Pediatric Ultrasound [1st ed. 2021] 3030568016, 9783030568016

This essential book is a unique, authoritative and clinically oriented text on pediatric ultrasound. It provides up-to-d

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Table of contents :
Preface
Acknowledgments
Contents
About the Contributors and Editors
Contributors
About the Editors
1: Ultrasound Imaging Techniques and Artifacts
Introduction
Acoustics
Wavelength and Frequency
Sound Propagation
Acoustic Impedance
Reflection
Refraction
Attenuation
Distance Measurement
Instrumentation
Transmitter
Transducer
Receiver
Image Display
Image Storage
Mechanical Transducer
Array Transducer
Transducer Selection
Harmonic Imaging
Spatial Compounding
Three-Dimensional Ultrasound
Doppler Ultrasound
Continuous Wave Doppler
Pulsed Wave Doppler
Color Doppler
Power Doppler
B-Flow
Elastography Imaging
Quasi-Static Strain Elastography
Dynamic Elastography
Ultrasound Contrast Imaging
Contrast Agents
Pulse Inversion Imaging
Ultrasound Artifacts
Grayscale Artifacts
Mirror Image: Multipath Reflection
Refraction
Reverberation, Comet-Tail, and Ring-Down Artifacts
Side Lobe Artifact
Enhancement and Shadowing Attenuation Artifacts
Partial Volume Artifact
Doppler Artifacts
Technically Related Doppler Artifacts
Inappropriate Doppler Settings
Aliasing (Wraparound)
Color Doppler Noise
Flow Directional Abnormalities
Anatomically Related Doppler Artifacts
Spectral Mirror Image Artifact
Tissue Vibration Artifact
Twinkling Artifact
Blooming Artifact
Three-Dimensional Ultrasound Artifacts
Ultrasound Contrast Agent Artifacts
Blooming Artifact
Systolic Peak Velocity Increase
High-Intensity Transient Signals
Ultrasound Safety
Thermal Bioeffects
Nonthermal Bioeffects
Regulations and Policies
References
2: Brain
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Cerebral Cortex
Basal Ganglia and Thalami
Ventricles
Cisterna Magna
Extra-Axial Fluid Spaces
Congenital Brain Anomalies
Dorsal Induction Disorders
Chiari Malformations
Anencephaly
Hydranencephaly
Ventral Induction Disorders
Holoprosencephaly
Septo-Optic (Pituitary) Dysplasia
Anomalies of the Corpus Callosum
Dandy–Walker Syndrome
Neuronal Proliferation Disorders
Hemimegalencephaly
Neuronal Migration Disorders
Lissencephaly
Gray Matter Heterotopia
Post-Migration Disorders
Polymicrogyria
Schizencephaly
Intracranial Hemorrhage
Preterm Infants
Periventricular Hemorrhagic Infarction
Cerebellar Hemorrhage
Term Infants
Epidural Hemorrhage
Subdural Hemorrhage
Subpial Hemorrhage
Parenchymal Hemorrhage
Choroid Plexus Hemorrhage
Hypoxic–Ischemic Injury
Global Hypoxic–Ischemic Injury
Preterm Infants
Term Infants
Focal Hypoxic–Ischemic Injury
Arterial Ischemic Stroke
Venous Sinus Thrombosis
Sickle Cell Disease
Infectious Brain Disorders
Viral Infections
Bacterial Infections
Fungal Infections
Neoplastic Brain and Ventricular Disorders
Neoplasms of the Brain
Neoplasms of the Ventricle
Vascular Brain Disorders
High-Flow Malformations
Low-Flow Malformations
Hydrocephalus
Benign External Hydrocephalus
Scalp Masses
Congenital Scalp Lesions
Dermoid/Epidermoid Cyst
Cephalocele
Lymph Node
Extracranial Birth Trauma
Vascular Scalp Lesions
Infantile Hemangioma
Sinus Pericranii
Suture Evaluation
Craniosynostosis
Positional Plagiocephaly
References
3: Spine
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Spinal Cord
Central Canal
Ventriculus Terminalis
Filar Cyst
Fatty Filum
Positional Nerve Root Clumping (“Pseudomass”)
Pseudosinus Tract
Dysmorphic Coccyx
Congenital Spinal Anomalies
Spinal Dysraphism
Open Defect
Meningocele
Myelocele and Myelomeningocele
Closed Defect
Simple Closed Defects
Complex Closed Defects
Lipomatous Tissue and Dural Defect (Lipomyelomeningocele, Lipomyelocele)
CSF-Containing Defects
Tethered Cord
Caudal Regression Syndrome
Spinal Lipoma
Segmental Spinal Dysgenesis
Infectious and Inflammatory Spinal Disorders
Epidural Abscess
Pilonidal Sinus and Cyst
Neoplastic Spinal Disorders
Intramedullary Tumors
Extramedullary Tumors
Sacrococcygeal Teratoma
Traumatic Spinal Disorders
Lumbar Puncture
Spinal Cord Injury
Spinal Cord Laceration and Transection
Epidural/Subdural Hematoma and Hematomyelia
Hydromyelia/Syringomyelia/Syrinx
References
4: Neck
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Neck
Anterior Triangle
Posterior Triangle
Lymph Nodes
Thyroid Gland
Parathyroid Glands
Salivary Glands
Parotid Glands
Submandibular Glands
Sublingual Glands
Neck
Congenital Neck Anomalies
Congenital Nonvascular Neck Masses
Congenital Benign Cystic Neck Masses
Thyroglossal Duct Cyst
Branchial Cleft Cyst
Cervical Thymic Cyst
Duplication Cyst
Teratoma and Dermoid Cyst
Congenital Benign Solid Neck Masses
Ectopic Thymus
Cervical Extension of Normal Thymus
Fibromatosis Colli
Congenital Vascular Neck Masses
Hemangiomas
Vascular Malformations
Arteriovenous Malformation
Arteriovenous Fistula
Venous Malformation
Lymphatic Malformation
Infectious and Inflammatory Neck Disorders
Cervical Lymphadenitis and Abscess
Mycobacterial Infection
Other Infectious and Inflammatory Disorders
Neoplastic Neck Disorders
Benign Neck Neoplasms
Myofibromatosis
Neurofibroma
Lipoma and Lipoblastoma
Malignant Neck Neoplasms
Lymphoma
Neuroblastoma
Rhabdomyosarcoma
Metastatic Disease
Thyroid Gland
Congenital Thyroid Gland Anomalies
Dysgenesis
Dyshormonogenesis
Focal Thyroid Gland Lesions
Cystic Focal Thyroid Gland Lesions
Colloid Cysts
Simple Cysts
Complex (Hemorrhagic) Cysts
Solid Focal Thyroid Gland Lesions
Benign Solid Focal Thyroid Gland Lesions
Follicular Adenoma
Hyperplastic or Adenomatoid Nodules
Malignant Solid Focal Thyroid Gland Lesions
Thyroid Cancer
Lymphoma
Diffuse Parenchymal Thyroid Gland Lesions
Multinodular Goiter (Nodular Hyperplasia)
Infectious Diffuse Parenchymal Thyroid Gland Disorders
Acute Suppurative (Bacterial) Thyroiditis
Subacute (De Quervain) Thyroiditis
Autoimmune-Mediated Diffuse Parenchymal Thyroid Gland Lesions
Graves’ Disease
Hashimoto Thyroiditis
Parathyroid Glands
Parathyroid Cyst
Parathyroid Hyperplasia
Parathyroid Adenoma
Salivary Glands
Congenital Salivary Gland Anomalies
First Branchial Cleft Cyst
Ranula
Infectious and Inflammatory Salivary Gland Disorders
Acute Infectious and Inflammatory Disorders
Viral (Nonsuppurative) Inflammation
Bacterial Parotitis and Abscess
Recurrent and Chronic Infectious and Inflammatory Disorders
Chronic Sialadenitis
Neoplastic Salivary Gland Disorders
Benign Salivary Gland Masses
Infantile Hemangioma
Lymphatic Malformation
Malignant Salivary Gland Neoplasms
Mucoepidermoid Carcinoma
Acinar Cell Carcinoma
Other Malignant Salivary Gland Neoplasms
Sialolithiasis
References
5: Lung
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Contrast-Enhanced Ultrasound
Normal Development and Anatomy
Normal Development
Normal Anatomy
Ultrasound Signs
The Pleural Line
Lung Sliding
A-Lines
B-Lines
M-Mode Appearance of the Normal Lung
Hepatization and Air Bronchograms
Congenital Lung Anomalies
Congenital Lobar Hyperinflation
Foregut Duplication Cyst
Congenital Pulmonary Airway Malformation
Bronchopulmonary Sequestration
Intralobar Bronchopulmonary Sequestration
Extralobar Bronchopulmonary Sequestration
Hybrid Congenital Lung Anomalies
Atelectasis and Consolidation
Pulmonary Necrosis
Pulmonary Abscess
Interstitial Lung Disease
Pulmonary Lymphangiectasia
Pulmonary Masses
Benign Pulmonary Masses
Malignant Pulmonary Neoplasms
Primary Malignant Pulmonary Neoplasms
Pleuropulmonary Blastoma
Rhabdomyosarcoma
Metastases
References
6: Pleura
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Normal Ultrasound Anatomy
A-Lines
B-Lines
T-Lines
Z-Lines
Pleural Effusion
Simple Pleural Effusion
Complex Pleural Effusion
Parapneumonic Effusion
Empyema
Fibrothorax
Traumatic Effusion
Hemorrhagic Effusion
Extrapleural Hematoma
Chylous Effusion
Pneumothorax
Absence of Lung Sliding
Stratosphere or Barcode Signs
Absence of B-Lines
Lung Point
Absence of Lung Pulse
Pleural Masses
Malignant Pleural Masses
Primary Neoplasms
Pleuropulmonary Blastoma
Rhabdomyosarcoma
Metastases
References
7: Mediastinum
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Compartment Approach
Thymus
Trachea
Esophagus
Mediastinal Masses
Prevascular (Anterior) Mediastinal Masses
Teratoma
Lymphoma
Lymphatic Malformation
Visceral (Middle) Mediastinal Masses
Foregut Duplication Cysts
Lymphadenopathy
Infectious Lymphadenopathy
Bacterial Lymphadenopathy
Mycobacterium Tuberculosis Lymphadenopathy
Fungal Lymphadenopathy
Fibrosing Mediastinitis
Neoplastic Lymphadenopathy
Paravertebral (Posterior) Mediastinal Masses
Neuroblastoma
Ganglioneuroblastoma
Ganglioneuroma
Cardiophrenic Angle Masses
Pericardial Cyst
Lymphadenopathy
References
8: Chest Wall
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Protocols
Annotations
Contrast-Enhanced Ultrasound
Normal Development and Anatomy
Normal Development
Thoracic Skeleton
Chest Wall Soft Tissues
Normal Anatomy
Thoracic Skeleton
Musculature
Ultrasound Appearance of Normal Chest Wall Anatomy
Congenital Chest Wall Anomalies
Vascular Tumors and Malformations
Hemangioma
Venous Malformation
Lymphatic Malformation
Osseous and Cartilaginous Lesions
Osteochondroma (Exostosis)
Asymmetric Cartilaginous Costochondral Junction
Enlarged Rib Ends
Infectious Disorders of the Chest Wall
Cellulitis
Abscess
Neoplastic Disorders of the Chest Wall
Benign Chest Wall Neoplasms
Lipoma
Mesenchymal Hamartoma
Malignant Chest Wall Neoplasms
Rhabdomyosarcoma
Ewing Sarcoma
Osteosarcoma
Lymphoma
Metastases
Traumatic Disorders of the Chest Wall
Hematoma
Rib Fracture
Foreign Bodies
References
9: Diaphragm
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Congenital Diaphragmatic Anomalies
Diaphragmatic Hernia
Bochdalek Hernia
Morgagni Hernia
Hiatal Hernia
Diaphragmatic Eventration
Acquired Diaphragmatic Disorders
Diaphragmatic Dysfunction
Diaphragmatic Inversion
Primary Diaphragmatic Masses
Benign Masses
Malignant Neoplasms
Traumatic Disorders
References
10: The Gastrointestinal Tract
Introduction
Esophagus
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Gastroesophageal Reflux
Hiatal Hernia
Stomach
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Congenital Anomalies
Gastric Atresia
Microgastria
Gastric Diaphragm (Antral Web)
Acquired Obstruction
Hypertrophic Pyloric Stenosis
Pylorospasm
Prostaglandin-Induced Foveolar Hyperplasia
Gastric Volvulus
Gastric Wall Thickening
Gastritis
Ménétrier Disease
Eosinophilic Gastroenteritis
Chronic Granulomatous Disease of the Stomach
Benign Masses of the Stomach
Gastric Duplication Cyst
Gastric Teratoma
Gastric Lipoma
Focal Foveolar Hyperplasia of the Stomach
Inflammatory Gastric Myofibroblastic Tumor
Gastric Bezoar
Other Benign Masses
Malignant Gastric Tumors
Lymphoma
GI Stromal Tumor
Other Malignant Masses
Small Bowel
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Congenital Anomalies
Duodenal Atresia, Stenosis, and Web
Intestinal Atresia
Jejunal and Ileal Stenosis
Midgut Malrotation
Meconium Ileus
Meconium Peritonitis and Pseudocyst
Acquired Obstruction
Intussusception
Small Bowel Intussusception
Ileocolic Intussusception
Small Bowel Wall Thickening
Infectious Enteritis
Crohn Disease
Hemorrhage
Trauma
Henoch–Schönlein Purpura
Eosinophilic Gastroenteritis
Lymphangiectasia
Cystic Fibrosis
Graft-Versus-Host Disease
Meckel Diverticulum
Benign Masses
Duplication Cyst
Mesenteric Cyst
Intestinal Polyp
Vascular Anomalies
Infantile Hemangioma
Blue Rubber Bleb Nevus Syndrome
Cutaneovisceral Angiomatosis with Thrombocytopenia
Malignant Masses
Hodgkin and Non-Hodgkin Lymphoma
Appendix
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Acute Appendicitis
Cystic Fibrosis of the Appendix
Benign Masses of the Appendix
Mucocele of the Appendix
Malignant Tumors of the Appendix
Carcinoid
Lymphoma of the Appendix
Colon
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Congenital Anomalies
Anorectal Malformations
Colonic Wall Thickening
Necrotizing Enterocolitis
Ulcerative Colitis
Crohn Disease
Infectious Colitis
Pseudomembranous Colitis
Neutropenic Colitis
Cystic Fibrosis
Hemolytic–Uremic Syndrome
Benign Masses
Juvenile Polyp
Duplication Cyst
Malignant Tumors
Lymphoma
Adenocarcinoma
References
11: Liver
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Grayscale Imaging
Doppler Ultrasound
Contrast-Enhanced Ultrasound
Elastography
Normal Development and Anatomy
Normal Development
Normal Anatomy
Segmental and Lobar Anatomy
Ligaments
Hepatic Circulation
Normal Hepatic Parenchyma
Anatomic Variants
Congenital Anomalies
Liver Cyst
Polycystic Liver Disease
Congenital Portosystemic Shunts
Diffuse Parenchymal Disease
Nonalcoholic Fatty Liver Disease
Fibrosis
Hemochromatosis
Cirrhosis
Infection
Viral Hepatitis
Bacterial Infection
Fungal Infection
Parasitic Infection
Trauma
Blunt Abdominal Trauma
Umbilical Vein Catheterization
Portal Hypertension
Budd–Chiari Syndrome
Sinusoidal Obstruction Syndrome
Peliosis Hepatis
Passive Venous Congestion
Portal Venous Gas
Tumors
Benign Masses
Congenital Hemangioma
Infantile Hemangioma
Mesenchymal Hamartoma
Focal Nodular Hyperplasia
Hepatic Adenoma
Malignant Tumors
Hepatoblastoma
Hepatocellular Carcinoma
Fibrolamellar Hepatocellular Carcinoma
Rare Primary Tumors
Metastases
Lymphoma
Posttransplant Lymphoproliferative Disorder
Leukemia
Liver Transplantation
Introduction
Surgical Technique
Whole Liver Transplantation
Living-Related Donor and Split Liver Grafts
Preoperative and Postoperative Imaging Considerations
Normal Liver Transplant Ultrasound
Rejection
Biliary Complications
Bile Leak
Biliary Stricture
Vascular Complications
Hepatic Artery Thrombosis
Hepatic Artery Stenosis
Hepatic Artery Pseudoaneurysm
Portal Vein Thrombosis
Portal Vein Stenosis
Hepatic Vein Outflow Obstruction
Inferior Vena Caval Stenosis and Thrombosis
Fluid Collections
Extrahepatic Collections
Intrahepatic Collections
References
12: Gallbladder and Biliary Tract
Gallbladder
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Congenital Anomalies
Agenesis/Hypoplasia
Ectopia
Septate Gallbladder
Duplication
Cholelithiasis
Sludge
Cholecystitis
Acute Calculous Cholecystitis
Acute Acalculous Cholecystitis
Biliary Dyskinesia
Chronic Cholecystitis
Porcelain Gallbladder
Hydrops
Torsion
Polyps
Adenomyomatosis
Cholesterol Polyps
Inflammatory Polyps
Other Polypoid Lesions
Other Disorders
Gallbladder Varices
Trauma
Biliary Tract
Technique
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Congenital Anomalies
Choledochal Cysts
Caroli Disease
Biliary Tract Obstruction
Biliary Atresia
Neonatal Hepatitis Syndrome
Alagille Syndrome
Byler Disease
Choledocholithiasis
Inspissated Bile Syndrome
Sclerosing Cholangitis
Mirizzi Syndrome
Bile Duct Stricture
AIDS Cholangiopathy
Spontaneous Perforation of the Extrahepatic Bile Ducts
Biliary Tract Trauma
Tumors
Benign Masses
Granular Cell Tumor
Bile Duct Adenoma
Malignant Bile Duct Tumors
Rhabdomyosarcoma of the Bile Duct
Cholangiocarcinoma
Neuroendocrine Tumor
Metastases
References
13: Spleen and Peritoneal Cavity
Spleen
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Lobulations and Clefts
Accessory Spleen
Congenital Anomalies
Wandering Spleen
Polysplenia, Hyposplenia, and Asplenia
Nonparasitic Splenic Cysts
Splenogonadal Fusion
Splenopancreatic Fusion
Infection
Pyogenic Abscess
Fungal Abscess
Tuberculous Infection
Epstein-Barr Viral Infection
Parasitic Infection
Acquired Immunodeficiency Syndrome
Inflammatory Disorders
Sarcoidosis
Rheumatic Disorders
Granulomatosis with Polyangiitis
Hemoglobinopathies
Lysosomal Storage Diseases
Portal Hypertension
Trauma
Splenosis
Vascular Anomalies
Lymphatic Malformation
Venous Malformation
Kaposiform Lymphangiomatosis
Peliosis
Benign Masses
Hamartoma
Extramedullary Hematopoiesis
Inflammatory Myofibroblastic Tumor
Hemangioma
Littoral Cell Angioma
Malignant Tumors
Lymphoma
Leukemia
Angiosarcoma
Kaposiform Hemangioendothelioma
Metastatic Disease
Neuroblastoma
Langerhans Cell Histiocytosis
Complications of Pancreatitis
Gamna-Gandy Bodies
Peritoneal Cavity
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Omentum
Mesentery
Peritoneal Fluid
Normal Flow of Peritoneal Fluid
Ascites
Hemoperitoneum
Chylous Ascites
Urine Ascites
Localized Peritoneal Fluid Collections
Cerebrospinal Fluid Pseudocyst
Biloma
Pancreatic Pseudocyst
Peritoneal Inclusion Cyst
Diaphragmatic Mesothelial Cyst
Peritoneal Inflammation
Infective Peritonitis
Tuberculous Peritonitis
Chemical Peritonitis
Granulomatous Peritonitis
Sclerosing Encapsulating Peritonitis
Abscess
Pneumoperitoneum
Omental Cyst
Segmental Omental Infarction
Mesenteric Lymphadenitis
Vascular Malformations
Lymphatic Malformation
Venous Malformation
Benign Masses
Infantile Hemangioma
Lipoma
Lipomatosis
Lipoblastoma/Lipoblastomatosis
Neurofibroma
Plexiform Neurofibroma
Desmoid Tumor
Castleman Disease
Inflammatory Myofibroblastic Tumor
Malignant Tumors
Primary Tumors
Lymphoma
Rhabdomyosarcoma
Desmoplastic Small Round Cell Tumor
Malignant Mesothelioma
Metastatic Disease
Neuroblastoma
Adenocarcinoma
Wilms’ Tumor
Germ Cell Tumor
Intracranial Neoplasms
References
14: Pancreas, Adrenal Glands, and Retroperitoneum
Introduction
Pancreas
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Lobulated Parenchymal Contour
Congenital Anomalies
Pancreas Divisum
Annular Pancreas
Common Pancreaticobiliary Channel
Partial Pancreatic Agenesis
Accessory Pancreatic Lobe
Ectopic Pancreas
Congenital Hyperinsulinism
Congenital Pancreatic Cyst
Genetic Disorders with Associated Pancreatic Abnormalities
Cystic Fibrosis
Shwachman-Diamond Syndrome
Beckwith-Wiedemann Syndrome
Autosomal Dominant Polycystic Kidney Disease
Von Hippel-Lindau Disease
Acute Pancreatitis
Acute Peripancreatic Fluid Collections
Pseudocysts
Pancreaticopleural Fistula
Necrotizing Pancreatitis
Vascular Complications
Acute Recurrent and Chronic Pancreatitis
Trauma
Pancreatic Venous and Lymphatic Malformations
Benign Pancreatic Neoplasms
Serous Cystadenoma
Mucinous Cystadenoma
Infantile Hemangioma
Cystic Teratoma
Lipoma
Inflammatory Myofibroblastic Tumor
Leiomyoma, Neurofibroma, and Schwannoma
Malignant Pancreatic Tumors
Pancreatoblastoma
Solid Pseudopapillary Tumor
Islet Cell Tumor
Acinar Cell Carcinoma
Ductal Adenocarcinoma
Lymphoma
Neuroblastoma
Primitive Neuroectodermal Tumor
Kaposiform Hemangioendothelioma
Rhabdomyosarcoma
Fibrosarcoma
Metastatic Disease
Pancreatic Transplantation
Adrenal Glands
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Discoid Adrenal Gland
Congenital Anomalies
Congenital Adrenal Agenesis
Fusion Abnormalities
Circumrenal Adrenal Gland
Horseshoe Adrenal Gland
Adrenal Rests
Adrenal Heterotopia
Genetic Disorders
Congenital Adrenal Hyperplasia
Congenital Lipoid Adrenal Hyperplasia
Wolman Disease
Adrenal Cyst
Idiopathic Adrenal Cyst
Infection
Congenital Herpes Simplex Infection
Granulomatous Infection
Xanthogranulomatous Adrenalitis
Abscess
Adrenal Hemorrhage
Adrenocortical Tumors
Adrenocortical Adenoma and Carcinoma
Neural Crest Tumors
Ganglioneuroma
Ganglioneuroblastoma
Neuroblastoma
Pheochromocytoma
Myelolipoma
Hemangioma
Teratoma
Leiomyoma
Lymphoma
Metastases
Nonvascular Disorders of the Retroperitoneum
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Infection and Abscess
Hemorrhage
Fibrosis
Extramedullary Hematopoiesis
Venous and Lymphatic Malformations
Lymphadenopathy
Infection
Lymphoma
Metastatic Disease
Benign Masses
Hemangioma
Mature Teratoma
Retroperitoneal Lipoma and Lipoblastoma
Neurofibroma and Schwannoma
Neural Crest Tumors: Ganglioneuroma, Ganglioneuroblastoma, and Neuroblastoma
Malignant Tumors
Rhabdomyosarcoma
Infantile Fibrosarcoma
Malignant Germ Cell Tumor/Immature Teratoma
Smooth Muscle Tumors
Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma)
Ewing Sarcoma
Inflammatory Myofibroblastic Tumor
Kaposiform Hemangioendothelioma
References
15: Male Genital Tract
Introduction
Scrotum
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Scrotum
Testes
Epididymis
Spermatic Cord
Testicular Appendages
Blood Supply
Anatomical Variants
Testicular Appendages
Vessels
Congenital Anomalies
Testicular Agenesis
Cryptorchidism
Anorchidism
Testicular Regression Syndrome
Testicular Hypoplasia
Polyorchidism
Testicular Ectopia
Cystic Dysplasia of the Rete Testis
Splenogonadal Fusion
Bell Clapper Deformity
Acute Scrotal Pain
Testicular Torsion
Segmental Testicular Infarction
Arterial Segmental Testicular Infarction
Venous Testicular Infarction
Torsion of Testicular Appendages
Inflammatory Disorders
Acute Epididymitis and Epididymo-orchitis
Isolated Orchitis
Testicular Abscess
Epididymal Abscess
Scrotal Abscess
Henoch-Schönlein Purpura
Idiopathic Scrotal Edema
Fournier Gangrene
Chronic Epididymitis
Dancing Megasperm
Scrotal and Spermatic Cord Fluid Collections
Scrotal Hydrocele
Spermatic Cord Hydrocele
Abdominoscrotal Hydrocele
Scrotal Hematocele
Scrotal Lymphocele
Scrotal Calcification
Testicular Microlithiasis
Loose Bodies
Meconium Peritonitis
Trauma
Blunt Scrotal Trauma
Testicular Hematoma
Testicular Fracture
Testicular Rupture
Scrotal Hematocele
Penetrating Scrotal Trauma
Foreign Body
Scrotal Urinoma
Repetitive Scrotal Microtrauma
Mountain Biking
Equestrian-Related Injuries
Inguinal Hernia
Indirect Inguinal Hernia
Direct Inguinal Hernia
Varicocele
Intratesticular Varicocele
Testicular Masses
Non-Neoplastic Lesions
Adrenal Rests
Leydig Cell Hyperplasia
Hamartoma
Simple Cyst
Sinus Histiocytosis (Rosai-Dorfman-Destombes Disease)
Primary Testicular Tumors
Germ Cell Tumors
Yolk Sac Tumor
Teratoma
Seminoma
Gonadoblastoma
Embryonal Carcinoma
Teratocarcinoma
Choriocarcinoma
Stromal Tumors
Leydig Cell Tumor
Sertoli Cell Tumor
Granulosa Cell Tumor
Other Testicular Tumors
Epidermoid Cyst
Dermoid Cyst
Fibroma
Neurofibroma
Lipoma
Hemangioma
Leiomyoma
Adenomatoid Tumor
Follicular Lymphoma
Secondary Testicular Tumors
Leukemia and Lymphoma
Neuroblastoma
Wilms’ Tumor
Langerhans Cell Histiocytosis
Carcinoid Tumor
Rhabdomyosarcoma
Retinoblastoma
Paratesticular Masses
Non-Neoplastic Lesions
Spermatocele
Epididymal Cyst
Fibrous Pseudotumor
Fibrous Hamartoma of Infancy
Juvenile Xanthogranuloma
Spermatic Granuloma
Cystic Dysplasia of Epididymis
Ectopic Adrenal Rest
Vascular Anomalies
Lymphatic Malformation
Venous Malformation
Arteriovenous Malformation
Benign Tumors
Lipoma
Adenomatoid Tumor
Leiomyoma
Dermoid
Neurofibroma
Papillary Cystadenoma
Malignant Tumors
Primary Tumors
Rhabdomyosarcoma
Inflammatory Myofibroblastic Tumor
Liposarcoma
Secondary Tumors
Wilms’ Tumor
Neuroblastoma
Leukemia
Lymphoma
Leiomyosarcoma
Fibrosarcoma
Prostate and Seminal Vesicles
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Prostate Gland
Seminal Vesicles
Congenital Anomalies
Enlarged Prostatic Utricle and Prostatic Utricle Cyst
Müllerian Duct Cyst
Seminal Vesicle Cyst
Seminal Vesicle Agenesis or Hypoplasia
Inflammatory Disorders
Prostatitis
Prostatic Abscess
Seminal Vesiculitis
Tumors of the Prostate and Seminal Vesicle
Rhabdomyosarcoma
Leukemia
Seminal Vesicle Tumors
References
16: Female Genital Tract
Introduction
Technique: Patient Positioning, Transducer Selection, and Imaging Approaches
Transabdominal Ultrasound
Transvaginal Ultrasound
Three-Dimensional Ultrasound
Transperineal Ultrasound
Normal Development and Anatomy
Normal Development
Gonads and Reproductive Tract
External Genitalia
Normal Anatomy
Ovary and Fallopian Tube
Uterus and Cervix
Vagina
Ovarian and Uterine Changes Associated with the Menstrual Cycle
Anatomic Variants
Arcuate Uterus
Congenital Anomalies
Müllerian Duct Anomalies
Müllerian Agenesis
Uterine Agenesis
Mayer-Rokitansky-Küster-Hauser Syndrome (MRKH)
Disorders of Lateral Fusion
Septate Uterus
Bicornuate Uterus
Uterus Didelphys
Unicornuate Uterus
Disorders of Vertical Fusion
Imperforate Hymen
Transverse Vaginal Septum
Atresia of Cervix or Vagina
OHVIRA Syndrome
Disorders of Sex Development
Sex Chromosome Disorders of Sex Development
45,X (Turner Syndrome)
46,XX Disorders of Sex Development
Congenital Adrenal Hyperplasia
Cloacal Malformation
Adnexal Masses
Ovarian Masses
Functional Cyst
Endometrioma
Germ Cell Tumors
Teratoma
Gonadoblastoma
Dysgerminoma
Yolk Sac Tumor
Choriocarcinoma
Mixed Germ Cell Tumor
Epithelial Tumors
Cystadenoma
Borderline Epithelial Tumor and Cystadenocarcinoma
Stromal Tumors
Thecoma-Fibroma
Juvenile Granulosa Cell Tumor
Sertoli-Leydig Cell Tumor
Secondary Tumors
Paraovarian Cyst
Peritoneal Inclusion Cyst
Adnexal Torsion
Isolated Tubal Torsion
Massive Edema of the Ovary
Ectopic Pregnancy
Pelvic Inflammatory Disease
Uterine Masses
Benign Masses
Leiomyoma (Fibroid)
Adenomyosis
Malignant Tumors
Lymphoma
Cervical Masses
Benign Tumors
Nabothian Cyst
Malignant Tumors
Rhabdomyosarcoma
Vaginal Masses
Benign Masses
Gartner Duct Cyst
Bartholin Cyst
Inclusion Cyst
Paraurethral Duct Cyst
Fibroepithelial Polyp
Müllerian Papilloma
Malignant Tumors
Rhabdomyosarcoma
Clear-Cell Adenocarcinoma and Endodermal Sinus Tumor
Vaginal Foreign Body
Pubertal Disorders
Precocious Puberty
Amenorrhea
Polycystic Ovary Syndrome
Canal of Nuck Disorders
Hydrocele of the Canal of Nuck
Hernia of the Canal of Nuck
References
17: Urinary Tract
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Grayscale Imaging
Doppler Ultrasound
Contrast-Enhanced Ultrasound
Elastography
Normal Development and Anatomy
Normal Development
Normal Anatomy
Kidney
Infant
Older Child and Adolescent
Anatomic Variants
Fetal Lobulation
Junctional Parenchymal Defect
Dromedary Hump
Hypertrophied Column of Bertin
Compensatory Hypertrophy
Compound Calyx
Accessory Renal Artery
Retroaortic Left Renal Vein
Circumaortic Left Renal Vein
Ureter
Normal Anatomy
Ureteral Jets
Bladder
Normal Anatomy
Anatomic Variants
Bladder Ears
Urethra
Normal Anatomy
Male Urethra
Female Urethra
Congenital Anomalies
Anomalies of Renal Number, Position, Fusion, and Growth
Renal Agenesis
Renal Duplication
Supernumerary Kidney
Renal Ectopia
Simple Ectopia
Crossed Renal Ectopia
Horseshoe Kidney
Pancake Kidney
Renal Hypoplasia
Anomalies of the Renal Collecting System and Ureter
Classification of Prenatal and Postnatal Hydronephrosis
Ureteropelvic Junction Obstruction
Ureteropelvic Junction Obstruction Caused by Crossing Vessel
Congenital Megacalyces
Congenital Infundibulopelvic Stenosis
Calyceal Diverticulum
Congenital Ureterovesical Junction Obstruction
Ectopic Ureter
Ectopic Ureterocele
Retrocaval Ureter
Vesicoureteral Reflux
Contrast-Enhanced Ultrasound Diagnosis of Vesicoureteral Reflux
Imaging of Endoscopically Placed Bulking Agents
Anomalies of the Bladder
Urachal Anomalies
Patent Urachus
Vesicourachal Diverticulum
Umbilicourachal Sinus
Urachal Cyst
Bladder Diverticula
Bladder Exstrophy
Cloacal Exstrophy
Cloacal Malformation
Bladder Duplication
Bladder Agenesis
Prune-Belly Syndrome
Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome
Anomalies of the Urethra
Posterior Urethral Valves
Anterior Urethral Valves
Urethral Duplication
Acquired Ureteral Obstruction
Intraluminal Obstruction
Extrinsic Compression
Neurogenic Bladder
Urinary Tract Infection
Acute Pyelonephritis
Renal Abscess
Pyonephrosis
Fungal Infection
Parasitic Infection
Opportunistic Infection
Chronic Pyelonephritis
Xanthogranulomatous Pyelonephritis
Cystitis
Renal Cystic Disease
Autosomal Recessive Polycystic Kidney Disease
Autosomal Dominant Polycystic Kidney Disease
Cystic Renal Dysplasia
Nephronophthisis
Medullary Cystic Disease
Glomerulocystic Kidney Disease
Syndromes with Renal Cysts
Tuberous Sclerosis
Von Hippel-Lindau Disease
Acquired Cystic Kidney Disease
Renal Vascular Disease
Renal Artery Stenosis
Renal Artery Thrombosis
Renal Artery Pseudoaneurysm
Renal Vein Thrombosis
Arteriovenous Fistula
Medical Renal Disease
Acute Kidney Injury
Chronic Kidney Disease
Renal Transplantation
Surgical Technique
Normal Posttransplant Imaging
Complications
Vascular Complications
Renal Artery Thrombosis
Renal Artery Stenosis
Renal Vein Thrombosis
Arteriovenous Fistula
Pseudoaneurysm
Parenchymal Complications
Acute Tubular Necrosis
Rejection
Drug Toxicity
Urologic Complications
Transplant Urine Leak
Transplant Ureteral Obstruction
Transplant Vesicoureteral Reflux
Transplant Pyelonephritis
Perinephric Fluid Collections
Transplant Lymphocele
Transplant Urinoma
Transplant Hematoma and Seroma
Transplant Abscess
Posttransplant Tumors
Urinary Tract Calcification
Renal Cortical Calcification
Medullary Nephrocalcinosis
Renal Vein Thrombosis Calcifications
Dystrophic Calcification
Urinary Stasis
Urolithiasis
Risk Factors
Kidney Stone Risk Factors
Bladder Stone Risk Factors
Trauma
Renal Trauma
Contrast-Enhanced Ultrasound Diagnosis of Trauma
Bladder Trauma
Tumors and Malformations
Renal Tumors
Benign Renal Tumors
Mesoblastic Nephroma
Angiomyolipoma
Multilocular Cystic Renal Tumor
Metanephric Adenoma
Inflammatory Myofibroblastic Tumor
Ossifying Renal Tumor of Infancy
Primary Malignant Renal Tumors
Wilms’ Tumor
Nephrogenic Rests and Nephroblastomatosis
Renal Cell Carcinoma
Rhabdoid Tumor
Clear Cell Sarcoma
Renal Medullary Carcinoma
Primitive Neuroectodermal Tumor
Other Rare Primary Malignant Renal Tumors
Secondary Malignant Renal Tumors
Leukemia
Lymphoma
Metastases
Osteosarcoma
Neuroblastoma
Primary Ureteral Tumors
Fibroepithelial Polyp
Urothelial Tumor
Secondary Ureteral Tumors
Extension of Wilms’ Tumor
Bladder Malformations and Tumors
Vascular Malformations
Lymphatic Malformation
Venous Malformation
Benign Bladder Tumors
Urothelial Papilloma
Papillary Urothelial Neoplasm of Low Malignant Potential
Fibroepithelial Polyp
Inflammatory Myofibroblastic Tumor
Leiomyoma
Neurofibroma
Paraganglioma
Nephrogenic Adenoma
Malignant Bladder Tumors
Rhabdomyosarcoma
Transitional Cell Carcinoma
Leiomyosarcoma
Angiosarcoma
Urethral Tumors
Urethral Polyp
Urinary Diversion
References
18: Musculoskeletal System
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development
Soft Tissues
Normal Anatomy and Imaging Approaches
Skin and Subcutaneous Tissues
Muscles
Tendons
Infectious/Inflammatory Disorders
Cellulitis
Pyomyositis
Soft Tissue Abscess
Trauma
Fat Necrosis
Foreign Bodies
Muscle Tears and Intramuscular Hematomas
Myositis Ossificans
Muscle Hernia
Tendinopathy and Tendon Tears
Tumors
Subcutaneous Granuloma Annulare
Pilomatricoma
Lipoma
Lipoblastoma
Bones/Cartilage
Normal Anatomy and Imaging Approaches
Congenital/Developmental Abnormalities
Congenital Rib Anomalies
Infectious/Inflammatory Disorders
Osteomyelitis
Trauma
Epiphyseal Separation
Classic Metaphyseal Lesion
Tumors
Osteochondroma
Joints
Infectious/Inflammatory Disorders
Septic Arthritis
Juvenile Idiopathic Arthritis
Hemarthrosis
Shoulder
Normal Anatomy and Imaging Approaches
Normal Anatomy
Patient Positioning
Imaging Approaches
Congenital/Developmental Abnormalities
Glenohumeral Dysplasia
Elbow
Normal Anatomy and Imaging Approaches
Normal Anatomy
Patient Positioning
Imaging Approaches
Anterior Approach
Posterior Approach
Medial Approach
Lateral Approach
Annular Ligament
Elbow Fat Pads and Joint Effusion
Congenital/Developmental Abnormalities
Congenital Radial Head Dislocation
Trauma
Distal Humeral Epiphyseal Separation
Apophyseal Avulsion
Pulled Elbow
Wrist and Hand
Normal Anatomy and Imaging Approaches
Normal Anatomy
Patient Positioning
Imaging Approaches
Ganglia
Congenital/Developmental Abnormalities
Carpal Boss
Tumors
Giant Cell Tumor of the Tendon Sheath
Hip
Normal Anatomy and Imaging Approaches
Normal Anatomy
Patient Positioning
Imaging Approaches
Neonates and Infants for Hip Dysplasia
Assessment for Synovitis and Effusion
Congenital/Developmental Abnormalities
Developmental Dysplasia of the Hip
Imaging
Treatment
Proximal Focal Femoral Deficiency
Infectious/Inflammatory Disorders
Transient Synovitis and Septic Arthritis
Trauma
Slipped Capital Femoral Epiphysis
Knee
Normal Anatomy and Imaging Approaches
Normal Anatomy
Patient Positioning
Imaging Approaches
Patellofemoral Joint
Extensor Mechanism
Tibial Tubercle
Menisci
Joint Effusion and Baker Cyst
Joint Effusion
Baker Cyst
Congenital/Developmental Abnormalities
Tibial Hemimelia
Congenital Knee Dislocation
Congenital Patellar Dislocation
Bipartite/Multipartite Patella
Discoid Meniscus and Meniscal Tears
Trauma
Osgood-Schlatter Disease
Sinding-Larsen-Johansson Syndrome
Ankle and Hindfoot
Normal Anatomy and Imaging Approaches
Normal Anatomy
Patient Positioning
Imaging Approaches
Joint Effusion
Calcaneal Apophysis
Trauma
Apophyseal Avulsion Injuries
Vascular Anomalies
Vascular Tumors
Infantile Hemangioma
Congenital Hemangioma
Kaposiform Hemangioendothelioma
Vascular Malformations
Venous Malformation
Lymphatic Malformation
Arteriovenous Malformation and Arteriovenous Fistula
References
19: Vascular Imaging
Introduction
Neck Vessels
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Carotid Artery
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Thrombosis and Stenosis
Aneurysm
Dissection
Internal Jugular Vein
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Congenital Anomalies
Jugular Vein Phlebectasia
Thrombosis
Stenosis
Aneurysm
Extremity Arteries
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Upper Extremity
Normal Development
Normal Anatomy
Lower Extremity
Normal Development
Normal Anatomy
Anatomic Variants
Stenosis and Thrombosis
Aneurysm
Pseudoaneurysm
Arteriovenous Fistula
Extremity Veins
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Upper Extremity
Normal Development
Normal Anatomy
Lower Extremity
Normal Development
Normal Anatomy
Anatomic Variants
Thrombosis
Acute Deep Vein Thrombosis
Chronic (Residual) Deep Vein Thrombosis
Retroperitoneal Vessels
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Aorta
Normal Development and Anatomy
Normal Development
Normal Anatomy
Thrombosis
Stenosis
Aneurysm
Dissection
Inferior Vena Cava
Normal Development and Anatomy
Normal Development
Normal Anatomy
Congenital Anomalies
Interruption of the IVC with Azygos Continuation
Retrocaval Ureter
Duplicated IVC
Left-Sided IVC
Thrombosis
May-Thurner Syndrome
References
20: Breast
Introduction
Technique
Patient Positioning
Ultrasound Transducer Selection
Imaging Approaches
Normal Development and Anatomy
Normal Development
Normal Anatomy
Anatomic Variants
Accessory Breast Tissue
Congenital Anomalies
Poland Syndrome
Polythelia/Polymastia
Amastia/Athelia/Amazia
Developmental Anomalies
Premature Thelarche
Juvenile (Virginal) Hypertrophy
Gynecomastia
Inflammatory Lesions
Mastitis and Abscess
Non-neoplastic Lesions
Mammary Duct Ectasia
Retroareolar Cysts (Obstructed Glands of Montgomery)
Fibrocystic Disease
Galactocele
Hematoma
Fat Necrosis
Intramammary Lymph Node
Vascular Malformations
Venous Malformation
Lymphatic Malformation
Neoplasms
Benign Tumors
Fibroadenoma
Hemangioma
Intraductal Papilloma
Juvenile Papillomatosis
Pseudoangiomatous Stromal Hyperplasia
Lactating Adenoma
Desmoid Tumor
Granular Cell Tumor
Malignant Tumors
Cystosarcoma Phyllodes
Carcinoma
Angiosarcoma
Hematologic Malignancies
Metastases
References
Index
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Harriet J. Paltiel Edward Y. Lee Editors

Pediatric Ultrasound

123

Pediatric Ultrasound

Harriet J. Paltiel  •  Edward Y. Lee Editors

Pediatric Ultrasound

Editors Harriet J. Paltiel Division of Ultrasound Department of Radiology, Boston Children’s Hospital and Harvard Medical School Boston, MA USA

Edward Y. Lee Division of Thoracic Imaging Department of Radiology, Boston Children’s Hospital and Harvard Medical School Boston, MA USA

ISBN 978-3-030-56801-6    ISBN 978-3-030-56802-3 (eBook) https://doi.org/10.1007/978-3-030-56802-3 © Springer Nature Switzerland AG 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To Eric and Emil, to the memory of Sarah and Daniel, and to all the children whose images grace these pages. To my coeditor, Edward Y. Lee, MD, MPH, for sharing his vast knowledge and experience in pediatric imaging. – Harriet J. Paltiel, MDCM To my parents, Kwan-Pyo and Kang-Ja, and my family for their constant support and encouragement. To the trainees and radiologists that I have met during my academic career for sharing their enthusiasm for learning. To my coeditor, Harriet J. Paltiel, MDCM, for sharing her expertise and passion for pediatric ultrasound. – Edward Y. Lee, MD, MPH

Preface

Ultrasound imaging plays an essential role in the diagnosis and management of pediatric disorders. Its ease of use, flexibility, lack of ionizing radiation, and relatively low cost compared to CT and MRI all enhance its attractiveness as a first-line imaging modality in patient evaluation. Recent technological advances, including contrast-enhanced ultrasound and elastography, continue to expand its diagnostic capabilities. This book is intended to provide a comprehensive review of current knowledge in the field of pediatric ultrasound and to serve as a reference for practicing physicians, residents and fellows, medical students, sonographers, and all others with an interest in the wide applicability of this important imaging tool in infants and children. An introductory chapter on the physics of ultrasound imaging techniques and artifacts is followed by chapters devoted to ultrasound of the brain, spine, and neck; chest, abdomen, and pelvis; musculoskeletal and vascular systems; and breast. The recent approval of ultrasound contrast agents for imaging of focal liver lesions and for voiding cystography in the United States has opened the door to the development and implementation of new applications of contrast-enhanced ultrasound of which many examples are featured throughout the book.  Applications of elastography to pediatric liver diseases are also described. The rapid development and increased use of ultrasound in the diagnosis and management in children with musculoskeletal and vascular disorders has prompted the inclusion of chapters entirely devoted to these topics. Both American and international authors have been selected for their expertise and to reflect the global perspective and intended audience for this book. A systematic approach to each organ system is provided, including an overview of ultrasound imaging techniques, normal development, and anatomy. This is followed by a discussion of normal variants, congenital anomalies, infectious and inflammatory disorders, traumatic lesions, and benign and malignant tumors. A brief review of the etiology and pathophysiology of each disorder precedes a description and illustration of the ultrasound imaging findings, relevant correlative imaging, and current treatment approach. Every chapter includes pertinent anatomical drawings, diagrams, and tables. Up-to-date references for each topic are provided. A selection of cine clips is also included in the online version of the book which is available in a fully searchable format. We hope that this work, with its accessible style and outstanding images, will be valuable to all readers in their daily practice and deepen their appreciation of the wide utility and applicability of ultrasound in pediatric medicine. Boston, MA, USA 

Harriet J. Paltiel Edward Y. Lee

vii

Acknowledgments

We are deeply grateful to the many colleagues whose efforts have contributed to this work. We thank all of the authors for their outstanding contributions. Much appreciation goes to Stephanie Frost, Development Editor, for her meticulous attention to detail in bringing this project to fruition and to Margaret Moore, Publishing Editor, Springer Nature, for providing the resources to accomplish this monumental task, and for her unwavering support and encouragement through the entire gestation of the book.

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Contents

1 Ultrasound Imaging Techniques and Artifacts���������������������������������������������������������   1 Don-Soo Kim, Harriet J. Paltiel, Phillip Jason White, and Elisabetta Sassaroli Introduction�����������������������������������������������������������������������������������������������������������������    1 Acoustics���������������������������������������������������������������������������������������������������������������������    2 Wavelength and Frequency�������������������������������������������������������������������������������������    2 Sound Propagation �������������������������������������������������������������������������������������������������    2 Acoustic Impedance�����������������������������������������������������������������������������������������������    4 Reflection ���������������������������������������������������������������������������������������������������������������    4 Refraction���������������������������������������������������������������������������������������������������������������    7 Attenuation�������������������������������������������������������������������������������������������������������������    7 Distance Measurement�������������������������������������������������������������������������������������������    8 Instrumentation�����������������������������������������������������������������������������������������������������������   11 Transmitter �������������������������������������������������������������������������������������������������������������   11 Transducer���������������������������������������������������������������������������������������������������������������   12 Receiver �����������������������������������������������������������������������������������������������������������������   12 Image Display���������������������������������������������������������������������������������������������������������   14 Image Storage���������������������������������������������������������������������������������������������������������   14 Mechanical Transducer�������������������������������������������������������������������������������������������   14 Array Transducer ���������������������������������������������������������������������������������������������������   19 Transducer Selection�����������������������������������������������������������������������������������������������   22 Harmonic Imaging �����������������������������������������������������������������������������������������������������   23 Spatial Compounding�������������������������������������������������������������������������������������������������   24 Three-Dimensional Ultrasound�����������������������������������������������������������������������������������   25 Doppler Ultrasound�����������������������������������������������������������������������������������������������������   26 Continuous Wave Doppler �������������������������������������������������������������������������������������   29 Pulsed Wave Doppler ���������������������������������������������������������������������������������������������   29 Color Doppler���������������������������������������������������������������������������������������������������������   31 Power Doppler �������������������������������������������������������������������������������������������������������   31 B-Flow �����������������������������������������������������������������������������������������������������������������������   32 Elastography Imaging�������������������������������������������������������������������������������������������������   32 Quasi-Static Strain Elastography ���������������������������������������������������������������������������   32 Dynamic Elastography�������������������������������������������������������������������������������������������   34 Ultrasound Contrast Imaging�������������������������������������������������������������������������������������   35 Contrast Agents�������������������������������������������������������������������������������������������������������   35 Pulse Inversion Imaging�����������������������������������������������������������������������������������������   36 Ultrasound Artifacts ���������������������������������������������������������������������������������������������������   37 Grayscale Artifacts�������������������������������������������������������������������������������������������������   37 Mirror Image: Multipath Reflection�������������������������������������������������������������������   37 Refraction�����������������������������������������������������������������������������������������������������������   37 Reverberation, Comet-Tail, and Ring-Down Artifacts���������������������������������������   38 Side Lobe Artifact�����������������������������������������������������������������������������������������������   39

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Enhancement and Shadowing Attenuation Artifacts�������������������������������������������   39 Partial Volume Artifact���������������������������������������������������������������������������������������   40 Doppler Artifacts�����������������������������������������������������������������������������������������������������   41 Technically Related Doppler Artifacts���������������������������������������������������������������   42 Inappropriate Doppler Settings�����������������������������������������������������������������������   42 Aliasing (Wraparound)�����������������������������������������������������������������������������������   43 Color Doppler Noise���������������������������������������������������������������������������������������   43 Flow Directional Abnormalities���������������������������������������������������������������������   44 Anatomically Related Doppler Artifacts�������������������������������������������������������������   44 Spectral Mirror Image Artifact�����������������������������������������������������������������������   44 Tissue Vibration Artifact���������������������������������������������������������������������������������   45 Twinkling Artifact�������������������������������������������������������������������������������������������   45 Blooming Artifact�������������������������������������������������������������������������������������������   46 Three-Dimensional Ultrasound Artifacts���������������������������������������������������������������   47 Ultrasound Contrast Agent Artifacts�����������������������������������������������������������������������   47 Blooming Artifact�����������������������������������������������������������������������������������������������   47 Systolic Peak Velocity Increase �������������������������������������������������������������������������   47 High-Intensity Transient Signals������������������������������������������������������������������������   47 Ultrasound Safety�������������������������������������������������������������������������������������������������������   47 Thermal Bioeffects�������������������������������������������������������������������������������������������������   47 Nonthermal Bioeffects �������������������������������������������������������������������������������������������   48 Regulations and Policies�����������������������������������������������������������������������������������������   48 References�������������������������������������������������������������������������������������������������������������������   49 2 Brain�����������������������������������������������������������������������������������������������������������������������������  51 Helen H. R. Kim, Wendy G. Kim, Edward Y. Lee, and Grace S. Phillips Introduction�����������������������������������������������������������������������������������������������������������������   51 Technique�������������������������������������������������������������������������������������������������������������������   52 Patient Positioning �������������������������������������������������������������������������������������������������   52 Ultrasound Transducer Selection ���������������������������������������������������������������������������   52 Imaging Approaches�����������������������������������������������������������������������������������������������   52 Normal Development and Anatomy���������������������������������������������������������������������������   57 Normal Development���������������������������������������������������������������������������������������������   57 Normal Anatomy�����������������������������������������������������������������������������������������������������   57 Cerebral Cortex�������������������������������������������������������������������������������������������������������   58 Basal Ganglia and Thalami�������������������������������������������������������������������������������������   58 Ventricles�����������������������������������������������������������������������������������������������������������������   59 Cisterna Magna�������������������������������������������������������������������������������������������������������   60 Extra-Axial Fluid Spaces ���������������������������������������������������������������������������������������   61 Congenital Brain Anomalies���������������������������������������������������������������������������������������   61 Dorsal Induction Disorders�������������������������������������������������������������������������������������   61 Chiari Malformations�����������������������������������������������������������������������������������������   61 Anencephaly�������������������������������������������������������������������������������������������������������   63 Hydranencephaly �����������������������������������������������������������������������������������������������   63 Ventral Induction Disorders �����������������������������������������������������������������������������������   63 Holoprosencephaly���������������������������������������������������������������������������������������������   63 Septo-Optic (Pituitary) Dysplasia�����������������������������������������������������������������������   64 Anomalies of the Corpus Callosum �������������������������������������������������������������������   65 Dandy–Walker Syndrome�����������������������������������������������������������������������������������   67 Neuronal Proliferation Disorders���������������������������������������������������������������������������   68 Hemimegalencephaly�����������������������������������������������������������������������������������������   68 Neuronal Migration Disorders �������������������������������������������������������������������������������   68 Lissencephaly�����������������������������������������������������������������������������������������������������   68 Gray Matter Heterotopia�������������������������������������������������������������������������������������   68 Post-Migration Disorders���������������������������������������������������������������������������������������   68

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Polymicrogyria���������������������������������������������������������������������������������������������������   68 Schizencephaly���������������������������������������������������������������������������������������������������   68 Intracranial Hemorrhage���������������������������������������������������������������������������������������������   70 Preterm Infants�������������������������������������������������������������������������������������������������������   70 Periventricular Hemorrhagic Infarction �������������������������������������������������������������   72 Cerebellar Hemorrhage���������������������������������������������������������������������������������������   72 Term Infants �����������������������������������������������������������������������������������������������������������   72 Epidural Hemorrhage�����������������������������������������������������������������������������������������   72 Subdural Hemorrhage�����������������������������������������������������������������������������������������   74 Subpial Hemorrhage�������������������������������������������������������������������������������������������   75 Parenchymal Hemorrhage�����������������������������������������������������������������������������������   75 Choroid Plexus Hemorrhage�������������������������������������������������������������������������������   75 Hypoxic–Ischemic Injury�������������������������������������������������������������������������������������������   75 Global Hypoxic–Ischemic Injury���������������������������������������������������������������������������   76 Preterm Infants���������������������������������������������������������������������������������������������������   76 Term Infants �������������������������������������������������������������������������������������������������������   77 Focal Hypoxic–Ischemic Injury�����������������������������������������������������������������������������   78 Arterial Ischemic Stroke�������������������������������������������������������������������������������������   78 Venous Sinus Thrombosis�����������������������������������������������������������������������������������   81 Sickle Cell Disease���������������������������������������������������������������������������������������������   81 Infectious Brain Disorders �����������������������������������������������������������������������������������������   84 Viral Infections�������������������������������������������������������������������������������������������������������   84 Bacterial Infections�������������������������������������������������������������������������������������������������   86 Fungal Infections ���������������������������������������������������������������������������������������������������   88 Neoplastic Brain and Ventricular Disorders���������������������������������������������������������������   88 Neoplasms of the Brain�������������������������������������������������������������������������������������������   88 Neoplasms of the Ventricle�������������������������������������������������������������������������������������   88 Vascular Brain Disorders �������������������������������������������������������������������������������������������   89 High-Flow Malformations �������������������������������������������������������������������������������������   90 Low-Flow Malformations���������������������������������������������������������������������������������������   90 Hydrocephalus �����������������������������������������������������������������������������������������������������������   90 Benign External Hydrocephalus�����������������������������������������������������������������������������   92 Scalp Masses���������������������������������������������������������������������������������������������������������������   93 Congenital Scalp Lesions���������������������������������������������������������������������������������������   93 Dermoid/Epidermoid Cyst ���������������������������������������������������������������������������������   93 Cephalocele���������������������������������������������������������������������������������������������������������   94 Lymph Node�����������������������������������������������������������������������������������������������������������   94 Extracranial Birth Trauma���������������������������������������������������������������������������������������   95 Vascular Scalp Lesions�������������������������������������������������������������������������������������������   95 Infantile Hemangioma ���������������������������������������������������������������������������������������   95 Sinus Pericranii���������������������������������������������������������������������������������������������������   96 Suture Evaluation�������������������������������������������������������������������������������������������������������   97 Craniosynostosis�����������������������������������������������������������������������������������������������������   97 Positional Plagiocephaly�����������������������������������������������������������������������������������������   99 References�������������������������������������������������������������������������������������������������������������������   99 3 Spine����������������������������������������������������������������������������������������������������������������������������� 103 Maddy Artunduaga, Domen Plut, Abbey J. Winant, Ricardo Restrepo, and Edward Y. Lee Introduction�����������������������������������������������������������������������������������������������������������������  103 Technique�������������������������������������������������������������������������������������������������������������������  103 Patient Positioning �������������������������������������������������������������������������������������������������  103 Ultrasound Transducer Selection ���������������������������������������������������������������������������  104 Imaging Approaches�����������������������������������������������������������������������������������������������  104

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Normal Development and Anatomy���������������������������������������������������������������������������  104 Normal Development���������������������������������������������������������������������������������������������  104 Normal Anatomy�����������������������������������������������������������������������������������������������������  104 Spinal Cord���������������������������������������������������������������������������������������������������������  107 Central Canal �����������������������������������������������������������������������������������������������������  108 Ventriculus Terminalis ���������������������������������������������������������������������������������������  108 Filar Cyst�������������������������������������������������������������������������������������������������������������  109 Fatty Filum���������������������������������������������������������������������������������������������������������  109 Positional Nerve Root Clumping (“Pseudomass”)���������������������������������������������  110 Pseudosinus Tract�����������������������������������������������������������������������������������������������  110 Dysmorphic Coccyx�������������������������������������������������������������������������������������������  110 Congenital Spinal Anomalies�������������������������������������������������������������������������������������  110 Spinal Dysraphism �������������������������������������������������������������������������������������������������  111 Open Defect �������������������������������������������������������������������������������������������������������  112 Meningocele���������������������������������������������������������������������������������������������������  112 Myelocele and Myelomeningocele�����������������������������������������������������������������  112 Closed Defect�����������������������������������������������������������������������������������������������������  113 Simple Closed Defects�����������������������������������������������������������������������������������  113 Complex Closed Defects���������������������������������������������������������������������������������  114 Lipomatous Tissue and Dural Defect (Lipomyelomeningocele, Lipomyelocele)�����������������������������������������������������������������������������������������������  116 CSF-Containing Defects���������������������������������������������������������������������������������  116 Tethered Cord���������������������������������������������������������������������������������������������������������  116 Caudal Regression Syndrome���������������������������������������������������������������������������������  118 Spinal Lipoma���������������������������������������������������������������������������������������������������������  119 Segmental Spinal Dysgenesis���������������������������������������������������������������������������������  119 Infectious and Inflammatory Spinal Disorders�����������������������������������������������������������  120 Epidural Abscess�����������������������������������������������������������������������������������������������������  120 Pilonidal Sinus and Cyst�����������������������������������������������������������������������������������������  120 Neoplastic Spinal Disorders���������������������������������������������������������������������������������������  121 Intramedullary Tumors�������������������������������������������������������������������������������������������  122 Extramedullary Tumors �����������������������������������������������������������������������������������������  122 Sacrococcygeal Teratoma���������������������������������������������������������������������������������������  122 Traumatic Spinal Disorders ���������������������������������������������������������������������������������������  124 Lumbar Puncture�����������������������������������������������������������������������������������������������������  124 Spinal Cord Injury���������������������������������������������������������������������������������������������������  124 Spinal Cord Laceration and Transection�������������������������������������������������������������  124 Epidural/Subdural Hematoma and Hematomyelia���������������������������������������������  124 Hydromyelia/Syringomyelia/Syrinx���������������������������������������������������������������������������  125 References�������������������������������������������������������������������������������������������������������������������  125 4 Neck����������������������������������������������������������������������������������������������������������������������������� 127 Patricia T. Acharya, Sharon R. Gordon, Mark C. Liszewski, Ricardo Restrepo, and Edward Y. Lee Introduction�����������������������������������������������������������������������������������������������������������������  127 Technique�������������������������������������������������������������������������������������������������������������������  127 Patient Positioning �������������������������������������������������������������������������������������������������  127 Ultrasound Transducer Selection ���������������������������������������������������������������������������  127 Imaging Approaches�����������������������������������������������������������������������������������������������  128 Normal Development and Anatomy���������������������������������������������������������������������������  128 Neck �����������������������������������������������������������������������������������������������������������������������  128 Anterior Triangle�������������������������������������������������������������������������������������������������  128 Posterior Triangle�����������������������������������������������������������������������������������������������  128

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Lymph Nodes ���������������������������������������������������������������������������������������������������������  129 Thyroid Gland���������������������������������������������������������������������������������������������������������  130 Parathyroid Glands�������������������������������������������������������������������������������������������������  131 Salivary Glands�������������������������������������������������������������������������������������������������������  131 Parotid Glands�����������������������������������������������������������������������������������������������������  131 Submandibular Glands���������������������������������������������������������������������������������������  132 Sublingual Glands�����������������������������������������������������������������������������������������������  133 Neck ���������������������������������������������������������������������������������������������������������������������������  133 Congenital Neck Anomalies�����������������������������������������������������������������������������������  133 Congenital Nonvascular Neck Masses���������������������������������������������������������������  133 Congenital Benign Cystic Neck Masses���������������������������������������������������������  133 Congenital Benign Solid Neck Masses�����������������������������������������������������������  138 Congenital Vascular Neck Masses ���������������������������������������������������������������������  138 Hemangiomas�������������������������������������������������������������������������������������������������  138 Vascular Malformations ���������������������������������������������������������������������������������  140 Infectious and Inflammatory Neck Disorders���������������������������������������������������������  144 Cervical Lymphadenitis and Abscess�����������������������������������������������������������������  144 Mycobacterial Infection �������������������������������������������������������������������������������������  145 Other Infectious and Inflammatory Disorders ���������������������������������������������������  146 Neoplastic Neck Disorders�������������������������������������������������������������������������������������  146 Benign Neck Neoplasms�������������������������������������������������������������������������������������  146 Myofibromatosis���������������������������������������������������������������������������������������������  146 Neurofibroma �������������������������������������������������������������������������������������������������  147 Lipoma and Lipoblastoma �����������������������������������������������������������������������������  147 Malignant Neck Neoplasms�������������������������������������������������������������������������������  149 Lymphoma �����������������������������������������������������������������������������������������������������  149 Rhabdomyosarcoma���������������������������������������������������������������������������������������  150 Metastatic Disease ���������������������������������������������������������������������������������������������  150 Thyroid Gland�������������������������������������������������������������������������������������������������������������  151 Congenital Thyroid Gland Anomalies �������������������������������������������������������������������  151 Dysgenesis ���������������������������������������������������������������������������������������������������������  151 Dyshormonogenesis�������������������������������������������������������������������������������������������  152 Focal Thyroid Gland Lesions���������������������������������������������������������������������������������  152 Cystic Focal Thyroid Gland Lesions �����������������������������������������������������������������  152 Colloid Cysts���������������������������������������������������������������������������������������������������  152 Simple Cysts���������������������������������������������������������������������������������������������������  152 Complex (Hemorrhagic) Cysts�����������������������������������������������������������������������  152 Solid Focal Thyroid Gland Lesions �������������������������������������������������������������������  152 Benign Solid Focal Thyroid Gland Lesions���������������������������������������������������  154 Malignant Solid Focal Thyroid Gland Lesions�����������������������������������������������  155 Diffuse Parenchymal Thyroid Gland Lesions���������������������������������������������������������  157 Multinodular Goiter (Nodular Hyperplasia)�������������������������������������������������������  157 Infectious Diffuse Parenchymal Thyroid Gland Disorders���������������������������������  159 Acute Suppurative (Bacterial) Thyroiditis �����������������������������������������������������  159 Subacute (De Quervain) Thyroiditis���������������������������������������������������������������  159 Autoimmune-Mediated Diffuse Parenchymal Thyroid Gland Lesions �������������  159 Graves’ Disease�����������������������������������������������������������������������������������������������  159 Hashimoto Thyroiditis �����������������������������������������������������������������������������������  160 Parathyroid Glands�����������������������������������������������������������������������������������������������������  161 Parathyroid Cyst�����������������������������������������������������������������������������������������������������  161 Parathyroid Hyperplasia�����������������������������������������������������������������������������������������  162 Parathyroid Adenoma���������������������������������������������������������������������������������������������  162 Salivary Glands�����������������������������������������������������������������������������������������������������������  163

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Congenital Salivary Gland Anomalies �������������������������������������������������������������������  163 First Branchial Cleft Cyst�����������������������������������������������������������������������������������  163 Ranula�����������������������������������������������������������������������������������������������������������������  163 Infectious and Inflammatory Salivary Gland Disorders�����������������������������������������  164 Acute Infectious and Inflammatory Disorders���������������������������������������������������  164 Viral (Nonsuppurative) Inflammation�������������������������������������������������������������  164 Bacterial Parotitis and Abscess�����������������������������������������������������������������������  164 Recurrent and Chronic Infectious and Inflammatory Disorders�������������������������  165 Chronic Sialadenitis ���������������������������������������������������������������������������������������  165 Neoplastic Salivary Gland Disorders ���������������������������������������������������������������������  166 Benign Salivary Gland Masses���������������������������������������������������������������������������  166 Infantile Hemangioma �����������������������������������������������������������������������������������  166 Lymphatic Malformation �������������������������������������������������������������������������������  166 Malignant Salivary Gland Neoplasms ���������������������������������������������������������������  166 Mucoepidermoid Carcinoma �������������������������������������������������������������������������  166 Acinar Cell Carcinoma�����������������������������������������������������������������������������������  166 Other Malignant Salivary Gland Neoplasms �������������������������������������������������  167 Sialolithiasis�����������������������������������������������������������������������������������������������������������  167 References�������������������������������������������������������������������������������������������������������������������  168 5 Lung����������������������������������������������������������������������������������������������������������������������������� 173 Eric S. Bih, Monica Epelman, Ricardo Restrepo, and Edward Y. Lee Introduction�����������������������������������������������������������������������������������������������������������������  173 Technique�������������������������������������������������������������������������������������������������������������������  173 Patient Positioning �������������������������������������������������������������������������������������������������  173 Ultrasound Transducer Selection ���������������������������������������������������������������������������  173 Imaging Approaches�����������������������������������������������������������������������������������������������  174 Contrast-Enhanced Ultrasound�������������������������������������������������������������������������������  174 Normal Development and Anatomy���������������������������������������������������������������������������  174 Normal Development���������������������������������������������������������������������������������������������  174 Normal Anatomy�����������������������������������������������������������������������������������������������������  175 Ultrasound Signs���������������������������������������������������������������������������������������������������������  175 The Pleural Line�����������������������������������������������������������������������������������������������������  175 Lung Sliding�����������������������������������������������������������������������������������������������������������  175 A-Lines�������������������������������������������������������������������������������������������������������������������  176 B-Lines�������������������������������������������������������������������������������������������������������������������  176 M-Mode Appearance of the Normal Lung�������������������������������������������������������������  176 Hepatization and Air Bronchograms�����������������������������������������������������������������������  176 Congenital Lung Anomalies���������������������������������������������������������������������������������������  177 Congenital Lobar Hyperinflation ���������������������������������������������������������������������������  178 Foregut Duplication Cyst ���������������������������������������������������������������������������������������  179 Congenital Pulmonary Airway Malformation �������������������������������������������������������  180 Bronchopulmonary Sequestration���������������������������������������������������������������������������  180 Intralobar Bronchopulmonary Sequestration�����������������������������������������������������  181 Extralobar Bronchopulmonary Sequestration�����������������������������������������������������  182 Hybrid Congenital Lung Anomalies�������������������������������������������������������������������  183 Atelectasis and Consolidation�������������������������������������������������������������������������������������  183 Pulmonary Necrosis �����������������������������������������������������������������������������������������������  183 Pulmonary Abscess�������������������������������������������������������������������������������������������������  184 Interstitial Lung Disease���������������������������������������������������������������������������������������������  185 Pulmonary Lymphangiectasia�������������������������������������������������������������������������������������  188 Pulmonary Masses �����������������������������������������������������������������������������������������������������  188 Benign Pulmonary Masses�������������������������������������������������������������������������������������  189

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Malignant Pulmonary Neoplasms���������������������������������������������������������������������������  189 Primary Malignant Pulmonary Neoplasms���������������������������������������������������������  189 Pleuropulmonary Blastoma�����������������������������������������������������������������������������  189 Rhabdomyosarcoma���������������������������������������������������������������������������������������  189 Metastases�����������������������������������������������������������������������������������������������������������  190 References�������������������������������������������������������������������������������������������������������������������  191 6 Pleura��������������������������������������������������������������������������������������������������������������������������� 195 Nathan David P. Concepcion, Bernard F. Laya, Ross A. Myers, and Edward Y. Lee Introduction�����������������������������������������������������������������������������������������������������������������  195 Technique�������������������������������������������������������������������������������������������������������������������  195 Patient Positioning �������������������������������������������������������������������������������������������������  196 Ultrasound Transducer Selection ���������������������������������������������������������������������������  196 Imaging Approaches�����������������������������������������������������������������������������������������������  196 Normal Development and Anatomy���������������������������������������������������������������������������  196 Normal Development���������������������������������������������������������������������������������������������  197 Normal Anatomy�����������������������������������������������������������������������������������������������������  197 Anatomic Variants���������������������������������������������������������������������������������������������������  199 Normal Ultrasound Anatomy���������������������������������������������������������������������������������  199 A-Lines���������������������������������������������������������������������������������������������������������������  200 B-Lines���������������������������������������������������������������������������������������������������������������  200 T-Lines ���������������������������������������������������������������������������������������������������������������  200 Z-Lines���������������������������������������������������������������������������������������������������������������  201 Pleural Effusion����������������������������������������������������������������������������������������������������������  201 Simple Pleural Effusion �����������������������������������������������������������������������������������������  202 Complex Pleural Effusion���������������������������������������������������������������������������������������  202 Parapneumonic Effusion�����������������������������������������������������������������������������������������  203 Empyema �����������������������������������������������������������������������������������������������������������  204 Fibrothorax���������������������������������������������������������������������������������������������������������  204 Traumatic Effusion�������������������������������������������������������������������������������������������������  205 Hemorrhagic Effusion�����������������������������������������������������������������������������������������  205 Extrapleural Hematoma �������������������������������������������������������������������������������������  206 Chylous Effusion�����������������������������������������������������������������������������������������������������  206 Pneumothorax�������������������������������������������������������������������������������������������������������������  207 Absence of Lung Sliding ���������������������������������������������������������������������������������������  208 Stratosphere or Barcode Signs �������������������������������������������������������������������������������  209 Absence of B-Lines�������������������������������������������������������������������������������������������������  209 Lung Point���������������������������������������������������������������������������������������������������������������  209 Absence of Lung Pulse�������������������������������������������������������������������������������������������  209 Pleural Masses �����������������������������������������������������������������������������������������������������������  210 Malignant Pleural Masses���������������������������������������������������������������������������������������  211 Primary Neoplasms���������������������������������������������������������������������������������������������  211 Pleuropulmonary Blastoma�����������������������������������������������������������������������������  211 Rhabdomyosarcoma���������������������������������������������������������������������������������������  212 Metastases�����������������������������������������������������������������������������������������������������������  214 References�������������������������������������������������������������������������������������������������������������������  214 7 Mediastinum��������������������������������������������������������������������������������������������������������������� 219 Sumera Ali, Abbey J. Winant, Ricardo Restrepo, Pedro Daltro, and Edward Y. Lee Introduction�����������������������������������������������������������������������������������������������������������������  219 Technique�������������������������������������������������������������������������������������������������������������������  219 Patient Positioning �������������������������������������������������������������������������������������������������  219

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Ultrasound Transducer Selection ���������������������������������������������������������������������������  220 Imaging Approaches�����������������������������������������������������������������������������������������������  220 Normal Development and Anatomy���������������������������������������������������������������������������  220 Normal Development���������������������������������������������������������������������������������������������  220 Normal Anatomy�����������������������������������������������������������������������������������������������������  221 Compartment Approach �����������������������������������������������������������������������������������������  221 Thymus�������������������������������������������������������������������������������������������������������������������  223 Trachea�������������������������������������������������������������������������������������������������������������������  224 Esophagus���������������������������������������������������������������������������������������������������������������  224 Mediastinal Masses�����������������������������������������������������������������������������������������������������  225 Prevascular (Anterior) Mediastinal Masses �����������������������������������������������������������  225 Teratoma�������������������������������������������������������������������������������������������������������������  225 Lymphoma ���������������������������������������������������������������������������������������������������������  226 Lymphatic Malformation �����������������������������������������������������������������������������������  227 Visceral (Middle) Mediastinal Masses�������������������������������������������������������������������  229 Foregut Duplication Cysts ���������������������������������������������������������������������������������  229 Lymphadenopathy�����������������������������������������������������������������������������������������������  231 Infectious Lymphadenopathy�������������������������������������������������������������������������  231 Neoplastic Lymphadenopathy�������������������������������������������������������������������������  232 Paravertebral (Posterior) Mediastinal Masses���������������������������������������������������������  233 Neuroblastoma ���������������������������������������������������������������������������������������������������  233 Ganglioneuroblastoma ���������������������������������������������������������������������������������������  233 Ganglioneuroma�������������������������������������������������������������������������������������������������  234 Cardiophrenic Angle Masses �������������������������������������������������������������������������������������  235 Pericardial Cyst�������������������������������������������������������������������������������������������������������  235 Lymphadenopathy���������������������������������������������������������������������������������������������������  235 References�������������������������������������������������������������������������������������������������������������������  236 8 Chest Wall������������������������������������������������������������������������������������������������������������������� 239 Jessica Kurian Introduction�����������������������������������������������������������������������������������������������������������������  239 Technique�������������������������������������������������������������������������������������������������������������������  239 Patient Positioning �������������������������������������������������������������������������������������������������  239 Ultrasound Transducer Selection ���������������������������������������������������������������������������  239 Imaging Approaches�����������������������������������������������������������������������������������������������  241 Protocols�������������������������������������������������������������������������������������������������������������  241 Annotations���������������������������������������������������������������������������������������������������������  241 Contrast-Enhanced Ultrasound�������������������������������������������������������������������������������  241 Normal Development and Anatomy���������������������������������������������������������������������������  241 Normal Development���������������������������������������������������������������������������������������������  241 Thoracic Skeleton�����������������������������������������������������������������������������������������������  241 Chest Wall Soft Tissues���������������������������������������������������������������������������������������  242 Normal Anatomy�����������������������������������������������������������������������������������������������������  243 Thoracic Skeleton�����������������������������������������������������������������������������������������������  243 Musculature���������������������������������������������������������������������������������������������������������  244 Ultrasound Appearance of Normal Chest Wall Anatomy���������������������������������������  246 Congenital Chest Wall Anomalies �����������������������������������������������������������������������������  247 Vascular Tumors and Malformations ���������������������������������������������������������������������  247 Hemangioma�������������������������������������������������������������������������������������������������������  248 Venous Malformation�����������������������������������������������������������������������������������������  250 Lymphatic Malformation �����������������������������������������������������������������������������������  251 Osseous and Cartilaginous Lesions �����������������������������������������������������������������������  251 Osteochondroma (Exostosis) �����������������������������������������������������������������������������  251 Asymmetric Cartilaginous Costochondral Junction�������������������������������������������  252 Enlarged Rib Ends ���������������������������������������������������������������������������������������������  253

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Infectious Disorders of the Chest Wall�����������������������������������������������������������������������  255 Cellulitis�����������������������������������������������������������������������������������������������������������������  255 Abscess�������������������������������������������������������������������������������������������������������������������  256 Neoplastic Disorders of the Chest Wall ���������������������������������������������������������������������  256 Benign Chest Wall Neoplasms�������������������������������������������������������������������������������  257 Lipoma ���������������������������������������������������������������������������������������������������������������  257 Mesenchymal Hamartoma ���������������������������������������������������������������������������������  257 Malignant Chest Wall Neoplasms���������������������������������������������������������������������������  258 Rhabdomyosarcoma�������������������������������������������������������������������������������������������  258 Ewing Sarcoma���������������������������������������������������������������������������������������������������  259 Osteosarcoma�����������������������������������������������������������������������������������������������������  260 Lymphoma ���������������������������������������������������������������������������������������������������������  261 Metastases�����������������������������������������������������������������������������������������������������������  262 Traumatic Disorders of the Chest Wall�����������������������������������������������������������������������  262 Hematoma���������������������������������������������������������������������������������������������������������������  262 Rib Fracture �����������������������������������������������������������������������������������������������������������  264 Foreign Bodies �����������������������������������������������������������������������������������������������������������  265 References�������������������������������������������������������������������������������������������������������������������  266 9 Diaphragm������������������������������������������������������������������������������������������������������������������� 271 Wendy G. Kim, Helen H. R. Kim, Grace S. Phillips, and Edward Y. Lee Introduction�����������������������������������������������������������������������������������������������������������������  271 Technique�������������������������������������������������������������������������������������������������������������������  271 Patient Positioning �������������������������������������������������������������������������������������������������  271 Ultrasound Transducer Selection ���������������������������������������������������������������������������  271 Imaging Approaches�����������������������������������������������������������������������������������������������  272 Normal Development and Anatomy���������������������������������������������������������������������������  272 Normal Development���������������������������������������������������������������������������������������������  272 Normal Anatomy�����������������������������������������������������������������������������������������������������  273 Congenital Diaphragmatic Anomalies �����������������������������������������������������������������������  274 Diaphragmatic Hernia���������������������������������������������������������������������������������������������  274 Bochdalek Hernia�����������������������������������������������������������������������������������������������  274 Morgagni Hernia�������������������������������������������������������������������������������������������������  275 Hiatal Hernia�������������������������������������������������������������������������������������������������������  275 Diaphragmatic Eventration�������������������������������������������������������������������������������������  277 Acquired Diaphragmatic Disorders ���������������������������������������������������������������������������  278 Diaphragmatic Dysfunction �����������������������������������������������������������������������������������  278 Diaphragmatic Inversion�����������������������������������������������������������������������������������������  279 Primary Diaphragmatic Masses ���������������������������������������������������������������������������������  279 Benign Masses �������������������������������������������������������������������������������������������������������  279 Malignant Neoplasms���������������������������������������������������������������������������������������������  280 Traumatic Disorders���������������������������������������������������������������������������������������������������  280 References�������������������������������������������������������������������������������������������������������������������  281 10 The Gastrointestinal Tract����������������������������������������������������������������������������������������� 283 Marthe M. Munden and Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  283 Esophagus�������������������������������������������������������������������������������������������������������������������  284 Technique���������������������������������������������������������������������������������������������������������������  284 Patient Positioning ���������������������������������������������������������������������������������������������  284 Ultrasound Transducer Selection �����������������������������������������������������������������������  284 Imaging Approaches�������������������������������������������������������������������������������������������  284 Normal Development and Anatomy�����������������������������������������������������������������������  284 Normal Development�����������������������������������������������������������������������������������������  284

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Normal Anatomy�������������������������������������������������������������������������������������������������  285 Gastroesophageal Reflux ���������������������������������������������������������������������������������������  286 Hiatal Hernia�����������������������������������������������������������������������������������������������������������  286 Stomach�����������������������������������������������������������������������������������������������������������������������  288 Technique���������������������������������������������������������������������������������������������������������������  288 Patient Positioning ���������������������������������������������������������������������������������������������  288 Ultrasound Transducer Selection �����������������������������������������������������������������������  289 Imaging Approaches�������������������������������������������������������������������������������������������  289 Normal Development and Anatomy�����������������������������������������������������������������������  290 Normal Development�����������������������������������������������������������������������������������������  290 Normal Anatomy�������������������������������������������������������������������������������������������������  290 Congenital Anomalies���������������������������������������������������������������������������������������������  290 Gastric Atresia�����������������������������������������������������������������������������������������������������  290 Microgastria �������������������������������������������������������������������������������������������������������  290 Gastric Diaphragm (Antral Web) �����������������������������������������������������������������������  292 Acquired Obstruction���������������������������������������������������������������������������������������������  292 Hypertrophic Pyloric Stenosis ���������������������������������������������������������������������������  292 Pylorospasm�������������������������������������������������������������������������������������������������������  293 Prostaglandin-Induced Foveolar Hyperplasia�����������������������������������������������������  294 Gastric Volvulus �������������������������������������������������������������������������������������������������  294 Gastric Wall Thickening�����������������������������������������������������������������������������������������  297 Gastritis���������������������������������������������������������������������������������������������������������������  297 Ménétrier Disease�����������������������������������������������������������������������������������������������  297 Eosinophilic Gastroenteritis�������������������������������������������������������������������������������  297 Chronic Granulomatous Disease of the Stomach�����������������������������������������������  298 Benign Masses of the Stomach�������������������������������������������������������������������������������  298 Gastric Duplication Cyst�������������������������������������������������������������������������������������  298 Gastric Teratoma�������������������������������������������������������������������������������������������������  300 Gastric Lipoma���������������������������������������������������������������������������������������������������  300 Focal Foveolar Hyperplasia of the Stomach�������������������������������������������������������  300 Inflammatory Gastric Myofibroblastic Tumor ���������������������������������������������������  300 Gastric Bezoar�����������������������������������������������������������������������������������������������������  301 Other Benign Masses �����������������������������������������������������������������������������������������  301 Malignant Gastric Tumors �������������������������������������������������������������������������������������  301 Lymphoma ���������������������������������������������������������������������������������������������������������  301 GI Stromal Tumor�����������������������������������������������������������������������������������������������  303 Other Malignant Masses�������������������������������������������������������������������������������������  303 Small Bowel���������������������������������������������������������������������������������������������������������������  305 Technique���������������������������������������������������������������������������������������������������������������  305 Patient Positioning ���������������������������������������������������������������������������������������������  305 Ultrasound Transducer Selection �����������������������������������������������������������������������  305 Imaging Approaches�������������������������������������������������������������������������������������������  305 Normal Development and Anatomy�����������������������������������������������������������������������  305 Normal Development�����������������������������������������������������������������������������������������  305 Normal Anatomy�������������������������������������������������������������������������������������������������  305 Congenital Anomalies���������������������������������������������������������������������������������������������  306 Duodenal Atresia, Stenosis, and Web�����������������������������������������������������������������  306 Intestinal Atresia�������������������������������������������������������������������������������������������������  307 Jejunal and Ileal Stenosis �����������������������������������������������������������������������������������  308 Midgut Malrotation���������������������������������������������������������������������������������������������  309 Meconium Ileus �������������������������������������������������������������������������������������������������  311 Meconium Peritonitis and Pseudocyst ���������������������������������������������������������������  312 Acquired Obstruction���������������������������������������������������������������������������������������������  313

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Intussusception���������������������������������������������������������������������������������������������������  313 Small Bowel Intussusception �������������������������������������������������������������������������  313 Ileocolic Intussusception���������������������������������������������������������������������������������  315 Small Bowel Wall Thickening �������������������������������������������������������������������������������  316 Infectious Enteritis ���������������������������������������������������������������������������������������������  316 Crohn Disease�����������������������������������������������������������������������������������������������������  317 Hemorrhage���������������������������������������������������������������������������������������������������������  319 Trauma �����������������������������������������������������������������������������������������������������������  319 Henoch–Schönlein Purpura ���������������������������������������������������������������������������  319 Eosinophilic Gastroenteritis�������������������������������������������������������������������������������  320 Lymphangiectasia�����������������������������������������������������������������������������������������������  321 Cystic Fibrosis ���������������������������������������������������������������������������������������������������  321 Graft-Versus-Host Disease���������������������������������������������������������������������������������  322 Meckel Diverticulum ���������������������������������������������������������������������������������������������  323 Benign Masses �������������������������������������������������������������������������������������������������������  324 Duplication Cyst�������������������������������������������������������������������������������������������������  324 Mesenteric Cyst �������������������������������������������������������������������������������������������������  326 Intestinal Polyp���������������������������������������������������������������������������������������������������  327 Vascular Anomalies���������������������������������������������������������������������������������������������  327 Infantile Hemangioma �����������������������������������������������������������������������������������  327 Blue Rubber Bleb Nevus Syndrome���������������������������������������������������������������  327 Cutaneovisceral Angiomatosis with Thrombocytopenia �������������������������������  328 Malignant Masses���������������������������������������������������������������������������������������������������  329 Hodgkin and Non-Hodgkin Lymphoma�������������������������������������������������������������  329 Appendix���������������������������������������������������������������������������������������������������������������������  330 Technique���������������������������������������������������������������������������������������������������������������  330 Patient Positioning ���������������������������������������������������������������������������������������������  330 Ultrasound Transducer Selection �����������������������������������������������������������������������  330 Imaging Approaches�������������������������������������������������������������������������������������������  330 Normal Development and Anatomy���������������������������������������������������������������������������  330 Normal Development���������������������������������������������������������������������������������������������  330 Normal Anatomy�����������������������������������������������������������������������������������������������������  330 Acute Appendicitis�������������������������������������������������������������������������������������������������  331 Cystic Fibrosis of the Appendix�����������������������������������������������������������������������������  332 Benign Masses of the Appendix�����������������������������������������������������������������������������  333 Mucocele of the Appendix ���������������������������������������������������������������������������������  333 Malignant Tumors of the Appendix �����������������������������������������������������������������������  333 Carcinoid�������������������������������������������������������������������������������������������������������������  333 Lymphoma of the Appendix�������������������������������������������������������������������������������  333 Colon���������������������������������������������������������������������������������������������������������������������������  334 Technique���������������������������������������������������������������������������������������������������������������  334 Patient Positioning ���������������������������������������������������������������������������������������������  334 Ultrasound Transducer Selection �����������������������������������������������������������������������  334 Imaging Approaches�������������������������������������������������������������������������������������������  334 Normal Development and Anatomy���������������������������������������������������������������������������  334 Normal Development���������������������������������������������������������������������������������������������  334 Normal Anatomy�����������������������������������������������������������������������������������������������������  335 Congenital Anomalies���������������������������������������������������������������������������������������������  335 Anorectal Malformations �����������������������������������������������������������������������������������  335 Colonic Wall Thickening ���������������������������������������������������������������������������������������  337 Necrotizing Enterocolitis �����������������������������������������������������������������������������������  337 Ulcerative Colitis �����������������������������������������������������������������������������������������������  337 Crohn Disease�����������������������������������������������������������������������������������������������������  339

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Infectious Colitis�������������������������������������������������������������������������������������������������  340 Pseudomembranous Colitis���������������������������������������������������������������������������������  341 Neutropenic Colitis���������������������������������������������������������������������������������������������  342 Cystic Fibrosis ���������������������������������������������������������������������������������������������������  343 Hemolytic–Uremic Syndrome ���������������������������������������������������������������������������  343 Benign Masses �������������������������������������������������������������������������������������������������������  344 Juvenile Polyp�����������������������������������������������������������������������������������������������������  344 Duplication Cyst�������������������������������������������������������������������������������������������������  345 Malignant Tumors���������������������������������������������������������������������������������������������������  345 Lymphoma ���������������������������������������������������������������������������������������������������������  345 Adenocarcinoma�������������������������������������������������������������������������������������������������  345 References�������������������������������������������������������������������������������������������������������������������  347 11 Liver����������������������������������������������������������������������������������������������������������������������������� 355 Jeannie K. Kwon, Maddy Artunduaga, Javier D. Gonzalez, Alexandra M. Foust, Elisabeth P. Moredock, Süreyya Burcu Görkem, and Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  356 Technique�������������������������������������������������������������������������������������������������������������������  356 Patient Positioning �������������������������������������������������������������������������������������������������  356 Ultrasound Transducer Selection ���������������������������������������������������������������������������  356 Imaging Approaches�����������������������������������������������������������������������������������������������  356 Grayscale Imaging �������������������������������������������������������������������������������������������������  356 Doppler Ultrasound�������������������������������������������������������������������������������������������������  357 Contrast-Enhanced Ultrasound�������������������������������������������������������������������������������  358 Elastography�����������������������������������������������������������������������������������������������������������  359 Normal Development and Anatomy���������������������������������������������������������������������������  360 Normal Development���������������������������������������������������������������������������������������������  360 Normal Anatomy�����������������������������������������������������������������������������������������������������  363 Segmental and Lobar Anatomy���������������������������������������������������������������������������  363 Ligaments�����������������������������������������������������������������������������������������������������������  364 Hepatic Circulation���������������������������������������������������������������������������������������������  366 Normal Hepatic Parenchyma �����������������������������������������������������������������������������  367 Anatomic Variants�����������������������������������������������������������������������������������������������  367 Congenital Anomalies�������������������������������������������������������������������������������������������������  369 Liver Cyst���������������������������������������������������������������������������������������������������������������  369 Polycystic Liver Disease�����������������������������������������������������������������������������������������  369 Congenital Portosystemic Shunts���������������������������������������������������������������������������  370 Diffuse Parenchymal Disease�������������������������������������������������������������������������������������  371 Nonalcoholic Fatty Liver Disease���������������������������������������������������������������������������  371 Fibrosis�������������������������������������������������������������������������������������������������������������������  372 Hemochromatosis���������������������������������������������������������������������������������������������������  374 Cirrhosis�����������������������������������������������������������������������������������������������������������������  374 Infection ���������������������������������������������������������������������������������������������������������������������  375 Viral Hepatitis���������������������������������������������������������������������������������������������������������  375 Bacterial Infection���������������������������������������������������������������������������������������������������  375 Fungal Infection �����������������������������������������������������������������������������������������������������  378 Parasitic Infection���������������������������������������������������������������������������������������������������  378 Trauma �����������������������������������������������������������������������������������������������������������������������  380 Blunt Abdominal Trauma���������������������������������������������������������������������������������������  380 Umbilical Vein Catheterization�������������������������������������������������������������������������������  380 Portal Hypertension ���������������������������������������������������������������������������������������������������  382 Budd–Chiari Syndrome ���������������������������������������������������������������������������������������������  383 Sinusoidal Obstruction Syndrome �����������������������������������������������������������������������������  384

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Peliosis Hepatis�����������������������������������������������������������������������������������������������������������  385 Passive Venous Congestion�����������������������������������������������������������������������������������������  386 Portal Venous Gas�������������������������������������������������������������������������������������������������������  386 Tumors �����������������������������������������������������������������������������������������������������������������������  387 Benign Masses �������������������������������������������������������������������������������������������������������  387 Congenital Hemangioma �����������������������������������������������������������������������������������  387 Infantile Hemangioma ���������������������������������������������������������������������������������������  391 Mesenchymal Hamartoma ���������������������������������������������������������������������������������  392 Focal Nodular Hyperplasia���������������������������������������������������������������������������������  393 Hepatic Adenoma�����������������������������������������������������������������������������������������������  394 Malignant Tumors���������������������������������������������������������������������������������������������������  397 Hepatoblastoma���������������������������������������������������������������������������������������������������  397 Hepatocellular Carcinoma ���������������������������������������������������������������������������������  400 Fibrolamellar Hepatocellular Carcinoma�����������������������������������������������������������  401 Rare Primary Tumors�����������������������������������������������������������������������������������������  402 Metastases�����������������������������������������������������������������������������������������������������������  403 Lymphoma ���������������������������������������������������������������������������������������������������������  404 Posttransplant Lymphoproliferative Disorder�����������������������������������������������������  405 Leukemia�������������������������������������������������������������������������������������������������������������  407 Liver Transplantation �������������������������������������������������������������������������������������������������  408 Introduction�������������������������������������������������������������������������������������������������������������  408 Surgical Technique�������������������������������������������������������������������������������������������������  409 Whole Liver Transplantation �����������������������������������������������������������������������������  410 Living-Related Donor and Split Liver Grafts�����������������������������������������������������  410 Preoperative and Postoperative Imaging Considerations���������������������������������������  411 Normal Liver Transplant Ultrasound ���������������������������������������������������������������������  412 Rejection�����������������������������������������������������������������������������������������������������������������  412 Biliary Complications���������������������������������������������������������������������������������������������  413 Bile Leak�������������������������������������������������������������������������������������������������������������  413 Biliary Stricture���������������������������������������������������������������������������������������������������  414 Vascular Complications �����������������������������������������������������������������������������������������  415 Hepatic Artery Thrombosis���������������������������������������������������������������������������������  415 Hepatic Artery Stenosis���������������������������������������������������������������������������������������  415 Hepatic Artery Pseudoaneurysm�������������������������������������������������������������������������  418 Portal Vein Thrombosis���������������������������������������������������������������������������������������  418 Portal Vein Stenosis��������������������������������������������������������������������������������������������  419 Hepatic Vein Outflow Obstruction ���������������������������������������������������������������������  420 Inferior Vena Caval Stenosis and Thrombosis ���������������������������������������������������  422 Fluid Collections�����������������������������������������������������������������������������������������������������  423 Extrahepatic Collections�������������������������������������������������������������������������������������  423 Intrahepatic Collections �������������������������������������������������������������������������������������  425 References�������������������������������������������������������������������������������������������������������������������  426 12 Gallbladder and Biliary Tract����������������������������������������������������������������������������������� 433 Christian L. Carlson, Mitchell W. Boehnke, and Harriet J. Paltiel Gallbladder�����������������������������������������������������������������������������������������������������������������  433 Technique���������������������������������������������������������������������������������������������������������������  433 Patient Positioning ���������������������������������������������������������������������������������������������  433 Ultrasound Transducer Selection �����������������������������������������������������������������������  434 Imaging Approaches�������������������������������������������������������������������������������������������  434 Normal Development and Anatomy�����������������������������������������������������������������������  434 Normal Development�����������������������������������������������������������������������������������������  434 Normal Anatomy�������������������������������������������������������������������������������������������������  434 Anatomic Variants���������������������������������������������������������������������������������������������������  436

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Congenital Anomalies���������������������������������������������������������������������������������������������  436 Agenesis/Hypoplasia�������������������������������������������������������������������������������������������  436 Ectopia ���������������������������������������������������������������������������������������������������������������  437 Septate Gallbladder���������������������������������������������������������������������������������������������  438 Duplication���������������������������������������������������������������������������������������������������������  439 Cholelithiasis����������������������������������������������������������������������������������������������������������  440 Sludge���������������������������������������������������������������������������������������������������������������������  442 Cholecystitis�����������������������������������������������������������������������������������������������������������  444 Acute Calculous Cholecystitis ���������������������������������������������������������������������������  444 Acute Acalculous Cholecystitis �������������������������������������������������������������������������  447 Biliary Dyskinesia�����������������������������������������������������������������������������������������������  447 Chronic Cholecystitis�����������������������������������������������������������������������������������������  449 Porcelain Gallbladder�����������������������������������������������������������������������������������������  449 Hydrops�������������������������������������������������������������������������������������������������������������������  449 Torsion �������������������������������������������������������������������������������������������������������������������  450 Polyps���������������������������������������������������������������������������������������������������������������������  450 Adenomyomatosis�����������������������������������������������������������������������������������������������  451 Cholesterol Polyps ���������������������������������������������������������������������������������������������  451 Inflammatory Polyps�������������������������������������������������������������������������������������������  452 Other Polypoid Lesions���������������������������������������������������������������������������������������  452 Other Disorders�������������������������������������������������������������������������������������������������������  453 Gallbladder Varices���������������������������������������������������������������������������������������������  453 Trauma ���������������������������������������������������������������������������������������������������������������  453 Biliary Tract ���������������������������������������������������������������������������������������������������������������  455 Technique���������������������������������������������������������������������������������������������������������������  455 Normal Development and Anatomy�����������������������������������������������������������������������  455 Normal Development�����������������������������������������������������������������������������������������  455 Normal Anatomy�������������������������������������������������������������������������������������������������  455 Anatomic Variants���������������������������������������������������������������������������������������������������  456 Congenital Anomalies���������������������������������������������������������������������������������������������  457 Choledochal Cysts ���������������������������������������������������������������������������������������������  457 Caroli Disease�����������������������������������������������������������������������������������������������������  459 Biliary Tract Obstruction ���������������������������������������������������������������������������������������  462 Biliary Atresia�����������������������������������������������������������������������������������������������������  462 Neonatal Hepatitis Syndrome�����������������������������������������������������������������������������  463 Alagille Syndrome ���������������������������������������������������������������������������������������������  465 Byler Disease �����������������������������������������������������������������������������������������������������  469 Choledocholithiasis���������������������������������������������������������������������������������������������  469 Inspissated Bile Syndrome���������������������������������������������������������������������������������  470 Sclerosing Cholangitis ���������������������������������������������������������������������������������������  471 Mirizzi Syndrome�����������������������������������������������������������������������������������������������  471 Bile Duct Stricture ���������������������������������������������������������������������������������������������  472 AIDS Cholangiopathy�����������������������������������������������������������������������������������������  472 Spontaneous Perforation of the Extrahepatic Bile Ducts���������������������������������������  472 Biliary Tract Trauma�����������������������������������������������������������������������������������������������  472 Tumors �������������������������������������������������������������������������������������������������������������������  473 Benign Masses ���������������������������������������������������������������������������������������������������  473 Granular Cell Tumor���������������������������������������������������������������������������������������  473 Bile Duct Adenoma�����������������������������������������������������������������������������������������  473 Malignant Bile Duct Tumors �����������������������������������������������������������������������������  473 Rhabdomyosarcoma of the Bile Duct�������������������������������������������������������������  473 Cholangiocarcinoma���������������������������������������������������������������������������������������  474 Neuroendocrine Tumor�����������������������������������������������������������������������������������  474 Metastases�������������������������������������������������������������������������������������������������������  474

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References�������������������������������������������������������������������������������������������������������������������  475 13 Spleen and Peritoneal Cavity������������������������������������������������������������������������������������� 481 Patrick Duffy, Ilse Castro-Aragon, Patrick Tivnan, Frank M. Volberg, Ella Kipervasser, Zoltan Harkanyi, and Harriet J. Paltiel Spleen�������������������������������������������������������������������������������������������������������������������������  482 Introduction�������������������������������������������������������������������������������������������������������������  482 Technique���������������������������������������������������������������������������������������������������������������  482 Patient Positioning ���������������������������������������������������������������������������������������������  482 Ultrasound Transducer Selection �����������������������������������������������������������������������  482 Imaging Approaches�������������������������������������������������������������������������������������������  482 Normal Development and Anatomy�����������������������������������������������������������������������  482 Normal Development�����������������������������������������������������������������������������������������  482 Normal Anatomy�������������������������������������������������������������������������������������������������  482 Anatomic Variants���������������������������������������������������������������������������������������������������  487 Lobulations and Clefts ���������������������������������������������������������������������������������������  487 Accessory Spleen �����������������������������������������������������������������������������������������������  487 Congenital Anomalies���������������������������������������������������������������������������������������������  490 Wandering Spleen�����������������������������������������������������������������������������������������������  490 Polysplenia, Hyposplenia, and Asplenia�������������������������������������������������������������  491 Nonparasitic Splenic Cysts���������������������������������������������������������������������������������  493 Splenogonadal Fusion�����������������������������������������������������������������������������������������  493 Splenopancreatic Fusion�������������������������������������������������������������������������������������  493 Infection �����������������������������������������������������������������������������������������������������������������  494 Pyogenic Abscess�����������������������������������������������������������������������������������������������  494 Fungal Abscess���������������������������������������������������������������������������������������������������  494 Tuberculous Infection�����������������������������������������������������������������������������������������  497 Epstein-Barr Viral Infection�������������������������������������������������������������������������������  498 Parasitic Infection�����������������������������������������������������������������������������������������������  498 Acquired Immunodeficiency Syndrome�������������������������������������������������������������  501 Inflammatory Disorders �����������������������������������������������������������������������������������������  502 Sarcoidosis ���������������������������������������������������������������������������������������������������������  502 Rheumatic Disorders�������������������������������������������������������������������������������������������  503 Granulomatosis with Polyangiitis�����������������������������������������������������������������������  504 Hemoglobinopathies�����������������������������������������������������������������������������������������������  504 Lysosomal Storage Diseases�����������������������������������������������������������������������������������  506 Portal Hypertension �����������������������������������������������������������������������������������������������  508 Trauma �������������������������������������������������������������������������������������������������������������������  508 Splenosis�������������������������������������������������������������������������������������������������������������  511 Vascular Anomalies�������������������������������������������������������������������������������������������������  511 Lymphatic Malformation �����������������������������������������������������������������������������������  511 Venous Malformation�����������������������������������������������������������������������������������������  513 Kaposiform Lymphangiomatosis �����������������������������������������������������������������������  513 Peliosis �������������������������������������������������������������������������������������������������������������������  515 Benign Masses �������������������������������������������������������������������������������������������������������  516 Hamartoma���������������������������������������������������������������������������������������������������������  516 Extramedullary Hematopoiesis���������������������������������������������������������������������������  516 Inflammatory Myofibroblastic Tumor�����������������������������������������������������������������  516 Hemangioma�������������������������������������������������������������������������������������������������������  517 Littoral Cell Angioma�����������������������������������������������������������������������������������������  517 Malignant Tumors���������������������������������������������������������������������������������������������������  518 Lymphoma ���������������������������������������������������������������������������������������������������������  518 Leukemia�������������������������������������������������������������������������������������������������������������  519 Angiosarcoma�����������������������������������������������������������������������������������������������������  520

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Kaposiform Hemangioendothelioma �����������������������������������������������������������������  521 Metastatic Disease ���������������������������������������������������������������������������������������������  521 Neuroblastoma �����������������������������������������������������������������������������������������������  521 Langerhans Cell Histiocytosis �������������������������������������������������������������������������������  521 Complications of Pancreatitis���������������������������������������������������������������������������������  522 Gamna-Gandy Bodies���������������������������������������������������������������������������������������������  523 Peritoneal Cavity���������������������������������������������������������������������������������������������������������  524 Introduction�������������������������������������������������������������������������������������������������������������  524 Technique���������������������������������������������������������������������������������������������������������������  524 Patient Positioning ���������������������������������������������������������������������������������������������  524 Ultrasound Transducer Selection �����������������������������������������������������������������������  524 Imaging Approaches�������������������������������������������������������������������������������������������  524 Normal Development and Anatomy�����������������������������������������������������������������������  524 Normal Development�����������������������������������������������������������������������������������������  524 Normal Anatomy�������������������������������������������������������������������������������������������������  524 Omentum�������������������������������������������������������������������������������������������������������������  526 Mesentery�����������������������������������������������������������������������������������������������������������  526 Peritoneal Fluid���������������������������������������������������������������������������������������������������  528 Normal Flow of Peritoneal Fluid �������������������������������������������������������������������  528 Ascites���������������������������������������������������������������������������������������������������������������������  528 Hemoperitoneum�������������������������������������������������������������������������������������������������  530 Chylous Ascites���������������������������������������������������������������������������������������������������  531 Urine Ascites�������������������������������������������������������������������������������������������������������  532 Localized Peritoneal Fluid Collections�������������������������������������������������������������������  532 Cerebrospinal Fluid Pseudocyst�������������������������������������������������������������������������  532 Biloma�����������������������������������������������������������������������������������������������������������������  533 Pancreatic Pseudocyst�����������������������������������������������������������������������������������������  534 Peritoneal Inclusion Cyst �����������������������������������������������������������������������������������  535 Diaphragmatic Mesothelial Cyst�������������������������������������������������������������������������  535 Peritoneal Inflammation�����������������������������������������������������������������������������������������  535 Infective Peritonitis���������������������������������������������������������������������������������������������  535 Tuberculous Peritonitis�����������������������������������������������������������������������������������  536 Chemical Peritonitis�������������������������������������������������������������������������������������������  537 Granulomatous Peritonitis ���������������������������������������������������������������������������������  537 Sclerosing Encapsulating Peritonitis�������������������������������������������������������������������  537 Abscess���������������������������������������������������������������������������������������������������������������  539 Pneumoperitoneum�������������������������������������������������������������������������������������������������  540 Omental Cyst ���������������������������������������������������������������������������������������������������������  540 Segmental Omental Infarction �������������������������������������������������������������������������������  540 Mesenteric Lymphadenitis �������������������������������������������������������������������������������������  541 Vascular Malformations �����������������������������������������������������������������������������������������  542 Lymphatic Malformation �����������������������������������������������������������������������������������  542 Venous Malformation�����������������������������������������������������������������������������������������  542 Benign Masses �������������������������������������������������������������������������������������������������������  545 Infantile Hemangioma ���������������������������������������������������������������������������������������  545 Lipoma ���������������������������������������������������������������������������������������������������������������  546 Lipomatosis���������������������������������������������������������������������������������������������������������  546 Lipoblastoma/Lipoblastomatosis �����������������������������������������������������������������������  547 Neurofibroma �����������������������������������������������������������������������������������������������������  547 Plexiform Neurofibroma���������������������������������������������������������������������������������  547 Desmoid Tumor �������������������������������������������������������������������������������������������������  548 Castleman Disease ���������������������������������������������������������������������������������������������  549 Inflammatory Myofibroblastic Tumor�����������������������������������������������������������������  550

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Malignant Tumors���������������������������������������������������������������������������������������������������  551 Primary Tumors �������������������������������������������������������������������������������������������������  551 Lymphoma �����������������������������������������������������������������������������������������������������  551 Rhabdomyosarcoma���������������������������������������������������������������������������������������  551 Desmoplastic Small Round Cell Tumor���������������������������������������������������������  553 Malignant Mesothelioma �������������������������������������������������������������������������������  554 Metastatic Disease ���������������������������������������������������������������������������������������������  555 Neuroblastoma �����������������������������������������������������������������������������������������������  555 Adenocarcinoma���������������������������������������������������������������������������������������������  555 Wilms’ Tumor�������������������������������������������������������������������������������������������������  555 Germ Cell Tumor �������������������������������������������������������������������������������������������  555 Intracranial Neoplasms�����������������������������������������������������������������������������������  555 References�������������������������������������������������������������������������������������������������������������������  555 14 Pancreas, Adrenal Glands, and Retroperitoneum��������������������������������������������������� 563 Anastasia L. Hryhorczuk and Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  563 Pancreas ���������������������������������������������������������������������������������������������������������������������  564 Technique���������������������������������������������������������������������������������������������������������������  564 Patient Positioning ���������������������������������������������������������������������������������������������  564 Ultrasound Transducer Selection �����������������������������������������������������������������������  564 Imaging Approaches�������������������������������������������������������������������������������������������  564 Normal Development and Anatomy�����������������������������������������������������������������������  564 Normal Development�����������������������������������������������������������������������������������������  564 Normal Anatomy�������������������������������������������������������������������������������������������������  564 Anatomic Variants���������������������������������������������������������������������������������������������������  566 Lobulated Parenchymal Contour �����������������������������������������������������������������������  566 Congenital Anomalies���������������������������������������������������������������������������������������������  566 Pancreas Divisum�����������������������������������������������������������������������������������������������  566 Annular Pancreas �����������������������������������������������������������������������������������������������  566 Common Pancreaticobiliary Channel�����������������������������������������������������������������  567 Partial Pancreatic Agenesis���������������������������������������������������������������������������������  567 Accessory Pancreatic Lobe���������������������������������������������������������������������������������  567 Ectopic Pancreas�������������������������������������������������������������������������������������������������  569 Congenital Hyperinsulinism�������������������������������������������������������������������������������  569 Congenital Pancreatic Cyst���������������������������������������������������������������������������������  569 Genetic Disorders with Associated Pancreatic Abnormalities�������������������������������  570 Cystic Fibrosis ���������������������������������������������������������������������������������������������������  570 Shwachman-Diamond Syndrome�����������������������������������������������������������������������  570 Beckwith-Wiedemann Syndrome�����������������������������������������������������������������������  571 Autosomal Dominant Polycystic Kidney Disease ���������������������������������������������  571 Von Hippel-Lindau Disease �������������������������������������������������������������������������������  571 Acute Pancreatitis���������������������������������������������������������������������������������������������������  572 Acute Peripancreatic Fluid Collections �������������������������������������������������������������  573 Pseudocysts���������������������������������������������������������������������������������������������������������  573 Pancreaticopleural Fistula�����������������������������������������������������������������������������������  575 Necrotizing Pancreatitis �������������������������������������������������������������������������������������  575 Vascular Complications �������������������������������������������������������������������������������������  576 Acute Recurrent and Chronic Pancreatitis �������������������������������������������������������������  576 Trauma �������������������������������������������������������������������������������������������������������������������  577 Pancreatic Venous and Lymphatic Malformations�������������������������������������������������  579 Benign Pancreatic Neoplasms���������������������������������������������������������������������������������  579 Serous Cystadenoma�������������������������������������������������������������������������������������������  579

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Mucinous Cystadenoma�������������������������������������������������������������������������������������  579 Infantile Hemangioma ���������������������������������������������������������������������������������������  579 Cystic Teratoma �������������������������������������������������������������������������������������������������  579 Lipoma ���������������������������������������������������������������������������������������������������������������  580 Inflammatory Myofibroblastic Tumor�����������������������������������������������������������������  580 Leiomyoma, Neurofibroma, and Schwannoma �������������������������������������������������  580 Malignant Pancreatic Tumors���������������������������������������������������������������������������������  580 Pancreatoblastoma ���������������������������������������������������������������������������������������������  580 Solid Pseudopapillary Tumor�����������������������������������������������������������������������������  582 Islet Cell Tumor �������������������������������������������������������������������������������������������������  582 Acinar Cell Carcinoma���������������������������������������������������������������������������������������  584 Ductal Adenocarcinoma�������������������������������������������������������������������������������������  585 Lymphoma ���������������������������������������������������������������������������������������������������������  585 Neuroblastoma ���������������������������������������������������������������������������������������������������  585 Primitive Neuroectodermal Tumor���������������������������������������������������������������������  586 Kaposiform Hemangioendothelioma �����������������������������������������������������������������  586 Rhabdomyosarcoma�������������������������������������������������������������������������������������������  587 Fibrosarcoma�������������������������������������������������������������������������������������������������������  587 Metastatic Disease ���������������������������������������������������������������������������������������������  587 Pancreatic Transplantation �����������������������������������������������������������������������������������������  588 Adrenal Glands�����������������������������������������������������������������������������������������������������������  588 Technique���������������������������������������������������������������������������������������������������������������  588 Patient Positioning ���������������������������������������������������������������������������������������������  588 Ultrasound Transducer Selection �����������������������������������������������������������������������  588 Imaging Approaches�������������������������������������������������������������������������������������������  588 Normal Development and Anatomy�����������������������������������������������������������������������  589 Normal Development�����������������������������������������������������������������������������������������  589 Normal Anatomy�������������������������������������������������������������������������������������������������  589 Anatomic Variants���������������������������������������������������������������������������������������������������  590 Discoid Adrenal Gland���������������������������������������������������������������������������������������  590 Congenital Anomalies���������������������������������������������������������������������������������������������  591 Congenital Adrenal Agenesis�����������������������������������������������������������������������������  591 Fusion Abnormalities ���������������������������������������������������������������������������������������������  591 Circumrenal Adrenal Gland �������������������������������������������������������������������������������  591 Horseshoe Adrenal Gland�����������������������������������������������������������������������������������  592 Adrenal Rests ���������������������������������������������������������������������������������������������������������  592 Adrenal Heterotopia�����������������������������������������������������������������������������������������������  593 Genetic Disorders���������������������������������������������������������������������������������������������������  593 Congenital Adrenal Hyperplasia�������������������������������������������������������������������������  593 Congenital Lipoid Adrenal Hyperplasia�������������������������������������������������������������  593 Wolman Disease�������������������������������������������������������������������������������������������������  594 Adrenal Cyst�����������������������������������������������������������������������������������������������������������  594 Idiopathic Adrenal Cyst �������������������������������������������������������������������������������������  594 Infection �����������������������������������������������������������������������������������������������������������������  595 Congenital Herpes Simplex Infection�����������������������������������������������������������������  595 Granulomatous Infection �����������������������������������������������������������������������������������  595 Xanthogranulomatous Adrenalitis ���������������������������������������������������������������������  595 Abscess���������������������������������������������������������������������������������������������������������������  595 Adrenal Hemorrhage�����������������������������������������������������������������������������������������������  596 Adrenocortical Tumors�������������������������������������������������������������������������������������������  597 Adrenocortical Adenoma and Carcinoma�����������������������������������������������������������  597 Neural Crest Tumors�����������������������������������������������������������������������������������������������  598 Ganglioneuroma�������������������������������������������������������������������������������������������������  598

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Ganglioneuroblastoma ���������������������������������������������������������������������������������������  599 Neuroblastoma ���������������������������������������������������������������������������������������������������  601 Pheochromocytoma�������������������������������������������������������������������������������������������������  606 Myelolipoma�����������������������������������������������������������������������������������������������������������  607 Hemangioma�����������������������������������������������������������������������������������������������������������  608 Teratoma�����������������������������������������������������������������������������������������������������������������  608 Leiomyoma�������������������������������������������������������������������������������������������������������������  609 Lymphoma �������������������������������������������������������������������������������������������������������������  609 Metastases���������������������������������������������������������������������������������������������������������������  609 Nonvascular Disorders of the Retroperitoneum���������������������������������������������������������  609 Technique���������������������������������������������������������������������������������������������������������������  609 Patient Positioning ���������������������������������������������������������������������������������������������  609 Ultrasound Transducer Selection �����������������������������������������������������������������������  609 Imaging Approaches�������������������������������������������������������������������������������������������  609 Normal Development and Anatomy�����������������������������������������������������������������������  609 Normal Development�����������������������������������������������������������������������������������������  609 Normal Anatomy�������������������������������������������������������������������������������������������������  610 Infection and Abscess���������������������������������������������������������������������������������������������  611 Hemorrhage�������������������������������������������������������������������������������������������������������������  613 Fibrosis�������������������������������������������������������������������������������������������������������������������  613 Extramedullary Hematopoiesis�������������������������������������������������������������������������������  614 Venous and Lymphatic Malformations�������������������������������������������������������������������  614 Lymphadenopathy���������������������������������������������������������������������������������������������������  615 Infection �������������������������������������������������������������������������������������������������������������  615 Lymphoma ���������������������������������������������������������������������������������������������������������  615 Metastatic Disease ���������������������������������������������������������������������������������������������  616 Benign Masses �������������������������������������������������������������������������������������������������������  617 Hemangioma�������������������������������������������������������������������������������������������������������  617 Mature Teratoma�������������������������������������������������������������������������������������������������  617 Retroperitoneal Lipoma and Lipoblastoma �����������������������������������������������������������  617 Neurofibroma and Schwannoma�����������������������������������������������������������������������������  617 Neural Crest Tumors: Ganglioneuroma, Ganglioneuroblastoma, and Neuroblastoma�������������������������������������������������������������������������������������������������  617 Malignant Tumors���������������������������������������������������������������������������������������������������  620 Rhabdomyosarcoma�������������������������������������������������������������������������������������������  620 Infantile Fibrosarcoma ���������������������������������������������������������������������������������������  620 Malignant Germ Cell Tumor/Immature Teratoma ���������������������������������������������  620 Smooth Muscle Tumors �����������������������������������������������������������������������������������������  621 Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma)���������  621 Ewing Sarcoma�������������������������������������������������������������������������������������������������������  621 Inflammatory Myofibroblastic Tumor���������������������������������������������������������������������  622 Kaposiform Hemangioendothelioma ���������������������������������������������������������������������  622 References�������������������������������������������������������������������������������������������������������������������  622 15 Male Genital Tract ����������������������������������������������������������������������������������������������������� 629 Judy H. Squires and Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  629 Scrotum�������������������������������������������������������������������������������������������������������������������  629 Technique���������������������������������������������������������������������������������������������������������������  629 Patient Positioning ���������������������������������������������������������������������������������������������  629 Ultrasound Transducer Selection �����������������������������������������������������������������������  629 Imaging Approaches�������������������������������������������������������������������������������������������  630 Normal Development and Anatomy�����������������������������������������������������������������������  630

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Normal Development�����������������������������������������������������������������������������������������  630 Normal Anatomy�������������������������������������������������������������������������������������������������  631 Scrotum�����������������������������������������������������������������������������������������������������������  631 Testes���������������������������������������������������������������������������������������������������������������  631 Epididymis �����������������������������������������������������������������������������������������������������  632 Spermatic Cord�����������������������������������������������������������������������������������������������  632 Testicular Appendages �����������������������������������������������������������������������������������  633 Blood Supply �������������������������������������������������������������������������������������������������  633 Anatomical Variants �����������������������������������������������������������������������������������������������  635 Testicular Appendages ���������������������������������������������������������������������������������������  635 Vessels�����������������������������������������������������������������������������������������������������������������  635 Congenital Anomalies���������������������������������������������������������������������������������������������  636 Testicular Agenesis���������������������������������������������������������������������������������������������  636 Cryptorchidism���������������������������������������������������������������������������������������������������  636 Anorchidism�������������������������������������������������������������������������������������������������������  636 Testicular Regression Syndrome�������������������������������������������������������������������������  636 Testicular Hypoplasia�����������������������������������������������������������������������������������������  637 Polyorchidism�����������������������������������������������������������������������������������������������������  637 Testicular Ectopia�����������������������������������������������������������������������������������������������  637 Cystic Dysplasia of the Rete Testis���������������������������������������������������������������������  638 Splenogonadal Fusion�����������������������������������������������������������������������������������������  638 Bell Clapper Deformity���������������������������������������������������������������������������������������  639 Acute Scrotal Pain���������������������������������������������������������������������������������������������������  639 Testicular Torsion�����������������������������������������������������������������������������������������������  639 Segmental Testicular Infarction �������������������������������������������������������������������������  641 Arterial Segmental Testicular Infarction���������������������������������������������������������  642 Venous Testicular Infarction���������������������������������������������������������������������������  642 Torsion of Testicular Appendages�����������������������������������������������������������������������  643 Inflammatory Disorders �������������������������������������������������������������������������������������  644 Acute Epididymitis and Epididymo-orchitis �������������������������������������������������  644 Isolated Orchitis ���������������������������������������������������������������������������������������������  644 Testicular Abscess�������������������������������������������������������������������������������������������  645 Epididymal Abscess ���������������������������������������������������������������������������������������  645 Scrotal Abscess�����������������������������������������������������������������������������������������������  645 Henoch-Schönlein Purpura�����������������������������������������������������������������������������  646 Idiopathic Scrotal Edema�������������������������������������������������������������������������������  646 Fournier Gangrene �����������������������������������������������������������������������������������������  649 Chronic Epididymitis ���������������������������������������������������������������������������������������������  649 Dancing Megasperm�����������������������������������������������������������������������������������������������  649 Scrotal and Spermatic Cord Fluid Collections�������������������������������������������������������  649 Scrotal Hydrocele�����������������������������������������������������������������������������������������������  649 Spermatic Cord Hydrocele���������������������������������������������������������������������������������  650 Abdominoscrotal Hydrocele�������������������������������������������������������������������������������  651 Scrotal Hematocele���������������������������������������������������������������������������������������������  651 Scrotal Lymphocele �������������������������������������������������������������������������������������������  652 Scrotal Calcification�������������������������������������������������������������������������������������������  652 Testicular Microlithiasis���������������������������������������������������������������������������������  652 Loose Bodies���������������������������������������������������������������������������������������������������  653 Meconium Peritonitis�������������������������������������������������������������������������������������  653 Trauma �������������������������������������������������������������������������������������������������������������������  653 Blunt Scrotal Trauma �����������������������������������������������������������������������������������������  653 Testicular Hematoma �������������������������������������������������������������������������������������  654 Testicular Fracture �����������������������������������������������������������������������������������������  655

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Testicular Rupture�������������������������������������������������������������������������������������������  655 Scrotal Hematocele�����������������������������������������������������������������������������������������  656 Penetrating Scrotal Trauma���������������������������������������������������������������������������������  656 Foreign Body �������������������������������������������������������������������������������������������������  656 Scrotal Urinoma ���������������������������������������������������������������������������������������������  657 Repetitive Scrotal Microtrauma ���������������������������������������������������������������������  657 Inguinal Hernia�������������������������������������������������������������������������������������������������������  657 Indirect Inguinal Hernia�������������������������������������������������������������������������������������  657 Direct Inguinal Hernia ���������������������������������������������������������������������������������������  658 Varicocele���������������������������������������������������������������������������������������������������������������  659 Intratesticular Varicocele�������������������������������������������������������������������������������������  660 Testicular Masses ���������������������������������������������������������������������������������������������������  660 Non-Neoplastic Lesions�������������������������������������������������������������������������������������  660 Adrenal Rests �������������������������������������������������������������������������������������������������  660 Leydig Cell Hyperplasia���������������������������������������������������������������������������������  661 Hamartoma�����������������������������������������������������������������������������������������������������  661 Simple Cyst�����������������������������������������������������������������������������������������������������  661 Sinus Histiocytosis (Rosai-Dorfman-Destombes Disease)�����������������������������  662 Primary Testicular Tumors�������������������������������������������������������������������������������������  662 Germ Cell Tumors�����������������������������������������������������������������������������������������������  662 Yolk Sac Tumor�����������������������������������������������������������������������������������������������  662 Teratoma���������������������������������������������������������������������������������������������������������  663 Seminoma�������������������������������������������������������������������������������������������������������  663 Gonadoblastoma���������������������������������������������������������������������������������������������  663 Embryonal Carcinoma �����������������������������������������������������������������������������������  663 Teratocarcinoma���������������������������������������������������������������������������������������������  664 Choriocarcinoma���������������������������������������������������������������������������������������������  664 Stromal Tumors���������������������������������������������������������������������������������������������������  664 Leydig Cell Tumor �����������������������������������������������������������������������������������������  665 Sertoli Cell Tumor�������������������������������������������������������������������������������������������  665 Granulosa Cell Tumor�������������������������������������������������������������������������������������  665 Other Testicular Tumors�������������������������������������������������������������������������������������  666 Epidermoid Cyst���������������������������������������������������������������������������������������������  666 Dermoid Cyst �������������������������������������������������������������������������������������������������  666 Fibroma�����������������������������������������������������������������������������������������������������������  666 Neurofibroma �������������������������������������������������������������������������������������������������  666 Lipoma �����������������������������������������������������������������������������������������������������������  667 Hemangioma���������������������������������������������������������������������������������������������������  667 Leiomyoma�����������������������������������������������������������������������������������������������������  668 Adenomatoid Tumor���������������������������������������������������������������������������������������  668 Follicular Lymphoma�������������������������������������������������������������������������������������  668 Secondary Testicular Tumors���������������������������������������������������������������������������������  668 Leukemia and Lymphoma�����������������������������������������������������������������������������������  668 Neuroblastoma ���������������������������������������������������������������������������������������������������  668 Wilms’ Tumor�����������������������������������������������������������������������������������������������������  669 Langerhans Cell Histiocytosis ���������������������������������������������������������������������������  669 Carcinoid Tumor�������������������������������������������������������������������������������������������������  669 Rhabdomyosarcoma�������������������������������������������������������������������������������������������  669 Retinoblastoma���������������������������������������������������������������������������������������������������  669 Paratesticular Masses ���������������������������������������������������������������������������������������������  669 Non-Neoplastic Lesions�������������������������������������������������������������������������������������  669 Spermatocele���������������������������������������������������������������������������������������������������  669 Epididymal Cyst���������������������������������������������������������������������������������������������  669

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Fibrous Pseudotumor �������������������������������������������������������������������������������������  670 Fibrous Hamartoma of Infancy�����������������������������������������������������������������������  670 Juvenile Xanthogranuloma�����������������������������������������������������������������������������  670 Spermatic Granuloma�������������������������������������������������������������������������������������  670 Cystic Dysplasia of Epididymis���������������������������������������������������������������������  670 Ectopic Adrenal Rest���������������������������������������������������������������������������������������  670 Vascular Anomalies���������������������������������������������������������������������������������������������  670 Lymphatic Malformation �������������������������������������������������������������������������������  670 Venous Malformation�������������������������������������������������������������������������������������  671 Arteriovenous Malformation���������������������������������������������������������������������������  671 Benign Tumors���������������������������������������������������������������������������������������������������  671 Lipoma �����������������������������������������������������������������������������������������������������������  671 Adenomatoid Tumor���������������������������������������������������������������������������������������  672 Leiomyoma�����������������������������������������������������������������������������������������������������  672 Dermoid ���������������������������������������������������������������������������������������������������������  672 Neurofibroma �������������������������������������������������������������������������������������������������  672 Papillary Cystadenoma�����������������������������������������������������������������������������������  672 Malignant Tumors�����������������������������������������������������������������������������������������������  673 Primary Tumors ���������������������������������������������������������������������������������������������  673 Secondary Tumors �����������������������������������������������������������������������������������������  673 Prostate and Seminal Vesicles�������������������������������������������������������������������������������������  674 Introduction�������������������������������������������������������������������������������������������������������������  674 Technique���������������������������������������������������������������������������������������������������������������  674 Patient Positioning ���������������������������������������������������������������������������������������������  674 Ultrasound Transducer Selection �����������������������������������������������������������������������  674 Imaging Approaches�������������������������������������������������������������������������������������������  674 Normal Development and Anatomy�����������������������������������������������������������������������  674 Normal Development�����������������������������������������������������������������������������������������  674 Normal Anatomy�������������������������������������������������������������������������������������������������  674 Prostate Gland�������������������������������������������������������������������������������������������������  674 Seminal Vesicles���������������������������������������������������������������������������������������������  675 Congenital Anomalies���������������������������������������������������������������������������������������������  675 Enlarged Prostatic Utricle and Prostatic Utricle Cyst�����������������������������������������  675 Müllerian Duct Cyst�������������������������������������������������������������������������������������������  675 Seminal Vesicle Cyst�������������������������������������������������������������������������������������������  675 Seminal Vesicle Agenesis or Hypoplasia �����������������������������������������������������������  677 Inflammatory Disorders �����������������������������������������������������������������������������������������  678 Prostatitis������������������������������������������������������������������������������������������������������������  678 Prostatic Abscess���������������������������������������������������������������������������������������������  678 Seminal Vesiculitis �����������������������������������������������������������������������������������������  678 Tumors of the Prostate and Seminal Vesicle�������������������������������������������������������  678 Rhabdomyosarcoma���������������������������������������������������������������������������������������  678 Leukemia���������������������������������������������������������������������������������������������������������  678 Seminal Vesicle Tumors���������������������������������������������������������������������������������  678 References�������������������������������������������������������������������������������������������������������������������  678 16 Female Genital Tract ������������������������������������������������������������������������������������������������� 683 Erica L. Riedesel and Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  683 Technique: Patient Positioning, Transducer Selection, and Imaging Approaches�����  683 Transabdominal Ultrasound�����������������������������������������������������������������������������������  683 Transvaginal Ultrasound�����������������������������������������������������������������������������������������  684 Three-Dimensional Ultrasound�������������������������������������������������������������������������������  686

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Transperineal Ultrasound���������������������������������������������������������������������������������������  686 Normal Development and Anatomy���������������������������������������������������������������������������  686 Normal Development���������������������������������������������������������������������������������������������  686 Gonads and Reproductive Tract�����������������������������������������������������������������������������  686 External Genitalia���������������������������������������������������������������������������������������������������  688 Normal Anatomy�����������������������������������������������������������������������������������������������������  688 Ovary and Fallopian Tube���������������������������������������������������������������������������������������  688 Uterus and Cervix���������������������������������������������������������������������������������������������������  689 Vagina���������������������������������������������������������������������������������������������������������������������  689 Ovarian and Uterine Changes Associated with the Menstrual Cycle���������������������  690 Anatomic Variants�������������������������������������������������������������������������������������������������������  692 Arcuate Uterus �������������������������������������������������������������������������������������������������������  692 Congenital Anomalies�������������������������������������������������������������������������������������������������  692 Müllerian Duct Anomalies�������������������������������������������������������������������������������������  692 Müllerian Agenesis���������������������������������������������������������������������������������������������  692 Uterine Agenesis���������������������������������������������������������������������������������������������  693 Mayer-Rokitansky-Küster-Hauser Syndrome (MRKH)���������������������������������  693 Disorders of Lateral Fusion �������������������������������������������������������������������������������  694 Septate Uterus�������������������������������������������������������������������������������������������������  694 Bicornuate Uterus�������������������������������������������������������������������������������������������  694 Uterus Didelphys �������������������������������������������������������������������������������������������  696 Unicornuate Uterus�����������������������������������������������������������������������������������������  696 Disorders of Vertical Fusion�������������������������������������������������������������������������������  696 Imperforate Hymen�����������������������������������������������������������������������������������������  696 Transverse Vaginal Septum�����������������������������������������������������������������������������  698 Atresia of Cervix or Vagina����������������������������������������������������������������������������  698 OHVIRA Syndrome���������������������������������������������������������������������������������������  700 Disorders of Sex Development�����������������������������������������������������������������������������������  701 Sex Chromosome Disorders of Sex Development�������������������������������������������������  701 45,X (Turner Syndrome)�������������������������������������������������������������������������������������  701 46,XX Disorders of Sex Development���������������������������������������������������������������  701 Congenital Adrenal Hyperplasia�����������������������������������������������������������������������������  702 Cloacal Malformation���������������������������������������������������������������������������������������������  702 Adnexal Masses ���������������������������������������������������������������������������������������������������������  703 Ovarian Masses�������������������������������������������������������������������������������������������������������  703 Functional Cyst���������������������������������������������������������������������������������������������������  703 Endometrioma�����������������������������������������������������������������������������������������������������  705 Germ Cell Tumors�����������������������������������������������������������������������������������������������  705 Teratoma���������������������������������������������������������������������������������������������������������  706 Gonadoblastoma���������������������������������������������������������������������������������������������  706 Dysgerminoma�����������������������������������������������������������������������������������������������  707 Yolk Sac Tumor�����������������������������������������������������������������������������������������������  708 Choriocarcinoma���������������������������������������������������������������������������������������������  708 Mixed Germ Cell Tumor���������������������������������������������������������������������������������  709 Epithelial Tumors�����������������������������������������������������������������������������������������������  709 Cystadenoma���������������������������������������������������������������������������������������������������  709 Borderline Epithelial Tumor and Cystadenocarcinoma���������������������������������  710 Stromal Tumors���������������������������������������������������������������������������������������������������  710 Thecoma-Fibroma�������������������������������������������������������������������������������������������  710 Juvenile Granulosa Cell Tumor����������������������������������������������������������������������  710 Sertoli-Leydig Cell Tumor �����������������������������������������������������������������������������  711 Secondary Tumors ���������������������������������������������������������������������������������������������  711 Paraovarian Cyst�����������������������������������������������������������������������������������������������������  711

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Peritoneal Inclusion Cyst ���������������������������������������������������������������������������������������  712 Adnexal Torsion �����������������������������������������������������������������������������������������������������  713 Isolated Tubal Torsion�����������������������������������������������������������������������������������������  713 Massive Edema of the Ovary �����������������������������������������������������������������������������  714 Ectopic Pregnancy�������������������������������������������������������������������������������������������������������  715 Pelvic Inflammatory Disease �������������������������������������������������������������������������������������  716 Uterine Masses�����������������������������������������������������������������������������������������������������������  717 Benign Masses �������������������������������������������������������������������������������������������������������  717 Leiomyoma (Fibroid)�����������������������������������������������������������������������������������������  717 Adenomyosis�������������������������������������������������������������������������������������������������������  718 Malignant Tumors���������������������������������������������������������������������������������������������������  719 Lymphoma ���������������������������������������������������������������������������������������������������������  719 Cervical Masses ���������������������������������������������������������������������������������������������������������  719 Benign Tumors�������������������������������������������������������������������������������������������������������  719 Nabothian Cyst���������������������������������������������������������������������������������������������������  719 Malignant Tumors���������������������������������������������������������������������������������������������������  720 Rhabdomyosarcoma�������������������������������������������������������������������������������������������  720 Vaginal Masses�����������������������������������������������������������������������������������������������������������  720 Benign Masses �������������������������������������������������������������������������������������������������������  720 Gartner Duct Cyst�����������������������������������������������������������������������������������������������  720 Bartholin Cyst�����������������������������������������������������������������������������������������������������  721 Inclusion Cyst�����������������������������������������������������������������������������������������������������  721 Paraurethral Duct Cyst���������������������������������������������������������������������������������������  721 Fibroepithelial Polyp�������������������������������������������������������������������������������������������  722 Müllerian Papilloma�������������������������������������������������������������������������������������������  722 Malignant Tumors���������������������������������������������������������������������������������������������������  722 Rhabdomyosarcoma�������������������������������������������������������������������������������������������  722 Clear-Cell Adenocarcinoma and Endodermal Sinus Tumor�������������������������������  722 Vaginal Foreign Body�������������������������������������������������������������������������������������������������  723 Pubertal Disorders�������������������������������������������������������������������������������������������������������  723 Precocious Puberty�������������������������������������������������������������������������������������������������  723 Amenorrhea�������������������������������������������������������������������������������������������������������������  724 Polycystic Ovary Syndrome�������������������������������������������������������������������������������  724 Canal of Nuck Disorders���������������������������������������������������������������������������������������������  725 Hydrocele of the Canal of Nuck�����������������������������������������������������������������������������  725 Hernia of the Canal of Nuck�����������������������������������������������������������������������������������  726 References�������������������������������������������������������������������������������������������������������������������  726 17 Urinary Tract��������������������������������������������������������������������������������������������������������������� 729 Ghadir H. Kassab, Ian Robinson, Roisin Hayes, Harriet J. Paltiel, D. Gregory Bates, Harris L. Cohen, Richard A. Barth, and Gabrielle Christina Maria Colleran Introduction�����������������������������������������������������������������������������������������������������������������  730 Technique�������������������������������������������������������������������������������������������������������������������  730 Patient Positioning �������������������������������������������������������������������������������������������������  730 Ultrasound Transducer Selection ���������������������������������������������������������������������������  730 Imaging Approaches�����������������������������������������������������������������������������������������������  730 Grayscale Imaging �������������������������������������������������������������������������������������������������  730 Doppler Ultrasound�������������������������������������������������������������������������������������������������  730 Contrast-Enhanced Ultrasound�������������������������������������������������������������������������������  730 Elastography�����������������������������������������������������������������������������������������������������������  731 Normal Development and Anatomy���������������������������������������������������������������������������  731 Normal Development���������������������������������������������������������������������������������������������  731 Normal Anatomy�����������������������������������������������������������������������������������������������������  734

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Kidney�����������������������������������������������������������������������������������������������������������������  734 Infant���������������������������������������������������������������������������������������������������������������  734 Older Child and Adolescent ���������������������������������������������������������������������������  734 Anatomic Variants�������������������������������������������������������������������������������������������  734 Ureter �����������������������������������������������������������������������������������������������������������������  738 Normal Anatomy���������������������������������������������������������������������������������������������  738 Ureteral Jets ���������������������������������������������������������������������������������������������������  738 Bladder���������������������������������������������������������������������������������������������������������������  738 Normal Anatomy���������������������������������������������������������������������������������������������  738 Anatomic Variants�������������������������������������������������������������������������������������������  740 Urethra ���������������������������������������������������������������������������������������������������������������  740 Normal Anatomy���������������������������������������������������������������������������������������������  740 Congenital Anomalies�������������������������������������������������������������������������������������������������  741 Anomalies of Renal Number, Position, Fusion, and Growth���������������������������������  741 Renal Agenesis���������������������������������������������������������������������������������������������������  741 Renal Duplication�����������������������������������������������������������������������������������������������  742 Supernumerary Kidney���������������������������������������������������������������������������������������  743 Renal Ectopia �����������������������������������������������������������������������������������������������������  744 Simple Ectopia �����������������������������������������������������������������������������������������������  744 Crossed Renal Ectopia ���������������������������������������������������������������������������������������  744 Horseshoe Kidney�����������������������������������������������������������������������������������������������  745 Pancake Kidney���������������������������������������������������������������������������������������������������  745 Renal Hypoplasia �����������������������������������������������������������������������������������������������  746 Anomalies of the Renal Collecting System and Ureter �����������������������������������������  746 Classification of Prenatal and Postnatal Hydronephrosis�����������������������������������  746 Ureteropelvic Junction Obstruction �������������������������������������������������������������������  746 Ureteropelvic Junction Obstruction Caused by Crossing Vessel �������������������  748 Congenital Megacalyces�������������������������������������������������������������������������������������  748 Congenital Infundibulopelvic Stenosis���������������������������������������������������������������  748 Calyceal Diverticulum ���������������������������������������������������������������������������������������  750 Congenital Ureterovesical Junction Obstruction �����������������������������������������������  751 Ectopic Ureter�����������������������������������������������������������������������������������������������������  752 Ectopic Ureterocele���������������������������������������������������������������������������������������������  752 Retrocaval Ureter �����������������������������������������������������������������������������������������������  752 Vesicoureteral Reflux �����������������������������������������������������������������������������������������  752 Contrast-Enhanced Ultrasound Diagnosis of Vesicoureteral Reflux �������������  755 Imaging of Endoscopically Placed Bulking Agents���������������������������������������  755 Anomalies of the Bladder���������������������������������������������������������������������������������������  755 Urachal Anomalies���������������������������������������������������������������������������������������������  755 Patent Urachus �����������������������������������������������������������������������������������������������  757 Vesicourachal Diverticulum���������������������������������������������������������������������������  757 Umbilicourachal Sinus�����������������������������������������������������������������������������������  758 Urachal Cyst���������������������������������������������������������������������������������������������������  758 Bladder Diverticula���������������������������������������������������������������������������������������������  758 Bladder Exstrophy ���������������������������������������������������������������������������������������������  758 Cloacal Exstrophy�����������������������������������������������������������������������������������������������  759 Cloacal Malformation�����������������������������������������������������������������������������������������  760 Bladder Duplication �������������������������������������������������������������������������������������������  761 Bladder Agenesis �����������������������������������������������������������������������������������������������  762 Prune-Belly Syndrome���������������������������������������������������������������������������������������  762 Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome���������������������������  763 Anomalies of the Urethra���������������������������������������������������������������������������������������  764 Posterior Urethral Valves �����������������������������������������������������������������������������������  764

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Anterior Urethral Valves�������������������������������������������������������������������������������������  765 Urethral Duplication�������������������������������������������������������������������������������������������  766 Acquired Ureteral Obstruction�����������������������������������������������������������������������������������  766 Intraluminal Obstruction�����������������������������������������������������������������������������������������  766 Extrinsic Compression �������������������������������������������������������������������������������������������  767 Neurogenic Bladder ���������������������������������������������������������������������������������������������������  767 Urinary Tract Infection�����������������������������������������������������������������������������������������������  768 Acute Pyelonephritis�����������������������������������������������������������������������������������������������  768 Renal Abscess���������������������������������������������������������������������������������������������������������  769 Pyonephrosis�����������������������������������������������������������������������������������������������������������  770 Fungal Infection �����������������������������������������������������������������������������������������������������  770 Parasitic Infection���������������������������������������������������������������������������������������������������  772 Opportunistic Infection�������������������������������������������������������������������������������������������  772 Chronic Pyelonephritis�������������������������������������������������������������������������������������������  772 Xanthogranulomatous Pyelonephritis���������������������������������������������������������������������  773 Cystitis �������������������������������������������������������������������������������������������������������������������  773 Renal Cystic Disease�����������������������������������������������������������������������������������������������  774 Autosomal Recessive Polycystic Kidney Disease ���������������������������������������������  775 Autosomal Dominant Polycystic Kidney Disease ���������������������������������������������  775 Cystic Renal Dysplasia���������������������������������������������������������������������������������������  776 Nephronophthisis �����������������������������������������������������������������������������������������������  776 Medullary Cystic Disease�����������������������������������������������������������������������������������  777 Glomerulocystic Kidney Disease�����������������������������������������������������������������������  777 Syndromes with Renal Cysts ���������������������������������������������������������������������������������  778 Tuberous Sclerosis ���������������������������������������������������������������������������������������������  778 Von Hippel-Lindau Disease �������������������������������������������������������������������������������  778 Acquired Cystic Kidney Disease �������������������������������������������������������������������������������  779 Renal Vascular Disease�����������������������������������������������������������������������������������������������  779 Renal Artery Stenosis���������������������������������������������������������������������������������������������  779 Renal Artery Thrombosis ���������������������������������������������������������������������������������������  781 Renal Artery Pseudoaneurysm�������������������������������������������������������������������������������  781 Renal Vein Thrombosis�������������������������������������������������������������������������������������������  781 Arteriovenous Fistula���������������������������������������������������������������������������������������������  783 Medical Renal Disease�����������������������������������������������������������������������������������������������  784 Acute Kidney Injury�����������������������������������������������������������������������������������������������  784 Chronic Kidney Disease�����������������������������������������������������������������������������������������  786 Renal Transplantation�������������������������������������������������������������������������������������������������  786 Surgical Technique�������������������������������������������������������������������������������������������������  787 Normal Posttransplant Imaging �����������������������������������������������������������������������������  788 Complications���������������������������������������������������������������������������������������������������������  788 Vascular Complications �������������������������������������������������������������������������������������  788 Renal Artery Thrombosis �������������������������������������������������������������������������������  788 Renal Artery Stenosis�������������������������������������������������������������������������������������  789 Renal Vein Thrombosis�����������������������������������������������������������������������������������  789 Arteriovenous Fistula�������������������������������������������������������������������������������������  789 Pseudoaneurysm���������������������������������������������������������������������������������������������  789 Parenchymal Complications�������������������������������������������������������������������������������  791 Acute Tubular Necrosis�����������������������������������������������������������������������������������  791 Rejection���������������������������������������������������������������������������������������������������������  792 Drug Toxicity �������������������������������������������������������������������������������������������������  792 Urologic Complications �������������������������������������������������������������������������������������  793 Transplant Urine Leak �����������������������������������������������������������������������������������  793 Transplant Ureteral Obstruction���������������������������������������������������������������������  794

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Transplant Vesicoureteral Reflux �������������������������������������������������������������������  794 Transplant Pyelonephritis�������������������������������������������������������������������������������  795 Perinephric Fluid Collections�����������������������������������������������������������������������������  796 Transplant Lymphocele�����������������������������������������������������������������������������������  796 Transplant Urinoma ���������������������������������������������������������������������������������������  796 Transplant Hematoma and Seroma�����������������������������������������������������������������  796 Transplant Abscess�����������������������������������������������������������������������������������������  796 Posttransplant Tumors�����������������������������������������������������������������������������������������  797 Urinary Tract Calcification�����������������������������������������������������������������������������������������  798 Renal Cortical Calcification�����������������������������������������������������������������������������������  798 Medullary Nephrocalcinosis�����������������������������������������������������������������������������������  798 Renal Vein Thrombosis Calcifications �������������������������������������������������������������������  799 Dystrophic Calcification�����������������������������������������������������������������������������������������  799 Urinary Stasis���������������������������������������������������������������������������������������������������������  799 Urolithiasis�������������������������������������������������������������������������������������������������������������  799 Risk Factors �������������������������������������������������������������������������������������������������������  800 Kidney Stone Risk Factors�����������������������������������������������������������������������������  800 Bladder Stone Risk Factors�����������������������������������������������������������������������������  800 Trauma �����������������������������������������������������������������������������������������������������������������������  801 Renal Trauma ���������������������������������������������������������������������������������������������������������  801 Contrast-Enhanced Ultrasound Diagnosis of Trauma�����������������������������������������  801 Bladder Trauma�������������������������������������������������������������������������������������������������������  802 Tumors and Malformations�����������������������������������������������������������������������������������������  803 Renal Tumors ���������������������������������������������������������������������������������������������������������  803 Benign Renal Tumors�����������������������������������������������������������������������������������������  803 Mesoblastic Nephroma�����������������������������������������������������������������������������������  803 Angiomyolipoma �������������������������������������������������������������������������������������������  804 Multilocular Cystic Renal Tumor�������������������������������������������������������������������  805 Metanephric Adenoma �����������������������������������������������������������������������������������  805 Inflammatory Myofibroblastic Tumor�������������������������������������������������������������  806 Ossifying Renal Tumor of Infancy�����������������������������������������������������������������  806 Primary Malignant Renal Tumors�����������������������������������������������������������������������  806 Wilms’ Tumor�������������������������������������������������������������������������������������������������  806 Renal Cell Carcinoma�������������������������������������������������������������������������������������  810 Rhabdoid Tumor���������������������������������������������������������������������������������������������  811 Clear Cell Sarcoma�����������������������������������������������������������������������������������������  811 Renal Medullary Carcinoma���������������������������������������������������������������������������  812 Primitive Neuroectodermal Tumor�����������������������������������������������������������������  812 Other Rare Primary Malignant Renal Tumors �����������������������������������������������  813 Secondary Malignant Renal Tumors�������������������������������������������������������������������  813 Leukemia���������������������������������������������������������������������������������������������������������  813 Lymphoma �����������������������������������������������������������������������������������������������������  813 Metastases�������������������������������������������������������������������������������������������������������  814 Primary Ureteral Tumors ���������������������������������������������������������������������������������������  815 Fibroepithelial Polyp�������������������������������������������������������������������������������������������  815 Urothelial Tumor�������������������������������������������������������������������������������������������������  816 Secondary Ureteral Tumors �����������������������������������������������������������������������������������  816 Extension of Wilms’ Tumor���������������������������������������������������������������������������  816 Bladder Malformations and Tumors�����������������������������������������������������������������������  816 Vascular Malformations �������������������������������������������������������������������������������������  816 Lymphatic Malformation �������������������������������������������������������������������������������  816 Venous Malformation�������������������������������������������������������������������������������������  816 Benign Bladder Tumors �������������������������������������������������������������������������������������  818

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Urothelial Papilloma���������������������������������������������������������������������������������������  818 Papillary Urothelial Neoplasm of Low Malignant Potential �������������������������  818 Fibroepithelial Polyp���������������������������������������������������������������������������������������  818 Inflammatory Myofibroblastic Tumor�������������������������������������������������������������  818 Leiomyoma�����������������������������������������������������������������������������������������������������  819 Neurofibroma �������������������������������������������������������������������������������������������������  819 Paraganglioma�������������������������������������������������������������������������������������������������  819 Nephrogenic Adenoma�����������������������������������������������������������������������������������  820 Malignant Bladder Tumors���������������������������������������������������������������������������������  821 Rhabdomyosarcoma���������������������������������������������������������������������������������������  821 Transitional Cell Carcinoma���������������������������������������������������������������������������  822 Leiomyosarcoma���������������������������������������������������������������������������������������������  823 Angiosarcoma�������������������������������������������������������������������������������������������������  823 Urethral Tumors �����������������������������������������������������������������������������������������������������  824 Urethral Polyp�����������������������������������������������������������������������������������������������������  824 Urinary Diversion�������������������������������������������������������������������������������������������������������  824 References�������������������������������������������������������������������������������������������������������������������  825 18 Musculoskeletal System��������������������������������������������������������������������������������������������� 835 Delma Y. Jarrett Introduction�����������������������������������������������������������������������������������������������������������������  835 Technique�������������������������������������������������������������������������������������������������������������������  836 Patient Positioning �������������������������������������������������������������������������������������������������  836 Ultrasound Transducer Selection ���������������������������������������������������������������������������  836 Imaging Approaches�����������������������������������������������������������������������������������������������  836 Normal Development�������������������������������������������������������������������������������������������������  837 Soft Tissues�����������������������������������������������������������������������������������������������������������������  837 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  837 Skin and Subcutaneous Tissues �������������������������������������������������������������������������  837 Muscles���������������������������������������������������������������������������������������������������������������  837 Tendons���������������������������������������������������������������������������������������������������������������  838 Infectious/Inflammatory Disorders�������������������������������������������������������������������������  838 Cellulitis�������������������������������������������������������������������������������������������������������������  838 Pyomyositis���������������������������������������������������������������������������������������������������������  839 Soft Tissue Abscess���������������������������������������������������������������������������������������������  839 Trauma �������������������������������������������������������������������������������������������������������������������  840 Fat Necrosis �������������������������������������������������������������������������������������������������������  840 Foreign Bodies ���������������������������������������������������������������������������������������������������  841 Muscle Tears and Intramuscular Hematomas�����������������������������������������������������  841 Myositis Ossificans���������������������������������������������������������������������������������������������  843 Muscle Hernia�����������������������������������������������������������������������������������������������������  843 Tendinopathy and Tendon Tears�������������������������������������������������������������������������  844 Tumors �������������������������������������������������������������������������������������������������������������������  844 Subcutaneous Granuloma Annulare�������������������������������������������������������������������  845 Pilomatricoma�����������������������������������������������������������������������������������������������������  845 Lipoma ���������������������������������������������������������������������������������������������������������������  846 Lipoblastoma�������������������������������������������������������������������������������������������������������  846 Bones/Cartilage�����������������������������������������������������������������������������������������������������������  847 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  847 Congenital/Developmental Abnormalities�������������������������������������������������������������  849 Congenital Rib Anomalies ���������������������������������������������������������������������������������  849 Infectious/Inflammatory Disorders�������������������������������������������������������������������������  850 Osteomyelitis �����������������������������������������������������������������������������������������������������  850

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Trauma �������������������������������������������������������������������������������������������������������������������  851 Epiphyseal Separation�����������������������������������������������������������������������������������������  851 Classic Metaphyseal Lesion�������������������������������������������������������������������������������  852 Tumors �������������������������������������������������������������������������������������������������������������������  853 Osteochondroma�������������������������������������������������������������������������������������������������  853 Joints���������������������������������������������������������������������������������������������������������������������������  854 Infectious/Inflammatory Disorders�������������������������������������������������������������������������  854 Septic Arthritis ���������������������������������������������������������������������������������������������������  854 Juvenile Idiopathic Arthritis�������������������������������������������������������������������������������  854 Hemarthrosis�����������������������������������������������������������������������������������������������������������  855 Shoulder ���������������������������������������������������������������������������������������������������������������������  856 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  856 Normal Anatomy�������������������������������������������������������������������������������������������������  856 Patient Positioning ���������������������������������������������������������������������������������������������  856 Imaging Approaches�������������������������������������������������������������������������������������������  856 Congenital/Developmental Abnormalities�������������������������������������������������������������  858 Glenohumeral Dysplasia�������������������������������������������������������������������������������������  858 Elbow �������������������������������������������������������������������������������������������������������������������������  860 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  860 Normal Anatomy�������������������������������������������������������������������������������������������������  860 Patient Positioning ���������������������������������������������������������������������������������������������  860 Imaging Approaches�������������������������������������������������������������������������������������������  860 Anterior Approach �����������������������������������������������������������������������������������������  860 Posterior Approach�����������������������������������������������������������������������������������������  861 Medial Approach���������������������������������������������������������������������������������������������  861 Lateral Approach���������������������������������������������������������������������������������������������  861 Annular Ligament���������������������������������������������������������������������������������������������������  862 Elbow Fat Pads and Joint Effusion�������������������������������������������������������������������������  862 Congenital/Developmental Abnormalities�������������������������������������������������������������  863 Congenital Radial Head Dislocation�������������������������������������������������������������������  863 Trauma �������������������������������������������������������������������������������������������������������������������  864 Distal Humeral Epiphyseal Separation���������������������������������������������������������������  864 Apophyseal Avulsion �����������������������������������������������������������������������������������������  864 Pulled Elbow�������������������������������������������������������������������������������������������������������  866 Wrist and Hand�����������������������������������������������������������������������������������������������������������  866 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  866 Normal Anatomy�������������������������������������������������������������������������������������������������  866 Patient Positioning ���������������������������������������������������������������������������������������������  867 Imaging Approaches�������������������������������������������������������������������������������������������  867 Ganglia�������������������������������������������������������������������������������������������������������������������  868 Congenital/Developmental Abnormalities�������������������������������������������������������������  869 Carpal Boss���������������������������������������������������������������������������������������������������������  869 Tumors �������������������������������������������������������������������������������������������������������������������  869 Giant Cell Tumor of the Tendon Sheath�������������������������������������������������������������  869 Hip�������������������������������������������������������������������������������������������������������������������������������  869 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  869 Normal Anatomy�������������������������������������������������������������������������������������������������  869 Patient Positioning ���������������������������������������������������������������������������������������������  870 Imaging Approaches�������������������������������������������������������������������������������������������  871 Neonates and Infants for Hip Dysplasia���������������������������������������������������������  871 Assessment for Synovitis and Effusion ���������������������������������������������������������  872 Congenital/Developmental Abnormalities�������������������������������������������������������������  872 Developmental Dysplasia of the Hip �����������������������������������������������������������������  872

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Imaging�����������������������������������������������������������������������������������������������������������  873 Treatment �������������������������������������������������������������������������������������������������������  875 Proximal Focal Femoral Deficiency�������������������������������������������������������������������  876 Infectious/Inflammatory Disorders�������������������������������������������������������������������������  877 Transient Synovitis and Septic Arthritis�������������������������������������������������������������  877 Trauma �������������������������������������������������������������������������������������������������������������������  877 Slipped Capital Femoral Epiphysis���������������������������������������������������������������������  877 Knee ���������������������������������������������������������������������������������������������������������������������������  878 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  878 Normal Anatomy�������������������������������������������������������������������������������������������������  878 Patient Positioning ���������������������������������������������������������������������������������������������  879 Imaging Approaches�������������������������������������������������������������������������������������������  879 Patellofemoral Joint ���������������������������������������������������������������������������������������  879 Extensor Mechanism���������������������������������������������������������������������������������������  879 Tibial Tubercle �����������������������������������������������������������������������������������������������  880 Menisci�����������������������������������������������������������������������������������������������������������  880 Joint Effusion and Baker Cyst ���������������������������������������������������������������������������  881 Joint Effusion �������������������������������������������������������������������������������������������������  881 Baker Cyst�������������������������������������������������������������������������������������������������������  881 Congenital/Developmental Abnormalities�������������������������������������������������������������  882 Tibial Hemimelia �����������������������������������������������������������������������������������������������  882 Congenital Knee Dislocation �����������������������������������������������������������������������������  882 Congenital Patellar Dislocation �������������������������������������������������������������������������  883 Bipartite/Multipartite Patella �����������������������������������������������������������������������������  884 Discoid Meniscus and Meniscal Tears���������������������������������������������������������������  885 Trauma �������������������������������������������������������������������������������������������������������������������  886 Osgood-Schlatter Disease�����������������������������������������������������������������������������������  886 Sinding-Larsen-Johansson Syndrome�����������������������������������������������������������������  886 Ankle and Hindfoot�����������������������������������������������������������������������������������������������������  887 Normal Anatomy and Imaging Approaches�����������������������������������������������������������  887 Normal Anatomy�������������������������������������������������������������������������������������������������  887 Patient Positioning ���������������������������������������������������������������������������������������������  887 Imaging Approaches�������������������������������������������������������������������������������������������  888 Joint Effusion �������������������������������������������������������������������������������������������������  888 Calcaneal Apophysis���������������������������������������������������������������������������������������  889 Trauma �����������������������������������������������������������������������������������������������������������������������  889 Apophyseal Avulsion Injuries���������������������������������������������������������������������������������  889 Vascular Anomalies�����������������������������������������������������������������������������������������������������  889 Vascular Tumors�����������������������������������������������������������������������������������������������������  889 Infantile Hemangioma ���������������������������������������������������������������������������������������  889 Congenital Hemangioma �����������������������������������������������������������������������������������  890 Kaposiform Hemangioendothelioma �����������������������������������������������������������������  891 Vascular Malformations �����������������������������������������������������������������������������������������  891 Venous Malformation�����������������������������������������������������������������������������������������  892 Lymphatic Malformation �����������������������������������������������������������������������������������  892 Arteriovenous Malformation and Arteriovenous Fistula �����������������������������������  893 References�������������������������������������������������������������������������������������������������������������������  894 19 Vascular Imaging ������������������������������������������������������������������������������������������������������� 899 Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  899 Neck Vessels���������������������������������������������������������������������������������������������������������������  899 Technique���������������������������������������������������������������������������������������������������������������  899

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Patient Positioning ���������������������������������������������������������������������������������������������  899 Ultrasound Transducer Selection �����������������������������������������������������������������������  899 Imaging Approaches���������������������������������������������������������������������������������������  900 Carotid Artery���������������������������������������������������������������������������������������������������������  901 Normal Development and Anatomy�������������������������������������������������������������������  901 Normal Development�������������������������������������������������������������������������������������  901 Normal Anatomy���������������������������������������������������������������������������������������������  902 Anatomic Variants�����������������������������������������������������������������������������������������������  902 Thrombosis and Stenosis �����������������������������������������������������������������������������������  902 Aneurysm�����������������������������������������������������������������������������������������������������������  905 Dissection�����������������������������������������������������������������������������������������������������������  905 Internal Jugular Vein�����������������������������������������������������������������������������������������������  906 Normal Development and Anatomy�������������������������������������������������������������������  906 Normal Development�������������������������������������������������������������������������������������  906 Normal Anatomy���������������������������������������������������������������������������������������������  906 Anatomic Variants�����������������������������������������������������������������������������������������������  906 Congenital Anomalies�����������������������������������������������������������������������������������������  906 Jugular Vein Phlebectasia�������������������������������������������������������������������������������  906 Thrombosis���������������������������������������������������������������������������������������������������������  906 Stenosis���������������������������������������������������������������������������������������������������������������  908 Aneurysm�����������������������������������������������������������������������������������������������������������  908 Extremity Arteries�������������������������������������������������������������������������������������������������������  909 Technique���������������������������������������������������������������������������������������������������������������  909 Patient Positioning ���������������������������������������������������������������������������������������������  909 Ultrasound Transducer Selection �����������������������������������������������������������������������  910 Imaging Approaches�������������������������������������������������������������������������������������������  910 Normal Development and Anatomy�����������������������������������������������������������������������  913 Upper Extremity�������������������������������������������������������������������������������������������������  913 Normal Development�������������������������������������������������������������������������������������  913 Normal Anatomy���������������������������������������������������������������������������������������������  913 Lower Extremity�������������������������������������������������������������������������������������������������  913 Normal Development�������������������������������������������������������������������������������������  913 Normal Anatomy���������������������������������������������������������������������������������������������  913 Anatomic Variants���������������������������������������������������������������������������������������������������  914 Stenosis and Thrombosis ���������������������������������������������������������������������������������������  914 Aneurysm���������������������������������������������������������������������������������������������������������������  916 Pseudoaneurysm�����������������������������������������������������������������������������������������������������  916 Arteriovenous Fistula���������������������������������������������������������������������������������������������  916 Extremity Veins�����������������������������������������������������������������������������������������������������������  918 Technique���������������������������������������������������������������������������������������������������������������  918 Patient Positioning ���������������������������������������������������������������������������������������������  918 Ultrasound Transducer Selection �����������������������������������������������������������������������  918 Imaging Approaches�������������������������������������������������������������������������������������������  919 Normal Development and Anatomy�����������������������������������������������������������������������  922 Upper Extremity�������������������������������������������������������������������������������������������������  922 Normal Development�������������������������������������������������������������������������������������  922 Normal Anatomy���������������������������������������������������������������������������������������������  922 Lower Extremity�������������������������������������������������������������������������������������������������  922 Normal Development�������������������������������������������������������������������������������������  922 Normal Anatomy���������������������������������������������������������������������������������������������  922 Anatomic Variants���������������������������������������������������������������������������������������������������  923 Thrombosis�������������������������������������������������������������������������������������������������������������  923 Acute Deep Vein Thrombosis�����������������������������������������������������������������������������  923

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Chronic (Residual) Deep Vein Thrombosis �������������������������������������������������������  926 Retroperitoneal Vessels�����������������������������������������������������������������������������������������������  927 Technique���������������������������������������������������������������������������������������������������������������  927 Patient Positioning ���������������������������������������������������������������������������������������������  927 Ultrasound Transducer Selection �����������������������������������������������������������������������  927 Imaging Approaches�������������������������������������������������������������������������������������������  927 Aorta�����������������������������������������������������������������������������������������������������������������������  927 Normal Development and Anatomy�������������������������������������������������������������������  927 Normal Development�������������������������������������������������������������������������������������  927 Normal Anatomy���������������������������������������������������������������������������������������������  927 Thrombosis���������������������������������������������������������������������������������������������������������  927 Stenosis���������������������������������������������������������������������������������������������������������������  928 Aneurysm�����������������������������������������������������������������������������������������������������������  929 Dissection�����������������������������������������������������������������������������������������������������������  931 Inferior Vena Cava �������������������������������������������������������������������������������������������������  931 Normal Development and Anatomy�������������������������������������������������������������������  931 Normal Development�������������������������������������������������������������������������������������  931 Normal Anatomy���������������������������������������������������������������������������������������������  931 Congenital Anomalies�����������������������������������������������������������������������������������������  933 Interruption of the IVC with Azygos Continuation ���������������������������������������  933 Retrocaval Ureter �������������������������������������������������������������������������������������������  933 Duplicated IVC�����������������������������������������������������������������������������������������������  934 Left-Sided IVC�����������������������������������������������������������������������������������������������  934 Thrombosis���������������������������������������������������������������������������������������������������������  934 May-Thurner Syndrome���������������������������������������������������������������������������������  936 References�������������������������������������������������������������������������������������������������������������������  936 20 Breast��������������������������������������������������������������������������������������������������������������������������� 941 Nadia Nagra-Mahmood, Angie L. Miller, Jennifer L. Williams, and Harriet J. Paltiel Introduction�����������������������������������������������������������������������������������������������������������������  941 Technique�������������������������������������������������������������������������������������������������������������������  941 Patient Positioning �������������������������������������������������������������������������������������������������  941 Ultrasound Transducer Selection ���������������������������������������������������������������������������  941 Imaging Approaches�����������������������������������������������������������������������������������������������  941 Normal Development and Anatomy���������������������������������������������������������������������������  942 Normal Development���������������������������������������������������������������������������������������������  942 Normal Anatomy�����������������������������������������������������������������������������������������������������  946 Anatomic Variants�������������������������������������������������������������������������������������������������������  947 Accessory Breast Tissue�����������������������������������������������������������������������������������������  947 Congenital Anomalies�������������������������������������������������������������������������������������������������  947 Poland Syndrome ���������������������������������������������������������������������������������������������������  947 Polythelia/Polymastia���������������������������������������������������������������������������������������������  947 Amastia/Athelia/Amazia�����������������������������������������������������������������������������������������  947 Developmental Anomalies �����������������������������������������������������������������������������������������  948 Premature Thelarche�����������������������������������������������������������������������������������������������  948 Juvenile (Virginal) Hypertrophy�����������������������������������������������������������������������������  948 Gynecomastia���������������������������������������������������������������������������������������������������������  948 Inflammatory Lesions�������������������������������������������������������������������������������������������������  949 Mastitis and Abscess�����������������������������������������������������������������������������������������������  949 Non-neoplastic Lesions�����������������������������������������������������������������������������������������������  950 Mammary Duct Ectasia�������������������������������������������������������������������������������������������  950 Retroareolar Cysts (Obstructed Glands of Montgomery)���������������������������������������  950

Contents

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Fibrocystic Disease�������������������������������������������������������������������������������������������������  951 Galactocele�������������������������������������������������������������������������������������������������������������  952 Hematoma���������������������������������������������������������������������������������������������������������������  953 Fat Necrosis �����������������������������������������������������������������������������������������������������������  953 Intramammary Lymph Node�����������������������������������������������������������������������������������  954 Vascular Malformations �����������������������������������������������������������������������������������������  954 Venous Malformation�����������������������������������������������������������������������������������������  954 Lymphatic Malformation �����������������������������������������������������������������������������������  955 Neoplasms�������������������������������������������������������������������������������������������������������������������  955 Benign Tumors�������������������������������������������������������������������������������������������������������  955 Fibroadenoma�����������������������������������������������������������������������������������������������������  955 Hemangioma�������������������������������������������������������������������������������������������������������  955 Intraductal Papilloma �����������������������������������������������������������������������������������������  956 Juvenile Papillomatosis���������������������������������������������������������������������������������������  957 Pseudoangiomatous Stromal Hyperplasia�����������������������������������������������������������  957 Lactating Adenoma���������������������������������������������������������������������������������������������  958 Desmoid Tumor �������������������������������������������������������������������������������������������������  959 Granular Cell Tumor�������������������������������������������������������������������������������������������  960 Malignant Tumors���������������������������������������������������������������������������������������������������  960 Cystosarcoma Phyllodes�������������������������������������������������������������������������������������  960 Carcinoma�����������������������������������������������������������������������������������������������������������  961 Angiosarcoma�����������������������������������������������������������������������������������������������������  962 Hematologic Malignancies���������������������������������������������������������������������������������  962 Metastases�����������������������������������������������������������������������������������������������������������  963 References�������������������������������������������������������������������������������������������������������������������  964 Index������������������������������������������������������������������������������������������������������������������������������������� 969

About the Contributors and Editors

Contributors Patricia  T.  Acharya, MD  Department of Radiology, Children’s Hospital of Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA Sumera  Ali, MD Department of Radiology, Arkansas Children’s Hospital, University of Arkansas for Medical Sciences, Little Rock, AR, USA Maddy Artunduaga, MD  Department of Radiology, Pediatric Radiology Division, University of Texas Southwestern Medical Center, Children’s Health Medical Center, Dallas, TX, USA Richard  A.  Barth, MD Department of Radiology, Lucile Packard Children’s Hospital, Stanford University School of Medicine, Stanford, CA, USA D. Gregory Bates, MD  Department of Radiology, Nationwide Children’s Hospital, The Ohio State University College of Medicine, Columbus, OH, USA Eric S. Bih, MD  Edward B. Singleton Department of Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, USA Mitchell  W.  Boehnke, MD Department of Radiology, Children’s Hospital Colorado, University of Colorado School of Medicine, Aurora, CO, USA Christian  L.  Carlson, MD, MS  Department of Radiology, Brooke Army Medical Center, Uniformed Services University of the Health Sciences, Fort Sam Houston, TX, USA Ilse Castro-Aragon, MD  Division of Pediatric Radiology, Department of Radiology, Boston Medical Center, Boston University School of Medicine, Boston, MA, USA Harris L. Cohen, MD  Department of Radiology, Le Bonheur Children’s Hospital, University of Tennessee Health Science Center, Memphis, TN, USA Gabrielle  Christina  Maria  Colleran, MB BCh BAO  Department of Radiology, National Maternity Hospital and Children’s Health Ireland at Temple Street, University College Dublin School of Medicine, Dublin, Ireland Nathan  David  P.  Concepcion, MD  Department of Radiology, St. Luke’s Medical Center College of Medicine - William H. Quasha Memorial, Quezon City, Philippines Pedro Daltro, MD, PhD  Department of Radiology, Alta Excelência Diagnóstica/DASA and Clínica de Diagnóstico por Imagem/DASA, Rio de Janeiro, Brazil Patrick Duffy, MB BCh BAO, MSc   Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Monica Epelman, MD  Department of Radiology, Nemours Children’s Hospital, University of Central Florida College of Medicine, Orlando, FL, USA

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About the Contributors and Editors

Alexandra M. Foust, DO  Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Javier D. Gonzalez, DO, MBA  Medical Center Radiology Group, Orlando Health Arnold Palmer Hospital for Children, Orlando, FL, USA Sharon R. Gordon, MD  Department of Radiology, Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY, USA Süreyya  Burcu  Görkem, MD  Division of Pediatric Radiology, Department of Radiology, Erciyes University School of Medicine, Kayseri, Turkey Zoltan Harkanyi, MD, PhD  Department of Radiology, Heim Pal National Pediatric Institute, Budapest, Hungary Roisin Hayes, MB BCh BAO   Department of Radiology, Children’s Health Ireland at Crumlin, Dublin, Ireland Anastasia  L.  Hryhorczuk, MD  Department of Radiology, C.S.  Mott Children’s Hospital, Michigan Medicine, Ann Arbor, MI, USA Delma  Y.  Jarrett, MD Department of Radiology, New York Presbyterian Hospital, Weill Cornell Medical College, New York, NY, USA Ghadir H. Kassab, BM, BCh, MSc  Department of Radiology, Children’s Health Ireland at Temple Street, Dublin, Ireland Don-Soo  Kim, PhD Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Helen H. R. Kim, MD  Department of Radiology, Seattle Children’s Hospital, University of Washington School of Medicine, Seattle, WA, USA Wendy  G.  Kim, MD Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Ella Kipervasser, MD  Department of Radiology, Mount Auburn Hospital, Cambridge, MA, and Harvard Medical School, Boston, MA, USA Jessica  Kurian, MD Division of Pediatric Radiology, Departments of Radiology and Pediatrics, Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY, USA Jeannie  K.  Kwon, MD Department of Radiology, Children’s Medical Center Dallas, University of Texas Southwestern Medical Center, Dallas, TX, USA Bernard F. Laya, MD, DO  Department of Radiology, St. Luke’s Medical Center College of Medicine - William H. Quasha Memorial, Quezon City, Philippines Edward Y. Lee, MD, MPH  Division of Thoracic Imaging, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Mark  C.  Liszewski, MD  Division of Pediatric Radiology, Departments of Radiology and Pediatrics, Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY, USA Angie L. Miller, MD  Department of Radiology, Children’s Hospital Colorado, University of Colorado School of Medicine, Aurora, CO, USA

About the Contributors and Editors

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Elisabeth P. Moredock, MD  Department of Radiology, Children’s Medical Center Dallas, University of Texas Southwestern Medical Center, Dallas, TX, USA Marthe  M.  Munden, MD  Department of Radiology, Shawn Jenkins Children’s Hospital, Medical University of South Carolina, Charleston, SC, USA Ross  A.  Myers, MD  Department of Radiology, Lehigh Valley Reilly Children’s Hospital, Allentown, PA, USA Nadia Nagra-Mahmood, MD  Edward B. Singleton Department of Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, USA Harriet  J.  Paltiel, MDCM Division of Ultrasound, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Grace S. Phillips, MD  Department of Radiology, Seattle Children’s Hospital, University of Washington, Seattle, WA, USA Domen Plut, MD, PhD  Unit of Pediatric Radiology, Clinical Institute of Radiology, Ljubljana University Medical Centre, Ljubljana, Slovenia Ricardo Restrepo, MD  Department of Interventional Radiology and Body Imaging, Nicklaus Children’s Hospital, Miami, FL, USA Erica  L.  Riedesel, MD Departments of Radiology and Imaging Sciences and Pediatrics, Children’s Healthcare of Atlanta, Emory University School of Medicine, Atlanta, GA, USA Ian Robinson, MB ChB  Department of Radiology, National Maternity Hospital and Children’s Health Ireland at Temple Street, University College Dublin School of Medicine, Dublin, Ireland Elisabetta Sassaroli, PhD  Department of Physics, Bridgewater State University, Bridgewater, MA, USA Judy H. Squires, MD  Department of Radiology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Patrick Tivnan, MD  Department of Radiology, Boston Medical Center, Boston University School of Medicine, Boston, MA, USA Frank M. Volberg, MD  Department of Radiology, UVA University Hospital, University of Virginia School of Medicine, Charlottesville, VA, USA Phillip  Jason  White, PhD Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School and Department of Physics, Simmons University, Boston, MA, USA Jennifer L. Williams, MD  Department of Radiology, University of Central Florida College of Medicine, Maitland, FL, USA Abbey J. Winant, MD  Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA

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About the Contributors and Editors

About the Editors Harriet  J.  Paltiel, MDCM  is a Pediatric Radiologist at Boston Children’s Hospital where she heads the Ultrasound Division, and an Associate Professor of Radiology at Harvard Medical School. She is a Fellow of the American Institute of Ultrasound in Medicine, and a Fellow and Past President of the Society of Radiologists in Ultrasound.

Edward  Y.  Lee, MD, MPH  is a Pediatric Radiologist at Boston Children’s Hospital where he heads the Thoracic Division, and an Associate Professor of Radiology at Harvard Medical School. He is the Past President of the New England Roentgen Ray Society (NERRS) and the Medical Staff Organization (MSO) at Boston Children’s Hospital. Dr. Lee is the current President of the International Society of Pediatric Thoracic Imaging (ISPTI).

I am a part of all that I have met; Yet all experience is an arch wherethro’ Gleams that untravell’d world whose margin fades For ever and forever when I move. ― Alfred, Lord Tennyson, Ulysses

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Ultrasound Imaging Techniques and Artifacts Don-Soo Kim, Harriet J. Paltiel, Phillip Jason White, and Elisabetta Sassaroli

Abbreviations 4D Four-dimensional A Amplitude A/D Analog-to-digital AIUM American Institute of Ultrasound in Medicine ARFI Acoustic radiation force impulse AVF Arteriovenous fistula B Brightness C Constant-range CGS Centimeter-gram-second CNR Contrast-to-noise ratio CT Computed tomography CW Continuous wave D/A Digital-to-analog DICOM Digital Imaging and Communications in Medicine DR Dynamic range DVD Digital video disc EFSUMB European Federation of Societies for Ultrasound in Medicine and Biology EI/B ratio Elastography image size (EI) to B-mode (B) ratio Eq. Equation FDA Food and Drug Administration FOV Field of view FR Frame rate FT Frame time D.-S. Kim (*) Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA e-mail: [email protected] H. J. Paltiel Division of Ultrasound, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA P. J. White Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School and Department of Physics, Simmons University, Boston, MA, USA E. Sassaroli Department of Physics, Bridgewater State University, Bridgewater, MA, USA

IVC M MI MR NCRP

Inferior vena cava Motion Mechanical index Magnetic resonance National Council on Radiation Protection and Measurement NEMA National Electrical Manufacturers Association ODS Output Display Standard PRF Pulse repetition frequency PRP Pulse repetition period PZT Lead zirconate titanate PW Pulsed wave ROI Region of interest SI International System SSI Supersonic imaging SNR Signal-to-noise ratio SSWE Supersonic shear wave elastography SWI Shear wave imaging TGC Time gain compensation THI Tissue harmonic imaging TI Thermal index TIB Bone thermal index TIC Cranial thermal index 3D Three-dimensional TIPS Transjugular intrahepatic portosystemic shunt T/R Transmit/receive 2D Two-dimensional UCA Ultrasound contrast agents US United States WFUMB World Federation for Ultrasound in Medicine and Biology Z Acoustic impedance

Introduction Ultrasound plays a crucial role in the diagnosis and management of pediatric disorders. The ease of study performance, portability, real-time capability, lack of ionizing radiation,

© Springer Nature Switzerland AG 2021 H. J. Paltiel, E. Y. Lee (eds.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-56802-3_1

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and cost-effectiveness relative to other cross-sectional imaging techniques highlight its many advantages. In this chapter, an overview of the physics and techno­logical principles of diagnostic ultrasound is provided, including an exploration of ultrasound-tissue interactions; the pulse-echo technique; transducers and ultrasound machine instrumentation for the detection and signal processing of echoes and image formation; Doppler ultrasound; as well as B-mode and Doppler ultrasound artifacts. Advanced ultrasound modes are also discussed, including harmonic and compound imaging, elastography, 3D imaging, ultrasound contrast, bioeffects, and ultrasound safety.

propagation (e.g., circular ripples generated by the drop of a stone in a pond propagating outward on the water surface). Two types of motion occur during sound propagation: the oscillatory motion of each particle of the medium and the motion of the wave carrying energy. As sound propagates through the medium, it sets each particle of the medium into an oscillatory back and forth motion. This oscillatory motion is similar to the sinusoidal oscillations of a block attached to a spring (Fig. 1.2). An important parameter is the period T, which is the time it takes for a given particle of tissue to complete a full sinusoidal oscillation as ultrasound waves travel through it (e.g., from crest to crest or from trough to trough). This full oscillation is

Acoustics Wavelength and Frequency

k m

Since its first clinical use in 1946, ultrasound imaging has played a major role in pediatrics. The key advantages over other diagnostic imaging techniques are its lack of ionizing radiation, real-time multiplanar imaging capability, and portability. Medical ultrasound operates at frequency ranges from 1 to 20  MHz, which exceed the upper limit of the audible range in humans, that is, from 20 to 20,000 Hz (Fig. 1.1).

x -x0

1

2

Infrasound

l in Tissue (m)

5

10

ABD/OB/CARD

10

Ultrasound

102 0

101

103

104

100

Fig. 1.1  Diagram illustrating the range of ultrasound frequencies and wavelengths (bottom row) and the ranges typically associated with different medical applications of ultrasound (upper row). In medicine, low frequencies less than 2 MHz are used for therapeutic applications. The

20

PV/DERM/OPHTH

Audible

Frequency (Hz) 101

+x0

Fig. 1.2 Mechanical model of longitudinal sound wave propagation through a medium conceptualized as individual particles within the medium connected by springs. A block of mass m attached on a spring with spring constant k sits on a very smooth surface. The spring is compressed by pushing the block along a distance x0, which is then released. After being released (and neglecting friction), the mass oscillates back and forth about the relaxed position of the spring (the equilibrium position), alternatively compressing and stretching the spring. The equation describing this motion is a sine or cosine function, for example: æ 2p ö where x is the amplitude (the maximum displacex ( t ) = x0 cos ç t ÷, 0 è T ø ment from the equilibrium position), t is the time, and T is the period (the time interval it takes to complete one complete oscillation or cycle)

Ultrasound is a high-frequency sound wave. Sound can be defined as a disturbance that propagates through a medium such as soft tissue carrying mechanical energy from one region to another. In air, water, and soft tissue, sound propagates as a longitudinal wave, where the movement of the particles in the medium is in the same direction as the direction of propagation of the wave. This is in contrast to transverse waves where the movement of particles is perpendicular to the direction of wave

Therapy

x

Oscillation

Sound Propagation

Frequency (MHz)

0

105

10-1

10-2

(Medical US)

106 10-3

107 10-4

108 10-5

frequency range of 2–7 MHz is used in abdominal (ABD), obstetric (OB), and cardiac (CARD) imaging. Higher frequencies of 7–20 MHz are used for peripheral vascular (PV), dermatology (DERM), and ophthalmological (OPHTH) imaging

1  Ultrasound Imaging Techniques and Artifacts

3

known as the wave cycle. The inverse of the period is the fre1 quency: f = (Fig. 1.3). T A simple mechanical model for a longitudinal sound wave is to consider that the particles of the medium are connected by springs (Fig. 1.4). At any given instant, the combined sinusoidal oscillations of all the particles generate regions of compression, where the particles are crowded together and the springs are compressed, and regions of rarefaction, where the particles are spaced far apart and the springs are stretched. In the regions of compression, the pressure is increased above the baseline, and in the regions of rarefaction, the pressure is lower than the baseline. It is these regions of variation in pressure that propagate through the medium as a wave with constant speed c. The oscillations of the ultrasound transducer pressed against the patient’s skin generate these variations in pressure that then propagate through tissue as a sound wave, also known as a compressional wave. As a function of distance or depth in tissue, the pressure oscillates (sinusoidal oscillation), increasing and decreasing above and below the mean pressure in the tissue (Fig. 1.5).

Particle Displacement

T

x0

time

Fig. 1.3  Particle displacement as a function of time. x0 is the maximum displacement from the equilibrium position and is also known as the amplitude. Displacements are as small as a few μm. 𝑇 is the period of time required for a particle to complete a full sinusoidal oscillation. The inverse of the period (1/𝑇) is the frequency of the wave cycle

Transverse Particle Velocity

Longitudinal Particle Velocity

Fig. 1.4  A simple mechanical model for transverse and longitudinal waves. Particles oscillate up and down in a transverse wave, and back and forth in a longitudinal wave Amplitude (A0)

C

R

C

Wavelength (λ )

R

C

R

Fig. 1.5  Diagram illustrating the combined sinusoidal oscillations of tissue particles resulting in regions of compression (C) in white and rarefaction (R) in black. At a given instant in time, along the direction of propagation of the wave, the pressure variations are sinusoidal in æ 2p ö space (p = A sin ç x ÷), where the amplitude A represents the maxiè l ø

Distance or Depth (x)

...

mum variation in tissue pressure from its mean value and determines the amount of energy carried by the ultrasound wave. x is position, and λ is the wavelength of a longitudinal wave. The wavelength is the distance between two sequential bands of compression or rarefaction

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D.-S. Kim et al.

The amplitude A is the maximum variation of the pressure from its mean value in the tissue. It is an important parameter because the square of the pressure amplitude determines the amount of energy carried by an ultrasound wave. The wavelength of a longitudinal wave is the distance between two bands of compression or rarefaction (crest to crest or trough to trough). A simple relationship exists between the velocity of propagation of a sound wave (c), the wavelength (λ), and the frequency (f) given by the equation (Eq. 1.1) c =lf (1.1) The speed of sound depends on the mass density and the elastic properties of the medium. It is nearly independent of wavelength and frequency. Given the mass density (ρ) and the bulk modulus (B) of a medium, which characterizes how a tissue volume changes in response to compressional forces such as those generated by longitudinal (compressional) mechanical waves, the speed of sound can be expressed as: c=



B r

of sound in soft tissue, for a frequency of 2 MHz, the wavelength is λ = 0.77 mm and for a frequency of 10 MHz, λ = 0.15 mm.

Acoustic Impedance The acoustic impedance (Z) refers to the resistance of a particular tissue or material to the propagation of sound. Acoustic impedance is the product of mass density (ρ) and the velocity (c) of sound in the medium: Z = rc (1.3) Acoustic impedance is expressed in units of g cm−2s−1 × 10−5 in the centimeter-gram-second (cgs) system or kg m−2 s−1 in the International System (SI) of units. The SI unit is the Rayl. Tissues with similar acoustic impedance values will be indistinguishable on an ultrasound image even if histologically they are very different.

Reflection

(1.2)

Figure 1.6 illustrates the speed of sound in a number of tissue types and in a piezoelectric material, the major component of ultrasound transducers, in order of increasing speed of sound propagation. Sound travels with an average speed of c = 1540 m/sec in soft tissue and 4080 m/sec in bone. In medical ultrasound, the frequency (f) of the ultrasound beam remains constant as it propagates through different tissue types, while its wavelength (λ) changes as the propagation speed c of the ultrasound varies somewhat from one soft tissue to another. Assuming the average speed

As ultrasound propagates through tissue, it loses energy, and becomes exponentially attenuated. Part of this energy is absorbed by the tissue and converted into heat, while another portion is removed from the transmitted beam because of ultrasound-tissue interactions. These interactions include reflection, scattering, and refraction. Reflected and scattered sound generates echoes for image formation, whereas transmitted sound does not contribute to image formation. Specular reflection of ultrasound refers to the interaction of ultrasound with a smooth and relatively large surface. This

4500 4000

4080

4000

Skull

PZT

Phase speed (m/s)

3500 3000 2500 2000 1500

1450

1480

Fat

Water

1540

1565

1560

1555

1600

Blood

Liver

Muscle

1000 600 500 0

330 Air

Lung

Soft Kidney Tissue Medium

Fig. 1.6  Diagram illustrating the speed of sound in a variety of different tissues, as well as in air and lead zirconate titanate (PZT), the major component of ultrasound transducers

1  Ultrasound Imaging Techniques and Artifacts

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Diffuse Scattering Specular Reflection

Diffuse Reflection

Fig. 1.7  Ultrasound-tissue interactions important for image formation include specular reflection, diffuse reflection, and diffuse scattering. Scattering of sound occurs in every direction although the transducer detects only the backscattered sound

Z1 = ρ1c1 Z2 = ρ2c2

Z1 = Z2

Z1 ≅ Z2

Z1 >> Z2 or Z1 c1

sin θ t

=

c1 c2

c2 < c1

Fig. 1.13  Diagram illustrating Snell’s law, a formula used to describe the relationship between the angles of incidence and refraction for two tissues with sound wave speeds c1 and c2, respectively. When c2  c1, the transmitted angle θt2 is larger than the incident angle θi. θr is the reflection angle

Refraction is a change in the direction of propagation of the incident ultrasound beam that occurs when the beam strikes a tissue interface at an angle other than 90 degrees. The frequency of ultrasound remains constant, but its speed and wavelength are slightly different in the second tissue. The clinical significance of refraction is that it can cause artifacts where imaged structures appear in an incorrect location. When the ultrasound beam travels from a tissue with speed of sound c1 into a second tissue with the speed of c2, a portion of the incident ultrasound will be reflected back into the first tissue with an angle θr, that is the same as the incident angle θi: θr= θr. The reflected beam does not travel back to the transducer and the interface will not be visible. The remainder of the sound will be transmitted into the second tissue with a changed direction of propagation, that is, it will be refracted with transmitted angle θt. The angles θi, θr, and θt are located between the direction of propagation of ultrasound and a line perpendicular to the tissue interface as shown in Fig. 1.13. The angle of refraction can be calculated by Snell’s law:



sin q i c1 = sin q t c2

(1.4)

If the speed of sound in the second tissue, c2, is lower than in the first tissue c1, (c2  c1, as in the case of ultrasound entering the interface from fat to muscle, θt is larger than θi. For example, for θi = 30°, θ t = 33.5°. As θi increases, so does θt. At a particular incident angle θc, called the critical angle, θt = 90°. At the critical angle, there is no transmitted sound to the second tissue and all incident sound runs along the interface between the two tissues. This phenomenon is known as total reflection. The critical angle can be calculated from Snell’s law by substitution of sin θt = 1 into Eq. 1.4:



sin q c =

c1 c2

(1.5)

For example, the critical angle for fat-muscle interface is θc = 65°.

Attenuation Reflection occurs at a flat, smooth interface. However, some interfaces may appear slightly rough on the scale of a wavelength and reflect ultrasound waves over a range of angles, particularly as the ultrasound frequency increases, an effect similar to scattering from small structures. This type of reflection is known as diffuse reflection.

As ultrasound propagates through tissue, it becomes ­attenuated. Attenuation is caused by energy absorption by the ultrasoundtissue interactions discussed in the prior section on refraction. The absorbed energy is converted into heat. Because of the attenuation of the incident beam, ultrasound intensity becomes

8

D.-S. Kim et al. I0

I(x) = I0e-2αx

α = αs + αa x

Thermo-viscous losses

Molecular relaxation

αa

αs

Fig. 1.14  Ultrasound intensity is exponentially attenuated as it propagates through tissue. The attenuation coefficient depends on both scattering and absorption. The scattering of sound occurs in every direction,

but only the backscattered echoes reach the transducer. Absorption is caused by thermo-viscous losses and molecular relaxation

exponentially attenuated as a function of depth (Fig. 1.14). Attenuation limits our ability to image regions deep within the body. Furthermore, ultrasound is highly attenuated by air and bone, thereby severely limiting our ability to image organs such as the lungs and the brain.

ing to the transducer from a 10 cm depth will be 50 dB weaker than the transmitted ultrasound beam. This value substituted in Eq.  1.6 shows that the intensity of the echo is 100,000 times less than the transmitted beam at the skin surface. The depth of penetration is defined as the maximum depth beyond which the echoes are too small to be detected by the ultrasound transducer. Penetration becomes increasingly smaller as ultrasound frequency increases. Because image quality increases with frequency, the highest frequency compatible with a given depth of penetration is chosen by the ultrasound operator.

Intensity is defined as the energy delivered by the ultrasound wave per unit time, per unit area perpendicular to the direction of propagation of the wave. Because of the enormous variation in intensity during ultrasound propagation, it is common to use a logarithm scale for intensity measurement. The attenuation in intensity is given in decibel units as æI ö attenuation in dB = 10 ´ log ç 1 ÷ , dB è I2 ø

(1.6)

I1 where I 2 is the ratio between the input and the output ultrasound intensity, and log is the base 10 logarithm. Attenuation increases with depth and with frequency. For a round-trip, the attenuation at a depth d in dB is

attenuation in dB = a ´ ( 2 ´ d ) ´ f

(1.7)

where α is the attenuation coefficient for a given tissue in dB/ cm/MHz, f is the ultrasound frequency in MHz, and d is the distance travelled by the ultrasound beam in cm. The average soft tissue attenuation is 0.5 dB/cm/MHz. The attenuation coefficient depends on both scattering and absorption. As an example, a transmitted ultrasound beam of frequency 5 MHz traveling a depth of 10 cm from the skin surface will be attenuated by 25 dB. The returning echo will be also attenuated by 25 dB as it returns back to the probe, for a total of 50 dB attenuation. This means that the echo return-

Distance Measurement Diagnostic ultrasound imaging is primarily implemented with the pulse-echo technique, which is made possible by the relatively slow speed of propagation of ultrasound in soft tissue, where c = 1540 m/s and the use of short-duration ultrasound pulses. With the pulse-echo technique, the ultrasound transducer sends out an ultrasound beam of short duration. Structures within the beam path cause some of the ultrasound to be reflected and scattered. Some of this reflected and scattered ultrasound (i.e., echoes) travels back along the path of the transmitted beam to the transducer where it is detected. The ultrasound machine determines the time between the transmission of the ultrasound pulse and the reception of a given echo. This time is known as time-of-flight. The time-of-flight is then used by the machine to calculate the distance between the transducer and the structure causing the echo:

1  Ultrasound Imaging Techniques and Artifacts

d=



9

c´t 2

(1.8)

with c = speed of sound in soft tissue. In ultrasound machines, this speed of sound is taken to be the average speed of sound in soft tissue: c = 1540 m/s. For example, with a depth of 1 cm, the time-of-flight is 13 μs, and for 10 cm, it is 130 μs. For this time scale, it is relatively simple for the electronic circuits to distinguish reflections at different depths with good resolution, and therefore to locate reflectors at different depths. To improve localization of a reflector, the pulse must be short. A short-duration pulse is obtained when the transducer generates ultrasound for a short-time duration of several microseconds (μs). The pulse duration is usually expressed in terms of the number of wave cycles. A typical pulse has a Pulse sum of different frequencies





Sinusoidal waves of different frequencies

Amplitude

Fig. 1.15  An ultrasound pulse consists of a sum of continuous sinusoidal waves spanning a range of frequencies. The pulse travels with a group velocity, and each sinusoidal wave has a phase velocity. The difference between phase velocity and group velocity is a small ultrasound wave that it is usually ignored. Each sinusoidal wave is assumed by the ultrasound machine to travel at speed c = 1540 m/s

duration of 3–5 cycles. At a frequency of 5 MHz, the period is T = 0.2 μs, and therefore 4 cycles last for about 0.8 μs. Fourier analysis shows that a short pulse consists of a continuous sum of sinusoidal waves of different frequencies (p = A sin (2πft)) (Fig. 1.15). This sum is within a defined range of frequencies and is dominated by the central frequency of the pulse, which has the highest amplitude and therefore carries the most energy. The ultrasound machine assumes that each frequency that makes up the beam travels at the same speed c = 1540 m/s. This is a good approximation, as the variation of speed as a function of frequency (i.e., dispersion) is very small for ultrasound, and therefore, the phase velocity and group velocity for ultrasound waves are very close to each other [2]. More important factors affecting ultrasound speed are the elastic properties and mass density of each tissue and the amplitude of the wave. The range of frequencies that make up a pulse is referred to as the frequency spectrum, and it can be represented graphically by displaying the amplitude associated with each frequency within the pulse (Fig. 1.16). The graph is centered on the center frequency, which has the highest amplitude, and therefore, the highest energy associated with it. The bandwidth is defined as the range of frequencies that comprise the pulse. Bandwidth is related to the pulse duration by

1

2

3 4 Frequency (MHz)

5

6

Fig. 1.16  Diagram of a frequency spectrum and pulse bandwidth 1/τ

(1.9)

For example, a 5 MHz pulse of duration 0.8 μs has bandwidth of 1.25 MHz. A short pulse yields a satisfactory time resolution and therefore good distance resolution (i.e., axial resolution) and its echoes contain information from a wide range of frequencies. In contrast, the information contained in an echo from a long pulse is concentrated near the central frequency and gives a stronger signal at that frequency. However, a longer pulse has poor distance resolution. In order to generate an image, the ultrasound machine must repeat the process of transmitting a pulse and receiving the echoes several times, moving the beam so that it passes through a different volume of tissue each time. Pulse repetition frequency (PRF) is defined as the number of pulses transmitted by the ultrasound machine in one second. PRF is limited by the maximal depth of penetration, which depends on the individual transducer settings and the tissue being evaluated. The ultrasound machine does not transmit a new pulse before it receives all of the echoes from the previous pulse. The time to receive the echo from a maximum depth penetration (i.e., range) Dmax is derived from Eq. 1.8:

1/t

0

1 Bandwidth = t

tmax =

2 ´ Dmax c

(1.10)

This is the shortest time between two consecutive pulses, and it defines the pulse repetition period (PRP), which is the time between two consecutive pulses (Fig. 1.17). The inverse

10

D.-S. Kim et al. PRP

Pulse duration (~1-2 µs)

Dmax =

PRP 2

c

PRP (µs)

PRF (kHz)

Range (cm)

100

10

7.7

150

6.7

11.6

250

4

19.3

500

2

38.5

Duty cycle = 0.2-2%

Fig. 1.17  The pulse repetition period (PRP) is determined by the range Dmax (maximum depth of penetration) and is the time interval between two consecutive pulses. Some values for Dmax and corresponding PRF are shown FOV D

FOV FOV FOV

D

N

N

PRP

D = Depth (m) FOV = Field of View (m)

LD = N / FOV = Line Density (m-1)

N = Number of lines FT = PRP x N = Frame Time (s)

FR = 1/FT = PRF/N = Frame Rate (fps or s-1)

Fig. 1.18  N scan lines (lines-of-sight) are required to generate an image for a given depth D. The field of view (FOV) is constant for a linear array transducer. The FOV changes as a function of depth for a sector array transducer

of this number is the maximum number of pulses that can be transmitted in one second and is given by:



PRFmax =

c 2 ´ Dmax

(1.11)

Therefore, for a small depth of penetration, the machine increases the PRF and for a larger depth, it reduces the PRF.  For example, for a range Dmax  =  7.7  cm, the PRF is 10 kHz. If the depth is increased to Dmax = 19.3 cm, the PRF is reduced to 4 kHz. The duty cycle (i.e., the time occupied by the cycle of operation of the ultrasound machine as a percentage of available time) is the ratio between the pulse duration and the PRP.  The PRP is much longer than the pulse duration, so that following the transmission of the pulse,

most of the time is spent by the transducer in “listening” to the returning echoes. The frame rate (FR) is defined as the number of images generated in one second. For image creation, an ultrasound machine transmits a number of sequential pulses. Each pulse travels along the path defined by the ultrasound beam width. The beam is often represented as a line known as the scan line or line-of-sight (Fig. 1.18). When creating an image, the ultrasound machine transmits N pulses with the total number of pulses generated in one second equal to N × FR. This number is by definition the PRF, so that the FR can be expressed as

FR =

PRF N

(1.12)

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11

The inverse of the FR is the frame time (FT): FT =

N = N ´ PRP . By inserting Eq. 1.11 into Eq. 1.12, PRF

we obtain the maximum FR

FR max =

c

(1.13)

2 ´ Dmax ´ N

Equation 1.13 is usually written as

FR max ´ Dmax ´ N =

c = 77, 000 cm / s 2

(1.14)

If a high FR is desired, the depth of penetration will be lower and/or a relatively small number of transmit pulses will be available to create each image. For example, if N = 100 and Dmax = 25 cm, the maximum FRmax is 30 frames (images) per second.

Instrumentation

Electrical signal

The four key elements of diagnostic ultrasound imaging include generation of the ultrasound beam, detection of the

time (sec)

Fig. 1.19  Electrical signal sampling. Electrical signal is sampled at regular time intervals (indicated by the red dots) and converted into binary numbers

returning echoes, signal processing of the acquired echo signals, and formation of the ultrasound images. Ultrasound machines have digital processing with analog and digital electronics, with a trend toward increasing levels of digitization. The transducer can convert electrical signals (voltage pulses) into ultrasound pulses and ultrasound echoes back into electrical signals. These electrical signals are analog signals. An analog electrical signal is a voltage pulse that varies continuously as a function of time. It is converted to a “digital” signal by an analog-to-digital converter (A/D converter). A digital signal is a series of binary numbers spaced at regular time intervals. Each number represents the value of the analog signal at the instant when it was detected (Fig. 1.19). An A/D converter can also convert a digital signal into an analog signal. For example, when an echo is transformed by the transducer into an analog echo signal, after pre-­ amplification, the A/D converter samples (i.e., measures) it at regular time intervals (e.g., 0.1 μs). The resulting digitized signal consists of ten million binary numbers (“samples”) per second. Provided that the number of samples per second is sufficiently high (a sampling rate of 20–40 MHz), no information is lost in the digitization process. In state-of-the-­art-ultrasound machines, beamforming is implemented using digital techniques (covered later in this chapter). A schematic block of a high-end ultrasound machine is shown in Fig. 1.20.

Transmitter The generation of the ultrasound beam is achieved by a transmitter (also known as a pulser), the transmit beamformer, and the transducer. State-of-the-art ultrasound machines perform digital beamforming, where each transducer element has its own transmitter, A/D converter, ampli-

Receive Beamformer A/D

T/R Switch

D/A

Delay + Processing

Processing

Central Controller

Display

Delay + Processing

Console

Transmit Beamformer

Fig. 1.20  Schematic block diagram of an ultrasound machine. T/R, Transmit/receive; A/D, analog-to-digital; D/A, digital to analog

12

fier, and transmit-receive switch. The transmitter provides voltage pulses (electrical signals) to the transducer for exciting the piezoelectric transducer elements which generate the ultrasound pulses that are then transmitted into the body. The transmitter is programmed by the machine’s central controller (computer) to produce voltage pulses of the correct frequency, pulse duration, amplitude, and appropriate PRF. These settings are initially set at default values by the machine when the probe and examination type are selected at the start of the examination. However, the user has the ability to subsequently change a number of these settings. The transmitter also controls the output transmit power by adjusting the applied voltage amplitude. The maximum voltage is limited by federal regulation for purposes of patient safety. The transmit beamformer manipulates the electrical pulses to be sent to the transducer elements so that the transmitted ultrasound beam has the correct position, shape, and size. The transmit beamformer delays the transmitted electrical signals sent to each transducer element by an appropriate time interval so that the beam is focused at the chosen depth. This process is covered in more detail below. In high-end ultrasound machines, this manipulation is achieved digitally, and the A/D converter of each element converts the digital signal into a suitable analog signal. When the switch is in the transmit mode, the analog signal excites the transducer element. Immediately following the ultrasound pulse transmission, the switch is set to receive mode.

Transducer The transducer that is contained inside the ultrasound probe is the active component of the probe. An ultrasound transducer is an electroacoustic device that produces ultrasound by converting the electrical signal pulse generated by the transmitter into an ultrasound pulse that is sent into the body. The same transducer detects the echo pulse and converts it into an electrical pulse. The major components of a transducer include a piezoelectric plate, a matching layer, a backing layer, and onboard electronics. A simplified diagram of a typical transducer is shown in Fig. 1.21. The piezoelectric plate is a thin crystal that can produce and detect mechanical vibrations. The thickness of the crystal is designed to be exactly half the wavelength of the generated ultrasound pulse. A higher frequency transducer that is used for high-resolution images of superficial structures has a thinner piezoelectric crystal than a lower frequency transducer used for imaging tissues and structures at greater depth. While some naturally occurring materials such as quartz have piezoelectric properties, their efficiency is very low. The development of ceramic materials has made ultrasound imaging possible, with lead-zirconate-titanate (PZT) the most commonly used. PZT can be molded into different

D.-S. Kim et al.

Onboard electronics

Transducer backing Piezoelectric element Matching layer

Fig. 1.21  Diagram of a typical linear array transducer

shapes with chemical additives to produce various properties that can be used in a variety of imaging applications. Until recently, all ultrasound transducers were made from ceramic materials which limited bandwidth. Pulses with large bandwidth are required to improve image quality. Currently, larger bandwidth is achieved with a new generation of materials that are composites of ceramics and polymers. Ultrasound probes made of these materials are referred to as broadband probes. For the sake of simplicity, we will only consider PZT transducers in this discussion. However, composite transducers are similar to purely ceramic transducers, with the main difference consisting in the material used as for the piezoelectric plate. A damping layer is placed behind the ceramic plate. This layer is designed to absorb energy and keep the transmit pulse relatively short; it is generally made of plastic that contains metal particles. A suitable matching layer which is also usually made of plastic, is placed in front of the ceramic plate to minimize the acoustic impedance mismatch between the ceramic material and the soft tissues of the body so that more acoustic energy can be transmitted into the tissue. Finally, a rubber lens along the transducer face makes contact with the patient.

Receiver The detection of echoes is achieved by the transducer and the receive beamformer. The transducer detects echoes as a function of time (or depth). Once the returning echo interacts with

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Amplification

TGC

Compression

Rectification Demodulation Rejection

Fig. 1.22  Processing of the echo signal includes time gain compensation (TGC), dynamic range compression, rectification, demodulation, and noise rejection

the piezoelectric plate, the plate is deformed and changes in thickness. This deformation generates a voltage difference across the two electrodes. Since ultrasound is highly attenuated with depth, an echo signal can be very weak. The echo received by each array element is boosted by the amplifier to a higher amplitude to facilitate subsequent processing and for minimizing the effect of electronic noise. The amount of amplification (or gain) is preset by the machine, but the user can make adjustments. The amplified echo signal is then transformed into a digital echo signal by the A/D converter. The receive beamformer delays the received echo signal from each transducer element by an appropriate interval so that the ultrasound beam is focused at the depth from which the echo arises, as discussed below. After the echo signal is augmented by the amplifier and digitized by the A/D converter, it is ready for processing. Signal processing can be divided into the following procedures: time gain compensation (TGC), rectification, demodulation, filtering (noise rejection), and dynamic range compression (Fig. 1.22). The ultrasound beam is attenuated with depth, and different tissues have varying rates of attenuation. TGC is used by the machine to apply a time-varying gain to the signals, beginning with a relatively low gain for superficial depths and increasing steadily with time as the echoes are received from greater depths. Because different tissues have variable attenuation, it is often necessary for the user to fine-­tune the TGC function to account for these variations. This fine-tuning is generally provided in the form of a series of slider controls. Dynamic range (DR) refers to the overall range of echo intensities used to form the image. It can be described mathematically as



æI ö DR = 10 ´ log ç max ÷ , dB è I min ø

(1.15)

where Imax is the intensity of the strongest echo, and Imin is the intensity of the weakest echo. The dynamic range of 60 dB corresponds to a ratio

I max = 1, 000, 000. The dynamic I min

range of an ultrasound signal is 60 dB or more. In comparison, human vision has a dynamic range of at most 30 dB. The echo signal is then compressed into 30  dB of grayscale dynamic range by the dynamic range compression function of the machine. The machine rectifies the echo signal (i.e., inverts the negative amplitude values to positive values) and removes the variations associated with the ultrasound frequency, leaving only the echo signal amplitude. This process is referred to as demodulation and amplitude detection. Finally, the digital signal is filtered to reduce electronic noise (noise rejection). Electronic noise has equal intensity at all frequencies. Noise is eliminated for the frequencies outside the bandwidth of the echo signal. Once the echo signals are processed as described above, image processing occurs. The scan converter writes the echo signals into the image memory. The image memory is a part of the ultrasound machine’s digital memory, which is used to store the processed echo signals. It consists of a two-dimensional (2D) array of pixels (pixel elements). A typical size is 1024 pixels wide by 768 pixels high, yielding a total of 786,432 pixels. Each pixel stores a digital number which determines the displayed shade of gray. This number is typically 8 or 12 bits long, providing 28 = 256 or 212 = 4096 different gray levels.

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The echo information is acquired one scan line at a time. The scan converter assembles the echo signals in the image memory by ordering information from the beamformer on the time of transmission and direction of the ultrasound beam so that each processed echo signal is at the correct position in the image memory. The scan lines may or may not pass through every pixel in the image memory. The scan converter uses a mathematical technique known as “interpolation” to fill in the gaps between the scan lines with appropriate values, so that the image is not degraded. Some preprocessing of the processed echo-signal is implemented prior to writing to the image memory. This may include the depth displayed on the image, zoom, persistence (average of recently acquired images to reduce speckle), extended field of view (FOV), and compound imaging. These changes made during preprocessing are permanent. Postprocessing changes that may be implemented when the stored image is read out for display are not permanent and may include measurements, color mapping, postprocessing zoom, and grayscale postprocessing curves.

mid-gray, a strong echo as white, and no detectable echo as black. B-mode scanning produces an image of a tissue slice in any anatomical plane. The B-mode display is used for 2D grayscale imaging as follows: the scan line in B-mode is swept throughout the plane of interest to generate a 2D tomographic image built by multiple scan lines, as shown in Fig.  1.18. The grayscale range should be wide enough to properly display small differences in the amplitude of the returning echoes arising from different sites in the body. A-mode was widely used in the early days of diagnostic ultrasound. In A-mode scanning, the beam is kept at a fixed position and the machine transmits and receives along the beam direction. The display shows echo amplitude as a function of depth. Since A-mode scanning displays detected echoes in unaltered form as long as the transducer is stationary, it is useful for certain clinical applications such as tissue characterization, localization of foreign bodies in the eye, or identification of breast cysts. M-mode is used to provide information regarding movement and is mainly used in obstetrical imaging to detect embryonic Image Display cardiac activity and in echocardiography to provide information regarding motion of the walls of the heart and cardiac valves. As Once image processing is complete, the image can be dis- with A-mode, in M-mode the ultrasound beam is fixed in posiplayed or stored. Brightness (B)-mode imaging is the most tion and repeatedly transmits pulses and receives echoes along commonly used technique in clinical ultrasound imaging. this position. Structures that are stationary relative to the probe Two other imaging modes used for specific applications (e.g., the chest wall) are displayed at a constant depth as horiinclude amplitude (A)-mode and motion (M)-mode. zontal lines, while structures that move toward and away from When a reflector is included within the ultrasound beam the probe (e.g., the walls of the heart) move up and down with as previously discussed, the reflector is placed at the correct their position displayed as a function of time (Fig. 1.23). depth and location on the mid-line of the beam (Fig. 1.23). Constant-range (C)-mode is a method of display of cross-­ This midline is referred to as either the scan line or the line-­ sectional echo data where the imaged plane is at a constant of-­sight. In B-mode imaging, the reflector is shown as a range from the transducer and perpendicular to the interrobrightness dot, which represents the echo intensity. A weak gating beam. echo will appear as dark gray, a moderate intensity echo as

Image Storage

A-Mode (1D) B-Mode (1D)

In addition to appearing on the ultrasound machine display monitor during a clinical examination, ultrasound images can be stored in machine memory, on a removable storage device (e.g., a digital video disc [DVD]), or on a network. Digital Imaging and Communications in Medicine (DICOM) is the most commonly used standard for storing and transmitting medical images, including ultrasound images and related data.

B-Mode (2D) C-Mode (2D)

Time

Mechanical Transducer M-Mode (1D+1D)

Fig. 1.23  Diagram illustrating imaging of a reflector in brightness (B), amplitude (A), constant-range (C), and motion (M) modes

The simplest type of mechanical transducer is a piezoelectric plate. A sketch of a plane rectangular transducer is shown in Fig.  1.24. A diagram of a plane circular transducer with radius a is shown in Fig. 1.25. The scan plane is the x-z plane

1  Ultrasound Imaging Techniques and Artifacts

15

y

Elevational, Slice Thickness P

r z Axial, Longitudinal

φ

Lateral, Azimuthal

x

Fig. 1.24  Diagram of a plane rectangular transducer. The Cartesian coordinates (𝑥, z) and the spherical polar coordinates (𝑟, 𝜃, 𝜙) of a point P are shown. Transducer is located in the x-y plane in the diagram. The scan plane is the x-z plane, and the z-y plane is the elevation plane y

r

a

z

The beam patterns for a disc transducer on the scan plane (x-z plane) are shown in Figs.  1.26, 1.27, 1.28, and 1.29. These figures are generated from diffraction theory as applied to ultrasound transducers. A discussion of diffraction theory is beyond the scope of this chapter but can be further explored by the interested reader [3, 4]. The main portion of the ultrasound beam is located within the bounds of the transducer surface up to a depth:

x

Fig. 1.25  Diagram of a plane circular transducer of radius a. The rectangular coordinates (x, y, z) and the polar coordinates (r, θ) are shown

Focal plane =

Near-field (Fresnel)

a2 λ

Far-field (Fraunhofer)

Fig. 1.26  Diagram illustrating pressure amplitude along the transducer axis and in the scan plane

and the transverse (i.e., lateral or radial) planes are perpendicular to the z-axis and parallel to the x-y plane. The transducer axis is the z-axis. An ultrasound wave is generated by the back-and-forth oscillations of the disc and the wave propagates in a direction perpendicular to the disc.

z0 =

a2 l

(1.16)

This depth defines the location of the focal plane. Beyond this plane, the beam diverges (Fig.  1.30). The region from the transducer to the focal plane is called the near-field or Fresnel zone, and the region beyond the focal plane is the far-field or Fraunhofer zone. The depth z0 in Eq. 1.16 is the near-field depth. The spreading of the beam in the far field is due to diffraction and is caused by the relatively large ultrasound wavelength. This divergence is the major factor limiting spatial resolution in ultrasound imaging. As shown in Fig. 1.26, in the near-field zone, the pressure amplitude along the transducer axis has an oscillatory pattern. At z0, the pressure reaches a final maximum value. In the farfield zone, the pressure amplitude falls approximately as 1/z 1 and therefore the intensity as 2 . As shown in Figs.  1.26 z and 1.27, the oscillatory pattern of crests and troughs in the near-field zone is not restricted to the transducer axis but occurs in the entire near-field zone. In the far-field zone, the beam pattern becomes simpler (Fig. 1.27). The pressure amplitude has a maximum value on the z axis (beam axis) that decreases as 1/z (Fig. 1.26). The pressure amplitude falls off with radial distance r from the beam axis (Fig. 1.27). In this zone, the main beam width increases linearly with depth of approximately λz/a. In Fig. 1.27, the contour plot of the pressure amplitude is also shown. The contour lines are symmetrical relative to trans-

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Far-field (Fraunhofer)

Focal plane a2/λ

Near-field (Fresnel)

Fig. 1.27  Diagram of pressure amplitude and contour plot in the scan plane. Pressure amplitude in transverse planes at different locations is shown along the transducer axis

a/λ= 2.0

a/λ= 3.2

a/λ= 6.4

Fig. 1.28  Pressure amplitude in the scan plane in the near-field zone for different values of

ducer axis and on each contour line the pressure amplitude has the same value. This figure also shows the pressure amplitude as a function of r at different depths. In the near-field zone, the pressure amplitude in the transverse planes shows several small oscillations. At the focal plane z0, the pressure amplitude shows a main lobe with the highest peak and the smallest beam width (about equal to the transducer radius a). In addition, there are

a/λ= 10

a l

two weaker side beams, termed side lobes. In the far-field zone the pressure amplitude in the transverse direction is significantly reduced and is spread due to diffraction. In both the near-field and far-field, the pressure undergoes rapid oscillations. However, these variations are generally averaged out and the signal obtained by a receiving transducer varies little within the near-field zone. As a result, a

1  Ultrasound Imaging Techniques and Artifacts a = l

17

0

0.2

0.5

0.7

0.8

0.9

1.0

2.0

3.0

5.0

10.0



a Fig. 1.29  Pressure amplitude in the scan plane in the far-field zone for different values of l Near-field

Circular Flat Transducer

Far-field

a

Divergence Angle q

z0 Focal plane

a2 Fig. 1.30  Illustration of the near-field and far-field of a circular flat transducer with radius a and focal length z0 = . The divergence angle θ is l defined as the angle between the transducer axis and the edge of the main central lobe

transducer with radius a remains approximately collimated to the near-field depth and then diverges. The beam diverges as

sin q = 0.61 ( l / a )

(1.17)

where θ is the angle between the transducer axis and the edge of the main central lobe, as shown in Fig. 1.30. A circular flat transducer can therefore generate a good lateral (transverse) resolution up to about the focal plane a2 ( z0 = ). It is clinically important to have good lateral resol lution in order to correctly image a given structure since the ultrasound machine places all the echoes gathered by a particular beam along the midline of the beam. The narrower the beam, the more accurate the location of the structure in the ultrasound image. When, a ≅ λ, the near-field is short and the beam diverges rapidly in the far-field, i.e., θ is large. When a is large compared to λ, the near-field is long and there is little divergence

in the far-field, i.e., θ is small, an optimal imaging situation. These trends are illustrated in Fig. 1.28 where the scan plane beam patterns in the near-field zone are shown for different values of a/λ. As shown in the figure, the oscillatory pattern a increases as a function of , but are averaged out at l detection. This information can provide a way to design ultrasound transducers to have approximately near-field performance up to a given depth z0. For example, if the transducer has a radius a  =  7.5  mm and operates at a central frequency of 3  MHz: a λ  =  0.51  mm (wavelength in soft tissue), = 11, the focal l plane depth is z0 = 110 mm, and the divergence angle is small with θ  =  2.4°. For a higher frequency, a smaller radius a is required in order to maintain a collimated beam up to the focal plane. For example, if the transducer operates at a central frequency of 10  MHz and has a radius a  =  2  mm: a λ = 0.51 mm, = 13, the focal plane depth is z0 = 26,and an l angle of divergence remains small at 2.6°.

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Increased frequency allows the source diameter and the beam width to be scaled down, while maintaining the beam width divergence small, even if the focal depth is short. Increased frequency also results in greater ultrasound beam attenuation. The beam patterns in the focal plane for different values of a/λ are shown in Fig. 1.28. For small values of a/λ, i.e., for low frequency or for a relatively small transducer, pressure is nearly independent of direction. As a/λ increases, the ultrasound intensity along the beam axis increases. For a flat ­circular transducer of radius a  =  7.5  mm and f  =  3  MHz, a = 16, the beam pattern includes a main lobe and sides lobes. l To overcome the shortcoming of unfocused transducers like the one shown in Fig.  1.25, focused transducers were introduced. Focused transducers are curved or have an attached acoustic lens as depicted in Fig. 1.31. The effect of the transducer curvature or the presence of the lens is that at a depth equal to the focal depth z = F as shown in Fig. 1.32, the beam width is the same as that obtained for the circular plate transducer in the far-field zone and can be approximated as:

Beam width = 2.44

lF D

(1.18)

with D transducer aperture. This is the so-called diffraction limit and is the best theoretical value that can be obtained for the beam width for a given aperture D and wavelength. Beyond that the beam diverges as it does with unfocused transducers. Thus, a focused transducer with a larger aperture D compared to λ can generate a small beam at this depth. The additional advantage of using focused transducers is that the beam pressure (or intensity) can be much larger in the focal plane. This result can be obtained from diffraction theory as well. The focus or focal depth is defined as the point on the beam axis where the beam intensity is the highest and the beam width is the smallest, and is given by Eq. 1.18. The beam can be narrowed not just at the focal plane but over a range of depths known as the focal zone (Fig. 1.33). Focusing can be strong or weak. A strongly focused transducer has a narrow beam at the focus and a short focal zone with rapid beam divergence in the far-field. A weakly focused transducer, with F/D > 1 has a longer focal zone, diverges less rapidly than the strongly focused transducer, and is more suitable for medical imaging. The beam patterns generated by a flat disc transducer and a curved or lens transducer can be obtained in a rigorous way from diffraction theory but can be also understood intuitively by considering the superposition principle and Huygens’ principle. The superposition principle states that when two or more waves reach the same location at the same time, their amplitudes sum algebraically (Fig. 1.34).

Focused (Concave) Transducer

Focal Zone

Plane (Linear) Transducer

Acoustic Lens

Fig. 1.31  Diagram of a focused transducer with a concave crystal (upper image) and a plane (linear) transducer focused with an acoustic lens (lower image)

Curved Transducer

F (Focal length)

Fig. 1.32  Curved transducer with a radius of curvature of F. Spherical wavefronts are also shown where all points of the propagating wave have the same phase. If the pressure waves are emitted in phase by each point on the surface of a spherically curved transducer, they will all intersect at the common point (i.e., the geometrical focus in figure) in phase. This occurs since they all travel the same distance to produce maximum constructive interference, and therefore maximum intensity at the focus. The wavefronts do not collapse to a point, because of the diffraction limit. Beyond the focus the beam diverges

a

b

Strongly Focused Curved Transducer

Weakly Focused Curved Transducer

Focal zone

Focal zone

Fig. 1.33  Two curved transducers, one strongly focused (a) and one weakly focused (b). The focal zone is shorter and more superficial with the strongly focused transducer

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19

A +

+ B =

=

A+B

a

b

Fig. 1.34  Superposition principle for two waves with same amplitude. (a) If the waves arrive at the same location with the same phase (i.e., their peaks and troughs coincide in time), their amplitudes are additive (constructive interference). (b) If the waves reach the same location with opposite phase (i.e., the peaks of one coincide with the troughs of the other), the result is complete cancellation (destructive interference)

Consider, for example, two waves of the same amplitude. If they arrive at the same location with the same phase (i.e., with their peaks and troughs coinciding in time), their amplitudes are additive (constructive interference). If they reach the location with opposite phase (i.e., the peaks of one coincide with the troughs of the other), the result is complete cancellation (destructive interference). If they reach the location with different phases (not opposite), the wave sum has a lower amplitude. Huygens’ principle states that points on the transducer surface act as point sources of spherical ultrasound waves, which have the same amplitude and frequency, and are emitted in phase. The pressure amplitude at a location P in the ultrasound beam is determined by the sum of the spherical waves from all of the points on the transducer face. If r is the distance between a transducer point and a location P, the phase acquired by the spherical wave emitted by this point is ϕ = (2πf)r/c, where r/c is the time-delay and f is the central frequency. In a circular plate transducer, different points on the transducer face have different distances to location P, so the waves acquire different phases. At some location, this results in overall constructive interference, giving rise to an amplitude maximum. At other locations, the overall effect is destructive, and a minimum amplitude is formed. This is the reason why in the near-field, for example, the pressure amplitude is not constant but shows many peaks and troughs. With spherically curved transducers, when waves are emitted in phase at the transducer surface, they will acquire the same phase traveling to the focus (ϕ  =  2πfF/c), their amplitudes sum and the intensity at the focus is maximum.

For a location different from the focus, the distance between this location and a point on the transducer surface changes. Therefore, the waves emitted by the point sources on the transducer surface will arrive at the same location with different phases, as they travel different distances, and the wave sum will have a much lower amplitude. A lens in front of a flat-surface transducer will achieve the same result as a spherically curved transducer. The lens is thickest at its center. This will delay the wave traveling through the center more than the waves traveling at the edges of the lens. These delays lead to an in-phase sum at the focus. The earliest and simplest transducers for medical applications used a fixed focused single element to generate and receive ultrasound pulses. These transducers were supported by a mechanical arm and moved along the body surface and could be tilted. Position data were encoded by the mechanical arm system, which made it possible to display echoes as intensities on the display monitor. Mechanical transducers are relatively inexpensive and easy to operate. However, their low-speed mechanical scanning, lack of variable ­focusing, and lack of real-time imaging subsequently led to the development of multiple-element electronic transducers. These arrays can electronically reproduce the effect of focusing a curved transducer or a lens.

Array Transducer One of the remarkable advancements in ultrasound instrumentation has been the development of multiple-element electronic transducers, or array transducers. In an array transducer, the ceramic plate is sliced into a large number of identical transducer “elements” to facilitate electronic focusing at different depths and steering (change of direction) of the ultrasound beam to a region of interest (ROI). Narrowing the beam to obtain better lateral resolution at a given depth is referred to as focusing. Array transducers achieve focusing electronically. As discussed above, better focusing is obtained when the ultrasound frequency is high and/or the transducer aperture is large. In array transducers, the ultrasound machine electronically creates the same effect of a curved transducer or a lens. To illustrate the principle of electronic focusing, we can consider the simplest case of a phased-array transducer. A phased-array transducer uses all of the elements to form a transmit pulse. Once the focal depth is selected by the user, the machine determines the distance between each element and the focus. This information together with the assumed speed of sound in soft tissue of 1540  m/s is used by the transmit beam-former to set a suitable time-delay for each electrical signal sent to an element, so that each element is activated at a slightly different time. The outermost elements transmit first, followed by the elements adjacent to them and so forth. The central element transmits last.

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The beam is essentially identical to one that a spherically curved transducer would produce, since the wavefronts converge to the focus (Fig. 1.35). Different focal depths can be chosen (Fig. 1.36). If the phased-array has 128 elements, then a total of 128 electronic delays are required. The term

Signals

n = 64-128

Fig. 1.35  Focused beam generated by a phased-array transducer. All the elements are used to generate the beam

Signals

“channel” is used for these circuits. The number of channels typically ranges from 64 to 128 elements, depending on the quality and cost of the machine. In order to generate an image, a phased-array transducer scans the beam by steering sequentially in a number of directions (Fig. 1.37). The steering of the beam can be also obtained by applying suitable time delays. The delays required to steer the beam are added to the delays required to focus the beam. A typical phased-array sweeps the beam approximately 90° from left to right, with each scan line (i.e., the midline of the beam or line-of-sight) rotated by about 1° to the previous scan line. This process requires about 90 transmit pulses to form an image. Focusing in reception is based on the same principle as focusing in transmit. For each scan line, the echo received from a given depth arrives at each element of the array at a slightly different time. The echo arrives at the center element first, so the receive beam-former applies the longest delay to the electrical signal for this echo. The echo arrives at the outermost elements last and therefore the beam-former applies the shortest delay to them. As a result of these time delays, the signals are in phase when they are added together electronically for processing. Unlike transmit focusing, focusing in reception is automatically controlled by the machine, a process termed dynamic focusing. At each instant, the machine can determine the depth of the returning echoes. Since the time needed for a two-way trip increases by 13  μs for every additional 1 cm of depth, the machine automatically advances the receive focus at the rate of 1 cm every 13 μs, starting immediately after the transmission of the pulse. At the same time, as focus in reception is advanced, the number of elements used to receive the echoes increases

Signals

Signals

Focal plane

Fig. 1.36  Beams generated by a phased-array transducer that are focused at different depths. All the elements are used to generate the beams

1  Ultrasound Imaging Techniques and Artifacts

Signals

21

Signals

Signals

Fig. 1.37  Steering of the beam in different directions by a phased-array transducer

Signals

n = 256-512 n ~ 20

Fig. 1.38  Group of active elements in a linear array generating a beam that is perpendicular to the transducer face

(receive aperture). This is known as “dynamic aperture.” The reason for this is that the beam width at the focus is inversely proportional to the transducer aperture (Eq. 1.18). It is therefore advantageous for the active receiving group to have as many elements (i.e., as large an aperture) as possible. However, there is no benefit in using a large group when receiving echoes from superficial structures since elements far from the center of the group will not receive echoes from these

structures. Thus, the maximum number of elements included in the beam increases with time after transmission, in proportion to the depth of the reception focus. As a result, the beam width in successive focal zones remains fairly constant, keeping lateral resolution as uniform as possible at all depths. A typical linear array transducer has between 256 and 512 elements. The beam is created using an adjacent group of elements, ranging from 20 to 128. With a 256 linear array, a first group of elements (i.e., 1, 2, 3, … to 20) generates an ultrasound beam (Fig. 1.38). Once all the echoes from this group are detected, an adjacent group of elements is activated. This is achieved by dropping an element from one end of the old group and adding a new one at the other end (e.g., 2, 3, to 21), and so on. The last beam is generated using elements 237–256, and therefore the image is constructed using a total of 237 scan lines. There is no steering of the beam in B-mode imaging for linear arrays, so all the scan lines are parallel to the transducer face (Fig. 1.38), and the image shape is rectangular. There are modes that will be discussed later in this chapter that require steering (Fig. 1.39), where a number of elements generate a steered beam. This occurs in pulsed Doppler mode, where the direction of the B mode beams is unchanged, but the Doppler beam may be steered to provide the appropriate angle between the beam and a blood vessel. In color Doppler mode, all the elements may generate a steered beam to achieve an appropriate Doppler angle while keeping the B mode lines unchanged. In compound imaging, several B mode images are created, each with a different beam-steering direction, which are then summed.

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Array transducers provide focusing on the scan plane but even today use a lens to achieve focusing along the elevation plane, which is the plane perpendicular to the scan plane (Fig. 1.24). This figure shows the (x, y, z) coordinates and the spherical polar coordinates (r, θ, ϕ) of a point P. The scan plane is the x-z plane, and the z-y plane is the elevation plane.

Transducer Selection A medical ultrasound machine is equipped with multiple probes for different clinical applications. The standard probes include linear array, curvilinear array, and phased array (Fig. 1.40).

Signals

n = 256-512

As discussed in the previous section, the image generated by a linear array provides a rectangular FOV. A curvilinear array functions as a linear array. However, owing to the probe curvature, the beams are not parallel but change direction as they step along the transducer face. Therefore, there is a radial component to its scan pattern. This type of probe provides a wider FOV than the linear array. In a phased array, the point of origin of the beam remains fixed, but the beam is steered in a number of different directions. The resulting image provides a good FOV at depth, but practically no information about superficial tissues. The selection of a particular probe depends on the organ(s) of interest and its depth from the probe face. The depth of penetration is inversely proportional to the frequency, and each transducer has a range of frequencies from which to choose. In general, the highest frequency transducer that permits adequate penetration to a tissue or organ of interest should be selected. Frequencies of 5 MHz or lower are useful for imaging organs such as the liver or kidney, while transducers with frequencies as high as 7–18  MHz are used to acquire high-resolution images of superficial structures such as muscle, tendon, testis, and thyroid. The neonatal brain can also be imaged at higher frequencies. The physical size of the probe, often called its “footprint,” and the available “acoustic window” into the patient, i.e., the area in the superficial tissues through which ultrasound can travel, are also important. Linear arrays tend to have higher frequency and are used for superficial structure imaging and biopsy. Their FOV is limited by the probe size. Curvilinear arrays tend to have a lower frequency and are used to image structures at depth. The FOV diverges with depth, so it is not so limited by probe size. When the acoustic window is

Fig. 1.39  Steered beam generated by a group of active elements in a linear array transducer Sector Arrays

Linear Array

Curvilinear Array

Narrow FOV Superficial imaging High frequency Biopsy guidance

Wide FOV Imaging at depth Low frequency Abdominal imaging

Phased Array

Small footprint Variable frequency Cardiac imaging

Fig. 1.40  Diagram of standard ultrasound probes, including linear array, curvilinear array, and phased array. FOV, Field of view

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23

extremely limited, as, for example, when imaging the heart, phased arrays are used.

Harmonic Imaging It was stated above that the transmitted ultrasound pulse travels at the average speed of sound in soft tissues (Fig. 1.15). It was also implicitly assumed that although the pulse is attenuated and that its amplitude decreases as it propagates in tissue, its shape remains the same. This description of wave propagation is from linear acoustics and is a very good approximation to reality when the wave intensity is small. At higher wave intensity, however, this assumption breaks down and nonlinear propagation effects become noticeable. One of these effects, which is at the foundation of harmonic imaging, is pulse distortion. In reference to Fig. 1.15, the wave intensity is highest in the central portion of the pulse (i.e., at the highest crest and lowest trough). The change of shape of the pulse is due to the fact that tissue becomes stiffer where the pressure is highest and more elastic where the pressure is lowest. When tissue stiffness increases, the propagation speed c increases and when the tissue becomes more elastic, speed c is reduced. As a consequence, the crests will travel a bit faster and the troughs a bit more slowly, causing the pulse to become increasingly distorted as it travels. This distortion occurs only in those regions where the pulse intensity is the highest, i.e., along the beam axis. Another important point is that the distorted pulse has a different spectrum than the transmitted pulse. As discussed above, the transmit pulse is composed of a contin-

f0

Frequency

Fig. 1.41  The left panel shows a simulated image of the transmitted beam in the scan plane with a central transmitted frequency f0. The beam shows a main lobe and side lobes. The highest intensity (dark

uous sum of sinusoidal waves with a central frequency f0 and a bandwidth 1/τ. When the pulse becomes distorted, harmonics of the central frequency (integer multiples of the central frequency): 2f0, 3f0, and so on, are generated. If, for example, the central frequency is f0 = 4 MHz, the second harmonic is 8  MHz, and the third harmonic is 12  MHz. The spectrum of the distorted pulse shows the frequency f0 and associated bandwidth, a frequency 2f0 and associated bandwidth, and a frequency 3f0 and associated bandwidth, and so on. The central frequency carries the most energy and the harmonics carry increasingly less energy. If the transmitted pulse is distorted as it propagates in tissue, the echoes caused by the interactions of this pulse with tissue structures will also be distorted. As a consequence, the distorted echo will also have harmonic components. In practice, the second harmonic is the most important harmonic since it carries the most energy and is the least attenuated while the other harmonic components are not considered. However, in keeping with the prior discussion, echoes will have a significant second harmonic component only where the intensity is high and therefore near the axis of the main beam. Figure  1.41 shows a simulated ultrasound beam with a main lobe where the intensity decreases away from the beam axis and side lobes. The dark red region near the central axis is where the intensity is the highest. Only the echoes coming from this region have a significant harmonic component. This fact is exploited in harmonic imaging, where an image is formed with echoes at the second harmonic 2f0 of the central transmitted frequency f0. If, for example, the machine transmits a 4  MHz central frequency, the harmonic image will be created with echoes at 8 MHz.

f0 2f0

Frequency

red) is near the central axis of the beam. The right panel demonstrates the portion of the beam near the central axis that has the highest second harmonic component

24

In harmonic imaging, a broad bandwidth transducer is used to transmit the central frequency and receives both the central and the second harmonic frequencies. A filter is then applied to remove the echo signal at the fundamental frequency and to preserve only the harmonic component for image formation. Tissue harmonic imaging (THI) increases image quality by suppressing weak echoes caused by artifacts and thereby improving the signal-to-noise ratio (SNR). This improvement occurs for two main reasons. First, the weak echoes arising away from the axis of the main lobe and from the side lobes and the slice thickness do not contribute significantly to the harmonic image. Therefore, beam-width, side lobe, and slice thickness artifacts are significantly reduced. Second, the transmit pulse becomes gradually distorted as it propagates through tissue. In superficial tissue (up to 1 or 2 cm depth), the transmitted pulse has not yet developed a significant distortion. This means that the echoes coming from these superficial tissues contain little energy at the second harmonic and consequently reverberation artifacts (discussed in a later section) are reduced. In addition, an improvement in spatial resolution is to be expected with harmonic imaging since the image is formed at twice the central frequency. Harmonic imaging has the drawback of decreased penetration. The second harmonic frequency is higher than the central transmit frequency, hence it undergoes greater attenuation, and the depth of penetration is reduced.

D.-S. Kim et al.

Fig. 1.42  Diagram of a compound scan. Several images are formed from different scanning angles and combined to form a single compound image

Spatial Compounding Spatial compound imaging mode is widely used with array transducers. Array transducers have the capability of electronic steering of the ultrasound beam to image the same tissue multiple times along different directions. The beam steering produces a set of images with a different lateral angle. The echoes from these multiple images from different scanning angles are compounded into a single image (Fig. 1.42). The operator can change the number of images used to form the compound image. Spatial compounding significantly improves the contrast-­ to-­noise ratio (CNR) and the definition of tissue boundaries by reducing the level of speckle, noise, clutter, and refractive shadows (Fig. 1.43). As a result, artifacts such as enhancement from weak reflectors and shadowing from strong reflectors are reduced. When a target is imaged from different approaches, it appears at the same point in the final compound image, but noise and speckle are uncorrelated from image to image and tend to cancel out, thereby improving contrast. Averaging these images will theoretically increase the SNR by a factor of n with n equal to the number of images.

Fig. 1.43  Spatial compounding. The combination of several images from different scanning angles generates a compound image that better displays the boundaries of a given structure

Better delineation of tissue boundaries, particularly of curved boundaries such as blood vessel walls, can be understood as follows: due to reflection, only the portion of a vessel wall that is perpendicular to the transmitted beam will generate a strong echo. Echoes from parts of the wall at other angles relative to the beam will be reflected away and will

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25

sound imaging is useful for depiction of fetal anatomy, cardiac imaging, gynecologic scanning, and virtual endoscopy. In conventional 2D imaging, an image is formed by acquiring echoes from a slice of tissue. The operator scans an ROI, often changing the probe orientation. Some examples of scanning techniques for imaging different parts of the body are shown in Fig. 1.44. By sweeping the probe through an ROI, the operator can form a 3D image of a particular structure or lesion. With 3D imaging, echoes from a volume of tissue are Three-Dimensional Ultrasound acquired automatically. The sequence of 2D images and the Three-dimensional (3D) ultrasound is used for viewing a vol- information about the position of each image in the scanned ume of interest by combining multiple scan planes, as well as region are stored, and algorithms are used to form a 3D view of for accurately estimating the volume of a lesion. 3D ultra- the ROI. This 3D view can be shown in a variety of formats. The 3D imaging systems available commercially can be divided into two groups depending on the ultrasound probe used: conventional probes and 2D array probes. The scanning methods used with conventional probes are free-hand and mechanical. Electronic scanning is used with 2D array Musculoskeletal probes. The 3D image can be rotated through different planes to be viewed from many angles. In free-hand scanning, the imager manually sweeps the transducer across the volume of interest with or without a position-sensing device. Free-hand scanning permits ­imaging Intravascular of a large volume, but measurements of distance, area, and/ Transrectal or volume are generally not as accurate as other scanning methods. Mechanical scanning employs a phased array mounted in an assembly, which mechanically oscillates in a sector movement or translates linearly over the body surface. Images acquired by the latter technique provide better resolution and accurate 3D reconstruction since the acquired 2D images are parallel to one another, and their intervals are well defined. In electronic scanning, a 2D array probe is used to directly Ocular image a 3D volume. A 2D array probe contains several thousand square elements arranged in a two-dimensional array. Without moving the array, the 3D volume is built up by electronic steering of the beam through the volume of interest to produce a pyramidal 3D view (Fig. 1.45). With a matrix probe, it is possible to achieve equivalent resolution in the scan and Cardiac (transcostal) elevational planes by applying the same degree of electronic Cerebral (transfontanelle) focusing and aperture control to both planes. Simultaneous data acquisition from each image plane enables a real-time 3D image display. The process of turning a volume of data into an image is Fig. 1.44 Scanning techniques for acquiring conventional two-­ referred to as rendering. As with computed tomography (CT) dimensional (2D) images. For musculoskeletal imaging, the scan plane and magnetic resonance (MR) imaging, three types of renis translated along an axis perpendicular to the plane and passing through its center, sweeping a cuboid volume. For intravascular and dering are implemented in 3D ultrasound imaging: multiplaintrarectal applications, the scan plane is translated in the same way, nar reformatting, volume rendering in the form of maximum sweeping a cylindrical volume. For ocular applications, the scan plane projection, and surface rendering. is rotated through a vertical axis located at the center of the scan plane, In multiplanar reformatting, a plane within the volume of sweeping a cylindrical volume. For cardiac and cerebral applications, data is chosen by the operator and the machine generates an the scan plane is rotated through a vertical axis located at one edge of image from the echoes lying in this plane. In maximum prothe scan plane, also sweeping a cylindrical volume

Rotational

Translational

not be seen. By combining images of the vessel taken at different angles, the boundary of the target will be better displayed in the compound image. The drawback of this mode is a reduced frame rate. Because of the improved CNR, spatial compound imaging is often used for imaging peripheral blood vessels and for musculoskeletal applications.

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2D Array Transducer

Rendering Planes

x

y

C-Scans B-Scans

Fig. 1.45  Diagram of a 2D array transducer that produces a pyramidal 3D view. Volume data can be displayed as a series of B-scan planes, as C-scan planes or rendering planes

Fig. 1.46  The Doppler effect is illustrated with a point source (target, black dot) and a transducer. (Top) When the target is stationary, the transmitted and reflected pulses have the same central frequency. (Middle) When the target is moving toward a stationary transducer, the

central frequency of the reflected pulse is higher than the central frequency of the transmitted pulse. (Bottom) When the source is moving away from a stationary transducer, the central frequency of the reflected pulse is lower than the central frequency of the transmitted pulse

jection, the machine software divides the volume of data into view lines and for each line selects and displays the strongest echo. In surface rendering, the most significant echo for each line is chosen and displayed. The machine then highlights the chosen echoes, permitting visualization of a surface of interest such as the fetal face. Repetitions of the 3D acquisition and their display at a low frame rate can be performed with 2D array transducers and is referred to as four-dimensional (4D) imaging.

Doppler Ultrasound When a detector and a source of waves move relative to each other, the observed frequency is not the same as the frequency emitted by the source. When the source (target) of the ultrasound waves moves toward the transducer, the frequency detected by the transducer is higher. Conversely, when the target is moved away from the transducer, the observed frequency is lower (Fig. 1.46). In ultrasound imag-

1  Ultrasound Imaging Techniques and Artifacts

27

ing, when sound is reflected off a moving object such as flowing blood or moving tissue, it undergoes a shift (i.e., change) in frequency. Doppler ultrasound is widely used to detect blood flow. More specifically, the Doppler frequency shift is used to obtain information about the presence, absence, direction, velocity, and temporal change of flow in blood vessels. The only components of blood that scatter ultrasound are the red blood cells, but the echoes that they produce are generally very weak and not normally detected on B-mode imaging. However, when the machine operates in Doppler mode, it can detect this frequency shift and therefore detect blood flow, particularly in the largest blood v­ essels. Doppler modes include continuous wave (CW) Doppler, pulsed wave (PW) Doppler, color Doppler, and power Doppler. The change in frequency between the transmitted and received frequencies is called the Doppler frequency shift (also known as the Doppler shift or Doppler frequency), FD. The Doppler shift can be calculated by subtracting the frequency of the transmitted beam, FT from the frequency of the received beam, FR, and can be expressed as: FD = DF = FR - FT =



u

Fig. 1.47  Diagram of ultrasound transducer emitting a sound wave that impinges on a blood vessel at angle θD. Blood flows within the vessel at velocity υ

2 FT v cos q D c

(1.19) where v is the speed of the moving object such as blood, and θD is the Doppler angle defined as the angle that the beam axis makes with the direction of flowing blood (Fig. 1.47). Velocity is a vector and therefore has a direction in space and a magnitude. The speed is the magnitude of the velocity and is always a positive number. The factor 2 in Eq. 1.19 is due to the fact that sound travels a round trip from the transducer to the blood vessel and back to the transducer. The Doppler shift is determined by both the speed of the red blood cells in the interrogated vessel and the angle the blood vessel makes with the ultrasound beam axis. The speed of a moving object is calculated from the measured Doppler shift and Doppler angle by rearranging Eq. 1.19: v=

θD

FD c 2 FT cos q D

(1.20)

There is no Doppler effect when there is no flowing blood. When blood is moving toward the transducer: θD  =  0, the 2 v FT Doppler shift is maximum: FD = (positive velocity) c and when it travels away from the transducer, the Doppler shift is minimum FD = - 2 v FT (negative velocity) (Fig. 1.48). c For example, if blood is moving toward the transducer at a speed of 100 cm/s and the transmitted beam has a central frequency of 4 MHz, then the Doppler shift is 5.2 kHz; if blood is moving away from the transducer, the Doppler shift is –5.2 kHz. This frequency falls within the audible range of the human ear. More generally, within the range of observed blood speeds, the Doppler shift usually falls in the audible range. Therefore, listen-

a

Stationary target: (FR – FT) = 0

b

Target motion toward transducer: (FR – FT) > 0

c

Target motion away from transducer: (FR – FT) < 0

Fig. 1.48  No Doppler shift is detected when blood (red blood cells) is not flowing. Detected frequency FR is slightly higher than transmitted frequency FT when blood is flowing toward the transducer, and slightly lower when it is moving away from transducer

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FT FT

FR

FR θ

u

u

Beam axis

Beam axis

∥ ∥



a

b

Fig. 1.49  Blood flow generally occurs at an angle relative to the ultra sound beam axis, the Doppler angle θD. The blood velocity v can be considered as the vector sum of two vectors: to the beam  one  parallel  direction and the other perpendicular to it: v = v + v^. The component of velocity along the direction of the ultrasound beam is v cos θD, which

θ = 60° cos θ = 0.5 ∆F = 0.5

θ = 90° cos θ = 0.0 ∆F = 0.0

θ = 0° cos θ = 1.0 ∆F = 1.0

Fig. 1.50  Diagram illustrating the effect of the Doppler angle on the frequency shift. The frequency shift is decreased in proportion to the cosine of the Doppler angle. At an angle of 90 degrees, there is no relative movement of the target toward or away from the transducer, and no frequency shift is detectable. At an angle of 60 degrees, the detected frequency shift is half that at an angle of 0 degrees. For a transducer with central frequency 4 MHz, the Doppler shift is 5.2 kHz at θ = 0, 2.6 kHz at θ = 60°, and 0 at θ = 90°. ∆F = frequency shift

ing to the Doppler shift can provide useful information in addition to analyzing images. The Doppler shift is determined by both the blood speed and the angle the blood flow makes with the beam

 is the magnitude of the vector v . In (a), this component points away from the transducer. In (b), it points toward the transducer. The frequency of the reflected sound beam is reduced in proportion to the cosine of θ. FR, Reflected frequency; FT, transmitted frequency; v, velocity

axis (Fig. 1.49). Figure 1.50 shows the Doppler shift for several angles: at θD = 0, the blood is moving toward the transducer and the Doppler shift is maximum; at θD = 60°, cos 60° = 0.5 and the Doppler shift is half that detected at θD  =  0; and at θD  =  90°, no frequency shift should be observed since cos 90° = 0. In situations where blood flow direction can be estimated from B-mode images, the operator activates the Doppler mode (e.g., PW Doppler) and places the angle marker in the direction of the blood flow within the Doppler sample volume. The ultrasound machine then calculates the Doppler angle and the blood flow velocity. There is some uncertainty associated with this calculated value due to imprecision in determining the exact direction of flow, subjectivity in placement of the angle marker, and intrinsic spectral broadening, an artifact discussed later. The most important source of error is the estimation of blood flow direction. Flow is complex in blood vessels and not necessarily parallel to the vessel wall. However, in practice, the operator places the angle marker parallel to the blood vessel wall. The error in velocity is small when the angle θD = 0 and increases as a function of θD. For this reason, 60° is usually considered the largest acceptable angle for velocity estimation. For angles of more than 60°, the cosine of the Doppler angle changes significantly. In echocardiography, angles close to zero are common, but for other applications, angles close to 60° occur more often.

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29

Continuous Wave Doppler CW Doppler is the simplest Doppler device and is typically housed in a handheld unit with an integrated speaker, such as those used in obstetrics for fetal heart monitoring. CW Doppler units operate at low acoustic power levels, are relatively inexpensive, and are easy to use with minimal training. The transducer is kept stationary over the ROI, and a sinusoidal ultrasound wave is transmitted continuously. The transducer contains two piezoelectric elements: one element to transmit sound waves (FT) and the other to receive the returned echoes (FR). This separation is necessary because ultrasound is transmitted continuously. The two elements are slightly tilted toward each other to allow overlap between the transmit and receiving beams (Fig. 1.51). Only blood and tissue within this sample volume are exposed to the transmitted ultrasound and “listened” to by the receiving element, and therefore, the Doppler shifted echoes are only detected for this region. The region where the two beams overlap is termed the sensitive volume or sample volume. In a typical CW Doppler device, the transmitter sends a CW signal with frequency FT  to both the transmitting element and the detector. The detector calculates the difference between the echo signal with frequency FR (detected by the receiving element) and the transmitted signal, to output a signal at the difference frequency (beat frequency): the Doppler shifted frequency FD. After wall filtering, where part of the signal with a frequency below the filter cutoff is removed, the Doppler signal is sent to a loudspeaker for monitoring. The primary function of the wall filtering is to remove echoes from moving tissue. In echocardiography, the CW Doppler device is built into an ultrasound machine, and the signal is processed to generate a Doppler spectral display, which is described below. Spatial resolution is degraded in CW Doppler because time-localized pulses are not used. In addition, CW sample volume is generally quite large.

T

R

Fig. 1.51  Diagram of a continuous wave (CW) ultrasound transducer. There are two piezoelectric elements, one to continuously transmit sound waves (T) and the second to continuously receive the reflected echoes (R). The two elements are slightly tilted toward each other to permit overlap between the transmitting and receiving beams

Range gate

Pulsed Wave Doppler

Fig. 1.52  Diagram of a pulsed wave (PW) Doppler device. Following transmission of a short burst of sound waves, the device listens for the returning echoes before generating another burst. The received signals can be electronically gated to detect echoes within a short time interval that corresponds to a specific depth

In contrast to CW Doppler, with PW Doppler it is possible to more accurately define the sample volume, typically with dimensions of several mm. Since PW Doppler is used in combination with B-mode, the sample volume can be accurately positioned on the B-mode image. If the direction of the blood flow is known, the ultrasound machine can estimate the Doppler angle and therefore determine blood velocity. As with B-mode, PW Doppler is based on the pulseecho principle and can therefore determine the depth of the structure causing the echo. The operator places the sample volume within the vessel. This allows the machine to calculate the beam direction and the depth of the sample volume.

If angle correction is applied, the Doppler angle can be calculated. The machine then generates a short pulse of ultrasound to transmit and collect the echo signal within a short time interval of 1 to 2 μs, the range gate. Echoes that arrive before and after the range gate are ignored. The time of initiation of the range gate is calculated by the machine to ensure that the echoes are coming from the correct depth. A schematic diagram of a range gate is shown in Fig. 1.52. The axial length of the sensitive volume can be as small as 1 mm. For each sample volume, this process of transmit and receive is repeated at regular intervals. This

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process is similar to B-mode except that the beam does not move. The number of transmit-receive cycles in one second defines the Doppler PRF. The sequence of echoes collected within a sample volume is combined in one PW Doppler signal. This signal is then wall-filtered to remove noise caused by tissue movement and is sent to a loudspeaker for monitoring and processed to generate a spectral display. An example of a spectral display in Fig.  1.53 shows a distribution of velocities as a function of time. When flow is toward the transducer, by convention the spectral display is placed above the reference line of 0 cm/s. When flow is away from the transducer, the spectral display is placed below the reference line. If angle correction is not applied, the machine assumes the Doppler angle to be zero, and the velocity readings are therefore incorrect. The left image (a) in Fig. 1.53 demonstrates spectral broadening with a beat frequency of varying amplitude that is caused by the fluctuation of the detected signal as red blood cells move in and out of the sample volume. Typically, a sample volume contains millions of red blood cells that do not move at the same velocity. The velocity is generally highest at the center of the blood vessel and falls to near zero close to the vessel wall. The Doppler signal reflects the range of red cell velocities within the sample volume. In the presence of disease, the blood velocity and its distribution can change. These changes alter the PW Doppler signal in a way that can be quantified in the spectral display. Intrinsic spectral broadening can also occur, which is an artifact. As with many artifacts, the cause lies in the idealized assumptions made by the machine. The ultrasound machine assumes the ultrasound beam to be a single line that originates from a single point on the transducer surface.

a Fig. 1.53  Normal spectral Doppler ultrasound signatures vary according to the vessel in question. (a) Spectral Doppler waveform from a normal main renal artery in an 18-year-old male demonstrates spectral broadening (between arrowheads). (b) Spectral Doppler waveform of

In reality, the beam has a finite extent and originates from a finite aperture, i.e., from a group of elements. The presence of this intrinsic spectral broadening causes a systematic error in every measurement of blood velocity. The greater the spectral broadening, the more the blood velocity is overestimated. In addition, when blood flow becomes turbulent because of disease, the spectrum has a wider range of Doppler shifts than found in a normal vessel. Intrinsic spectral broadening may mimic the spectral broadening due to disease. The lower and upper limits of the spectral display determine the maximum Doppler shift that can be correctly ­measured. These are the “Nyquist limits,” and their value is half the Doppler PRF. The Doppler PRF is also called the velocity scale because an increase or decrease will increase or decrease the range of Doppler frequencies or velocities that can be displayed. Additional operator controls include sample volume length that affects the range gate, Doppler gain, and the wall frequency cutoff. The power of the transmitted ultrasound is higher in PW Doppler than in B mode in order to increase the scattering signal from blood. This is generally achieved by transmitting longer pulses than in B mode. Although this process degrades spatial resolution, it has the advantage of increasing transmitted power without increasing peak pressure, which can be harmful to the patient. Another drawback of PW Doppler mode is that it is a timeconsuming process to examine a vessel since only one sample volume at a time can be processed. The combination of real-time B-mode imaging with CW or PW Doppler is known as duplex Doppler sonography. It can be difficult to analyze blood flow in small organs using PW Doppler if only a standard grayscale image is used to identify the position of tiny vessels of interest.

b the upper abdominal aorta in the same individual reveals a clear “window” (arrowhead), indicating that all the blood cells in the sample volume are moving at the same speed, so-­called “plug” flow

1  Ultrasound Imaging Techniques and Artifacts

Color Doppler Color Doppler imaging, also known as color flow Doppler and color flow imaging, is a form of duplex Doppler that combines 2D grayscale imaging with the color mapping of flow information in real time, as seen in the color image of Fig. 1.54. Color Doppler is a technique that is complementary to PW Doppler. It can be used to locate blood vessels, to guide placement of the sample volume for PW Doppler, and to assess the vascularity of given organ or tissue. It is important to remember that at each point of a color Doppler image, the color represents the Doppler frequency shift and not blood velocity. In color Doppler mode, there is no audible sound or spectral display because of the way the Doppler color image is acquired. When initiating a color Doppler examination, the operator places a color box over the ROI. The machine creates a grayscale image and then acquires the color image by scanning the beam throughout the color box, collecting Doppler shift information along each scan line. This information is superimposed on the grayscale image to generate the color Doppler image. This entire process is repeated many times, according to the set frame rate. For each scan line, the machine creates a large number of sample volumes within the color box from top to bottom. As with PW Doppler, color Doppler uses a gating technique, but it is implemented differently since echoes from many sample volumes need to be acquired, processed, and displayed. To speed up the process of collecting echoes, only a small number of transmit pulses (typically 8) are used for each scan line, compared to PW Doppler that typically uses 128 pulses.

R

L

31

For each scan line, many range gates are simultaneously active, each collecting echoes from different depths along the scan line. For each sample volume on each scan line, the echoes coming from the eight transmit pulses are fast-­ processed to yield three Doppler parameters: the mean (average) Doppler shift, the variance, and the Doppler signal power. The mean Doppler shift determines which color is displayed at each point in the color box. It is proportional to the mean blood velocity within the sample volume and also depends on the Doppler angle at any particular point. By convention, shades of red are used to represent flow toward the transducer and shades of blue to represent flow away from the transducer. The color bar on the image indicates the amount of Doppler shift, ranging from more saturated shades of red and blue for low velocities to less saturated shades for higher velocities. Areas where flow is absent or too slow to be detected will appear dark. The range of Doppler frequencies that can be measured and displayed is determined by the Nyquist limit and is half the Doppler PRF. The velocity values displayed at the top and bottom of the color bar indicate what the blood velocity at the Nyquist limits would be if the Doppler angle were 0°. These values are therefore inaccurate unless the Doppler angle is about 0°. The variance is a measure of spectral broadening and is not usually displayed in the color Doppler images except for echocardiography, where large regions of increased spectral broadening are assigned a green color in the image. Compared to PW Doppler, color Doppler measures Doppler shifts less accurately because it cannot correct for Doppler angle, is less effective in removing noise caused by moving tissues, and is less able to detect slow-moving blood because the Doppler PRF has to be constantly readjusted. When the ROI is deep in location, the color Doppler FR can be low. The FR is improved by using a coarser line density and by reducing the size of the color box. Some high-end machines have the capability of generating a number of transmit beams simultaneously.

Power Doppler

Fig. 1.54  Transverse color Doppler ultrasound image of a varicocele in an 18-year-old male. Flow within the enlarged veins of the left-sided varicocele (arrows) is well depicted. Flow information is superimposed on grayscale images of the right (R) and left (L) testes

Power Doppler, also known as energy Doppler or amplitude Doppler, is a specialized form of color Doppler. Unlike color Doppler, power Doppler does not display the mean Doppler shift or direction of blood flow. Instead, it displays the power (strength) of the Doppler signal. The power of the Doppler

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facts and limitations than is color Doppler ultrasound which requires manipulation of more parameters. Applications of B-flow imaging include evaluation of blood flow in superficial vascular structures such as the carotid arteries [5] and liver [6]. Slow-moving blood is well depicted at B-flow imaging with high spatial resolution. Slow blood flow is not shown on Doppler ultrasound studies that use high-pass filters (also called wall filters) to remove the low-amplitude frequency shifts coming from slow movement of blood and soft tissue vibration around blood vessels. B-flow imaging does not provide information regarding velocity or direction of flow.

Elastography Imaging Fig. 1.55  Normal power Doppler ultrasound image of the kidney in an 11-year-­old male. Flow in small blood vessels is well depicted

signal is encoded in color which is then superimposed on a grayscale image as illustrated in Fig. 1.55. Power Doppler has several advantages compared to color Doppler, including greater sensitivity to flow, better edge definition, and depiction of the course of tortuous and irregular vessels. The power of the Doppler signal is proportional to the number of moving red blood cells. A map of perfusion can be formed by displaying the amplitude of signals coming from moving red blood cells in an ROI.  The power is displayed using a single color with a brightness scale reflecting amplitude. Some machines can provide information about the blood flow direction with directional power Doppler images. Power Doppler is efficient in detecting low velocity flow in small vessels because it is easier for the ultrasound machine to detected signal power than the mean Doppler shift when the echo is weak. Power Doppler is therefore the preferred Doppler mode when weak signals need to be detected and displayed. Power Doppler can also detect flow when the Doppler angle is 90° and there is theoretically no Doppler shift. This is due to the spectral mirror artifact, discussed later in this chapter. Power Doppler is not affected by aliasing, except when the directional power display is used. The main limitation of power Doppler is its extreme sensitivity to motion.

B-Flow B-flow imaging, or B-mode flow imaging, is a non-Doppler technique that produces real-time imaging of blood flow during grayscale B-mode ultrasound imaging. B-flow imaging is relatively simple to perform and is less prone to various arti-

Ultrasound elastography imaging generates images of tissue elasticity [7–9]. It is an emerging technique that is currently under evaluation in clinical practice. Ultrasound elastography exploits the fact that diseased tissues often have different elasticity than healthy tissues. For example, cancerous tissue is usually stiffer than normal tissue as the density of cells and blood vessels is higher. The two main elastography methods currently implemented clinically are (1) quasi-static strain elastography and (2) dynamic elastography that applies a time-varying force to tissues. The main clinical applications of ultrasound elastography to date have been for imaging the stiffness of the liver and breast.

Quasi-Static Strain Elastography In some quasi-static strain elastography methods, the ultrasound probe is used to induce a quasi-static tissue deformation. Deformation occurs along the three spatial directions although the largest deformation occurs along the direction of the applied force, which is the direction of ultrasound beam propagation. Soft tissue is difficult to compress but easy to deform. As a result, a deformation applied to a soft tissue mainly causes a change in tissue shape, while the volume remains nearly unchanged. This is the reason why soft tissues are considered nearly “incompressible,” and the soft tissue bulk compressional modulus, which characterizes the volume changes of a tissue in response to compression, is generally several orders of magnitude larger than the shear modulus, which describes how a tissue responds to a shear (transverse) force. Given a lesion of volume V and surface area A, the application of a force per unit area of lesion (known as stress) results

1  Ultrasound Imaging Techniques and Artifacts

x

33

x’

y

y’

x=y

x’ < y’

Precompression

Compression

a

Shear waves

b

Fig. 1.56 (a) Quasi-static compression of two identical-­sized lesions of different stiffness. The quasi-static compression decreases the axial length of both lesions, with x’  x’. Strain images are obtained by comparing the echo signals from the lesion and surrounding tissue before and after



e=

=

34

Diagnosis by means of a color pattern is subjective, although strain images can also provide numerical values such as the strain ratio and the length ratio. The strain ratio represents the hardness of the lesion and is defined as the strain of the reference tissue region divided by the strain of the lesion. A soft lesion is deformed more than the surrounding tissue, and therefore its strain ratio is less than one. A hard lesion is deformed less than the surrounding tissue, and therefore its strain ratio is greater than one. The length ratio, elastography image size (EI) to B-mode (B) ratio, or EI/B ratio, is the ratio between the maximal horizontal or vertical length of the lesion measured at elastography imaging and the corresponding length measured in B-mode imaging. With some clinical ultrasound equipment, the probe is not used to apply a stress but instead just touches the skin with deformation caused by involuntary muscle contraction in the hand of the operator and vibration caused by muscle contraction and breathing of the patient. However, adequate elastography images cannot always be obtained for deeper lesions with this method. The main limitation of this technique is that the unknown stress that is applied affects the elasticity image and consequently the elasticity score, strain ratio, and length ratio. Another limitation is that selection of the images for elasticity evaluation is user-dependent.

Dynamic Elastography Dynamic elastography methods exploit the radiation force generated by the ultrasound beam. Two main techniques have been implemented clinically: acoustic radiation force impulse (ARFI) [14] imaging and shear wave speed imaging (SWI) [15–17]. ARFI, also known as qualitative ARFI, exploits the radiation force induced by a focused ultrasound pulse of high mechanical index (MI) (1.5–3.0) and longer duration than B-mode pulses: 0.1–0.5 msec. At the focal spot, the radiation force produces a displacement peak in the axial direction of about 10–20 μm, with the tissue returning to its resting position within about 5  msec. The axial tissue displacement is then determined using speckle-tracking algorithms as for strain elastography. ARFI produces strain images of the focal spot, enabling the imaging of lesions located at deeper depths. The same probe is used to generate the pulse to image an ROI, a high MI pulse to displace the tissue in the focal zone (called a “pushing pulse”), and a second imaging pulse to record the position of the displaced tissue. By sequentially interrogating different scan lines, a 2D strain image is created. The “push” pulses are of longer duration than standard diagnostic pulses, and this has the disadvantage of increasing the acquisition time and the deposited energy in the tissue, which can lead to heating. For this reason, images are acquired at relatively low frame rate which reduces temporal resolution.

D.-S. Kim et al.

SWI techniques rely on the detection of shear wave propagation for estimating tissue stiffness. Shear waves are easily generated by the application of either a transient or oscillatory force to deform tissue. Unlike longitudinal ultrasound waves, however, high-frequency shear waves are highly attenuated in tissue and cannot propagate. Low-frequency shear waves (10  Hz–2000  Hz) are less attenuated and can propagate in tissue, but at a much lower speed than longitudinal ultrasound waves between 1 and 50 m/s. Shear wave speed (cs) is related to the tissue shear modulus (µ), the tissue mass density (ρ), and Young’s modulus (E) by

m E (1.22) = r 3 r The Young’s modulus (E) is defined as the ratio between the applied stress and the resulting strain: E = stress/strain. Equation 1.22 provides a way for estimating tissue stiffness based on knowledge of the shear-wave speed. A number of techniques implemented clinically generate shear waves inside tissue using the radiation force exerted by a focused ultrasound beam. The deformation of tissue induced by the radiation force at the focal depth gives rise to a lowfrequency (sonic) shear wave which propagates primarily perpendicularly to the direction of propagation of the focused beam (Fig. 1.56b). For example, when determining ARFI shear wave speed (also known as quantitative ARFI), an ROI is chosen by the user from the B-mode image (Fig. 1.58). The user then activates a pushing pulse to generate the shear wave on one side of the ROI, which then travels through the ROI.  Time-offlight shear speed estimation methods using high-frame rate conventional B-mode imaging are employed to quantify the shear wave speed from the displacement data. These methods estimate the time of the arrival of the wave at multiple lateral locations and use this information to estimate the speed of the wave propagation between the locations. The shear wave cs =

Fig. 1.58  Hepatic fibrosis in a 12-year-old female with congenital heart disease palliated with a Fontan procedure. Transverse 2D shearwave elastography ultrasound image of the right lobe of the liver demonstrates an abnormally elevated shear-wave speed of 2.94 m/s

1  Ultrasound Imaging Techniques and Artifacts

35

a

b

Fig. 1.59 (a) Pushing pulses at different depths. (b) Supersonic images (SSI) of a cylindrical shear-wave propagating in a phantom at different times. The wavefront is distorted when passing through a harder inclusion (right image) since it propagates more quickly. The gray level indicates displacement in the phantom. (© 2011 Bercoff J.  Published in Bercoff [18] under CC BY 3.0 license. Available from: https://doi. org/10.5772/19729)

speed of the ROI is displayed, from which the operator can estimate the Young’s modulus using Eq. 1.22. Another technique is supersonic shear wave elastography (SSWE), which employs very high frame rates, up to 5000 Hz, to capture 2D images of the propagating shear wave. The word “supersonic” alludes to the way shear wave is generated. As with ARFI, a pushing pulse is used to generate shear waves. However, in SSWE, a number of pushing pulses are successively focused at different depths in an organ, generating a shear wave at each focal zone. If the focus is moved faster than the shear waves, the waves accumulate on the so-called Mach cone, generating two plane shear waves (Fig. 1.59). Immediately after generation of the pushing pulse, the machine sends out an imaging sequence at very high frame rates (5000 Hz) to catch the shear wave created by the pushing pulse. This imaging sequence consists of unfocused ultrasound beams (ultrasound plane waves) that spread over the ROI and record the resulting echoes which are used to form an image of the ROI.  From that sequence, the local shear wave speed and thus the Young’s modulus of the tissue are estimated. An example of an SSWE image of a breast mass taken at a very high frame rate (5000  Hz) is shown in Fig.  1.60, together with the corresponding B-mode image. The Young’s modulus (E) in kPa is shown with a color map. Transient elastography uses a vibrator in contact with the body to generate low-frequency spherical shear waves which are detected by an ultrasound transducer placed on the vibrator and operating at a very high frame rate.

Fig. 1.60 Supersonic shear-wave elastography of breast lesion. Lower image: BI-RADS category 3 lesion (probably benign) in B-mode. Upper image: In supersonic shear-wave elastography (SSWE), there is heterogeneous stiffness with a maximum Young’s modulus (E) of 180 kilopascals (kPa) (7.7  m/s). Biopsy showed invasive ductal carcinoma. From Berg WA, Cosgrove DO, Dore CJ, Schäfer FK, Svensson WE, Hooley RJ, et al. Shear-wave elastography improves the specificity of breast US: the BE1 multinational study of 939 masses. Radiology. 2012;262(2):435–49. [19]

Ultrasound Contrast Imaging Contrast Agents Ultrasound contrast agents (UCA) are gas microbubbles encapsulated by a thin shell made of protein, lipid, polymer, or surfactant. Most UCA range in size from 2 to 6 μm in diameter as illustrated in Fig. 1.61, and contain air or, more commonly, a low-solubility gas such as perfluorocarbon. UCA underwent significant development in the 1990s for diagnostic purposes and more recently have been investigated for potential therapeutic applications such as facilitation of ultrasound-mediated drug and gene delivery. In diagnostic ultrasound, microbubbles injected intravenously increase the echoes from blood vessels and flowing blood. Microbubbles are extremely powerful acoustic

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s­catterers owing to their impedance mismatch, resonance, and highly nonlinear behavior. At low-pressure amplitudes, microbubbles produce linear backscatter enhancement. As the power is increased, microbubbles scatter nonlinearly. It is the detection of these nonlinear components which forms the basis of contrast-­specific imaging techniques such as contrast harmonic imaging, pulse inversion imaging, and contrast Doppler, which are used to suppress tissue signals and enhance small blood vessel echoes. In therapy, microbubbles have been investigated for a number of potential new applications. Ultrasound enhanced

2-6 µm

Stable Gas

Biodegradable shell

Fig. 1.61  A microbubble contrast agent is a gas microbubble encapsulated by a thin biodegradable shell, ranging in size from 2–6 μm and containing a low-solubility gas such as perfluorocarbon

with microbubbles increases cell membrane permeability to large molecules (both drugs and genes) [20, 21], facilitates the delivery of large molecules to interstitial tissues [22–26], and promotes blood clot lysis [27]. Ultrasound contrast agents are used to improve imaging for applications such as echocardiography, liver, urinary tract, and transcranial color Doppler ultrasound.

Pulse Inversion Imaging Echoes from microbubbles contain harmonic components because they often scatter ultrasound nonlinearly. Harmonic imaging is therefore quite suitable for imaging UCA. In fact, harmonic imaging was originally developed for contrast-agent imaging under the assumption that tissue emits linear echoes and microbubbles emit nonlinear echoes. Pulse inversion imaging was developed in order to overcome the limitations of conventional harmonic imaging. In conventional harmonic imaging, the image is formed from echoes centered at twice the transmit frequency and uses these echoes to form the grayscale harmonic image. This approach fails when the frequency spectra of the fundamental and second harmonic overlap with each other. The only way to prevent overlapping is to use longer transmit pulses that keep the spectrum bandwidth smaller. However, longer pulses degrade axial resolution. Pulse inversion imaging can be used even when the frequency spectra overlap. The technique is illustrated in Fig. 1.62, where one incident pulse in B has the same wave-

Linear echo

Incident pulse

Nonlinear echo

t

t

+

t

t

+

t

t

Fig. 1.62  Diagram illustrating the principle of pulse inversion imaging. (A) A sound pulse enters the body and returning echoes are received from the contrast agent and the stationary tissues. (B) An inverted copy of the first sound pulse is transmitted in the same direction with result-

B

=

=

Sum, s(t)

A

t

t C=A+B

ing echoes. (C) The sum of the linear echoes from the stationary tissues are inverted copies of each other and their sum is zero. The even nonlinear components of the microbubble echoes produce a harmonic signal when summed

1  Ultrasound Imaging Techniques and Artifacts

length and amplitude as the pulse in A, but its phase is exactly inverted (180° out of phase). Upon reception, the echoes reflected from stationary tissues are linear and cancel each other out when added together. However, when microbubble contrast agents are present, they generate nonlinear echoes from harmonic scattering of moving targets. Pulse inversion imaging isolates this nonlinear echo to create a nonzero sum signal that depicts a real-time distribution and concentration of the microbubbles. Since two nonlinear echo signals are not completely out of phase, combining these echoes results in a high-amplitude signal. Pulse inversion imaging can be used with broadband ultrasound transmission and detection for improved axial resolution.

Ultrasound Artifacts An ultrasound artifact is any alteration of an image that does not represent the anatomy being scanned. Artifacts are more common in ultrasound imaging than in other imaging modalities. They can be related to the machine (faulty equipment, electrical noise) and to the operator (control settings not properly set). Certain artifacts are inevitable because of the nature of ultrasound-tissue interactions and the assumptions made by the machine about these interactions. Artifacts do not always contribute negatively to image interpretation and can often provide useful information. Understanding the cause and the generation of various artifacts can help an operator in arriving at a correct diagnosis. Several assumptions are made when creating ultrasound images that can result in image artifacts. These include the following: • The ultrasound wave travels at the same speed of 1540 m/ sec in all tissues. • The transmitted wave travels in a straight path from the transducer to the reflector and back to the transducer. • Attenuation of sound in tissue is uniform. • Each reflector produces only a single echo. • Beam dimensions are small in both the lateral and elevational directions. • All detected echoes originate from the central axis of the beam.

Grayscale Artifacts  irror Image: Multipath Reflection M Mirror image artifact (multipath reflection artifact) is produced when a structure is near a highly reflective interface such as the diaphragm (the interface between the chest and the abdomen), and can be imaged by reflected ultrasound. The geometry of reflection is simple, with the angle of incidence equal to the angle of reflection (see discussion of

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Reflection earlier in this chapter). Since the machine assumes that ultrasound travels in a straight line, the structure is displayed behind the interface and often at its true location as well (Figs. 1.63 and 1.64).

Refraction As previously discussed, refraction is a change in the direction of propagation of the incident ultrasound beam that occurs when it strikes a tissue interface at an angle other than 90°. As schematically shown in Fig. 1.13, refraction in ultrasound imaging results in apparent misplacement of a structure in an image from its true position. Refraction artifacts are frequent at the interface between soft tissue (c = 1540 m/sec) and fat (c = 1450 m/sec), or between soft tissue and fluid (c = 1480 m/sec).

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Fig. 1.63  Mirror image of the bladder caused by gas-filled bowel in a 7-month-old male. Longitudinal grayscale ultrasound image reveals bowel gas (arrowheads) that serves as a mirror to produce a reflection (asterisk) of the bladder (B)

S

*

Fig. 1.64  Mirror image of the scalp caused by the skull in a 3-month-­ old male. Transverse grayscale ultrasound image of soft-tissue swelling of the scalp (S) demonstrates a mirror image artifact (asterisk) deep to the bone (arrow)

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Two of the most common refraction artifacts are duplication refraction (ghost) artifact and refractive shadowing artifact. Duplication artifact usually occurs when the ultrasound beam is refracted from a superficial structure resulting in apparent duplication of a deeper structure. Refractive shadowing artifact (edge shadowing) is caused by loss of beam intensity due to defocusing at the edge of a cystic structure. Refractive shadowing appears as a linear shadow that differs from the shadowing caused by significantly reduced transmission. Refractive artifacts can be eliminated when the structure in question is scanned from different angles or by rotating the transducer. An example of refraction artifact is shown in Fig. 1.65.

 everberation, Comet-Tail, and Ring-Down R Artifacts Reverberation artifact is the production of multiple echoes generated from repeated reflections between two closely spaced interfaces. Reverberation often occurs when the acoustic impedance mismatch between two interfaces is high. The first transmitted pulse is reflected at the interface, received by the transducer and displayed in the image. Some of the echo energy returned to the transducer is reflected at the transducer surface and is redirected back into the patient, where it undergoes a second reflection at the same interface and returns to the transducer to be displayed on the image as another echo at twice the depth. The reflection and redirection of the initial transmitted pulse can occur multiple times at the same interface, and the sequence is repeated and displayed as a series of equidistant bands of decreasing brightness (intensity) (Fig. 1.66). a

Fig. 1.65 Rectus muscle refraction artifact in a 17-year-old male. Transverse grayscale ultrasound images of the mid-abdomen. When the transducer is positioned (a) in the midline there is an apparent duplica-

Fig. 1.66  Reverberation artifact from bowel gas in a 22-month-old male. Transverse grayscale ultrasound image of the right upper quadrant of the abdomen reveals a bright linear echo near the ultrasound transducer caused by intraluminal bowel gas (arrows). Repeated reflection of sound waves between the parietal peritoneum of the abdomen and gas in the bowel lumen results in multiple evenly spaced linear artifacts at increasing depth (arrowheads)

b

tion (arrowheads) of the superior mesenteric artery (SMA) and aorta (arrows). When the transducer is positioned to the right of the midline (b), only a single SMA (arrowhead) and aorta (arrow) are visualized.

1  Ultrasound Imaging Techniques and Artifacts

The subcutaneous fat-muscle interface often generates reverberation artifacts. Two strong reflectors along a beam path can produce a series of reverberation artifacts (comettail artifact) with equally spaced bands, which is equivalent to the space between the reflectors (Figs. 1.67 and 1.68). Ring-down artifacts arise from from resonant vibrations within trapped tetrahedrons of air bubbles. They produce a continuous sound wave that appears as a series of parallel bands or as a streak deep to a focus of gas such as a pneumoperitoneum (Fig. 13.69a).

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 ide Lobe Artifact S Side lobes are inevitable and present with all transducers. Piezoelectric elements expand and contract not only in a thickness direction but also in a radial direction. Side lobes are emissions of low-amplitude energy that project radially from the axis of the main ultrasound pulse and are caused by the radial expansion and contraction of the piezoelectric elements. Side lobe artifact is caused by echoes received from the side-lobe energy, which are incorrectly placed on the image of the main beam because the transducer interprets all echoes as if they originated from the main beam. The intensity of side lobes is so weak (less than 10% of the main beam intensity) that they do not usually generate visible artifacts on soft tissue imaging. However, side lobe artifacts become more visible when a highly reflective object is located outside the main beam plane, such as a biopsy needle, or gas in the bowel that appears as a ghost image in the urinary bladder in the displayed image. An ex An example of refraction artifact ample of side lobe artifact is shown in Fig. 1.69.

Enhancement and Shadowing Attenuation Artifacts Enhancement and shadowing attenuation are the most prominent and useful artifacts in ultrasound imaging, frequently aiding in the characterization of a variety of lesions. Attenuation of Fig. 1.67  Comet-tail artifact arising from the gallbladder in a 3-month-­ ultrasound depends on the tissue through which it propagates. old male with cholesterolosis. Longitudinal grayscale ultrasound image Enhancement artifact, also called increased through-­ reveals numerous foci of reverberation artifact (arrowheads) along the transmission, appears when a focal lesion has a lower attenuainner aspect of the anterior gallbladder wall. These are due to the presence of cholesterol crystals that are highly reflective of the ultrasound tion than the surrounding tissue. The result is an area of increased beam

Fig. 1.68  Comet-tail artifact arising from inspissated colloid in a thyroid nodule of a 11-year-old female. Transverse grayscale ultrasound image of the right thyroid lobe reveals a small hypoechoic nodule containing a central echogenic focus with posterior reverberation artifact (arrow)

Fig. 1.69  Side-lobe artifact in the gallbladder of a 21-month-old male. Longitudinal grayscale ultrasound image shows intraluminal echoes (arrow) from an adjacent gas-containing loop of bowel (arrowhead)

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brightness behind a hypoechoic structure. Cysts and other fluidfilled structures such as the gallbladder are less attenuating than the surrounding soft tissues, so that the more distal tissues often produce brighter signals than those generated by similar adjacent tissues at the same depth. The degree of enhancement (brightness) can be controlled using TGC. Examples of enhancement artifact are shown in Figs. 1.70 and 1.71. Shadowing artifact appears as an area of decreased brightness behind a strongly attenuating structure such as a calcification, metallic foreign body, bone, and some solid masses. This artifact is caused by significant attenuation of the ultrasound by either absorption in the structure or reflection at an interface, and results in little transmission of sound, leaving a long dark shadow posterior to the structure. Examples of shadowing artifact are shown in Figs.  1.72, 1.73, and 1.74.

Partial Volume Artifact Partial volume artifact is also referred to as slice thickness artifact or beam width artifact, depending on the angulation

Fig. 1.70  Enhancement artifact associated with a breast cyst in a 16-year-old female. Longitudinal grayscale ultrasound image of the breast demonstrates a cyst (asterisk). There is a relative increase in the intensity of the echoes posterior to the cyst (arrows) compared to the adjacent soft tissues

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Fig. 1.71  Enhancement artifact associated with a Wilms’ tumor in an 8-month-old male. Longitudinal grayscale ultrasound image of the right kidney demonstrates a solid upper pole mass (asterisk). Increased intensity of echoes posterior to the mass (arrows) relative to the adjacent soft tissues is identified. The homogeneity of the solid mass results in a lower attenuation of the sound waves compared to the neighboring soft tissues

Fig. 1.72  Shadowing artifact from a kidney stone in a 16-year-old male. Transverse grayscale ultrasound image of the right kidney shows clean shadowing (arrow) deep to a large stone (asterisk)

1  Ultrasound Imaging Techniques and Artifacts

of the transducer relative to the scan plane. Partial volume artifact can appear in either an in-plane direction (lateral) or at 90° to the scan plane (slice thickness). This artifact is caused by simultaneous sampling of tissues with different acoustic properties when scanned with a beam width that is greater than the dimensions of the structure. It appears in

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the image as pseudo sludge or as echoes in an otherwise echo-­free area. A beam width artifact can be reduced by optimal positioning of the focal zone. A slice thickness artifact is integral to the transducer and cannot be entirely eliminated. An example of partial volume artifact is shown in Fig. 1.75.

Doppler Artifacts Artifacts in both spectral and color flow Doppler imaging are often classified as technically related and anatomically related artifacts.

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Fig. 1.73  Shadowing artifact due to bowel gas in a 17-year-old male. Longitudinal grayscale ultrasound image of the left upper quadrant demonstrates dirty shadowing (arrows) posterior to a gas-filled bowel loop (asterisk). The artifact is caused by sound wave reflections at the gas-­soft-­tissue interface

a

Fig. 1.75  Partial volume artifact of the bladder in an 8-day-old male. (a) Transverse grayscale ultrasound image reveals pseudo-­ sludge (arrows) in the posterior aspect of the bladder. (b) Transverse grayscale

Fig. 1.74  Shadowing artifact associated with renal angiomyolipoma in a 13-year-old female. Longitudinal grayscale ultrasound image shows a large echogenic mass (asterisk) in the lower pole of the right kidney. There is posterior acoustic shadowing (arrows) related to absorption of sound waves by fat in the tumor

b

ultrasound image obtained after repositioning of the focal zone closer to the posterior wall of the bladder resulted in complete elimination of the artifact

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a

b

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Fig. 1.76  Effect of gain settings on depiction of flow in the carotid artery of a 17-year-old male. (a) Longitudinal color Doppler ultrasound image obtained with a low gain setting (arrowhead) results in reduced detection of blood flow. (b) Color Doppler ultrasound image obtained with a high gain setting (arrowhead) leads to excessive electronic noise in the image (arrow). (c) Color Doppler ultrasound image with an appropriate gain setting (arrowhead) results in satisfactory depiction of uniform flow throughout the vessel

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Technically Related Doppler Artifacts Inappropriate Doppler Settings The most important controls for correctly displaying blood flow, especially for slow flow, are the gain, Doppler PRF (also termed velocity scale), filtration setting, and transducer focal depth. When the gain is too low (Fig.  1.76a), the very weak echoes from blood are too small to be detected. If the gain is too high, excessive electronic noise becomes visible in the Doppler image (Fig. 1.76b). The spectral Doppler gain setting should be adjusted so that the velocity envelope is thin, and flow is seen in a uniform direction (Fig. 1.76c). It is appropriate to adjust the color Doppler gain setting by increasing it to the point at which noise starts to appear in the image and then decreasing it until the noise just clears from the image or is barely noticeable. The Doppler PRF (number of pulses emitted per second), also called the velocity scale on some ultrasound machines, should be set as low as possible until aliasing, noise, or tissue motion (discussed below) becomes apparent. The Doppler signal contains not only the low-amplitude, higher Doppler frequencies from blood, but also the high-­ amplitude, lower Doppler frequencies from slow-moving tissues such as the vessel walls. The wall filter controls the ability to distinguish moving blood from moving tissue by removing the low Doppler frequencies while retaining the higher frequencies. There is, however, a compromise in the selection of the cut-off frequency to be used, as it is important not to suppress the low frequencies associated with slow velocity flow. A low filter setting increases the likelihood of low-velocity flow detecb

c

Fig. 1.77  Effect of wall filter settings on the depiction of renal blood flow in a 14-year-old female. (a) Longitudinal color Doppler ultrasound image of the right kidney obtained with a low filter setting (arrowhead) demonstrates color signal throughout the renal parenchyma. Depiction of the vasculature is limited by prominent color noise. (b) Image of the right kidney obtained with a high filter setting (arrowhead) has reduced

noise but prevents visualization of the smaller peripheral parenchymal vessels. (c) Image of the right kidney obtained several months earlier with a medium filter setting (white arrowhead) reveals peripheral parenchymal vessels (black arrowhead), as well as satisfactory depiction of the larger central vessels. Incidentally noted is a prominent color Doppler twinkling artifact (arrow) associated with a renal pelvic stone

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tion, but also contains noise (Fig. 1.77). A high-filter setting suppresses low-frequency shifts arising from slowly flowing blood. The Doppler transmit frequency to be used depends on the depth of the vessel. A high transmit frequency is more sensitive for detecting blood flow at the expense of penetration. If penetration is an issue, a lower transmit frequency should be chosen. Aliasing (Wraparound) For a given Doppler PRF (velocity scale), there is a limit to the maximum Doppler frequency shift that can be estimated and visualized correctly. This limit is known as the Nyquist PRF limit and is half the Doppler PRF: fD = . Since flow 2 velocity is proportional to the Doppler frequency shift (Eq. 1.20), increasing or decreasing the PRF (velocity scale) will increase or decrease the range of frequencies, and therefore the displayed velocities. The Nyquist limit is related to the ability of the Doppler processor to process the Doppler signal. If the Doppler frequency shift exceeds the Nyquist limit, the Doppler processor cannot reconstruct the signal correctly because the signal sampling rate is too low. Aliasing occurs for both PW Doppler and color Doppler when the Doppler shift frequenPRF cies exceed the Nyquist limit ( ). 2 In PW Doppler, aliasing can be seen as waveform peak cutoff with the peaks displaced below the baseline (Fig. 1.78). With color Doppler, aliasing can cause an abrupt change in color suggesting incorrectly that the direction of flow has

a

changed (Fig. 1.79). A true flow reversal is characterized by adjacent areas of dark red and dark blue. Color aliasing is a valuable artifact because it displays regions of high-­frequency Doppler shifts, which could potentially be sites of abnormal flow. Increasing the Doppler PRF can eliminate or reduce aliasing but at the expense of depth of penetration. If that is not possible, using a lower transducer frequency reduces the Doppler frequency shift, which can help to decrease or eliminate aliasing. Increasing the Doppler angle can also reduce the Doppler shift. However, this option is often not feasible because the acoustic window to the vessel is either too limited to allow angle variation, or because the angle is already close to 60° and cannot be increased any further. In echocardiography, CW Doppler, which is not affected by aliasing, is often used instead of PW Doppler. A major drawback is its relatively large sample volume. Color Doppler Noise Noise is often related to inappropriately high Doppler gain. A spectral gain setting that is too high degrades the velocity envelope, causing it to appear thickened. This appearance mimics spectral broadening. Spectral broadening is an important diagnostic indicator and has two causes. One is due to the fact that the Doppler sample volume contains a range of velocities, so the Doppler signal has a range of frequencies. In the presence of disease, the range of frequencies can increase, particularly when the blood flow becomes turbulent (e.g., post-stenotic turbulence). The other cause is intrinsic spectral broadening. The ultrasound beam used to acquire the Doppler signal is generated by a group of ultrasound elements. Therefore, the

b

Fig. 1.78  Pulsed wave (PW) Doppler ultrasound depiction of aliasing in the carotid artery of a 17-year-old male. (a) Longitudinal color and spectral Doppler ultrasound image of the carotid artery shows a low pulse repetition frequency (PRF; arrowhead) with aliasing of the arte-

rial systolic peaks that are displaced below the baseline. (b) Spectral Doppler evaluation of the carotid artery after increasing the PRF results in an appropriate display of the arterial systolic peaks above the baseline in the same direction as the rest of the arterial waveforms

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Fig. 1.79  Color Doppler aliasing in a 4-year-old male with mid-aortic syndrome. (a) Longitudinal grayscale ultrasound image shows marked focal thickening of the wall of the mid-abdominal aorta (arrows) with significant luminal narrowing. (b) Longitudinal color Doppler ultra-

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sound image reveals aliasing as foci of light blue color assignment (arrowheads) in the zone of luminal narrowing. Unlike true flow reversal, there is no separation of the red and blue hues by a black region without flow

Rapid movement of the transducer is another cause of a Doppler shift and artifactual color signal. Power Doppler is particularly sensitive to artifactual motion, such as movement of the transducer.

Fig. 1.80  Effect of insonation angle on the depiction of color Doppler flow in a 14-year-old female with heterotaxy and a left-sided inferior vena cava (IVC; arrows). Transverse color Doppler ultrasound image demonstrates a small colorless segment (arrowheads) in the vascular lumen where the interrogating ultrasound beam intersects the vessel at a 90-degree angle

Doppler signal is acquired by ultrasound traveling along multiple paths. For each of these paths, the Doppler angle is different, and so there will be a different Doppler shift. The overall Doppler signal contains a combination of all these Doppler shifts resulting in spectral broadening. When the color gain setting is too high, color signal appears throughout the image as a random admixture of red and blue (i.e., color speckles) rather than having a homogeneous color, which is typical of flow within a vessel. Any structure that moves can also cause a random Doppler shift.

Flow Directional Abnormalities The detected Doppler shift frequencies are dependent on the cosine of the angle of insonation (θ). As the Doppler angle approaches 90°, the Doppler signal can be very small and therefore may be removed by the wall filter. Flow direction can also be inappropriately displayed if the interrogating ultrasound beam intersects the vessel at a 90° angle. If a curved or phased array is used, every beam used to generate the image has a different angle and therefore a different Doppler angle. Hence, a range of color will be seen with a small colorless segment in the lumen of the vessel (Fig. 1.80).

Anatomically Related Doppler Artifacts Spectral Mirror Image Artifact This artifact, already discussed for grayscale imaging, also occurs in Doppler imaging. As with grayscale imaging, Doppler mirror images arise close to strongly reflecting interfaces which act as mirrors, causing a tissue or structure located above the interface to be replicated below the interface. If the region that is being mirror-imaged contains blood vessels, they will be displayed in the mirror image as shown in Figs. 1.81 and 1.82. Because the artifactual signal is generated by blood flow in a real vessel but is simply improperly positioned, it usually has the same size and shape as the signal from the true vessel. Its intensity, however, is often weaker. This is because the artifactual signal arises from the sound reflected off the mirror which

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A

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V

Fig. 1.81  Mirror image artifact of the subclavian artery in a 21-year-­ old female with thoracic outlet syndrome. Longitudinal power Doppler ultrasound image shows the left subclavian artery (A) with a mirror image (arrowheads) located inferiorly. The interface between the vessel lumen and the underlying lung tissue acts as a mirror in reflecting the incident sound

is weaker than the Doppler signal from the true vessel that arises from the original sound pulse. Scanning from an angle that excludes the source vessel or decreasing the power output and Doppler gain settings should eliminate or reduce the mirror image. Occasionally, weaker acoustic interfaces will act as mirrors for color Doppler imaging. For example, bone can reflect enough sound to produce color Doppler mirror images. Tissue Vibration Artifact Turbulent blood flow causes pressure fluctuations in the lumen of the vessel and vibration of the vessel wall, which generates a detectable Doppler signal. This signal is displayed as focal random red and blue color patches in the perivascular space at the site of the abnormal vessel. The artifact is most prominent during systole when the velocities are greatest, and less prominent during diastole. Waveforms from vibrating tissues are typically strong, low-frequency signals that are symmetric above and below the baseline. Perivascular tissue vibration artifact can be seen in any situation where there is sufficiently turbulent blood flow. The commonly encountered lesions include arteriovenous fistulas (AVF), stenotic arteries, aneurysms, pseudoaneurysms, and vascular anastomotic sites (Fig. 1.83). Twinkling Artifact Small calcified and crystalline structures can produce echoes that mimic movement. With color Doppler, they typically appear as a random mixture of red and blue colors fluctuating in time (Fig. 1.84). For this reason, this artifact is known as “twinkling” artifact. The associated waveforms show a high-­ intensity, non-physiologic signal with aliased components on both sides of the baseline. The artifact is typically accentuated at low transmit frequencies and high Doppler scale settings.

Fig. 1.82  Mirror image artifact of the right subclavian vein in an 18-year-old male. Longitudinal color Doppler ultrasound image depicts the normal right subclavian vein (V) with a mirror image (arrowheads) located inferiorly

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Fig. 1.83  Perivascular tissue vibration from an arteriovenous fistula in a 52-year-old female with recent cardiac catheterization for congenital heart disease. Longitudinal color Doppler ultrasound image shows a fistulous connection (arrows) between the common femoral artery (A) and vein (V) with adjacent tissue vibration artifact (arrowheads) manifested as a mixture of blue and red speckles

The twinkling artifact has been exploited most commonly in the detection of urinary tract stones. The twinkling artifact from urinary stones is likely generated by a random strong reflection and multiple inner reflections of the incident pulse at the rough interface formed by the crystalline aggregate.

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Fig. 1.84  Color Doppler twinkling artifact associated with a renal stone in a 23-year-­old male. (a) Longitudinal grayscale ultrasound image reveals a small echogenic focus (arrow) in the lower pole of the left kidney without posterior acoustic shadowing. (b) Longitudinal

color Doppler ultrasound image demonstrates a twinkling artifact (arrowheads) with alternating color signals extending posterior to the site of the echogenic focus in the lower renal pole

Fig. 1.85  Blooming artifact in a 2-month-old premature infant with vena caval thrombi. (a) Longitudinal grayscale ultrasound image reveals two linear echogenic thrombi (arrows) in the IVC. (b) Longitudinal

color Doppler ultrasound image displays color signal in the IVC that completely obscures the thrombi

Although the twinkling artifact is most often used to aid in detection of small renal calculi, it is also helpful in the setting of ureteral and bile duct stones, pancreatic calcifications, and foreign bodies. This artifact may be easier to detect than acoustic shadowing and is useful in stone identification.

may still detect the Doppler signal from the vessel. This occurs because the spatial resolution of color Doppler is lower than that of grayscale. The resulting image will display color Doppler signal in the pixels corresponding to the soft tissue, thus masking underlying grayscale information (Fig. 1.85). This can obscure abnormalities within the vessel lumen, such as nonobstructive thrombus or arterial plaques, as well as lesions in the tissues around the vessel.

Blooming Artifact When the ultrasound beam is centered on soft tissue that is within or immediately adjacent to a blood vessel, the beam

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Three-Dimensional Ultrasound Artifacts 3D imaging cannot fix the 2D ultrasound artifacts covered in Sections “Gray-Scale Artifacts” and “Doppler Artifacts”. If some artifacts are present in the 2D images, they will be also present in the volume of echo data. However, the artifacts present in the 2D images may be visible in a 3D image without the presence of the causative structure. This is because their presence may not be available in a specific image but will be expressed throughout the volume and present in multiple planes and rendered images. For example, the rendering of a shadow from an overlying structure such as bone or a calculus may be seen as a hollow void on a 3D image without the representation of the bone or calculus itself. Therefore, it is important to interpret 3D images in combination with 2D imaging to identify the origin of the artifact. There are artifacts that are unique to 3D volume acquisition and display processing. Manual acquisition of a volume of echo data by sliding the transducer can result in artifacts related both to the varying speed of transducer movement and some types of patient motion (respiration, cardiac motion, vessel pulsation, general patient movement) that occurs during the relatively long acquisition time. This can result in data volumes which do not correctly reproduce some of the object dimensions. Automatic volume acquisition with newer ultrasound probes has overcome this issue to a large extent. The post-processing of the volume of echo-data is quite complex and can generate several artifacts. The quality of the rendered images often depends on the choice of the rendering parameters such as threshold, opacity, lighting, and so on. The threshold parameter, which is used to define the level of gray voxels to be visualized, is a particularly important parameter. Excessive thresholding can remove part or all of an important structure. When the threshold parameter is set appropriately, it can minimize or eliminate noise and improve image quality.

Ultrasound Contrast Agent Artifacts Blooming Artifact In color Doppler mode, the injection of contrast agents can accentuate the blooming artifact described in Section “Doppler Artifacts.” It occurs soon after the administration of contrast agent at the time of peak enhancement. As the contrast agents enters a vessel, the magnitude of the echo increases with a correspondingly large increase in Doppler signal. This increase in signal can expand the width of the vessel, causing “blooming.” A slow injection limits blooming artifact because it decreases peak signal intensity.

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 ystolic Peak Velocity Increase S An artifactual increase in systolic peak velocity of up to 50% can occur at the time of contrast peak enhancement, reflecting the limited dynamic range of the system. This artifact can be minimized by reducing the Doppler gain and using a slow injection. The increased systolic velocity can potentially result in overestimation of the degree of a stenotic lesion if contrast images are interpreted without conventional color Doppler images. The presence of flow disturbances on the color Doppler images should help in grading stenotic lesions. High-Intensity Transient Signals High-intensity transient artifacts can be seen with pulsed Doppler at the time of peak contrast enhancement or during late enhancement. They can also be detected with color and power Doppler ultrasound as higher-intensity color pixels within the more uniform background of the vessel.

Ultrasound Safety Ultrasound imaging does not produce carcinogenic ionizing radiation and has an outstanding safety record. However, ultrasound strongly interacts with tissues and as a result may cause harm by increasing their temperature and through the exertion of mechanical forces. The changes that ultrasound can cause to a tissue are classified as thermal and nonthermal bioeffects [27–29].

Thermal Bioeffects The thermal bioeffects of ultrasound are primarily affected by the ultrasound frequency, beam intensity, transmit power (energy radiated by the transducer every second), scanning mode, and tissue absorption properties. As the ultrasound propagates through tissue, some energy is absorbed and converted into heat. Absorption increases with frequency and beam intensity. The absorption properties of the tissue also affect heating. Blood absorbs much less energy than bone or lung tissue. Other soft tissues fall in between with muscle having the highest absorption. Blood flow also affects tissue heating because it carries away heat. Well-perfused tissues heat up significantly less than poorly perfused tissues. Interfaces between soft tissue and bone are a particular concern as a large part of the ultrasound energy is reflected at these interfaces. This can cause substantial localized heating at these interfaces. Another important factor is whether the beam is scanned through the tissue, as it is in B-mode and color Doppler imaging, or whether it is stationary, as with PW Doppler and CW Doppler. When the beam is scanned, the heat is spread through a larger volume of tissue, reducing temperature

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increase. B-mode imaging is generally safe since it uses the lowest exposure parameters. Doppler imaging requires a higher transmit power than B-mode imaging to overcome low scattering from blood and therefore potentially poses more risk to the patient than B-mode imaging. PW Doppler has the highest risk of substantial tissue heating because it requires a higher transmit power, and the beam is kept stationary during acquisition. Even though the beam is kept stationary for CW Doppler, the risk is less because the pressure amplitude and therefore the intensity (which is proportional to the pressure amplitude squared) are kept lower than for PW Doppler. CW Doppler is a simpler technique than PW Doppler, and requires less transmit power than PW Doppler to achieve a comparable echo signal. The thermal index (TI) was developed to estimate the increase in temperature that might occur during an ultrasound scan. It is essentially a measure of the likely maximum temperature rise of the tissue during the scan. A TI of 0.9 implies an expected temperature rise of about 0.9 °C. TI is defined as the ratio of the acoustic power produced by the transducer (W) to the power required to raise the tissue temperature by 1 °C. Bone absorbs more heat than soft tissue. Two TIs have been defined for bone: (1) bone TI (TIB) that takes into account the extra heating that occurs at bonesoft tissue interfaces; and the cranial TI (TIC) when the probe is placed in proximity to the patient’s skull.

Nonthermal Bioeffects Cavitation is the most important nonthermal bioeffect of ultrasound. Acoustic cavitation describes the interaction of gas bubbles with a sound field. At low pressure amplitude, bubbles undergo stable cavitation, i.e., they oscillate, often nonlinearly, around an equilibrium position. They remain relatively stable in solution, and may oscillate for many cycles of the acoustic pressure. As the pressure amplitude is further increased, cavitation can become inertial. Inertial cavitation is characterized by the sudden expansion and rapid collapse of bubbles. The bubbles may fragment or repeat the growth/collapse cycle a number of times. Bubble collapse can create extremely high localized temperatures in the gas contained inside a contrast microbubble, while in the liquid surrounding the microbubble they can generate shock waves that produce harmful bioeffects. Inertial cavitation can also generate free ­ radicals within microbubble gas and at gas-liquid interfaces that can alter biomolecules such as DNA, proteins, and lipids. Cavitation is important because gas bubbles occur in areas such as the lungs and gastrointestinal tract. In addition, the

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risk of inertial cavitation increases as the peak negative pressure increases. The peak negative pressure, also known as rarefaction peak pressure, is the most negative pressure that occurs during an ultrasound pulse. In water, a sufficiently high negative pressure can pull apart molecules and create a gas bubble. If there are preexisting gas bubbles or dust particles in the water, cavitation also occurs more easily. A similar effect can also occur in tissue, especially if there are preexisting gas bubbles. The likelihood of inertial cavitation increases with decreasing ultrasound frequency. The MI quantifies the likelihood that exposure to diagnostic ultrasound will produce an adverse bioeffect by inertial cavitation. The MI is defined as the estimated peak rarefactional pressure in vivo, Pr, divided by the square root of the center frequency f of the beam: MI =

Pr



f

(1.23)

Regulations and Policies Ultrasound equipment sold in the United States (US) must meet the US Food and Drug Administration (FDA) regulations requiring that manufacturers supply information on acoustic power output and ensure that certain acoustic parameters do not exceed allowable levels. In 1991, The FDA set new regulations for the output of diagnostic ultrasound that has increased permissible output intensity for fetal, neonatal, cardiac, and ophthalmological applications. These new regulations superseded earlier ones established in 1976, which were more restrictive. Manufacturers generally provide real-­time on-screen display of acoustic power as Output Display Standard (ODS), as defined by the American Institute of Ultrasound in Medicine (AIUM) and the National Electrical Manufacturers Association (NEMA). Two main acoustic parameters of the ODS are the TI and MI as discussed above. Manufacturers are required to display the TI and MI during the scan whenever the probe-machine combination is capable of producing a value for either index greater than 1.0. In general, the following upper limits should be observed during an ultrasound scan: MI  2 cm in diameter. Type 2 has a frequency of 10–15% and is characterized by single or multiple cysts that are ≥ 0.5 cm but ≤ 2 cm in diameter. Type 3 has a fre-

Features Proximal bronchial anomaly and acinar dysplasia involving all pulmonary lobes Incompatible with life A single or multiple cysts that are > 2 cm in diameter A single or multiple cysts that are ≥ 0.5 cm in diameter and ≤ 2 cm Predominantly solid tissue with small cysts that are < 0.5 cm in diameter Large air-filled cysts that can be difficult to distinguish from type 1 lesions

quency of 8% and is characterized by predominantly solid tissue with small cysts that are 10 mm in thickness may be associated with substantial lung functional impairment and dyspnea [65]. On ultrasound, pleural fibrosis is initially hypoechoic and hypovascular, becoming heterogeneous (Fig. 6.20) and vascularized over time. Contrast-enhanced ultrasound (CEUS) may be helpful to differentiate complex fluid from fibrosis. Pleural calcifications may occur and are seen as hyperechoic deposits with acoustic shadowing. Lung decortication is performed if the pleural fluid is not adequately drained despite thoracentesis, thoracostomy tube drainage, and VATS, or if there is severe pleural fibrosis. Decortication involves removal of the thickened layer from the pleural surface [64–66].

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a

b

L

Fig. 6.20  Pleural fibrosis in an 11-year-old female with primary pulmonary tuberculosis. (a) Longitudinal grayscale ultrasound image of the right chest shows an echogenic pleural fluid collection (asterisk) with pleural thickening (arrows). L, Liver. (b) Coronal contrast-enhanced CT

a

image reveals markedly thickened pleura (arrows) with multi-loculated fluid in keeping with progressive tuberculosis, pleural dissemination and developing fibrothorax

b

L

L

Fig. 6.21  Hemothorax in a 6-month-old male with heterotaxy and recent cardiac surgery. (a) Longitudinal grayscale ultrasound image of the left chest shows clumping of echogenic material (asterisk) representing blood

clot. (b) Transverse color Doppler ultrasound image of the left chest demonstrates avascularity of the pleural collection. L, Liver

Traumatic Effusion

nary infarction, and post-pericardiotomy syndrome can also present with hemothorax. Pleural fluid analysis shows a hematocrit of more than 50% compared to that of peripheral blood [52, 56]. Ultrasound is a reliable tool for identifying hemothorax. An acute blood collection is usually echo-free, whereas old blood is echogenic, with clumping representing clots (Fig.  6.21). Hemothorax may show increasing echogenicity toward the

Hemorrhagic Effusion Hemothorax is the presence of blood within the pleural cavity, which is usually related to blunt or penetrating trauma. However, inflammation, malignancy, rupture of bronchopulmonary sequestration or arteriovenous malformation, spontaneous intrathoracic vessel rupture, pulmo-

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dependent part of the effusion (the “hematocrit” sign) due to a layering effect of the cells. Multiple thick septations can be seen with long-­standing hemothorax, similar to empyema. The affected child typically has a history of decreasing hemoglobin and hematocrit levels [2, 11, 49]. Hemothorax is usually managed by ultrasound-guided placement of a simple chest tube.

Treatment of extrapleural hematoma depends on the clinical status of the patient. A stable patient with a small hematoma can be managed conservatively. However, needle aspiration or thoracotomy may be needed to evacuate blood clots in a large extrapleural hematoma because of respiratory and circulatory compromise.

Extrapleural Hematoma Extrapleural hematoma results from the accumulation of blood in the extrapleural space between the parietal pleura and the endothoracic fascia [67–71]. It is uncommon and usually occurs in association with a rib fracture from injury to the intercostal vessels or during traumatic insertion of a subclavian venous catheter. There is no specific clinical symptom that identifies an extrapleural hematoma, but affected pediatric patients may present with chest pain and dyspnea. A large extrapleural hematoma can mimic a hemothorax [70–73]. Ultrasound is rarely used for the diagnosis of extrapleural hematoma. A pleural reflection may be identified at the lower margin of the hematoma, but the costophrenic angle is not obliterated. CT can show a displaced extrapleural fat layer and parietal pleura (the “pleural lining” sign) which is pathognomonic for extrapleural hematoma.

Chylous Effusion

a

Fig. 6.22  Chylothorax in a 13-month-old female with a congenital thoracic lymphatic malformation. (a) Longitudinal grayscale ultrasound image of the left chest shows a large anechoic fluid collection (asterisk) with layering debris (arrows). (b) Coronal T2-weighted, fat-suppressed

Chylous effusion or chylothorax is a rare cause of pleural effusion in the pediatric population, although congenital chylothorax is the most common cause of pleural effusion in the first week of life [74–76]. It arises from the leakage of chyle or lymphatic fluid into the pleural space as a result of damage to the thoracic duct or its tributaries by rupture, laceration, or compression [77–79]. Chylothorax may be congenital or acquired. Con­genital chylothorax may be due to lymphatic anomalies (Fig. 6.22), thoracic cavity defects, or other congenital malformations. It is a rare occurrence, estimated to affect 1 in 10,000 births. Acquired cases are commonly due to birth trauma or malignant, post-surgical, or infectious causes such as tuberculosis or filariasis. Lymphoma is the most common malignant, nontrau-

b

MR image demonstrates a multi-loculated, fluid-filled structure (arrowheads) that extends from the upper retroperitoneal space to the posterior aspect of the left mediastinum adjacent to the thoracic aorta (arrow) in keeping with a lymphatic malformation

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L

Fig. 6.23  Chylothorax in a 7-year-old male with left subclavian vein thrombosis. (a) Longitudinal grayscale ultrasound image of the left chest shows a large pleural effusion (asterisk) with echogenic debris. Extensive atelectasis of the lung (L) is seen inferiorly. (b) Aspiration

revealed milky fluid (asterisk) consistent with a chylothorax (Images courtesy of Dr. Ricardo Restrepo, Nicklaus Children’s Hospital, Miami, FL, USA)

matic etiology, especially non-Hodgkin lymphoma. Iatrogenic injury to the thoracic duct during cardiothoracic surgery is also a common cause of chylothorax in the pediatric population. A small chylothorax is usually asymptomatic, but dyspnea and tachypnea may occur with larger chylous effusions. Ultrasound and CT can demonstrate similar findings of a simple pleural effusion of near water density, without or with debris (Fig. 6.23) in pediatric patients with chylous effusion. However, a chylous effusion may be echogenic in the setting of a thoracic malignancy.

Pneumothorax

Chylothorax typically responds to conservative treatment [80–82] since the thoracic duct leak closes spontaneously in nearly 50% of patients. Initial fluid aspiration is performed for diagnostic purposes. Continuous thoracostomy drainage can be performed for recurrent fluid accumulation to maintain lung expansion. To reduce lymphatic fluid production, treatment with total parenteral nutrition, a fat-restricted diet of medium-chain triglycerides, and administration of somatostatin or its analogue octreotide may be instituted [83, 84]. Surgical interventions including thoracic duct ligation, pleural abrasion, pleurodesis with doxycycline, thoracoscopic parietal pleural clipping [85], or pleural-to-peritoneal shunts can be performed if conservative treatment fails.

Pneumothorax is an abnormal accumulation of air within the pleural space. It can be primary and spontaneous or secondary to underlying pulmonary pathology, connective tissue disease, or infection (Fig. 6.24) [86]. Pneumothorax is considered primary if there is no underlying predisposing condition. The pathophysiology is believed to be due to rupture of blebs or bullae. The highest incidence of primary spontaneous pneumothorax in the pediatric population is in tall, thin males 13–16 years of age [86–88]. In the neonatal or perinatal period, pneumothorax is commonly seen in patients with surfactant deficiency or meconium aspiration syndrome. Both disorders result in alveolar rupture or air leak. The overall incidence of pneumothorax according to gestational maturity is 4%, 2.6%, and 6.7% in early preterm, moderate-late preterm, and term neonates, respectively [89, 90]. Pneumothorax can be visualized on ultrasound along the anterior chest wall of supine pediatric patients since air collects in the non-dependent portions of the pleural cavity [91–93]. Generally, the most common site is along the anterior 2nd–4th intercostal spaces in the midclavicular line. The pleural space should be explored from the sternum to

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Pneumothorax

Closed pneumothorax

a

Open pneumothorax

b

Air in pleural space

Tension pneumothorax

c

Air in pleural space

Fig. 6.24  Pneumothorax can be classified according to the relationship between pleural and atmospheric pressure. (a) A closed pneumothorax has an intact chest wall with pleural cavity pressure less than atmospheric pressure. (b) An open pneumothorax has chest wall disruption with equal

Air in pleural space increasing and unable to escape

pleural cavity and atmospheric pressures. (c) A tension pneumothorax occurs when pleural cavity pressure is greater than atmospheric pressure resulting in contralateral cardiomediastinal shift

Table 6.1  Chest ultrasound signs and imaging findings without and with pneumothorax Ultrasound signs Lung sliding Seashore sign Stratosphere/ Barcode sign B-lines Lung point Lung pulse

Imaging findings Visceral pleura slides against parietal pleura during respiration Coarse or grainy pattern resembling sand on a beach on M-mode Uniformly parallel horizontal lines above and below the pleural line on M-mode Vertically oriented echogenic lines that arise from the pleural line and extend to the bottom of the image Transition from normal lung sliding to absence of lung sliding Rhythmic movement of the pleura in synchrony with cardiac activity

midclavicular line and from the clavicle to the anterior diaphragm. Comparison with the contralateral side may also be helpful. Ultrasound can diagnose a pneumothorax with a high degree of accuracy [6]. It is more sensitive than chest radiography but is similarly specific [94, 95]. However, quantification of pneumothorax on ultrasound is difficult, and therefore ultrasound is unlikely to completely replace the need for a chest radiograph. The high accuracy of ultrasound is due to several reliable arti-

Without pneumothorax Present Present Absent

With pneumothorax Absent Absent Present

May be present

Absent

Absent Present

Present Absent

facts or signs which are discussed in the following sections and summarized in Table 6.1.

Absence of Lung Sliding Absence of lung sliding is diagnostic of a pneumothorax [96– 99], with a reported sensitivity of 95.3%, specificity of 91.1%, and negative predictive value of 100% (p 10 years of age), although these criteria are not universally applied [24]. Ultrasound allows visualization and measurement of lymph node size as well as evaluation of internal architecture and perfusion [25]. Abnormal lymph nodes are typically hypoechoic when compared to the thymus and mediastinal fat and relatively hyperechoic compared to adjacent vessels. Depending on the underlying pathology, they can also demonstrate loss of normal internal architecture with non-visualization of a normal echogenic hilum. Infectious Lymphadenopathy Bacterial Lymphadenopathy

Bacterial pulmonary infections are relatively common in children, and bacterial pneumonia often leads to enlargement of the regional mediastinal lymph nodes. Typical bacterial respiratory pathogens in children younger than 5  years of age include Streptococcus pneumoniae, Staphylococcus aureus, and S. pyogenes. In school-age children older than 5 years of age, the most common bacterial respiratory pathogens are S. pneumoniae, Mycoplasma pneumoniae, and Chlamydia pneumoniae. Although imaging is not routinely performed, it may be indicated in children with severe or recurrent pneumonia and to assess for complications. Mediastinal lymph nodes often enlarge as part of the immune response to bacterial pneumonia, although the organism has not necessarily infected the node itself. On ultrasound, a mediastinal lymph node reactive to bacterial infection is generally increased in size, often with an elliptical or ovoid shape. The long axis remains larger than the short axis, typically with a ratio of >2. The nodal cortex may thicken and become more hypoechoic, especially when compared to adjacent muscle. However, the normal echogenic fatty hilum is typically preserved, and color Doppler

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evaluation demonstrates central hilar vascularity with branching vessels extending into the adjacent nodal parenchyma [25]. Mycobacterium Tuberculosis Lymphadenopathy

According to the World Health Organization, tuberculosis (TB) ranks among the top ten causes of death worldwide [26]. There were an estimated 10.0 million new cases of TB in 2018, 11% of which affected children under 15 years of age. Clinical diagnosis of TB in children is challenging, as symptoms can be nonspecific and tuberculin skin testing also has limitations. Mediastinal lymphadenopathy is common in pediatric patients with tuberculous infection and is usually multifocal. It may be obscured on chest radiography due to a large thymus and variability in the size of affected lymph nodes. However, it can often be detected with ultrasound. Ultrasound has been proposed as an adjunct to chest radiographs for evaluation of mediastinal lymphadenopathy due to TB in children, especially in resource-poor settings, which are common endemic areas for TB [2]. One study found that ultrasound was able to detect mediastinal lymphadenopathy in 67% of children with pulmonary TB who had normal chest radiographs [27]. Ultrasound has also been effective in documenting the decrease in size and number of mediastinal lymph nodes during treatment [28]. When using ultrasound for evaluation of tuberculous mediastinal lymphadenopathy, a four-view approach has been described for ease of communication and standardization [29]. Two orthogonal views are obtained through the suprasternal notch and two views through the left parasternal intercostal space using the thymus as an acoustic window. When obtaining transverse images from a suprasternal approach, anatomic landmarks include the right and left brachiocephalic veins, SVC, aorta, pulmonary trunk, and thymus. In the oblique suprasternal view, anatomic landmarks include the left brachiocephalic vein, aortic arch and its branches, and the thymus. On ultrasound, enlarged tuberculous lymph nodes are hypoechoic and round or oval in shape (Fig. 7.14). Enlarged nodes may be solitary or resemble a mass with multiple matted or conglomerate nodes. They may develop central necrosis with posterior acoustic enhancement. On color Doppler imaging, the vascular pattern is variable but commonly manifests as preserved but displaced hilar vascularity. The central hilar vessels may be absent in nodes with central necrotizing, granulomatous inflammation. Tuberculous nodes often demonstrate capsular hyperemia or inflammatory change in the surrounding soft tissues (i.e., periadenitis). Nodal calcification is not seen in acute primary TB infection (the most common TB infection in children). However, echogenic shadowing calcifications may develop during treatment or with recurrent infection.

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E

*

Fig. 7.14  Mediastinal lymphadenopathy in a 2-year-old male with tuberculosis. Longitudinal grayscale ultrasound image shows a soft tissue mass with central areas of low echogenicity due to necrosis (asterisk) and focal calcification (arrow). E, Pleural effusion

Tuberculosis in children is treated with a short multidrug regimen. Treatment should be initiated promptly as TB has the potential to disseminate quickly and cause complications. The duration of the therapy depends on whether the patient has been previously treated and if the lungs are involved. New cases of pulmonary TB are treated with an aggressive four-drug combination for 2 months followed by a two-drug combination for 4 months. Imaging is not recommended during treatment or follow-up, as there will be no significant decrease in nodal size [30]. Fungal Lymphadenopathy

Fungal respiratory infections are most common in children with primary or acquired immunodeficiency, as with immunosuppression after transplantation, chemotherapy, steroids, or chronic illness. Fungal infection is often suspected when severe infectious symptoms persist despite antibiotic treatment. Common fungal respiratory pathogens affecting children include aspergillus, candida, pneumocystis, coccidioidomycosis, cryptococcus, and histoplasmosis. Several fungal pathogens are endemic to certain regions of the United States, including histoplasmosis in the Ohio/Mississippi river valley and coccidioidomycosis in the southwest. The ultrasound appearance of pulmonary fungal infection in children depends on the underlying pathogen. Coccidioidomycosis frequently results in hilar lymphadenopathy, whereas histoplasmosis may cause hilar and mediastinal lymphadenopathy. On ultrasound, fungal lymph nodes are indistinguishable from tuberculous lymph nodes, as both can develop necrosis and calcification after treatment. Enlarged, matted thoracic lymph nodes can coalesce to form a mediastinal granuloma, which may compress adjacent mediastinal structures. Treatment of fungal diseases in children depends on their severity and the underlying immune status of the child.

Immunocompetent children with mild histoplasmosis or coccidioidomycosis may not require treatment as the disease is self-limited. However, any severe infection or disseminated histoplasmosis requires antifungal medication and possibly a short course of corticosteroid therapy to control symptoms and limit complications [31]. Fibrosing Mediastinitis

Fibrosing mediastinitis is a benign but locally aggressive inflammatory disease characterized by extensive fibrosis in the mediastinum, often resulting in luminal narrowing of vital mediastinal structures including the airways, vessels, and esophagus. The underlying etiology of fibrosing mediastinitis is currently unknown, however genetic factors are thought to play a role [32]. Although no organism has been isolated from biopsy specimens of fibrosing mediastinitis, it occurs most often following histoplasmosis infection and is believed to result from leakage of fungal antigens from infected mediastinal lymph nodes. Exposure to the fungal antigens is thought to incite a profound immune inflammatory response with subsequent development of fibrosis. Morbidity from fibrosing mediastinitis depends on the extent of fibrosis and its effect on adjacent mediastinal structures, including the airways, esophagus, and vessels. On ultrasound, identification of ill-defined, nonvascular mediastinal soft tissue, often with calcification and narrowing of vascular structures, should raise concern for fibrosing mediastinitis in a child with known histoplasmosis infection. The diffuse type of fibrosing mediastinitis can involve multiple compartments, and appreciation of its entire extent may be limited with ultrasound. Therefore, cross-sectional imaging with CT or MR imaging is typically required for complete assessment. Extensive fibrosis associated with granulomatous inflammation of the mediastinum generally does not respond to antifungal therapies and may require endoscopic surgical intervention in severe cases. However, mediastinal adenitis that causes obstruction of the airway, esophagus or vascular structures can be treated with a combination of antifungal medication and corticosteroids [31]. Neoplastic Lymphadenopathy Neoplastic mediastinal lymphadenopathy in children can occur either as a primary malignancy, such as lymphoma, or as metastatic lymph nodes. Lymphoma and lymphomatous involvement of the mediastinal nodes are discussed in an earlier section of this chapter. On ultrasound, metastatic lymph nodes typically appear enlarged and with a rounded contour. There is frequently effacement of the central fatty hilum. The borders of metastatic lymph nodes may be lobulated or irregular but remain well-defined. Matting of lymph nodes can occur, where

7 Mediastinum

lymph nodes coalesce into a single mass-like lesion. On color Doppler imaging, internal hilar vascularity of the metastatic lymph nodes is lost. Instead, there is peripheral vascularity since tumor vessels arise from the nodal periphery. Calcification of metastatic lymph nodes can occur with some malignancies, including osteosarcoma, neuroblastoma, and extragonadal germ cell tumor. Treatment of metastatic mediastinal lymph nodes depends on the nature of the underlying tumor.

Paravertebral (Posterior) Mediastinal Masses Almost 90% of paravertebral (posterior) mediastinal masses in children are of neurogenic origin [33]. Neurogenic tumors are the most common extracranial solid tumors in the pediatric population. Neurogenic tumors can arise from any neuronal structure, including the nerve sheath, sympathetic ganglion, or paraganglion, although the majority arise from the autonomic ganglia, including benign ganglioneuroma, ganglioneuroblastoma of variable malignant potential, and malignant neuroblastoma.

Neuroblastoma Neuroblastoma is the third most common pediatric malignancy after leukemia and central nervous system tumors [34]. The mediastinum is the second most common location for neuroblastoma after the abdomen and generally carries a better prognosis relative to other sites [35]. Children with thoracic neuroblastoma commonly present with pain, shortness of breath, weight loss, and peripheral nerve deficits from neural foraminal invasion. Less often, neuroblastoma can present with Horner syndrome and opsoclonus-myoclonus. Neuroblastoma is traditionally staged using the International Neuroblastoma Staging System, which is based on the surgical and pathological findings. A newer staging system, proposed by the International Neuroblastoma Risk Group (INRG) in 2009, emphasizes the use of image-defined risk factors (IDRFs) [36]. IDRFs describe the surgical risk factors that would make tumor resection difficult at the time of diagnosis, such as whether the tumor encases the aorta or its major branches. Currently, multiple imaging modalities are used for initial staging and follow-up of neuroblastoma, including ultrasound, MR imaging, CT, and nuclear medicine I-123 meta-iodobenzylguanidine (MIBG) scans. On ultrasound, neuro­blastoma typically appears as a heterogenous paravertebral mass, which may be solid or mixed solid and cystic in appearance (Fig. 7.15). It can extend through the neural foramina, which is best appreciated in the neonatal period. Almost half of all neuroblastomas demonstrate calcification which can be coarse, stippled, or curvilinear and is usually

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detected with radiographs or CT, although occasionally it can be visualized with ultrasound. On color Doppler evaluation, neuroblastoma demonstrates internal vascularity but is not highly vascular and does not typically demonstrate a dominant feeding vessel which helps to differentiate it from a congenital lung malformation such as a bronchopulmonary sequestration. Neuroblastoma is a diverse disease, and its prognosis depends on several factors, some of which are patient-­related, although most are tumor-related. Current therapy of neuroblastoma is based on the risk categories as developed by the Children’s Oncology Group. Patients are classified into low-, intermediate-, and high-risk categories based on the stage of the disease, age at presentation, histology of the tumor, MYCN oncogene status, and DNA content of the tumor. The general treatment for the low-risk tumor category is surgical resection, and outcomes are excellent. In a subset of low-risk infants under 1 year of age with a localized primary tumor or with tumor dissemination limited to the skin, liver, and/or bone marrow, observation is an option since there is a high rate of spontaneous regression. For intermediate-­risk disease, a combination of surgery and chemotherapy is the current standard of care. For high-risk disease, an aggressive approach is pursued that includes chemotherapy, surgical resection, stem cell rescue, radiation, and immunologic therapy [37].

Ganglioneuroblastoma Ganglioneuroblastoma is an intermediate tumor on the spectrum of tumors arising from the autonomic (sympathetic) ganglia. Ganglioneuroblastoma shares characteristics of both malignant neuroblastoma and benign ganglioneuroma. Neuroblastoma and ganglioneuroblastoma are often grouped together for cancer reporting, staging, and survival statistics, as both have malignant potential. The imaging characteristics of ganglioneuroblastoma are variable and can range from a well-encapsulated lesion to a poorly marginated lesion associated with metastases. Histologically, a ganglioneuroblastoma contains more than 50% differentiated cells, while neuroblastoma contains less than 50%. On ultrasound, ganglioneuroblastoma can appear as a solid homogenous lesion or as a more cystic and poorly marginated paravertebral mass. Imaging, therefore, cannot reliably differentiate ganglioneuroblastoma from neuroblastoma. Ganglioneuroblastoma together with ganglioneuroma accounts for a quarter of localized neurogenic tumors. Chemotherapy is not effective for these lesions, and non-­ radical or subtotal tumor resection is an acceptable form of treatment as long as the margins of the residual tumor are less than 2  cm in any dimension [38]. Small amounts of residual tumor do not appear to affect survival, although regular long-term follow-up is warranted [39]. In cases where

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Fig. 7.15  Thoracic neuroblastoma in a 5-month-old female who presented with respiratory distress. (a) Transverse grayscale ultrasound image of the upper mediastinum demonstrates a large, round, heterogeneous mass with calcification (arrowheads). (b) Transverse color

Doppler ultrasound image reveals vascular flow to the lesion. (c) Axial contrast-enhanced CT image shows a large, calcified paraspinal mass that displaces the right lung anteriorly and shifts the mediastinum (arrow) to the left

surgery might be associated with significant morbidity, a watch-and-wait approach has been suggested [40].

adrenal gland, and neck [41]. Ganglioneuromas are usually asymptomatic but may rarely present with symptoms of catecholamine excess, such as flushing, if the tumor produces significant levels of catecholamines. On ultrasound, ganglioneuroma typically appears as an elongated, vertically oriented, well-circumscribed mass in the paravertebral region, along the course of the sympathetic chain. It is usually homogenously hypoechoic and vascular by color Doppler. Calcifications are seen in 40–60% of cases and may be fine, speckled, or coarse [41]. Calcification is generally better identified with CT.

Ganglioneuroma Ganglioneuroma is a benign tumor composed entirely of ganglion cells, with no malignant potential. School-age ­children are affected, with a median age of diagnosis ranging from 5 and 10 years. Ganglioneuromas may arise de novo or can result from maturation of a neuroblastoma or ganglioneuroblastoma. The most common locations for ganglioneuroma include the posterior mediastinum, retroperitoneum,

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Although ganglioneuromas are often less aggressive in appearance, because of the substantial overlap in imaging features of ganglioneuroma, ganglioneuroblastoma, and neuroblastoma, it is difficult to reliably distinguish between these tumors based on imaging alone, and pathological evaluation is usually required for definitive diagnosis.

The clinical course of a pericardial cyst is usually benign. When asymptomatic, it can be followed, and spontaneous resolution can occur. When symptomatic or causing compression of cardiac structures, intervention should be considered. Treatment options include cyst aspiration, chemical sclerosis, and surgical resection [42].

Cardiophrenic Angle Masses

Lymphadenopathy

Pericardial Cyst

Pericardial lymph nodes are located in or around the pericardial fat in the prevascular space. Pericardial lymph nodes are typically not visible on imaging studies in normal pediatric patients. Consequently, visible pericardial nodes are likely to be pathologic [43]. On ultrasound, the appearance of a pericardial lymph node can vary depending on the underlying pathology. A reactive node is typically enlarged with an elliptical or ovoid shape. The cortex can appear thickened and hypoechoic as compared to the adjacent pericardial fat. A normal echogenic fatty hilum is preserved. In contrast, a malignant cardiophrenic lymph node is much larger and typically round in shape (Fig. 7.17). The normal echogenic fatty hilum is lost, and prominent central and peripheral vascularity is observed. Treatment of enlarged pericardial lymph nodes depends on the underlying pathology which may include ­antibiotics for infection or antineoplastic regimens for metastatic disease.

A pericardial cyst most often develops as a congenital abnormality of mesothelial origin resulting from failure of fusion of one of the mesenchymal lacunae that form the pericardial sac [42]. It is characterized by a thin wall and usually contains simple fluid. A pericardial cyst is commonly connected to the pericardium and typically occurs in the anterior cardiophrenic angle, frequently on the right side. Some pericardial cysts have been described as developing after infection, inflammation, or trauma. They are usually asymptomatic but can present with symptoms related to compression of adjacent structures. On ultrasound, a pericardial cyst typically appears as a well-circumscribed unilocular cystic structure, predominantly anechoic with a thin wall (Fig.  7.16). On Doppler evaluation, it is avascular. Complexity of the fluid and/or septations may be present if there is superimposed hemorrhage or infection.

a

b

H

Fig. 7.16  Pericardial cyst in a 9-year-old male with a history of pleuropulmonary synovial sarcoma. (a) Axial contrast-enhanced CT image shows a small, well-circumscribed lesion (arrowhead) adjacent to the right heart border. Although the density of the lesion is compatible with

H

a cyst, the patient’s history of tumor raised concern for a metastasis. (b) Sagittal contrast-enhanced ultrasound image (CEUS) reveals the avascular (arrow), benign nature of the lesion. H, Heart

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Fig. 7.17 Pericardial lymph node in a 19-year-old male with relapsed hepatocellular carcinoma. (a) Axial non-contrast CT image shows a lobulated soft tissue mass (arrow) adjacent to the right heart border in keeping with a metastatic pericardial lymph node. (b) Transverse CEUS image of the lymph node after an initial cryoablation procedure reveals a central non-enhancing zone consistent with ablated tumor. There is an irregular

ring of surrounding enhancing tissue (arrowheads) that probably represents a combination of residual tumor and inflamed adjacent soft tissues. (c) Transverse CEUS image of the lymph node after a second cryoablation shows enlargement of the central avascular zone with little enhancement of the surrounding tissues in keeping with a successful procedure

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5. Han BK, Babcock DS, Oestreich AE. Normal thymus in infancy: sonographic characteristics. Radiology. 1989;170(2):471–4. 6. Han BK, Yoon HK, Suh YL. Thymic ultrasound. II. Diagnosis of aberrant cervical thymus. Pediatr Radiol. 2001;31(7):480–7. 7. Han BK, Suh YL, Yoon HK.  Thymic ultrasound. I.  Intrathymic anatomy in infants. Pediatr Radiol. 2001;31(7):474–9. 8. Yildiz AE, Elhan AH, Fitoz S. Prevalence and sonographic features of ectopic thyroidal thymus in children: a retrospective analysis. J Clin Ultrasound. 2018;46(6):375–9. 9. Lin MJ, Gurley K, Hoffmann B. Bedside ultrasound for tracheal tube verification in pediatric emergency department and ICU patients: a systematic review. Pediatr Crit Care Med. 2016;17(10):e469–76. 10. Merten DF. Diagnostic imaging of mediastinal masses in children. AJR Am J Roentgenol. 1992;158(4):825–32.

1. Wernecke K, Peters PE, Galanski M. Mediastinal tumors: evaluation with suprasternal sonography. Radiology. 1986;159(2):​405–9. 2. Moseme T, Andronikou S. Through the eye of the suprasternal notch: point-of-care sonography for tuberculous mediastinal lymphadenopathy in children. Pediatr Radiol. 2014;44(6):681–4. 3. Wernecke K, Potter R, Peters PE, Koch P. Parasternal mediastinal sonography: sensitivity in the detection of anterior mediastinal and subcarinal tumors. AJR Am J Roentgenol. 1988;150(5):1021–6. 4. Carter BW, Benveniste MF, Madan R, Godoy MC, de Groot PM, Truong MT, et  al. ITMIG classification of mediastinal compartments and multidisciplinary approach to mediastinal masses. Radiographics. 2017;37(2):413–36.

7 Mediastinum 11. Evers M, Rechnitzer C, Graem N, Skov Wehner P, Schroeder H, Rosthoej S, et  al. Epidemiological study of paediatric germ cell tumours revealed the incidence and distribution that was expected, but a low mortality rate. Acta Paediatr. 2017;106(5):779–85. 12. Moeller KH, Rosado-de-Christenson ML, Templeton PA. Mediastinal mature teratoma: imaging features. AJR Am J Roentgenol. 1997;​169(4): 985–90. 13. Grabski DF, Pappo AS, Krasin MJ, Davidoff AM, Rao BN, Fernandez-Pineda I. Long-term outcomes of pediatric and adolescent mediastinal germ cell tumors: a single pediatric oncology institutional experience. Pediatr Surg Int. 2017;33(2):235–44. 14. Sudour-Bonnange H, Faure-Conter C, Martelli H, et al. Primary mediastinal and retroperitoneal malignant germ cell tumors in children and adolescents: Results of the TGM95 trial, a study of the French Society of Pediatric Oncology (Société Française des Cancers de l’Enfant). Pediatr Blood Cancer. 2017;64(9) 15. Ward E, DeSantis C, Robbins A, Kohler B, Jemal A. Childhood and adolescent cancer statistics, 2014. CA Cancer J Clin. 2014;64(2):83–103. 16. Nachman JB, Sposto R, Herzog P, Gilchrist GS, Wolden SL, Thomson J, et  al. Randomized comparison of low-dose involved-­field radiotherapy and no radiotherapy for children with Hodgkin’s disease who achieve a complete response to chemotherapy. J Clin Oncol. 2002;20(18):3765–71. 17. Hodgson DC, Dieckmann K, Terezakis S, Constine L; International Lymphoma Radiation Oncology Group. Implementation of contemporary radiation therapy planning concepts for pediatric Hodgkin lymphoma: Guidelines from the International Lymphoma Radiation Oncology Group. Pract Radiat Oncol. 2015;5(2):85–92. 18. Link MP, Shuster JJ, Donaldson SS, Berard CW, Murphy SB. Treatment of children and young adults with early-stage non-­Hodgkin’s lymphoma. N Engl J Med. 1997;337(18):1259–66. 19. Ghaffarpour N, Burgos CM, Wester T. Surgical excision is the treatment of choice for cervical lymphatic malformations with mediastinal expansion. J Pediatr Surg. 2018;53(9):1820–4. 20. Merrow AC, Gupta A, Patel MN, Adams DM. 2014 Revised classification of vascular lesions from the International Society for the Study of Vascular Anomalies: radiologic-pathologic update. Radiographics. 2016;36(5):1494–516. 21. Nobuhara KK, Gorski YC, La Quaglia MP, Shamberger RC.  Bronchogenic cysts and esophageal duplications: common origins and treatment. J Pediatr Surg. 1997;32(10):1408–13. 22. Bratu I, Laberge JM, Flageole H, Bouchard S. Foregut duplications: is there an advantage to thoracoscopic resection? J Pediatr Surg. 2005;40(1):138–41. 23. Scarpa AA, Ram AD, Soccorso G, Singh M, Parikh D. Surgical experience and learning points in the management of foregut duplication cysts. Eur J Pediatr Surg. 2018;28(6):515–21. 24. de Jong PA, Nievelstein RJ.  Normal mediastinal and hilar lymph nodes in children on multi-detector row chest computed tomography. Eur Radiol. 2012;22(2):318–21. 25. Jenssen C, Annema JT, Clementsen P, Cui XW, Borst MM, Dietrich CF.  Ultrasound techniques in the evaluation of the mediastinum, part 2: mediastinal lymph node anatomy and diagnostic reach of ultrasound techniques, clinical work up of neoplastic and inflammatory mediastinal lymphadenopathy using ultrasound techniques and how to learn mediastinal endosonography. J Thorac Dis. 2015;7(10): E439–58. 26. Global tuberculosis report. World Health Organization; 2019.

237 27. Bosch-Marcet J, Serres-Creixams X, Zuasnabar-Cotro A, Codina-­ Puig X, Catala-Puigbo M, Simon-Riazuelo JL.  Comparison of ultrasound with plain radiography and CT for the detection of mediastinal lymphadenopathy in children with tuberculosis. Pediatr Radiol. 2004;34(11):895–900. 28. Bosch-Marcet J, Serres-Creixams X, Borras-Perez V, Coll-Sibina MT, Guitet-Julia M, Coll-Rosell E. Value of sonography for follow-­up of mediastinal lymphadenopathy in children with tuberculosis. J Clin Ultrasound. 2007;35(3):118–24. 29. Pool KL, Heuvelings CC, Belard S, Grobusch MP, Zar HJ, Bulas D, et al. Technical aspects of mediastinal ultrasound for pediatric pulmonary tuberculosis. Pediatr Radiol. 2017;47(13):1839–48. 30. American Academy of Pediatrics. Tuberculosis. In: Kimberlin DWBM, Jackson MA, Long SS, editors. Red book: 2018 report of the committee on infectious diseases. Itasca, IL: American Academy of Pediatrics; 2018. 31. American Academy of Pediatrics. Histoplasmosis. In: Kimberlin DWBM, Jackson MA, Long SS, editors. Red book: 2018 report of the committee on infectious diseases. Itasca, IL: American Academy of Pediatrics; 2018. p. 449–53. 32. Rossi SE, McAdams HP, Rosado-de-Christenson ML, Franks TJ, Galvin JR. Fibrosing mediastinitis. Radiographics. 2001;21(3):​737–57. 33. Saenz NC, Schnitzer JJ, Eraklis AE, Hendren WH, Grier HE, Macklis RM, et al. Posterior mediastinal masses. J Pediatr Surg. 1993;28(2):172–6. 34. American Cancer Society, Inc. Cancer Facts & Figures 2017[Internet]. Available from: https://www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/cancer-facts-figures-2017.html 35. Pavlus JD, Carter BW, Tolley MD, Keung ES, Khorashadi L, Lichtenberger JP 3rd. Imaging of thoracic neurogenic tumors. AJR Am J Roentgenol. 2016;207(3):552–61. 36. Brisse HJ, McCarville MB, Granata C, Krug KB, Wootton-Gorges SL, Kanegawa K, et al. Guidelines for imaging and staging of neuroblastic tumors: consensus report from the international neuroblastoma risk group project. Radiology. 2011;261(1):243–57. 37. Swift CC, Eklund MJ, Kraveka JM, Alazraki AL. Updates in diagnosis, management, and treatment of neuroblastoma. Radiographics. 2018;38(2):566–80. 38. Decarolis B, Simon T, Krug B, Leuschner I, Vokuhl C, Kaatsch P, et al. Treatment and outcome of ganglioneuroma and ganglioneuroblastoma intermixed. BMC Cancer. 2016;16:542. 39. Yang T, Huang Y, Xu T, Tan T, Yang J, Pan J, et al. Surgical management and outcomes of ganglioneuroma and ganglioneuroblastoma-­ intermixed. Pediatr Surg Int. 2017;33(9):955–9. 40. Alexander N, Sullivan K, Shaikh F, Irwin MS.  Characteristics and management of ganglioneuroma and ganglioneuroblastoma-­ intermixed in children and adolescents. Pediatr Blood Cancer. 2018;65(5):e26964. 41. Lonergan GJ, Schwab CM, Suarez ES, Carlson CL. Neuroblastoma, ganglioneuroblastoma, and ganglioneuroma: radiologic-pathologic correlation. Radiographics. 2002;22(4):911–34. 42. Meschisi M, Piccione MC, Bella GD, Zito C.  Multimodalities imaging in diagnosis of pericardial cyst. J Cardiovasc Echogr. 2015;25(2):60–2. 43. Dietrich CF, Annema JT, Clementsen P, Cui XW, Borst MM, Jenssen C. Ultrasound techniques in the evaluation of the mediastinum, part I: endoscopic ultrasound (EUS), endobronchial ultrasound (EBUS) and transcutaneous mediastinal ultrasound (TMUS), introduction into ultrasound techniques. J Thorac Dis. 2015;7(9):​E311–25.

8

Chest Wall Jessica Kurian

Abbreviations ABC Aneurysmal bone cyst CEUS Contrast-enhanced ultrasound CH Congenital hemangioma CT Computed tomography DLBCL Diffuse large B-cell lymphoma ES Ewing sarcoma IH Infantile hemangioma LM Lymphatic malformation MH Mesenchymal hamartoma MHE Multiple hereditary exostoses MR Magnetic resonance MRSA Methicillin-resistant Staphylococcus aureus NICH Non-involuting congenital hemangioma NHL Non-Hodgkin lymphoma OS Osteosarcoma PICH Partially involuting congenital hemangioma PNET Primitive neuroectodermal tumor RICH Rapidly involuting congenital hemangioma RMS Rhabdomyosarcoma VATS Video-assisted thoracoscopic surgery VM Venous malformation

Introduction The chest wall consists of the bone and soft tissue structures that surround the lungs and the vascular structures of the chest. It contributes to the physiologic mechanism of respiration, protects the lungs and mediastinal structures, and provides mechanical stabilization to the thorax, shoulder girdle, and arms. The chest wall is made up of multiple components, including the skin and subcutaneous tissue, muscles, bones J. Kurian (*) Division of Pediatric Radiology, Departments of Radiology and Pediatrics, Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY, USA e-mail: [email protected]

and cartilage (sternum, rib cage, spine), vessels, and nerves. Importantly, in children the chest wall is less rigid than in adults, due to its greater cartilaginous component. Ultrasound is particularly well-suited for evaluation of the pediatric chest wall, as acoustic windows are excellent when there is thin adipose tissue and incomplete ossification of the bones, and most of the structures of interest are superficial. Ultrasound also allows for efficiently focused imaging of palpable chest wall abnormalities (Table 8.1). This chapter reviews up-to-date techniques for ultrasound imaging of the pediatric chest wall, as well as chest wall embryology and normal anatomy. The clinical and imaging features of various congenital and acquired disorders of the chest wall in infants and children are also discussed.

Technique Patient Positioning Optimal positioning is important for maintaining patient comfort, reducing motion, and thereby maximizing image quality. To examine the anterior and lateral chest wall, children can be scanned in supine and lateral decubitus positions, with the arms raised when necessary. To examine the posterior chest wall, the patient can be sitting while using a bedside table to rest the arms and support the chest during scanning. For infants and young children, a bolster (such as a foam wedge or rolled towel) should be used for support, and it is important to have a parent, caregiver, or child life specialist at the bedside to assist with positioning and motion reduction.

Ultrasound Transducer Selection High-frequency (7–15 MHz) linear array transducers (also known as “small parts” transducers) provide the best near-­field resolution and are therefore optimal for examination of the superficial structures that comprise the chest wall. In general, one should use the

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Table 8.1  Palpable pediatric chest wall lesions Lesion Congenital Asymmetric costochondral junction Congenital vascular lesions Infectious Cellulitis Abscess

Neoplastic Benign Osteochondroma

Lipoma Malignant Sarcoma

Lymphoma

Traumatic Hematoma

Rib fracture

Foreign body

Description

Location

US Features

Angular deformity of cartilage (benign anatomic variant)

Junction of cartilage and ossified rib, parasternal anterior chest wall Subcutaneous tissue > muscle

Hypoechoic cartilage is angulated or enlarged – must compare to the other side to see asymmetry See Table 8.2

Bacterial infection of the skin and subcutaneous tissue Localized collection of pus with surrounding inflammation. Develops from cellulitis or wound

Subcutaneous tissue

Thickening, hyperechogenicity, and “disarray” of subcutaneous fat; “cobblestoning”; hyperemia Fluid collection with variable echogenicity, thick hyperemic capsule, swirling echoes

Benign osteocartilaginous excrescence of the bone, often affects chest wall in MHE Benign tumor of mature fat cells

Rib >> scapula, clavicle, spine, sternum

Protuberance continuous with the rib, posterior acoustic shadowing, hypoechoic cartilage cap

Subcutaneous tissue >> muscle, commonly upper back

Well circumscribed, usually hypoechoic, thin hyperechoic linear bands, no flow or minimal flow

Group of malignancies arising from the soft tissue, bone, cartilage, or bone marrow

Rhabdomyosarcoma: Chest wall Heterogeneous solid mass, irregular contour, internal vascularity, necrosis musculature Ewing sarcoma: rib >> other sites Osseous origin with sunburst lines and large extraosseous portion in Ewing sarcoma Osteosarcoma: rib >> other sites Posterior acoustic shadowing from osteoid matrix in osteosarcoma Enlarged lymph nodes, nonspecific solid mass, May involve lymph nodes muscle infiltration (rare) (axillary, pectoral, cardiophrenic) or chest wall bone and muscle

Vascular tumors and malformations

Group of malignancies arising from lymphocytes

Localized extravascular collection of blood products. Caused by trauma or bleeding disorder Break in the rib, usually caused by trauma

Usually subcutaneous tissue

Subcutaneous tissue or muscle

Osseous portion of the rib or costal cartilage

Any external object that becomes Usually subcutaneous tissue retained in the patient, via penetrating wound or iatrogenic placement

Appearance varies by age: initially hyperechoic becoming hypoechoic with liquifaction; fluid-debris levels, septations. Avascular unless chronically organized Acute: Discontinuity or step-off of anterior cortical echogenic line, “chimney phenomenon” acoustic shadow, surrounding fluid collection Healing: Calcific prominence (callus) with acoustic shadowing Hyperechoic structure with clean or dirty acoustic shadow; “comet-tail” artifact from metal or glass; surrounding inflammation or hypoechoic fluid collection if retained >24 hours

MHE, Multiple hereditary exostoses

highest frequency possible that still allows adequate depth visualization of the lesion in question. For very small or very superficial lesions (e.g., skin lesions), a high-frequency L-shaped transducer (also known as a “hockey stick” transducer) is a useful adjunctive tool. This transducer has a small acoustic window with a small footprint on the order of 25 mm, compared to 38 mm or larger for commonly used linear transducers [1].

Low-­frequency transducers may be required on some occasions when greater depth penetration is required, such as for larger patients, or when examining lesions with a deeper extent, usually greater than 6 cm from the skin surface [2, 3]. If there is a disease process that extends deep to the chest wall or requires a wider viewing area, a phased array transducer is appropriate. In these cases, probes with small footprints are helpful for scanning through the intercostal spaces [3].

8  Chest Wall

Imaging Approaches Protocols When performing ultrasound of the chest wall, rather than trying to develop a standardized protocol, it is more efficient to tailor each study to the location and size of the suspected lesion. For the majority of ultrasound examinations of the chest wall, the scan is targeted directly to a region of concern, usually a palpable mass. Technical parameters such as frequency, focal depth, gain, etc. should be adjusted appropriately for the position, depth, and size of the targeted lesion. Color Doppler ultrasound should be used to determine the vascular properties of any chest wall mass, particularly soft tissue abscesses and vascular malformations. For children who are old enough to follow instructions, short periods of breath holding can be helpful, especially during Doppler assessment. Because the majority of chest wall examinations deal with superficial structures, it is important to use an adequate amount of coupling gel, and the imager’s hand should fully support the weight of the transducer. This minimizes transducer pressure which can cause morphological distortion of superficial lesions and reduce detectability of Doppler flow [4, 5]. When evaluating deeper structures or large pediatric patients, these techniques are not always applicable, since some degree of manual pressure may be necessary to improve image quality [6]. Ultrasound images should be obtained in sagittal and transverse planes that extend through the abnormality. Cine clips are helpful for characterization of irregularly shaped lesions. When evaluating anterior chest wall deformities, comparison images of the contralateral side at the same level must be obtained to assess symmetry. It is often helpful to initially study the asymptomatic side to familiarize oneself with the patient’s normal anatomy. Extended field of view or panoramic images can be used as necessary to depict large lesions. Annotations It is important to document images using standard landmarks based on the surface anatomy of the chest. Transducer position should be documented by referencing these landmarks, including the mid-sternal or anterior median line (midline from sternal notch to xiphoid), mid-clavicular line (drawn vertically through the middle of the clavicle), axillary fossa (bordered by the scapula, clavicle, first rib, pectoralis and latissimus dorsi muscles), anterior and posterior axillary lines (through the anterior and posterior axillary folds), mid-axillary line (through the apex of the axillary fossa), mid-scapular

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line (drawn vertically through the inferior angle of the scapula), and mid-­spinal line (midline posterior chest) [7].

Contrast-Enhanced Ultrasound In recent years, contrast-enhanced ultrasound (CEUS) has gained a preliminary foothold in the evaluation of lesion vascularity patterns, particularly of liver and kidney masses [8, 9]. Second-generation contrast agents are now in use, which consist of microbubbles of gas suspended in a phospholipid shell and administered through a peripheral intravenous line. These microbubbles resonate when exposed to the ultrasound beam, resulting in vascular “enhancement” that appears as hyperechogenicity on dynamic grayscale imaging. This technique allows visualization of vascular anatomy and temporal perfusion patterns. There is relatively little experience with the use of CEUS in the evaluation of extremity soft tissue tumors in children or of the chest wall. However, early studies of CEUS imaging of extremity masses in adults show that it increases accuracy in distinguishing between benign and malignant lesions [10– 13]. It is feasible that the same principles can be translated into evaluation of chest wall masses. This would reduce the need for computed tomography (CT) or magnetic resonance (MR) imaging and thereby avoid the risks associated with ionizing radiation, sedation and anesthesia, and gadolinium administration. Further study is needed in this area.

Normal Development and Anatomy Normal Development The musculoskeletal structures of the chest wall form between the fourth and eighth week of gestation; however, some components continue to develop even after birth [14]. The chest wall and trunk originate from paraxial mesoderm and somatic (lateral plate) mesoderm [15]. The paraxial mesoderm organizes itself segmentally along the neural tube into 40 somites. The somites then segregate into sclerotomes and dermomyotomes [16].

Thoracic Skeleton The sclerotomes become the bony structures of the chest wall [16]. They are initially located ventromedially and migrate toward the neural tube to become the vertebrae. Each vertebra is formed by two successive somite levels. Sclerotomic cells surround the notochord to form the intervertebral discs. In the thorax, foci of mesenchyme develop

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J. Kurian Vertebral arch

Vertebral Costal arch process

Costovertebral joint

Rib

Rib

Vertebral body Growing rib 35 days

Vertebral body

Vertebral body

38 days

40 days

Fig. 8.1  Appearance of the ribs and vertebrae at progressive stages of embryonic development. The costal processes develop from the mesenchyme at the lateral aspect of the thoracic vertebral arches and extend outward to become the growing ribs. The ribs continue to lengthen in a

horizontal direction. The transverse processes of the vertebrae grow outward to meet the tubercle of the rib. A joint also forms between the vertebral body and the head of the rib (“costovertebral joint”)

Clavicle

Manubrium Clavicle Rib

Ossification centers Mesenchymal condensations 43 days

Ribs

Xiphoid process

Sternal bars (begin to chondrify and fuse as ribs become connected) 45 days

Birth

Fig. 8.2  Appearance of the sternum at progressive stages of fetal development. Mesenchymal condensations in the midline thorax form the two longitudinal sternal bars. The sternal bars and anterior aspects of the ribs are cartilaginous (indicated in blue). The sternal bars fuse in a

craniocaudad manner. Segmental ossification centers form in the manubrium and sternum, also in a craniocaudad order. Two or more ossification centers can form within each segment (but will later fuse). The xiphoid process does not ossify until the second or third decade of life

lateral to the vertebral arches to become the costal processes, which then lengthen to form the ribs (Fig.  8.1). Later in development, primary ossification centers form near the rib angles, and the cartilaginous ribs undergo endochondral ossification. Complete ossification of the ribs only occurs during adolescence, at which time secondary ossification centers form at the heads and tubercles of the ribs. The sternum is independently derived later in gestation (10 weeks) from somatic (lateral plate) mesoderm [16]. In the midline, mesenchymal tissue forms two longitudinal cartilaginous sternal bars, which eventually fuse in a craniocaudal direction (Fig.  8.2). As with the ribs, the cartilaginous sternum later develops segmental ossification centers that

will fuse to each other (Fig. 8.3). The xiphoid completes its ossification only in the second or third decade of life, sometimes even as late as 40 years of age [16, 17].

Chest Wall Soft Tissues The dermomyotomes become the soft tissues of the chest wall [16]. They are positioned dorsolaterally and subsequently separate into dermatomes and myotomes. The myotomes give rise to the skeletal musculature, still maintaining their segmental arrangement. The myotomes further subdivide into two components: epimeres which form the deep muscles of the back and hypomeres which form the muscles of the ventrolateral body wall, including the intercostal mus-

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1

cles (Fig. 8.4). The dermatomes give rise to the dermis and connective tissue of the dorsal chest wall. In contrast, the ventral dermis is formed from somatic mesoderm. Each dermatome and myotome is innervated by a segmental nerve.

Normal Anatomy 2

3 Fuse to Form Sternal Body 4

5

6

Fig. 8.3  Anterior and lateral views of the sternum. The sternum consists of six ossification centers: the manubrium (1), the four segments of the sternal body (2–5), and the xiphoid process (6). The sternal body segments 2–5 begin fusing in adolescence and complete fusion by age 25 years. The manubrium does not fuse to the sternum (except occasionally in old age) and remains as the manubriosternal symphysis, also known as the sternal angle or angle of Louis

Thoracic Skeleton The thoracic skeleton consists of the 12 thoracic vertebrae (T1-T12), 12 paired ribs and costal cartilages, and the sternum (Fig. 8.5). A typical rib consists of a head, neck, tubercle, angle, and shaft. The head of each rib articulates with the superior articular facet of the vertebra it is numbered after and also with the inferior articular facet of the vertebra above; this forms the costovertebral joint. The tubercle of the rib articulates with the transverse process of the vertebra, forming the costotransverse joint. These facet joints are synovial joints. The shaft of the rib has a costal groove that houses the intercostal neurovascular bundle as it travels forward from the spine and aorta. The first through seventh ribs are termed “true” ribs, as they connect directly to the sternum and manubrium. The 8th through 12th ribs are termed “false” ribs, as they do not articulate with the sternum. The costal cartilages are bands of hyaline cartilage that attach the medial ends of the ribs to the sternum. The costal cartilages of ribs 1–7 curve superiorly to articulate with the sternum, and the costal cartilages of ribs 8–10 articulate with the cartilage of the rib above. The 11th

Epimere

Extensor muscle of spine

Intermuscular septum Spinal cord

Dorsal primary ramus

Spinal ganglion Hypomere

Outer, intermediate, and inner muscular layer of hypomere as found in wall of thorax and abdomen

Dorsal aorta Ventral primary ramus

Coelomic cavity

Rectus column

a Fig. 8.4  Transverse sections of the embryonic thorax at (a) 5 weeks and (b) 7 weeks. The skeletal muscle is formed from myotomes, which divide into epimeres and hypomeres. The epimeres form the deep extensor muscles of the back (erector spinae). The hypomeres form the

b ventrolateral body wall muscles by separating into three layers (outer, intermediate, and inner) intercostal muscles. A segmental nerve associates with each myotome to provide motor innervation via the dorsal and ventral rami

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J. Kurian Sternum

Sternal notch

Clavicle

Manubrium

Angle

Body

Xiphoid process

1 Neck

2 3 True ribs (1-7)

4 Middle Rib: Posterior View

5 6

1st Left Rib: Superior view

8

Tubercle

Head Neck Tubercle (no angle)

11 9

Articular facets

Costal groove

7

False ribs (8-12)

Head

Angle

Subclavian vein & artery grooves 2nd Left Rib: Superior View

12

10

Head Neck Tubercle Angle

Floating ribs (11-12)

Costal cartilages

Fig. 8.5  Anterior view of the thoracic skeleton. The true, false, and floating ribs are denoted. The anatomy of the ribs is shown, consisting of the head, neck, tubercle, angle, and shaft. The costal groove houses the intercostal vein, artery, and nerve. The head of the rib has two artic-

ulations, one with the costal facet of the vertebra at the same level and one with the cephalad level (costovertebral joints). The tubercle of the rib articulates with the transverse process of the vertebra (costotransverse joint)

and 12th ribs are termed “floating” ribs because their cartilage terminates in the muscles of the abdominal wall. The sternocostal joints are synovial joints, except for the first rib which is fused to the manubrium as a synchondrosis. The sternum consists of three flat bones: the manubrium, sternal body, and xiphoid process. The jugular or suprasternal notch is the palpable landmark at the superior aspect of the manubrium, bounded by the clavicles on each side. The sternal angle or angle of Louis is a bony ridge at the manubriosternal joint, which is continuous with the second rib and is the landmark for the level of the tracheal bifurcation. The xiphoid is the smallest and thinnest bone, located at the inferior aspect of the sternum. The paired internal thoracic arteries (also known as the internal mammary arteries) are branches of the subclavian arteries that supply the sternum (Fig. 8.6). The ventral chest wall is also supplied by collateral vessels between the subclavian artery and the deep epigastric artery.

coracoid process of the scapula. The other superficial or extrinsic muscles of the back include the serratus anterior and latissimus dorsi. The serratus anterior consists of multiple slips of muscle coursing from the medial scapula along the anterolateral chest wall between ribs 1 and 8. The latissimus dorsi is the largest muscle in the body and has extensive attachments to the spine (T6 or T7 through L5), ribs (posterior ribs 8 or 9 through 12), inferior border of the scapula, humerus, and posterior iliac and sacral bones. The smaller extrinsic muscles of the chest wall include the trapezoids, rhomboids, subclavius, and serratus posterior. Additionally, some of the abdominal wall muscles have attachments to the ribs and xiphoid process, including the rectus abdominis, external and internal oblique muscles, and transversus abdominis. The intrinsic or deep back muscles include several groups of muscles that fuse to the vertebral bodies, functioning to maintain posture and control vertebral movement. These include the erector spinae and transversospinalis groups. The deepest muscles of the chest wall are the intercostal muscles (Figs. 8.6 and 8.7). There are three layers of muscle spanning each intercostal space: the external and internal intercostal muscles, which course obliquely in opposite directions to each other, and the innermost intercostal muscle, which is a thin layer that is separated from the former two muscles by the

Musculature The muscles of the anterior chest wall include the pectoralis major, a large fan-shaped muscle originating from the clavicle and sternum and inserting on the bicipital groove of the humerus (Fig. 8.6). The pectoralis minor lies deep to the pectoralis major, originating from ribs 3–5 and inserting on the

8  Chest Wall

245 Sternohyoid muscle Sternocleidomastoid muscle

Internal ernal jugular vein Middle e scalene muscle

Anterior scalene muscle

Anteriorr scalene muscle Posteriorr scalene muscle

Trapezius muscle Omohyoid muscle

Clavicle

Pectoralis major muscle

Common carotid artery

Deltoid muscle

Internal thoracic artery and vein

External intercostal muscles Intercostobrachial nerve membranes Internal intercostal muscles

Intercostal vein, artery and nerve Transversus thoracic muscle Musculophrenic artery and vein

External intercostal membrane

External intercostal muscles

Digitations of serratus anterior muscle

Superior epigastric artery and vein

Latissimus dorsi muscle

Rectus abdominis muscle

Fig. 8.6  Anterior view of the thorax. The muscles and neurovascular structures of the chest wall are denoted, with their relationships to the thoracic skeleton. The extrinsic muscles that are shown here include the trapezius, serratus anterior, and latissimus dorsi. The intrinsic muscles refer to the

intercostal muscle layers and the transversus thoracic muscle. The anterior aspect of the external intercostal muscle thins into an aponeurosis called the external intercostal membrane, which inserts on the sternum. The pectoralis muscle connects the anterolateral thoracic wall to the upper extremity

Rami communicantes Anterior ramus (intercostal nerve) Internal intercostal membrane External intercostal muscle

Posterior intercostal artery Lateral pectoral cutaneous branch artery

Lateral pectoral cutaneous branch nerve Innermost intercostal muscle Internal intercostal muscle Common membrane of innermost intercostal and transversus thoracis muscles External intercostal membrane Anterior pectoral cutaneous branch nerve

Parietal pleura Sympathetic (cut edge) tunk

Aorta

Site of anastomosis/potential collateral pathway between posterior and anterior intercostal arteries

Transversus Internal thoracis thoracic artery

Anterior perforating branch artery

Fig. 8.7  Transverse section through the mid-thorax at T4-T5. This section illustrates the intrinsic muscle layers of the chest wall, as well as the segmental arterial blood supply and spinal innervation. The anterior rami give rise to the intercostal nerves, which supply pectoral cutaneous

Anterior intercostal artery

branches. The posterior intercostal arteries arise from the thoracic aorta, and the anterior intercostal arteries arise from the internal thoracic (internal mammary) artery. Perforating arteries supply the muscle, fascia, and skin

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J. Kurian

Skin: epidermis and dermis

a

Skin Subcutaneous

Subcutaneous fat

Fascia

Fascia

Rib

Skeletal muscles Internal intercostal muscle

Intercostal

Rib

Muscle

Pleura

External intercostal muscle Rib

Lung

Vein, artery, and nerve Parietal pleura Intrapleural space Visceral pleura Lung parenchyma

b

Skin Subcutaneous Fascia

Muscle Rib

Fig. 8.8  Sectional view of the layers of the chest wall. The fascia represents a layer of connective tissue that lies below the subcutaneous fat and encases the skeletal muscle. The extrinsic layers of skeletal muscle vary according to the region of the chest wall (e.g., pectoralis, serratus anterior, etc.)

neurovascular bundle. The transversus thoracis muscle can be considered part of the innermost layer and attaches to the sternum, xiphoid, and costal cartilage of ribs 2–6. Blood supply to these muscles is from the posterior intercostal branches of the thoracic aorta and the anterior intercostal branches of the internal thoracic artery. The intercostal nerves arise from the anterior rami of the 1st through 11th thoracic nerves.

 ltrasound Appearance of Normal Chest Wall U Anatomy The layers of the chest wall, from outer to inner, are the skin, subcutaneous fat, fascia, skeletal muscle, and bone, underneath which lie the pleura and lung (Fig. 8.8). These layers can be readily demonstrated using high-frequency ultrasound and are important to recognize in localizing the origin of a mass (Fig. 8.9). The epidermis and dermis appear together as a single thin hyperechoic layer. Deep to this, the subcutaneous fat can be of variable thickness and demonstrates hypoechoic lobules of fat with randomly arranged echogenic septa. The fascia separates the fat and superficial muscle layer, appearing as a thin hyperechoic band. Skeletal muscles are encountered next, recognized by hypoechogenicity with characteristic echogenic striations. This layer includes the pectoralis muscles, serratus anterior, latissimus dorsi, rhomboids, and trapezius muscles. In pubertal females, breast tissue can be seen overlying the pectoral muscles between the second and sixth ribs (Fig. 8.10) [4]. In larger females, a retromammary fat layer

Intercostal

Pleura

Lung

Fig. 8.9  Normal chest wall anatomy on ultrasound in (a) a 15-month-­ old female and (b) a 12-year-old male. The layers of the chest wall, from outer to inner, are the skin (dermis and epidermis), subcutaneous fat, fascia, skeletal muscle, rib, and intercostal muscles. Deep to this lie the pleura and lung parenchyma. The subcutaneous fat demonstrates a lobular appearance and contains thin septa. Linear echogenic striations can be seen in the skeletal muscle. The cartilaginous portion of the ribs in the younger patient (a) is hypoechoic. The ossified rib in the older patient (b) casts a posterior acoustic shadow

Fig. 8.10  Normal chest wall anatomy on ultrasound in an 11-year-old female. The developing breast tissue (asterisk) is hypoechoic, with surrounding echogenic connective tissue and fat. The breast tissue overlies the pectoralis major muscle (arrows), which contains echogenic striations that are typical of skeletal muscle

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S1

S2

S3

M R R Fig. 8.11  Normal sternum in a 5-day-old male. Sagittal grayscale ultrasound image at the mid-sternal line demonstrates the ossification centers of the manubrium (M) and the first three sternal body segments (S1, S2, S3). The fourth segment and the xiphoid are beyond the field of view. Hypoechoic cartilage (white arrowheads) is seen between the sternal ossification centers. The cartilage at the manubriosternal articulation (black arrowhead) has an outward prominence which corresponds to the palpable sternal angle. Thymic tissue (asterisks) is noted in the retrosternal space

Fig. 8.13  Intercostal vessels in a 17-year-old male. Sagittal color Doppler ultrasound image (with inverted color scale) of the anterior chest at the level of the cartilaginous ribs (R) demonstrates the intercostal vein (white arrow) and intercostal artery (black arrow) along the inferior margin of the rib

Fig. 8.12  Xiphoid process in a 17-year-old male. Sagittal grayscale ultrasound image at the mid-sternal line demonstrates the hypoechoic cartilage (black arrows) of the xiphoid and the ossified portion (white arrow) of the inferior sternal body. The xiphoid may not ossify until the third decade of life

can sometimes be seen between the breast tissue and the pectoral muscle. Deep to the muscles are the bony structures of the thorax (ribs, sternum, scapulae, vertebrae). The cortical surface of ossified bone appears as a sharp hyperechoic line with intense posterior shadowing. The non-ossified hyaline cartilage of the ribs is hypoechoic or nearly anechoic (due to high water content), sometimes with a thin hyperechoic border and internal scattered punctate bright foci (Fig.  8.9a). The echogenicity of cartilage increases with skeletal maturation [18]. Cartilage can also be seen in the sternum of young patients prior to fusion of the ossification centers, as well as at the xiphoid (Figs. 8.11 and 8.12). Deep to the rib cage is a strong hyperechoic line representing the interface between the pleura and aerated lung

(Fig. 8.9). The pleural line can be visualized sliding against the chest wall during respiration. The vessels related to the chest wall are not routinely evaluated; however with careful inspection, the intercostal artery and vein can be observed (Fig. 8.13) [19]. The intercostal nerves are generally not visible by ultrasound unless involved by a pathologic process.

Congenital Chest Wall Anomalies Vascular Tumors and Malformations Vascular lesions are divided into two major categories, according to the classification scheme of the International Society for the Study of Vascular Anomalies (ISSVA): tumors and malformations [20]. Vascular tumors are categorized into three groups: benign, locally aggressive, or borderline. Vascular malformations, which are nonneoplastic, are categorized into four groups: simple, combined, those of major named vessels, and those associated with other anomalies. A third broad category is used for provisionally unclassified anomalies, such as lesions with features that overlap between tumor and malformation. Ultrasound is highly important in the assessment of vascular anomalies and is usually the first imaging test. It is used

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Table 8.2  Clinical and ultrasound features of selected vascular lesions of the pediatric chest wall Lesion Infantile hemangioma

Congenital hemangioma

Venous malformation

Lymphatic malformation

Clinical presentation Blue-red lesion Appears shortly after birth, proliferates for weeks/ months, involutes beginning at 6–12 months for several years May remain as focal fibrofatty tissue after involution Violaceous mass, may ulcerate Fully formed at birth RICH: 90% involution by 3 months, total involution by 14 months NICH: May grow commensurate with patient PICH: Begins as RICH but does not fully involute and then persists like a NICH Single or multiple lobular bluish masses, compressible

Wide range of size and extent May be identified at birth or in the first 2 years Spontaneous regression possible Sudden enlargement from hemorrhage, infection

Grayscale ultrasound Well-defined, ovoid or lobular shape Solid with variable echogenicity, heterogeneous

Doppler ultrasound Diffusely hypervascular (“lights up”) Low-resistance arterial waveforms

Large, heterogeneous Calcification, hemorrhage, large vessels

Abundant enlarged peripheral vessels, large feeding arteries and draining veins

Slow velocity venous flow or Hypoechoic, spongiform undetectable flow May appear as a collection of vessels Thickened subcutaneous fat Calcified phleboliths No vascularity apart from some flow in Thin-walled cystic spaces septa Debris, fluid-fluid levels Echogenic and mass-like if microcystic

RICH, Rapidly involuting congenital hemangioma; NICH, non-involuting congenital hemangioma; PICH, partially involuting congenital hemangioma

to identify the type of lesion; assess its size, extent, and degree of vascularity; and monitor response to treatment. The grayscale and Doppler features, combined with the clinical appearance, allow for categorization of the lesion and guidance of therapy. Ultrasound features that must be determined include lesion echogenicity; presence of solid tissue, cysts, calcification, or thrombi; compressibility; density of vascularity on color Doppler; and presence of arterial and venous waveforms, with measurement of velocities and resistive indices on spectral Doppler. This section of the chapter does not cover all the diagnoses in the ISSVA classification scheme but does address those entities that are most commonly encountered in the pediatric chest wall (Table 8.2). It is helpful to note that the ultrasound properties of these lesions can be applied to any body part in which they occur. It should also be noted that vascular malformations may occur in combination with each other resulting in a “mixed” lesion with overlapping ultrasound features.

Hemangioma Hemangioma is the most common pediatric vascular neoplasm, of which there are two forms, infantile and congenital [21]. Infantile hemangioma (IH) is the most common vascular lesion in children, with a prevalence of 5–10%, and is far more likely to be seen in the chest wall than congenital hemangioma (CH) [22, 23]. IH develops shortly after birth as a blue-red lesion and then undergoes a proliferative phase over the next few months to 1 year and then an involution phase over the next few years, sometimes leaving behind fibrofatty tissue [23, 24]. Certain large or deep segmental IHs are associated with syndromes and occur in characteristic locations [22]. Examples

include PHACE syndrome (posterior fossa brain malformation; large IH of the face, neck, or scalp; arterial anomalies; cardiac defects and aortic coarctation; and eye anomalies), and LUMBAR syndrome (Lower body IH; Urogenital anomalies; ulceration; Myelopathy; Bony deformities; Anorectal malformation; arterial anomalies; and Renal anomalies) [25]. CHs are present at birth as fully grown masses. There are three types of CH which are characterized by their clinical time course: rapidly involuting congenital hemangioma (RICH), non-involuting congenital hemangioma (NICH), and partially involuting congenital hemangioma (PICH) [26]. Diagnosis of small hemangiomas, which are usually the IH form, can be made on clinical grounds and does not require imaging. For larger lesions with uncertain anatomic extent, ultrasound is performed as the initial assessment. When it develops in the chest wall, IH is usually confined to the subcutaneous tissue [22]. During the proliferative phase, it has a nonspecific grayscale ultrasound appearance, presenting as a well-defined mass, which may be hyperechoic, hypoechoic, or heterogeneous (Figs. 8.14 and 8.15) [27]. Color Doppler demonstrates rich vascularity with high vessel density (greater than five vessels or color pixels per square cm) [28]. Spectral Doppler shows the presence of both arteries and veins, usually with high-velocity, low-resistance arterial waveforms. Although ultrasound is not typically used during the involution phase, the shrinking lesion demonstrates decreased vessel density and hyperechogenic fatty tissue. CHs are usually solitary and tend to be distinct in appearance from IH, in that they are heterogeneous and contain large intralesional vessels which are visible on grayscale, representing arter-

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a

b

Fig. 8.14  Hemangioma in a 4-week-old female. (a) Longitudinal grayscale ultrasound image of the right lateral chest wall shows a well-­defined lesion (calipers) in the subcutaneous fat that is hyperechoic to the skeletal muscle. (b) Transverse color Doppler ultrasound image demonstrates vascularity throughout the lesion, typical of hemangioma

a

ies, dysplastic veins, and venous lakes [21, 29]. Arteriovenous shunting, venous thrombi, and calcifications have also been described [21, 22, 28]. These features are not seen in IH. If IH is multiple with five or more skin lesions identified on physical examination, affected pediatric patients must be screened for the presence of liver hemangiomas using ultrasound [23]. IH does not generally require treatment because it is expected to involute, although treatment may be needed in certain situations, including complications due to growth in high-risk locations (e.g., airway, orbit), local complications (ulceration, hemorrhage), multiple IHs (usually visceral, e.g., the liver), and high-output cardiac failure [30, 31]. Oral propranolol is the usual treatment choice. Secondline therapies include corticosteroids, interferon alpha, vincristine, and pulsed dye laser [30, 31]. Ultrasound is used to assess treatment response, and special attention must be paid to any portions of the lesion that are not visible to the clinician [22]. Treatment of CH depends on observation of changes during the first few days and weeks of life. RICH begins involuting shortly after birth, whereas NICH grows in proportion to the child, although the prognosis is favorable. PICH demonstrates intermediate behavior, initially acting as RICH but evolving to a persistent NICH [26]. Infrequently, therapy for CH may be needed due to symptoms from size, growth, ulceration, bleeding, thrombocytopenia, or heart failure. Treatments include excision, embolization, or pulsed dye laser.

b

c

Fig. 8.15  Hemangioma in a 19-month-old female. (a) Longitudinal grayscale ultrasound image of the right anterior chest wall shows a mildly heterogeneous lesion (calipers) in the subcutaneous fat that is hyperechoic to the skeletal muscle. (b) Longitudinal power Doppler

ultrasound image at the same level shows diffuse vascularity with high density of vessels. (c) Spectral Doppler sample of the lesion reveals low-resistance arterial waveforms

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Venous Malformation Venous malformation (VM) is a low-flow lesion, consisting of dysplastic veins (blood-filled channels) with deficiency of smooth muscle, which form a single or multifocal mass [23, 32]. VM is the most common vascular malformation, usually seen in the skin or subcutaneous tissue; however, it can occur anywhere including deeper structures such as the muscle, bone, and internal organs [21, 33]. Most cases are sporadic, although there are some familial forms that affect both the skin and mucosa, such as the blue rubber bleb nevus syndrome where multiple VMs occur in the gastrointestinal tract [20]. VMs are present at birth and grow with the child; however, they sometimes are not apparent until the child is older

and tend to enlarge during puberty [20, 34]. On clinical examination, VM usually presents as a soft mass with overlying bluish skin discoloration but sometimes may present as a group of dilated superficial veins [20]. There are multifocal and diffuse forms which can involve large areas such as an entire limb. VM may enlarge with a Valsalva maneuver or gravity dependence (change in positioning) and cause pain and swelling after vigorous activity, or thrombophlebitis [20, 21, 34, 35]. On ultrasound, VM appears as a well-defined hypoechoic mass with spongiform echotexture, due to enlarged blood-­ filled spaces with intervening septa (Figs. 8.16 and 8.17) [21]. In some lesions, subcutaneous fat can be seen interdigitating between dysplastic veins [22]. Doppler examination demon-

a

b

M

c R

S

Fig. 8.16  Venous malformation in a 13-year-old male who presented with a bluish skin lesion on the right anterior chest wall. (a) Longitudinal grayscale ultrasound image shows a serpiginous hypoechoic lesion (arrows) in the subcutaneous tissue overlying the muscle (M) and rib (R). (b) Power Doppler ultrasound image at the same level demonstrates

a

a few areas of color signal, with the majority of the lesion appearing avascular due to slow flow. (c) Axial T2-weighted, fat-­suppressed magnetic resonance (MR) image of the anterior chest wall demonstrates the corresponding superficial soft tissue lesion (arrow), with hyperintense signal typical of a venous malformation. S, Sternum

b X

+

+ X

Fig. 8.17  Venous malformation in a 17-year-old male who presented with a left anterior chest wall mass. (a) Transverse grayscale ultrasound image demonstrates a well-defined hypoechoic mass (calipers) with a spongiform echotexture and internal linear septa. There is a shadowing calcification (arrow) in the mass consistent with a phlebolith, which is

pathognomonic of a venous malformation. (b) Axial contrast-enhanced, T1-weighted, fat-suppressed MR image shows the corresponding mass within the left pectoralis musculature. The mass demonstrates diffuse gadolinium uptake and signal voids (arrow) due to phleboliths

8  Chest Wall

strates slow venous flow, sometimes so slow as to be undetectable, although intralesional thrombosis can also be seen [20–22]. Augmentation with compression or Valsalva maneuver can help detect flow [36]. The lesions are usually compressible, in keeping with their venous nature. Although uncommon, the presence of calcified phleboliths is pathognomonic, as they are rarely seen in other vascular anomalies [22, 27]. In cases of uncertain diagnosis or large extent, MR imaging evaluation is required. The deep veins of the involved area must be imaged prior to directed therapy [34]. Treatment is not required for small or asymptomatic VMs but can be indicated in VM complicated by pain, disfigurement, or functional impairment [37, 38]. Supportive therapies include compression garments, analgesics, and anticoagulants in cases with localized intravascular coagulopathy (intralesional thrombus). Directed therapies include sclerotherapy (first-line), surgery (for small, well-defined lesions), and targeted agents such as sirolimus [39]. Ultrasound and/or MR imaging is performed pre- and post-­sclerotherapy to demonstrate efficacy of treatment.

Lymphatic Malformation Lymphatic malformation (LM) is another low-flow vascular malformation consisting of abnormal lymphatic channels, often manifested as dilated endothelial-lined cysts [23]. The individual locules are variable in size, termed macrocystic when >1–2 cm, microcystic when 3 days) progresses to tissue “disarray” [66, 67]. The most common ultrasound finding in cellulitis is “cobblestoning” or branching interstitial fluid, representing hypoechoic fluid that interdigitates between subcutaneous fat lobules in a pattern reminiscent of a cobblestone street (Fig. 8.25) [67, 68]. The subcutaneous tissue also becomes thickened and hyperechogenic, and there is loss of normal architecture with blurring of the planes between the epidermis, dermis, and hypodermis [68]. Color Doppler can demonstrate hyperemia, which is a sign of inflammation. As with all ultrasound studies of the chest wall, comparison to the unaffected side will help in recognition of these abnormalities, especially if they are subtle. The ultrasound findings must be interpreted in consideration of the clinical findings, as some of these features are nonspecific; for example, interstitial fluid is also seen in soft tissue edema from noninfectious causes (e.g., deep venous thrombosis, lymphedema) [69]. In most cases of community-acquired uncomplicated cellulitis, affected children can be treated with oral antibiotics. In more severe infections, including those associated with lethargy, hypotension, and other signs of systemic toxicity, hospitalization and parenteral antibiotics are indicated [64, 70]. Necrotizing fasciitis or gangrenous infections require surgical debridement.

b

SC

M

between the fat lobules, giving rise to a “cobblestone” appearance. (b) Transverse grayscale ultrasound image demonstrates fluid tracking in the plane of the superficial fascia (arrowheads) at the deepest extent of the infectious process. M, Muscle

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Abscess

Neoplastic Disorders of the Chest Wall

Abscess is an uncommon manifestation of chest wall infections in children. A chest wall abscess may develop from progression of purulent cellulitis or as a result of open wounds or thoracic surgery [71]. Children with cellulitis can form abscesses in 48 hours or less [65]. An abscess is a localized collection of pus (white blood cells and bacteria), which is organized into a necrotic central core surrounded by neutrophils, dilated blood vessels, and proliferating fibroblasts. The clinical presentation is similar to cellulitis in terms of localized inflammation. However, in abscesses, physical examination can demonstrate a palpable indurated or nodular area, with fluctuance. Edema and/or cellulitis of the surrounding soft tissues is present. The ultrasound appearance of an abscess, which is not specific to the chest wall, is of a focal fluid collection of variable echogenicity (Fig. 8.26). In a classic abscess, the collection is spherical and surrounded by a thick capsule demonstrating hyperemia. Swirling of fluid during transducer compression indicates the presence of pus and should be captured with a cine clip (Fig. 8.27) [69]. It is important to recognize that not all purulent infections result in classic abscess formation [67]. Some purulent collections, particularly in MRSA infections, are small and irregularly shaped, with ill-defined borders [72]. Additionally, purulence with drainage may be clinically apparent even in the absence of a visible fluid collection on ultrasound [67]. Ultrasound plays an important role in assessment of chest wall soft tissue infections, since identification of an abscess indicates the need for incision and drainage. Antibiotics may be considered as adjunctive therapy [70]. Repeat ultrasound can be performed to assess response to therapy, if needed.

In general, the role of imaging in the workup of chest wall tumors is primarily for localization and extent of disease, as many of the imaging features are nonspecific and tissue sampling is required for definitive diagnosis. MR imaging is often the imaging modality of choice for its high tissue contrast, ability to depict the entire extent of the mass, and identify osseous involvement. However, ultrasound is often performed as the first step in the workup of a clinically suspicious mass, and it is a useful tool for “triage” of cases into benign or possibly malignant categories [73]. Concerning clinical features include new onset or progressive enlargement, pain, size greater than 5 cm, and deep location. Ultrasound features of malignant lesions include

a

Fig. 8.27  Abscess in a 16-year-old female who presented with a nodular area of fluctuance of the anterior chest wall. Transverse color Doppler ultrasound image shows an ovoid fluid collection with posterior acoustic enhancement and peripheral vascularity. The fluid contains numerous low-level echoes, which on real-time scanning demonstrated swirling when light pressure was placed on the transducer. This finding indicates the presence of pus

b

+

+

Fig. 8.26  Abscess in a 17-year-old female who presented with a painful lump on the upper back. (a) Longitudinal grayscale ultrasound image demonstrates a rounded fluid collection (calipers) in the subcutaneous tissue with a thick, irregular echogenic wall. Posterior acoustic enhancement is present indicating the cystic nature of the lesion. There

is inflammation of the surrounding fat with thickening and hyperechogenicity. (b) Transverse color Doppler ultrasound image shows some flow at the edges of the collection and hyperemia of the surrounding subcutaneous tissue

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heterogeneous echotexture, distortion of surrounding anatomy, cortical bone destruction, and “chaotic” or disorganized Doppler flow (neoangiogenesis) [73, 74]. Ultrasound findings can suggest a preoperative diagnosis when they are taken into consideration together with clinical, radiographic, and MR imaging findings [75]. As mentioned earlier in this chapter, CEUS is a promising tool for evaluation of soft tissue masses. Either the presence of homogeneous enhancement or the absence of enhancement correlate with benignity. Heterogeneous enhancement is associated with malignancy [10, 11]. Recent work with ultrasound contrast agents has shown that targeting of enhancing regions improves the diagnostic yield of biopsy [76]. Also promising are early investigations in the pediatric population that indicate that CEUS can be used to assess treatment response of solid malignancies [77].

cial lipomas are well circumscribed with a thin capsule, oblong in shape, and relatively homogeneous in echotexture, aside from occasional delicate hyperechoic bands oriented parallel to the skin surface (Fig. 8.28) [78, 81]. The echogenicity of adipocytic lesions is variable, as it depends on the amount of fat content relative to stroma or other admixed tissue types. However, lipomas represent pure fat except for the fibrous septa (parallel linear bands), and the superficial form is usually isoechoic to the surrounding subcutaneous fat [79]. Some lipomas are hyperechoic or lack the parallel linear bands (Fig. 8.29). There is no posterior acoustic shadowing or enhancement. Although lipomas are supplied by a rich vascular network, color Doppler flow is usually undetectable, likely due to compression of vessels by large adipocytes [78, 79, 81] Management of lipoma depends on location and size. In the appropriate clinical setting, ultrasound can be diagnostic for lipomas under 5 cm. However, any lesions that are larger and deep, have atypical features, or change clinically warrant repeat ultrasound and/or MR imaging [5]. The majority of superficial lipomas are asymptomatic and do not require treatment; however, when indicated, surgical excision is curative [79]. Deep lipomas are also treated with excision. Incomplete resection and local recurrence are known complications, due to the more expansile nature of these lesions [78]. Deep lipomas are larger and more variable in appearance by ultrasound than classic lipomas. They should be further assessed with MR imaging for confirmation of diagnosis and surgical planning [78, 81].

Benign Chest Wall Neoplasms Lipoma Lipoma is a benign tumor composed of mature fat cells and is the most common soft tissue neoplasm [78]. The chest wall and trunk are relatively common sites for benign lipomas, especially the upper back. Most lipomas are superficial, i.e., subcutaneous, and are smaller than 5 cm [78, 79]. Deep lipomas can arise below the superficial fascia and be located within or between muscles. However, these are less frequent and are especially rare in the chest wall [78–80]. The term lipomatosis refers to an unencapsulated version which is diffusely proliferative and infiltrates the musculature. Clinical examination is usually sufficient for diagnosis of a superficial lipoma, which is palpable as an ovoid, mobile, rubbery, or “doughy” mass [5, 78]. On ultrasound, superfi-

Mesenchymal Hamartoma Mesenchymal hamartoma (MH) is an exceedingly rare lesion arising in the chest wall of newborns and young infants, and

a

b

+

+

LD

Fig. 8.28  Lipoma in a 12-year-old female who presented with a soft mobile mass of the left lateral chest wall. (a) Longitudinal grayscale ultrasound image shows a well-defined oblong subcutaneous mass (calipers) overlying the latissimus dorsi (LD) muscle, with its long axis

oriented parallel to the skin surface. The echotexture is reminiscent of subcutaneous fat, and multiple thin echogenic bands are seen throughout the lesion. (b) Color Doppler ultrasound image at the same level shows no vascularity in the mass (minor flash artifact is noted)

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Fig. 8.29  Lipoma with alternative appearance in a 19-year-old male who presented with a long-standing posterior chest wall mass. (a) Longitudinal grayscale ultrasound image demonstrates an oblong subcutaneous mass (calipers), which is fairly homogeneous but mildly

hyperechoic relative to the adjacent muscle and fat. A few thin internal echogenic bands are present. (b) Transverse color Doppler ultrasound image shows lack of flow in the majority of the mass, except for one focus of vascularity in its right lateral aspect

occasionally identified in the prenatal period. MH is a benign proliferation of skeletal tissue arising from a rib, with a prominent cartilaginous component [82]. Characteristic features include intrathoracic projection with a large extrapleural mass, internal calcification, and secondary aneurysmal bone cyst (ABC) formation with multiple hemorrhage-filled cavities. There is wide variability in clinical presentation of MH, with some lesions detected incidentally in asymptomatic pediatric patients and others causing extreme respiratory distress [83, 84]. Symptoms depend on the size of the lesion and degree of mass effect on the lungs and heart. Physical findings are also varied, ranging from a minor chest wall deformity to a visible mass. Ultrasound features of MH are nonspecific and have primarily been reported for prenatal cases [85]. On prenatal ultrasound, MH appears as a rounded, heterogeneous intrathoracic mass with a hyperechoic capsule, located adjacent to the posterior ribs [85, 86]. The mass grows as the pregnancy ­progresses, and may become hypoechoic centrally, presumably due to hemorrhage [85]. Large lesions with mass effect can cause mediastinal shift and pulmonary hypoplasia [86]. MH can be a source of pleural bleeding and a pleural effusion may be identified on ultrasound [84, 85]. MH may be confused with a congenital lung lesion due to its intrathoracic extension or with a malignant lesion due to its size and distortion of the chest [84]. However, fetal MR imaging can identify chest wall involvement and the presence of secondary ABC and/or hemorrhage with fluid-fluid levels, features which are highly suggestive of MH [82, 86]. Postnatal ultrasound features have not been well-described. Radiographs and CT are more useful in the postnatal period to demonstrate the costal origin of the mass, erosion or molding of adjacent bones, and osteoid or chondroid matrix [82, 84, 86]. Although MH appears aggressive on imaging and histopathology, it is a benign lesion and conservative man-

agement is favored. Lesions have usually reached peak size at birth and shrink within the first 2 years of life [84, 85, 87]. However, clinically unstable patients require tumor resection via thoracotomy and may also need reconstruction of the chest wall [84]. Surgery should be considered in children with substantial physical disfigurement [82]. Complete resection is curative. Radiofrequency thermoablation can also be performed [24, 82].

Malignant Chest Wall Neoplasms The ultrasound features of chest wall malignancies described below have been extrapolated from established features of extremity tumors, because of their rare incidence in the chest wall and paucity of specific literature, particularly in the pediatric population.

Rhabdomyosarcoma Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children, accounting for one-half of all pediatric sarcomas [88]. It arises from primitive mesenchyme that differentiates into cells simulating striated muscle, and can occur in any body part excluding bone [48, 89, 90]. In the chest wall, it originates from the musculature, and the absence of a costal origin helps distinguish it from other types of sarcoma. Most pediatric chest wall RMS are of the alveolar or embryonal subtype [89, 90]. RMS can occur at any age but is most common in young children aged 2–5 years [89]. RMS of the chest wall has also been identified by prenatal ultrasound [91, 92]. RMS presents as a mass that is usually non-tender on palpation although it can be a source of chest pain [89, 93]. Signs and symptoms of metastatic disease include lymphadenopathy, fatigue, weight loss, and low blood counts.

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a

b X

+

+

X

Fig. 8.30  Rhabdomyosarcoma in a 21-month-old female who presented with swelling of the chest wall. (a) Transverse grayscale ultrasound image shows a solid chest wall mass (calipers) with heterogeneous echotexture and poor definition of its right lateral margin. (b) Axial contrast-enhanced,

T1-weighted, fat-suppressed MR image demonstrates the mass (arrows) in the upper right chest wall and axilla, which has heterogeneous signal and surrounding infiltrative enhancement. Biopsy showed rhabdomyosarcoma with involvement of subpectoral lymph nodes

On ultrasound, RMS typically appears as a heterogeneous solid mass, which may have an irregular contour (Fig. 8.30). Internal vascularity is present on color Doppler. Tumor necrosis can occur, resulting in anechoic, avascular cystic spaces. There is no shadowing calcification within the tumor; however, 20% of affected patients have bone invasion [94]. The embryonal subtype can invade the mediastinum. Prognosis of RMS depends on age, histologic type (with alveolar type having the poorest prognosis), degree of differentiation, DNA analysis, tumor size, and extent of disease, including resection margins [89, 90]. RMS of the chest wall has an unfavorable prognosis, with a tendency for local recurrence and metastasis [88, 90]. Treatment of RMS requires a coordinated approach that includes chemotherapy, surgery, and radiation [90]. When used as part of serial imaging during therapy, ultrasound can assess changes in tumor size, although there are no specific changes in tumor echotexture that occur [95].

of tumors in the Ewing family share a common karyotype abnormality with a balanced 11;22 chromosomal translocation [33, 89, 97]. The most common location for ES of the bone to arise in the chest wall is from a rib. It can also develop from the sternum, scapula, and clavicle [96]. The peak age of incidence is 10–15  years, and the presentation includes nonspecific findings of pleuritic chest pain and swelling or a palpable mass [97]. Fever and an elevated erythrocyte sedimentation rate can also be present. These findings as well as the radiographic appearance can mimic an infectious process. Ultrasound can be used to identify the soft tissue component of the tumor, which is typically larger than the intraosseous component (Fig. 8.31) [45]. With careful inspection, the osseous origin of the tumor can be identified by demonstrating that the mass surrounds the bone, causes cortical irregularity or erosion, and exhibits a “sunburst” appearance with an array of echogenic lines arising perpendicular to the bone [98, 99]. The sunburst appearance corresponds to aggressive periosteal reaction, which is also seen on radiographs. Calcification in the soft tissue component is uncommon [97]. Doppler vascularity is generally present, with high arterial velocities in the periphery of the lesion [98–100]. Tumors with a relatively small extraosseous portion are homogeneous and hypoechoic [101]. Large tumors undergo necrosis and hemorrhage, becoming heterogeneous in echotexture. In the case of necrotic tumors, ultrasound is helpful in identifying high-­yield areas of non-necrotic solid tissue for biopsy [97, 100]. In extraosseous ES, the soft tissue tumor is usually hypoechoic and may contain anechoic regions of hemor-

Ewing Sarcoma The Ewing sarcoma (ES) family of tumors is the most common group of chest wall malignancies in the pediatric population. It includes classic Ewing sarcoma of the bone, extraosseous Ewing sarcoma, and primitive neuroectodermal tumor (PNET) [96]. The extraosseous form is rare; however, the chest wall is one of the most common locations, where it is termed an Askin tumor [89, 97]. ES tumors are aggressive small round blue cell tumors, thought to arise from embryonal neural crest cells. PNET is considered to have more neuroectodermal differentiation than classic ES; however, 90%

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a

Fig. 8.31  Ewing sarcoma of the rib in a 6-year-old boy with abdominal pain, weight loss and fever. (a) Transverse grayscale ultrasound image shows a heterogeneous soft tissue mass encircling a rib (arrow)

rhage or necrosis [97, 102]. Intratumoral calcification can occur in up to 25% of cases. Doppler vascularity is present. Treatment of ES includes initial chemotherapy and surgical resection, which may be followed by radiation therapy [90]. Wide excision usually includes parts of adjacent ribs, musculature, and pleura, with large defects necessitating chest wall reconstruction. While ultrasound is not used for staging purposes, it can be used to monitor the extraosseous portion of the tumor during therapy. On MR imaging a decrease in tumor vascularity and enhancement indicate response to chemotherapy [97]. Similarly, a decrease in intratumoral blood flow can be seen on Doppler ultrasound, as well as increased arterial resistive indices on spectral analysis [97, 100, 103]. However, Doppler findings are not consistent across studies, and in general, ultrasound is not widely used for the purpose of follow-up.

Osteosarcoma Osteosarcoma (OS) is a high-grade malignant, bone-forming mesenchymal tumor predominantly affecting adolescents and young adults. Primary thoracic OS is rare, but it can arise from the ribs, sternum, scapula, or clavicle [4, 33, 93, 96]. OS usually presents as a painful mass. When it affects the chest wall, it can also cause respiratory distress [94, 105]. The rare extraosseous form of OS can also present in the chest wall but is more often seen in older adults after radiation or other toxic exposures [93, 104, 105]. Since OS is primarily intramedullary in location, the role of ultrasound is limited. When ultrasound is performed, it

b

with prominent posterior acoustic shadowing (arrowhead). (b) Contrastenhanced axial computed tomography (CT) image shows the mass arising from the left 12th rib that displays lytic destruction (arrow)

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Fig. 8.32  Osteosarcoma of the chest wall in a 10-year-old female who presented with known multifocal tumor. Transverse grayscale ultrasound image demonstrates an irregularly shaped mass (calipers) with coarse echogenic regions and strong posterior acoustic shadowing due to osteoid matrix

can demonstrate a poorly demarcated, heterogeneous, mixed echogenicity mass [100, 106]. Necrotic regions appear anechoic [101]. Central irregular hyperechoic areas with posterior acoustic shadowing correspond to osteoid matrix that is seen on radiography (Fig. 8.32). In some cases, ultrasound can also demonstrate cortical destruction by identifying defects in the echogenic surface of the bone, as well as the sunburst or “hair-on-end” pattern of periosteal reaction,

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Fig. 8.33  Lymphoma in an 18-year-old male who presented with a palpable anterior chest wall mass due to relapsed Hodgkin’s disease. (a) Transverse grayscale ultrasound of the palpable region demonstrates a

solid lobular mass (calipers) with heterogeneous echotexture. (b) Axial contrast-enhanced CT image through the lower chest reveals that the lesion is a protruding left cardiophrenic nodal mass (arrow). L, Liver

Fig. 8.34 Chest wall mass in a 2-year-old male with stage III Burkitt lymphoma. Sagittal grayscale ultrasound image shows several hypoechoic masses (arrows), some ovoid shaped and some ill-defined. There is thickening and increased echogenicity of the surrounding soft tissues

Lymphoma Lymphoma of the chest wall is unusual, accounting for only 2% of chest wall tumors. It usually occurs in adults, and incidence rates in children are unknown [90, 94]. Non-­Hodgkin lymphoma (NHL), specifically diffuse large B-cell lymphoma (DLBCL), is the most common diagnosis, although Hodgkin lymphoma as well as a wide variety of other lymphoid neoplasms can present with a chest wall mass [110–113]. Primary extranodal chest wall lymphoma can arise from the bone, muscle, or breast. Secondary chest wall involvement is more common and results from direct invasion of lymphoma from the mediastinum, pleura, or lung [110, 114]. Widespread disseminated lymphoma can affect the lymph node groups of the chest wall or spread to the ribs, sternum, spine, muscle, or skin. Presenting symptoms of chest wall lymphoma include localized pain, palpable mass, or pathologic fracture. Of note, leukemia, particularly acute lymphoblastic leukemia, can have a similar presentation and is a diagnostic consideration in children with chest wall pain or multiple destructive bone lesions [115]. Chest wall lymphoma can be seen on ultrasound imaging of the bone, muscle, or lymph nodes (Figs. 8.33 and 8.34). In general, the ultrasound findings are nonspecific and cannot be distinguished from other malignancies or even an inflammatory process [110]. Ultrasound can identify nodal enlargement, with the most common chest wall sites being the pectoral and subpectoral groups [114]. Lymphoma of the bone tends to have an imaging appearance similar to other small round blue cell neoplasms such as ES, with permeative osseous destruction [110]. As described for chest wall sarcomas, these lesions can potentially be identified by ultrasound if a substantial extraosseous compo-

with echogenic spicules perpendicular to the bone similar to those seen in ES [107]. On Doppler imaging, OS is hypervascular, with predominantly peripheral flow that demonstrates high velocity and low resistance [100, 101]. However, tumors with >90% necrosis show less neovascularity [108]. Treatment of OS usually consists of neoadjuvant chemotherapy and resection, sometimes followed by postoperative chemotherapy [93]. OS is less sensitive to radiation compared to other tumors, although radiation may be given after incomplete resection [90, 93]. OS of the chest wall has a poor prognosis, with greater rates of recurrence and metastatic disease compared to OS of the extremities [94, 104, 109].

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nent is present. Primary lymphoma of the muscle is a rare entity that affects older adults and on ultrasound may appear as a discrete intramuscular mass or diffuse infiltration and enlargement of the muscle [110, 116]. This is a scenario in which ultrasound of the contralateral muscle for comparison is helpful in detecting the abnormality as an asymmetry. Isolated chest wall lymphoma requires biopsy for diagnosis. Biopsy may not always be required in patients with known lymphoma, but identification of chest wall involvement is important for disease staging and treatment. Chemotherapy is the mainstay of treatment, with or without radiotherapy [90].

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lytic bone lesions, for which cross-sectional imaging evaluation is required.

Traumatic Disorders of the Chest Wall Hematoma

Metastases Metastatic disease is responsible for a minority of chest wall lesions in children [24]. Metastases to bones or soft tissues of the chest wall usually occur in patients with known widely disseminated disease [96]. The primary diagnostic consideration is neuroblastoma, which can involve the chest wall through direct extension from the posterior mediastinum or through hematogenous metastases to the ribs or vertebrae [24]. Other tumors that can metastasize to the chest wall include rhabdomyosarcoma, lymphoma, and leukemia. Soft tissue lesions generally demonstrate ultrasound features similar to the primary tumor from which they originate, although most appear as a nonspecific solid mass (Fig. 8.35). The majority of chest wall metastases consist of

A hematoma is defined as a localized extravascular collection of blood. In the chest wall, a hematoma can occur in the subcutaneous tissue or muscle. Etiologies include trauma, surgery, bleeding disorders, and anticoagulation [6]. Substantial trauma is usually required to cause a chest wall hematoma; however, hemorrhage can also occur within chest wall neoplasms and vascular malformations, either spontaneously or with minor trauma. Intramuscular hematoma is a rare finding and can be seen in the setting of a bleeding diathesis such as hemophilia or after athletic injuries such as trauma to the pectoralis muscles in weight lifters. Children with chest wall hematoma are likely to experience localized pain and swelling with bruising over the site. The ultrasound appearance of hematoma depends on its location and age, although hematomas in different tissues tend to show common changes on serial ultrasound examinations [117]. In the subcutaneous tissues, acute hematomas can have ill-defined borders and variable internal echo-

Fig. 8.35  Metastatic disease of the chest wall in a 16-year-old female with chronic liver disease and hepatocellular carcinoma. (a) Transverse grayscale ultrasound image of the posterolateral left chest shows a heterogeneous soft tissue mass (calipers), which encompasses an area of shadowing calcification (white arrow). The mass also contains an

anechoic area of necrosis (black arrow). (b) Sagittal contrast-­enhanced CT image of the thorax through the same region shows a destructive soft tissue mass (arrows) centered at the left tenth rib. The remaining spicules (arrowhead) of the rib inside the mass correspond to the calcification seen on ultrasound

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Fig. 8.36  Acute hematoma in a 20-year-old male who presented with chest wall swelling after trauma. (a) Longitudinal grayscale ultrasound image shows an ovoid mass-like intramuscular structure (calipers)

genicity (hypoechoic, intermediate, or hyperechoic) and are avascular on color Doppler (Fig.  8.36). As the hematoma subsequently liquefies, it tends to become hypoechoic or anechoic [6]. Fluid-debris levels may appear due to separation of serum and cellular debris. Over the next 3–4 weeks, the collection becomes more heterogeneous and can demonstrate septations due to fibrin strands and solid-appearing areas due to retracting clot (Fig.  8.37) [118, 119]. As the hematoma resorbs, it becomes smaller with increased echogenicity at the periphery. The time course for resolution is variable, and in some cases, hematomas become organized with a fibrous capsule that prevents blood resorption, resulting in a palpable hard mass. Ultrasound of organized hematoma can show a whorled appearance, with variable amounts of liquid and solid tissue, and even internal Doppler vascularity, making the diagnosis more challenging. Intramuscular hematomas of the chest wall can result from muscle tears or tendon injuries and can appear as a hyperechoic mass with shaggy margins inside the body of the muscle or as diffuse enlargement of the muscle with loss of normal filamentous echotexture [41, 120, 121]. With healing, there is a variety of outcomes, including hyperechoic scar tissue, myositis ossificans with acoustic shadowing, and intramuscular cysts [121]. Usually, hematomas spontaneously resolve with conservative management. Ultrasound-guided aspiration can be considered when more rapid resolution is needed [122]. Rarely, hematomas may instead slowly expand, a phenomenon that is termed chronic expanding hematoma [123]. This lesion is thought to be caused by bleeding from proliferating

overlying the left seventh rib (R) that is isoechoic to the muscle. (b) Transverse power Doppler ultrasound image shows no flow within the lesion, consistent with an early phase of hemorrhage

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M

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X M

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Fig. 8.37  Subacute hematoma in a 19-year-old male who presented with chest wall swelling after trauma. (a) Extended field of view longitudinal grayscale ultrasound image demonstrates a large heterogeneous collection (calipers) in the pectoralis musculature (M). (b) Transverse grayscale ultrasound image reveals low-level particulate echoes throughout the collection, as well as irregular echogenic, solid-appearing material (asterisks) due to retracting clot

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vessels within the granulation tissue along the fibrous capsule of the hematoma [124]. Ultrasound demonstrates a nonspecific complex mass with peripheral solid nodules and vascularity, and biopsy may be needed to distinguish this lesion from a sarcoma [125]. There is little literature on this in children. It has been reported to occur in the chest wall of adults after trauma and surgery [126–128].

Rib Fracture Rib fractures are the most common traumatic injury of the thorax and are typically caused by blunt force [129]. Other etiologies include stress/overuse injury, pathologic fractures due to demineralization or neoplasm, and child abuse. The most common presenting symptom is pain. Although plain radiographs are usually obtained to assess acute rib fractures, 50% of fractures may not be visible at presentation [61, 129]. Additionally, fractures of the costal cartilage cannot be demonstrated on radiography. Ultrasound is more sensitive than radiography and can be a useful tool in these situations [130, 131]. The primary ultrasound finding of acute rib fracture is a discontinuity of the linear echogenic line of the anterior cortex, which may also have a step-off depending on the degree of displacement [61]. This is best demonstrated with the probe held parallel to the long axis of the rib [132]. Costal cartilage fractures have similar findings except that the cartilage margins are thinner and less echogenic than the bone [133]. Some rib fractures with prominent discontinuity may demonstrate a focal acoustic shadow at the level of the fracture, a sign that has been referred to as the “chimney phenomenon” [61]. Hypoechoic fluid collections representing acute hematoma may be seen adjacent to the fracture. It is helpful to also screen for adjacent fractures by scanning the rib levels above and below and to perform a brief ultrasound survey of the ipsilateral thoracic cavity to identify any associated pleural effusion or hemothorax. Fractures of the lower ribs (ribs 9–12) can also have associated injuries of the liver or spleen, which may be recognized incidentally during scanning [129]. At times, the only indication of rib fracture is the presence of signs of healing on follow-up imaging. In the healing stage of rib fracture, ultrasound can demonstrate callus formation, which appears as a calcific prominence of the rib with pronounced acoustic shadowing (Fig.  8.38). In the absence of reported trauma, healing fractures on ultrasound can mimic other rib lesions. For example, occult costal cartilage fractures can present weeks or months after initial injury as a parasternal mass and be mistaken for malignancy on imaging and histology [133, 134]. Therefore, the ultrasound findings should be interpreted in the context of a detailed clinical history.

Fig. 8.38  Healing rib fracture in a 5-year-old male who presented with a painful mass and history of injury 2 weeks previously. Radiographs at the time of injury were negative. (a) Transverse grayscale ultrasound image of the palpable area demonstrates coarse calcification with strong posterior acoustic shadowing typical of bone. (b) Longitudinal grayscale ultrasound image at the same level shows that the mass (arrows) overlies an angular deformity of a rib (R) and represents the callus of a healing occult fracture

While ultrasound is more sensitive than radiography for rib fracture, in current practice, it is not routinely used for all cases of thoracic trauma. Its most efficient use is probably in the setting of minor trauma, to identify rib fractures in hemodynamically stable patients in whom there is high clinical suspicion but negative radiography. Tenderness during scanning, obesity, and breast tissue can sometimes be limiting factors [132]. In pediatric patients with higher-level trauma, CT should be used instead as the initial modality as it is sensitive for fractures as well as associated complications. Uncomplicated rib fractures are managed conservatively with pain control. The presence of multiple fractures is considered an indicator of more severe trauma, and additional interventions may be required for concomitant injuries.

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Examples include thoracostomy for pneumothorax or hemothorax, intubation of patients with respiratory distress due to chest wall instability, and embolization of active bleeding from the intercostal arteries.

Foreign Bodies Foreign bodies of the chest wall are rare but may encompass a broad range of items. In children, potential sources of retained foreign bodies include penetrating wounds (e.g., knives, glass), traffic accidents, gunshot injuries, acupuncture, and others [135, 136]. Foreign bodies can also result from self-embedding behavior, a rare form of self-injury seen in adolescents with psychiatric illness [135, 137]. Pediatric patients with retained foreign bodies usually present with pain at the time of the inciting injury. In some cases, foreign bodies are unrecognized and may not become symptomatic until long after the initial wound has healed [135]. Iatrogenic foreign bodies that may be seen in the pediatric chest wall include therapeutic devices such as subcutaneous chemotherapy ports, tunneled central lines, ventriculoperitoneal shunt catheters, vagal nerve stimulators, cardiac pacemakers, implantable defibrillators, and orthopedic hardware.

a

Certain foreign bodies such as wood and plastic are non-­ radiopaque. Ultrasound offers an advantage over plain radiography for detection of these objects. It can also be helpful in providing more accurate localization of radiopaque foreign bodies. In addition, ultrasound is an important tool for assessing complications such as infection (abscess) and granuloma formation. Foreign bodies appear as hyperechoic structures with clean or dirty posterior acoustic shadowing, commonly linear in shape (Figs. 8.39 and 8.40) [122, 135, 138, 139]. Orientation of the probe parallel to the foreign body provides the best ultrasound demonstration of its length; however, perpendicular scanning is optimal for identifying the acoustic shadow [138]. Metal and glass objects can produce a reverberation artifact or “comet-tail” artifact [135]. Foreign bodies that have been retained for 24  hours or more can elicit a surrounding inflammatory reaction [138]. On ultrasound, a hypoechoic halo can develop around the object, representing edema, granulation tissue, or fluid collection (Fig. 8.39). Ultrasound can also detect fluid collections and signs of infection associated with therapeutic devices of the chest wall (Fig. 8.40). The decision to remove a chest wall foreign body depends on multiple factors. Indications include pain, infection, and migration, as well as sharp objects positioned in critical locations, e.g., near pleura, nerves, or blood vessels. Organic for-

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Fig. 8.39  Retained foreign body in a 16-year-old male who presented with chest wall pain and a remote history of a gunshot wound. (a) Sagittal grayscale ultrasound image of the left anterior chest wall demonstrates punctate and linear echogenic foci (white arrow) with posterior acoustic

shadowing (black arrows), within the pectoralis major muscle. There is an irregular fluid collection (arrowheads) surrounding the foreign body. R, Rib. (b) Coned-down view of a frontal chest radiograph shows metallic shrapnel in the chest which corresponds to the ultrasound findings

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Fig. 8.40  Retained foreign body in a 15-year-old female who presented with chest wall pain and drainage after pacemaker removal. (a) Sagittal grayscale ultrasound image through the left anterior chest wall shows two echogenic structures (arrow and arrowhead) with posterior acoustic shadowing, representing abandoned pacemaker leads. Reverberation artifact from one of the foreign bodies (arrow) is visible, which can be caused by

metal. The leads are surrounded by a hypoechoic, halo-like fluid collection. There is also inflammatory change in the adjacent subcutaneous fat. (b) Sagittal color Doppler ultrasound image taken slightly lateral to image (a) shows one of the leads (arrow) contiguous with an abscess (asterisk) that extends to the skin surface

10. Gay F, Pierucci F, Zimmerman V, Lecocq-Teixeira S, Teixeira P, Baumann C, et al. Contrast-enhanced ultrasonography of peripheral soft-tissue tumors: feasibility study and preliminary results. Diagn Interv Imaging. 2012;93(1):37–46. 11. Gruber L, Loizides A, Luger AK, Glodny B, Moser P, Henninger B, et al. Soft-tissue tumor contrast enhancement patterns: diagnostic value and comparison between ultrasound and MRI. AJR Am J Roentgenol. 2017;208(2):393–401. 12. Oebisu N, Hoshi M, Ieguchi M, Takada J, Iwai T, Ohsawa M, et al. Contrast-enhanced color Doppler ultrasonography increases diagnostic accuracy for soft tissue tumors. Oncol Rep. 2014;32(4):1654–60. References 13. Stramare R, Gazzola M, Coran A, Sommavilla M, Beltrame V, Gerardi M, et al. Contrast-enhanced ultrasound findings in soft-­ 1. Saini V, Samra T.  Ultrasound guided supraclavicular subclavian tissue lesions: preliminary results. J Ultrasound. 2013;16(1):​21–7. cannulation: a novel technique using “hockey stick” probe. J Emerg 14. Ryan S.  Embryology and anatomy of the neonatal chest. In: Trauma Shock. 2015;8(1):72–3. Donoghue V, editor. Radiological imaging of the neonatal chest. 2. Cox M, Soudack M, Podberesky DJ, Epelman M. Pediatric chest 2nd ed. Berlin, Heidelberg. Springer; 2008. ultrasound: a practical approach. Pediatr Radiol. 2017;47(9):​ 15. Garriock RJ, Chalamalasetty RB, Kennedy MW, Canizales LC, 1058–68. Lewandoski M, Yamaguchi TP. Lineage tracing of n­ euromesodermal 3. Szabo TL, Lewin PA. Ultrasound transducer selection in clinical progenitors reveals novel Wnt-dependent roles in trunk progeniimaging practice. J Ultrasound Med. 2013;32(4):573–82. tor cell maintenance and differentiation. Development. 2015;​ 4. Lee RK, Griffith JF, Ng AW, Sitt JC. Sonography of the chest wall: 142(9):1628–38. a pictorial essay. J Clin Ultrasound. 2015;43(9):525–37. 16. Sadler TW, Langman J.  Langman’s medical embryology. 12th 5. Wagner JM, Rebik K, Spicer PJ. Ultrasound of soft tissue masses ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & and fluid collections. Radiol Clin North Am. 2019;57(3):657–69. Wilkins; 2012. Chapter 10, The axial skeleton; p. 133–44. 6. Carra BJ, Bui-Mansfield LT, O'Brien SD, Chen DC. Sonography 17. van der Merwe AE, Weston DA, Oostra RJ, Maat GJ. A review of musculoskeletal soft-tissue masses: techniques, pearls, and pitof the embryological development and associated developmental falls. AJR Am J Roentgenol. 2014;202(6):1281–90. abnormalities of the sternum in the light of a rare palaeopathologi 7. Moore KL, Agur AMR, Dalley AF. Clinically oriented anatomy. cal case of sternal clefting. Homo. 2013;64(2):129–41. 8th ed. Philadelphia: Wolters Kluwer; 2018. Chapter 4, Thorax; 18. Chauvin NA, Ho-Fung V, Jaramillo D, Edgar JC, Weiss PF. p. 290–403. Ultrasound of the joints and entheses in healthy children. Pediatr 8. McCarville MB, Kaste SC, Hoffer FA, Khan RB, Walton RC, Radiol. 2015;45(9):1344–54. Alpert BS, et  al. Contrast-enhanced sonography of malignant 19. Gorg C, Bert T, Gorg K, Heinzel-Gutenbrunner M. Colour Doppler pediatric abdominal and pelvic solid tumors: preliminary safety ultrasound mapping of chest wall lesions. Br J Radiol. 2005;​ and feasibility data. Pediatr Radiol. 2012;42(7):824–33. 78(928):303–7. 9. Stenzel M, Mentzel HJ.  Ultrasound elastography and contrast-­ 20. Wassef M, Blei F, Adams D, Alomari A, Baselga E, Berenstein enhanced ultrasound in infants, children and adolescents. Eur J A, et al. Vascular anomalies classification: recommendations from Radiol. 2014;83(9):1560–9.

eign bodies (e.g., wood) and contaminated wounds are particularly prone to infection [139]. In an appropriate clinical setting, ultrasound-guided percutaneous removal can be attempted. Surgery is an alternative option; however, ultrasound is still useful to provide guidance for marking the incision site.

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268 61. Smereczynski A, Kolaczyk K, Bernatowicz E.  Chest wall  underappreciated structure in sonography. Part II: non-cancerous lesions. J Ultrason. 2017;17(71):275–80. 62. Kurihara Y, Yakushiji YK, Matsumoto J, Ishikawa T, Hirata K.  The ribs: anatomic and radiologic considerations. Radiographics. 1999;19(1):​105–19. quiz 51–2 63. Hayeri MR, Ziai P, Shehata ML, Teytelboym OM, Huang BK. Soft-tissue infections and their imaging mimics: from cellulitis to necrotizing fasciitis. Radiographics. 2016;36(6):1888–910. 64. Bystritsky R, Chambers H.  Cellulitis and soft tissue infections. Ann Intern Med. 2018;168(3):ITC17–32. 65. Nelson CE, Kaplan S, Bellah RD, Chen AE. Sonographically occult abscesses of the buttock and perineum in children. Pediatr Emerg Care. 2017. https://doi.org/10.1097/PEC.0000000000001294. 66. Chao HC, Lin SJ, Huang YC, Lin TY. Sonographic evaluation of cellulitis in children. J Ultrasound Med. 2000;19(11):743–9. 67. Nelson CE, Chen AE, Bellah RD, Biko DM, Ho-Fung VM, Francavilla ML, et  al. Ultrasound features of purulent skin and soft tissue infection without abscess. Emerg Radiol. 2018;25(5):​ 505–11. 68. O’Rourke K, Kibbee N, Stubbs A. Ultrasound for the evaluation of skin and soft tissue infections. Mo Med. 2015;112(3):202–5. 69. Adhikari S, Blaivas M. Sonography first for subcutaneous abscess and cellulitis evaluation. J Ultrasound Med. 2012;31(10):1509–12. 70. Stevens DL, Bisno AL, Chambers HF, Dellinger EP, Goldstein EJ, Gorbach SL, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(2):e10–52. 71. Sakran W, Bisharat N.  Primary chest wall abscess caused by Escherichia coli costochondritis. Am J Med Sci. 2011;342(3):​ 241–6. 72. Gaspari RJ, Blehar D, Polan D, Montoya A, Alsulaibikh A, Liteplo A. The Massachusetts abscess rule: a clinical decision rule using ultrasound to identify methicillin-resistant Staphylococcus aureus in skin abscesses. Acad Emerg Med. 2014;21(5):558–67. 73. Lakkaraju A, Sinha R, Garikipati R, Edward S, Robinson P. Ultrasound for initial evaluation and triage of clinically suspicious soft-tissue masses. Clin Radiol. 2009;64(6):615–21. 74. Bodner G, Schocke MF, Rachbauer F, Seppi K, Peer S, Fierlinger A, et al. Differentiation of malignant and benign musculoskeletal tumors: combined color and power Doppler US and spectral wave analysis. Radiology. 2002;223(2):410–6. 75. Nagano S, Yahiro Y, Yokouchi M, Setoguchi T, Ishidou Y, Sasaki H, et al. Doppler ultrasound for diagnosis of soft tissue sarcoma: efficacy of ultrasound-based screening score. Radiol Oncol. 2015;49(2):135–40. 76. Loizides A, Widmann G, Freuis T, Peer S, Gruber H. Optimizing ultrasound-guided biopsy of musculoskeletal masses by application of an ultrasound contrast agent. Ultraschall Med. 2011;32(3):​ 307–10. 77. McCarville MB, Coleman JL, Guo J, Li Y, Li X, Honnoll PJ, et  al. Use of quantitative dynamic contrast-enhanced ultrasound to assess response to antiangiogenic therapy in children and adolescents with solid malignancies: a pilot study. AJR Am J Roentgenol. 2016;206(5):933–9. 78. Murphey MD, Carroll JF, Flemming DJ, Pope TL, Gannon FH, Kransdorf MJ. From the archives of the AFIP: benign musculoskeletal lipomatous lesions. Radiographics. 2004;24(5):1433–66. 79. Burt AM, Huang BK. Imaging review of lipomatous musculoskeletal lesions. SICOT J. 2017;3:34. 80. Sheybani EF, Eutsler EP, Navarro OM. Fat-containing soft-tissue masses in children. Pediatr Radiol. 2016;46(13):1760–73. 81. Navarro OM.  Imaging of benign pediatric soft tissue tumors. Semin Musculoskelet Radiol. 2009;13(3):196–209. 82. Groom KR, Murphey MD, Howard LM, Lonergan GJ, Rosado-­ De-­Christenson ML, Torop AH. Mesenchymal hamartoma of the

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8  Chest Wall 105. Qian J, Zhang XY, Gu P, Shao JC, Han BH, Wang HM. Primary thoracic extraskeletal osteosarcoma: a case report and literature review. J Thorac Dis. 2017;9(12):E1088–95. 106. Kabg B, Zeng H, Tang X, Xiong A, Ma Z, Liu G. Ultrasonographic evaluation of osteosarcomas. J Huazhong Univ Sci Technolog Med Sci. 2006;26(5):629–32. 107. Loberant N. Sonographic hair-on-end sign in osteosarcoma. J Clin Imaging Sci. 2015;5:42. 108. Lin YH, Chiou HJ, Chen WM, Yen CC, Chou YH, Hung GY, et al. Color Doppler ultrasonography evaluation for chemotherapy treatment response of osteogenic sarcoma. Ultrasound Med Biol. 2012;38(2):202–8. 109. Fatimi SH, Khawaja RD, Majid Z. Giant osteosarcoma of chest wall requiring resection and pneumonectomy. Asian Cardiovasc Thorac Ann. 2014;22(7):875–7. 110. Bligh MP, Borgaonkar JN, Burrell SC, MacDonald DA, Manos D. Spectrum of CT findings in thoracic extranodal non-Hodgkin lymphoma. Radiographics. 2017;37(2):439–61. 111. Das DK, Pathan SK, Al-Waheeb SKM, Ali AE, Joneja M, Al-Kanderi MG, et al. Chest wall lymphomas: fine needle aspiration cytodiagnosis and review of the literature. Cytopathology. 2017;28(5):364–70. 112. Lim CY, Ong KO. Imaging of musculoskeletal lymphoma. Cancer Imaging. 2013;13(4):448–57. 113. Rich BS, McEvoy MP, Honeyman JN, La Quaglia MP. Hodgkin lymphoma presenting with chest wall involvement: a case series. J Pediatr Surg. 2011;46(9):1835–7. 114. Press GA, Glazer HS, Wasserman TH, Aronberg DJ, Lee JK, Sagel SS. Thoracic wall involvement by Hodgkin disease and non-­ Hodgkin lymphoma: CT evaluation. Radiology. 1985;157(1):195–8. 115. Watt AJ.  Chest wall lesions. Paediatr Respir Rev. 2002;3(4): 328–38. 116. Gorospe L, Chinea-Rodriguez A, Garcia-Cosio-Piqueras M, Calbacho-Robles M, Almeida-Arostegui NA. Hodgkin lymphoma presentation with extensive chest wall muscle involvement in an adult. Ann Thorac Surg. 2018;106(1):e37. 117. Ryu JK, Jin W, Kim GY. Sonographic appearances of small organizing hematomas and thrombi mimicking superficial soft tissue tumors. J Ultrasound Med. 2011;30(10):1431–6. 118. Hashefi M. Ultrasound in the diagnosis of noninflammatory musculoskeletal conditions. Semin Ultrasound CT MR. 2011;32(2):​ 74–90. 119. Taljanovic MS, Gimber LH, Klauser AS, Porrino JA, Chadaz TS, Omar IM.  Ultrasound in the evaluation of musculoskeletal soft-­ tissue masses. Semin Roentgenol. 2017;52(4):241–54. 120. Lee YK, Skalski MR, White EA, Tomasian A, Phan DD, Patel DB, et al. US and MR imaging of pectoralis major injuries. Radiographics. 2017;37(1):176–89. 121. Smith SE, Salanitri J, Lisle D. Ultrasound evaluation of soft tissue masses and fluid collections. Semin Musculoskelet Radiol. 2007;11(2):174–91. 122. Hryhorczuk AL, Restrepo R, Lee EY.  Pediatric musculoskeletal ultrasound: practical imaging approach. AJR Am J Roentgenol. 2016;206(5):W62–72.

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9

Diaphragm Wendy G. Kim, Helen H. R. Kim, Grace S. Phillips, and Edward Y. Lee

Abbreviations B Brightness BH Bochdalek hernia CDE Congenital diaphragmatic eventration CDH Congenital diaphragmatic hernia DP Diaphragmatic paralysis ECMO Extracorporeal membrane oxygen HH Hiatal hernia M Motion MH Morgagni hernia TDR Traumatic diaphragmatic rupture

Introduction The diaphragm is a skeletal muscle that separates the thoracic and abdominal cavities and is essential for the normal development of the thoracic and abdominal viscera. The diaphragm also performs critical functions in respiration and digestion. Congenital or acquired disorders of the diaphragm cause substantial morbidity and mortality in the pediatric population, and prompt diagnosis is essential. Ultrasound is best suited for evaluation of the pediatric diaphragm because W. G. Kim Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA H. H. R. Kim Department of Radiology, Seattle Children’s Hospital, University of Washington School of Medicine, Seattle, WA, USA G. S. Phillips Department of Radiology, Seattle Children’s Hospital, University of Washington, Seattle, WA, USA E. Y. Lee (*) Division of Thoracic Imaging, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA e-mail: [email protected]

it allows for dynamic imaging of anatomic and functional abnormalities. Ease of access and lack of ionizing radiation make ultrasound an appropriate first-line diagnostic modality, particularly in critically ill pediatric patients. This chapter provides an overview of the ultrasound evaluation of the diaphragm in the pediatric population, beginning with up-to-date ultrasound imaging techniques, diaphragmatic embryology, and normal anatomy. The remainder of the chapter focuses on the ultrasound findings and relevant clinical features of congenital and acquired diaphragmatic disorders in the pediatric population.

Technique Patient Positioning Ultrasound evaluation of the diaphragm is best performed with the patient in a supine position, which allows for greater diaphragmatic excursion and greater reproducibility. This is thought to be due to decreased gravitational impedance of abdominal visceral movement and decreased compensatory active breathing compared to the upright or sitting positions [1]. Sitting or lateral decubitus positions can sometimes be helpful to optimize the ultrasound window in pediatric patients with external support devices or dressings along the anterior chest wall.

Ultrasound Transducer Selection The optimal ultrasound transducer frequency should be tailored to both patient size and the specific clinical question. High-frequency (9–17  MHz) linear array transducers can provide optimal spatial resolution and are particularly useful in infants and small children. Low-frequency (2–6  MHz) convex or sector transducers allow greater depth of penetration and field of view and are useful for examination of older

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children and adolescents and also for the evaluation of diaphragmatic excursion [1, 2].

Imaging Approaches An oblique transverse subxiphoid approach allows for dynamic evaluation of symmetric diaphragmatic excursion. Sector transducers are typically better suited for this approach, permitting visualization of both medial hemidiaphragms in the ultrasound window. Evaluation of critically ill, ventilated pediatric patients should be coordinated with the respiratory therapist to assess diaphragmatic excursion both on and temporarily off ventilator support. Bilateral longitudinal transdiaphragmatic approaches are helpful for anatomic evaluation of each hemidiaphragm using either the liver, spleen, or stomach as an acoustic window. Conventional brightness (B)-mode ultrasound is typically used to qualitatively evaluate the diaphragm and peridiaphragmatic structures. Motion (M)-mode ultrasound can also

Septum transversum

be used for quantitative measurements of both the amplitude and direction of motion of diaphragmatic excursion. Normal excursion should be greater than 4 mm, and usually there is less than a 50% difference in excursion between the hemidiaphragms [3, 4]. Color Doppler imaging is useful for characterizing juxta-diaphragmatic masses or vascular structures.

Normal Development and Anatomy Normal Development The diaphragm forms between the 4th and 12th weeks of life from four main embryologic precursors. These include the transverse septum centrally, the bilateral pleuroperitoneal folds posterolaterally, the body wall musculature peripherally, and the esophageal mesoderm posteromedially (Fig. 9.1). A failure of either development or appropriate fusion of these structures can result in a congenital diaphragmatic hernia [5].

Septum transversum

Liver

DAY 27

Septum transversum

DAY 34

Septum transversum

T1

T1

Pleuroperitoneal membrane

L1 Pleuroperitoneal membrane

L1 DAY 43

Fig. 9.1  Development of the diaphragm. Diagram illustrating fetal development of the diaphragm occurring between the 4th and 12th weeks of gestation. The transverse septum originates anteriorly and

DAY 54

forms the central portion of the diaphragm. The pleuroperitoneal membranes form posterolaterally on either side, while the mesoderm develops into the body wall musculature and esophageal mesoderm

9 Diaphragm

273 Sternum

Central tendon of diaphragm

Vena cava passing through caval opening Esophagus passing through esophageal hiatus

Diaphragm

Aorta passing through aortic hiatus

12th (floating) ribs Left psoas major Vertebrae Left quadratus lumborum

Fig. 9.2 Anatomy of the diaphragm. Illustration of the diaphragm as viewed from below shows the attachments of the diaphragm to the chest wall and spine. The caval opening is located at approximately the T8

vertebral level, the esophagus traverses the esophageal hiatus at the T10 vertebral level, and the aorta passes through the aortic hiatus at the T12 vertebral level

Normal Anatomy The diaphragm is a thin, domed musculotendinous structure separating the abdominal and thoracic cavities. The fibrous central tendon constitutes the apex of the domed diaphragm, while the radially oriented muscular fibers extend laterally to the ribs at their costal attachments. The crural diaphragm is thicker and located posteromedially, surrounding the esophagus and aorta and attaching to the upper lumbar vertebrae. The right and left crura are joined by the median arcuate ligament. The medial and lateral arcuate ligaments attach the posterior diaphragm to the spine and 12th ribs, while the anterior and lateral attachments include the inferior sternum, xiphoid, lower six ribs, and costal cartilages (Fig. 9.2) [6]. The right and left hemidiaphragms are innervated by the right and left phrenic motor nerves (C3–C5) and vascularized by the phrenic, internal thoracic, and intercostal arteries. On ultrasound, the diaphragm appears as a thin hypoechoic muscular sheath between echogenic layers of peritoneum and pleura (Fig.  9.3). With low-frequency transducers, the diaphragm frequently appears as a single echogenic layer

Fig. 9.3  Normal appearance of the diaphragm in a 14-day-­old female. Transverse grayscale ultrasound image at a subxiphoid midline position demonstrates a symmetric appearance of the posterior hemidiaphragms (arrows) which are depicted as echogenic curved lines. The hypoechoic diaphragmatic crura (arrowheads) can also be seen at midline draping over the aorta (asterisk)

between the lung and abdominal viscera due to ultrasound reverberation artifact between the lung and diaphragm [7]. During inspiration, the diaphragm moves inferiorly, and the muscle fibers appear to thicken [1].

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Congenital Diaphragmatic Anomalies Diaphragmatic Hernia Congenital diaphragmatic hernia (CDH) is a focal defect in the diaphragm that can result in displacement of the abdominal contents into the thoracic cavity. CDH occurs in approximately 0.02–0.06% of births and continues to have substantial associated morbidity and mortality despite recent medical advances [8, 9]. Clinical prognosis is usually determined by the degree of pulmonary hypoplasia and functional derangement of the lungs and associated structures. Additional anomalies are present in up to 50% of patients with CDH, including neural tube defects, cleft palate, congenital heart disease, esophageal atresia, and genetic syndromes, and often portend a worse prognosis [10]. CDH is classified by the location of the diaphragmatic defect, with a Bochdalek hernia in the posterolateral diaphragm, a Morgagni hernia in the anteromedial parasternal diaphragm, and a hiatal hernia occurring centrally through the esophageal hiatus (Fig. 9.4, Table 9.1).

Bochdalek Hernia Bochdalek hernia (BH) is the most common type of CDH (approximately 90% of cases) and usually affects the left hemidiaphragm [9, 10]. It is thought to occur secondary to a developmental malformation of the pleuroperitoneal membrane or failure of attachment to the thoracic wall [11]. Diagnosis is usually made during routine prenatal imaging or in the neonatal period due to pulmonary hypoplasia and symptoms of respiratory distress. BH can usually be detected by routine prenatal ultrasound as early as 18 weeks of gestation [12]. On ultrasound, a left-sided CDH typically manifests as displacement of the stomach, bowel, and/or left hepatic lobe into the left chest with contralateral mediastinal shift (Fig.  9.5). Right-sided CDH presents with displacement of the hepatic dome, gallbladder, omentum, and/or bowel into the right chest with leftward mediastinal shift. Color Doppler evaluation may demonstrate an abnormal course of the umbilical and hepatic veins [10]. Fetal lung volume can also be measured using three-dimensional ultrasound to determine prognosis. Measured lung volumes less than 15–25% of expected volume, along with herniation of the liver

Morgagni hernia Other anterior hernias Hiatal hernia

Bochdalek hernia

a

Morgagni hernia and other anterior hernias

Hiatal (sliding and paraesophageal) hernia c

b

Fig. 9.4  Diagram demonstrating different types of diaphragmatic hernia. (a) Bochdalek hernia is typically large and occurs posteriorly. (b) Morgagni hernia occurs anteriorly. (c) Hiatal hernia occurs in the region of the esophageal hiatus Table 9.1  Types of diaphragmatic hernia and distinguishing factors Location Side Developmental etiology

Bochdalek hernia Posterior Left more common than right Pleuroperitoneal membrane malformation or failure to attach to the thoracic wall

Morgagni hernia Anterior Right more common than left Failed fusion of the septum transversum and the anterior thoracic wall

Hiatal hernia Esophageal hiatus Midline Enlargement of the hiatus secondary to delayed descent of the stomach

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a

b

L S

S

Fig. 9.5  Bochdalek hernia in a 19-week gestational age male fetus. (a) Transverse grayscale ultrasound image demonstrates a large left diaphragmatic hernia with intrathoracic location of the stomach (S), spleen (asterisk), and multiple loops of bowel (arrow) with rightward displace-

ment of the heart (arrowhead). (b) Sagittal oblique grayscale ultrasound image shows the liver (L) which remains intra-abdominal in  location, with the stomach (S), bowel (arrow), and spleen (asterisk) displaced into the thorax

into the chest, associated cardiac malformations, and maternal polyhydramnios, can signify a worse prognosis [10, 11]. Postnatal ultrasound is usually performed in conjunction with radiography and is particularly useful in identifying herniation of solid organs (Fig.  9.6). Recent studies have demonstrated the utility of postnatal ultrasound evaluation to guide surgical management by quantifying the size of the defect, determining the presence or absence of a diaphragmatic rim, and differentiating the defect from diaphragmatic eventration [7, 13, 14]. Management of BH involves a multidisciplinary approach. Primary medical treatment includes low-pressure, high-­ frequency mechanical ventilation to prevent lung injury and pharmacologic treatment of pulmonary hypertension. Early initiation of extracorporeal membrane oxygen (ECMO) should be considered in infants who fail to improve with conventional management [15]. Surgical repair is usually delayed until the patient is physiologically stabilized [16]. A subcostal approach laparotomy is typically used to place the herniated abdominal viscera back into the abdominal cavity. Small defects can be repaired with primary apposition, while larger defects are repaired by patch or graft closure. Thoracoscopic and laparoscopic surgical approaches have recently been gaining favor, with good clinical outcomes [17].

septum transversum and the anterolateral thoracic wall [6]. Affected patients can be asymptomatic or present later in life with mild respiratory distress, recurrent pneumonia, or gastrointestinal symptoms [8]. Prenatal and postnatal ultrasound findings of MH are similar to those of BH (Fig. 9.7). The herniated portion of the liver may demonstrate abnormal echogenicity due to vascular engorgement [10]. On ultrasound, demonstrating d­iscontinuity and folding of the free edge of the diaphragm with a narrow angle waist has been shown to be a specific finding for right-sided hernias [7]. Surgical repair is performed due to the risk of bowel incarceration and strangulation [10]. Laparoscopic and open repair have demonstrated similar favorable outcomes, while the use of patch repair has more recently been shown to reduce the rate of recurrence [18].

Morgagni Hernia Morgagni hernia (MH) occurs most commonly on the right side and is thought to result from a failure of fusion of the

Hiatal Hernia Hiatal hernia (HH) is usually acquired due to weakening or atrophy of the diaphragmatic crura. However, congenital HH is thought to occur as a result of delayed descent of the stomach during development, which causes enlargement of the esophageal hiatus [10]. HHs are further subdivided into sliding hernias, where both the gastroesophageal junction and portions of the stomach move into the chest; paraesophageal hernias, where only portions of the stomach are displaced into the chest; and congenital short esophagus, where the stomach is fixed inside the chest [10]. Affected children typically present with gastroesophageal reflux,

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S

c

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Fig. 9.6  Bochdalek hernia in a 1-month-old male with trisomy 18, congestive heart failure and multiple congenital anomalies. (a) Frontal chest radiograph demonstrates cardiomegaly, pulmonary edema, and a rounded opacity (arrow) at the left lung base. (b) Sagittal grayscale ultra-

a

sound image demonstrates herniation (arrow) of the spleen (S) into the left chest. Sagittal grayscale ultrasound images demonstrate (c) a normal thin echogenic diaphragm (arrowhead) on the right and (d) a discontinuous diaphragm (arrow) on the left

b

H

Fig. 9.7  Morgagni hernia in a 4-month-old male with trisomy 21. Sagittal (a) and transverse (b) grayscale ultrasound images of the liver demonstrate focal herniation (arrows) of a portion of the right hepatic

lobe into the anterior chest. The liver directly abuts the heart (H). Note the intact portions (arrowheads) of the diaphragm posteriorly and laterally

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recurrent respiratory tract infections, emesis, and failure to thrive [19]. Prenatal diagnosis of HH can be made with ultrasound, which demonstrates an anechoic or hypoechoic mass or tubular structure in the posterior mediastinum that is continuous with the stomach [20]. An intact diaphragm should also be confirmed. Peristalsis of the herniated stomach can be identified on real-time ultrasound imaging [21]. Postnatal imaging diagnosis usually involves radiography or a fluoroscopic contrast study of the upper gastrointestinal tract. Ultrasound can be useful to exclude other causes of gastroesophageal reflux in young children. Determination of esophageal length, diameter, wall thickness, and the angle at the gastroesophageal junction can also provide diagnostic indicators of reflux or the presence of an HH (Fig. 9.8) [22, 23]. Symptomatic HH is treated surgically, which involves reducing the herniated contents, excising the hernia sac, closing the crural defect, and performing an antireflux procedure such as a Thal or Nissen fundoplication. Laparoscopic technique has been shown to have favorable outcomes and reduced recurrence rates [19, 24].

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Diaphragmatic Eventration Congenital diaphragmatic eventration (CDE) refers to the abnormal elevation or contour of an otherwise intact diaphragm, which is thought to occur in the setting of congenitally thinned diaphragmatic musculature [6]. Partial eventration occurs more commonly anteromedially on the right side and usually encompasses a portion of the liver [25]. Complete eventration occurs more commonly on the left side, with a slight male predominance [26]. CDE has been associated with other anomalies, including ipsilateral lung hypoplasia, congenital heart disease, and pectus excavatum [27]. Focal weakness of the diaphragm can also be acquired in the setting of trauma, infection, ischemia, or neuromuscular dysfunction and can be distinguished pathologically from CDE by the presence of a normal number of muscle fibers [25, 28]. Although the majority of patients with CDE are asymptomatic, clinical manifestations can vary widely, with some pediatric patients developing severe life-­threatening respiratory distress. Affected children most commonly present with tachypnea, vomiting, recurrent respiratory tract infections, and cough [27]. Ultrasound evaluation of focal CDE demonstrates an intact, echogenic diaphragm covering a portion of the elevated abdominal viscera (Fig. 9.9). The appearance of a fixed, broadangled waist during respiratory excursion at the site of eventration has been shown to be specific for the diagnosis of CDE [7]. The imaging appearance of complete CDE is difficult to distinguish from diaphragmatic paralysis, as both usually demonstrate asymmetric diaphragmatic excursion.

L

Fig. 9.8  Hiatal hernia in a 6-month-old female with vomiting. Sagittal grayscale ultrasound image of the diaphragmatic hiatus demonstrates a portion of the gas-filled stomach (asterisk) extending superiorly into the thorax through a widened hiatus (between arrows). The stomach was seen to slide dynamically through the hiatus on real-time imaging

Fig. 9.9  Diaphragmatic eventration in a 6-month-old female. Sagittal grayscale ultrasound image shows an abnormal contour (arrow) of the left medial hemidiaphragm containing a portion of the left hepatic lobe (L). In contrast to a true hernia, the diaphragm is intact and demonstrated normal excursion on real-time imaging

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Symptomatic CDE is typically treated with diaphragmatic plication, with more recent literature demonstrating the efficacy and improved outcomes of minimally invasive thoracoscopic approaches [29, 30].

Acquired Diaphragmatic Disorders Diaphragmatic Dysfunction Diaphragmatic paralysis (DP) or weakness can be a rare cause of respiratory distress in the pediatric population, with relatively more clinically significant sequelae when compared to adults. Infants and children have increased compliance of the chest wall and weaker accessory respiratory muscles, which decreases their compensatory efforts, even for unilateral dysfunction. This can lead to lung atelectasis, pneumonia, or difficulty weaning off mechanical ventilation [11]. Phrenic nerve injury due to birth trauma and cardiothoracic surgery is the most common cause of DP in infants under 1  year of age [31]. Phrenic nerve paralysis can also result from infection, inflammation, metabolic neuropathies, central nervous system pathology, or extrinsic compression from vascular abnormalities or masses [28]. Myopathies and neuromuscular disorders may also cause diaphragmatic weakness. a

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Dysfunction is usually unilateral, although bilateral dysfunction can also occur and results in more clinically evident respiratory failure [5]. Symptoms of DP include respiratory distress, paradoxical breathing, and increased work of breathing. Affected infants may also present with feeding difficulty and vomiting [31]. Imaging diagnosis of DP involves real-time evaluation with both B-mode and M-mode ultrasound. A subxiphoid approach typically demonstrates asymmetric excursion of the hemidiaphragms on B-mode ultrasound, while midaxillary views of each hemidiaphragm can allow quantification of excursion on M-mode ultrasound (Fig. 9.10). A diaphragmatic excursion less than 4 mm and a greater than 50% difference in excursion between the hemidiaphragms are indicative of dysfunction [3, 4]. The use of ultrasound for serial monitoring of diaphragmatic function in mechanically ventilated pediatric patients is being increasingly used to guide management of critically ill children [32, 33]. Management of DP depends on the severity of the clinical symptoms and whether or not phrenic nerve injury is thought to be reversible. Ventilatory support is required in pediatric patients presenting with hypoxia or failure to thrive. It can involve endotracheal ventilation or less invasive continuous or bi-­level positive airway pressure ventilation [31]. Symptomatic DP due to irreversible phrenic nerve injury is typically treated surgically with diaphragmatic plication, either via thoracotb

Fig. 9.10  Diaphragmatic dysfunction in a 15-month-old male with congenital cardiac disease and difficulty weaning off ventilation after surgery. Sagittal M-mode ultrasound images of the right (a) and left (b) hemidiaphragms demonstrate asymmetrically diminished excursion (arrowheads) on the right

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omy or minimally invasive thoracoscopic or laparoscopic techniques. Children with intact phrenic nerve function may benefit from an implanted phrenic nerve stimulator device [5].

Diaphragmatic Inversion Inversion of the diaphragm can occur in the setting of a large pleural or pericardial effusion, tension pneumothorax, or thoracic mass. It can occur in any age group but should be recognized as a cause of respiratory distress in the pediatric population. The right hemidiaphragm is less commonly affected than the left due to the presence of the liver, although bilateral inversion has also been reported [34]. Inversion is difficult to identify on radiographs alone, as the diaphragm is usually obscured by the primary cause of inversion. Ultrasound evaluation can diagnose both inversion of the diaphragm and the underlying cause (Fig.  9.11). Diaphragmatic excursion can be diminished, exaggerated, or

L K

paradoxical [25, 34, 35]. Inversion may affect the entire hemidiaphragm or only a small portion [25]. Management of diaphragmatic inversion typically involves treatment of the underlying cause. Pleural or pericardial effusions are most often treated with thoracentesis.

Primary Diaphragmatic Masses Benign Masses There are few documented reports of benign diaphragmatic masses that occur in the pediatric population. Reported lesions include cyst, lymphatic malformation, hemangioma, and lipoma (Table 9.2). Benign lesions can be asymptomatic and are often found incidentally. While benign cystic masses such as mesothelial cyst and bronchogenic cyst are the most common primary diaphragmatic neoplasms in adults, they are rare in children [36, 37]. A mesothelial cyst is typically located along the right posterolateral hemidiaphragm near the costophrenic angle, while a bronchogenic cyst is typically located at the diaphragmatic crus (Fig.  9.12). Both types of cyst are thin walled and anechoic on ultrasound, although a bronchogenic cyst may sometimes appear echogenic due to proteinaceous or hemorrhagic contents [38, 39]. A lymphatic malformation may appear as a multicystic mass that encases but does not compress the adjacent vasculature and may be associated with a chylothorax [40, 41]. A hemangioma frequently displays enlarged vascular channels Table 9.2  Diaphragmatic masses

Fig. 9.11  Diaphragmatic inversion in a 1-month-old female with history of meconium aspiration receiving extracorporeal membrane oxygenation (ECMO). Longitudinal grayscale ultrasound image shows a large right hemothorax (asterisk) causing diaphragmatic inversion (arrow). The right kidney (K) and liver (L) are seen below the inverted diaphragm

a

Fig. 9.12 Mesothelial cyst in a 6-year-old male with an incidentally identified cystic lesion of the left hemidiaphragm. Transverse (a) and sagittal (b) grayscale ultrasound images of the left hemidiaphragm demon-

Benign lesions Mesothelial cyst Bronchogenic cyst Lymphatic malformation Hemangioma Lipoma

Malignant lesions Rhabdomyosarcoma Undifferentiated sarcoma Yolk sac tumor Extra-osseous Ewing sarcoma

b

strate a well-defined hypoechoic and avascular cystic structure (arrows) adjacent to the spleen that moved with the diaphragm on real-­ time imaging

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on color Doppler ultrasound and can also be associated with a pleural effusion [42, 43]. Lipoma has a slight predilection for the left hemidiaphragm and can be sessile or hourglass in morphology [44]. Ultrasound delineation of an intact diaphragm is helpful in differentiating a lipoma from a fat-containing diaphragmatic hernia. Management of benign lesions depends on symptomatology and malignant potential. Most masses are typically surgically resected, both to establish a diagnosis and to alleviate symptoms. Mesothelial cysts can sometimes spontaneously regress, and some researchers suggest serial imaging surveillance [38]. Mesothelial cysts and larger unresectable lymphatic malformations have also been successfully treated with sclerotherapy [40, 45].

Malignant Neoplasms Primary diaphragmatic neoplasms in the pediatric population are exceedingly rare, and the majority are malignant (Table 9.2) [36]. There is no particular gender predilection, and lesions occur with equal frequency in the right and left hemidiaphragms [36]. The most common primary tumor of the diaphragm in children is rhabdomyosarcoma, an aggressive neoplasm of mesenchymal origin. Other documented malignant neoplasms include undifferentiated sarcoma, yolk sac tumor, and extra-osseous Ewing sarcoma (Fig. 9.13). Sarcomas tend to occur in slightly older children, with an average age of 12  years, while yolk sac tumors have been reported exclusively in children under the age of 2 years [46, 47]. Clinical presentation is dependent on age at diagnosis, along with size and histology of the mass. Affected pediatric

Fig. 9.13  Yolk sac tumor in a 4-year-old male with respiratory distress. Transverse grayscale ultrasound image shows a heterogeneous solid mass (arrows) adjacent to the esophagus (asterisk) and inseparable from the left diaphragm

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patients most commonly present with symptoms of chest pain, shortness of breath, and cough [36]. Left-sided diaphragmatic lesions may cause gastrointestinal symptoms due to gastric compression [48]. Diaphragmatic masses present a diagnostic challenge due both to their rarity and difficulty in delineating their site of origin. Because of their aggressive nature, sarcomas and yolk sac tumors may be large at the time of diagnosis, appearing as heterogeneous, vascular lesions on ultrasound. Larger tumors are often misdiagnosed as originating from adjacent organs such as the liver, lung, spleen, stomach, and pericardium [36]. Their diaphragmatic origin is sometimes better demonstrated after tumor shrinkage with chemotherapy. Helpful imaging clues in determining diaphragmatic origin include the pattern of organ displacement, presence of an obtuse angle between the mass and the diaphragm, and a “claw” sign demonstrating portions of the diaphragm extending around the mass [49]. Differential considerations include common juxta-diaphragmatic masses such as hepatic, peritoneal, or pleural-based neoplasms. It is important to note that the diaphragm may be involved in direct extension of adjacent tumors, particularly those arising in the retroperitoneum [50]. Metastatic involvement of the diaphragm has been documented in cases of thymoma and ovarian cancer which are both exceedingly rare in children [37]. Treatment of malignant diaphragmatic tumors is determined by histopathology and usually involves some combination of chemotherapy, radiation, and surgical resection. Larger tumors may require partial resection of the diaphragm, with muscular flap or graft reconstruction [36].

Traumatic Disorders Traumatic diaphragmatic rupture (TDR) is uncommon in children and is typically associated with high-impact, multiorgan trauma. TDR occurs in approximately 3% of children with blunt abdominal trauma [51]. Males are more commonly affected than females, with an average age of 7  years [51]. TDR more commonly occurs on the left side, although traumatic defects tend to be larger on the right side. While adults presenting with TDR usually present with abdominal symptoms, the majority of pediatric patients present with ­respiratory distress and decreased breath sounds. TDR is frequently associated with injury to the liver, lung, pelvis, and/or kidney, although isolated TDR has also been reported [51]. Ultrasound can demonstrate unilateral thickening with focal discontinuity of the diaphragm. Fluid may be seen above and below the affected diaphragm with an appearance of a floating free edge of the ruptured diaphragm [52–54]. In cases of associated visceral herniation, real-time imaging may show intrathoracic location of the liver and/or peristalsing bowel

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18. Tan Y-W, Banerjee D, Cross KM, De Coppi P; GOSH team, Blackburn SC, Rees CM, Giuliani S, Curry JI, Eaton S. Morgagni hernia repair in children over two decades: institutional experience, systematic review, and meta-analysis of 296 patients. J Pediatr Surg. 2018;53(10):1883–9. 19. Garvey EM, Ostlie DJ. Hiatal and paraesophageal hernia repair in pediatric patients. Semin Pediatr Surg. 2017;26(2):61–6. 20. Ruano R, Benachi A, Aubry MC, Bernard JP, Hameury F, NihoulFekete C, et al. Prenatal sonographic diagnosis of congenital hiatal hernia. Prenat Diagn. 2004;24(1):26–30. 21. Ogunyemi D. Serial sonographic findings in a fetus with congenital hiatal hernia. Ultrasound Obstetr Gynecol. 2001;17(4):350–3. 22. Savino A, Cecamore C, Matronola MF, Verrotti A, Mohn A, Chiarelli F, et al. US in the diagnosis of gastroesophageal reflux in References children. Pediatr Radiol. 2012;42(5):515–24. 23. Westra SJ, Wolf BH, Staalman CR. Ultrasound diagnosis of gastroesophageal reflux and hiatal hernia in infants and young children. J 1. Sarwal A, Walker FO, Cartwright MS. Neuromuscular ultrasound Clin Ultrasound. 1990;18(6):477–85. for evaluation of the diaphragm. Muscle Nerve. 2013;47(3):319–29. 2. Mong A, Epelman M, Darge K. Ultrasound of the pediatric chest. 24. Petrosyan M, Shah AA, Chahine AA, Guzzetta PC, Sandler AD, Kane TD. Congenital paraesophageal hernia: contemporary results Pediatr Radiol. 2012;42(11):1287–97. and outcomes of laparoscopic approach to repair in symptomatic 3. Urvoas E, Pariente D, Fausser C, Lipsich J, Taleb R, Devictor D. infants and children. J Pediatr Surg. 2019;54(7):1346–50. Diaphragmatic paralysis in children: diagnosis by TM-mode ultra 25. Yeh HC, Halton KP, Gray CE. Anatomic variations and abnormalities sound. Pediatr Radiol. 1994;24(8):564–8. in the diaphragm seen with US. Radiographics. 1990;10(6):​1019–30. 4. 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loops [55]. Indirect signs of TDR include non-­visualization of the left diaphragm or spleen due to herniation of the stomach and associated loss of a usual ultrasound window [56]. Surgical management is determined by the location of injury and most often requires laparotomy. Thoracotomy or transdiaphragmatic surgical approaches are also reported. Traumatic diaphragmatic defects are usually repaired with primary apposition and suturing [57].

282 39. Liou CH, Hsu HH, Hsueh CJ, Juan CJ, Chen CY. Imaging findings of intradiaphragmatic bronchogenic cyst: a case report. J Formos Med Assoc. 2001;100(10):712–4. 40. Ming Y-C, Wong K-S, Wang C-J, Lai J-Y.  Successful management of a bilateral diaphragmatic lymphangioma. Pediatr Surg Int. 2007;​ 23(6):591–3. 41. Seo T, Ito T, Ishiguro Y, Ando H, Iio K, Umeda T, et al. Lymphangioma of the right diaphragm. Pediatr Surg Int. 1992;7:384–6. 42. Yao Q, Hu X, Huang G, Pa M. A case of diaphragmatic infantile hemangioma. J Perinatol. 2013;33(7):576–7. 43. Wu L, Wang JM, Qiao ZW, Yan YL, Wang LS. Successful embolization and long-term follow-up of a rare neonatal diaphragmatic hemangioma. SAGE Open Med Case Rep. 2015;3:2050313X15615471. 44. Margiotta G, Carlini L, Carnevali E, Lancia M, Gabbrielli M, Bacci M. Giant diaphragmatic lipoma: two autopsy case reports and review of the literature. J Forensic Sci. 2015;60(6):1640–3. 45. Akinci D, Akhan O, Ozmen M, Ozkan OS, Karcaaltincaba M. Diaphragmatic mesothelial cysts in children: radiologic findings and percutaneous ethanol sclerotherapy. AJR Am J Roentgenol. 2005; 185(4):873–7. 46. Choi Y-S, Liu H-C, Yeh T-C, Hou JY, Sheu JC, Chen BF, et  al. Primary diaphragmatic yolk sac tumor and review of the literature. J Pediatr Hematol Oncol. 2011;33(2):e77–9. 47. Raney RB, Anderson JR, Andrassy RJ, Crist WM, Donaldson SS, Maurer HM; Intergroup Rhabdomyosarcoma Study Group. Soft-tissue sarcomas of the diaphragm: a report from the intergroup rhabdomyosarcoma study group from 1972 to 1997. J Pediatr Hematol Oncol. 2000;22(6):510–4.

W. G. Kim et al. 48. Melis M, Rosen G, Hajdu CH, Pachter HL, Raccuia JS. Primary rhabdomyosarcoma of the diaphragm: case report and review of the literature. J Gastrointest Surg. 2013;17(4):799–804. 49. Traubici J, Daneman A, Hayes-Jordan A, Fecteau A. Primary germ cell tumor of the diaphragm. J Pediatr Surg. 2004;39(10):1578–80. 50. Restrepo CS, Eraso A, Ocazionez D, Lemos J, Martinez S, Lemos DF. The diaphragmatic crura and retrocrural space: normal imaging appearance, variants, and pathologic conditions. Radiographics. 2008; 28(5):1289–305. 51. Marzona F, Parri N, Nocerino A, Giacalone M, Valentini E, Masi S, et al. Traumatic diaphragmatic rupture in pediatric age: review of the literature. Eur J Trauma Emerg Surg. 2019;45(1):49–58. 52. Koplewitz BZ, Ramos C, Manson DE, Babyn PS, Ein SH. Traumatic diaphragmatic injuries in infants and children: imaging findings. Pediatr Radiol. 2000;30(7):471–9. 53. Kirkpatrick AW, Ball CG, Nicolaou S, Ledgerwood A, Lucas CE. Ultrasound detection of right-sided diaphragmatic injury; the “liver sliding” sign. Am J Emerg Med. 2006;24(2):251–2. 54. Somers JM, Gleeson FV, Flower CD. Rupture of the right hemidiaphragm following blunt trauma: the use of ultrasound in diagnosis. Clin Radiol. 1990;42(2):97–101. 55. Kim HH, Shin YR, Kim KJ, Hwang SS, Ha HK, Byun JY, et  al. Blunt traumatic rupture of the diaphragm: sonographic diagnosis. J Ultrasound Med. 1997;16(9):593–8. 56. Gangahar R, Doshi D.  FAST scan in the diagnosis of acute diaphragmatic rupture. Am J Emerg Med. 2010;28(3):387.e1–3. 57. Furák J, Athanassiadi K. Diaphragm and transdiaphragmatic injuries. J Thorac Dis. 2019;11(Suppl 2):S152–7.

The Gastrointestinal Tract

10

Marthe M. Munden and Harriet J. Paltiel

Abbreviations AFP Alpha-fetoprotein ALARA As Low As Reasonably Achievable BRBNS Blue rubber bleb nevus syndrome CD Crohn disease CeCS Contrast-enhanced colosonography CEUS Contrast-enhanced ultrasound CF Cystic fibrosis CFTR Cystic fibrosis transmembrane regulator CMV Cytomegalovirus CT Computed tomography DIOS Distal intestinal obstruction syndrome DSRCT Desmoplastic small round cell tumor ECMO Extracorporeal membrane oxygenation ESPGHAN European Society for Pediatric Gastroen­ terology, Hepatology, and Nutrition FDG Fluorodeoxyglucose GER Gastroesophageal reflux GI Gastrointestinal GIST Gastrointestinal stromal tumor GVHD Graft-versus-host disease HCG Human chorionic gonadotropin HLA Human leukocyte antigen HPS Hypertrophic pyloric stenosis HSP Henoch–Schönlein purpura HUS Hemolytic–uremic syndrome IBD Inflammatory bowel disease

M. M. Munden (*) Department of Radiology, Shawn Jenkins Children’s Hospital, Medical University of South Carolina, Charleston, SC, USA e-mail: [email protected] H. J. Paltiel Division of Ultrasound, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA

Ig Immunoglobulin ISSVA International Society for the Study of Vascular Anomalies LES Lower esophageal sphincter MII Multiple intraluminal impedance MR Magnetic resonance NASPGHAN North American Society for Pediatric Gastro­ enterology, Hepatology, and Nutrition NEC Necrotizing enterocolitis NHL Non-Hodgkin lymphoma PEG Polyethylene glycol PET Positron emission tomography SBI Small bowel intussusception SMA Superior mesenteric artery SMV Superior mesenteric vein UC Ulcerative colitis UGI Upper gastrointestinal

Introduction Ultrasound is an important imaging modality for evaluation of the gastrointestinal tract in children. Ultrasound is often the first-line imaging modality in children presenting to the Emergency Department with vomiting, abdominal pain, and lethargy not explained by initial plain abdominal radiographs. There is no need for preparation in the emergent setting for ultrasound imaging and the lack of imaging with radiation is in accordance with the As Low As Reasonably Achievable (ALARA) principle. Ultrasound techniques for imaging of the pediatric GI tract are reviewed, followed by normal development and anatomy. The definition, incidence, and typical clinical presentation of entities involving the GI tract from the esophagus to the anorectal region are discussed, including infectious, inflammatory, congenital, neoplastic, as well as anatomic variants that can predispose to volvulus and obstruction. A brief overview of management is also provided.

© Springer Nature Switzerland AG 2021 H. J. Paltiel, E. Y. Lee (eds.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-56802-3_10

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Esophagus Technique Patient Positioning Cooperation varies with age, but in most pediatric patients, the cervical esophagus is easily evaluated with ultrasound by placing the patient supine, using a small pillow or towel roll to extend the neck for optimal visualization. The upper thoracic esophagus can be difficult to assess due to acoustic reflectors from the lungs. However, the heart can be used as an acoustic window to visualize the lower thoracic esophagus [1]. The gastroesophageal junction can easily be studied in the supine infant. Ultrasound Transducer Selection The highest resolution linear array transducers, typically in the range of 15–18 MHz, are used for imaging with settings optimized for the bowel wall. A small footprint transducer is ideal in the study of the cervical esophagus in infants and younger children. Imaging Approaches No special preparation is needed although fasting for at least 4 hours is recommended in the non-emergent setting for optimal imaging to reduce artifact from food content in the stomach and small bowel. Transverse images of the cer-

vical esophagus can be obtained centering just to the left of midline with the esophagus located posterior to the left lobe of the thyroid gland. Sagittal imaging of the cervical esophagus is relatively easily performed using a left lateral approach to study the majority of the cervical esophagus. A right lateral approach can be used to image the lower cervical esophagus [1]. Filling the stomach with clear liquid and then placing the transducer in a sagittal plane in the midline along the aortic hiatus allows for assessment of the lower thoracic esophagus and gastroesophageal junction. This approach can be used to assess for gastroesophageal reflux, hiatal hernia, as well as intrathoracic positioning of the stomach.

Normal Development and Anatomy Normal Development The gastrointestinal tract arises from the endoderm of the trilaminar embryo in the third week of life and extends from the buccopharyngeal membrane to the cloacal membrane. The GI tract and its associated organs will subsequently receive contributions from all three germ cell layers. In the fourth week of life three distinct regions, the foregut, midgut, and hindgut, extend the length of the embryo and will develop into the different components of the GI tract (Fig. 10.1).

Pharynx

Aorta Stomodeum Heart Septum transversum

Esophageal region Gastric and duodenal regions Celiac artery

Yolk stalk and vitelline artery Allantois Proctodeum Cloacal membrane Cloaca

Primordium of liver Superior mesenteric artery to midgut Inferior mesenteric artery Hindgut

Fig. 10.1  Diagram of a 4-week-old embryo showing early development of the gastrointestinal tract and its arterial blood supply

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Normal Anatomy The esophagus is a fibromuscular tube which consists of cervical, thoracic, and abdominal components (Fig. 10.2). The esophagus arises from the embryonic endoderm with the early digestive tract, dividing into a foregut, midgut, and hindgut. The

proximal foregut separates into a ventral respiratory and dorsal gastrointestinal tube. The ventral tracheobronchial diverticulum eventually separates from the dorsal foregut to become the respiratory tract. A disturbance in this process of separation underlies the development of tracheoesophageal malformations. Bronchogenic cysts and esophageal duplication cysts also arise from aberrant budding of the tracheobronchial tree. During the fourth month of gestation, the embryonic ciliated epithelium is replaced by stratified squamous epithelium. The circular muscle and ganglion cells form during week 6, while blood vessels enter the submucosa during week 7. The striated muscle of the upper esophagus and upper esophageal sphincter is derived from branchial arches 4, 5, and 6 and is innervated by the vagus nerve. The smooth muscle of the lower esophagus and lower sphincter are derived from mesenchyme of somites surrounding the foregut. The esophagus also receives parasympathetic and sympathetic innervation which regulates glandular secretion, striated and smooth muscle activity, and blood supply [2]. The cephalad portion of the cervical esophagus begins inferior to the cricoid cartilage at the lower border of the pharynx at the sixth cervical vertebra and ends at the upper mediastinum, located between the trachea anteriorly and the vertebra posteriorly (Fig. 10.3). The thoracic esophagus crosses the diaphragm at the esophageal hiatus around the tenth thoracic vertebral level and the short portion of the abdominal esophagus joins the gastric cardia (Fig. 10.4). The thoracic esophagus courses to the right of the cephalad aorta and posterior to the left atrium more caudally. There is an upper and lower esophageal functional sphincter. The cricopharyngeus forms the primary muscle of the upper sphincter, triggered by the swallowing reflex. The lower esophageal sphincter (LES), like the lower esophagus, is composed of smooth muscle which thickens at the LES, anchored by the right diaphragmatic crus. The lower sphincter provides an antireflux mechanism at the diaphragmatic hiatus [3].

Pharynx Cricoid cartilage Trachea

Left flexure of esophagus

Arch of aorta Left bronchus Right flexure of esophagus

Descending aorta Intra-abdominal esophagus

Fundus of stomach

Esophageal hiatus

Cardia

Pylorus

Greater curvature

Descending duodenum

Lesser curvature

Fig. 10.2  Diagram of the normal esophagus and stomach

a

b

T

Fig. 10.3  Normal ultrasound appearance of cervical esophagus in a 5-year-old child. (a) Sagittal grayscale ultrasound image shows normal alternating layers (arrows) of the esophageal wall. Incidentally noted is

a cervical extension (arrowhead) of the thymus gland. (b) Transverse grayscale ultrasound image shows the normal esophagus (arrow) posterior to the left thyroid lobe (T)

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Fig. 10.4  Normal gastroesophageal junction in a 3-month-old infant. Sagittal grayscale ultrasound image of the gastroesophageal junction with normal length of abdominal esophagus. Swallowed echogenic air bubbles (arrow) are identified in the lower thoracic esophagus

The esophagus narrows at the cricoid cartilage; at the level of the aortic arch where it is compressed by the left main bronchus; and at the esophageal hiatus; all common sites at which food or foreign bodies may become lodged within the esophagus. The abdominal esophagus is a short portion extending from the esophageal hiatus of the diaphragm to the cardia of the stomach [4]. The esophageal wall is comprised of an inner echogenic mucosal layer, surrounded sequentially by a thin hypoechoic muscular layer, an echogenic submucosal layer, and a hypoechoic layer of circular and longitudinal muscle. The outer, adventitial layer consists of echogenic fat.

Gastroesophageal Reflux Gastroesophageal reflux (GER) is defined as the retrograde passage of gastric contents into the esophagus. Gatrointestinal reflux disease (GERD) is defined as reflux with associated complications such as aversion to feeding, esophageal strictures, or failure to thrive. GER is considered a normal physiologic entity that occurs several times a day in normal infants, associated with transient relaxation of the lower esophageal sphincter. Up to 50% of normal infants spit up daily during the first 6 months of life [5]. GERD is associated with symptoms that include poor weight gain, refusal to eat, vomiting with irritability, choking, wheezing, and failure to thrive. The incidence of GERD is lower in breast-fed infants, peaks around 4 months of age, and

M. M. Munden and H. J. Paltiel

declines by 12 months of age. When present in older children, symptoms include heartburn, chest pain, and dysphagia [5, 6]. Reflux of gastric contents can be easily seen during an ultrasound examination. Infants with GER have a shorter intraabdominal esophagus compared to those without reflux [1]. Contrast-enhanced color Doppler ultrasound has been used to diagnose GER in children [6]. However, the retrograde motion of gastric content is readily detected on grayscale ultrasound (Fig. 10.5) simply by filling of the stomach with milk or water [7–9]. A recent update by the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and the European Society for Pediatric Gas­ troenterology, Hepatology, and Nutrition (ESPGHAN) [10] reported a 95% sensitivity of color Doppler ultrasound in the detection of GER but only an 11% specificity when comparing ultrasound assessment with 24-hour pH testing. Although there is no evidence to support the use of ultrasound as a primary means of diagnosing GERD, it may be useful to assess for other causes of GER, such as hiatal hernia and pyloric stenosis [11]. Imagers should be aware of the “masslike” appearance of the gastroesophageal junction after surgical fundoplication wrap for treatment of GERD (Fig. 10.6), closely resembling the appearance associated with intussusception. The upper gastrointestinal tract (UGI) barium study is not the study of choice to assess for pathologic reflux but is useful in the evaluation of possible anatomic obstruction, and for the diagnosis of a web, stenosis, or malrotation that could predispose to GER. Continuous intraluminal esophageal pH monitoring is being used less often as a primary modality for diagnosis, while multiple intraluminal impedance (MII) is emerging as a better method for detection of GERD.  MII and pH electrodes are placed using a single catheter [11]. Upper endoscopy can be helpful in those who do not respond to routine management by directly visualizing the esophageal mucosa and permitting evaluation of the severity of injury and inflammation. GERD symptoms often respond to thickening of formula, cessation of overfeeding, and avoidance of supine positioning and tobacco smoke [12]. Various pharmacologic agents are available, including acid suppressants, histamine 2 receptor inhibitors, protein pump inhibitors, and prokinetic agents. Fundoplication surgery is performed when GER cannot be controlled medically [13].

Hiatal Hernia A hiatal hernia is defined as herniation of a portion of the stomach through the esophageal hiatus into the thorax, and is associated with a variety of diaphragmatic abnormalities, including enlargement of the esophageal hiatus, congenital defects, and post-traumatic damage. Most hiatal hernias in children are congenital in origin.

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a

b

Fig. 10.5  Gastroesophageal reflux in a 6-month-old infant. (a) Sagittal grayscale ultrasound image of the gastroesophageal junction shows reflux (arrow) of liquid gastric content into the lower esophagus.

(b) Upper gastrointestinal (UGI) series image reveals reflux of barium (arrow) into the thoracic esophagus

Fig. 10.6  Fundoplication wrap in a 2-year-old male. (a) Sagittal grayscale ultrasound image of the gastroesophageal junction shows a masslike appearance (arrow) of the fundoplication wrap just below the

diaphragm (arrowhead). (b) Transverse grayscale ultrasound image depicts the rounded fundoplication wrap (arrow) that mimics the layers of an intussusception

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The four types of hiatal hernia include: type I–sliding hiatal hernia, type II–paraesophageal hernia (often seen with prior fundoplication), type III–components of sliding hiatal hernia and paraesophageal hernia, and type IV–herniation of all or part of the stomach into the thorax (usually with organoaxial malrotation of the stomach) [14–16]. The clinical manifestations of a hiatal hernia can be vague, including frequent burping, spitting, epigastric pain, hosrseness, or wheezing. In the presence of a hiatal hernia, the intra-abdominal esophagus is shortened, the angle between the abdominal esophagus and the posterior gastric wall is increased, and sliding of the gastric fundus toward the diaphragm may be observed [1]. It is not uncommon to see a gas-filled hiatal hernia on chest radiographs, often in patients with a history of prior fundoplication that may have loosened, or in those with neurological disease and increased intra-abdominal pressure predisposing to hiatal hernia. Gas-filled hiatal hernias can be identified on ultrasound, barium studies, plain chest radiographs, and CT examinations (Fig. 10.7). Please refer to Chap. 9: Diaphragm for additional information about hiatal hernia.

a

Pharmacologic agents (including those used for treatment of GERD) and diet adjustment can be used to treat symptoms related to a sliding hiatal hernia. Surgery is performed when there is no relief after medical management. For hiatal hernias of type II, III, and IV, surgery should be performed to prevent complications.

Stomach Technique Patient Positioning The stomach is easily accessible for ultrasound evaluation with the patient in a supine position. The gastroesophageal junction is best seen in a sagittal plane anterior to the aorta. The gastric fundus and greater curvature are well-assessed with the patient in a left lateral decubitus position. The gastric antrum and pylorus are best studied in a right lateral decubitus position. b

S

c

Fig. 10.7 Hiatal hernia in 3 different patients. (a) Sagittal grayscale ultrasound image of the lower left chest demonstrates the gastric fundus (calipers). S, Spleen. (b) UGI series image shows a barium-filled gastric

fundus (arrow) in the lower chest. (c) Chest radiograph reveals a gasfilled hiatal hernia (arrow)

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Ultrasound Transducer Selection The highest resolution linear transducer that penetrates adequately (usually 12–18 MHz) provides the best detail, with settings adjusted for bowel imaging. Gentle compression using the liver as an acoustic window permits evaluation of the gastric body and antrum. Cine loops can be used to document gastric motility. Color Doppler is used to detect hyperemia. Imaging Approaches A 4-hour fast is recommended to reduce gastric food content with an overnight fast of greater than 8 hours improving visibility even further in older children. Filling the stomach with clear fluid and using the liver as an acoustic window permits evaluation of the gastric wall, peristalsis, gastric outlet, and abnormal wall thickening due to masses,

a

inflammation, or retained, undigested material forming a gastric bezoar. Oral contrast agents such as iso-osmolar polyethylene glycol (PEG) can improve bowel distension but water often suffices. Wall measurements should be obtained with the stomach fully distended with fluid when possible, and the scan should be performed in the mid-longitudinal plane proximal to the pyloric canal. Echogenicity of the 5 gastric wall layers represents a combination of the interface echoes and the echogenic properties of the histologic layers of the stomach wall. The normal gastric mucosal thickness is 2–3 mm, the normal thickness of the wall of the gastric antrum is about 2 mm, and the normal pyloric muscle thickness is 2 mm or less. The variability of measurements between distended and nondistended wall measurements (Fig.  10.8) has been

b

c

Fig. 10.8  Normal gastric wall in a 6-week-old infant presenting with frequent non-bilious emesis. (a) Transverse grayscale ultrasound image of the posterior gastric wall (arrow) shows normal definition of the wall layers that appear thickened due to luminal under-distention. (b)

Transverse grayscale ultrasound image of the anterior wall of the stomach (arrows) after the lumen is partially distended with water. (c) Transverse grayscale ultrasound image shows a normal thin gastric wall (arrows) after complete luminal distention with water

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reported as between 4 mm and 5 mm when measuring from the inner echogenic mucosa to the outer border of the gastric wall [17–19]. On cross-sectional imaging, if the image obtained is too close to the contracted pyloric canal, thickening of the pyloric muscle can be erroneously suggested. Similarly, if tangential images are obtained in a longitudinal plane, the muscle may appear falsely thickened.

Normal Development and Anatomy Normal Development At the end of the fourth week of life, the stomach is a straight, hollow tube (Fig. 10.9). From the fourth to sixth weeks, it initially dilates in a fusiform manner followed by preferential growth of its dorsal wall. This results in a bulge that will eventually develop into the greater curvature. In the sixth to eighth weeks of life, the stomach rotates simultaneously along the longitudinal axis and the anteroposterior axis. Normal Anatomy The four main regions of the stomach are the cardia, the fundus, the body, and the pylorus (Fig. 10.2). The cardia is the zone surrounding the lower esophagus and receives esophageal contents. The dome of the fundus is located to the left of the esophageal junction and cephalad to the cardia. The gastric body, the largest portion of the stomach, extends from the fundus to the antrum with the concave border of the lesser curvature and the convex greater curvature along the inferior body of the stomach. The gastric antrum ends at the pylorus where gastric contents exit to the duodenal bulb. In addition to the circular and longitudinal muscle layers present in the bowel wall, the stomach has an inner oblique smooth muscle layer which allows for the mechanical breakdown of food products. The superficial mucosal lining contains mucous glands. Deep to the epithelial layer is the lamina propria containing lymphoid cells and small blood vessels. A thin muscular layer underlies the lamina propria, with overlying submucosa, muscularis propria, and serosa forming the outer layer [20]. The greater omentum hangs down from the greater curvature of the stomach.

Congenital Anomalies The fetal stomach can be visualized as early as 9  weeks of gestation with an identifiable fundus, lesser and greater curvatures, and a pylorus identified around 14 weeks [21]. Various congenital anomalies may affect gastric size. In esophageal atresia with no distal tracheoesophageal fistula, the stomach

M. M. Munden and H. J. Paltiel

may be absent or small on prenatal imaging. In cases of duodenal atresia, the stomach may be large. Congenital obstructions of the stomach are felt to represent the sequelae of vascular accidents in fetal life.

Gastric Atresia Gastric atresia is a congenital defect with complete occlusion of the pylorus. It represents less than 1% of all congenital intestinal obstructions and may have an autosomal recessive inheritance. There is also an association with trisomy 21 and epidermolysis bullosa [22]. The incidence of gastric or pyloric atresia is 1 in 100,000 births, seen prenatally as polyhydramnios with a distended single bubble and obstruction of the gastric outlet [23]. Infants present with non-bilious emesis with the first feeding. Ultrasound will show a distended stomach with obstruction at the outlet. A distended stomach is seen on radiographs with absence of gas distal to the obstruction. The lack of gas in the duodenum helps to distinguish gastric atresia from the more common “double bubble” sign of duodenal atresia described later in this chapter. Gastric atresia is treated surgically soon after birth with resection of the obstructed segment and creation of a gastroduodenostomy. Microgastria Microgastria is a very rare anomaly in which the stomach is a small tubular structure without a recognizable fundus, body, or antrum. The greater and lesser curvatures do not develop. Microgastria can be associated with intestinal malrotation, megaesophagus, asplenia, polysplenia, and congenital heart disease [24, 25] as well as upper limb anomalies, and is seldom an isolated abnormality [26]. The etiology is unknown with a suspected defect in mesodermal development during the fourth or fifth week of gestation. Prenatally, there is polyhydramnios with non-visualization of the stomach. A dilated esophagus with deficient peristalsis is frequently present on prenatal imaging. The gastroesophageal junction is incompetent and patients with microgastria present with vomiting and failure to thrive during infancy, some with aspiration pneumonia due to associated gastroesophageal reflux [27]. A small tubular stomach at ultrasound should raise suspicion for microgastria. Plain films at birth can show gas throughout the gastrointestinal tract. On barium studies, a small, tubular midline stomach is seen with microgastria as well as esophageal dilation [25]. Treatment options for microgastria include medical management with frequent small feedings or jejunal tube feedings [26]. Surgical options include gastric augmentation with

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10  The Gastrointestinal Tract Liver

Dorsal aorta

Stomach

Spleen

Gallbladder

Spleen

Small intestine

Dorsal pancreatic bud

Midgut loop Cranial limb

Umblical cord

Omphaloenteric duct

Caudal limb

Superior mesenteric artery

a

Inferior mesenteric artery

a1

Dorsal mesogastrium Liver

b1

b

Dorsal aorta Liver

Omental bursa

Spleen

Ventral mesentery Gallbladder

Cecum

Stomach

Spleen Transverse colon

Duodenum Hindgut

Umblical cord

Cecal swelling

c

c1

d

d1 Lesser omentum Desending colon Small intestine

Ascending colon

Sigmoid colon

Rectum

e

Cecum and appendix

Fig. 10.9  Diagrams of normal embryological development of the gastrointestinal (GI) tract. (a) By week four of development, the division of the GI tract into the foregut, midgut, and hindgut has occurred. The growth of the GI tract exceeds the volume of the abdominal cavity so that the developing intestine herniates into the umbilicus. The GI tract then undergoes a 90-degree counterclockwise rotation around the superior mesenteric artery. (b) The superior limb of the intestinal loop will form the ileum and the inferior limb will form the colon. The bowel will

continue to grow and rotate for the next 5 weeks. (c) The proximal portion of the midgut loop has migrated from a superior position to the right side of the body and the distal portion of the loop has migrated from an inferior position to the left. (d) In week ten, the bowel retracts back into the abdominal cavity where it undergoes a 180-degree counterclockwise rotation. The cecum is then located in the right upper quadrant of the abdomen. (e) Enlargement of the large intestine pushes the cecum down to its final position in the right lower quadrant of the abdomen

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a jejunal loop and gastric excision with a Roux-en-Y esophagojejunostomy [28, 29]. Esophagus

 astric Diaphragm (Antral Web) G A gastric diaphragm (or antral web) is a thin membrane about 2–4  mm in thickness extending across the gastric antrum at a distance from 1 to 7 cm proximal to the pylorus which can lead to gastric outlet obstruction. The web is a mucosal structure and can vary from a crescent of mucosa to a circumferential web with a central opening. The etiology of this unusual finding in children is uncertain, with an incidence of 1 in 100,000 births [30]. Neonates may present with difficulty feeding and non-bilious emesis. Some patients present later in life with vague symptoms of early satiety, epigastric pain, postprandial vomiting, and transient episodes of vomiting. Ultrasound of a fluid-stomach may reveal an echogenic fold or diaphragm-like structure crossing the distal stomach from the lesser to the greater curvature with associated gastric dilation and delayed gastric emptying. The pyloric channel is normal [30, 31]. On barium studies, an antral web is seen as a persistent band-like linear defect at the gastric antrum causing a “double bulb” sign with the antral chamber between the pylorus and the web appearing as one bulb and the proximal duodenum appearing as the second bulb. Antral webs can be treated with surgical myotomy and endoscopic dilation. Intraoperative endoscopic gastroduodenoscopy combined with operative antral web resection has been beneficial in localizing the webs at surgery [32].

Acquired Obstruction  ypertrophic Pyloric Stenosis H Hypertrophic pyloric stenosis (HPS) is defined as an abnormal thickening of the muscular layer and abnormal elongation of the pyloric canal with failure of relaxation leading to gastric outlet obstruction and projectile, forceful non-bilious emesis (Fig. 10.10). Symptoms typically occur from 2 to 12 weeks of age, but very rarely after 12 weeks. Though unusual, HPS also can present before 2 weeks of age. Those infants with a very early presentation are more likely to have a positive family history of HPS. HPS occurs in about 2–3.5 per 1000 live births and is more common in males than in females with a 1.5-fold increased risk in first-born children and a fivefold male predominance. It is less common in infants of older mothers. Prematurity of less than 37 weeks may be a risk factor [33]. Premature infants develop HPS at a later chronological age (but earlier post-menstrual age) than term infants, with some studies showing a higher female preponderance [34, 35]. Maternal smoking increases the risk of HPS by 1.5- to twofold. Some studies have found an increased incidence with bottle feeding (not expressed breast milk) [36, 37].

Duodenum

Pyloric stenosis

Stomach

Fig. 10.10  Diagram of pyloric stenosis

The etiology of HPS remains unclear although there is a genetic predisposition, with a study from Denmark showing an almost 200-fold higher rate among monozygotic twins, and a 20-fold increased rate among dizygotic twins and siblings [38]. Studies have postulated abnormal innervation of the muscle layer, with findings of a reduced number of nerve terminals, abnormal nitric oxide synthase activity, and deficient interstitial cells of Cajal [39]. An overly distended stomach may be noted on plain radiographs in patients with HPS. Ultrasound has replaced barium studies for the diagnosis of HPS, with an accuracy approaching 100% [40]. The gastric outlet is easily studied by placing the infant in a right lateral decubitus position, using the liver as an acoustic window. Although the stomach in HPS is often already distended, a small amount of clear fluid can help delineate pyloric anatomy. However, over-distention of the stomach displaces the pyloric channel posteriorly and may require repositioning of the patient into either a left lateral decubitus position, or switching to a lower frequency transducer for deeper penetration and optimal imaging. Pyloric measurements should be obtained in the midlongitudinal plane of the stomach or in cross section at or just proximal to the pyloric channel, measuring the muscle thickness of a single wall, excluding the mucosa and submucosa. If obtained in a tangential plane, the muscle may appear falsely thickened. In infants with HPS, the pyloric ring is no longer clearly defined and the thickened pyloric channel measures from 1.4 to 2 cm in length (Fig. 10.11). The muscle thickness of the elongated pyloric channel changes rather abruptly from the 1-mm thickness of the normal antrum to 3  mm or greater in the hypertrophied

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canal [40]. During the ultrasound examination, the pyloric channel should at no time appear normal with gastric peristalsis. In premature infants with HPS, ultrasound measurements are not affected by weight or corrected gestational age [35]. Treatment for HPS is surgical. Laparoscopic pyloromyotomy is widely used now as an alternative to open pyloromyotomy with good success. Laparoscopic procedures allow a shorter time to full feeding with slightly shorter hospital a

stays [41]. Persistent vomiting in the post-surgical infant can be evaluated by ultrasound, but should be interpreted with caution, as the muscle can remain thickened up to 8 months after surgery [42, 43].

Pylorospasm Pylorospasm has a similar presentation to HPS but represents a spasmodic contraction of the pylorus, not a fixed obstruction. Pylorospasm is characterized by a transient spasm b

c

Fig. 10.11  Hypertrophic pyloric stenosis in a 3-week-old male with projectile vomiting and a normal gastric antrum shown for comparison. (a) Transverse grayscale ultrasound image demonstrates an elongated pyloric channel and marked muscle wall thickening (arrow). (b) Transverse gray-

scale ultrasound image shows a normal pyloric channel (arrow) for comparison with no thickening of the antropyloric muscle, allowing passage of gastric contents. (c) Abdominal radiograph reveals a distended stomach (arrows) due to underlying pyloric stenosis

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of the pyloric muscle without gastric outlet obstruction. Clinical presentation is similar to hypertrophic pyloric stenosis with persistent non-bilious vomiting in the young infant. A transient pyloric canal elongation and muscle thickening may be present during ultrasound evaluation of the pyloric channel and may mimic HPS or raise suspicion for pyloric stenosis in evolution. However, the thickened pyloric muscle relaxes with observation to allow gastric emptying [39, 42]. The muscle wall thickness of pylorospasm can overlap with that of HPS, although it is not a constant finding (Fig. 10.12, Table 10.1). On UGI studies, intermittent flow of contrast into the duodenum differentiates pylorospasm from HPS. In those infants with a pyloric muscle thickness of 2–3 mm and an elongated pyloric channel that does not relax throughout the ultrasound examination, continued clinical monitoring and short-term interval ultrasound follow-up may be warranted to assess for pyloric stenosis in evolution.

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Ultrasound of the stomach in patients with prostaglandininduced foveolar hyperplasia will show a polypoid, echogenic thickening of the antral mucosa without extension into the lamina propria (Fig. 10.13). This contrasts with HPS that involves the muscular layer, not the mucosa. Color Doppler imaging of the mucosa in patients with foveolar hyperplasia may show increased vascularity in the deep gastric mucosa [46]. Foveolar hyperplasia resulting from prostaglandin therapy is treated medically, with spontaneous resolution after cessation of treatment. There have been a few reported cases of the coexistence of both foveolar hyperplasia and HPS, a possibility that should be considered in young infants if symptoms do not resolve after discontinuation of prostaglandins [47].

 rostaglandin-Induced Foveolar Hyperplasia P Foveolar cells cover the gastric epithelium and focal polypoid hyperplasia can occur in the gastric antral mucosa, and to a lesser extent in the intestine. In the neonate or infant with cyanotic congenital heart disease treated with prolonged prostaglandin therapy to maintain patency of the ductus arteriosus, gastric outlet obstruction can develop as a result of foveolar hyperplasia. This can lead to elongation and polypoid thickening of the antropyloric channel [44, 45]. Foveolar hyperplasia can clinically mimic HPS in patients who present in the age range typical of hypertrophic pyloric stenosis.

Gastric Volvulus Gastric volvulus is a rare abnormal rotation of the stomach leading to gastric outlet obstruction, and is classified into organoaxial and mesenteroaxial types. With organoaxial gastric volvulus, the stomach rotates around its long axis and becomes obstructed with an inversion of the greater and lesser curvatures if rotated greater than 180 degrees. Organoaxial volvulus accounts for about two-thirds of gastric volvulus in children. The most commonly associated condition is congenital diaphragmatic hernia, although acquired diaphragmatic hernia, eventration, and paraesophageal hernia can be complicated by gastric volvulus (Fig. 10.14) [48, 49]. With mesenteroaxial gastric volvulus, the stomach rotates around its short axis with a displacement of the antrum and pylorus above the gastroesophageal junction, presenting

Fig. 10.12  Pylorospasm in a 5-week-old infant presenting with forceful emesis. (a) Transverse grayscale ultrasound image shows an elongated pyloric channel with thickening of the pyloric muscle (arrow),

which mimics pyloric stenosis. (b) Transverse grayscale ultrasound image after several minutes of observation shows a patent, normalappearing channel (arrow). The stomach is not distended

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10  The Gastrointestinal Tract Table 10.1  Ultrasound features of hypertrophic pyloric stenosis versus pylorospasm Pyloric stenosis Muscle wall thickness >3 mm Change with time No Associated gastric distention Yes

Pylorospasm May be >3 mm Yes No

a

acutely with severe obstruction. Although organoaxial volvulus is more common overall than mesenteroaxial volvulus, most cases of mesenteroaxial volvulus occur in children. Early and accurate diagnosis of acute gastric volvulus is essential to prevent ischemia and perforation. Acute gastric volvulus usually occurs in a child less than 5  years of age

b

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Fig. 10.13  Prostaglandin-induced foveolar hyperplasia in a 1-monthold infant with vomiting. Patient receiving extracorporeal membrane oxygenation (ECMO) for complex congenital heart disease. Transverse (a) and sagittal (b) grayscale ultrasound images of the gastric body

show polypoid thickening (arrows) of the gastric wall. (c) Chest radiograph reveals diffuse gastric wall thickening (arrow) as well as support apparatus for ECMO

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Fig. 10.14  Diaphragmatic hernia with organoaxial gastric volvulus in a neonate. (a) Chest radiograph shows the intrathoracic stomach (arrows) due to a diaphragmatic hernia. (b) Oblique power Doppler ultrasound image obtained through the lower chest shows the gastric

antrum (arrow) lying posterior to the gastric fundus (asterisk). (c) Image from an UGI series reveals organo-axial volvulus of the intrathoracic stomach (arrow). F, Fundus of stomach

who presents with non-bilious emesis, epigastric distention, and pain. Chronic volvulus in infants may manifest with emesis, feeding difficulties, and failure to thrive. A diagnosis of gastric volvulus is usually made on the basis of plain radiographs and UGI series. Radiographic findings include spherical gastric distension, herniation of the stomach above the diaphragm, diaphragmatic elevation, and a paucity of distal bowel gas. With organoaxial volvulus, the greater curvature of the stomach may be seen above the lesser curvature. Ultrasound does not generally play a role in diagnosis, although in experienced hands it can be diagnostic in children with mesenteroaxial

gastric volvulus, revealing a displacement of the antrum above the gastroesophageal junction. An UGI series can evaluate the rotation of the stomach and identify gastric outlet obstruction. CT will show the rotated stomach and a transition point [50]. Treatment of gastric volvulus is surgical, with a reduction in the volvulus, gastropexy, and repair of any potential diaphragmatic hernia or defect. Acute gastric volvulus can induce shock, and immediate gastric suction with removal of gastric contents is done to temporarily improve any associated compartment syndrome [51].

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Gastric Wall Thickening Gastritis Gastritis, gastropathy, and peptic ulcer disease are often considered together in the spectrum of acid peptic disease. If untreated, gastritis can progress to peptic ulcer disease. Helicobacter pylori is the most common gastric microbial pathogen and is a major risk factor for gastritis, gastric and duodenal ulcers. The gastric antrum is the most common site of inflammation and the submucosal layer is often colonized. About half of the world’s population is estimated to be infected with H. pylori, usually acquired within the first 5 years of life. The prevalence of infection is higher in developing countries and is the most important cause of primary duodenal ulcers in children [52]. Less common infectious etiologies of gastritis include cytomegalovirus, fungi such as histoplasmosis, and parasites. High-dose steroids, non-steroidal anti-inflammatory drugs, stress/trauma, inflammatory bowel disease, systemic mastocytosis, and chronic renal disease can also lead to gastritis [53]. Symptoms are nonspecific and include epigastric pain, nausea, vomiting, anorexia, and occasionally hematemesis. Ultrasound of gastritis shows nonspecific gastric antral wall and mucosal thickening (Fig.  10.15). Significantly greater thickening of the muscularis mucosa and muscular layers of the antrum occur in the setting of infection than in patients with other forms of gastritis [54]. UGI barium studies show nonspecific gastric fold thickening primarily in the antrum in patients with H. pylori gastritis [54, 55].

Fig. 10.15  Gastritis in a 4-month-old male. Transverse grayscale ultrasound image of the distal stomach reveals thickening (arrow) of all layers of the antropyloric region of the stomach

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The gold standard for diagnosis of H. pylori gastritis is endoscopy. Noninvasive urea breath testing and stool antigen testing are used in follow-up. Treatment for gastritis is medical. Triple therapy using proton pump inhibitors in combination with antibiotics has been effective in patients with H. pylori gastritis.

Ménétrier Disease Pediatric Ménétrier disease is a rare protein-losing gastropathy in children with marked hypertrophy of the folds of the gastric body and fundus, and sparing of the antrum [56]. It may be clinically confused with eosinophilic gastritis as peripheral eosinophilia occurs in more than half of the patients with Ménétrier disease. The etiology is unknown with speculation regarding its link to chemical irritants, toxins, and possibly autoimmunity. Cytomegalovirus (CMV) infection of the stomach is found in about one-third of patients [57, 58]. Ménétrier disease can present with nausea, vomiting, and abdominal pain, with symptoms often developing after a respiratory infection. Peripheral edema is reported in the majority of children due to the severe protein loss which can lead to initial suspicion of a renal disorder. The diagnosis can be suspected upon detection of thickened mucosal folds during imaging with ultrasound, barium studies, or CT.  Although a specific diagnosis may not be made by ultrasound, it can still be used to follow therapy. Clinical and pathologic correlations are needed to make the diagnosis, as endoscopic biopsy alone is insufficient. A full thickness gastric biopsy is often required. Ménétrier disease in children is generally benign and selflimited, lasting about 5  weeks. Treatment of CMV, when detected, usually leads to remission. In the absence of CMV infection, treatment is usually supportive and includes hydration, histamine 2 receptor antagonists, and proton pump inhibitors with albumin replacement [59, 60]. Eosinophilic Gastroenteritis Eosinophilic gastroenteritis is an uncommon benign inflammatory infiltration by eosinophils that is either primary or secondary (due to allergies or parasites) in etiology. Any segment of the GI tract can be involved, but the stomach and small intestine are the most commonly affected. Prevalence in the United States ranges from 8 to 28 per 100,000, and is more common in children than in adults. Excess weight, higher socioeconomic status, and Caucasian race may be risk factors with a possible hereditary component. About one half of patients have concomitant allergic disorders, including asthma and eczema. Peripheral eosinophilia is present in about 70% of patients [61]. Eosinophilic gastroenteritis usually presents with chronic, nonspecific symptoms including abdominal pain, dysphagia, diarrhea, nausea, and weight loss. Protein-losing enteropathy, ascites, and GI bleeding can also occur.

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Radiologic findings are nonspecific, variable, and can even be absent. Ultrasound may show gastric fold thickening and pseudopolyposis of the gastric body and antrum along with small bowel wall thickening and ascites. Barium studies show a nonspecific mucosal fold thickening and nodularity that is most prominent in the gastric antrum. The antrum can be narrowed and nodular in chronic disease and may result in obstruction. CT shows diffuse thickening of mucosal folds, submucosal edema, ascites, and occasionally obstruction [62]. Diagnosis requires the presence of GI symptoms, histologic evidence for eosinophilic infiltration, and exclusion of other causes of tissue eosinophilia. Biopsy plays an important role in diagnosis, although multiple biopsies may be required due to the patchy distribution of the eosinophilic infiltrates [63]. Spontaneous remission occurs in about a third of cases and food allergy appears to play an important role. Therapeutic options include dietary modification as the first option, followed by steroids, leukotriene inhibitors, and mast cell stabilizers. Relapses are frequent [63, 64].

 hronic Granulomatous Disease of the Stomach C Chronic granulomatous disease is a rare inherited primary immunodeficiency commonly transmitted as an X-linked or autosomal recessive disorder affecting about 4–5 per million live births [65]. Chronic granulomatous disease affects males more than females and about two-thirds have the X-linked recessive form. There is a defect in the genes encoding for the nicotinamide dinucleotide phosphate (NADPH) oxidase complex which leads to a defective oxidative burst of the neutrophils and macrophages resulting in an inability to destroy catalase-positive bacteria and fungi [66]. Patients are susceptible to bacterial and fungal infections which lead to inflammation and granuloma formation in the affected tissues (lung, cervical nodes, GI tract, liver, and spleen). Patients receive life-long antibiotic and antifungal treatment, which has led to improved overall survival. Children are usually diagnosed within the first 5 years of life due to severe, recurrent bacterial and fungal infections. When the stomach or intestinal wall is involved, the inflammation can cause gastric pain, diarrhea, vomiting, and gastric outlet obstruction. On ultrasound examination, there will be circumferential wall thickening of the gastric antrum with narrowing, a distinctive finding seen in approximately 16% of affected children (Fig. 10.16) [67]. On UGI series, the antrum will show concentric narrowing with an elongated pyloric channel and delay in gastric emptying. Patients with X-linked disease are more prone to gastric outlet obstruction. Computed tomography (CT) may show enlarged, low attenuation mesenteric nodes that can later calcify. Magnetic resonance (MR) imaging can distinguish acute from chronic thickening with acute disease being hyperintense on T2-weighted images and showing post-contrast enhancement, while chronic disease is not T2 hyperintense nor does it enhance.

Fig. 10.16  Chronic granulomatous disease in a 10-year-old male with bilious vomiting. Transverse grayscale ultrasound image shows marked thickening (arrow) of the gastric wall in the antropyloric region

Patient survival has improved with long-term antibiotic and antifungal therapy. The only definitive treatment at present is hematopoietic stem cell transplantation with an overall survival rate of greater than 90% for children undergoing transplantation when less than 14 years of age. Recent publications describe gene therapy for X-linked recessive chronic granulomatous disease as an alternative for those without a human leukocyte antigen (HLA) matched donor [68, 69].

Benign Masses of the Stomach  astric Duplication Cyst G Duplication cysts and mesenteric cysts are the most common cysts of the GI tract with an incidence of 1  in 4500 births. Enteric duplication cysts can occur anywhere from the base of the tongue to the anus but are most commonly seen in the distal ileum along the mesenteric border (33%). Only 7% involve the stomach [70]. They are often detected prenatally or within the first few years of life. They are believed to arise between the fourth and eighth weeks of gestation with several proposed theories as to etiology, including failed luminal recanalization in the esophagus, small bowel, and colon. A reported increased incidence of associated spinal defects, cardiac, or urinary malformations occurs in 16–26% [70]. Heterotopic tissue is present in about 35% of gastric duplication cysts and up to 10% contain ectopic pancreatic tissue in the submucosal layer. The rare intrapancreatic duplication cyst

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can be confused with a pancreatic pseudocyst. Intrapancreatic duplication cysts fill with secretions and can erode into the pancreatic duct leading to pancreatitis. Duplication cysts involving the pancreas are most commonly found in infants and children [71, 72]. Duplication cysts may be an incidental finding on routine ultrasound examination but can lead to gastric outlet obstruction, pancreatitis, bleeding from ulceration, or vague epigastric fullness. The characteristic well-defined inner echogenic mucosal layer and outer hypoechoic muscular layer of the duplication cyst – the “gut signature” – can help establish the diagnosis by

ultrasound (Figs. 10.17 and 10.18). Eighty percent of duplication cysts are spherical and have no communication with the bowel lumen, while 20% are tubular and do communicate with the bowel lumen [73]. Foci of ectopic tissue within a duplication cyst can lead to inflammation, ulceration, and hemorrhage, resulting in a more complex appearance by ultrasound. Some cysts may be pedunculated. Most gastric duplication cysts are located along the greater gastric curvature [74]. Imaging pitfalls exist, as there are other cysts within the abdomen that can have a double layer “pseudo gut signature” appearance that may be misinterpreted as a duplication

Fig. 10.17  Duplication cyst in the region of the gastric outlet in a 2-week-old infant with persistent vomiting. Transverse (a) and sagittal (b) grayscale ultrasound images of the gastric outlet reveal an anechoic,

avascular cyst (calipers; arrow). Gut signature is not well-demonstrated. (c) Axial T2-weighted, fat-suppressed MR image demonstrates fluid signal (arrow) within the lesion

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Patients with a mature teratoma or a low-grade immature teratoma and serum alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (HCG) hormone values in a normal range are treated by surgical excision with close clinical follow-up. These tumors carry a good prognosis and plasma AFP levels can be used for monitoring purposes [78–80].

Fig. 10.18  Gastric duplication cyst in a 17-month-old female. Transverse grayscale ultrasound image obtained in the right mid-abdomen demonstrates a well-circumscribed cyst containing internal echogenic debris. The cyst wall has a characteristic “gut signature,” with an echogenic inner mucosal layer and a hypoechoic outer muscular layer

cyst  [75]. Barium studies show an intramural filling defect impressing the gastric contour. CT with contrast demonstrates a thick-walled, low-attenuation lesion with enhancement of the lining, occasionally with calcification in the wall. MR imaging will show increased signal within the cyst on fluidweighted sequences. Rare reports of malignant transformation exist, so surgery is the recommended treatment in all cases [76]. Surgical removal requires complete cyst excision along with the shared wall with the stomach. Marsupialization of cysts that communicate with the stomach risks exposure of the cyst mucosa to gastric contents. Surgical excision is also the mainstay of therapy for the rare pancreatic duplication cyst.

Gastric Teratoma Extragonadal teratomas are very rare in children, with the majority occurring in the sacrococcygeal region or within the mediastinum. Gastric teratoma has been reported but is quite unusual, representing 1% of all teratomas, occurring before 1 year of age and with a male predominance. The majority of these tumors arise from the greater curvature and posterior wall of the stomach. The lesions can present as a palpable mass or with emesis, although those with intramural extension may present with gastrointestinal bleeding and gastric perforation [77]. As with teratomas elsewhere, calcification, fat, and cystic areas are identified at imaging. While these tumors may be found at initial ultrasound examination and calcifications may be seen on plain radiographs, the large size of these tumors usually requires cross-sectional imaging with CT or MR for diagnosis.

Gastric Lipoma Gastric lipoma represents less than 1% of all gastric tumors and is usually detected incidentally at autopsy. It is benign and composed of mature adipose tissue and usually occurs in the submucosa of the gastric antrum. In adults, gastric lipomas can be larger with ulcerations. A few cases have been reported in children presenting with hematemesis due to mucosal ulceration, intermittent vomiting, and melena [81]. Most of the imaging findings have been reported in adults and diagnosed by CT after initially noted on an UGI series as an ulcerated lesion with smooth margins. A low attenuation mass can be seen on barium studies due to the presence of fatty tissue [82]. Surgical removal is the treatment of choice in large, symptomatic gastric lipomas. Smaller lesions can be treated by endoscopic removal [83].  ocal Foveolar Hyperplasia of the Stomach F Focal foveolar hyperplasia is rare in children. It is caused by an accumulation of inflammatory cells in the gastric mucosa resulting in large, hypertrophic folds that form broad-based polyps. Foveolar hyperplasia occurs in response to injury, involving both the gastric antrum and body in the presence of H. pylori gastritis, but is confined to the antrum in non-H. pylori gastritis [84]. Primary bile reflux has also been reported to lead to foveolar hyperplasia and vascular congestion in children [85]. The few reported cases located in the gastric antrum presented with non-bilious vomiting, weight loss, gastric outlet obstruction, and gastrointestinal bleeding [86]. Ultrasound shows superficial lobulated thickening of the gastric mucosa leading to partial gastric outlet obstruction. Color Doppler reveals intense hyperemia of the gastric antral wall deep to the mucosa [46]. On an UGI series, there may be elongation and narrowing of the pylorus which can mimic pyloric stenosis in the appropriate age range. Diagnosis is difficult and may require endoscopy with biopsy. Treatment is symptomatic and supportive. If H. pylori is documented, appropriate therapy aimed at eradicating the infection is undertaken. I nflammatory Gastric Myofibroblastic Tumor Inflammatory myofibroblastic tumor is another very rare benign mesenchymal neoplasm of unknown etiology that can involve the stomach, although more often these tumors involve the lung. They occur in fewer than 1 in one million individuals and are composed of myofibroblastic spindle

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cells with an inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils. There is a wide range of age at presentation with females affected more than males, and a mean age of 9 years at diagnosis [87, 88]. A solitary mass is the most frequent, although visceral and cutaneous involvement can occur with the multicentric form of tumor. Clinically, patients may present with weight loss, fever, anemia, thrombocytosis, or with a slow growing mass leading to obstruction. Ultrasound reveals a hypovascular, solid mass with central hypoechoic necrosis and calcification. Tumor size can range from several cm to more than 10 cm. They may be lobulated in contour and will demonstrate prominent enhancement on CT. On MR imaging they are typically isointense to muscle on T1-weighted sequences with variable T2 intensity depending on the fibrous content [89]. Biopsy is required for diagnosis and tumors should be surgically removed. While solitary and multicentric tumors often have a benign course, those with positive margins after surgical resection are associated with recurrence and increased mortality [89, 90]. Adjuvant chemotherapy is used if there is a local invasion or in rare cases of metastasis.

Gastric Bezoar A bezoar consists of ingested material that mainly accumulates in the stomach although it can develop in any portion of the gastrointestinal tract and result in obstruction. Lactobezoars occur mainly in infants who are fed improperly constituted or high caloric formula. Many are preterm infants fed a high casein–whey ratio, highly concentrated formula. Lactobezoars can occur in full-term infants as well, perhaps related to poor gastric emptying and decreased gastric secretions. Trichobezoars are more common and occur in older children from chewing and swallowing hair that accumulates in the stomach, sometimes extending into small bowel [91]. Phytobezoars develop as a result of poorly digested fruit and vegetable fibers. Bezoars in adults often occur following gastric surgery and will not be further discussed. A bezoar can be suspected by plain radiography on the basis of a large amount of mass-like undigested gastric material in patients presenting with early satiety, abdominal pain, poor weight gain, and bowel obstruction. It may appear as mottled solid matter filling the stomach or small bowel, although a large, recently ingested meal can have a similar appearance. Ultrasound can be used for diagnosis, although a correct diagnosis of a gastric bezoar was made by ultrasound in only 25% of patients in one series [92]. Filling the stomach with clear fluid and positioning the patient upright and in both decubitus positions to separate the bezoar from the

gastric wall is useful to exclude a gastric mass (Fig. 10.19). Trichobezoars form an echogenic arc with marked acoustic shadowing caused by air trapped within the conglomerate of hair fibers. This appearance helps to differentiate a gastric bezoar from non-pathologically ingested food content. Barium should be administered with caution as it can interfere with therapeutic endoscopy. CT will show a lowdensity mass mixed with air bubbles, better seen with window manipulation for optimal visualization [92]. Lactobezoars are usually medically treated with bowel rest and a change to predigested formula. Some success has been described with the use of intra-gastric N-acetylcysteine for lactobezoars as well as with the ingestion of Coca-Cola® for phytobezoars [93, 94]. Large-channel endoscopes have been used to remove gastric phytobezoars with suction. Trichobezoars are often surgically removed although some have been treated with endoscopic removal [95].

 ther Benign Masses O Other benign gastric masses are rare in children. Heterotopic pancreas, plasma cell granuloma, and leiomyoma can occur, among others. These lesions may manifest as focal thickening of the gastric wall or as a polypoid mass [96, 97]. The ultrasound features of these lesions are nonspecific and diagnosis rests with clinical correlation and/or biopsy.

Malignant Gastric Tumors Lymphoma Non-Hodgkin lymphoma (NHL) is not common in the pediatric population, affecting about 700–800 children per year in the United States. Burkitt and Burkitt-like lymphomas are the most frequent subtypes of non-Hodgkin lymphoma in childhood, accounting for 35–40% of NHL [98]. The sporadic form seen in North America is associated with Epstein–Barr virus in 15% of cases. Most pediatric cases of NHL are high grade with aggressive behavior. Burkitt lymphoma involves the GI tract in a reported 23% of cases, affecting the distal small bowel, cecum, and appendix most commonly, and often presenting with obstructive symptoms or pain. Burkitt lymphoma is the most rapidly growing tumor in children [99]. The stomach is rarely involved. The peak age for Burkitt lymphoma is 5–15 years although those presenting younger than age 5 years have a slightly better outcome [100]. Rare reported cases of gastric involvement have presented with vague, episodic abdominal pain, vomiting, weight loss, and constipation.

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Fig. 10.19  Gastric trichobezoars in two adolescent females presenting with early satiety and weight loss. (a) Transverse grayscale ultrasound image of the stomach in the first patient shows the arclike contour of a trichobezoar (asterisk) in the upright position, outlined by water administered during the study. (b) UGI series image of the second patient reveals a trichobezoar (arrow) outlined

by barium. (c) Coronal contrast-enhanced computed tomography (CT) image shows a conglomerate of hair (arrows) filling the stomach and containing entrapped air. (d) Gastric trichobezoar following surgical removal. (Image courtesy of Dr. Harry Kozakewich, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA)

Ultrasound findings of gastric lymphoma include thickening of the hypoechoic layers of the gastric wall with or without loss of layer stratification (Fig. 10.20). Masses can protrude into the lumen and result in luminal narrowing [100, 101]. Plain radiographs may show gastric wall thickening and contrast studies will show a gastric mass. Contrast-enhanced CT and fluorodeoxyglucose (FDG) positron emission tomogra-

phy (PET) provide anatomic and metabolic imaging, now the standard of care. PET/MR imaging may provide an alternative to PET/CT yielding high-quality images with a reduction in radiation dose [98]. Treatment is surgical for localized disease, although most children with NHL are treated with chemotherapy. Treatment is based on lymphoma type and stage.

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Fig. 10.20  An 11-year-old female with Burkitt lymphoma involving the stomach. (a) Transverse grayscale ultrasound image reveals a large, hypoechoic mass (asterisk) encasing the gas-filled stomach (S). (b)

Coronal contrast-enhanced CT image shows the low-attenuation mass (asterisk) surrounding the stomach. There is a large ulceration (arrow) along the lesser gastric curvature

GI Stromal Tumor GI stromal tumor (GIST) is the most common neoplasm of the stomach in children and the most common mesenchymal neoplasm of the GI tract. It originates from the interstitial cells of Cajal, the cells that mediate communication between the autonomic nervous system and the smooth muscle. GI stromal tumors are distinguished from other mesenchymal neoplasms pathologically by their expression of KIT (CD117), a tyrosine kinase growth factor receptor. GIST has a reported incidence of 0.11 cases per million in the pediatric population and 0.4% of all GIST patients are less than 20  years of age [102]. GIST in children is distinct with characteristics that vary from the adult form, including a median age at diagnosis in the second decade compared to 63  years in adults, a female predilection (70% of cases) compared to an equal gender distribution in adults, and lack of mutation in KIT or platelet-derived growth factor receptor A (PDGFRA) in 85% of cases [102]. Tumors lacking these mutations are referred to as “wild type.” A pediatric GIST is most likely to present as a GI bleed due to its predilection for the stomach, but can also manifest with pain, vomiting, and early satiety. GIST can occur in isolation or in association with Carney’s triad (GIST, pulmonary chondroma, and paraganglioma), Carney–Stratakis syndrome (GIST and paraganglioma), and neurofibromatosis type I [103]. No distinguishing ultrasound or other imaging feature can identify a GIST from other mesenchymal neoplasms such as leimyoma or leiomyosarcoma. GIST is generally exophytic and rarely calcifies (Fig. 10.21). It contains cystic regions and

hemorrhage and may invade adjacent organs and metastasize to the liver and omentum. Plain radiographs may show a mass indenting the gastric wall, rarely with calcification. Barium studies will show a smooth, well-circumscribed mass along the gastric wall. CT, MR imaging, and PET may be used in staging and follow-up of an intramural mass with extragastric extension. The majority of these lesions enhance on CT and MR imaging. MR imaging features depend on the degree of necrosis and hemorrhage [103]. Treatment is surgical excision. In patients with localized disease, complete surgical removal with negative margins is achieved in 93%. However, the event-free survival rate at 10 years is only 16% [104].

 ther Malignant Masses O Other malignant gastric tumors are extremely rare in children. Leiomyosarcoma represents 2–4% of soft tissue sarcomas in the pediatric population although they rarely involve the stomach. It is crucial that leiomyosarcoma be differentiated from GIST for treatment purposes. Presentation with severe anemia with a large gastric filling defect on UGI series has been reported [105]. Primary gastric adenocarcinoma is exceedingly rare in children, constituting 0.05% of pediatric GI malignancies. While H. pylori is commonly implicated as an etiology in adults, the etiology of this rare tumor is unknown in children. Symptoms include vomiting and abdominal pain with metastatic disease often found at presentation due to the nonspecific clinical presentation and rarity of the disease [105].

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Fig. 10.21  GI stromal tumor (GIST) in a 15-year-old female with unexplained anemia. (a) Transverse grayscale ultrasound image shows multiple echogenic nodules (arrowheads) arising from the wall of the stomach, with a large exophytic component (asterisk) along the lesser curvature. (b) Sagittal grayscale ultrasound image of the distal

stomach (S) reveals multiple lobulated, exophytic masses (arrows) extending to the liver (L). (c) Coronal contrast-enhanced CT image depicts the heterogeneous, low-attenuation masses (arrows) arising from the stomach (S)

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Small Bowel Technique Patient Positioning For ultrasound of the small bowel, the patient is mainly scanned in a supine position, with additional decubitus positioning used depending on the clinical question. To assess the duodenum for hematoma or normal retroperitoneal position, a right lateral decubitus position is helpful in identifying the proximal duodenum which can then be followed with the patient supine as it extends transversely between the aorta and the superior mesenteric artery. Placing the patient in a left lateral decubitus position often helps displace superficially located bowel loops and improves access to the deeper regions of the abdomen. With necrotizing enterocolitis in infants, supine and decubitus positioning assists with distinguishing air within the bowel lumen from air in the bowel wall, i.e., pneumatosis. Ultrasound Transducer Selection High-resolution transducers (15–18 MHz) with settings optimized for bowel detail are used for both grayscale and color Doppler imaging. In the older child, a convex lower frequency transducer (5–9 MHz) may be necessary for adequate penetration. Imaging Approaches Ultrasound imaging in the emergent setting requires no preparation, while patients undergoing evaluation for inflammatory bowel disease (IBD) or other elective small bowel studies should not eat solids for 4 hours prior to examination. Ingestion of clear liquids (12–16 ounces) is encouraged for elective studies to distend the small bowel and fill the bladder, which elevates the small bowel loops out of the pelvis. Filling the stomach with water provides an acoustic window for evaluation of the duodenum and proximal jejunum. Carbonated drinks are discouraged in order to avoid gas artifact. Ultrasound contrast is useful for evaluating flares and response to therapy in patients with IBD [106]. The normal duodenum can typically be examined in the fasting patient from the gastric antrum with the patient in a right lateral decubitus position, then along its retroperitoneal position between the superior mesenteric artery (SMA) and aorta with the patient supine. If water or milk is given, the gastric content can be followed through the duodenum. The orientation of the SMA and superior mesenteric vein (SMV) should be noted. When an inflammatory process is encountered in the right lower quadrant, the small bowel proximally within the left lower quadrant and jejunal loops in the left

upper quadrant are studied in sagittal and transverse planes to assess for bowel wall thickening, dilated loops, mesenteric adenopathy, and interloop abscess. The remaining small bowel can be studied with gentle, graded compression in a supine position. To evaluate the distal ileum for infectious enteritis or Crohn disease, gentle anterior compression with simultaneous posterior manual compression is useful in separating bowel loops. Cine clips are obtained to document small bowel motility.

Normal Development and Anatomy Normal Development In contrast to the stomach which develops a dorsal bulge in early embryonic life, the duodenum develops a ventral bulge (Fig. 10.9). The proximal duodenum, from the pylorus to just past the papilla, is derived from the foregut, and maintains its blood supply from the celiac axis, the major artery to the foregut. The rest of the duodenum is derived from the midgut, and is supplied by the superior mesenteric artery, the major artery to the midgut, through the dorsal mesentery. When the stomach rotates during embryonic life, the duodenum also alters in position, with its formerly concave dorsal border subsequently opening to the left, the so-called “C-loop.” There is subsequent resorption of the dorsal mesentery that leaves a covering of visceral peritoneum along its anterior surface. The loss of mesenteric attachment results in the eventual retroperitoneal location of the duodenum beyond the level of the bulb [107]. Normal Anatomy On ultrasound evaluation, normal small bowel wall thickness is less than 2.5 mm with the inner hyperechoic mucosa and outer hypoechoic muscular layers visible. Small bowel loops are decompressed if no fluid has been administered. Normal bowel is not hyperemic with only minimal flow detected. With normal bowel rotation, the four segments of the duodenum can be identified from the pylorus to the duodenojejunal junction, with the third portion coursing posterior to the pancreas, between the aorta and the superior mesenteric artery. The third portion of the duodenum can be documented in the aorto-mesenteric space in the sagittal plane (Fig.  10.22). Normal folds of jejunum transition to the smoother appearance of ileum in the mid-abdomen and right lower quadrant. Jejunal loops show more peristalsis than normal ileum [106]. The terminal ileum joins the cecum in the right lower quadrant, entering just cephalad to the appendix.

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b

Fig. 10.22  Normal ultrasound appearance of the duodenum and proximal small bowel in an infant. (a) Transverse grayscale ultrasound image demonstrates the third portion of the duodenum (arrow) coursing between

the superior mesenteric artery (arrowhead) and the aorta (A). (b) Sagittal grayscale ultrasound image of the left flank shows normal, collapsed proximal small bowel loops (arrow)

Congenital Anomalies

additional areas of intestinal obstruction. Postoperative complications include a leak at the anastomosis and persistent narrowing with delayed passage of ingested liquids across the repair site. Duodenal stenosis is relatively rare and may not be diagnosed until later in childhood depending on the degree of narrowing. Duodenal web is a result of incomplete recanalization between the eighth and tenth weeks of gestation resulting in either a complete obstruction or a perforated ­diaphragm. The second portion of the duodenum is the most common location, distal to the ampulla. Additional abnormalities described in patients with duodenal atresia and stenosis include malrotation and a preduodenal portal vein [110]. Associated anomalies in patients with a duodenal web include malrotation and trisomy 21 [111]. Infants with a complete web will present with duodenal obstruction and bilious emesis soon after birth, while those with a fenestrated web may present later in life with recurrent episodes of bilious emesis, abdominal distention, and failure to thrive. Ultrasound diagnosis of duodenal stenosis and duodenal web can be made if the stomach is filled with fluid. Luminal narrowing (stenosis) or an obstructing intraluminal membrane (web) with a dilated proximal duodenum proximal to the narrowed area will be demonstrated (Fig.  10.24). Imaging of a stenosis can mimic the “double bubble” sign on plain abdominal radiographs although distal gas is often present, depending on the degree of stenosis. Upper GI studies of duodenal stenosis will show an abrupt duodenal narrowing distal to a dilated bulb with small amounts of contrast identified beyond the stenosis. A web appears as a faint radiolucent line outlined by barium. Over time, the web elongates as a result of continual peristalsis, resulting in a wind sock configuration of an intraluminal duodenal diverticulum [112]. The role of CT in the evaluation of the duodenum in children is limited. Both duodenal stenosis and web are treated surgically. There are also published reports of successful endoscopic balloon dilation in children with these abnormalities [113, 114].

 uodenal Atresia, Stenosis, and Web D Duodenal atresia is a congenital obstruction that usually occurs distal to the ampulla of Vater due to a failure of recanalization of the duodenum during the eighth to tenth weeks of gestation. Of all potential causes for congenital duodenal obstruction, the majority are due to duodenal atresia, although annular pancreas, duodenal stenosis, and duodenal web may also cause partial obstruction. The diagnosis of duodenal atresia is often made on prenatal imaging and is one of the most common causes of fetal bowel obstruction. Duodenal atresia occurs in 1 in 2500–5000 births with a 3% prevalence in patients with trisomy 21. About 30% of patients with duodenal atresia have trisomy 21, and there is also an association with VACTERL (vertebral, anorectal, cardiac, tracheoesophageal, renal, and limb anomalies) [108]. Infants with duodenal atresia present with bilious emesis soon after birth or after the first feeding. On prenatal ultrasound, a “double bubble” sign and polyhydramnios can be seen, representing the fluid-filled, distended stomach and proximal duodenum. Initial radiographs show the classic “double bubble” sign of the air-filled, distended stomach and proximal duodenum. Often there is no air distal to the double bubble. Air injected through an enteric tube provides excellent contrast for evaluation by abdominal radiographs which are often all that is needed to make the diagnosis. Ultrasound can demonstrate the fluid-filled stomach and level of obstruction of the dilated duodenum (Fig.  10.23). Ultrasound can also assess for possible associated malrotation and extrinsic compression from an annular pancreas that can partly or completely surround the second portion of the duodenum [109]. When duodenal atresia is located between two bile duct orifices, a rare anomaly, gas may be seen distal to the dilated proximal duodenum [108]. Duodenal atresia is treated surgically by duodeno-duodenostomy or duodeno-jejunostomy with operative evaluation for

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b

a

Fig. 10.23  Duodenal atresia in a newborn infant. (a) Transverse grayscale ultrasound image of the epigastric region shows dilation (arrow) of the duodenum proximal to the atresia. (b) Abdominal radiograph

a

demonstrates a typical “double bubble” appearance with a dilated duodenum (arrow) proximal to the site of atresia

b

Fig. 10.24  Duodenal web in a 3-year-old male with failure to thrive. (a) Transverse grayscale ultrasound image shows a web (arrows) narrowing the lumen of the proximal duodenum. (b) UGI series image

with patient in a right lateral position reveals circumferential narrowing (arrow) caused by the web with dilation (asterisk) of the proximal duodenum

Intestinal Atresia The prevalence of jejunoileal atresia is 1–3 per 10,000 live births and is weakly associated with cystic fibrosis, malrotation, and gastroschisis. It is thought to occur as a consequence of intra-uterine mesenteric vascular accidents, possibly due to volvulus or bowel incarceration in utero. The different types of intestinal atresia include septal “web” atresia, blind-ending atresia, mesenteric gap atresia, and apple peel atresia, as well as multiple atresias. The most common type is blind-ending atresia. The incidence of multiple bowel atresias is 15%. After the duodenum, the ileum is the most common site of involvement. Bowel atresia associated with gastroschisis (5–15% of cases) is a poor prognostic indicator [115]. The

rare “apple peel” form of atresia occurs when the distal small bowel wraps around its vascular supply, resembling an apple peel, and affects the duodenum and proximal jejunum. This form of atresia may have a genetic component [116]. Small bowel atresia is often detected prenatally with dilated bowel and polyhydramnios. Patients present soon after birth with bilious emesis, abdominal distention, and failure to pass meconium. Prenatal ultrasound may show dilated, fluid-filled proximal bowel loops and evidence of in utero perforation as well as polyhydramnios. Postnatally, a diagnosis of intestinal atresia is usually made on plain radiographs. Ultrasound findings include dilated proximal, blind-ending bowel with no gas in

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the decompressed distal bowel. A small bowel “whirlpool” sign located in the mid-abdomen and right lower quadrant unrelated to midgut volvulus has been described with apple peel atresia. This sign has been shown to better depict the cause of obstruction when compared to barium studies [117]. Plain films will show dilated bowel loops proximal to the atretic segment and an absence of distal gas. A “triple bubble” appearance is seen with jejunal atresia that is equivalent to the “double bubble” sign of duodenal atresia, with the third bubble representing proximal jejunal dilation. Peritoneal calcifications related to in utero perforation may be seen (Fig. 10.25). a

Contrast enema is performed to exclude additional sites of atresia and associated malrotation. An unused microcolon will be present with both jejunal and ileal atresia [22]. Treatment for bowel atresia is surgical. Apple peel atresia, previously associated with a poor outcome, more recently has a reported excellent long-term outcome although postoperative complications occur in the majority of patients [118].

J ejunal and Ileal Stenosis Jejunal stenosis is a narrowing of the jejunum without disruption in continuity or defect in the adjacent mesentery. Stenoses b

L

c

d

Fig. 10.25  Newborn infant with jejunal atresia. (a) Transverse grayscale ultrasound image demonstrates dilated proximal small bowel (arrow) with collapsed distal bowel loops. (b) Sagittal right upper quadrant grayscale ultrasound image reveals peritoneal calcifications (arrows) overly-

ing the surface of the liver (L). (c) Abdominal radiograph identifies dilated proximal small bowel (black arrow) and peritoneal calcifications (white arrow). (d) Contrast enema shows a microcolon and dilated, gasfilled bowel loops (arrow) proximal to the atretic jejunum

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of the bowel are a relatively rare cause of neonatal obstruction, accounting for approximately 5–11% of all jejunoileal obstructions [119]. At the stenotic site, there is often a short, narrow segment with a minute lumen where the muscularis is irregular and the submucosa is thickened. Occasionally, there is an obstructing membrane [120]. The resultant intestinal obstruction is incomplete. Clinically, there may be a history of maternal polyhydramnios, and postnatally infants may present with bilious emesis and abdominal distention. Often there is a failure to pass meconium. With incomplete obstruction, diagnosis may be delayed. A diagnosis of jejunal or ilieal stenosis is generally made on plain radiographs or on small bowel follow-through examinations that reveal proximally dilated loops with delayed passage of contrast and normal caliber loops beyond the stenosis. Ultrasound will show dilated loops proximal to the site of stenosis. Treatment is surgical with either limited intestinal resection or longitudinal incision with resection of the stenotic segment.

Midgut Malrotation Midgut malrotation refers to any deviation from the normal 270-degree counterclockwise rotation of the midgut during development and presents clinically in approximately 1  in 2500 live born infants less than 1 year of age. Anatomically it is much more common, occurring in 0.2%–1% of the normal population [121]. Malrotation involves malpositioning of the bowel with abnormal fixation. The normally broad mesenteric attachment is foreshortened, predisposing to midgut volvulus. Ladd bands are fibrous peritoneal bands that attach the malrotated cecum in the right upper quadrant to the retroperitoneum and extend over the second portion of the duodenum where they may result in extrinsic compression or obstruction (Fig.  10.26). The most severe complication of malrotation is midgut volvulus where the mesenteric base twists around the superior mesenteric artery (SMA), obstructing the bowel and compromising gut perfusion, a surgical emergency.

Stomach

Duodenum

Ladd bands Cecum

Small intestine

Intestinal

Midgut

malrotation

volvulus

a Fig. 10.26  Diagrams of intestinal malrotation and volvulus. (a) In intestinal malrotation, there is a short mesenteric attachment. Ladd bands attach the malrotated cecum in the right upper quadrant to the retroperitoneum.

b The mesenteric base is predisposed to twist around the superior mesenteric artery. (b) When midgut volvulus occurs and the mesenteric base twists around the superior mesenteric artery, gut perfusion is compromised

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Intestinal nonrotation is a subtype of malrotation in which the small bowel is mainly located in the right hemiabdomen and the cecum in the left hemiabdomen. The risk of volvulus is much lower in complete nonrotation because patients have the effective anatomy of someone who has undergone a Ladd procedure. Reversed rotation occurs when a 90-degree ­clockwise rotation of the bowel occurs during development rather than the normal 270-degree counterclockwise rotation. The duodenum passes in front of the superior mesenteric artery, and the colon lies in front of the mesentery [121]. Patients born with omphalocele, gastroschisis, and congenital diaphragmatic hernias will have bowel malrotation. It also frequently occurs in the setting of heterotaxy (30–90% of patients), and is associated with bowel atresia, annual pancreas, and Hirschsprung disease [122, 123]. More than half of affected individuals will present in the first month of life with midgut volvulus and bilious emesis. Some patients have more indolent symptoms resulting in chronic volvulus with a delayed diagnosis [124]. Malrotation results in an abnormal position of the SMV and the SMA, with the SMV located anterior to, or to the left of the SMA rather than in normal position to the right of the artery (Fig. 10.27). With midgut volvulus, a dilated proximal

a

Fig. 10.27  Relationship of the superior mesenteric artery (SMA) to the superior mesenteric vein (SMV). (a) Transverse grayscale ultrasound image depicts the SMV (arrow) normally positioned anterior and

duodenum is seen tapering at the site where the SMV twists around the SMA, the so-called “whirlpool” sign (Fig. 10.28). This sign has a reported 87% sensitivity for the detection of midgut volvulus [125]. Recently, the “whirlpool” sign has been described in neonates with congenital intestinal obstruction unrelated to midgut malrotation, related instead to segmental volvulus of the small intestine or coiled distal small intestine associated with apple peel atresia [117]. Although these ultrasound findings are valuable, their absence does not completely exclude malrotation or volvulus, and an UGI series remains the reference standard for diagnosis. Ultrasound documentation of a normal position of the third portion of the duodenum posterior to the SMA and anterior to the aorta has been shown to exclude bowel malrotation [126]. CT can also document the retro-mesenteric, normal position of the third portion of the duodenum, although it is not the imaging modality of choice in young children. The obstructed bowel proximal to a volvulus and the “whirlpool” sign can also be seen on CT. Once diagnosed, malrotation with midgut volvulus is treated with emergent surgery (Fig.  10.29). Malrotation without associated volvulus is treated surgically on a non-

b

to the right of the SMA (arrowhead). (b) Transverse grayscale ultrasound image depicts the SMV (arrow) abnormally positioned anterior and to the left of the SMA (arrowhead)

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Fig. 10.28  Midgut volvulus in a 2-week-old neonate presenting with bilious emesis. (a) Transverse grayscale ultrasound image demonstrates a dilated, fluid-filled stomach (S) and dilated third portion of the duodenum (arrow) ending in a narrowed beak. (b) Transverse color Doppler

ultrasound image of the duodenum shows a “whirlpool” sign with the superior mesenteric vein (arrow) and mesentery wrapped around the superior mesenteric artery (arrowhead). (c) UGI series image reveals a beak (arrow) at the site of obstruction caused by the volvulus

emergent basis with the Ladd procedure, where the abnormal peritoneal bands are released, and the appendix is removed.

sated secretions from the exocrine glands in CF result in abnormal meconium [127]. Meconium ileus typically presents in the neonate as a distal small bowel obstruction that responds to contrast enema with resolution of the obstruction in 39% [128]. Meconium ileus can be associated with bowel atresia, necrosis, and perforation. Perforation can occur in utero, leading to extrusion of meconium and digestive enzymes into the peritoneal cavity resulting in an intense chemical peritonitis followed by peritoneal calcification. In utero imaging will show polyhydramnios, ascites, and matted echogenic bowel. There may be a focal mass and intraperitoneal calcification if perforation has occurred. Postnatal

Meconium Ileus Meconium ileus occurs when the distal ileum is obstructed by tenacious meconium. Meconium ileus presents soon after birth with abdominal distention, bilious emesis, and delayed passage of meconium. It can be suspected on prenatal ultrasound when intestinal obstruction is seen in association with echogenic bowel. Approximately 20% of infants with cystic fibrosis (CF) present with meconium ileus, many of whom have the dF508 mutation on amniocentesis. The thick, inspis-

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ultrasound imaging shows the dilated small bowel loops, ascites, echogenic meconium and extraluminal calcifications. Plain films in the neonate may show proximally dilated loops, absent air-fluid levels on decubitus or upright imaging, and a “bubbly” pattern of distended intestinal loops (Fig. 10.30). Calcifications and mass effect from a meconium pseudocyst may be identified on plain films although ultrasound can detect more subtle extraluminal calcification. A meconium pseudocyst frequently manifests as a calcified soft tissue mass on plain films, and as a mass with peripheral calcification with color Doppler twinkling artifact and heterogeneous content on ultrasound [129]. Ultrasound of meconium ileus shows bowel filled with echogenic, thick meconium proximal to a microcolon, while ileal atresia will demonstrate dilated loops of bowel filled with air and fluid proximal to a microcolon. Both disorders are associated with a microcolon on contrast enema. A diagnostic contrast enema is typically carried out to the level of obstruction in the setting of atresia. With meconium ileus, contrast enema with water-soluble material is both diagnostic and therapeutic. Non-operative management for simple meconium ileus includes repeated attempts to dissolve the thick meconium by water-soluble enema. Surgery is required for persistent bowel obstruction, volvulus, and/or perforation [129].

Fig. 10.29  Diagram of surgical release of Ladd bands in the setting of malrotation with volvulus

Fig. 10.30  Newborn male with meconium ileus. (a) Sagittal grayscale ultrasound image of the left lower quadrant shows echogenic content within a collapsed microcolon (arrow) with dilated proximal bowel

 econium Peritonitis and Pseudocyst M Meconium peritonitis follows in utero bowel perforation, leading to leakage of meconium into the peritoneal cavity and a sterile, chemical inflammatory response. A meconium cyst develops when the intraperitoneal meconium is contained by fibrous adhesions. Bowel loops can become

loops (arrowhead). (b) Supine abdominal radiograph demonstrates dilated proximal bowel loops due to meconium ileus

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entrapped within the cyst, and mural calcification often occurs. Bowel perforation can result from in utero volvulus, bowel atresia, vascular accidents, and meconium ileus. In one study, only 8% of patients with meconium peritonitis had underlying cystic fibrosis [129]. A morbidity rate of 34% and a mortality rate of 2% have been reported for infants with meconium peritonitis [130]. Prenatal ultrasound imaging commonly shows fetal ascites and dilated bowel. Infants may present with intestinal obstruction and pneumoperitoneum. A meconium pseudocyst can present as a distended abdomen. Plain films may show diffuse peritoneal calcifications. Postnatal ultrasound imaging can show punctate echogenic peritoneal calcifications, subtle free air, dilated small bowel loops, and complicated ascites as well as the calcified mass of a meconium pseudo-

a

c

Fig. 10.31  Meconium pseudocyst in a newborn infant with calcifications seen prenatally suspicious for in utero perforation. (a) Transverse grayscale ultrasound image shows a soft tissue mass (arrows) with internal calcifications in the mid-abdomen. (b) Transverse color Doppler ultrasound image of the meconium pseudocyst demonstrates peripheral flow

cyst with heterogeneous contents (Fig. 10.31). Dilated loops from an obstruction may be present as well. Subtle calcifications not seen on plain film can be detected by ultrasound. For complex meconium ileus associated with bowel atresia, necrosis and perforation, surgical intervention is mandatory [129].

Acquired Obstruction Intussusception Small Bowel Intussusception Small bowel intussusception occurs when a segment of bowel (the intussusceptum) telescopes into a distal segment (the intus-

b

d

(arrow) with no internal perfusion. (c) Sagittal grayscale ultrasound image of the right upper quadrant reveals subtle calcification (arrow) along the liver surface related to in utero bowel perforation. (d) Supine abdominal radiograph does not reveal the hepatic calcification or the meconium pseudocyst

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suscipiens), and is a common etiology of acute abdominal pain. Small bowel intussusception differs from the more common ileocolic intussusception as it is frequently an incidental, transient finding on ultrasound. A small bowel intussusception can persist when it occurs in association with a lead point such as a Meckel diverticulum, polyp, or duplication cyst [131]. Symptomatic small bowel intussusception occurs in the setting of Henoch–Schönlein purpura, celiac disease, Peutz– Jeghers syndrome with small bowel polyps, and indwelling gastrojejunal feeding tubes. Small bowel intussusception is also a known complication after abdominal surgery, responsible for 5–15% of all postoperative bowel obstruction [132]. Non-transient, symptomatic small bowel intussusception can present with intermittent abdominal pain, vomiting, GI tract bleeding, and occasionally as a palpable mass. a

Ultrasound is the imaging modality of choice for all types of intussusception, with high sensitivity and specificity as well as high negative predictive values, showing a “doughnut” or “pseudo-kidney” sign of alternating bowel layers with internal echogenic mesenteric fat and nodes. The sensitivity for diagnosing intussusception by ultrasound is reported as 98% with a specificity of 98% [133]. A transient intussusception is usually asymptomatic, and has been shown in several studies to be smaller than an ileocolic intussusception, with a maximum diameter of less than 3.5 cm, with normal bowel wall thickness and no associated dilated bowel loops (Fig. 10.32). Small bowel intussusceptions with pathologic lead points are typically larger (Fig. 10.33). Mean fat core diameter, the ratio of inner fat core diameter to outer wall thickness, and the presence of lymph nodes

b

Fig. 10.32  Transient small bowel intussusception found incidentally in two different patients. (a) Transverse grayscale ultrasound image shows a small diameter (arrow) small bowel intussusception that resolved dur-

a

Fig. 10.33  Non-transient small bowel intussusception due to a polyp in a 4-year-old male with abdominal pain. (a) Longitudinal grayscale ultrasound image shows a small bowel intussusception (arrows).

ing the study. (b) Axial contrast-enhanced CT image demonstrates a transient small bowel intussusception (arrow) in a child with no GI symptoms

b

(b) Coronal contrast-enhanced CT image identifies the extensive small bowel intussusception (arrows) caused by a small bowel polyp identified at surgery

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have also been suggested as ways of differentiating small bowel from large bowel intussusception [131, 134]. In postoperative patients, plain films may show a small bowel obstruction. In the past, ultrasound was not thought to be reliable for the diagnosis of postoperative small bowel intussusception. However, a recent series found ultrasound to be highly accurate [135]. CT also will show the site of a nontransient intussusception and the level of bowel obstruction in those cases where the diagnosis cannot be made by ultrasound or plain film. Barium studies are not typically useful. Patients with non-transient small bowel intussusception and an identifiable lead point are treated surgically. Management of non-transient small bowel intussusception includes short-term observation to ensure resolution, or careful follow-up to confirm spontaneous reduction [136]. Ileocolic Intussusception Ileocolic intussusception is an invagination of proximal bowel (the intussusceptum) into more distal bowel (the intussuscipiens) which occurs mainly due to hyperplasia of Peyer patches in the terminal ileum that act as a lead point (Fig.  10.34). Ileocolic intussusception is the most common abdominal emergency in infancy and early childhood with approximately two-thirds presenting in the first year of life. Infants less than 3 months of age are relatively spared [137]. More than 50% of cases occur in children under 1 year of age, and 80–90% under 2  years of age [138, 139]. An underlying lead point is less common, found in about 25% of patients, such as a duplication cyst, Meckel diverticulum, or lymphoma. Cases of ileocolic intussusception associated with a lead point tend to occur in older children. Following reduction, the recurrence rate is from 8 to 15%, which should always raise the question of a pathologic lead point. Intussusception of the appendix can occur in isolation or as part of an ileocolic intussusception. The appendix is the lead point in about 0.2% of all cases of ileocolic intussusception [140]. Isolated appendiceal intussusception does occur in children, and the majority of them will be inflamed [141]. The typical clinical presentation for idiopathic intussusception is a child with irritability, intermittent abdominal pain, emesis, and bloody stools. “Currant jelly” stool, a result of sloughed mucosa, blood, and mucus, occurs in a minority of patients. Ultrasound is the imaging modality of choice for the diagnosis or exclusion of intussusception, with a sensitivity approaching 100% and a specificity of 88–100%. Ultrasound features include a mass with concentric alternating hypo- and hyperechoic rings of bowel resulting in a “doughnut” or target-like appearance on axial images and a “pseudokidney” on longitudinal images. Internal echogenic mesenteric fat and nodes are usually identified near the base of an intussusception. The absence of blood flow on ultrasound suggests bowel

a Colon

Intussuscipiens

Intussusceptum

Ileum

Cecum

b Colon

Intussusceptum

Ileocecal valve

Constricted blood supply

Cecum Ileum

Appendix

Fig. 10.34  Diagrams of ileocolic intussusception. (a) There is invagination of the terminal ileum (the intussusceptum) into the cecum and ascending colon (the intussuscipiens) (b) The blood supply to the invaginated ileum is constricted and may become compromised if the obstruction is not relieved in a timely fashion

ischemia and the presence of interloop fluid correlates significantly with ischemia and irreducibility (Fig. 10.35) [142]. A false-positive diagnosis of intussusception can occasionally be made in other conditions that cause bowel wall

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b

Fig. 10.35  Ileocolic intussusception in two separate patients. (a) Trans­ verse grayscale ultrasound image of the right lower quadrant in an 18-month-old female with abdominal pain shows bulky mesenteric nodes (arrowhead) adjacent to an ileocolic intussusception (arrow). (b)

Longitudinal color Doppler ultrasound image of the right lower quadrant in a 2-year-old male with bloody diarrhea and lethargy shows an ileocolic intussusception with interloop fluid (arrow). Bowel perfusion is preserved

thickening, such as Henoch–Schönlein purpura. Plain films are often nondiagnostic, although occasionally a mass is identified in the right mid- or upper abdomen with decreased bowel gas in the right lower quadrant. Dilated small bowel due to early obstruction can also be seen. In the absence of peritonitis, bowel perforation, or shock, pressure-monitored reduction is the first line of treatment for ileocolic intussusception which can be performed fluoroscopically or with ultrasound, using liquid or air. The success rate of air enema is approximately 83% compared to 70% for liquid enema reduction [143]. Delayed repeat air enema in a clinically stable patient is an option for an initially irreducible intussusception located at the ileocecal valve, with a 90% reported success rate [142]. Those intussusceptions that cannot be reduced are surgically treated [144].

affected each year. Campylobacter is present in the gastrointestinal tracts of poultry, cattle, swine, and sheep as well as in dogs and cats. Disease transmission is usually food-borne through undercooked meat or contaminated dairy products, although contaminated water and ice can also spread the disease. The incubation period is typically 2–5 days, although it can be longer. Viral gastroenteritis is even more common than bacterial gastroenteritis, and according to the Centers for Disease Control accounts for more than 200,000 deaths of children worldwide per year [146]. Viral gastroenteritis commonly causes outbreaks of enteritis on cruise ships, in daycare centers, and schools that are usually self-limited and resolve in 1–3  days. Transmission is often via the fecal–oral route. Enteric viruses such as rotavirus and norovirus are leading causes of gastroenteritis worldwide. Vaccines against rotavirus were implemented in 95 countries in 2018 [147]. On ultrasound, viral gastroenteritis may demonstrate prominent lymph nodes and ascites. The bowel wall is not usually thickened. Rarely, pneumatosis can be seen in infants and children infected with rotavirus [148]. Thickening of the terminal ileum and cecum occurs with bacterial enteritis. Lymphoid hyperplasia with thickening of the terminal ileum and mesenteric lymph node enlargement occur with Yersinia and Salmonella infection. Ascariasis infestation is clearly shown when mobile worms are found within the lumen of bowel, and the echogenic, well-developed digestive tract of the worm can also be imaged [149]. The sites of involvement in patients with enteritis is a key differentiating feature on both ultrasound and CT. Parasitic infections such as Giardia and Strongyloides involve the proximal small bowel while bacterial infections such as Salmonella, Shigella, and Yersinia affect the distal small bowel (Table 10.2) [150].

Small Bowel Wall Thickening Infectious Enteritis Gastroenteritis is defined as three or more loose or watery stools in 24 hours, with or without vomiting, fever, or abdominal pain. Bacterial enterocolitis in children can be caused by a variety of organisms, including Shigella, Salmonella, Escherichia coli, Yersinia, and Campylobacter. An estimated 211–375 million episodes of diarrheal illness occur each year in the United States, many related to food-borne illness. In 2011, the incidence of Salmonella infections in the United States was 1645 per 100,000 people [145]. Patients with sickle cell disease are at risk for Salmonella infection due to splenic hypofunction, with associated high morbidity and mortality rates. Campylobacter is one of the leading causes of bacterial enterocolitis in the world, with an estimated 1.3 million patients in the United States

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10  The Gastrointestinal Tract Table 10.2  Typical bowel involvement of common infectious organisms Bowel segment Proximal small bowel Distal small bowel Distal ileum and cecum Ascending colon Cecum and ascending colon Descending colon Pancolitis

Organism Giardia, Strongyloides Salmonella, Yersinia, Shigella TB Yersinia, Salmonella Campylobacter Shigella Clostridium difficile, CMV, Escherichia coli

TB, Tuberculosis; CMV, cytomegalovirus

Most cases of bacterial gastroenteritis are self-limited and do not require stool cultures or antimicrobial therapy. Treatment is supportive, with replacement of fluid and electrolytes. Stool cultures are only indicated for patients with severe or prolonged diarrhea, bloody diarrhea, presence of stool leukocytes, lactoferrin, or occult blood. Treatment for viral gastroenteritis is also symptomatic, with the goal of maintaining hydration.

Crohn Disease Inflammatory bowel disease (IBD) represents a chronic inflammatory disease of the gastrointestinal tract that typically manifests as episodes of relapsing inflammation. There is a peak onset between 15 and 30 years of age. Inflammatory bowel disease includes Crohn disease (CD), ulcerative colitis (UC), atypical UC, and IBD-unclassified [151]. Approximately 25% of cases of IBD present before the age of 18 years, and the incidence in children is increasing globally in both developed and developing nations [152]. Pediatric-onset IBD often has atypical features, making classification more difficult. The upper GI tract is more affected by IBD in children than in adults, and can occur with both CD and UC. Crohn’s disease is characterized by transmural inflammation of bowel, skip lesions, and symptoms that wax and wane. It is usually progressive, with half of those affected experiencing complications such as fistulas and strictures. Patients with a childhood onset of CD usually have more progressive and extensive disease than those that with onset of the disease in adulthood. Colonic involvement is frequent in pediatric CD, especially the left colon. With early-onset CD in children less than 5  years of age, there may be isolated colonic disease [153]. Diagnosis of IBD can be challenging with patients often experiencing atypical symptoms of diarrhea, rectal bleeding, and abdominal pain as well as extra-intestinal symptoms such as unexplained fever, arthritis, and chronic anemia. Detection of disease activity is important for early institution of biologic therapy. The reference standard for assessing response to therapy is endoscopy, an invasive procedure. Transabdominal ultrasound is highly effective for detecting inflammation due to Crohn’s disease and can be used both as

the initial study and for follow-up, which is ideal for children due to its lower cost and lack of radiation when compared to MR and CT enterography. The ultrasound examination should begin in the ileocecal region, given the predilection for involvement of the terminal ileum. High-frequency transducers are used to evaluate focal regions of interest, while lower frequency transducers are used in the assessment of deep fluid collections, optimizing settings for high contrast and low flow on Doppler settings. In experienced hands, perianal ultrasound can be used to assess abscesses and fistulas [154]. Detecting active disease can be clinically challenging, as many patients are asymptomatic despite recurrent disease. Bowel wall thickness is important for assessing disease activity as is color Doppler. Bowel wall thickening (greater than 2.5 mm for small bowel) and loss of normal bowel wall stratification are identified. With active disease, segments of bowel are hyperemic, non-compressible, greater than 4–5 mm in thickness, and demonstrate decreased peristalsis (Fig. 10.36). Thick­ ened loops with more than 2 vessels per square cm on color Doppler are strongly associated with active disease [155]. Superior mesenteric arterial flow velocities are elevated in patients with active disease. The mesentery may be thickened and echogenic, corresponding to the creeping fat seen by CT. Mesenteric nodes are commonly enlarged and hyperemic. Contrast-enhanced ultrasound (CEUS) is a relatively new technique that in adult patients has been shown to provide both subjective and objective information about bowel wall and mesenteric blood flow that is useful in determining disease activity in patients with IBD [156]. Shear wave elastography has also been used to measure bowel stiffness, and together with CEUS can distinguish between inflammatory and fibrostenotic bowel [157]. To date, there have been only a few descriptions of the use of either CEUS or shear wave elastography in the evaluation of IBD in children [158, 159]. On ultrasound evaluation, strictures appear as thickened bowel with luminal narrowing and more proximal dilated bowel. The sensitivity of ultrasound in detecting strictures varies between 60 and 85% [160]. Barium studies are less sensitive than CT and MR enterography for the detection of IBD. MR enterography is the noninvasive technique with the highest diagnostic accuracy for evaluation of disease activity in children and adults [161, 162]. However, its use is more limited in younger children who require sedation. The goal of treatment is to achieve mucosal healing which is associated with improved clinical outcome. Biologic treatment with anti-tumor necrosis factor agents such as infliximab and adalimumab, the most potent drug class to induce and lead to maintained mucosal healing, has benefited a large portion of patient’s with CD of all ages [163]. When given within 3 months of diagnosis, early biological treatment is associated with significantly improved outcomes [164].

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Fig. 10.36  Active Crohn disease in a 16-year-old female with fistula formation and secondary abscess. (a) Transverse color Doppler ultrasound image of the right lower quadrant demonstrates wall thickening and hyperemia (arrow) of the terminal ileum with adjacent fatty proliferation (arrowhead). (b) Transverse extended field of view grayscale ultrasound image of the right lower quadrant shows the substantial thickening (arrows) of the distal ileum. (c) Transverse grayscale ultrasound image of the right lower quadrant depicts a fistula (white arrow) between the abscess (arrowhead) and the diseased distal ileum (black

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arrow). (d) Longitudinal color Doppler ultrasound image reveals hyperemia surrounding the abscess (calipers) and the adjacent fistula (arrow). (e) Coronal contrast-enhanced CT image demonstrates a gas bubble (arrowhead) within the abscess, and loss of the fat planes (arrow) between the diseased ileal loops at the site of fistula formation. (f) Coronal T2-weighted, fat-suppressed magnetic resonance (MR) image depicts the diseased distal ileum (arrow) with adjacent fatty proliferation and an abscess (arrowhead) in the right lower quadrant

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Hemorrhage Trauma Duodenal hematoma in children is not uncommon, occurring in the setting of both accidental and non-accidental trauma, as well as a rare complication of endoscopic biopsy. Blunt hollow visceral injury in children in the United States ranges from 1% to 5% of cases of blunt pediatric abdominal trauma, arising from handlebar and seat belt injury as well as direct blows in the setting of non-accidental trauma [165]. Physical examination is usually suggestive of intestinal injury in the majority of patients who present with generalized tenderness and abdominal bruising. Bowel injury in non-accidental trauma is more frequent than in accidental trauma [166]. There are rare reports of jejunal hematomas resulting from blunt trauma. Intramural duodenal hematoma following upper GI endoscopy is uncommon, usually in patients with a bleeding diathesis [167]. In the setting of trauma and non-accidental trauma with suspected bowel injury, CT is the imaging examination of choice. A partial thickness tear of the bowel wall results in a hematoma, most often occurring in the duodenum. CT typically shows an eccentric mass extending into the bowel lumen which can cause partial proximal obstruction [168]. Acutely, the hematoma will have slightly increased attenuation becoming low attenuation with evolution. Ultrasound can be useful in the follow-up of a known hematoma to resolution, demonstrating circumferential or eccentric bowel wall thickening, sometimes with adjacent free fluid (Fig. 10.37).

a

Fig. 10.37  Duodenal hematoma in a 5-year-old female after duodenal biopsy at endoscopy. (a) Transverse grayscale ultrasound image of the mid-abdomen reveals marked distension of the duodenum (arrow) with

Duodenal hematoma is managed non-operatively with nasogastric tube suction, bowel rest, and parenteral nutrition [169]. Henoch–Schönlein Purpura Henoch–Schönlein purpura (HSP) is a multisystemic hypersensitivity-mediated small vessel vasculitis that affects children between 3 and 10 years of age and frequently involves the GI tract. It is the most common vasculitis in children. Patients present with colicky abdominal pain, vomiting, and melena. The purpuric rash is the earliest manifestation in most patients. About 75% of affected children will develop a transient arthritis of the large joints, and about 50% have GI tract involvement. Hematuria can also occur. There is intramural bowel hemorrhage that is confined to the mucosa and submucosa. About 5% of patients with HSP will develop complications related to bowel hemorrhage, including small bowel and ileo-colic intussusceptions, massive GI hemorrhage, ileal perforation, and stricture [170, 171]. Ultrasound manifestations of HSP include bowel wall thickening usually affecting the ileum, although the jejunum and sometimes the duodenum are involved (Fig.  10.38). Mesenteric adenopathy and ascites are often present. The wall thickening of HSP is a known ultrasound mimic of intussusception. However, secondary intussusception does occur in approximately 5% of patients with HSP and can be diagnosed by ultrasound [172]. Plain films may show focal bowel wall thickening. CT can depict multifocal, circumferential bowel wall thickening with a target pattern of enhancing mucosal and serosal layers, vascular engorgement of the mesentery and mesenteric adenopathy. Rare complications of massive hemor-

b

heterogeneous, echogenic material in keeping with blood clot. (b) Coronal contrast-enhanced CT image shows the blood-filled, dilated duodenum (arrow)

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Fig. 10.38  Henoch–Schönlein purpura in a 6-year-old male. Sagittal grayscale ultrasound images of the left lower quadrant (a) and midline (b) show circumferential wall thickening (arrows) of small bowel with

moderate ascites (arrowhead). B, Bladder (c) Sagittal color Doppler ultrasound image reveals bowel wall hyperemia (arrow). The appearance of the bowel loops mimics an intussusception

rhage, ileal perforation, and stricture can also be readily diagnosed [171]. The intramural hemorrhages of HSP will resolve spontaneously with conservative management in most patients. Steroids are used in uncomplicated cases. Ultrasound can be useful in documenting resolution of bowel wall involvement.

caused by a hypersensitivity to certain foods or other unknown allergens. A family history of allergic disorders is often present. The prevalence of eosinophilic gastroenteritis in the United States is approximately 25 per 100,000 and is most common in the northeastern United States and in urban areas [173]. Any portion of the GI tract can be involved, although the gastric antrum and the proximal small bowel are almost always affected. Three subtypes have been described: mucosal, muscular, and serosal. In the mucosal form of disease, there is focal or diffuse mucosal fold thickening, as well as polyps, ulcerations, and luminal narrowing. Mucosal involvement can lead to protein-losing enteropathy. The muscular

Eosinophilic Gastroenteritis Eosinophilic gastroenteritis is an uncommon disorder characterized by the triad of eosinophilic infiltration of portions of the GI tract, disordered GI function, and peripheral eosinophilia. The etiology is unknown. Some cases may be

10  The Gastrointestinal Tract

form manifests as bowel wall stenosis or obstruction, rigidity, and dysmotility. The presence of ascites is regarded as the main feature of the serosal pattern. Given that multiple layers of the bowel wall can be involved in eosinophilic gastroenteritis, multiple abnormalities often coexist. Symptoms vary with the site and type of involvement. The stomach and small bowel are most commonly affected, causing abdominal pain, bloody diarrhea, and rectal bleeding. The disease often has a chronic and relapsing course. Allergic disorders, including asthma and eczema, and food intolerances are present in 45–63% of reported cases [174]. Peritoneal fluid shows a predominance of eosinophilic white blood cells. Endoscopic findings include friable mucosa, ulcers, and polyps. Ultrasound features include thickening of the mucosal folds and intestinal wall, luminal narrowing, and ascites. The gastric findings of eosinophilic gastroenteritis are discussed earlier in this chapter. On CT, a “halo” sign and the “araneidlimb-like” sign have been described due to submucosal edema causing layering enhancement of the bowel wall and a spider-leg appearance. Pneumatosis is sometimes identified [175–177]. Treatment with corticosteroids is the mainstay of therapy. In patients with a chronic and relapsing course, additional long-term therapies may be required, including dietary restriction, and treatment with leukotriene inhibitors and azathioprine [174]. Ultrasound can be used to follow the response to therapy.

Lymphangiectasia Lymphangiectasia is a rarely encountered, chronic, debilitating condition that can occur anywhere in the body but most often affects the pulmonary and intestinal lymphatics. Intestinal lymphangiectasia (Waldmann disease) involves focal or diffuse dilation of the mucosal, submucosal, and subserosal lymphatics [178]. The diffuse, widespread form has a reported association with Noonan and Turner syndromes and trisomy 21 [179]. Lymphangiectasia is usually diagnosed before the third year of life. Common symptoms of primary intestinal lymphangiectasia include persistent diarrhea, peripheral edema, hypoproteinemia, and steatorrhea. Ultrasound demonstrates segmental or diffuse bowel wall thickening and mesenteric edema (Fig.  10.39). MR lymphangiography will show dilated central lymphatics. Treatment is symptomatic with a low-fat diet of mediumchain triglycerides, steroids, and albumin infusions. The prognosis is good for infants presenting after the neonatal period. Octreotide, an analogue of somatostatin, has been successful in treating more severe cases. A prospective study of sirolimus is currently underway [180].

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Fig. 10.39  Lymphangiectasia in a 22-year-old female. Sagittal grayscale ultrasound image of the right lower quadrant of the abdomen reveals marked, polypoid mural thickening of bowel loops which are separated by echogenic, edematous mesenteric fat

Cystic Fibrosis Cystic fibrosis (CF), an autosomal recessive disease, results from a defect in the cystic fibrosis transmembrane regulator (CFTR) which results in viscous secretions in multiple organ systems, most notably the lung and gastrointestinal tract. CF affects about 70,000 people worldwide. About 60% of individuals with CF are born with pancreatic exocrine insufficiency which progresses to affect about 90% of patients over time. GI manifestations of CF include bowel dysmotility which can manifest as meconium ileus in the neonate, constipation, small bowel bacterial overgrowth, and distal intestinal obstruction syndrome (DIOS). DIOS is defined as complete intestinal obstruction with bilious emesis and/or fluid levels in the small intestine on abdominal radiographs with a fecal mass at the ileocecal region and abdominal pain and/or distention [181]. DIOS affects between 10% and 20% of older children and adolescents with CF, with an increasing incidence with age. Once an individual has had an episode of DIOS, the recurrence risk is as high as 77% [182]. Chronic excess pancreatic enzyme replacement can result in a fibrosing colopathy with inflammation of the ileocecal region. The DIOS that occurs in older children results from thick mucus and undigested fecallike material that causes obstruction at the ileocecal region. Small intestinal bacterial overgrowth can result from the poor motility in patients with CF and presents with abdominal pain, distention, diarrhea, steatorrhea, anemia, and weight loss. On plain radiographs of the abdomen, DIOS appears as a bubbly, granular mass of stool in the right lower quadrant. While this appearance is useful in differentiating between con-

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stipation and distal intestinal obstruction in CF patients, it is not recommended as a standard diagnostic stool [181]. Ultrasound and CT can be used to confirm the diagnosis by demonstrating dilated loops of intestine with a fecal mass in the distal small bowel (Fig. 10.40). The wall of the cecum will appear thickened and there is usually pericecal fat stranding [183]. Chronic low-grade bowel obstruction in patients with CF is treated with a variety of approaches that include adequate hydration, osmotic laxatives such as polyethylene glycol, and strict adherence to pancreatic enzymatic replacement. Small intestinal bacterial overgrowth is treated with antibiotics and probiotics. Newer therapies using lubiprostone, a synthetic eicosanoid which activates the CLC2 chloride channel and enhancing fluid secretion into the gut, have become available as an adjunct to therapy in selected cases [184]. Installation of water-soluble contrast into the colon and ileum under fluoroscopic control has been found to reduce the need for surgical intervention.

Graft-Versus-Host Disease Graft-versus-host disease (GVHD) is an immunologic complication resulting from functionally competent donor T lymphocytes responding to foreign human leukocyte antigens (HLAs) expressed by recipient cells. GVHD is a common complication of hematopoietic stem cell transplantation with an incidence of up to 60% and affects the skin, GI tract, and hepatobiliary systems. GVHD can be acute, developing within a

the first 100  days after transplantation, or chronic. Acute GVHD can be life threatening, and accounts for almost half of posttransplantation deaths not related to recurrent tumors. The number of chronic GVHD cases is increasing with an incidence of about 40% in matched sibling donors and 70% with unrelated donors [185]. In the gastrointestinal tract, there is epithelial cell apoptosis that can lead to frank necrosis and sloughing of mucosa. The terminal ileum and colon are the predominant sites of involvement. Patients present with nonspecific symptoms of watery diarrhea, abdominal pain, GI bleeding, ileus, and protein-losing enteropathy. Early detection is important for optimizing outcome. The differential diagnosis includes infection and drug-related toxicity [186]. Ultrasound findings in the GI tract include fluid-filled and dilated bowel with an accentuated distinction between bowel wall layers, marked bowel wall thickening, and ascites (Fig. 10.41). Some bowel loops demonstrate hyperemia with color Doppler while others have decreased, high-resistance flow in the SMA which correlates with a poor outcome. Experimental studies have shown a damaged gut mucosal barrier in the walls of patients with GVHD [187]. CT imaging shows bowel wall thickening with a “target” sign due to low attenuation edema of the submucosal layer located between the markedly enhancing mucosal and serosal layers [188].

b

Fig. 10.40  Cystic fibrosis and distal intestinal obstruction syndrome (DIOS) in a 15-year-old male. (a) Supine abdominal radiograph shows several dilated upper abdominal bowel loops with a paucity of distal

bowel gas concerning for obstruction. (b) Longitudinal grayscale ultrasound image of the right lower quadrant of the abdomen shows multiple dilated, fecalized loops of small bowel

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a

b

c

Fig. 10.41  2-year-old male with graft-vs-host disease after bone marrow transplantation for treatment of leukemia presenting with abdominal pain. (a) Transverse grayscale ultrasound image of the right lower quadrant demonstrates two thick-walled loops of ileum surrounded by a small amount of

free fluid. (b) Longitudinal color Doppler ultrasound image of the right lower quadrant shows significant mural hyperemia of a distal ileal bowel loop. (c) Longitudinal power Doppler ultrasound image of the left lower quadrant reveals a thickened, hyperemic, and edematous mesentery (arrow)

Treatment for acute and chronic GVHD is complex, including improved conditioning regimens prior to transplantation. The aim is to achieve immune reconstitution in order to prevent disease relapse. Corticosteroids are used for initial treatment followed by targeted therapies.

fibrous band. A Meckel diverticulum can vary in  location, with approximately 75% found within 100 cm of the ileocecal valve, arising from the antimesenteric border of the distal small bowel [189]. About 60% contain ectopic gastric mucosa with hemorrhage the most common complication in children, with a reported incidence of up to 55%. Additional possible complications include bowel obstruction from a Meckel band, small bowel intussusception with the diverticulum serving as the lead point, and umbilical discharge [190]. Painless bright red blood per rectum is the most common complication, and bleeding can be massive. Acute Meckel diverticulitis is less common and presents in a fashion similar to acute appendicitis. Rarely, a carcinoid tumor can arise in a Meckel diverticulum.

Meckel Diverticulum Meckel diverticulum is the most common congenital anomaly of the GI tract. It is a remnant of the omphalomesenteric duct and is present in about 2% of the population. The duct typically obliterates in the first trimester of pregnancy. Failure of obliteration can lead to a diverticulum, fistula, or

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For suspected hemorrhage related to a Meckel diverticulum, technetium-99m pertechnetate scintigraphy is the imaging modality of choice. Simultaneous activity will appear in the stomach and in the ectopic gastric mucosa located within the diverticulum. Ultrasound plays a role in identifying complications related to a Meckel diverticulum, such as small bowel intussusception or obstruction caused by an omphalomesenteric band. Findings associated with Meckel diverticulitis may include a blind-ending tubular structure with mural thickening, and surrounding inflammation (Fig. 10.42) [106]. Meckel diverticulum is not often identified on ultrasound, barium studies, or CT [191]. The treatment for symptomatic Meckel diverticulum is surgical excision.

Benign Masses

Fig. 10.42  Meckel diverticulum in a 19-month-old female with a history of anemia and rectal bleeding. Transverse (a) and longitudinal (b) grayscale ultrasound images of the right lower quadrant of the abdomen show a short, thick-walled, blind-ending tubular structure (arrows) sur-

rounded by collapsed, matted loops of small bowel. (c) Coronal image from a Meckel scan demonstrates intense uptake in the right lower quadrant (arrow) that persisted at 30 minutes. The kinetics of this focus paralleled that of the gastric mucosa

Duplication Cyst Duplication cysts are congenital malformations of the bowel with an epithelial lining containing bowel mucosa, sharing a common wall with the bowel along it mesenteric border. Duplication cysts occur in 1 of 4500 births, and can be found anywhere along the gastrointestinal tract. They are cystic or tubular in shape. The majority do not communicate with the adjacent bowel lumen. One third of all duplication cysts are located in the ileum, the most common site. Ectopic gastric mucosa occurs in 20–30% which can lead to complications such as hemorrhage, and ectopic pancreatic tissue in 3%.

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Associated congenital anomalies, including spinal defects, cardiac, or urinary tract malformations, occur in 16–26% [70]. When located in the distal small bowel, a duplication cyst may serve as a lead point for intussusception, obstruct the distal small bowel, and bleed or perforate if it contains ectopic gastric mucosa. Duplication cysts are often asymptomatic and found incidentally on both prenatal and postnatal imaging. High-resolution ultrasound imaging can readily depict the 5 bowel wall layers of a duplication cyst (i.e., hyperechoic mucosa, hypoechoic muscularis mucosa, hyperechoic submucosa, hypoechoic muscularis propia, and outer hyperechoic serosa). However, a multilayered appearance can also be seen with a mesenteric cyst, abscess, and choledochal cyst [192]. The “Y” sign has been described which repre-

a

sents the splitting of the shared hypoechoic muscularis propria between the cyst and adjacent loop of bowel, a sign not described for other abdominal cysts. A subtle change in the shape and contour of the cyst can be noted, even in the absence of peristalsis of adjacent bowel, attributed to contraction of the muscular layer of the cyst. Echogenic debris and internal fluid levels can be seen when a duplication cyst is complicated by bleeding from ectopic gastric mucosa or infection (Fig. 10.43). While CT is not typically performed for diagnosis, a duplication cyst may be found incidentally. CT is also used in older patients to assess for associated complications. CT will show a c­ ystic mass with a thin, slightly enhancing outer wall. Protein­ aceous material may be seen within the lumen after bleeding. On MR imaging, cysts will be low in signal intensity on

b

c

Fig. 10.43  Duplication cyst of the distal ileum in a 2-month-old asymptomatic female with an abdominal lesion found prenatally. Transverse grayscale (a) and color Doppler (b) ultrasound images of the right lower

quadrant show the more medial portion of a large, bilobed distal ileal cyst (calipers, arrow) containing layering debris. (c) Transverse color Doppler ultrasound image reveals marked mural hyperemia

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T1-weighted images and high in intensity on T2-weighted images [70]. Surgical treatment of duplication cysts is necessary because of potential complications such as obstruction, intussusception, hemorrhage, and infection.

Mesenteric Cyst Mesenteric cysts arise from the small or large bowel mesentery as a proliferation of lymphatic tissue that does not communicate with the lymphatic system. They have a reported incidence of fewer than 1 per 100,000 hospital admissions for abdominal pain. A mesenteric cyst can occur anywhere along the mesentery and can also extend into the retroperitoneum, but are most commonly located in the ileal mesentery. They may present as

Fig. 10.44  Mesenteric cyst causing bowel obstruction in a 3-yearold male with abdominal pain and vomiting. (a) Transverse grayscale ultrasound image shows bowel (arrow) trapped within a large abdominal cyst (arrowheads) containing echogenic debris. (b) Axial contrast-

M. M. Munden and H. J. Paltiel

an abdominal mass or as an incidental finding on imaging. Bowel obstruction has been reported in infants with rare reports of intra-cystic bleeding and rupture [193]. Complications include torsion, volvulus, hemorrhage, and infection. On ultrasound, a mesenteric cyst can be unilocular or multiseptated, thin or thick-walled, and can contain internal echogenic debris (Fig. 10.44). The appearance is relatively nonspecific, as many other lesions, including lymphatic malformation, ovarian cyst, abscess, and meconium pseudocyst can have similar imaging features. CT typically shows low attenuation of the cystic lesion. While most mesenteric cysts are incidental findings, minimally invasive surgery is the treatment of choice when they are symptomatic.

enhanced CT image of the abdomen depicts the collapsed bowel loop (arrow) trapped within the large cystic lesion. (c) Surgical specimen of the resected mesenteric cyst

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Intestinal Polyp Intestinal polyps are epithelial or submucosal growths that protrude into the bowel lumen. The juvenile polyp is the most common polyp in children, and occurs within the colon. Numerous polyposis syndromes are associated with small bowel polyps. Peutz–Jeghers syndrome is the most common polyposis syndrome. The polyps are hamartomatous, and are not considered to be premalignant lesions. Juvenile polyposis syndrome is associated with small and large bowel hamartomatous polyps as well as gastric polyps, with a high risk of developing malignancy [194]. Small bowel polyps can serve as lead points for intussusception. Children with polyps often present with bleeding or pain. Small polyps can be identified on fluoroscopic contrast studies of the GI tract. On ultrasound, a polyp can occasionally be detected as the lead point of a small bowel intussusception (Fig. 10.45). Surveillance of patients predisposed to small bowel polyps is generally performed with CT enterography, MR enterography, and capsule endoscopy [195]. Small bowel polyps are removed either by endoscopy or by surgery. Vascular Anomalies Vascular anomalies are a biologically and morphologically diverse group of vascular channel abnormalities. Some vas-

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cular anomalies are comprised of a single vessel type such as a vein, artery, capillary, or lymphatic vessel, while more complex lesions can involve a combination of vessel types. Lesions may be solitary, multiple, or part of a multisystemic condition. The classification of vascular anomalies is based on a combination of endothelial characteristics, biological properties, and clinical behavior. According to the classification scheme of the International Society for the Study of Vascular Anomalies (ISSVA), vascular anomalies are broadly classified into two categories, tumors and malformations. These categories are further subdivided according to the vascular channels involved and other biological characteristics. Named entities with other associated anomalies are also included. Some vascular anomalies with features of both tumor and malformation remain provisionally unclassified [196]. Vascular anomalies involving the GI tract manifest clinically with four distinct patterns of signs and symptoms: (1) GI bleeding, overt or occult; (2) abdominal pain due to mass effect or intestinal obstruction; (3) abdominal distension, hepatomegaly, high-output cardiac failure due to arteriovenous shunting, for example, hepatic hemangioma, or arteriovenous fistula; and (4) diarrhea, edema, ascites, and hypoalbuminemia due to intestinal lymphangiectasia [196]. Infantile Hemangioma Infantile hemangioma is the most common benign tumor of infancy, occurring in 4–5% of term neonates, and as high as 23% in premature infants [197]. Infantile hemangioma affecting the bowel and mesentery is rare [198]. On ultrasound, hypoechoic tumor masses are identified in the wall of the small bowel and adjacent mesentery (Fig.  10.46). The ascending colon is occasionally involved as well. The SMA, SMV, and portal vein will appear dilated. Similar findings are shown by CT and MR imaging [198]. Patients are usually successfully treated with propranolol or corticosteroids.

Fig. 10.45  Polyp acting as lead point for small bowel intussusception in a 14-year-old female with Peutz-Jeghers syndrome. Transverse grayscale ultrasound image shows a large intraluminal hypoechoic polyp (arrow)

Blue Rubber Bleb Nevus Syndrome Blue rubber bleb nevus syndrome (BRBNS), a multifocal venous malformation, is a congenital vascular anomaly that often presents with multiple skin and soft tissue lesions accompanied by recurrent or chronic GI bleeding. Intestinal lesions range in number from tens to hundreds. The lesions typically have a sessile, polypoid appearance. Individual lesions can involve any or all layers of the bowel wall. Histologically, the lesions are composed of thin-walled venous channels that include large cystic zones. Patients often present with GI bleeding in early childhood that results in chronic anemia and a dependency on repeated red blood cell transfusions or intravenous iron administration.

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d

Fig. 10.46  Mesenteric hemangioma in a 7-week-old female who presented with anemia and rectal bleeding. (a) Transverse grayscale ultrasound image of the abdomen shows a well-circumscribed, echogenic mass (arrows) in the left upper quadrant that contains several enlarged vessels (arrowheads), and surrounds and encases bowel loops. (b) Transverse contrast-enhanced ultrasound (CEUS) image obtained in the

arterial phase shows diffuse enhancement of the mass. (c) Transverse CEUS image obtained in the venous phase shows rapid washout of contrast from the mass and s­ everal large draining mesenteric veins (arrowheads). (d) Coronal contrast-enhanced, T1-weighted, fat-suppressed MR image shows relatively hypo-enhancing loops of bowel (arrowheads) surrounded by markedly enhancing tumor (arrow)

Multiple imaging modalities are often needed to show all lesions. There is generally a limited role for ultrasound in the evaluation of the GI tract lesions of patients with BRBNS.  Labeled red blood cell scintigraphy is the best noninvasive method for revealing small bowel i­ nvolvement. Endoscopic ultrasound also plays a valuable role. Imaging is used to evaluate complications, particularly those stemming from gastrointestinal lesions, and to plan appropriate therapy [199]. In the past, control of bleeding associated with BRBNS has relied on endoscopic or surgical ablation or resection.

More recently, Sirolimus has been used successfully to control BRBNS-related bleeding [196, 200]. Cutaneovisceral Angiomatosis with Thrombocytopenia Cutaneovisceral angiomatosis with thrombocytopenia (CAT), also called multifocal lymphangioendotheliomatosis with thrombocytopenia (MLT), is a multifocal vascular anomaly that shares features of both tumor and malformation and, therefore, remains provisionally unclassified [196]. Imaging evaluation has not played a significant role in the diagnosis of these patients to date [201].

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Malignant Masses  odgkin and Non-Hodgkin Lymphoma H Hodgkin and non-Hodgkin lymphoma (NHL) are common malignancies in children. Hodgkin lymphoma is more common in adolescents and involves the nodal system. NonHodgkin lymphoma is more common in children and more frequently involves the GI tract. Non-Hodgkin lymphoma is diagnosed in approximately 700–800 children per year in the United States. Burkitt and Burkitt-like lymphomas represent the most frequent subtype of non-Hodgkin lymphoma in childhood, accounting for 35–40% of NHL [98]. The sporadic form seen in North America is associated with Epstein– Barr virus in 15% of cases. a

Most pediatric cases of NHL are high grade with aggressive behavior. Burkitt lymphoma involves the GI tract in a reported 23% of cases, affecting the distal small bowel, cecum, and appendix most frequently, with abdominal or pelvic masses in 45%. Patients present with a palpable mass, obstructive symptoms, and/or pain. Ileocolic intussusception is a rare mode of presentation. Burkitt lymphoma is the most rapidly growing tumor in children [99]. Abdominal radiographs may show bowel wall thickening with mass effect and calcification. Ultrasound will demonstrate diffuse bowel wall thickening with adjacent nodal masses in the mesentery and retroperitoneum [99]. Intussusception secondary to Burkitt’s lymphoma can also be identified (Fig.  10.47). Imaging with intravenous contrast-enhanced CT and positron b

*

c

Fig. 10.47  Burkitt lymphoma acting as a lead point for small bowel intussusception in a 6-year-old male with abdominal pain. (a) Longitudinal grayscale ultrasound image of the abdomen reveals multiple heterogeneous soft tissue masses (arrows) within the mesentery. (b) Longitudinal grayscale ultrasound image reveals a mass in the left lower quadrant with a bowel-within-bowel appearance. The bowel walls are markedly

thickened. There is a thin crescent of fluid (arrow) between the intussuscepted loops of bowel, as well as a small amount of adjacent free fluid (asterisk). (c) Axial contrast-enhanced CT image of the abdomen shows the intussusception (arrow) in the left lower quadrant with proximal thick-walled bowel loops (arrowheads)

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emission tomography (PET)/CT provide anatomic and metabolic information that are the current standard of care. PET/MR imaging may prove to be an acceptable alternative in providing high-quality images with a reduction in radiation dose compared with PET/CT [98]. Chemotherapy is the main treatment for childhood Burkitt lymphoma.

Appendix Technique Patient Positioning The patient is scanned in a supine position and asked to point to the site of maximal tenderness. As the majority of appendixes are retrocecal in location, it is important to image the paracolic gutter to search for a retrocecal appendix. If the appendix is not identified, placing the patient in a left lateral decubitus position while applying gentle anterior compression with the ultrasound transducer and posterior compression with the non-scanning hand will separate bowel loops and often improves visualization of the appendix. Another approach is to place the patient prone for several minutes, and then re-image in a supine position. Ultrasound Transducer Selection The highest resolution linear ultrasound transducer optimized for bowel wall detail is used that will permit adequate penetration, usually on the order of 15–18 MHz in children. If needed, a lower resolution transducer of about 9 MHz can be used to search for the appendix deep in the right lower quadrant or pelvis. Less often, an even lower frequency curvilinear transducer may be needed to assess the abdomen and pelvis for adequate imaging of the findings associated with appendiceal perforation. Imaging Approaches A methodical approach is undertaken to identify the appendix which is usually located 2  cm distal to the terminal ileum. Initial assessment is made using gentle, yet firm graded compression in the right lower quadrant at the site of maximal tenderness. If the appendix is not readily seen, imaging of the lateral border of the ascending colon is performed followed caudally to the level of the cecum. The appendix is retrocecal in 65% of patients [202–204]. Abdominal guarding can be used as a guide to find the appendix which is sometimes located deep in the pelvis or posterior and deep to the iliac vessels. The tip of the appendix must be found to differentiate the appendix, a blind-ending viscus, from the terminal ileum. Appendiceal diameter is measured with compression, from serosa to serosa. Color Doppler is used to assess for hyperemia

M. M. Munden and H. J. Paltiel

of the appendix and for surrounding inflammatory changes or abscess. Dependent regions are evaluated for complex fluid collections, especially in children under the age of 4 years who lack a well-developed omentum to contain a perforation. Assessment should include all four abdominal quadrants and the pelvis to search for abscess collections.

Normal Development and Anatomy Normal Development The cecal diverticulum arises from the midgut in week 6 of gestation and is the precursor of the cecum and the appendix. At 8 weeks the appendix is histologically identifiable. As the colon elongates, the cecum and appendix undergo medial rotation along with the midgut and descend into the lower right side of the abdomen (Fig. 10.9). In weeks 14 and 15 the appendiceal mucosa develops lymphoid tissue.

Normal Anatomy The normal appendix has a diameter less than 6  mm with compression and a trilaminar appearance with a thin, echogenic central stripe (Fig.  10.48). The length can be up to 10–12 cm. Single wall thickness is less than 2 mm. Normal diameter is usually on the order of 3–4 mm. The lamina propria normally contains lymphoid follicles which can hypertrophy in response to gastroenteritis.

Fig. 10.48  Normal appendix in a 4-year-old male complaining of right lower quadrant pain. Transverse grayscale ultrasound image shows a normal, slender appendix (arrows) with a trilaminar appearance of the wall draped (arrows) across the psoas muscle and common iliac vessels

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Acute Appendicitis The overall incidence of appendicitis is 7% and is the most common cause for emergency surgery in children. In accordance with the ALARA principle, both the American College of Radiology and the American Academy of Pediatrics recommend ultrasound as the initial imaging modality for evaluation of suspected appendicitis. The more slender the body habitus, the better the imaging detail. However, even some children with a large body habitus can be successfully imaged by ultrasound for appendicitis. A body mass index of less than 30 is used by some centers as a cut-off for ultrasound evaluation. On ultrasound, an acutely inflamed appendix appears as a blind-ending tubular structure that is non-compressible and measures 6 mm or more in diameter. The size of the appendix can vary significantly for both normal and abnormal appendixes, and the 6-mm criterion is more useful for excluding appendicitis than for confirming it (Fig. 10.49). Ultrasound findings of acute appendicitis include a diameter of 6 mm or more with compression, an outer wall thickness greater than 3 mm, hyperemia, surrounding echogenic mesenteric fat, and adjacent echogenic fluid (Table  10.3). Thinning of the appendiceal wall to less than 2 mm in thickness and right lower quadrant loculated fluid collections have been shown to be highly specific (>90%) for perforation. The presence or absence of an intraluminal fecalith should be noted. A small amount of simple fluid may be seen adjacent

a

to the appendix, even in the absence of perforation. Mesenteric lymphadenopathy frequently accompanies appendicitis, but by itself is a nonspecific finding also seen with other types of abdominal inflammation. Thickening and increased echogenicity of the periappendiceal mesenteric fat is a valuable secondary finding of appendicitis. The presence of more than one ultrasound sign of inflammation should be considered strong evidence of appendicitis, even if other definitive signs are absent [204]. Secondary abscess formation and an extruded fecalith are sometimes identified (Figs. 10.50 and 10.51). Imaging pitfalls include lymphoid hyperplasia, where the muscular wall will be thickened but smooth from hyper­ trophied lymphoid follicles and the lumen will contain no ­exudate. With lymphoid hyperplasia, the appendix may be non-compressible, with a 6–8-mm diameter. In the absence of periappendiceal inflammatory fluid, hyperechoic periappendiceal fat, and mural hyperemia, there is a low likelihood of appendicitis (Fig. 10.52) [205]. Fecal impaction can also distend the appendix, but the normal bowel wall layers will be maintained and there will be no associated hyperemia or surrounding inflammatory changes (Table 10.3) [206]. Treatment of acute appendicitis has historically been surgical appendectomy. However, there is now evidence that uncomplicated cases of acute appendicitis can be treated with antibiotics alone [207]. Therefore, features of complicated appendicitis, including the presence or absence of a fecalith, signs of perforation, and fluid collections are important to document.

b

Fig. 10.49  Acute retrocecal appendicitis in a 9-year-old female with 2 days of right lower quadrant pain. (a) Sagittal grayscale ultrasound image of the right paracolic gutter demonstrates a thickened outer appendiceal wall and distended lumen measuring more than 6 mm in

diameter (­calipers). There is minimal adjacent free fluid. (b) Sagittal color Doppler ultrasound image reveals marked hyperemia of the inflamed appendiceal wall (arrow)

Table 10.3  Ultrasound features of the normal and abnormal appendix Diameter with compression Outer wall thickness Hyperemia Surrounding inflammation

Normal appendix < 6 mm < 3 mm No No

Appendicitis > 6 mm Increased outer wall thickness > 3 mm Yes Yes

Lymphoid hyperplasia Can be > 6 mm Thickened lamina propria Sometimes No

Inspissated stool Can be > 6 mm Normal No No

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Fig. 10.50  Perforated appendicitis in a 12-year-old male presenting with 4  days of right lower quadrant pain. Transverse color Doppler ultrasound image of the right lower quadrant demonstrates a focal fluid collection (arrow) adjacent to a distended appendix (arrowhead)

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Fig. 10.52  Lymphoid hyperplasia of the appendix in a 10-year-old male with right lower quadrant pain. Transverse color Doppler ultrasound image of the right lower quadrant shows an enlarged, thickwalled and hyperemic appendix (arrow)

Fig. 10.53  Inspissated fecal material in the appendix of a 15-year-old female with cystic fibrosis. Sagittal grayscale ultrasound image of the appendix (cursors) reveals echogenic intraluminal material (arrow) but no thickening of the wall

Fig. 10.51  Large fecalith with perforated appendicitis in a 14-year-old female. Transverse color Doppler ultrasound image shows a large, shadowing fecalith (arrow) within a distended appendix. There is marked thickening of the surrounding soft tissues

Cystic Fibrosis of the Appendix The diameter of the appendix in asymptomatic patients with CF is often greater than 6  mm due to mucoid and stool impaction with a reported mean diameter of 8.3  mm

(Fig. 10.53) [208]. Acute appendicitis in patients with cystic fibrosis is rare, with an incidence of 1–2% compared with an overall incidence of 7% in the general population [209]. Chronic abdominal pain is common in patients with CF, who also frequently receive antibiotics for treatment of pulmonary infections. Both of these factors can delay the diagnosis of acute appendicitis. As a consequence, appendiceal perforation and other complications of acute appendicitis are higher in patients with CF than in the general population. An ultrasound diagnosis of acute appendicitis in a CF patient should therefore be based on signs of inflammation, including focal tenderness with compression, loss of definition of wall layers, surrounding omental or mesenteric fat infiltration, and abnormal intraperitoneal fluid, rather than appendiceal diameter.

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Benign Masses of the Appendix Mucocele of the Appendix Mucocele of the appendix refers to a cystically dilated appendix filled with mucin caused by a non-acute obstruction of the appendiceal neck. It is very rare in children, typically occurring in middle-aged adults [210].

Malignant Tumors of the Appendix Carcinoid Malignant neoplasms of the appendix are rare, occurring in approximately 1% of appendectomy specimens, with carcinoid tumor the most common appendiceal malignancy [211]. Carcinoid tumor is a neuroendocrine neoplasm and is often found incidentally on pathological examination of appendectomy specimens and tends not to be aggressive. About 75% of tumors are localized to the appendiceal tip. A rare, functioning tumor can produce vasoactive substances and manifest as carcinoid syndrome with diarrhea and wheezing. However, most carcinoid tumors of the appendix are much more likely to present clinically as acute appendicitis rather than with carcinoid syndrome. Ultrasound findings are those of typical appendicitis with carcinoid tumor usually discovered unexpectedly on pathoa

logic examination. Calcification in an appendiceal carcinoid has been reported to mimic an appendicolith [212]. Treatment is surgical, sometimes requiring removal of the adjacent cecum and right colon for larger masses. As the majority of carcinoid tumors are localized to the tip of the appendix, surgery is curative if the mass is less than 2 cm in size [213, 214].

Lymphoma of the Appendix The GI tract is the most common site for extra-nodal NHL.  The distal small bowel, terminal ileum, cecum, and appendix are common sites of involvement. Most reported pediatric cases of appendiceal lymphoma are caused by the Burkitt lymphoma subtype. The incidence of Burkitt lymphoma has been increasing over the last several decades. The median age of children with Burkitt lymphoma is 8 years and the tumor doubling time is approximately 24  hours. Most patients present with abdominal pain, a palpable mass, and obstruction, as well as symptoms that can mimic acute appendicitis. Actual appendiceal involvement is rare, reported to be 1–3% [99]. Ultrasound findings include enlargement of the appendix with diffuse mural thickening (Fig. 10.54). CT cases of the rare appendiceal lymphoma have shown soft tissue masses in the right lower quadrant with no discernible normal appenb

c

Fig. 10.54 Lymphoma of the appendix in a 14-year-old male with large B-cell lymphoma. Sagittal (a) and transverse (b) grayscale ultrasound images of the right lower quadrant of the abdomen reveal a markedly thickened, hypoechoic appendix, with loss of definition of the

normal wall layers. (c) Transverse grayscale ultasound image shows that the appendix (arrowhead) abuts a large right lower abdominal and pelvic soft tissue mass (arrows)

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dix [215]. PET/CT is performed to evaluate for additional sites of disease. Treatment depends on extent of disease, and in children involves aggressive chemotherapy. Five-year survival is between 80% and 90% [216].

Colon Technique Patient Positioning For ultrasound study of the large bowel, the patient is usually examined in a supine position but can be placed in a left lateral decubitus position with posterior manual compression while scanning from an anterior approach, gently compressing anteriorly with the ultrasound transducer to separate bowel loops. Ultrasound Transducer Selection A high-resolution linear transducer on the order of 12–18 MHz and optimized for bowel technique with a low wall filter and low pulse repetition frequency is used to initially evaluate the entire colon. The bowel wall is assessed with grayscale and color Doppler imaging for thickness, definition of wall layers and hyperemia (Fig.  10.55). Cine loops are used to evaluate colonic motility. If an abnormality is encountered, a lower frequency transducer is used to identify abnormal fluid collections or abscesses in all dependent regions of the abdomen and pelvis.

Fig. 10.55  Normal ascending colon in a 16-year-old male. Sagittal grayscale ultrasound image reveals a thin wall (between arrows) with normal definition of wall layers

M. M. Munden and H. J. Paltiel

Imaging Approaches In the emergent setting, no bowel preparation is required. If a study is scheduled to assess for IBD, a patient ideally should be fasting for 4 hours prior to ultrasound evaluation. Hydration with clear liquids distends the bladder which can be used as an acoustic window, and also displaces small bowel loops from the pelvis. The bladder can be emptied after the initial assessment to perform deeper compression. The colon should be studied in transverse and sagittal planes, beginning with the right lower quadrant. The position of the colon and the presence of haustra aid in distinguishing the colon from the small bowel. The rectum is imaged by using the fluid-filled bladder as an acoustic window. Pathological colonic wall thickening is easily detected, as well as hyperemia. Normal colon typically shows little vascularity. A retrograde saline enema can be used to help identify a polyp or mass. The five layers of the colonic wall should be readily depicted in most patients [105].

Normal Development and Anatomy Normal Development By the fourth week of gestation, the gastrointestinal tract has divided into foregut, midgut, and hindgut. The small and large intestines undergo rapid growth in the fourth and fifth weeks of life and quickly exceed the available space in the abdominal cavity. The midgut herniates into the umbilical cord, forming a loop. The superior limb of the intestinal loop forms the ileum while the inferior limb forms the colon. The herniated intestine rotates ninety degrees counterclockwise around the mesentery so that the proximal portion of the loop migrates from a superior position to the right side and the distal portion of the loop migrates from an inferior position to the left. The superior limb of the loop forms the ileum while the inferior limb forms the colon. The herniated intestine rotates ninety degrees counterclockwise around the mesentery so that the inferior limb migrates to the left. In the tenth week, the bowel retracts back into the abdominal cavity and rotates 180 degrees coun-

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terclockwise. The cecum is then positioned in the right upper quadrant of the abdominal cavity. Colonic growth displaces the cecum into its final position in the right lower quadrant (Fig. 10.9). The hindgut initially consists of the cloaca, which is later separated by a septum into a dorsal GI compartment and a ventral urogenital compartment (Fig. 17.5). The blood supply of the hindgut comes mainly comes from inferior mesenteric artery. The hindgut subsequently differentiates into the distal third of transverse colon, the descending colon, sigmoid colon, rectum and upper anus. The transverse colon and sigmoid colon have a mobile mesentery, while the mesentery of the descending colon becomes fixed to the dorsal wall. The upper third of the rectum is ultimately intraperitoneal in location, the middle third retroperitoneal and the lower third infraperitoneal along with the superior anus.

Normal Anatomy The colon is the largest portion of the intestine where water is absorbed from the digestive content and waste material is stored as feces. Bacterial fermentation of undigested material takes place in the colon. The first portion of the colon is the cecum, joined to the terminal ileum at the ileocecal valve. The cecum continues to the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. As described in the Development section above, the ascending colon, descending colon, and rectum are normally fixed in the retroperitoneum while the remainder of the colon is intraperitoneal. The transverse colon is encased in peritoneum and connected to the posterior abdominal wall by the transverse mesocolon. Unlike the small bowel, the colon has distinct haustral markings caused by contraction of the taeniae coli, three bands of smooth muscle that run the length of the colon. The arterial supply to the colon is via the superior and inferior mesenteric arteries and a connecting marginal artery that runs the length of the colon. Normal colonic wall thickness is 2 mm [105].

Congenital Anomalies Anorectal Malformations Anorectal malformations are among the most common congenital anomalies found in the newborn period, occurring in approximately 1 in 5000 births, and ranging from minor to very complex lesions. Thirty-six percent are reportedly isolated lesions while about 60% are associated with other abnormalities. Anorectal malformations occur above the levator muscles in about 45%, and are low in position, passing through the levator ani muscles in about 55% [217]. Anorectal malformations frequently occur as a component of the VACTERL association. The more proximal the colonic malformation, the more frequent the associated anomalies. The incidence of associated urinary tract anomalies with imperforate anus ranges from 26% to 50%. Associated chromosomal defects occur in 8% of patients [218]. Patients present at birth with bowel obstruction, failure to pass meconium, and an absent or abnormal anus. High imperforate anus is often associated with a rectovesical or rectourethral fistula. When urine mixes with meconium, a characteristic enter­ olithiasis can be seen by both plain radiography and ultrasound. Ultrasound can be used to confirm its intraluminal location and differentiate it from extraluminal meconium peritonitis [106]. Transperineal high-resolution ultrasound imaging can demonstrate the site of the fistula and the distance of the blind-ending rectum to the perineal skin surface (Fig. 10.56). The study should not be performed in a crying infant as the increased abdominal pressure moves the rectal pouch closer to the perineal surface. A pouch-to-perineum distance of 15 mm has a sensitivity of 100% and a specificity of 86% in separating low from high and intermediate forms of imperforate anus [219]. Treatment of anorectal malformations is surgical. If the rectum is low in position, a single procedure can be performed to pull the rectum through the anal sphincter. If the rectum is in a high position, a three-staged correction is typical with the first stage consisting of colostomy to allow

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d

Fig. 10.56  Newborn female with low imperforate anus and meconium passing from the vagina. (a) Sagittal transperineal grayscale ultrasound image shows the anus (arrow) just deep to the skin surface with small echogenic bubbles (arrowhead) in the rectovaginal fistula. (b) Transverse grayscale ultrasound image demonstrates a stool-filled rectum (arrow) posterior to the decompressed bladder (B). (c) Prone

abdominal radiograph with metallic marker (arrow) placed over distal rectum during the ultrasound study underestimates the distal extent of the rectum. (d) Transverse grayscale ultrasound image of the right lower quadrant reveals a large amount of stool (arrow) within the sigmoid colon

stool passage and creation of a mucous fistula to permit mucous drainage. A colostogram is then performed to assess the distance of the blind-ending rectum from the skin surface and to assess for the presence of a fistula. The second operation is performed to close the fistula. The third procedure is closure of the colostomy. Voiding cystourethrography combined with distal colonography via a mucous fistula has traditionally been used to demonstrate the fistulous connections in patients with anorectal malformation. Contrast-enhanced colosonography

(ceCS) is a new technique that involves the instillation of ultrasound contrast material into the mucous fistula followed by scanning from an anterior sagittal, transperineal, and posterior sagittal approach. This technique has been used to outline the distal colon and identify the presence and location of fistulas without the use of ionizing radiation [220]. Similarly, voiding urosonography performed after installation of ultrasound contrast material into the bladder can also outline rectourethral fistulous tracts as the patient voids (Fig. 10.57).

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U

R B

Fig. 10.57  Imperforate anus with rectourethral fistula in a 2-month-old male. Transperineal longitudinal image from a contrast-enhanced voiding urosonogram (ceVUS) shows the bladder (B) and urethra (U). A fistulous tract (arrow) is seen extending posteriorly from the prostatic portion of the urethra to the rectum (R)

Colonic Wall Thickening Necrotizing Enterocolitis Necrotizing enterocolitis (NEC) is a form of intestinal inflammation that is estimated to occur in 5–14% of infants weighing less than 1500 grams at birth, with a mortality rate ranging from 25% to 40% [221]. The pathogenesis of NEC is multifactorial, with immaturity and a compromised intestinal epithelial barrier leading to bacterial overgrowth, intestinal inflammation, and systemic infection. NEC can present with increasing gastric residuals, bowel distention, and bloody diarrhea and progress to intestinal perforation, shock, and death. The distal ileum and proximal large bowel are most commonly involved, although extensive involvement of the entire colon can occur. Diagnosis is based on clinical findings, laboratory values, and imaging features. NEC can progress from a medically managed disorder to surgical NEC with the need for abdominal drainage or bowel resection. Imaging findings on plain radiography include bowel distention, pneumatosis, portal venous gas, and pneumoperitoneum when there is perforation of necrotic bowel. Periodic supine and lateral decubitus films are performed

for patients on a “NEC watch.” Bowel ultrasound has become a useful adjunct to plain radiography for the diagnosis of NEC and its complications. Ultrasound can be used to evaluate bowel wall thickness and perfusion and detect abdominal fluid collections. It can also detect pneumatosis, portal venous gas, and free air (Fig. 10.58). Pneumatosis appears as echogenic foci within the bowel wall that do not change with compression, while intraluminal gas is mobile and changes with bowel compression. Ultrasound is more sensitive for the detection of pneumatosis than plain radiography [222]. Bowel wall thickness, echogenicity, and perfusion are initially increased due to inflammation [223]. As the disease progresses, the bowel wall becomes thinned with decreased-to-absent perfusion and loss of peristalsis. Bowel wall thinning is defined as a thickness of less than 1  mm [224]. Contrast-enhanced ultrasound of the bowel has been shown to be more sensitive than color Doppler imaging in the detection of blood flow to the bowel [225]. Treatment of NEC involves bowel rest, replacement of fluids, and intravenous antibiotics. Surgical intervention is required in the event of bowel perforation or necrotic bowel. Secretory immunoglobulin (Ig)A acquired via the ingestion of human milk helps to provide protection against NEC.

Ulcerative Colitis Ulcerative colitis (UC) is a chronic, relapsing inflammatory condition of the colon that can present with bloody diarrhea, tenesmus, crampy abdominal pain, and weight loss. The incidence of pediatric-onset UC is from 1 to 4 per 100,000 in the United States and Europe [226]. The course and extent of pediatric-onset disease tend to be more severe, with a 30–40% colectomy rate at 10 years. Affected children also suffer from delayed puberty and skeletal maturation. Studies have shown that 60–80% of pediatric patients present with pancolitis, compared with only 20–30% in adults [227]. While UC has historically been perceived as a superficial inflammatory process that uniformly involves the rectum and progressed contiguously toward the proximal colon, more recent data have shown rectal sparing in 5% of children at diagnosis [227]. Gastritis is commonly seen in association with UC and erosions may be present [228]. No special bowel preparation is required for ultrasound assessment. Bowel loops are evaluated for diminished peristalsis, hyperemia, wall thickening, strictures, and adjacent mesenteric inflammatory changes (Fig. 10.59). Conventional transabdominal ultrasound provides limited assessment of the sigmoid colon and rectum. Barium studies can be used to assess for stricture formation.

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c Fig. 10.58  Necrotizing enterocolitis in a 1-week-old premature infant. (a) Transverse midline abdominal power Doppler ultrasound image reveals thinning (arrow) of the bowel wall with surrounding hyperemia. (b) Sagittal power Doppler ultrasound image of the subhepatic region one

a

day later shows an echogenic ring of pneumatosis (arrow) and extensive bowel wall hyperemia. (c) Sagittal grayscale ultrasound image of the right upper quadrant demonstrates a small echogenic focus of air (arrow) along the upper liver edge consistent with early bowel perforation

b

Fig. 10.59  Ulcerative colitis in a 22-year-old male complaining of left-sided abdominal pain. (a) Longitudinal grayscale ultrasound image of the left lower abdominal quadrant shows thickening (arrowheads) of

the wall of the descending colon with loss of normal haustral folds. (b) Longitudinal color Doppler ultrasound image reveals mural hyperemia (arrowheads)

Treatment goals in children with UC depend on disease severity. Aminosalicylates are used to induce remission in patients with mild-to-moderate disease. Oral steroids are recommended for inducing remission in patients with moderate

disease but not for long-term administration. In refractory cases, infliximab and oral tacrolimus can be used. Maintenance therapy is continued indefinitely. Colectomy is considered when patients are unresponsive to medical therapy [226].

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Crohn Disease Approximately 60% of patients with Crohn disease have colonic involvement. Approximately a half of these patients have synchronous involvement of the small intestine; the rest have disease limited to the colon. Colonic Crohn disease can be segmental or involve the entire colon. As with Crohn ­disease elsewhere in the GI tract, it is often associated with normal skip areas. Fistulas involving the colon are usually secondary to small intestinal disease although primary colonic fistulas also occur. Focal colonic perforation is common and can lead to an abscess or fistula [229]. Abdominal or pelvic abscess can present with a wide range of clinical findings, from low-grade fever and mild abdominal pain to sepsis and peritonitis. As previously described for ulcerative colitis, ultrasound evaluation of the colon in patients with Crohn disease can detect altered peristalsis, hyperemia, wall thickening, strictures, adjacent mesenteric inflammatory changes, as well as

b

a

c

ascites and abscesses. Transperineal imaging provides information regarding perirectal disease [230]. CT enterography is favored over MR enterography in an acute setting using neutral oral contrast to visualize mural enhancement, and is preferred for its ability to detect pneumatosis and free air. MR enterography is the modality of choice for assessment of perianal and perirectal complications of Crohn disease and its ability to detect active disease [231]. Contrast-enhanced ultrasound can be performed to assess colonic wall vascularity at the microcirculatory level. Prominent mural enhancement is associated with active disease, an important distinction from fibrosis, since active disease is managed medically and fibrotic strictures typically require surgical treatment. Time-intensity curves can be used to compare disease activity over time and inform patient management decisions (Fig. 10.60) [232]. Shear wave elastography can help to distinguish between fibrotic and non-fibrotic zones of colonic narrowing [233].

d

Fig. 10.60  Crohn disease in an 18-year-old male. (a) Transverse grayscale ultrasound image of the right lower quadrant of the abdomen reveals thickening of the wall of the terminal ileum and cecum (arrow) with luminal narrowing. There is loss of definition of the normal bowel wall layers. (b) Transverse power Doppler ultrasound image shows mural hyperemia. (c)

Transverse CEUS image demonstrates marked transmural enhancement of the terminal ileum and cecum. (d) Time–intensity curves generated from regions of interest placed over the wall of the abnormal bowel segments. These curves can be used to more objectively assess treatment response when compared over time

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Treatment depends on disease location and severity. Medical therapies include immunosuppressant and anti-tumor necrosis factor drugs. Monoclonal antibodies have been recently been approved for clinical use [234].

Infectious Colitis Infectious colitis is a common cause of acute abdominal pain in children and is characterized by the passage of three or more loose stools per day. In developing countries, diarrheal disease can be devastating in children under 5 years of age. Most cases of infectious gastroenteritis are viral in etiology with rotavirus, norovirus, adenovirus, and astroviruses the common pathogens (Fig. 10.61) [146]. Rotavirus is the leading cause of infantile diarrheal illness worldwide [235]. Gram-negative bacteria including Shigella, Salmonella, Campylobacter, Escherichia coli, and Yersinia also frequently cause enteritis. The primary mode of transmission of bacterial enteritis is via the fecal–oral route, through ingestion of contaminated food and water as well as direct human-to-human contact.

Bacterial colitis can be noninflammatory or inflammatory. Noninflammatory bacterial pathogens such as E. coli and Staphylococcus lead to watery diarrhea without an associated febrile illness. Enterohemorrhagic E. coli can cause hemorrhagic colitis after ingestion of contaminated foods. Yersinia, Campylobacter, Shigella, Chlamydia, and Salmonella infections may have bloody and mucopurulent diarrhea associated with fever and severe abdominal pain [147]. Yersinia and Salmonella usually infect the ascending colon (Fig.  10.62) while Shigella infects the descending colon (Fig.  10.63). Salmonella infection frequently has associated adenopathy and splenomegaly. Cytomegalovirus, pseudomembranous colitis, and E. coli usually result in pancolitis [150]. Ultrasound is useful in identifying bowel wall thickening, hyperemia, and free fluid. When the cecum and ascending colon demonstrate thickened, echogenic walls, Campylobacter infection should be considered. Wall thickening with prominent ileocolic nodes caused by Yersinia infection can mimic Crohn disease [236].

a

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Fig. 10.61  Adenoviral enteritis in a 6-year-old male. Sagittal grayscale ultrasound images of (a) the ascending colon (arrow) and (b) the rectum (arrow) show diffuse wall thickening

a

Fig. 10.62  Salmonella enteritis in a 3-year-old female. (a) Sagittal grayscale ultrasound image of the ascending colon shows diffuse wall thickening (calipers) with loss of haustral folds (arrow). (b) Sagittal

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color Doppler ultrasound image of the affected ascending colon reveals hyperemia (arrow) of the bowel wall

10  The Gastrointestinal Tract

Viral gastroenteritis is usually self-limited, and treatment is symptomatic and supportive. Patients with severe bacterial enteritis are treated with antibiotics.

S

Fig. 10.63  Shigella enteritis in a 2-year-old male with bloody diarrhea. Transverse grayscale ultrasound image of the splenic flexure reveals circumferential bowel wall thickening (arrow). S, Spleen

Fig. 10.64  Clostridium difficile colitis in a 12-year-old male who completed a recent course of antibiotics. Sagittal grayscale ultrasound images show diffuse wall thickening of (a) the ascending colon and (b)

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Pseudomembranous Colitis Pseudomembranous colitis is usually precipitated by a course of antibiotics that interferes with the normal colonic bacterial flora and results in colonization by Clostridium difficile. Yellow-white nodules or plaques form pseudomembranes on the mucosal surface of the colon. Clindamycin, penicillin, fluoroquinolones, and cephalosporins are typically associated with pseudomembranous colitis, although any antibiotic can potentially be implicated. The incidence of C. difficile infections has been increasing steadily over the past two decades [237]. Infection is mediated by the production of two exotoxins, toxin A and toxin B. Patients commonly present with abdominal pain, profuse, watery and foul-smelling diarrhea, fever, and leukocytosis about 3–9 days after initiation of antibiotic treatment. Approximately 3–8% will develop fulminant infection with severe ileus, toxic megacolon, colonic perforation, and/or septic shock [238]. Ultrasound imaging shows diffuse and marked wall thickening of the entire colon and ascites (Fig. 10.64). Plain films of the abdomen may show a colonic ileus, thumb-printing, ascites, and a toxic megacolon (greater than 5.6 cm diame-

the descending colon (arrows), respectively. (c) Axial contrast-enhanced CT image reveals a “double halo” sign (arrow) of submucosal edema

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ter) in severe cases. CT, if needed, often shows diffuse colonic wall thickening and nodularity, bowel wall stranding with edema, ascites, the “accordion” sign when oral contrast is trapped between thickened haustral folds or the “double halo” sign of submucosal edema with 2 or 3 concentric rings in the large bowel. With the exception of Crohn’s disease, the wall thickening that occurs with pseudomembranous colitis is greater than with any other infectious or inflammatory processes [239, 240]. Treatment consists of administration of metronidazole or vancomycin with most patients responding within 3–4 days.

Neutropenic Colitis Neutropenic colitis, or typhlitis, is a life-threatening transmural inflammation of the cecum, terminal ileum, and ascending colon that affects approximately 5% of children who

M. M. Munden and H. J. Paltiel

receive chemotherapy, with a mortality rate of about 5%. It occurs primarily in neutropenic patients, most often children with leukemia. Patients with Burkitt lymphoma may also have an increased risk of neutropenic colitis [241]. Cytotoxic chemotherapy causes a breakdown of the gut mucosa leading to mucosal ulceration and necrosis, and bowel wall edema [242]. More extensive involvement of the colon, including the rectum, has been reported [243]. Patients usually present with abdominal pain, fever, and neutropenia. Diarrhea and vomiting are also common. Imaging plays an important role in the diagnosis of neutropenic colitis. Ultrasound is often sufficient for diagnosis, showing a bowel wall thickness of 3 mm or greater with circumferential thickening of the cecum that extends into the terminal ileum and ascending colon (Fig. 10.65). Pneumatosis can affect the entire colon, and there are surrounding inflam-

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b

Fig. 10.65  12-year-old male with acute lymphocytic leukemia and neutropenic colitis. Sagittal (a) and transverse (b) ultrasound images with grayscale (left panels) and color Doppler (right p­ anels) show

diffuse wall thickening (arrows) and hyperemia (arrowheads) of the ascending colon

10  The Gastrointestinal Tract

matory changes and ascites. Infectious etiologies that need to be distinguished from neutropenic colitis include pseudomembranous colitis, GVHD, and cytomegaloviral colitis. C. difficile colitis typically affects the entire colon, while GVHD involves both small and large bowel with prominent mucosal enhancement on CT. While ultrasound is usually sufficient for diagnosis of neutropenic colitis, CT is useful for detection of complications such as perforation and abscess, showing circumferential wall thickening with pericecal fat stranding and pneumatosis [239, 242, 244]. Medical management with antibiotics, granulocyte colony-stimulating factor, and total parenteral nutrition has led to improved outcomes and decreased mortality rates.

Cystic Fibrosis Cystic fibrosis transmembrane regulator (CFTR) dysfunction in the GI tract is present in all CF patients, regardless of genotype. The CFTR protein controls the secretion of chloride, bicarbonate, and fluid into the colon. The most serious intestinal complication of CF is obstruction. Patients may develop rectal prolapse and ileocolic intussusception due to enlarged lymphoid follicles or thickened stool. There is an increased incidence of Crohn disease and fibrosing colonopathy in patients with CF.  Fibrosing colonopathy is an iatrogenic complication that tends to develop in patients under the age of 10 years who are receiving high-dose pancreatic enzyme replacement [183]. Ultrasound will show colonic dilation, wall thickening, and hyperemia. Ileocolonic intussusception and ascending colon strictures can also be identified [245]. Radiologic features of fibrosing colonopathy include nodular thickening, loss of haustral folds, and stricture formation predominantly involving the ascending colon. Pericolonic and mesenteric fat proliferation are shown on CT, as well as signs of perforation or bowel ischemia.

343

Water-soluble enemas are used to relieve severely impacted stool. Lubiprostone, a calcium chloride channel activator, is used for treatment of chronic constipation. Ivacaftor, a transmembrane conductance regulator–potentiator, has been shown to improve the gut microbial flora and to reduce intestinal inflammation [246].

Hemolytic–Uremic Syndrome Hemolytic–uremic syndrome (HUS) is a disorder characterized by low red blood cells, acute kidney failure, and low platelets. Children typically develop diarrhea, stomach cramping, and fever 3–4 days after eating food contaminated with bacteria that produce the Shiga toxin that then incites an autoimmune response. E. coli-type O157:H7 is the responsible organism in about 80% of cases. Other organisms including Streptococcus pneumoniae, Shigella, and Salmonella and certain medications can also cause HUS. Patients initially present with bloody diarrhea, fever, vomiting, and weakness. Renal dysfunction and low platelets develop as the diarrhea is improving. Atypical HUS is often due to a genetic mutation and presents differently. Both forms of HUS can lead to widespread inflammation and thrombotic microangiopathy. HUS typically occurs in children under the age of 5 years and is a leading cause of acute kidney failure in young children, affecting about 1.5 per 100,000 people per year [247, 248]. Hemorrhagic colitis is the most common GI manifestation of HUS.  Ischemia leading to bowel perforation can occasionally occur. Ultrasound will show concentric wall thickening that most often involves the cecum and ascending colon, as well as ascites (Fig.  10.66). Renal involvement manifests as enlarged, echogenic kidneys. CT will show wall thickening, luminal narrowing, and pericolonic fat stranding [239]. Treatment is supportive, and may include corticosteroids, dialysis, and plasmapheresis. About 70–85% of patients will have a full recovery.

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M. M. Munden and H. J. Paltiel

Fig. 10.66  6-year-old female with hemolytic–uremic syndrome. (a) Transverse grayscale ultrasound image shows a thick-walled colonic loop in the right lower quadrant of the abdomen. (b) Transverse color Doppler ultrasound image reveals hyperemia of the colonic

wall. (c) Sagittal grayscale ultrasound image of the right kidney (K) demonstrates increased cortical echogenicity compared to the adjacent liver (L)

Benign Masses

of juvenile polyposis syndrome (JPS). The number of juvenile polyps is important since more than five polyps increase the risk for colorectal cancer, which is discussed below. A challenge occurs when managing a patient with three or four juvenile polyps because it is unclear whether the patient will go on to develop juvenile polyposis syndrome and therefore be at significant risk for intestinal cancer. Juvenile polyposis syndrome is an autosomal dominant condition in which colonic polyps continue to increase in number during adolescence and adulthood. Extra-colonic polyps can also be found throughout the GI tract. The cumulative lifetime risk for colorectal cancer in patients with juvenile polyposis syndrome is 39%. Solitary

Juvenile Polyp Juvenile polyps are hamartomatous lesions and are the most common benign colonic tumors in childhood, with an incidence of approximately 1%. They occur most often in the first 10 years of life, with a peak incidence between 2 and 5  years of age. There is a male-to-female ratio of 1.4:1 Solitary juvenile polyps carry no malignant potential. However, adolescents and adults with multiple juvenile polyps do carry a significant risk of malignancy [249]. Patients with 2–5 polyps fulfill the criteria for multiple juvenile polyps while those with more than 5 polyps meet the definition

345

10  The Gastrointestinal Tract

and/or inflammation [70, 73]. Treatment of a colonic duplication cyst consists of surgical removal.

Malignant Tumors

Fig. 10.67  Juvenile polyp in a 3-year-old male with painless rectal bleeding. Sagittal grayscale ultrasound image of the left lower quadrant shows a round, heterogeneous, solid lesion (calipers) in the descending colon

juvenile polyps are typically left-sided, measuring from 1 to 3 cm in size and are usually pedunculated. These polyps usually present with painless rectal bleeding although some may manifest as a prolapsing mass or with mucopurulent stools [250]. Colonoscopy is the modality of choice for the detection of juvenile polyps [251, 252]. Ultrasound has been shown to have a low sensitivity of 47% but a high specificity of 100% in the detection of colonic polyps in children who do not undergo bowel preparation prior to examination [251]. Polyps appear as intraluminal, vascular, hypoechoic lesions containing internal cystic areas (Fig.10.67). Colonic filling defects are seen on contrast enema. Solitary polyps are removed by polypectomy. Suggested surveillance of patients with juvenile polyposis syndrome includes colonoscopy every 3 years from the time of symptom occurrence or in the early teenage years if symptoms have not occurred in the setting of a family history; and upper endoscopy every 2 years beginning at 15 years of age [249].

Duplication Cyst Approximately 6.8% of all duplication cysts occur in the colon with about 30% containing ectopic gastric mucosa [253]. Colonic duplication cysts may be asymptomatic or can present with obstruction, abdominal pain, and bleeding. As previously described for duplication cysts occurring elsewhere in the GI tract, ultrasound can demonstrate the characteristic “gut signature” of these lesions with the hyperechoic inner mucosal layer surrounded by a hypoechoic layer of smooth muscle. Internal contents can be simple and anechoic or complex with internal contents from bleeding

Lymphoma A recent review of NHL of the GI tract noted that approximately 29% of tumors involved the colon. Burkitt lymphoma was the most common subtype, followed by diffuse large B-cell lymphoma. Colonic tumors had the best survival rate [254]. Clinical presentation varies, including abdominal pain, weight loss, diarrhea, and intussusception [255]. The nonspecific presentation may lead to delays in diagnosis. Bowel wall thickening, bulky adenopathy, and hepatosplenomegaly can be seen with ultrasound and CT (Fig. 10.68) [256]. The ileocecal region is commonly affected by B-cell lymphoma. Well-defined tumor margins with preserved fat planes are typically seen with CT. Colonic lymphoma is treated with chemotherapy. Surgery is performed for palliation of pain and treatment of obstruction, perforation, and bleeding [256]. Adenocarcinoma Colorectal adenocarcinoma in children is extremely rare, representing about 1% of all pediatric neoplasms. The annual incidence in children is about one in ten million in patients less than 20 years of age, with a peak incidence at 15 years. Despite its rarity, it is still the most common primary solid malignancy of the GI tract in children [257, 258]. Predisposing conditions are identified in 10–30% of patients with colorectal adenocarcinoma, including familial adenomatous polyposis, UC, Crohn disease, and Peutz–Jeghers syndrome. In a large case series of colorectal carcinoma in children, 22% had colonic polyps and 8 of 77 had multiple polyps [259]. A high microsatellite instability is one of the most important genetic mutations associated with childhood colorectal carcinoma. Tumors are evenly distributed between the right and left sides of the colon with most diagnosed pathologically as mucinous adenocarcinoma. Presenting symptoms are nonspecific, and include abdominal pain and vomiting, weight loss, altered bowel habits, hematochezia, and anemia. Diagnosis is therefore often delayed in children due to a low initial clinical suspicion for colorectal carcinoma. Duration of symptoms prior to diagnosis can range from 2 to 6 months, so that children are more likely to have advanced disease at diagnosis, which may contribute to the overall poor outcomes associated with this tumor [260]. Ultrasound imaging can show concentric, hypoechoic colonic wall thickening with a target or “pseudokidney” appearance consisting of central echogenic mucosa surrounded by thickened bowel wall. Imaging findings are

346

a

c

Fig. 10.68  Burkitt lymphoma in a 5-year-old male complaining of abdominal pain for a month. (a) Sagittal grayscale ultrasound image of the right upper quadrant shows mass-like thickening (arrows) of the colon. (b) Transverse grayscale ultrasound image of the right lower

M. M. Munden and H. J. Paltiel

b

d

quadrant shows similar mass-like thickening of the colon (arrow). (c) Transverse color Doppler ultrasound image of the right lower quadrant mass reveals internal perfusion. (d) Coronal contrast-enhanced CT image depicts the large right colonic mass (arrow)

10  The Gastrointestinal Tract

Fig. 10.69  Adenocarcinoma of the colon in a 15-year-old male. Supine radiograph of the abdomen reveals psammomatous calcifications (arrow) in the distal colon associated with mucinous adenocarcinoma

similar to those in adults with case reports of plain film and contrast studies documenting lower GI obstruction. Plain films may reveal a paralytic ileus with large soft tissue masses containing calcifications in advanced cases (Fig.  10.69). Barium studies often reveal an “apple core” lesion. CT will show a colonic mass with segmental, circumferential wall thickening. Liver and peritoneal masses are readily depicted. PET/CT is often used to depict the overall extent of disease. Treatment involves surgical removal of the cancer. There is some controversy as to the role and type of chemotherapy to use in children with colonic adenocarcinoma. Monoclonal antibody target therapy has shown promising results for metastatic disease. As colon cancer is so rare in children, survival rates are uncertain. The stage at diagnosis is one of the most important factors in determining mortality rate [249].

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11

Liver Jeannie K. Kwon, Maddy Artunduaga, Javier D. Gonzalez, Alexandra M. Foust, Elisabeth P. Moredock, Süreyya Burcu Görkem, and Harriet J. Paltiel

Abbreviations 2D SWE ADPKD AFP AML ARFI BCS CEUS CH CMV CT CVP DWI EBV e-FAST EHE ERCP FALD

Two-dimensional shear-wave elastography Autosomal dominant polycystic kidney disease Alpha-fetoprotein Acute myeloid leukemia Acoustic radiation force impulse Budd–Chiari syndrome Contrast-enhanced ultrasound Congenital hemangioma Cytomegalovirus Computed tomography Central venous pressure Diffusion-weighted imaging Epstein–Barr virus Extended focused assessment with sonography in trauma Epithelioid hemangioendothelioma Endoscopic retrograde cholangiopancreatography Fontan-associated liver disease

J. K. Kwon (*) · E. P. Moredock Department of Radiology, Children’s Medical Center Dallas, University of Texas Southwestern Medical Center, Dallas, TX, USA e-mail: [email protected] M. Artunduaga Department of Radiology, Pediatric Radiology Division, University of Texas Southwestern Medical Center, Children’s Health Medical Center, Dallas, TX, USA J. D. Gonzalez Medical Center Radiology Group, Orlando Health Arnold Palmer Hospital for Children, Orlando, FL, USA A. M. Foust Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA S. B. Görkem Division of Pediatric Radiology, Department of Radiology, Erciyes University School of Medicine, Kayseri, Turkey H. J. Paltiel Division of Ultrasound, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA

FDG Fluorodeoxyglucose FLHCC Fibrolamellar variant of HCC FNH Focal nodular hyperplasia GLUT-1 Glucose transporter protein-1 HBV Hepatitis B virus HCC Hepatocellular carcinoma HCV Hepatitis C virus HIDA Hepatobiliary iminodiacetic acid HIV Human immunodeficiency virus HMH Hepatic mesenchymal hamartoma HSCT Hematopoietic stem cell transplantation HSV Herpes simplex virus HU Hounsfield unit IHH Infantile hepatic hemangioma IVC Inferior vena cava IQR Interquartile range MRCP MR cholangiopancreatography MRE MR elastography MR Magnetic resonance NAFLD Nonalcoholic fatty liver disease NASH Nonalcoholic steatohepatitis NHL Non-Hodgkin lymphoma NICH Noninvoluting congenital hemangioma PET Positron emission tomography PHL Primary hepatic lymphoma PICH Partially involuting congenital hemangioma PLD Polycystic liver disease PRETEXT Pretreatment extent of tumor pSWE Point shear-wave elastography PTLD Posttransplant lymphoproliferative disorder RI Resistive index RICH Rapidly involuting congenital hemangioma ROI Region of interest SHL Secondary hepatic lymphoma SOS Sinusoidal obstruction syndrome TACE Transarterial chemoembolization TE Transient elastography TE Echo time TIPS Transjugular intrahepatic portosystemic shunt (abbreviations continue)

© Springer Nature Switzerland AG 2021 H. J. Paltiel, E. Y. Lee (eds.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-56802-3_11

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(abbreviations continued) TPN UES UVC VOD

Total parenteral nutrition Undifferentiated embryonal sarcoma Umbilical vein catheter Veno-occlusive disease

Introduction A wide spectrum of disorders can affect the pediatric liver. This chapter will focus on the role of ultrasound in the diagnosis and management of pediatric hepatic disorders, including a review of transducer selection and imaging techniques, liver development and anatomy, and an overview of the most clinically relevant anatomical variants, congenital anomalies, as well as benign and malignant hepatic disorders encountered in daily practice. Ultrasound imaging of liver transplantation is also discussed.

the liver should be obtained in the transverse, sagittal, and coronal planes. Asking the patient to perform deep inspiration with breath-hold causes the liver to move inferiorly and may avoid the acoustic shadowing from the lower right ribs and improve visualization of the hepatic dome. Liberal use of color and pulsed Doppler imaging as well as contrast-enhanced ultrasound (CEUS) imaging can help distinguish blood vessels from bile ducts and characterize vascular lesions.

Grayscale Imaging Grayscale imaging is used to obtain a global assessment of the hepatic parenchyma (Fig.  11.1, Table  11.1). For

L

Technique Patient Positioning Ultrasound examination of the liver is performed with patients in a supine position. Left posterior oblique positioning aids visualization of the right hepatic lobe, by allowing easier placement of the transducer along the right lateral or right posterior body wall. Having the patient raise the right arm above their head results in opening of the lower intercostal spaces, allowing for a wider sonographic window.

K

Fig. 11.1  Normal liver in a 5-month-old male. Sagittal grayscale ultrasound image shows normal parenchymal echotexture of the liver (L) and right kidney (K)

Ultrasound Transducer Selection In infants and small children, the liver is ideally imaged Table 11.1  Causes of diffuse change in hepatic echotexture with a linear or curved-array transducer with a frequency of Decreased Increased 5–9 MHz. In larger patients, a 2.5–5 MHz transducer may Infectious hepatitis (hepatitis Steatosis B, hepatitis C) be required to enable greater penetration and visualization Drug-induced (steroids, Inflammatory hepatitis of the deeper portions of the larger right hepatic lobe. High-­ chemotherapeutic agents) (non-alcoholic frequency linear transducers up to 12 MHz or more are usesteatohepatitis, drug-­ ful in smaller infants and for the evaluation of superficial induced, autoimmune) Cirrhosis structures, including the liver surface contour. Transducers Neoplastic infiltration (leukemia, lymphoma) with a smaller footprint permit intercostal scanning.

Imaging Approaches Fasting for 3–4 hours prior to the ultrasound examination for infants, and 4–6  hours for older children, minimizes bowel gas and aids visualization of the liver [1]. Images of

Nutritional (total parental nutrition, Miscellaneous (fasting state, extreme malnutrition) passive venous congestion, septic shock) Metabolic (glycogen storage disorder, α1-antitrypsin deficiency, Wilson disease, hemochromatosis, cystic fibrosis, tyrosinemia) Chronic hepatitis

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example, a generalized increase in echogenicity is most commonly seen in the setting of hepatic steatosis. In contrast, a diffusely hypoechoic appearance of the liver with relatively increased echogenicity of the portal triads, the so-­called “starry sky” appearance, is a reflection of parenchymal edema (Fig. 11.2) [2]. Grayscale imaging also depicts blood vessels, bile ducts, and cysts, which appear as tubular or round, anechoic structures coursing through the liver.

Doppler Ultrasound

Fig. 11.2  “Starry sky” appearance of the liver in a 7-year-old female in septic shock. Transverse grayscale ultrasound image shows diffusely hypoechoic hepatic parenchyma due to edema with the portal triads appearing relatively more echogenic than normal

Fig. 11.3  Normal color Doppler appearance of the main portal vein in a 19-month-old female. Transverse color Doppler ultrasound image of the liver shows normal flow toward the liver (hepatopetal flow) encoded in red (arrow). Flow away from the liver (hepatofugal) is encoded in blue

a

Fig. 11.4  Normal spectral Doppler waveforms in a 1-month-old female. (a) Oblique color Doppler ultrasound image of the liver reveals a normal mildly pulsatile waveform in the main portal vein.

Doppler ultrasound is most useful for the evaluation of blood vessels or for blood flow detection within a cystic or solid structure (Fig.  11.3). Analysis of the spectral Doppler waveforms provides information regarding flow velocity and direction (Fig. 11.4). Flow indices such as the arterial resistive index (RI) can be calculated based on peak systolic velocity, end diastolic velocity, and mean velocity of blood flow. Color and pulsed Doppler imaging are commonly performed to assess posttransplant vascular structures or vascular masses; evaluate flow in the portal vein; and differentiate blood vessels from bile ducts or other fluid-filled structures (Fig. 11.5) [1]. Power Doppler can be useful in detecting low-flow, especially in the setting of suspected portal vein and hepatic vein thrombosis.

b

(b) Oblique color Doppler ultrasound image of the liver shows a normal low-resistance arterial waveform in the main hepatic artery with a resistive index (RI) measurement of 0.60

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microbubbles remain confined to the vascular space as blood pool agents [3, 4]. CEUS is useful to evaluate focal liver lesions, with the ability for real-time characterization of enhancement patterns and a greater ability to detect blood flow compared to Doppler imaging [3, 5–8]. In the arterial phase, the extent and pattern of the vascular supply of a lesion can be determined. Portal venous and delayed phase imaging is used to assess the patterns of washout of contrast material, which help to differentiate between benign and malignant lesions [9]. Patterns of enhancement can also be used to differentiate solid lesions from complex cystic collections. One advantage of CEUS over computed tomography (CT) is that it provides excellent temporal resolution without the use of ionizing radiation. Compared with magnetic resonance (MR) imaging, CEUS examinations tend to be shorter in duration and can accommodate more patient motion, decreasing the need for sedation, an important concern in children [7, 10, 11]. In addition, ultrasound Fig. 11.5  Parenteral-nutrition-associated liver disease in a 19-month-­ old male. Transverse power Doppler ultrasound image of the liver uses contrast agents have a high safety profile, without nephrotoxicity a color map to depict the amplitude of the Doppler signal in the right or hepatotoxicity [3, 12–15]. Repeat bolus administration of the portal vein and its branches. Flow velocity and direction are not indi- contrast agent can also be performed as needed. cated, but noise is diminished, thereby permitting higher gain settings Imaging is best performed with contrast-specific software, and increased sensitivity for the detection of flow. Note the abnormally which uses a low mechanical index to minimize microbubble increased echogenicity of the hepatic parenchyma destruction within the imaging field of view. Typically, a dualdisplay mode is used, with side-by-side grayscale imaging for Contrast-Enhanced Ultrasound anatomic localization, and contrast-­mode with background Contrast-enhanced ultrasound (CEUS) uses microbubbles that tissue suppression to display areas of enhancement (Fig. 11.6) are smaller than the size of a red blood cell to assess the vas- [16]. Quantitative analysis with time–intensity curves can also cularity of a tissue or organ. When injected intravenously, the be performed [17].

a

b Fig. 11.6  Normal liver depicted by contrast-enhanced ultrasound (CEUS) in a 12-day-old male. (a) Sagittal CEUS image of the liver in the arterial phase (right panel) with reference grayscale image (left panel) shows intravenous contrast filling the hepatic arteries (arrow-

head). (b) Transverse CEUS in the delayed phase (right panel) with reference grayscale image (left panel) reveals that intravenous contrast has homogeneously distributed throughout the liver parenchyma

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Elastography Elastography is a relatively new ultrasound technique that noninvasively assesses the stiffness of tissue in response to an applied stress, which is estimated by tracking and measuring the speed of shear waves propagating through tissues. Three main methods for liver assessment exist, which differ in the source of the applied stress, the size of the sampling area, and the output parameters reported (Table 11.2) [18]. One-dimensional transient elastography (TE) is a method developed and used only for liver fibrosis assessment [19]. It employs a mechanical impulse created by a piston-like probe (FibroScan®, Echosens, Paris, France) that is applied at the skin surface over a small region of interest (ROI). TE measurements are obtained without imaging guidance. Both point shear-wave elastography (pSWE) and twodimensional shear-wave elastography (2D SWE) are incorporated into many clinical ultrasound systems and use an acoustic radiation force impulse (ARFI), rather than a mechanical impulse, to generate shear waves. With these ARFI methods, grayscale ultrasound imaging can be used to guide placement of the ROI and avoid nonparenchymal structures such as vessels and the gallbladder. Added benefits of 2D SWE are a larger ROI and the generation of color elastogram maps that correspond to degrees of tissue stiffness (Fig. 11.7). Up to 10 measurements are obtained in the same location of the liver (typically, segments VII or VIII), and results are

reported as median values in units of m/sec and/or kilopascals (kPa) (Fig. 11.8), with quality assessment values reported as interquartile range (IQR)/median (%) [18]. As in adults, good correlation between ARFI and histological staging of liver fibrosis has been observed in pediatric patients [19–21]. In the liver, elastography is useful for the assessment of fibrosis, with clinical applications continuing to expand, including the evaluation of biliary atresia and Fontan-associated liver disease [22–24].

Fig. 11.7  Hepatic cirrhosis in a 19-year-old female with cystic fibrosis. Transverse grayscale elastography ultrasound image shows diffusely echogenic liver parenchyma with elevated mean velocity measurement consistent with cirrhosis

Table 11.2  Comparison of elastography methods Measurement region Region of interest size Relative cost Impulse sources Image guidance and correlations Patient-related limitations MR, Magnetic resonance

Transient elastography (TE) Shear-wave elastography (SWE) One-dimensional Point (pSWE) 2-dimensional (2D SWE) 4 cm3 1.0 cm3 (pSWE) or 20 cm3 (2D SWE) Small region of interest Larger regions of interest $ $$ Mechanical impulse Acoustic radiation force impulse (ARFI) No imaging assessment of Grayscale evaluation of hepatic liver parenchyma Limited by ascites and body Limited by body habitus habitus More studies needed for validation

MR elastography (MRE) 4 axial selections 250 cm3 Evaluates entire liver $$$ Mechanical impulse Concurrent conventional MR imaging can further assess for masses and cirrhosis Possible need for sedation Contraindications to MR imaging

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Fig. 11.8  Normal liver stiffness values in a 17-year-old female. Oblique transverse 2D shear-wave elastography ultrasound image of the right lobe of the liver demonstrates side-by-side display of the measurement confidence map (left) and the corresponding color stiffness map (right). Two

small, circular regions of interest are placed within the maps in the green areas (left) indicating high confidence, with corresponding shades in the cool end of the color spectrum (blue) showing normal stiffness levels (right). Note the diffusely echogenic parenchyma consistent with fatty liver

Normal Development and Anatomy

ligament, which carries the umbilical vein. As cells of the hepatic diverticulum proliferate, interlacing cords of hepatic cells join to form hepatic sinusoids. There are at least 20 discrete cell populations in the fully developed liver, including hepatocytes, endothelial cells, cholangiocytes, hepatic stellate cells, and Kupffer cells [25]. At 7 weeks, the ductus venosus emerges as a large shunt that connects the umbilical vein to the inferior vena cava, allowing blood to bypass the liver (Fig. 11.10).

Normal Development In the fourth week of life, the hepatic diverticulum emerges as a ventral outgrowth of the caudal end of the foregut and will eventually form the liver (Fig. 11.9). The hepatic diverticulum extends into the septum transversum, which forms part of the diaphragm and the ventral mesentery. The ventral mesentery gives rise to the lesser omentum and the falciform

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361 Aorta Hepatic diverticulum Duodenum Heart

Peritoneal cavity

Septum transversum

Hepatic diverticulum growing into the septum transversum

Level of section B

Superior mesenteric artery

a

b

Heart

Septum transversum

Diaphragm

Dorsal mesentery

Lesser omentum

Duodenum

Developing liver

Liver

Level of section D

Falciform ligament

Dorsal aorta

Visceral peritoneum

Free border of ventral mesentery

Parietal peritoneum Inferior mesenteric artery

Peritoneal cavity

c

Falciform ligament

d

Fig. 11.9  Diagram of embryologic development of the liver. (a) Sagittal section of a 4-week embryo. (b) Transverse section through the plane of the dashed line in (a). The hepatic diverticulum extends into the septum transversum as the peritoneal cavity expands. (c) Sagittal

section of a 5-week embryo. (d) Transverse section through the plane of the dashed line in (c). The liver is joined to the ventral abdominal wall by the falciform ligament and to the stomach and duodenum by the lesser omentum

Hepatic portion of inferior vena cava

Hepatic vein (right vitelline)

Hepatic vein (left vitelline)

Ductus venosus

Portal vein

Left umbilical vein Splenic vein

Superior mesenteric vein

Fig. 11.10  Ventral view of the liver in a 7-week embryo. Hepatic sinusoids form the ductus venosus which carries blood from the umbilical vein to the inferior vena cava

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In fetal life, oxygen-rich blood is supplied by the placenta through the umbilical vein. Blood in the umbilical vein drains into the left portal vein and from there flows through the ductus venosus to the hepatic vein confluence and into the inferior vena

a

cava (IVC). After birth, the umbilical vein and ductus venosus close, and their remnants persist as the round ligament of the liver and the ligamentum venosum, respectively (Fig. 11.11).

b

LP

LP

c

LP

Fig. 11.11  Umbilical vein closure in a 1-day-old female. (a) Transverse grayscale ultrasound image of the liver shows the left portal vein (LP) with the umbilical vein (white arrow) anteriorly seen in cross-section as a round echogenic structure. The ductus venosus (black arrow) is closing, and appears as a band-like echogenic focus extending posteriorly from the left LP to the IVC (arrowhead). (b) Transverse color Doppler

ultrasound image of the liver shows flow within the LP and absence of flow in the umbilical vein (white arrow). This appearance should not be confused with thrombosis of the left portal vein. (c) Longitudinal color Doppler ultrasound image of the liver shows the course of the umbilical vein (white arrows) within the liver as it approaches the LP. Note that there is flow within the LP, but not in the umbilical vein

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Normal Anatomy  egmental and Lobar Anatomy S The liver is divided into three lobes: left, right, and caudate. Three vertically oriented planes containing the right, middle, and left hepatic veins, respectively, radiate from the IVC to divide the liver into four sections. The right and left lobes are separated by the main lobar fissure, which contains the middle hepatic vein and runs through the gall bladder fossa to the IVC. The right intersegmental fissure contains the right hepatic vein and divides the right lobe into anterior and posterior sections. The left intersegmental fissure contains the left hepatic vein and divides the left lobe into medial and lateral sections. The caudate lobe is located at the posterior aspect of the liver, separated from the left hepatic lobe by the fissure for the ligamentum venosum anteriorly, and bounded by the IVC posteriorly (Figs. 11.12 and 11.13). The papillary process is the anteromedial extension of the caudate lobe.

H PV CL

PH

IVC

Fig. 11.12  Normal ultrasound anatomy of the caudate lobe in a 12-year-old male. Longitudinal grayscale ultrasound image of the left hepatic lobe shows the caudate lobe (CL) located in the posterior aspect of the liver and separated from the left hepatic lobe by the fissure for the ligamentum venosum (black arrow) anteriorly, and bounded by the inferior vena cava (IVC) posteriorly. The portal vein (PV), hepatic artery (H), and pancreatic head (PH) are also seen

Anterior Quadrate lobe Gallbladder Round ligament of liver

Cystic duct

Porta hepatis Hepatic artery proper

Right lobe

Common hepatic duct Hepatic portal vein Coronary ligament Inferior vena cava

Left lobe

Bare area Caudate lobe

Ligamentum venosum

Posterior Fig. 11.13  Diagram of segmental and lobar anatomy of the liver, inferior view. The hepatic artery proper, common hepatic duct, and hepatic portal vein course through the porta hepatis. The quadrate lobe lies anterior to the porta hepatis; the caudate lobe lies posterior

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The Couinaud classification system of liver anatomy further divides the right and left hepatic lobes into superior and inferior segments by an imaginary horizontal plane containing the right and left main portal branches [26]. Its usefulness lies in the fact that each segment is a functional unit that contains its own dual inflow blood supply (arterial and portal venous), lymphatic drainage, and biliary drainage, and can be individually resected. Segment I is the caudate lobe. Segments II to VIII are numbered in a clockwise fashion beginning in the left lateral superior liver. Segments II and III comprise the left lateral section, superior and inferior to the portal plane, respectively. Segment IV is the quadrate lobe and comprises the left medial section. It is divided into segments IVa and IVb, located superior and inferior to the portal plane, respectively. Segments V and VI comprise the right hepatic lobe inferior to the portal plane, in the anterior and posterior sections, respectively. Segments VII and VIII comprise the right hepatic lobe superior to the portal plane, in the anterior and posterior sections, respectively (Figs. 11.14 and 11.15).

Right posterior section

Ligaments The liver is covered by a thin layer of fibrous connective tissue known as Glisson’s capsule. The majority of the liver is covered by the visceral peritoneum and is associated with several peritoneal ligaments that anchor the liver to the abdominal wall (Fig. 11.16). The ligaments can be seen by ultrasound as linear, echogenic structures that are more conspicuous when they contain fibrofatty tissue or are surrounded by ascites. The coronary ligament attaches the superior surface of the liver to the inferior surface of the diaphragm via its anterior and posterior folds. The bare area of the liver is the portion of the liver surface located between the anterior and posterior folds of the coronary ligament that is not covered by peritoneum. Adjacent to the bare area, the right and left triangular ligaments are formed by the union of the anterior and posterior folds of the coronary ligament and attach the liver to the diaphragm (Fig. 11.17). Anteriorly, the right and left triangular ligaments converge to form the falciform ligament, which attaches the

Right anterior section

Left medial section

Left lateral section Middle hepatic vein

Right hepatic vein

Left hepatic vein VII

II VIII I

IV III

VI V

Inferior vena cava Hepatic duct Hepatic artery Portal vein

Gall bladder

Bile duct Cystic duct

Fig. 11.14  Couinaud classification of liver anatomy. The liver is divided into eight functionally independent segments based on a transverse plane that passes through the bifurcation of the main portal vein, each with its own vascular inflow, outflow, and biliary drainage. In the center of each segment, there is a branch of the hepatic artery, portal vein, and bile duct.

Along the edges of each segment, there is venous outflow through the hepatic veins so that each hepatic vein drains two adjacent segments. The division of the liver into independent units means that individual segments can be resected without damaging the remaining segments

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b

a

IVa/b VIII

III

IVb

II/III

M

R VII

*

V/VIII R

I

VI/VII

Fig. 11.15  Ultrasound hepatic segmental anatomy in a 14-year-old male. (a) Transverse grayscale ultrasound image of the liver at the level of the left portal vein (arrow). The left hepatic lobe is divided by the left portal vein into the superior segments (IVa and II) and the inferior segments (IVb and III). The superior segments of the right hepatic lobe (VII and VIII) are divided by the right hepatic (R) and middle hepatic (M) veins. The caudate lobe (I) is

I

*

located anterior to the IVC (asterisk) (b) Transverse grayscale ultrasound image of the liver at the level of the right portal vein (arrow). The right hepatic lobe is divided by the right portal vein into the superior segments (VII and VIII) and the inferior segments (V and VI). The medial left hepatic lobe segments (IVa and IVb) and the lateral left hepatic lobe segments are divided by the left hepatic vein (not pictured). I, Caudate lobe; asterisk, IVC

Bare area (diaphragmatic surface of liver) Coronary ligament

Left triangular ligament Right triangular ligament Fibrous appendix of liver Left lobe, diaphragmatic surface Right lobe, diaphragmatic surface

Falciform ligament

Round ligament of liver (obliterated umbilical vein) Inferior border Gallbladder, fundus Fig. 11.16  Diagram of an anterior view of the liver with its ligamentous peritoneal attachments

liver to the anterior abdominal wall and carries the umbilical vein to the liver during fetal development (Fig. 11.18). The umbilical vein remnant forms the round ligament of the liver and runs along the free edge of the falciform ligament to the origin of the left portal vein. The ductus venosus, which carries fetal blood from the umbilical vein to the IVC, closes after birth to form the ligamentum venosum.

The hepatogastric and hepatoduodenal ligaments are peritoneal folds that attach the porta hepatis of the liver to the stomach and proximal duodenum and form the lesser omentum. The hepatoduodenal ligament contains the main portal vein, the proper hepatic artery, and the common bile duct. The hepatogastric ligament extends from the ligamentum venosum and contains the left gastric artery and vein.

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FF

L

K

Fig. 11.17  Ultrasound demonstration of the right triangular ligament in a 15-year-old female. Transverse grayscale ultrasound image of the right hepatic lobe (L) shows the right triangular ligament (white arrow) which is well depicted because of the adjacent perihepatic free fluid (FF). K, Right kidney

ated, nutrient-rich blood from the spleen and intestines. The main portal vein divides into right and left branches to supply the right and left hepatic lobes, respectively. The right portal vein subsequently divides into anterior and posterior branches. The walls of the portal veins are echogenic by ultrasound, making them easily distinguishable. On spectral Doppler imaging, the normal portal vein demonstrates mild phasicity, related to cardiac and respiratory activity. In the fasting state, the normal peak flow velocity in the main portal vein should vary between approximately 20–40 cm/s [28]. Slower velocities occur in the setting of portal hypertension, and faster velocities are noted postprandially. Classic hepatic arterial anatomy, in which the celiac axis branches into the left gastric, splenic, and common hepatic arteries, is seen in approximately 50% of the population. After giving off the gastroduodenal artery, the common hepatic artery becomes the proper hepatic artery, which then divides into the right and left hepatic arteries [27]. The proper hepatic artery supplies approximately 50% of the liver’s oxygen requirements. The hepatic artery branches accompany the portal vein branches, and, along with bile duct branches, form the portal triads, which are enclosed in a connective tissue sheath. The normal hepatic artery shows pulsatile, low-resistance flow, with resistive indices ranging between 0.55 and 0.70 [28]. Elevated resistance may be seen in the postprandial state; in chronic hepatocellular disease, including cirrhosis; in hepatic venous congestion; and in transplant rejection. Decreased resistance may be seen in proximal arterial narrowing (such as transplant anastomotic stenosis) or distal vascular shunts (such as posttraumatic or iatrogenic fistulas) [29]. Blood flow leaves the liver through the right, middle, and left hepatic veins (Fig. 11.19). The hepatic veins in turn drain

IVa M

L

II

VIII R Fig. 11.18  Ultrasound demonstration of the falciform ligament in an 18-year-old male. Transverse grayscale ultrasound image shows a linear echogenic band (arrowhead) extending to the liver capsule

Hepatic Circulation The liver has a dual blood supply from the portal vein and the hepatic artery. About 70% of the afferent blood flow into the liver is from the portal venous system, unique vessels that begin and end in a capillary system [27]. The portal vein supplies the liver with approximately half of its oxygen requirements by bringing partially deoxygen-

VII

IVC

Fig. 11.19  Ultrasound demonstration of normal hepatic veins in a 12-yearold male. Transverse color Doppler ultrasound image of the liver demonstrates the right (R), middle (M), and left (L) hepatic veins converging at the inferior vena cava (IVC). Couinaud segments VII, VIII, IVa, and II are separated by the hepatic veins in the superior portion of the liver

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into the IVC. The right hepatic vein drains segments V–VIII. It typically courses through the right intersegmental fissure and separates the superior anterior and posterior segments of the right hepatic lobe (Couinaud segments VIII and VII, respectively). The middle hepatic vein drains segments IV, V, and VIII. It courses through the main lobar fissure and separates segments IVa and VIII, while the left hepatic vein, which drains segments II and III, courses through the left intersegmental fissure and separates segments II and IVa. The caudate lobe drains separately into the IVC via multiple perforating veins. The typical hepatic venous spectral Doppler waveform has four phases with inflection points reflecting right atrial systole (A wave), right ventricular systole (S wave), right ventricular diastole (V wave), and right atrial diastole (D wave). The larger S and D waves demonstrate flow toward the heart.

 ormal Hepatic Parenchyma N The basic structural units of the liver are the acini, which are oriented in a radial configuration to form a lobule (Fig. 11.20). The dual blood supply enters an acinus at the periphery of the lobule via the hepatic arteriole and portal venule which converge to allow blood to mix in the sinusoids. Blood then exits the acinus at the central vein, which is at the center of the lobule. Kupffer cells located along the sinusoids serve a filtering function for blood. The space of Disse, which is located adjacent to the sinusoidal endothelium and separates it from the hepatocytes, contains stellate and other stromal cells. Running in parallel alongside the sinusoids are the bile canaliculi, which carry bile that flows in the opposite direction to the blood, toward the periphery of the lobule. The hepatic artery proper, common hepatic duct, and hepatic portal vein course through the porta hepatis (Fig. 11.21). On ultrasound, the normal liver demonstrates homogeneous echogenicity with low-level echoes. Typically, the

walls of the portal veins are echogenic, which can help to differentiate them from the hepatic veins (Fig. 11.22). In children less than 6 months of age, the liver may be mildly hypoechoic or isoechoic relative to the normal right renal cortex. By 6  months of age, the liver is typically minimally hyperechoic relative to the right kidney and mildly hypoechoic relative to the spleen.

Anatomic Variants Familiarity with anatomic variations in liver anatomy will help to avoid confusion or misdiagnosis, and their recognition can be critical in treatment planning of diseased livers. Reidel’s lobe is an inferior tongue-like projection of hepatic parenchyma that can extend quite inferiorly along the right paracolic gutter and be mistaken for hepatomegaly (Fig. 11.23). “Sliver of liver” or “Beaver tail liver” refers to a variant where the lateral segment of the left hepatic lobe extends far leftward and appears to wrap around the spleen. The papillary process of the caudate lobe is an anteromedial extension of hepatic parenchyma that may mimic a mass near the head of the pancreas. Typically, the right and left hepatic arteries arise from the common hepatic artery at the porta hepatis. Some of the more common variations in hepatic arterial anatomy include: (1) a replaced or accessory left hepatic artery arising from the left gastric artery; (2) a replaced right hepatic artery arising from the superior mesenteric artery; and (3) a replaced common hepatic artery arising from the superior mesenteric artery. Standard portal venous anatomy consists of a main portal vein branching into right and left portal veins, with subsequent division of the right portal vein into anterior and posterior branches. Variations include trifurcation of the main portal vein into right anterior, right posterior, and left portal veins. Occasionally, the right posterior portal vein arises as the first branch of the main portal vein. Central vein Sinusoid

Stellate cell

Kupffer cell

Space of Disse

Endothelial cell

Bile ductule

Hepatocyte Portal venule Hepatic arteriole

Portal field

Fig. 11.20  Diagram of a liver acinus, the smallest functional unit of the liver. Blood flows from the portal venule through a hepatic sinusoid to the central vein. Bile flows in the opposite direction within the bile ductule

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Portal vein atresia can occur when involution of the fetal umbilical vein is excessive. The fetal umbilical vein normally drains into the left portal vein and spontaneously involutes at birth. When involution is excessive, portal vein stenosis or atresia can develop. When there is atresia of a major branch of the portal vein, there can be associated absence of the corresponding hepatic lobe [27]. The preva-

lence of portal vein hypoplasia in the setting of biliary atresia has been reported to be up to 26% [27]. Other congenital anomalies are described in Section “Congenital Anomalies.” Anatomic variations of the hepatic veins are common. For example, there may be an accessory right inferior hepatic vein that drains directly into the IVC, and an accessory right superior anterior vein that drains into the middle hepatic vein. The

Fig. 11.21  Ultrasound demonstration of a normal porta hepatis in an 8-year-old female. Longitudinal oblique grayscale (left) and color Doppler (right) ultrasound images of the porta hepatis through which

course the hepatic artery proper (black arrows), common hepatic duct (black arrowheads), and main portal vein (calipers, white arrows). The hepatic duct is the most anteriorly located of the three structures

Fig. 11.22 Normal hepatic parenchyma in a 17-year-old male. Transverse grayscale ultrasound image of the liver depicts a normal liver contour and normal hepatic parenchymal echotexture. The right, middle, and left hepatic veins are seen converging and draining into the IVC (asterisk). Portal veins (white arrowhead) are identified by their thin, echogenic walls which differentiates them from hepatic veins (white arrow) which typically have imperceptible walls

Fig. 11.23  Riedel lobe in an 18-year-old female. Sagittal grayscale ultrasound image shows an elongated, tongue-like projection of the right hepatic lobe (arrowheads) extending inferior to the lower pole of the right kidney, a normal variant

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middle and left hepatic veins often form a common trunk prior to draining into the IVC. The caudate lobe veins are also variable, with one or more veins draining separately into the IVC.

Congenital Anomalies

trast administration. Rarely, these cysts can appear complex due to hemorrhage or superinfection. Most congenital hepatic cysts are incidentally detected and will remain stable in size or undergo resolution without the need for intervention. Larger, symptomatic cysts may be excised or fenestrated via open or laparoscopic surgery [31]. Simple aspiration is not favored due to the risk of recurrence.

Liver Cyst Congenital liver cysts are thought to represent hyperplastic bile duct rests that progressively dilate due to failure of development of normal connections with the biliary tree. They consist of an outer layer of fibrous tissue and are lined with biliary-type epithelium. As there is no connection to the biliary tree, the contained fluid is clear and typically does not contain bile. These cysts are most often identified as an incidental finding on prenatal or postnatal imaging and are not associated with any genetic syndrome or cysts in other organs. The overall prevalence of congenital liver cysts has been reported to be 2.5% [30], and they occur more often in girls than boys. The increasing use of cross-sectional imaging has shown that they are more common than originally believed. Congenital liver cysts are usually asymptomatic, ranging in size from a few mm to several cm. Rarely, cysts may become large enough to produce symptoms, such as dull right-upper-­ quadrant pain, abdominal bloating, or nausea. Complications are more common in larger cysts and can include cholestasis due to bile duct compression, spontaneous hemorrhage, infection, or torsion in the case of exophytic cysts. On ultrasound, these lesions appear as an anechoic, simple unilocular or multilocular cyst, with a thin or imperceptible wall and posterior acoustic enhancement (Fig. 11.24). They may be multiple in number and vary in size, with larger cysts measuring more than 4  cm in diameter. CT and MR imaging demonstrate a smooth-walled, fluid attenuation or intensity lesion without enhancement after intravenous con-

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Polycystic Liver Disease Polycystic liver disease (PLD) comprises a heterogeneous group of autosomal dominant conditions that lead to defective biliary cell growth. Defective proteins in primary cilia lead to abnormal development of the ductal plate [32]. This results in variable, but progressive development of cystic hamartomas (von Meyenburg complexes) throughout the liver which are isolated and not part of the biliary tree. Hepatic cysts increase in size and number with increasing age and are rare in young children. PLD is the most common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD) (Fig. 11.25) [33]. Rarely, milder forms of PLD occur in the absence of ADPKD, although the pathologic appearance is identical. Female patients have a greater severity of disease, thought to be related to estrogen exposure [33, 34]. Most patients are asymptomatic and maintain normal liver function, although large cysts and massive hepatomegaly may cause mass effect leading to n­ ausea, dyspnea, severe abdominal pain, abdominal distention, and early satiety [33]. Imaging findings include predominantly simple cysts which may vary in size and number, depending on patient age. Often, there are more than 20 liver cysts, with only a few kidney cysts [32]. Over time, more than 50% of the liver parenchyma will be replaced by cysts ranging from less than 10 mm to 80 mm in size [35]. Dominant cysts are typical. Peribiliary cysts may appear as sub-centimeter cysts or tubular structures oriented along

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Fig. 11.24  Congenital hepatic cyst in a 69-day-old male. (a) Transverse grayscale ultrasound image shows a simple-appearing cystic lesion (arrowhead) within the hepatic parenchyma adjacent to the gallbladder

(asterisk). (b) Color Doppler ultrasound image reveals the completely avascular nature of the lesion

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Fig. 11.25  Autosomal dominant polycystic liver disease in a 21-year-­ consistent with a cyst. (b) Transverse grayscale ultrasound image of the old male. (a) Transverse grayscale ultrasound image of the liver shows a right kidney shows multiple cortically based cysts with enhanced through well-circumscribed, anechoic lesion (arrow) in the right lobe of the liver transmission (arrowheads) that demonstrates enhanced through transmission of sound (arrowheads)

the portal vessels. Hemorrhagic or infected cysts can be heterogeneous in echotexture on ultrasound, with increased attenuation on unenhanced CT, and increased T1-weighted signal on MR imaging. Other findings, such as fluid-fluid levels, cyst wall thickening, and calcification suggest infection. Somatostatin analogues have been shown to reduce liver volume in patients with PLD [36]. Dominant liver cysts can be treated with aspiration and sclerotherapy, fenestration, or segmental hepatic resection. Liver transplantation is indicated in only a minority of patients [37].

Congenital Portosystemic Shunts Congenital portosystemic shunts are rare vascular abnormalities that occur as a result of abnormal development or involution of the fetal vasculature. Blood from the splanchnic venous circulation is shunted to the systemic circulation, bypassing the hepatic sinusoids in a variety of anatomic configurations. The prevalence is about 1:30,000 children [27]. With intrahepatic shunts (including abnormal persistence of a patent ductus venosus), abnormal connections occur between branches of the portal vein and the hepatic veins or IVC (Fig. 11.26). Extrahepatic shunts (also known as Abernethy malformation) may demonstrate splanchnic venous return to any systemic vein, with or without preservation of portal venous perfusion to the liver [38]. Extrahepatic shunts associated with congenital absence of the portal vein are more common in females and are often associated with other congenital anomalies, including skeletal defects, congenital heart d­ isease, polysplenia, intestinal malrotation, and genitourinary anomalies.

Clinical manifestations of congenital portosystemic shunts may be related to the bypassing of splanchnic blood from the liver and include hypergalactosemia, hyperammonemia, hepatic encephalopathy, hypoxia due to hepatopulmonary syndrome, and pulmonary hypertension. Deprivation of portal flow to the liver may result in elevated liver enzymes, liver atrophy, and the development of hepatic lesions, including regenerative nodules, focal nodular hyperplasia, adenoma, hepatoblastoma and hepatocellular carcinoma [27]. Doppler ultrasound is the first-line imaging modality for identifying congenital portosystemic shunts. Imaging findings are variable, depending upon the location of the portosystemic shunt, and can include anomalous portosystemic connections, absence of the main portal vein or its branches, and compensatory enlargement of the hepatic artery. The portal vein may have a biphasic or triphasic waveform that reflects variations in right heart pressure [1]. CT or MR imaging can be used to define shunt anatomy if it is not completely delineated by ultrasound. MR imaging can also evaluate associated focal liver lesions. Unlike acquired portosystemic shunts, congenital shunts are not associated with imaging features of portal hypertension (such as varices, ascites, or splenomegaly), which can help to differentiate between the two. Many intrahepatic shunts will spontaneously close by 1 year of age without requiring definitive treatment. In older patients, surgical shunt occlusion or transcatheter coil embolization may be effective in treating symptoms and preventing complications. However, in patients with total absence of portal venous supply, liver transplantation is the appropriate therapeutic option.

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Fig. 11.26  Congenital intrahepatic portosystemic shunt in a 6-year-­ trast-enhanced computed tomography (CT) images of the abdomen old male. Sagittal grayscale (a) and color Doppler (b) ultrasound show the abnormal side-­to-­side connection (arrowheads) between the images demonstrate an abnormal connection (arrows) between the main main portal vein/proximal left portal vein and the intrahepatic IVC portal vein (asterisks) and the IVC (V). Axial (c) and sagittal (d) con-

Diffuse Parenchymal Disease Nonalcoholic Fatty Liver Disease Nonalcoholic fatty liver disease (NAFLD) encompasses the entire spectrum of fatty liver disease, defined by fat content exceeding 5% of the liver weight in the absence of secondary causes of hepatic fat accumulation. Nonalcoholic steatohepatitis (NASH) refers to the form of NAFLD where inflammation and hepatocyte injury are present. NASH can lead to fibrosis and cirrhosis, which are also included in the spectrum of NAFLD. NAFLD is the most common form of pediatric chronic liver disease in the industrialized world, and is associated with visceral adiposity, male sex, higher insulin levels, and Hispanic ethnicity [39]. It affects up to 10% of the general pediatric population and 80% of obese or overweight children [40].

Extreme malnutrition, exogenous steroids, and drugs such as amiodarone and methotrexate are additional causes of fatty liver. Most children are asymptomatic or have nonspecific complaints such as fatigue, malaise, and vague abdominal pain. Aspartate aminotransferase, alanine aminotransferase, and ultrasound are used to screen for NAFLD in obese children. Ultrasound findings of diffuse fatty liver (steatosis) include increased echogenicity of the liver relative to the normal right kidney, loss of echogenicity of the portal vein walls, attenuation of the ultrasound beam, and poor visualization of the diaphragm through the liver (Fig.  11.27). Diagnostic confidence increases with increasing severity of the fatty liver. Hepatomegaly is common. Areas of focal fatty sparing appear as hypoechoic foci in comparison to the surrounding echogenic, fatty liver, and at times may appear mass-like. Fatty sparing is often located along the porta hepatis, falciform ligament, or gall bladder fossa. On unenhanced CT, the fatty liver demonstrates hypoat-

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Fig. 11.27  Nonalcoholic fatty liver disease in a 17-year-old female. (a) Transverse and (b) sagittal grayscale ultrasound images show an enlarged, diffusely echogenic liver

tenuation, and measures less than 40 Hounsfield units (HU), or at least 10 HU less than the spleen. Several methods for assessing hepatic steatosis by MR imaging are also available. In-phase and opposed-phase MR imaging (also referred to as dual echo, or chemical shift imaging) can qualitatively and quantitatively estimate the fat fraction in the liver, with higher fat content areas demonstrating greater signal dropout on opposed-phase images. Multi-echo Dixon sequences to calculate proton density fat fraction and MR spectroscopy are two additional quantitative methods with a high degree of accuracy for evaluating fat content in the liver [41]. The mainstay of treatment of nonalcoholic fatty liver in children is lifestyle modification, including diet, exercise, and weight loss.

Liver biopsy, the traditional standard for assessing liver fibrosis, has limitations due to its invasiveness, complications, subjectivity, and sampling variability, hence the efforts to develop reproducible imaging-based techniques [43]. Mild liver fibrosis often has a normal imaging appearance. As fibrosis advances, some features will overlap with cirrhosis, the end stage of liver fibrosis. On ultrasound, the liver may demonstrate a coarse echotexture with variable hypertrophy or atrophy of hepatic segments (Figs.  11.28 and 11.29) [42]. Lace-like areas of hypoattenuation on CT and hyperintensity on MR imaging may be present. Focal confluent fibrosis may appear mass-like, and delayed hyperenhancement

Fibrosis Hepatic fibrosis refers to the excess deposition of proteins, including collagen fibers, in the extracellular matrix of the liver, in response to all causes of chronic liver inflammation and hepatocyte injury [42, 43]. This results in compression K of the portal venules and leads to portal hypertension. Early diagnosis and treatment of fibrosis may be reversible, whereas progression of fibrosis leads to cirrhosis [44]. Underlying causes of fibrosis that present in the pediatric and young adult population include biliary atresia, Fontan-­ associated liver disease (FALD), total parenteral nutrition (TPN)-associated liver fibrosis, Alagille syndrome, ciliopathies (including autosomal recessive polycystic kidney disease), cystic fibrosis, and NAFLD. Patients are often asymptomatic, Fig. 11.28  Hepatic fibrosis in a 17-year-old male with steatohepatitis. with liver disease detected during the workup or monitoring of Sagittal grayscale ultrasound image of the liver shows a coarsened, heterogeneous appearance of the parenchyma. K, Right kidney associated clinical entities [43].

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on MR imaging helps to differentiate fibrosis from hepatocellular carcinoma [42]. Fibrosis can be assessed by quantifying liver tissue stiffness with ultrasound or MR elastography techniques [42]. Both smaller (pSWE) (Fig.  11.30) and larger region of ­interest samples (2D SWE) of liver tissue can be evaluated in real-time. Imaging ultrasound elastography techniques have the added benefit of concurrent anatomic and morphologic assessment of the liver, with color maps demonstrating stiffness values on 2D SWE (Fig. 11.31).

MR elastography uses an external device placed on the patient’s right upper abdomen to generate shear waves in the liver and allows for the entire liver to be assessed by the generation of colorized wave images and quantitative elastograms. It should be noted that increased liver stiffness can be due to factors other than fibrosis, such as a postprandial state and right heart failure. In addition, patient breath-hold and operator scanning techniques may produce increased stiffness levels. Direct comparison of quantitative results of different methods has also been problematic due to lack of standardization between equipment manufacturers and techniques. A recent study that assessed

Fig. 11.29  Congenital hepatic fibrosis in a 20-month-old male with autosomal recessive polycystic kidney disease. Transverse grayscale ultrasound image shows an extremely heterogeneous and coarse appearance of the hepatic parenchyma consistent with fibrosis. Hepatic biliary ductal dilation (arrowheads) is also present, in keeping with Caroli disease

Fig. 11.30 Hepatic fibrosis in a 21-year-old female with Fontan-­ associated liver disease. Transverse ultrasound elastography image of the liver shows heterogeneous parenchyma. Point shear-wave elastography measurements are consistent with mild to moderate fibrosis

Fig. 11.31 Hepatic fibrosis in a 17-year-old female with Fontan-­ ness map (right). Two circular regions of interest placed within the associated liver disease. Oblique transverse 2D shear-wave elastogra- maps in the green zones indicate high confidence (left), with elevated phy ultrasound images of the right hepatic lobe demonstrates side-by-side stiffness levels (right). Note the coarse hepatic parenchyma display of the confidence map (left) and the corresponding color stiff-

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the repeatability and agreement of shear-wave speeds (SWSs) across six state-of-the-art ultrasound 2D SWE systems showed good to excellent intersystem agreement of measured SWS in elastic phantoms and in vivo livers [43]. Given the wide spectrum of insults that cause hepatic fibrosis, treatment is tailored to the underlying etiology.

Hemochromatosis Hemochromatosis refers to iron overload with an ­abnormal accumulation of iron in the body. Primary hemochromatosis (also referred to as genetic or hereditary hemochro­matosis) is an autosomal recessive disorder that leads to increased absorption of intestinal iron with symptoms typically developing adulthood. Secondary hemochromatosis refers to all other causes of iron overload, such as multiple red blood cell transfusions, excessive dietary intake, or normal dietary intake with increased absorption as can be seen with ineffective erythropoiesis accompanying certain liver diseases and inherited anemias. Excess iron may accumulate in the liver, pancreas, heart, skin, and synovium, leading to inflammation and fibrosis caused by reactive oxygen species. Patients may be asymptomatic or present with complaints of fatigue, skin hyperpigmentation, and arthralgias.

Fig. 11.32  Hemochromatosis in an 18-year-old female with Ewing sarcoma. Transverse (a) and sagittal (b) grayscale ultrasound images of the liver show mild, diffusely increased hepatic parenchymal echo-

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Ultrasound findings are not specific to hemochromatosis. Liver fibrosis and cirrhosis may be present, seen as increased or coarse echogenicity of liver parenchyma (Fig.  11.32). Unenhanced CT can demonstrate marked diffuse hepatic hyperattenuation. Dual-energy CT and gradient-echo MR imaging sequences with progressively increasing echo times (TEs) can be used to quantify iron deposition, which is qualitatively noted as low signal intensity on T2-weighted images. Venesection (phlebotomy) remains the mainstay of therapy.

Cirrhosis Cirrhosis represents the end stage of liver fibrosis due to progressive liver disease. Patients with cirrhosis are at risk of developing complications such as portal vein thrombosis, varices, hepatocellular carcinoma, and liver failure. The most common causes of cirrhosis in the first years of life are biliary atresia and genetic/metabolic diseases. In older children, cirrhosis is usually caused by chronic viral hepatitis and autoimmune disorders [45]. Patients may be asymptomatic, or present with abdominal distention, jaundice, gastrointestinal bleeding, hepatomegaly, and/or splenomegaly. Morphologic changes that can be detected with ultrasound, CT, and MR imaging include a nodular contour of

genicity. (c) Axial T2-weighted, fat-suppressed MR image shows generalized decreased signal throughout the liver and spleen consistent with secondary hemochromatosis

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Fig. 11.33  Cardiac cirrhosis in a 7-year-old male. Transverse grayscale ultrasound image shows a small liver (arrows) with an irregular contour. There is a large volume of ascites (asterisk)

Fig. 11.34  Viral hepatitis in a 7-year-old male. Transverse grayscale ultrasound image shows a diffusely hypoechoic liver with increased echogenicity of the portal triads (arrowheads) consistent with a “starry sky” appearance

the liver, right posterior lobe hepatic notch, and an enlarged gallbladder fossa (Fig. 11.33) [46–48]. Caudate lobe hypertrophy and segmental atrophy are attributed to alterations of intrahepatic blood flow [49]. The hepatic echotexture may be heterogeneous or coarse. Ultrasound findings associated with portal hypertension include slow hepatopetal or hepatofugal portal venous flow, splenomegaly, ascites, and varices associated with portosystemic shunts [46]. Regenerative, siderotic, or dysplastic liver nodules may develop; these are often poorly visualized by ultrasound and are better assessed with MR imaging where they are characterized by a lack of washout on delayed phase imaging. The treatment of cirrhosis is aimed at the underlying disorder and associated complications. Ultimately, liver transplantation may be needed.

hepatitis due to hepatitis B virus (HBV) and hepatitis C virus (HCV) may progress to chronic hepatitis, cirrhosis, and hepatocellular carcinoma [51]. Chronic infection occurs among 80%–90% of infected infants with 25% of them ultimately developing cirrhosis [52, 53]. The clinical presentation of viral hepatitis in children is variable, as patients may be asymptomatic or develop signs and symptoms such as fever, fatigue, abdominal pain, and jaundice. Findings of viral hepatitis on ultrasound are nonspecific and include hepatomegaly, decreased echogenicity of the liver with a relative increase in echogenicity of the portal vein walls (the so-called “starry sky” appearance) (Fig. 11.34), enlarged porta hepatis nodes, and gallbladder wall thickening [2, 54]. Similarly, periportal edema or hepatocyte edema may appear as hypodense areas on CT, or increased T2-weighted signal intensity on MR imaging with heterogeneous enhancement [55]. Imaging can also be normal in patients with acute hepatitis, or periportal lymphadenopathy may be the only imaging abnormality [54]. In chronic hepatitis, liver echogenicity may increase and become coarse or heterogeneous, with an appearance indistinguishable from fatty liver [55]. Treatment for acute HBV infection includes antiviral agents and supportive care. Universal vaccination of newborns is recommended in most countries and has resulted in a significant decrease in mother-to-child transmission [56].

Infection Viral Hepatitis A variety of viruses can infect the liver and cause hepatitis. In the newborn, herpes simplex virus (HSV) usually causes a severe multisystemic disorder with encephalitis and liver failure [50]. Cytomegalovirus (CMV) is the most common cause of congenital infection, affecting 1–2% of newborns, and may present with a petechial rash, hepatosplenomegaly, and jaundice [50]. Other viruses that can cause hepatitis include human immunodeficiency virus (HIV) and coxsackievirus. Infection of the liver with a hepatotropic virus can lead to a spectrum of conditions, from asymptomatic to fulminant hepatic failure, and persistent subclinical infection to rapidly progressive chronic liver disease and cirrhosis [51]. Acute

Bacterial Infection Bacterial infection of the liver is relatively rare compared with viral infection and most commonly manifests as liver abscess, acute bacterial hepatitis, or granulomatous liver disease (e.g., tuberculous liver disease and bartonellosis) [57]. Etiologies are typically polymicrobial and broad-spectrum, due to enteric

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pathogens entering the liver via the biliary tract, portal vein, hepatic artery, or direct extension from trauma or invasive procedures. Bacterial abscesses account for 75% of all liver abscesses in the developed world [58]. They are commonly caused by infections arising from the biliary tract (such as ascending cholangitis or cholecystitis), hematogenous spread (as through the hepatic artery in sepsis), or from portal vein pyemia in complicated abdominal infections (such as perforated appendicitis) [59]. Bacterial infections frequently occur in patients with acute-on-chronic liver disease and are associated with high mortality [60]. Symptoms are often nonspecific and include fever, abdominal pain, fatigue, and nausea. Abscesses may be unilocular, multilocular, and/or multifocal. At ultrasound, smaller hepatic abscesses (less than 2 cm in diameter) may appear as hypoechoic nodules or vague areas of altered echogenicity. Larger abscesses can range from hypoechoic to hyperechoic, depending on the internal contents (debris and/or thickened septa) and may even appear solid [59]. Posterior acoustic enhancement and the absence of internal blood flow by color Doppler may be useful to help differentiate an abscess from a solid neoplastic lesion (Fig. 11.35). CEUS can increase diagnostic confidence over grayscale ultrasound, with demonstration of an avascular, nonenhancing center, and peripheral enhancement without or with internal septal enhancement (Fig.  11.36). Notably, enhancing areas may demonstrate washout, a feature also seen in hepatic malignancy (Fig. 11.37) [61]. Confidence

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in the diagnosis is increased by the presence of gas within the abscess [59]. At contrast-enhanced CT, hepatic abscesses appear as welldefined, low-attenuation lesions with an enhancing rim [59]. A peripheral low-attenuation outer ring in the portal venous phase, representing perilesional edema (“double target” sign), may show enhancement on delayed phase imaging [59]. At MR imaging, abscesses typically demonstrate central T1-weighted hypointensity and T2-weighted hyperintensity, although their protein content may cause variation of this pattern [59]. The rim of the abscess demonstrates early and persistent enhancement, while perilesional edema appears as T2-weighted hyperintensity with enhancement in the delayed phase. Diffusion-weighted imaging (DWI) reveals restricted diffusion [62]. Organizing abscesses may mimic solid masses, with central granulation tissue that may occasionally demonstrate enhancement [63]. Acute bacterial hepatitis may appear normal or demonstrate nonspecific imaging findings. Granulomatous liver disease can have a variable appearance, including the absence of imaging abnormalities. Findings are nonspecific and include lesions of varying size which are commonly hypoechoic at ultrasound, hypoattenuating at contrast-­ enhanced CT, and hyperintense on T2-weighted MR imaging [59]. Therapy includes antibiotic treatment for the underlying disease. For liver abscesses, image-guided transhepatic percutaneous needle aspiration and/or catheter drainage are commonly employed, particularly in larger abscesses with a diameter greater than 5 cm [64].

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Fig. 11.35  Hepatic abscess in a 16-year-old male. (a) Traverse grayscale ultrasound image shows a complex bilobed, cystic intrahepatic fluid collection (arrows) in the right hepatic lobe that (b) demonstrates no internal flow on color Doppler evaluation

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Fig. 11.36  Hepatic abscess in a 9-month-old female with septic shock. Transverse CEUS image shows a hypoechoic lesion in the right lobe of the liver with increased through transmission on the reference grayscale image (left panel) that demonstrates no internal flow (right panel)

Fig. 11.37  Hepatic abscess in a 16-year-old male with fungal infection. (a) Longitudinal CEUS image of the liver obtained in the late phase of enhancement shows a well-circumscribed, unenhancing focus (arrow) with a thick hypoenhancing rim in keeping with an abscess.

(b) Longitudinal CEUS image obtained in the portal venous phase of enhancement 3 months later shows internal enhancement (arrow), consistent with healing

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Fungal Infection

more lesions than imaging performed during other phases, with an increase in the number of identifiable hyperenhancing foci Hepatic fungal infection occurs in patients with prolonged [67]. Hypoattenuating lesions are usually seen on portal phase neutropenia and immunosuppression or immunodeficiency imaging, with enhancement patterns varying depending on the due to medical disorders or medication. Very low birth-­ phase of contrast injection and stage of disease [68]. MR imagweight (less than 1500 g) and extremely premature neonates ing features include a T2-weighted hyperintense lesion with a are also at increased risk [65]. Candida species, Aspergillus nonenhancing center representing necrosis that gradually species, and Cryptococcus neoformans account for 80% of resolves with treatment [67]. Fungal abscesses may demonall fungal infections [66]. Hepatic infection often occurs in strate restricted diffusion on diffusion-weighted images [62]. conjunction with splenic involvement. Due to challenges in accurate and prompt diagnosis of Clinical manifestations such as fever, abdominal pain, fungal infections, the use of empiric antifungal agents in jaundice, and hepatomegaly are nonspecific and overlap with febrile neutropenic patients has been advocated [69]. Hepatic other invasive infections. Blood cultures have a high false- candidiasis can be refractory to conventional therapy or negative rate and reluctance to perform invasive diagnostic require an extensive course of antifungal therapy [67]. procedures in affected patients makes the diagnosis of invasive fungal disease challenging [67]. Therefore, imaging plays a critical role in prompt detection and initiation of therapy. Parasitic Infection The imaging features of fungal diseases share similar characteristics and are not useful for identifying a specific pathogen. A variety of parasites may infect the liver, and generally Microabscesses are the characteristic pattern of disease by both demonstrate nonspecific imaging findings, with the excepimaging and histology (Fig. 11.38). tion of amebic abscess and echinococcal cyst. Although parAt ultrasound, four patterns of hepatosplenic candidiasis asitic hepatic infection is most problematic in endemic areas have been described: hypoechoic nodule (most common, but in the developing world, its incidence is increasing due to least specific); echogenic focus (2–5 mm, seen late in disease tourism and human migration [70]. and representing areas of calcification); bull’s-eye (hyperechoic The most common extraintestinal complication of inner inflammatory nidus with a peripheral hypoechoic ring of Entamoeba histolytica infection is amebic liver abscess [68]. fibrosis, generally seen with active infection); and “wheel within Ingested pathogens colonize the colon and then travel to the a wheel” (the bull’s-eye appearance with an additional central liver via the portal venous system. Symptoms include malhypoechoic nidus representing necrosis, seen early in the course aise and right upper quadrant pain. Diagnosis is aided by of disease) [68]. stool sample or blood serum analysis [71]. CT and MR imaging are superior to ultrasound for the idenThe imaging appearance of amebic abscess is classically tification of fungal hepatic lesions [67]. Specifically, arterial unilocular and solitary in the right hepatic dome, but otherphase imaging at CT and MR imaging depicts significantly wise indistinguishable from a pyogenic abscess [68, 72].

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Fig. 11.38  Hepatosplenic candidiasis in a 6-year-old female. Transverse grayscale ultrasound images of the liver (a) and spleen (b) show multiple tiny hypoechoic lesions (arrowheads)

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Larger abscesses are at risk for spontaneous rupture and can lead to the development of pericardial, pleural, or perihepatic fluid collections [73]. Metronidazole therapy is the mainstay of medical treatment for amebic abscess [68]. In uncertain cases, aspiration or percutaneous drainage aids in identification of the causative pathogen and treatment. Amebic abscesses may take up to 2 years to resolve on imaging [68, 72]. Hydatid disease develops after the ingestion of Echi­ nococcus granulosus found in contaminated food, water, and soil [68]. Embryos invade the bowel mucosa and travel to the

liver via the portal system. As the cyst matures in the liver, the inner germinal layer (endocyst) invaginates to develop daughter cysts within the parent cyst, pathognomonic for hydatid disease. At ultrasound, the appearance of a hydatid cyst ranges from anechoic to diffusely echogenic (Figs. 11.39 and 11.40) [68]. Smaller daughter cysts of varying size can be identified and may rupture and become detached, appearing as floating membranes (“water lily” sign) [68]. Intrabiliary rupture is a common complication and may lead to biliary distortion and dilation. Shadowing, echogenic foci representing varying b

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Fig. 11.39  Hepatic hydatid disease in an 18-year-old female. Transverse grayscale ultrasound image of the liver (a) shows a well-circumscribed, echogenic mass with (b) no internal vascularity by color Doppler

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Fig. 11.40  Hepatic hydatid disease in a 16-year-old male. (a) Transverse grayscale ultrasound image shows a well-circumscribed hypoechoic mass in the liver which demonstrates increased through transmission. (b) Transverse color Doppler ultrasound image shows no internal vascularity

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degrees of calcification may be present in the periphery of the cyst, usually indicative of nonviability [68]. CT demonstrates a well-defined, hypoattenuating lesion, often with internal daughter cysts that may be of lower density than the parent cyst [68]. MR imaging demonstrates hyperintense T2-weighted and hypointense T1-weighted parent and daughter cysts, although some variation may be seen due to internal debris. The peripheral layer of the cyst is hypointense on T1- and T2-weighted images, due to fibrous and calcified components. Treatment of hydatid cysts includes the administration of antiparasitic drugs, percutaneous drainage and instillation of a sclerosing agent within the cystic cavity, and surgical excision [68].

Trauma Blunt Abdominal Trauma The liver is the most frequently injured organ in blunt abdominal trauma and is often seen in conjunction with other organ injuries [74]. Hepatic lacerations involve the capsule and are associated with hemoperitoneum. Hematomas may be intraparenchymal or subcapsular. Bile duct and major hepatic vascular injuries may also occur. Common causes include motor vehicle collisions, pedestrian accidents, falls, and sports injuries [75]. Point-of-care emergency extended focused assessment with sonography in trauma (e-FAST) ultrasound imaging may be used in unstable patients to depict free fluid indicating hemoperitoneum that can develop secondary to hepatic laceration [74]. Standard grayscale ultrasound is of limited

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diagnostic accuracy for hepatic injury and may depict vague areas of near-isoechogenicity or hyperechogenicity and free fluid [3, 76]. Conversely, CEUS has demonstrated promise in improving the diagnostic accuracy of ultrasound, comparable to that of the gold-standard CT [3, 74, 75, 77]. By both CT and CEUS, traumatic hepatic lesions appear as areas of hypo-enhancement or nonenhancement of varying size, shape, and location within the liver, depending on the nature and force of the injury (Figs. 11.41 and 11.42) [3, 76]. On CEUS, active bleeding may present as mobile foci of increased echogenicity within an anechoic or hypoechoic lesion [74]. Nonoperative management is the mainstay of treatment in most hemodynamically stable children [78]. Interventional procedures such as angioembolization are performed for hepatic arterial hemorrhage. Laparotomy may be necessary in patients with peritonitis or hemodynamic instability. Delayed complications include hemorrhage, abscess, pseudoaneurysm, and bile leakage, many of which can be treated by interventional radiologic techniques [79].

Umbilical Vein Catheterization The umbilical vein is commonly used for central venous access in neonates. An umbilical vein catheter (UVC) normally courses from the umbilical vein to the left portal vein, through the ductus venosus and hepatic venous confluence toward the right atrium, with the tip ideally located at the inferior cavoatrial junction [27, 80, 81]. A malpositioned UVC can perforate the vessel wall, leading to liver parenchymal injury or hematoma and extravasation of infused fluids

Fig. 11.41  Liver laceration in a 13-year-old male who sustained blunt abdominal trauma. Reference transverse grayscale ultrasound image (left panel) shows a faint hypoattenuating focus (arrow) in the liver that is more conspicuous (arrowhead) by CEUS (right panel)

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Fig. 11.42  Liver laceration in a 9-year-old male. Reference sagittal grayscale ultrasound image (left panel) shows a faint linear hypoattenuating focus (arrow) in the liver which becomes more conspicuous (arrowhead) by CEUS (right panel)

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Fig. 11.43  Malpositioned umbilical vein catheter (UVC) in an 8-day-­ old male with extravasation of infused total parenteral nutrition (TPN) fluids. (a) Frontal chest radiograph shows an abnormal lateral position of the UVC tip (arrow). (b) Sagittal color Doppler ultrasound image

shows two well-circumscribed, avascular, heterogeneously hyperechoic foci (arrowheads) in the right lobe of the liver consistent with complex fluid collections. A large amount of ascites (asterisk) is present

[27, 82]. Symptoms include unexplained acute clinical deterioration, hypotension, drop in hematocrit, and abdominal distension due to hepatomegaly or ascites [80]. Ultrasound may demonstrate an intrahepatic or subcapsular fluid collection that can be anechoic or complex, depending on the contents of the extravasated fluid and the

duration of injury. Lesion size, shape, and echogenicity can be variable [81]. Some lesions may be echogenic and lobulated or branching in configuration [80]. Internal flow will be absent on Doppler evaluation (Fig. 11.43). Due to the location of the umbilical vein and ductus venosus, abnormalities are more commonly seen in the left hepatic

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lobe and can be associated with left portal vein thrombosis [80]. Foci of air and calcification may be detected within the fluid collection by ultrasound or radiography in the subacute and late stages of UVC perforation [27]. Additional radiographic findings include an enlarging hepatic silhouette or mass effect secondary to the fluid collection. Management is conservative. After removal of the misplaced catheter, the fluid collection often resolves with time [27]. In cases of severe abdominal distension or mass effect, paracentesis or drainage of fluid from the intrahepatic or perihepatic collection may speed recovery.

Portal Hypertension Portal hypertension refers to the pathologic increase in portal venous pressure due to obstruction of flow that may occur at the presinusoidal level (e.g., portal vein thrombosis, umbilical vein catheterization, prothrombotic disorders, extrinsic compression of the portal vein); sinusoidal level (e.g., cirrhosis); or postsinusoidal level (e.g., right heart failure, IVC obstruction) (Table 11.3) [83, 84]. Portal vein thrombosis is the most common cause of extrahepatic portal vein obstruction and is a major cause of portal

hypertension in children [85]. In approximately half of cases, the etiology is idiopathic [83, 84, 86]. In the absence of underlying hepatic parenchymal disease, patients with portal hypertension frequently present with upper gastrointestinal bleeding due to ruptured gastric and esophageal varices [86]. Splenomegaly with or without hypersplenism is also a common clinical manifestation. Younger patients may experience growth retardation. Portosystemic varices may manifest clinically as dilated abdominal wall veins (“caput medusae”) and hemorrhoids. Ultrasound with Doppler evaluation of portal hypertension may reveal enlargement of portal venous diameter and decreased velocity or reversal of flow (hepatofugal flow) within the portal veins (Fig.  11.44) [87]. Acute portal vein thrombosis may appear as an anechoic filling defect within the portal vein, best detected with color Doppler imaging, while chronic thrombus appears more echogenic. Over time, tortuous portal vein collaterals (also known as cavernous transformation of the portal vein) may develop and appear as an irregular tangle of vessels at the porta hepatis, well ­visualized with color Doppler imaging [84, 86]. A recanalized umbilical vein or enlarged paraumbilical vein may be seen in the area of the falciform ligament [87]. Other associated findings include splenomegaly, ascites, and liver cirrhosis. Ultrasound elastography is emerging as a

Table 11.3  Causes of portal hypertension Hepatic Presinusoidal Granulomatous disease Portal vein thrombosis Umbilical vein catheterization Lymphomas Splenic or superior mesenteric Polycystic liver disease Chronic hepatitis vein thrombosis Schistosomiasis Prothrombotic disorders Extrinsic compression of portal Primary biliary cirrhosis Primary sclerosing vein cholangitis Partial or complete agenesis of Cystic fibrosis portal vein Liver disease Prehepatic

Post-hepatic Sinusoidal Cirrhosis Congenital hepatic fibrosis Biliary atresia NAFLD Viral hepatitis Hemochromatosis Wilson disease Peliosis hepatitis

Post-sinusoidal Sinusoidal obstruction syndrome Chemotherapy Hematopoietic stem cell transplant

Budd–Chiari syndrome (hepatic vein obstruction) Inferior vena cava obstruction Right heart failure Tricuspid regurgitation Constrictive pericarditis

NAFLD, Nonalcoholic fatty liver disease

a

Fig. 11.44  Portal hypertension in an 18-year-old male. (a) Oblique transverse color Doppler ultrasound image of the main portal vein with spectral analysis shows reversed (hepatofugal) flow. (b) Sagittal gray-

b

scale ultrasound image reveals marked splenomegaly and hilar varices (arrow), secondary signs of portal hypertension

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noninvasive screening tool for portal hypertension in patients with chronic liver disease [83, 88, 89]. CT and MRI performed with intravenous contrast agents also provide visualization of the presence and extent of portal vein thrombosis, portosystemic collateral vessels and varices [87]. Management requires treatment of the underlying cause of portal hypertension and its complications. Strategies include pharmacologic, endoscopic, interventional radiologic, and surgical approaches [85, 86]. Gastrointestinal variceal bleeding is treated by endoscopic band ligation. Extrahepatic portal venous obstruction in patients with refractory variceal bleeding can be treated by the creation of a surgical Rex shunt (mesoportal bypass) to restore hepatopetal portal perfusion [85]. Interventional radiology procedure options include thrombectomy, angioplasty, and transjugular intrahepatic portosystemic shunt (TIPS) creation [83, 90]. Patients with end-stage liver disease and portal hypertension may require liver transplantation [83].

Budd–Chiari Syndrome Budd–Chiari syndrome (BCS) refers to the spectrum of clinical manifestations caused by hepatic venous outflow obstruction occurring at any level from the small hepatic veins to the inferior cavoatrial junction [91, 92]. Primary BCS is due to intrinsic causes of venous obstruction, such as thrombus or membranes, whereas secondary BCS is due to extrinsic causes, such as compression by tumor, abscess, or hyperplastic nodules [93]. Hypercoagulable states account for the majority of cases [93, 94]. BCS is an example of postsinusoidal portal hypertension, where hepatic vein occlusion leads to increased sinusoidal and

a

Fig. 11.45  Budd–Chiari syndrome in an 8-year-old male. (a) Transverse grayscale ultrasound image shows a markedly thickened gallbladder wall (arrowheads) and ascites (asterisk). (b) Transverse color Doppler ultra-

portal pressure [92]. The severity of clinical presentation is dependent on the duration and extent of obstruction. Patients with only a single t­hrombosed hepatic vein may be asymptomatic. With extensive venous outlfow obstruction, hepatocellular hypoxia may result in necrosis and fulminant liver failure [92]. Patients may present acutely with fever, right upper quadrant pain, hepatomegaly, coagulopathy, ascites, and renal failure [95]. Insidious progression of hepatic vein obstruction may lead to fibrosis and eventual cirrhosis. Chronic BCS may present with additional manifestations of portal hypertension, such as progressive abdominal distention due to ascites and splenomegaly (Fig. 11.45) [92, 93]. On grayscale ultrasound imaging, acute thrombosis of the hepatic veins or IVC may appear anechoic or hypoechoic, with documentation of absent flow greatly aided by color and spectral Doppler evaluation. In the setting of thrombus, flow may be absent, slow, retrograde, or bi-directional. An obstructing membrane may appear as a linear echogenic structure within the vessel lumen. This membrane, or other focal narrowing, may cause abrupt cutoff of flow, turbulent flow, or focally increased flow velocities. Proximal to the site of obstruction, loss of phasicity of the venous spectral waveform may be demonstrated. In other instances, the hepatic veins may not be visualized due to extrinsic compression, or they may appear echogenic and cord-like. Over time, intrahepatic and extrahepatic venovenous collateral vessels may develop, appearing as enlarged, tortuous, abnormally located vascular channels [93]. Other ultrasound findings include compensatory enlargement of the caudate lobe, with an enlarged caudate vein draining directly into an unobstructed IVC. The parenchyma of the liver segments affected by hepatic vein thrombosis may acutely appear hypoechoic due to congestion and edema, or heterogeneous due to infarction or fibrosis with or without regenerative nodules. Splenomegaly and ascites are also commonly seen in BCS [92].

b

sound image of the liver with spectral analysis shows a recanalized umbilical vein (arrow) with hepatofugal flow. No flow was detected in the hepatic veins (not shown)

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CT and MR imaging will demonstrate the same morphologic features depicted by ultrasound. Following intravenous contrast administration, there will be a lack of enhancement of thrombosed vessels and corresponding hepatic segments [93, 96]. Liver parenchymal findings include patchy, decreased peripheral enhancement due to stasis in the hepatic sinusoids and portal veins, with relatively increased enhancement in the central portions of the liver and the caudate lobe [92, 93, 97]. On T2-weighted MR imaging, heterogeneously increased signal intensity is seen in the liver periphery. Diagnostic catheter venography is performed prior to interventional procedures and may demonstrate occlusion or stenosis of the hepatic veins or IVC, large intrahepatic collateral vessels, or a spiderweb-like appearance of smaller collaterals [92, 98, 99]. Initial treatment options include angioplasty, stent placement, and catheter-directed thrombolysis [100]. Transjugular intrahepatic portosystemic shunt (TIPS) creation and liver transplantation have improved mortality in recent years [92, 101]. Long-term anticoagulation is often required in most patients with BCS due to an underlying hypercoagulable state [101]. a

Sinusoidal Obstruction Syndrome Sinusoidal obstruction syndrome (SOS), previously known as veno-occlusive disease (VOD), is a disorder that causes venous outflow obstruction in the liver due to epithelial injury and sinusoidal obstruction. First recognized in patients who ingested toxic plant alkaloids, SOS has been reported in up to 77% of patients who have undergone hematopoietic stem cell transplantation (HSCT) [102]. Patients receiving chemotherapy and immunosuppression without HSCT have also been affected. Classically, patients present with painful hepatomegaly, weight gain, and ascites within the first 21  days following HSCT, but novel therapies have led to an increase in lateonset disease [103]. Advanced disease may lead to fibrosis or the rapid onset of multi-organ failure [104]. Ultrasound, MR imaging, and CT may all show hepatomegaly, ascites, and gallbladder wall thickening, which are nonspecific findings (Fig. 11.46) [104, 105]. Elevated hepatic artery resistive indices can also be demonstrated. While reversal of portal venous flow with Doppler ultrasound is diagnostic, it is usually only present in the late stages of the b

c

Fig. 11.46 Sinusoidal obstruction syndrome in an 18-month-old female. (a) Transverse grayscale ultrasound image shows gallbladder wall thickening (arrowhead) and a small amount of ascites (arrows).

Oblique transverse color Doppler ultrasound images with spectral analysis show (b) diminished diastolic flow in the hepatic artery with an elevated resistive index (RI), and (c) pulsatile flow in the main portal vein

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disease and its absence does not exclude SOS.  Therefore, diagnosis is largely based on clinical criteria [105]. Aggressive fluid management is essential in treating SOS. Mild cases can be managed with supportive measures only. Defibrotide is the only approved agent for the treatment of SOS in children and adults. Its mechanism of action is not completely understood, but it is believed to play a role in endothelial protection. High-dose steroids are also of benefit [105].

Peliosis Hepatis Peliosis hepatis is a rare, benign vascular condition of the liver characterized by dilated sinusoidal spaces, with or without an endothelial lining, resulting in blood-filled cystic ­cavities of varying size, ranging from 1 mm to several cm [106]. Other organs, such as the spleen and bone marrow, can also be involved. While the pathogenesis of peliosis hepatis remains unclear, hepatocellular necrosis and sinusoidal damage likely play a role. It is associated with a variety of conditions, including drug-­related (steroids, chemotherapeutic agents, oral contraceptives, azathioprine), immunosuppression (posttransplantation or hematologic disorders), and infection (tuberculosis, HIV, and Bartonella henselae). Rare pediatric associations include X-linked myotubular myopathy, Escherichia coli sepsis, and cystic fibrosis. In 20–50% of patients, no risk factor is identified [106]. Peliosis hepatis is often discovered incidentally on imaging or autopsy, as many patients are asymptomatic. Abdominal pain, cholestasis, hepatomegaly, portal hypertension, or liver failure may be present. Larger lesions can rupture, leading to intrahepatic hemorrhage or hemoperitoneum and hypovolemic shock [106].

Fig. 11.47  Peliosis hepatitis in a 20-year-old female with a history of liver transplantation. (a) Transverse grayscale ultrasound image shows multiple small, round, echogenic foci (arrowheads) throughout the right lobe of the liver. (b) Axial T2-weighted, fat-suppressed MR image shows multiple tiny hyperintense foci in the right lobe of the liver which

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Imaging findings are nonspecific and variable, based on the size and number of the lesion cavities, the physical state of the blood components, and the presence of hepatic steatosis. Innumerable small lesions or several large cystic cavities may be present. On ultrasound, lesions tend to be hyperechoic, although they may appear hypoechoic in the setting of hepatic steatosis, or heterogeneously hypoechoic due to internal hemorrhage (Fig.  11.47) [106]. Doppler imaging may reveal peri- or intra-lesional vascularity. At CEUS, peliotic lesions may demonstrate an early arterial central enhancement compatible with a target-sign pattern, followed by centrifugal filling and homogeneous enhancement comparable to that seen at contrast-enhanced CT and MR imaging [107]. Unenhanced CT typically demonstrates a hypoattenuating lesion, although hemorrhage and calcification may increase attenuation. On MR imaging, lesions usually appear hyperintense on T2-weighted images, and hypointense on T1-weighted images, although hyperintense T1- and T2-weighted foci may represent foci of hemorrhage [106]. Thrombosed cavities may only enhance peripherally, mimicking the appearance of an abscess. In some instances, centripetal enhancement is reminiscent of the appearance of a hemangioma. Some lesions may mimic liver tumors, although the lack of mass effect with peliosis hepatis helps to differentiate between them. Lesions smaller than 1 cm may go undetected. When associated with an offending agent, peliosis hepatis may resolve with discontinuation of the medication or treatment of infection [106]. Due to the potential for serious complications, periodic surveillance or surgical resection should be considered. Successful transcatheter embolization in the emergent setting of massive hemorrhage has been described [108].

are not in continuity with the biliary tree. These foci did not enhance on the arterial or early portal venous phases of the study. Enhancement was identified on delayed imaging (not shown). Subsequent biopsy confirmed peliosis hepatitis

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Passive Venous Congestion Passive venous congestion of the liver, also known as congestive hepatopathy, refers to the spectrum of liver abnormalities that are due to any cause of right heart failure and elevated central venous pressure (CVP) [108]. The elevated CVP is transmitted to the hepatic vessels, leading to sinusoidal dilation and congestion, perisinusoidal hemorrhage, thrombosis, and fibrosis [109]. The mottled gross pathological appearance of the liver with passive venous congestion has been described as a “nutmeg liver,” caused by nodular zones of red cell accumulation. Chronicity may lead to the development of focal nodular hyperplasia, cirrhosis, and hepatocellular carcinoma [109, 110]. Children and adolescents with congenital heart disease and single-ventricle anatomy who undergo palliative Fontan reconstruction, whereby systemic venous return bypasses the right ventricle and passively flows to the pulmonary arteries, are becoming an increasingly significant group of patients who require screening for liver disease [110]. Symptoms relating to the underlying cardiac disease typically dominate; dull right upper quadrant pain and mild elevation of liver enzymes may be present. Ultrasound findings include a dilated IVC and dilated hepatic veins (Fig. 11.48) [109]. Spectral Doppler evaluation may reveal diminished respiratory variation along with dampening or loss of the normal tetraphasic hepatic venous waveform [109]. Acute congestion may result in hepatomegaly while chronic congestion can lead to cirrhosis with a nodular liver contour, splenomegaly, and ascites. In the setting of high right atrial pressures, CT with contrast administered via an upper extremity vein may demonstrate early enhancement of the IVC and hepatic veins due to reflux of contrast material [109]. Patchy enhancement of

Fig. 11.48  Passive venous congestion in a 20-month-old female with right-sided heart failure. Transverse grayscale ultrasound image of the liver shows engorged hepatic veins (arrowheads) and ascites (asterisk)

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the liver parenchyma with reticular areas of hypoenhancement is noted particularly in the liver periphery during the portal venous phase, with corresponding T2 hyperintensity on MR imaging. Delayed MR imaging using a hepatocytespecific contrast agent can show nonenhancing linear or reticular bands representing fibrous septa next to the hepatic veins with sparing of the regions next to the portal triads. Periportal edema manifests as periportal tracks of hypointensity on CT, hyperintensity on T2-weighted images, and delayed phase enhancement. Hypervascular nodules may be present. Ultrasound and MR elastography are useful in detecting increased liver stiffness due to venous congestion, particularly in the liver periphery, but cannot otherwise differentiate between congestion, fibrosis, and other causes of increased liver stiffness. There is no specific treatment for passive venous congestion. Therapy is aimed at treating the underlying cardiac disease, including cardiac transplantation. Diuretics and pulmonary vascular vasodilator therapy may be beneficial [111].

Portal Venous Gas Portal venous gas can be seen in a variety of conditions, ranging from benign to life-threatening [112]. Gas may enter small or large intestinal veins via a compromised mucosa, or as a result of increased intraluminal pressure, and subsequently travel to the portomesenteric venous system [113]. In children, portal venous gas is commonly associated with pneumatosis intestinalis resulting from necrotizing enterocolitis in premature infants, or occurs secondary to umbilical vein catheterization [1, 114]. Portal venous gas can be seen in other conditions with or without vascular compromise, bowel ischemia, or bowel mucosal injury, such as intraabdominal infection, inflammatory bowel disease, bowel dilation, following an interventional procedure or after steroid administration. Uncommon causes include occult child abuse [115], liver transplantation [116], and hypertrophic pyloric stenosis [117]. Ultrasound has a high sensitivity for the detection of portal venous gas [114]. On grayscale images, it appears as punctate or short linear, echogenic foci oriented in a branching configuration (Figs.  11.49 and 11.50). The echogenic foci may be mobile, traveling toward the liver periphery and conforming to the course and direction of blood flow within portal veins [114, 118]. The typically peripheral location helps to differentiate portal venous gas from air in the biliary tree (pneumobilia), which is more centrally located within the liver. Duplex Doppler ultrasound shows mobile echogenic foci within the lumen of the portal vein, producing sharp bidirectional spikes superimposed on the normal monophasic portal

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Fig. 11.49  Portal venous gas in a premature 4-day-old male with complex congenital heart disease. Transverse grayscale ultrasound image shows multiple punctate echogenic foci (arrowheads) in a linear distribution in the left lobe of the liver

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Fig. 11.50  Portal venous gas in a premature 12-day-old female with necrotizing enterocolitis and abdominal distention. Transverse grayscale ultrasound image shows echogenic foci (arrow) in the main portal vein and diffusely throughout the liver within distal intrahepatic portal venous branches

b

Fig. 11.51  Congenital liver hemangioma in a 1-day-old female. (a) Transverse grayscale ultrasound image of the liver shows a large, multilobulated, soft tissue mass in the right hepatic lobe that contains

numerous internal anechoic tubular structures. (b) Color Doppler ultrasound image reveals multiple enlarged vessels surrounding and extending into the mass

venous wave pattern [114]. Radiographically, portal venous gas appears as peripheral branching lucencies in the liver; similarly, on CT, branching air-density foci are demonstrated in the portal vein and its branches, often predominantly in the left hepatic lobe. Treatment for portal venous gas is aimed at the underlying cause and may include antibiotics, bowel decompression, and urgent laparotomy.

Tumors Benign Masses Congenital Hemangioma Congenital hemangioma (CH) is a rare, benign vascular tumor that is typically focal and fully grown at birth (Fig.  11.51, Tables 11.4 and  11.5). CHs occur in the liver but are more

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Table 11.4  Characteristics of liver masses in children Typical ultrasound Age of presentation appearance

Entity Benign Hemangioma, congenital (CH), and infantile (IHH)

First year of life

Mesenchymal hamartoma

Less than 2 years

Focal nodular hyperplasia

Varies

Hepatic adenoma

Adolescence Hyperechoic with internal heterogeneity

Malignant Hepatoblastoma Less than 5 years

Hepatocellular carcinoma (HCC)

Contrast-enhanced ultrasound features

Calcification/ Hemorrhage

+ (CH, if large) Arterial peripheral Hyperechoic with nodular enhancement prominent with gradual central vascular filling channels, IHH may be multifocal Minimal enhancement – (uncommon) Predominantly cystic with septations, internal low-level echoes – (uncommon) Early arterial Isoechoic or enhancement of a hypoechoic, feeding vessel, spoke may have a wheel pattern central scar

AFP levels

Elevated initially Low birth weight, (CH) cutaneous hemangioma, PHACES syndrome, hypothyroidism (IHH) Normal (can be Typically isolated, DICER1 gene mildly mutation may elevated) predispose to other malignancies Normal Prior chemotherapy, hereditary hemorrhagic telangiectasia, portosystemic shunt Normal Oral contraceptives, anabolic steroids, glycogen storage disease type I, FAP, Hurler syndrome

Rapid arterial hyperenhancement with centripetal filling, isoechoic or rare washout on delayed phases

++

Early arterial Heterogeneous, hyperenhancement cystic and solid, with washout on portal or hepatic portal venous phase vein invasion

++

Elevated

+

Elevated

Early arterial Over 5 years Heterogeneously hyperenhancement hypoechoic, but with washout on may be mixed portal venous phase or hyperechoic

+ Heterogeneous arterial Adolescence Heterogeneous, enhancement with central washout on portal echogenic venous phase strands, may be multifocal Solid with areas of Nonspecific/limited data – (uncommon) Undifferentiated 6–10 years cystic change or embryonal necrosis sarcoma

Fibrolamellar HCC

Associations

Usually normal

Normal

Prematurity, very low birth weight, Beckwith– Wiedemann, FAP, glycogen storage disease type IA Perinatal HBV infection, biliary atresia, hemochromatosis, glycogen storage disease type I, Wilson disease, hereditary tyrosinemia None identified

Rarely may arise within existing mesenchymal hamartoma

AFP, Alpha-fetoprotein; CH, congenital hemangioma; FAP, familial adenomatous polyposis; HVB, hepatitis B virus; IHH, infantile hepatic hemangioma Table 11.5  Characteristics of liver hemangiomas Type Subtype Growth Involution GLUT-1 Focality

Congenital Rapidly involuting (RICH) Fully grown at birth Typically involutes by 14  months Negative Unifocal

GLUT-1, Glucose transporter protein-1

Non-involuting (NICH) Partially involuting (PICH) Grows proportionately with child Fully grown at birth None Initial regression followed by stability of size Negative Negative Unifocal Unifocal

Infantile Infantile hemangioma (IHH) Proliferates in the first year of life Slow regression up to 10 years Positive Typically multifocal/diffuse

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c

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d L

A

Fig. 11.52  Rapidly involuting congenital liver hemangioma (RICH) in a 2-month-old male. (a) Transverse grayscale ultrasound image shows a large, heterogeneous right hepatic lobe mass containing anechoic tubular structures and focal calcification. The mass is smaller when compared to prior studies (not shown). (b) Transverse color Doppler ultrasound image

shows marked hypervascularity of the lesion (c) Transverse color Doppler ultrasound image with spectral analysis reveals low resistance arterial flow within the mass. (d) Sagittal grayscale ultrasound image shows marked tapering of the abdominal aorta (A) below the level of the liver (arrow) due to arteriovenous shunting within the mass. L, Liver

often identified in the skin or subcutaneous tissues of the head and neck region and lower extremities. Three subtypes have been recognized: rapidly involuting congenital hemangioma (RICH), which typically involutes completely by 14 months of age (Fig.  11.52); noninvoluting congenital hemangioma (NICH), which does not regress, but grows proportionately with the child’s overall growth; and partially involuting congenital hemangioma (PICH), which undergoes initial growth regression followed by stabilization (Fig. 11.53) [119–122]. Immunostaining for glucose transporter protein-1 (GLUT1) is an important differentiator between CH, which is GLUT-1 negative, and infantile hepatic hemangioma (IHH), which is a

separate entity with distinctive clinical features and GLUT-1 positivity [123, 124]. Serum alpha-fetoprotein (AFP) levels may be elevated initially but should subsequently decrease. Hepatic CH may be detected prenatally or incidentally, and most are asymptomatic. Larger CH may present as an abdominal mass in an otherwise healthy infant. Transient thrombocytopenia and anemia occur some infants. High-output heart failure can develop in infants with large CH, due to arteriovenous shunting through the tumor and cardiac overload [123]. Most CHs are unifocal, whereas IHH is more commonly multifocal or diffuse (see further discussion of IHH in Section “Infantile Hemangioma”).

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b

a

c

d

f

e

g

Fig. 11.53  Partially involuting congenital liver hemangioma (PICH) in a 2-month-old male. Serial follow-up showed partial involution that then stabilized. (a) Transverse grayscale ultrasound image of the right hepatic lobe demonstrates a large, heterogeneous mass with internal tubular and round anechoic structures consistent with prominent vascular channels or areas of intralesional hemorrhage. (b) Longitudinal power Doppler ultrasound image of the right hepatic lobe demonstrates blood flow at the periphery and within the mass (c) Longitudinal CEUS image obtained during the early arterial phase demonstrates a nodular, hyperenhancing periphery (white arrowheads). (d) Longitudinal CEUS image obtained

during the early arterial phase one second after the image in (c) demonstrates further centripetal enhancement of the mass (white arrowheads). (e) Longitudinal CEUS image obtained during the portal venous phase demonstrates near-complete enhancement of the mass. Small, persistent, central unenhancing foci represent intralesional bleeding, thrombus, and/ or fibrosis. (f) Axial contrast-enhanced, T1-weighted, fat-suppressed MR image shows thick, peripheral and heterogeneous central enhancement of the hemangioma. (g) Axial T2-weighted, fat-suppressed MR image shows diffuse hyperintensity of the lesion with central hypointense flow voids

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On ultrasound imaging, features common to both types of hemangioma include well-circumscribed solid tissue that may appear hyperechoic, hypoechoic, or of mixed echogenicity with prominent vascular channels. CH often demonstrates focal calcifications and macroscopic arteriovenous shunting. Doppler examination will reveal low-­resistance, high-velocity arterial flow. On CEUS, CT, or MR imaging, there is arterial peripheral nodular enhancement with gradual central filling and diffuse enhancement with lack of washout on delayed imaging. In smaller lesions, the fill-in is more rapid and may appear instantaneous, probably due to the abundant arteriovenous shunts [125]. For CH, exceptions to the typical pattern of diffuse enhancement may occur in the setting of intralesional bleeding, thrombosis, fibrosis, or coarse calcification, resulting in a heterogeneous, solid and cystic appearance [126]. On MR imaging, lesions demonstrate T2-weighted hyperintensity and T1-weighted hypointensity, and flow voids may be identified. Arteriovenous shunting may result in enlargement and increased flow velocity of hepatic arteries and veins associated with the hemangioma, and tapering of the aorta distal to the celiac trunk [1, 122, 123, 127]. RICH will eventually completely involute, often leaving only a clump of coarse calcifications. RICH typically involutes by the age of 14  months, and treatment is not usually necessary. For symptomatic patients, propranolol is the mainstay of medical therapy. Continued monitoring for at least 1 year, with documentation of stable size and vascularity, is recommended [128].

Infantile Hemangioma Infantile hepatic hemangioma (IHH) is the most common benign tumor of infancy, occurring in 5% of infants, with a a

Fig. 11.54  Infantile liver hemangioma in a 10-month-old female. (a) Reference transverse grayscale ultrasound image of the liver shows a well-circumscribed, echogenic focus (arrow) that (b) demonstrates prompt,

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higher incidence in girls, preterm infants, and in Caucasians (Tables 11.4 and 11.5) [127, 129]. IHH is frequently associated with cutaneous infantile hemangiomas. Immunostaining for GLUT-1 is an important differentiator between IHHs, which are GLUT-1 positive, and CHs, which are GLUT-1 negative. Unlike CH, IHH is generally not present at birth but usually becomes apparent within 4–6 weeks. It proliferates in the first year of life, followed by a slow involution that can last up to 10 years [130]. IHHs usually present as multi-focal or diffuse lesions that cause hepatomegaly. When diffuse, almost the entire liver parenchyma can be replaced, putting patients at risk for severe complications, including high-­output cardiac failure due to high volume arteriovenous shunting, hypothyroidism secondary to overproduction of type III iodothyronine deiodinase, bleeding, and abdominal compartment syndrome [123, 131–133]. As noted above for CH, the tumor nodules may appear as hyperechoic, hypoechoic, or mixed echogenicity well-­ circumscribed masses with prominent vascular channels. Doppler examination reveals low-resistance, high-velocity arterial flow. In contrast to CH, these tumors do not generally exhibit internal hemorrhage, necrosis, or calcification. On CEUS, CT, or MR imaging, there is typically arterial peripheral nodular enhancement with gradual central filling and diffuse enhancement with lack of washout on delayed imaging (Fig. 11.54). The majority of IHHs are discovered incidentally during routine imaging and do not require specific treatment. Ultrasound screening for liver IHH is recommended when five or more cutaneous IHHs are noted [134]. Propranolol is the mainstay of medical therapy.

b

rapid uptake (arrowheads) during the arterial phase of CEUS, greater than that of the adjacent hepatic parenchyma

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Mesenchymal Hamartoma Hepatic mesenchymal hamartoma (HMH) is the second most common benign liver mass in children, after hemangioma (Table 11.4) [135]. HMH is primarily seen in children under the age of 2 years and typically manifests as a large multicystic liver mass composed of a disordered arrangement of primitive mesenchyme, cysts lined with biliary-type epithelium, and hepatic parenchyma. Although the etiology is not well understood, HMH is associated with microRNA dysregulation and the DICER1 gene mutation [136, 137]. Children with HMH may present with an enlarging, painless abdominal mass that may lead to respiratory distress

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from mass effect or lower limb edema due to compression of the IVC [135]. If the mass is very large, complications can occur, including ascites, jaundice, and congestive heart failure due to intratumoral arteriovenous shunting. Paradoxically, while there are reports of spontaneous regression, HMH can rarely progress to an aggressive malignant undifferentiated embryonal sarcoma (UES) [135, 138]. AFP levels may be elevated. The classic imaging appearance of HMH is a complex cystic mass with thin internal septations (Fig. 11.55) [132, 139]. However, the appearance may range from predominantly cystic with thin or thick septa to predominantly solid-­

b

c

Fig. 11.55  Mesenchymal hamartoma of the liver in a 2-year-old female. (a) Transverse grayscale ultrasound image shows a large, cystic mass with thick septations. The cysts are of varying size and contain low-­level echoes.

(b) Transverse color Doppler ultrasound image demonstrates no evidence of septal hypervascularity. (c) Coronal T2-weighted, fat-suppressed MR image reveals that the mass replaces most of the right hepatic lobe

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appearing due to the presence of internal thick, proteinaceous material or hemorrhage, with a few small cysts. On ultrasound, anechoic spaces of varying size and number are seen and may contain low-level echoes, and thin or thick echogenic linear bands. The solid portions are echogenic. There is little color Doppler activity, which is limited to the septations and solid portions of the mass. On CT, the cystic portions of the mass are of fluid density and nonenhancing, while septations and solid portions demonstrate hypoenhancement compared to the background normal liver [132]. On MR imaging, the cystic portions of HMH demonstrate T2 hyperintensity, with variable T1 hypointensity depending on the protein content of the cyst fluid. Septations and solid portions demonstrate hypointensity on T1- and T2-weighted images, and mild enhancement following contrast material administration [138]. Surgical resection has traditionally been the treatment of choice. Less invasive techniques, such as ultrasound-guided cyst aspiration, either prenatally or postnatally [140], or ­laparoscopic fenestration, have been used [141]. Some investigators have opted for “watchful waiting” in asymptomatic patients, while others advocate resection of all HMHs due to their malignant potential [135, 139].

 ocal Nodular Hyperplasia F Focal nodular hyperplasia (FNH) is a benign epithelial liver tumor marked by the nodular proliferation of hyperplastic hepatocytes and biliary epithelium (Table  11.4) [3]. It is thought to occur as a result of a vascular abnormality originating within the lesion’s fibrous central stellate scar. An increased prevalence of FNH has been observed in patients with hereditary hemorrhagic telangiectasia and in children with a history of chemotherapy, which suggests that chemotherapy-induced vascular injury can lead to the development of FNH [142, 143]. FNH is a benign mass with nonaggressive features. It is often detected incidentally, most commonly in adult women, young children and adolescents. Patients may complain of right upper quadrant pain. Rare complications include hemorrhage and tumor rupture. As FNH is mostly composed of hepatocytes, its appearance may be subtle on imaging, with detection aided by the

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visualization of a central vascular scar or mass effect on adjacent structures. On ultrasound, FNH appears as a homogeneous mass that is isoechoic, hypoechoic, or hyperechoic to normal liver. Doppler evaluation reveals arterial flow within the hyperechoic central scar, with blood flowing to the periphery in a spoke-wheel configuration and displacement of vessels along the periphery of the lesion (Fig. 11.56) [3, 144]. CEUS is a favorable alternative to CT and MR imaging due to the lack of associated ionizing radiation, shorter scan times, and without the need for sedation [3]. CEUS findings include early arterial enhancement of a central feeding vessel leading to branching vessels in a spoke-wheel configuration [3]. Subsequently, there is centrifugal hyperenhancement of the lesion in the portal venous phase, and absence of washout on delayed phase imaging. A nonenhancing central scar may be seen (Fig. 11.57). Multi-phase CT and MR imaging may demonstrate characteristic features of FNH.  On unenhanced CT, FNHs are hypodense or isodense to background liver, although they may be hyperdense if the liver is fatty. On MR imaging, FNH is typically isointense or hypointense on T1-weighted images; slightly hyperintense or isointense on T2-weighted images; and has a hyperintense central scar on T2-weighted images. The postcontrast appearance of an FNH is similar on CT and MR imaging. In the arterial phase, there is homogeneous hyperenhancement, except for the central scar. In the portal venous and delayed phases, the lesion may become more isoenhancing, and the central scar may show some enhancement. If a hepatocyte-specific MR imaging contrast agent such as gadoxetate disodium (Eovist®, Bayer HealthCare Pharma­ ceuticals) is used, FNHs will demonstrate late hepatocytephase imaging (20 minutes after injection of contrast) due to the presence of functioning hepatocytes, a feature which helps to differentiate FNH from other liver lesions [145]. FNHs are typically asymptomatic lesions requiring no treatment. In symptomatic patients, transarterial embolization has been used to successfully control symptoms and reduce lesion size [146].

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Fig. 11.56  Focal nodular hyperplasia of the liver in a 16-year-old female. (a) Transverse grayscale ultrasound image shows a well-defined mass in the right hepatic lobe which is isoechoic to the liver parenchyma and contains a mildly echogenic, central stellate scar (arrow-

heads). (b) Transverse color Doppler ultrasound image demonstrates peripheral vessels within the mass. (c) Axial T2-weighted, fat-suppressed MR image depicts the hyperintense central scar (arrow)

Hepatic Adenoma Hepatic adenoma is a benign lesion formed by the proliferation of pleomorphic hepatocytes that contain lipid and glycogen and are arranged in sheets or cords rather than a normal acinar pattern (Table 11.4) [127]. They are typically solitary, occur more often in females than males, and are associated with the use of estrogen-containing oral contraceptives and anabolic androgenic steroids [132]. In chil-

dren, hepatic adenomas are associated with glycogen storage disease where multiple lesions are often present [127]. Patients are usually asymptomatic but may also present with hepatomegaly and abdominal pain due to spontaneous rupture leading to hemorrhage, including life-threatening hemoperitoneum [127].

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Fig. 11.57  Focal nodular hyperplasia of the liver in a 17-year-old male. (a) Longitudinal CEUS image obtained in the early arterial phase shows a spoke-wheel pattern of enhancement. (b) Longitudinal CEUS

image obtained in the late phase and (c) axial contrast-enhanced CT image show diffuse hyperenhancement of the lesion, with a central unenhanced focus (arrows) consistent with a scar

On grayscale ultrasound imaging, the appearance of hepatic adenoma is nonspecific (Fig.  11.58). It is well-circumscribed and may be hyperechoic due to the high lipid content of hepatocytes and heterogeneous due to the presence of hemorrhage and calcification [127]. In the setting of fatty infiltration of the liver as with glycogen storage disease,

an adenoma may be hypoechoic relative to the adjacent liver parenchyma (Fig. 11.59) [127]. There is no central scar. CEUS of hepatic adenoma typically shows rapid arterial hyperenhancement with centripetal filling of the lesion. In the portal venous and late phases, hepatic adenoma is typically isoechoic to the surrounding liver parenchyma. Occasionally,

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Fig. 11.58  Hepatic adenoma in a 15-year-old male. (a) Sagittal grayscale ultrasound image shows a heterogeneous mass (arrowheads) in hepatic segment VII. (b) Sagittal color Doppler ultrasound image demonstrates flow at the periphery of the lesion. (c) Axial gadoxetate disodium

(Eovist®) contrast-enhanced, T1-weighted, fat-suppressed MR image in the hepatobiliary phase demonstrates a hypointense mass (arrowheads) in the right hepatic lobe

in the late phase, gradual washout may occur, making the differentiation from malignancy more challenging and necessitating biopsy for diagnosis [3]. Postcontrast CT and MR imaging show enhancement patterns that are similar to those of CEUS [127]. On noncontrast CT, an adenoma may be isodense, hyperdense, or hypodense, depending on the presence of surrounding fatty infiltration and any intralesional fat, hemorrhage, or calcification. On MR imaging, intralesional blood products may create significant heterogeneity; out-of-­phase imaging typi-

cally demonstrates signal dropout due to the presence of microscopic fat [127]. Cessation of any hormonal therapy may lead to spontaneous regression [127]. Due to the risk of spontaneous rupture and risk of malignant transformation, surgical resection is considered the standard of care for larger adenomas [147]. Transarterial embolization and microwave ablation are emerging minimally invasive interventional radiology alternatives to surgical resection [148].

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Fig. 11.59  Hepatic adenoma in a 17-year-old female with glycogen storage disease type I. (a) Longitudinal grayscale ultrasound image of the liver demonstrates multiple hepatic masses. The largest lesion (arrow) is of mixed echogenicity while the smaller lesions (arrowheads) are hyperechoic relative to the surrounding hepatic parenchyma. (b) Longitudinal CEUS image of the largest lesion in (a) shows early arterial enhancement. (c) Longitudinal CEUS image obtained less than one second after the image in (b) shows rapid centripetal enhancement. (d)

Longitudinal CEUS image obtained in the portal venous phase reveals persistent hyperenhancement of the lesion compared to the adjacent normal hepatic parenchyma. (e) Longitudinal CEUS image obtained during the delayed phase reveals iso- to minimal hyperenhancement of the lesion compared to the adjacent normal hepatic parenchyma. No washout of contrast from the lesion relative to the normal parenchyma was demonstrated

Malignant Tumors

[149]. An increased prevalence in very low birth weight infants has been observed [151, 153]. Two-thirds of cases present in the first 2 years of life and 90% are seen in patients before the age of 5 years [149, 154]. There is a slight male predominance. Most children present with abdominal distension or nonspecific symptoms such as anorexia, weight loss, and vomiting. Jaundice is infrequently present. Common sites of metastatic disease include the lungs, bone, brain, and lymph nodes. Serum AFP levels are abnormally elevated in 90% of patients [149]. On imaging, hepatoblastoma appears as a well-circumscribed, lobulated, or septated mass, often large enough to cause significant hepatomegaly. Depending on its cellular make-up, the appearance may be homogeneous or heterogeneous, and coarse calcifications are often present [149]. Portal or hepatic vein invasion is commonly seen.

Hepatoblastoma Hepatoblastoma is the most common primary hepatic malignancy of childhood (Table  11.4) [149]. It is composed of embryonic cells with a spectrum of differentiation, from a poorly differentiated epithelial pattern, to well-differentiated cell types. Hepatoblastomas are divided into two broad categories: epithelial type and mixed epithelial and mesenchymal type. When present, mesenchymal cells, also with a range of differentiation, confer a heterogeneous appearance on imaging and pathologic analysis [149–152]. Hepatoblastoma has been associated with Beckwith– Wiedemann syndrome, Gardner syndrome (familial colorectal polyposis), trisomy 18, and type 1A glycogen storage disease

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The PRE-Treatment EXTent of tumor (PRETEXT) staging system for children with a primary hepatic malignancy is based on determining the number of contiguous tumorfree liver sections. It is used to guide prognosis and management and takes into consideration the extent of tumor within the liver, as well as additional annotation factors such as vascular involvement, extrahepatic extent, multifocality, and tumor rupture [155]. PRETEXT is widely accepted as a means of describing tumor extent in a standardized manner and has been proven to correlate with patient prognosis. PRETEXT staging is optimally determined by MR imaging [152, 155].

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On ultrasound, hepatoblastoma is usually hyperechoic with hypoechoic septa, and variable degrees of heterogeneity, marked by echogenic shadowing calcifications or anechoic foci representing hemorrhage or necrosis (Fig.  11.60) [152, 156, 157]. CEUS shows early peripheral enhancement during the arterial phase and brisk contrast agent washout during the late venous phase (Fig.  11.61) [3]. CT demonstrates a well-circumscribed, hypodense mass on unenhanced and contrast-enhanced images, with varying degrees of heterogeneity [152, 156, 158, 159]. Speckled or amorphous calcification is often seen [149]. On MR imaging, hepatoblastoma may appear homogeneously hypointense on T1-weighted images and hyperin-

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Fig. 11.60  Hepatoblastoma in a 10-month-old male. (a) Transverse grayscale ultrasound image shows a large heterogeneous mass (arrows) replacing most of the right hepatic lobe. Internal echogenic foci (arrowheads) demonstrate posterior acoustic shadowing consistent with calcification. (b) Coronal contrast-enhanced, T1-weighted, fat-suppressed

MR image depicts a solid mass in the right hepatic lobe with central ­nonenhancing foci consistent with necrosis. (c) Transverse grayscale ultrasound image obtained after chemotherapy reveals decreased size of the tumor and increased coarse calcifications (arrow) within the mass

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Fig. 11.61  Hepatoblastoma in a 7-year-old male. (a) Transverse grayscale ultrasound image of the liver demonstrates a heterogeneous mass (arrow) in the left hepatic lobe compressing the gallbladder (asterisk). (b) CEUS arterial phase image shows mildly increased contrast uptake by the mass compared to the surrounding hepatic parenchyma. Several anechoic foci (arrowheads) within the lesion represent tumor necrosis and/or hemor-

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rhage. (c) CEUS portal venous phase image reveals early contrast washout (arrowheads) from several sites within the mass. (d) Axial gadoxetate disodium (Eovist®) contrast-enhanced, T1-weighted, fat-suppressed MR image in the hepatobiliary phase demonstrates a heterogeneous, predominantly hypointense mass (arrow) in the left hepatic lobe. There is a subcapsular liver hematoma (asterisk) with a fluid-fluid level (arrowhead)

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tense on T2-weighted images; mixed tumors demonstrate heterogeneous signal intensity and enhancement [149, 152, 156, 158, 160]. Fibrotic septa are hypointense on both T1and T2-weighted images and enhance after contrast administration. Hemorrhagic areas may appear hyperintense on T1-weighted images. MR angiography is useful for the preoperative evaluation of the hepatic vasculature. Surgical resection is the definitive treatment for hepatoblastoma. Neoadjuvant chemotherapy is used to decrease tumor bulk and treat pulmonary metastases prior to resection or transplant [149, 152, 159, 162]. Interventional radiology procedure options, such as transarterial chemoembolization (TACE), radiofrequency ablation, and microwave ablation, are promising emerging techniques [152, 163, 164].

Hepatocellular Carcinoma Hepatocellular carcinoma (HCC) is a malignant tumor of cells of hepatocyte differentiation and the second most common primary hepatic malignancy in children after hepatoblastoma. Children who develop HCC are typically older, between 6 and 10  years of age, and may or may not have antecedent liver disease (Table 11.4) [165]. In parts of the world where HBV is endemic, perinatally acquired HBV is a major risk factor, with a high prevalence of HCC and a documented decline in incidence follow­ing mass HBV immunization [55]. Elsewhere in the world, non­infectious causes predominate, such as hereditary tyrosinemia, progressive familial intrahepatic cholestasis, glycogen storage disorder

Fig. 11.62  Hepatocellular carcinoma in a 15-year-old female. (a) Transverse grayscale ultrasound image shows multiple heterogeneously hypoechoic masses in the liver (arrowheads). (b) Axial image from CT

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type I, alpha-1-antitrypsin deficiency, Wilson disease, congenital portosystemic shunts, autoimmune hepatitis, and Alagille’s syndrome, and are indications for routine imaging and AFP surveillance [166]. Children usually present with an abdominal mass and pain. Advanced disease may present with weight loss, fever, or jaundice. Serum AFP levels are markedly elevated in most patients [149]. HCC may present as a solitary, multinodular, or diffuse infiltrative mass with a variable or mosaic appearance. On ultrasound, HCC typically appears as a large, lobulated, heterogeneously hypoechoic mass [167]. Echogenic areas may represent fat or acute hemorrhage, while hypoechoic or anechoic areas may represent old hemorrhage or necrosis (Fig.  11.62). Doppler evaluation can depict arterial flow within the mass, and assess for tumor invasion into the portal vein, hepatic veins, or IVC. CEUS, CT, and MR imaging demonstrate arterial phase hyperenhancement with washout in the portal venous and delayed phases [168]. Sites of metastasis include lymph nodes, lungs, brain, and bone. See Section “Hepatoblastoma” for a brief discussion of the PRETEXT staging system for children with a primary hepatic malignancy. The long-term survival rate remains poor. Management is targeted to complete surgical removal either by resection or liver transplantation [169]. Neoadjuvant chemotherapy and interventional radiology techniques are employed to downstage the tumor and improve survival [163, 164].

angiogram of the abdomen demonstrates prominent arterial enhancement of the lesions (arrowheads)

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Fig. 11.63  Fibrolamellar hepatocellular carcinoma in a 16-year-old male. (a) Transverse grayscale ultrasound image shows a large, exophytic, heterogeneously hypoechoic mass (arrowheads) arising from the

 ibrolamellar Hepatocellular Carcinoma F The fibrolamellar variant of HCC (FLHCC) is a distinct, rare variant of HCC with features that distinguish it from conventional HCC. In the pediatric population, it is more commonly seen in patients without underlying chronic liver disease (Table  11.4) [150]. Compared with pediatric HCC, FLHCC presents in older children (more than 12 years of age), is less often ­multifocal, and metastatic disease is often present, particularly to the lungs [167, 170]. Nodal metastases may be seen in the porta hepatis, retroperitoneum, pelvis, and mediastinum. Unlike conventional HCC, AFP levels are usually normal. Histologically, abundant collagenous fibrous sheets containing cords of tumor cells are arranged in a parallel configuration, hence the term “fibrolamellar” [171]. Pathologically, a central stellate scar is seen, another feature not typical for conventional HCC. Patients frequently present with abdominal pain, hepatomegaly, or abdominal mass. Malaise and weight loss may occur. On ultrasound, FLHCC is typically a solitary well-­ defined, lobulated mass that is heterogeneously isoechoic or hyperechoic (Figs. 11.63 and 11.64). Echogenic strands may be identified, representing the central scar with or without shadowing calcifications [167]. On multi-phase CT, FLHCC may present as a well-­ defined hypodense mass on unenhanced imaging, with heterogeneous arterial hyperenhancement. Portal venous and delayed phases show variable degrees of enhancement and washout. A central stellate scar is often present, though not pathognomonic for FLHCC, as both FNH and FLHCC may contain a central scar with a variable degree and timing of enhancement [149, 171]. However, when present, calcification within a thick, greater than 2 cm-wide central scar is a helpful distinguishing feature of FLHCC [172].

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liver. (b) Longitudinal color Doppler ultrasound image of the mass shows internal vascularity

Fig. 11.64  Fibrolamellar hepatocellular carcinoma in a 6-year-old male. Transverse grayscale ultrasound image of the right hepatic lobe demonstrates a well-defined, heterogeneous mass (arrow). An echogenic central scar aids in diagnosis when present, but may not be seen, as in this case

On MR imaging, FLHCC typically demonstrates T1weighted hypointensity and T2-weighted hyperintensity. The central scar usually appears hypointense on T1- and T2-weighted images, which helps to distinguish FLHCC from FNH, which usually has a T2-hyperintense scar [171]. Surgical resection is the mainstay of treatment. Tumor recurrence is common. The results of chemotherapy and radiation have been poor [167]. TACE and radiofrequency ablation have been used with positive outcomes in limited reports. Radioembolization with Yttrium-90 may be used to downstage initially unresectable masses [173].

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Rare Primary Tumors Undifferentiated embryonal sarcoma (UES) is a rare malignant mesenchymal tumor, most commonly found in patients between 6 and 10 years of age (Table 11.4) [167, 174]. UES consists of undifferentiated cells associated with a myxoid stroma. Patients present with an abdominal mass and pain. Tumor rupture has been reported at presentation, with associated hemoperitoneum and peritoneal seeding [175]. The classic imaging description is of a large, solitary mass with a predominantly solid, hyperechoic appearance on ultrasound and water density/intensity on CT/MR imaging, due to the high water content of the myxoid stroma

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[137]. However, predominantly anechoic masses have also been described [176]. Enhancing soft tissue components may be present at the periphery or in the form of septa (Fig. 11.65). Treatment consists of neoadjuvant chemotherapy with resection or liver transplantation. Epithelioid hemangioendothelioma (EHE) and angiosarcoma are malignant vascular tumors that may occur in the liver and can present in childhood. EHE is a low-to-­intermediate-­ grade vascular sarcoma, while angiosarcoma is a rare, aggressive malignant tumor [138]. For both tumors, multifocal involvement is typical, and the imaging appearance can be quite variable. The ultrasound appearance includes multiple nodules, a large mass, and a diffuse heterogeneous echotexture.

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Fig. 11.65  Undifferentiated embryonal sarcoma of the liver in a 6-year-old female. (a) Reference sagittal grayscale ultrasound image (left panel) and CEUS image (right panel) show a well-circumscribed, heterogeneously hypoechoic mass (arrows) with enhancing solid components. The mass

demonstrates internal, anechoic spaces (arrowheads) consistent with necrosis and/or hemorrhage. (b)  Coronal contrast-enhanced, T1-weighted, fatsuppressed MR image shows a large, multiloculated, hypointense and heterogeneously enhancing mass (arrows) centered in the right hepatic lobe

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Masses are typically hypodense on CT. Variable patterns of arterial enhancement have been described, including rimlike and heterogeneous [138]. Contrast-enhanced CT demonstrates progressive enhancement on portal and delayed phases [175]. When subcapsular in location, capsular retraction is a distinctive feature of EHE [138]. There is no standardized treatment for EHE. Recently, the mammalian target of rapamycin inhibitor, sirolimus, has been suggested as a possible therapeutic option in children [177]. With respect to hepatic angiosarcoma, the prognosis is very poor regardless of the treatment. The mean survival noted in the literature is 10 months to 2 years [178]. Rhabdoid tumors are uncommon and highly aggressive tumors of early childhood, most commonly occurring in the kidney and central nervous system [179, 180]. Primary hepatic rhabdoid tumors are extremely rare. On histology, cells resemble rhabdomyoblasts. Patients are often asymptomatic, and tumors are large upon presentation. The imaging appearance is nonspecific. Masses are predominantly solid and heterogeneous, and cystic components and calcifications may be present [180, 181]. Because of the rarity of this disease, there is no standard therapeutic algorithm. In a recent retrospective study of six pediatric patients treated at a single center, treatment for the three survivors consisted of intensive multiagent chemotherapy, early surgical resection of the tumor and radiotherapy in one child [182]. Embryonal rhabdomyosarcoma of the biliary tree is a highly malignant tumor which presents exclusively in children mainly under the age of 5  years [149]. It commonly arises in the extrahepatic biliary tree but may grow into the intrahepatic biliary tree and invade the liver [138, 149]. Patients may present with signs and symptoms that mimic viral hepatitis, including jaundice, abdominal distension, and fever. Ultrasound findings include biliary ductal dilation with an intraluminal mass. The portal vein is often displaced,

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without thrombosis [138]. Polypoid or grape-like projections are common. The tumor has a variable imaging appearance, ranging from solid to cystic components [149].

Metastases Metastatic disease is the most frequent malignancy of the liver [183]. The liver is a common site of metastatic disease, owing to its dual blood supply and cellular and molecular microenvironment that permits cancer cell growth [184]. The most common site of origin of liver metastases in children with solid tumors is neuroblastoma followed by Wilms’ tumor. Other solid malignant tumors that can metastasize to the liver include germ cell tumor, gastrointestinal stromal tumor, osteosarcoma, desmoplastic small round cell tumor, and neuroendocrine tumor [185]. Metastatic disease is often associated with a poor prognosis. A unique exception is neuroblastoma stage 4S (defined as localized primary tumor with dissemination limited to skin, liver, and/or bone marrow involvement less than 10% in infants younger than 12  months of age), which frequently regresses spontaneously without requiring therapy. Liver metastases are usually asymptomatic and detected during staging workup of patients with malignancy. Metastases are typically multifocal and involve both hepatic lobes. The imaging appearance of metastatic disease is quite variable and is dependent upon the nature of the primary tumor and the presence and degree of underlying hepatic steatosis, particularly for ultrasound and CT imaging [183]. Lesions may be solid or cystic, hypoechoic and well defined, hyperechoic, or targetoid due to central hemorrhage (Fig. 11.66) [183]. CEUS increases the accuracy of detection of metastatic disease compared to ultrasound performed without contrast administration, and has a similar sensitivity to CT [14, 186]. In particular, washout of contrast material in the portal

Fig. 11.66  Metastatic rhabdomyosarcoma in an 11-year-old female. (a) Transverse grayscale ultrasound image shows a hyperechoic intrahepatic mass (arrowheads) with a hypoechoic rim. (b) Transverse color Doppler ultrasound image reveals a small amount of blood flow within the lesion

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venous phase is highly associated with malignancy, similar to CT and MR imaging (Fig. 11.67) [9, 183]. Treatment of metastatic liver disease will vary according to the underlying primary tumor, but may involve surgery, radiation, and/or chemotherapy.

Lymphoma Primary hepatic lymphoma (PHL) is defined as lymphoma confined to the liver and perihepatic nodal sites. It is rare,

accounting for less than 1% of all non-Hodgkin lymphoma (NHL) [187]. PHL is associated with HBV, HCV, Epstein–Barr virus (EBV), and human immunodeficiency virus (HIV) [188]. In contrast, the vast majority of lymphomatous involvement of the liver is due to secondary involvement by non-Hodgkin lymphoma [187, 188]. Patients may present with right upper quadrant pain or jaundice, as well as systemic symptoms of fever and weight loss.

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Fig. 11.67  Metastatic renal cell carcinoma in a 21-year-old female. (a) Oblique longitudinal grayscale ultrasound image shows two echogenic lesions (arrowheads) in the right hepatic lobe. (b) Oblique longitudinal CEUS image (right panel) reveals prominent arterial enhancement of

the two masses (arrows). Reference grayscale image in the left panel (c) Oblique longitudinal CEUS image in portal venous phase (right panel) demonstrates rapid contrast washout (arrow) from the larger lesion. Reference grayscale image in the left panel

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PHL usually presents as a solitary, large liver mass that enhances heterogeneously (Fig.  11.68) [188]. Secondary hepatic lymphoma (SHL) most commonly presents as homogeneous, multifocal lesions or diffuse infiltration without a dominant mass, often with splenic lesions. A miliary pattern of numerous small hypoenhancing nodules throughout the liver is a less common presentation of SHL [188, 189]. On ultrasound, lymphomatous nodules are usually hypoechoic, without posterior acoustic enhancement (Fig. 11.69) [188]. Some nodules may demonstrate a target-like appearance, with a hyperechoic center and a peripheral hypoechoic rim [188, 189]. CEUS reveals portal and late phase washout, similar to other hepatic malignancies [190]. On CT and MR imaging, lesions demonstrate hypoenhancement compared with background liver parenchyma [188]. On MR imaging, the lymphomatous nodules tend to be hypointense or isointense on T1-weighted images and moderately hyperintense on T2-weighted images with restricted diffusion on diffusion-weighted imaging [188]. Some lesions may demonstrate a target appearance with central T2-weighted hyperintensity and a peripheral hypoin-

tense rim [188]. Fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT typically demonstrates avid hypermetabolic activity and is routinely used for staging and evaluation of treatment response [188]. Hepatic lymphoma is typically treated with a chemotherapy regimen based on the histologic subtype.

Fig. 11.68  Epstein–Barr virus (EBV)-associated lymphoproliferative disease in a 12-year-­old female. (a) Transverse grayscale ultrasound image of the left hepatic lobe shows a round, well-circumscribed, het-

erogeneous, solid mass with a thin hypoechoic rim. (b) Transverse color Doppler ultrasound image shows peripheral hyperemia with several enlarged vessels extending into the mass

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Fig. 11.69  Hepatic involvement in a 2-year-old female with immunodeficiency and diffuse large B-cell lymphoma. (a) Sagittal grayscale ultrasound image demonstrates a hypoechoic, geographic region

 osttransplant Lymphoproliferative Disorder P Posttransplant lymphoproliferative disorder (PTLD) represents a continuum of disease complications ranging from benign lymphoid hyperplasia to high-grade malignant lymphoma [191]. It occurs in the setting of solid organ or hematopoietic stem cell transplantation and immunosuppression. Most cases develop within the first year following transplantation when immunosuppression rates are highest [192, 193]. A second peak in incidence occurs 4–5  years following transplantation [192, 193]. 95% of PTLD cases are associated with EBV infection, which causes the proliferation of B-cells without the normal T-cell response due to immunosuppression [194].

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(arrowhead) along the periphery of the right hepatic lobe. (b) Sagittal color Doppler ultrasound image shows increased vascularity within the hypoechoic focus

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Children are at higher risk of developing PTLD than adults, likely related to lower rates of EBV seropositivity in children prior to transplant, with seroconversion occurring following exposure to EBV-seropositive donor organs [195]. PTLD often manifests within or near the site of the allograft, in nodal or extra-nodal locations. The liver is the most commonly involved abdominal organ [188]. Clinical features are based on location and pattern of organ involvement, and, when the liver is involved, may include fever, right upper quadrant pain, jaundice, and abnormal liver enzymes [191].

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Several patterns of solid organ involvement by PTLD may occur: The obstructive pattern of involvement of the liver appears as a mass in the region of the porta hepatis causing biliary ductal dilatation with or without vascular encasement and often without vessel occlusion [188]. The parenchymal (scattered) pattern appears as multiple scattered lesions throughout the liver parenchyma. PTLD in the liver can also manifest as one or more discrete masses (Fig.  11.70). Lastly, the infiltrative pattern of involvement appears as a mass extending into regional structures such as

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Fig. 11.70  Posttransplant lymphoproliferative disorder in a 10-year-old female with a liver homograft. Transverse (a) and sagittal (b) grayscale ultrasound images show a well-delineated, heterogeneously hypoechoic

mass with a central echogenic focus in the left hepatic lobe. (c) Sagittal color Doppler ultrasound image shows no internal vascularity

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the abdominal wall or adjacent organs, causing soft tissue edema and obscuration of fat planes [191]. On ultrasound, PTLD lesions are hypoechoic. On CT, PTLD lesions appear hypodense. MR imaging shows low or intermediate signal intensity abnormality on T1- and T2-weighted imaging, although lesions can occasionally appear hyperintense on T2-weighted imaging. Following contrast administration, lesions demonstrate hypoenhancement. They appear FDG-avid on PET [191]. Treatment approaches include reduction of immunosuppressive therapy, immunotherapy with the CD20 monoclonal antibody (rituximab), antiviral therapy, and/or chemotherapy. EBV-specific cytotoxic T lymphocytes are of limited availability but have been used with success [188, 196].

Leukemia Acute leukemia accounts for approximately 30% of all childhood malignancies and is the most common cancer in children [197]. Leukemic infiltrates may involve the liver, particularly along the portal tracts [198]. Myeloid sarcoma (synonymous with chloroma or granulocytic sarcoma) is a

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rare extramedullary mass of myeloid precursor cells that usually manifests during remission or disease relapse of acute myeloid leukemia (AML) [199]. Over half of children with leukemia have a palpable liver, palpable spleen, pallor, fever, or bruising on diagnosis [197]. The ultrasound appearance of leukemic infiltration of the liver includes a coarsened echotexture and hepatomegaly. The imaging features of hepatic myeloid sarcoma are nonspecific and are similar to those of hepatic lymphoma. The diagnosis of myeloid sarcoma can be suggested when there is a history of AML [188]. Similar to hepatic lymphoma, myeloid sarcoma can appear as hypoechoic lesions on ultrasound, with hypoenhancement or washout following intravenous contrast administration by CEUS, CT, or MR imaging (Fig. 11.71). However, compared with hepatic lymphoma, discrete masses of myeloid sarcoma are typically more heterogeneously enhancing and less wellcircumscribed [185]. Chemotherapy is used for the treatment of leukemia, with the possible addition of localized radiation therapy for myeloid sarcoma.

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Fig. 11.71  Hepatic leukemia in a 10-month-old male. (a) Sagittal grayscale ultrasound image shows a subcapsular, heterogeneously hypoechoic mass (arrowhead). (b) Sagittal color Doppler ultrasound image reveals minimal internal vascularity

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Liver Transplantation Introduction Advancements in surgical technique and immunosuppressive therapy have allowed liver transplantation to become a suitable treatment option for pediatric patients with end-­ stage liver disease. Ultrasound with Doppler assessment serves as the main imaging modality in the evaluation of liver transplants. A thorough understanding of the surgical approach and the specific anastomotic anatomy is vital in the interpretation of postoperative imaging studies. In this section, a review is provided of the various transplantation options for children, pre- and postoperative imaging considerations of the donor and recipient, postoperative monitoring of the graft, as well as the most important vascular and nonvascular postoperative complications (Tables 11.6, 11.7, and 11.8). Liver transplantation is an effective treatment option for children with end-stage liver disease [200, 201]. According to the Organ Procurement and Transplantation Network database, 17,560 pediatric liver transplants have been performed in the United States since 1988, and a total of 551 children received hepatic grafts in 2019 [202]. Biliary atresia is the most common etiology of pediatric end-stage liver disease, followed by metabolic disorders and acute hepatic necrosis. During organ procurement, patient weight and size are the major determinants of the type of graft that will be transplanted. In children, partial liver transplantation (living-­ related donor or split cadaveric liver graft) is the most

Table 11.6  Expected transient postoperative liver transplant ultrasound findings Location and type Grayscale findings Intrahepatic

Findings

Parenchymal edema at hepatectomy margin “Starry sky” parenchymal appearance Periportal edema Extrahepatic Ascites, small Fluid collections, small Right pleural effusion, small Regional lymph nodes Color and spectral Doppler findings All graft vasculature Slight narrowing at surgical anastomoses Hepatic artery Elevated hepatic artery RI up to 0.95 ( 12 years by week of menstrual cycle Week of menstrual cycle 1 2 3 4 5+

Uterine volume (cm3) Mean 45.3 45.7 49.8 52.2 51.5

Endometrial stripe thickness (mm) Mean 4.5 6.0 6.6 7.6 5.7

SD 16.2 19.0 24.0 20.9 23.3

SD 2.8 3.6 3.8 3.8 2.8

SD, Standard deviation Modified from Gilligan LA, Trout AT, Schuster JG, Schwartz BI, Breech LL, Zhang B, et al. Normative values for pelvic organs throughout childhood and adolescence. Pediatr Radiol. 2019;49(8):​1042–50. [5]

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Fig. 16.10  Ultrasound appearance of normal endometrial changes (cursors) during the menstrual cycle. Sagittal grayscale ultrasound images obtained on (a) day 5, early proliferative phase; (b) day 12, late proliferative phase; (c) day 17, early secretory phase; (d) day 26, late secretory phase

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Anatomic Variants

Müllerian Duct Anomalies

Arcuate Uterus

Anomalies occur when there is a failure of fusion of the paired müllerian ducts or incomplete resorption of the vertical midline septum. The incidence of müllerian duct anomalies is estimated at approximately 0.1–10% of the general population [9, 10]. The American Society of Reproductive Medicine has classified seven types of müllerian anomalies based on embryology (Fig. 16.11) [11]. Most of these anomalies are identified during evaluation for primary amenorrhea. The association of uterine and renal anomalies is well established. When a gynecologic anomaly is identified, the kidneys and urinary tract should be carefully assessed for additional abnormalities and vice versa.

An arcuate uterus is considered a variant of normal anatomy. The arcuate configuration results from incomplete resorption of the longitudinal septum between the two müllerian uterine horns, leaving a small soft tissue indentation at the top of the uterine fundus that extends less than 1 cm into the endometrial canal. An arcuate uterus has a normal, smooth, external fundal contour and a single endometrial cavity (Fig. 16.11). Individuals with an arcuate uterus have normal menses and normal reproductive potential.

Congenital Anomalies Given the complex and integrated sequence of events associated with development of the reproductive tract, there are many opportunities for abnormal development resulting in structural anomalies.

I Hypoplasia/agenesis

(a) Vaginal

(b) Cervical

Müllerian Agenesis Arrested development of the müllerian ducts results in complete agenesis or hypoplasia of the vagina, uterus, or both [12]. The stage of embryologic development at which arrest occurs determine which structures are affected. Of note, patients with müllerian agenesis will have normal ovaries

II Unicornuate

(a) Communicating

III Didelphus

(b) Non Communicating IV Bicornuate

(c) Fundal

(d) Tubal

(e) Combined (c) No cavity

VI Arcuate

V Septate

(a) Complete

(d) No horn

(a) Complete

(b) Partial

VII DES drug related

(b) Partial

Fig. 16.11  Classification of müllerian anomalies according to the American Society for Reproductive Medicine System. Buttram VC Jr, Gibbons WE. Müllerian anomalies: a proposed classification. Fertil Steril. 1979;32(2):40–6. [11]

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with normal external female genitalia development and undergo the normal changes of puberty. Uterine Agenesis Uterine agenesis is characterized by a complete absence of the uterus. The fallopian tubes will also be absent. Importantly, patients with isolated uterine agenesis will have a normal distal vagina, and the ovaries are typically normal in structure and function, though they may be in an atypical location. Patients will present with primary amenorrhea. On ultrasound, a thin strip of fatty tissue will be seen between the bladder and rectum (Fig. 16.12). Uterine transplantation is a recently introduced therapeutic option that is still in its infancy [12]. Mayer-Rokitansky-Küster-Hauser Syndrome (MRKH) Mayer-Rokitansky-Küster-Hauser syndrome (MRKH), also known as vaginal atresia, is defined as congenital absence of the upper two thirds of the vagina in association with variable müllerian duct anomalies [1]. The absence of the vagina is the characteristic that distinguishes MRKH from the other müllerian anomalies and has significant anatomic,

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physiologic, and psychologic implications for the patient. Most patients will also have associated cervical agenesis. MRKH has a reported incidence of 1 per 4000–5000 females and most often presents as primary amenorrhea [13]. The diagnosis may be suspected clinically after an abnormal physical examination. Affected individuals may have associated non-­gynecologic anomalies, most commonly unilateral renal agenesis, abnormalities of the middle ear, and abnormal development of the vertebral bodies (Klippel-Feil syndrome). Transabdominal ultrasound is the initial imaging study of choice for the evaluation of the uterus and adnexal structures, although MR imaging may be necessary for definitive diagnosis. Uterine anomalies vary from complete agenesis to a single midline uterine remnant with or without an endometrial cavity (Fig. 16.13). As with uterine agenesis, the ovaries are typically normal, and patients may not be diagnosed for some time due to normal estrogen-driven development of the breasts and external genitalia. Treatment includes psychological counseling and support, as well as creation of a functional vagina. This can be achieved through the use of dilators or surgery [14].

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Fig. 16.12  Uterine agenesis. (a) Longitudinal grayscale ultrasound image of the pelvis in a 7-year-old female. No uterus is identified. Sagittal (b) and axial (c) proton-density-weighted, fat-suppressed magnetic resonance (MR) images confirm the absence of the uterus with a

normal vagina (v) identified between the bladder (b) and rectum (r). Note the presence of normal ovaries (arrowheads) in the right and left superolateral aspects of the pelvis on the axial image

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Fig. 16.13 Mayer-Rokitansky-Küster-Hauser syndrome (MRKH) in a 16-year-old female. Longitudinal grayscale ultrasound images of the pelvis demonstrate (a) a small, tubular soft tissue structure (arrow) p­ osterior to the bladder without an endometrial stripe representing a uterine remnant. Normal right (b) and left ovaries (c) are identified. Longitudinal

grayscale ultrasound images reveal (d) a solitary right kidney and (e) absence of the left kidney. Sagittal (f) and (g) axial T2-weighted, fatsuppressed MR images confirm vaginal agenesis. Small, paired soft tissue structures adjacent to the normal ovaries (o) and connected by a fibrous band (arrowheads) are suggestive of rudimentary uterine buds

 isorders of Lateral Fusion D Incomplete lateral fusion of the paired müllerian ducts during embryologic development can result in a spectrum of abnormalities.

Bicornuate Uterus Partial fusion of the two müllerian ducts leads to the formation of a bicornuate uterus with two uterine horns joined together caudally by a central muscular septum. Two types of bicornuate uterus have been described, defined by involvement of the cervical canal (Fig. 16.11). In complete bicornuate uterus (bicornuate bicollis), the central myometrium extends to the level of the external cervical os resulting in two separate cervical canals (Fig. 16.15). In partial bicornuate uterus (bicornuate unicollis), the central myometrium extends only to the internal cervical os resulting in a single cervical canal that communicates with the two uterine horns. The distinction between a septate and bicornuate uterus is made by careful evaluation of the external uterine contour. In a bicornuate uterus, the two horns are more widely separated, typically by an intercornual distance greater than 4 cm, with a deep indentation (more than 1 cm) in the fundal contour (Fig. 16.16).

Septate Uterus Septate uterus is the most common müllerian anomaly seen in routine clinical practice. It results from failure of the final step of embryologic development and resorption of the median septum between the paired müllerian ducts. There are two types of septate uterus: complete septate uterus with a septum extending to the level of the internal cervical os; and partial septate uterus with a septum partially extending into the endometrial cavity without reaching the cervix (Fig. 16.11). The remnant midline septum consists of fibrous material that appears hypoechoic on ultrasound. The external uterine fundal contour may be flat or mildly (less than 1 cm) indented (Fig. 16.14).

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Fig. 16.14  Septate uterus in a 13-year-old female. (a) Transverse grayscale ultrasound image of the uterus demonstrates a hypoechoic muscular septum (arrow) dividing the endometrial cavity. The external fundal contour is also slightly indented (arrowheads). (b) Transverse grayscale

ultrasound image of the cervix demonstrates extension of the midline septum (arrowhead) through the endocervical canal. (c) Oblique axial T2-weighted, fat-suppressed MR image depicts the muscular septum ­(arrowheads) extending along the entire length of the uterus and cervix

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Fig. 16.15  Bicornuate bicollis uterus in a 15-year-old female. Transverse grayscale ultrasound images of the uterus (a) and cervix (b) show two distinct uterine horns and cervices separated by myometrium

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Fig. 16.16  Illustration of the anatomical differences between a bicornuate and a septate uterus. In a bicornuate uterus (a), the concavity of the external uterine contour (3) lies below (arrow) a straight line connecting the cornua (1 and 2); or (b) the concavity (3) lies less than 5 mm

2

3 1

2

(arrow) above the intercornual line. (c) In a septate uterus the apex of the external uterine contour (3) lies more than 5 mm (arrow) above the intercornual line

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If there is any uncertainty on ultrasound evaluation, MR imaging should be considered, as differentiation between these two entities is critical for patient counseling and future family planning. Septate uterus can be effectively treated surgically, leading to improved obstetric outcomes, while a bicornuate uterus is not amenable to surgical intervention. Uterus Didelphys Complete failure of müllerian duct fusion results in uterus didelphys, defined as two completely separate uterine horns, each with its own endometrial cavity and cervix (Fig. 16.11). Two cervices must be documented either by ultrasound or clinical examination to confirm the diagnosis of uterus didelphys. The two widely splayed uterine cavities and separate cervices can be identified by transabdominal ultrasound (Fig. 16.17). 3D ultrasound is useful in identifying the fundal cleft that serves to distinguish this condition from a complete septate uterus. A vaginal septum is seen in up to 75% of cases and may be complete or partial. If a vaginal septum results in obstruction of one or both uterine horns, it can be identified with ultrasound. MR imaging or physical examination may be needed for complete evaluation. Surgical treatment of uterus didelphys with a Strassman metroplasty is usually reserved for women with recurrent pregnancy loss [15]. Unicornuate Uterus Failure of one müllerian duct to elongate while the other develops normally results in a unicornuate uterus. Different types of unicornuate uterus have been described by the American Fertility Society (Fig.  16.11) [11]. An isolated unicornuate uterus is the most common, with a reported frequency of 35%. However, a rudimentary uterine horn may develop from the abnormal müllerian duct.

Fig. 16.17  Uterus didelphys in a 14-year-old female. Transverse grayscale ultrasound image shows two widely separated uterine cavities (arrows)

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With the exception of MRKH, urinary tract anomalies are seen more often with unicornuate uterus than with any other müllerian anomaly. Renal agenesis ipsilateral to the abnormally developed müllerian duct is the most common abnormality [9]. Ultrasound imaging of a unicornuate uterus may be challenging, especially via a transabdominal approach. A unicornuate uterus is typically smaller than a normal uterus and may be laterally displaced in the pelvis (Fig.  16.18). Identification of a rudimentary horn may be particularly difficult. If possible, these patients should be imaged in the latter half of the menstrual cycle in order to better visualize the thickened endometrium [16]. Use of 3D ultrasound can increase diagnostic accuracy [3]. However, many of these patients need further MR imaging for complete evaluation of the pelvic structures. A unicornuate uterus is characterized on MR imaging by its typically banana-shaped external contour, reduced uterine volume, and asymmetric configuration [15]. Surgical treatment is restricted to patients with a rudimentary uterine horn that can be resected when there is associated severe dysmenorrhea, chronic pain related to endometriosis, or dyspareunia. Surgery is also recommended for patients with a functional rudimentary horn that has an endometrial cavity in order to prevent a potentially life-­threatening pregnancy within the horn [15].

 isorders of Vertical Fusion D The upper and lower portions of the vagina are fused vertically during the process of recanalization of the müllerian duct. The hymen, a squamous mucosal tissue structure of the urogenital sinus, invaginates cranially from the perineum to meet the longitudinal vaginal canal of the müllerian duct. As the müllerian duct recanalizes, both the transverse vaginal plate and hymenal tissue resorb to create a tubular vaginal canal. Failure of the recanalization process results in vaginal obstruction. Imperforate Hymen During normal development of the vaginal canal, only a small remnant of circumferential redundant hymenal tissue remains at the vaginal introitus. An imperforate hymen occurs when the hymenal tissue fails to completely resorb. An imperforate hymen may present in the neonatal period as hydrocolpos or mucocolpos. However, patients are typically asymptomatic until the onset of menses when vaginal obstruction results in hematometrocolpos. On physical examination, a patient with an imperforate hymen usually presents with a vaginal bulge of thin hymenal tissue with a dark or bluish hue caused by the accumulation of menstrual blood in the proximal vagina [17]. On transabdominal ultrasound the obstructed vagina appears as a round or tubular mass in the pelvic midline

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Fig. 16.18  Left-sided unicornuate uterus and obstructed right hemi-­ uterus in a 13-year-old female. (a) Transverse grayscale ultrasound image of the pelvis reveals right and left-sided uteri with hypoechoic material (arrow) within the right endometrial cavity. (b) Longitudinal grayscale ultrasound image of the left pelvis reveals a well-developed uterus with a normal-appearing, echogenic endometrial lining (arrow-

head). (c) Longitudinal grayscale ultrasound image of the right pelvis reveals an abnormal, truncated shape of the rudimentary right uterine horn. (d) Coronal T2-weighted, fat-­suppressed MR image of the pelvis depicts the banana-shaped left uterus and the small, obstructed right hemi-uterus containing hypointense endometrial material (arrow). Arrowheads, Right and left ovaries

between the posterior wall of the bladder and anterior wall of the rectum (Fig.  16.19). Internal echoes are seen from accumulated cervical mucus or hemorrhagic material from menses. The uterine cavity may also be fluid-

filled and dilated. Clinical history, physical examination, and ultrasound demonstration of hematometrocolpos with otherwise normal pelvic organs are often sufficient for diagnosis.

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b U

V

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Fig. 16.19  Imperforate hymen with hematocolpos in an 11-year-old female. (a, b) Longitudinal grayscale ultrasound images of the pelvis demonstrate the markedly dilated, fluid-filled vagina (V) compressing the bladder (asterisk). U, Uterus

Surgical intervention is necessary only in symptomatic prepubertal patients. Once the diagnosis of imperforate hymen is confirmed, surgical intervention is usually deferred because the hymen may open spontaneously at puberty once estrogenization has occurred. Treatment includes incision (hymenotomy) or excision. Excision is preferred if the hymen is thickened or if the patient is an adolescent or older [17]. Transverse Vaginal Septum Failure of canalization of the transverse vaginal plate results in a transverse vaginal septum. A transverse septum is a membrane of connective tissue with vascular and muscular components that divides the vagina into two segments. The septum can vary in location, occurring in the upper (46%), middle (40%), or lower (14%) portions of the vagina [1]. The presenting symptoms of a transverse vaginal septum are similar to those of imperforate hymen with amenorrhea, cyclical pain, and a pelvic mass. However, on examination the hymen is normal, and there is a short, blind-ending vagina. Ultrasound findings in patients with imperforate hymen and transverse vaginal septum are similar. Differentiation of imperforate hymen and imperforate transverse vaginal septum relies on identification of the level of vaginal obstruction and evaluation of the thickness and composition of the band of tissue obstructing the vagina (Fig. 16.20). Transperineal ultrasound may be helpful in diagnosis (Fig. 16.21). Preoperatively it is essential to determine the location and thickness of the septum and to identify the presence or absence of a cervix. This is usually accomplished by combining the physical examination with findings at ultrasound and MR imaging. Most septa are 1 to several mm in thick-

ness, but occasionally a partial vaginal agenesis coexists, leading to a very thick obstruction, which changes the surgical approach. There are rare cases of cervical agenesis that resemble a high vaginal septum but require different surgical treatment [18]. Atresia of Cervix or Vagina Cervical atresia is a rare müllerian anomaly consisting of absence or aplasia of the cervix. It is characterized either by the absence of any cervical tissue or by the presence of markedly abnormal cervical tissue. It typically occurs in association with absence of the upper vagina and is usually diagnosed at menarche, when patients present with amenorrhea and cyclical lower abdominal pain. Delays in diagnosis and treatment can lead to endometriosis. Ultrasound is useful in documenting the absence of the cervix and can identify blood products in the uterine cavity (i.e., hematometra). Pelvic endometriomas may be seen as uni- or multilocular fluid collections containing low level echoes, internal septations, and mural nodules with no internal vascularity on color Doppler evaluation. Laparoscopy is the reference standard for the diagnosis of endometriosis although MR imaging is increasingly being used, especially to assess deep foci of disease. There is no consensus regarding optimal treatment of cervical atresia. Total hysterectomy is one option, while uterovaginal anastomosis offers an alternative for patients to maintain menstruation [19]. Isolated vaginal atresia occurs when the caudal portion of the vagina normally contributed by the urogenital sinus fails to form and is replaced with fibrous tissue. In contrast to the vaginal atresia associated with MRKH, this anomaly is extremely rare [20]. Patients present with primary amen-

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Fig. 16.20  Transverse vaginal septum in a 16-year-old female. (a) Longitudinal grayscale ultrasound image of the pelvis demonstrates a dilated distal vagina with internal echoes suggestive of hemorrhagic material. Hypoechoic tissue at the inferior aspect of the dilated upper

vagina (arrow) represents the vaginal septum. (b) Sagittal T2-weighted, fat-suppressed MR image confirms the presence of a transverse septum (arrow), with low-­intensity material filling the endometrial cavity of the uterus (U) and vagina (V)

Fig. 16.21 Transperineal imaging in the setting of hematocolpos may help differentiate between imperforate hymen and a transverse vaginal septum. (a) Transperineal longitudinal grayscale ultrasound image of an imperforate hymen in a 13-year-old female. Hematocolpos extends close to the vaginal introitus as measured by the calipers. (b) Transperineal longitudinal grayscale ultrasound image of a collapsed distal vagina in a 12-year-old female with a transverse vaginal septum. The proximal

vagina (V) is distended with blood products, while the distal vagina (calipers) appears collapsed. (c) Transabdominal longitudinal grayscale ultrasound image identifies the transverse vaginal septum (arrow) distal to the fluid-filled vagina (V). Images b and c from Paltiel HJ, Phelps A. US of the pediatric female pelvis. Radiology. 2014;270(3):644–57. B, Bladder; R, rectum; U, urethra

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orrhea and severe cyclical pelvic pain. Ultrasound imaging reveals hematometrocolpos. Although there is no consensus regarding optimal surgical treatment, pull-through vaginoplasty has been reported as an effective option [21]. OHVIRA Syndrome Obstructed hemivagina and ipsilateral renal anomaly (OHVIRA), also known as Herlyn-Werner-Wunderlich syndrome, is a müllerian anomaly characterized by uterus didelphys, unilateral obstructed hemivagina, and an ipsilateral renal anomaly. Patients with this syndrome usually present after

menarche with recurrent severe dysmenorrhea, pelvic pain, or occasionally with a vaginal mass due to an obstructed hemivagina that can be confused with a transverse vaginal septum. Transabdominal ultrasound is the initial imaging study of choice and can usually identify the uterus didelphys and hematocolpos [22]. When OHVIRA is suspected, further evaluation with MR imaging is usually performed for preoperative planning (Fig. 16.22). The goal of surgical treatment in OHVIRA is to relieve symptoms and guarantee successful reproductive outcomes. b

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Fig. 16.22 Obstructed hemivagina and ipsilateral renal anomaly (OHVIRA) syndrome in an 18-year-old female. (a) Transverse grayscale ultrasound image of the pelvis demonstrates uterus didelphys. (b) Longitudinal grayscale ultrasound image of the low pelvis reveals hema-

tocolpos of the left upper vagina (V). Coronal T2-weighted, fat-suppressed MR images confirm (c) the presence of fluid (arrowhead) in the obstructed proximal left hemivagina and (d) ipsilateral left renal agenesis

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Treatment of choice is resection of the vaginal septum in order to achieve continuity of the vagina [23].

Disorders of Sex Development Disorders of sex development (DSD) are defined as congenital conditions in which the development of the chromosomal, gonadal, or anatomic sex is atypical. DSD may be caused by chromosomal abnormality, gonadal dysgenesis, abnormalities of hormone production, or abnormal end-organ hormone response. DSD may be first suspected when a baby is born with an ambiguous appearance of the external genitalia; however, they can also occur in patients with normal external genitalia. Nomenclature and classification of these complex conditions has been proposed by the International Consensus Conference on Intersex and the European Society for Paediatric Endocrinology [24]. Previous terms (intersex, hermaphrodite, pseudohermaphrodite) should be avoided. Imaging plays an important role in the diagnosis of patients with suspected DSD. Ultrasound is used to establish the presence or absence of gonads and müllerian derivatives. Evaluation should include imaging of the pelvis to assess for the presence or absence of the uterus and ovaries, inguinal and perineal regions to document the presence or absence of testes, and renal and adrenal regions to document any abnormalities of these organs [25]. MR imaging can serve as an additional problem-solving tool to search for the gonads and clarify the internal anatomy.

 ex Chromosome Disorders of Sex S Development Sex chromosome DSD occurs when there is an abnormal number of sex chromosomes or localized genetic alterations of the sex chromosomes.

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45,X (Turner Syndrome) Turner syndrome is the most common sex chromosome DSD, caused by the absence of all or part of one of the X chromosomes. About 40–50% of females with Turner syndrome have the 45,X karyotype, 15–25% have mosaicism with 45,X/46,XX, 20% have an isochromosome, and ring X chromosomes are present in a few patients [25]. Affected individuals are born with a normal uterus, fallopian tubes, and vagina. However, the absence of a second X-chromosome leads to abnormal development of the ovaries. The ovaries consist of streaks or ridges of connective tissue in the mesosalpinx parallel to the fallopian tubes. There is delayed development of the external genitalia and a delay in the onset of puberty. Patients present with primary amenorrhea. Individuals with monosomy X are typically diagnosed in infancy or early childhood due to a classic physical appearance (short stature, low set ears, short webbed neck) and other congenital anomalies including Hashimoto thyroiditis, congenital heart disease, renal anomalies, diabetes, and skeletal abnormalities [1]. Streak ovaries are difficult to image with ultrasound due to their location and size and are typically less than 1 ml in volume (Fig. 16.23). If ultrasound fails to identify ovarian tissue, MR imaging can be considered for further evaluation. The uterus and vagina will have a prepubertal appearance. Treatment of patients with Turner syndrome depends on age and involves hormone replacement therapy as well as management of associated abnormalities. In childhood and adolescence, management is focused on growth and treatment with growth hormone. Hormone replacement therapy is used to induce puberty, to maintain feminization in adult life, and to reduce morbidity and mortality [25]. 46,XX Disorders of Sex Development Females with 46,XX DSD have a female genotype and two ovaries. However, their external genitalia may show a variable degree of virilization due to excess androgen hormone. b

Fig. 16.23  Streak ovaries in a 17-year-old female with Turner syndrome (45,X). Longitudinal grayscale ultrasound images of the right (a) and (b) left pelvis reveal tiny, dysplastic ovaries (cursors) that are significantly smaller than expected for age

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Congenital Adrenal Hyperplasia

detailed diagnosis as well as appropriate hormonal, surgical, and mental health treatment, as necessary [28].

Congenital adrenal hyperplasia (CAH) is a family of autosomal recessive disorders that is the most common cause of ambiguous genitalia seen in clinical practice. More than 90% of cases are caused by 21-hydroxylase deficiency, an enzyme that plays a vital role in steroid biosynthesis. There are mild and severe forms of the disorder, with the severe form ­usually detected in infancy or early childhood and the milder form presenting anywhere from infancy to adulthood. Equal numbers of females and males are affected. In the fetus, the absence of 21-hydroxylase leads to chronic stimulation of the adrenal glands by the pituitary gland leading to adrenal cortical hyperplasia, excess testosterone production, and abnormal development of the external genitalia and lower genitourinary tract [26]. Affected female infants will have masculinized external genitalia and lower genitourinary tract. The clitoris is enlarged, and there is partial or complete labial fusion. The urethra and lower vagina often unite to form a common channel, a urogenital sinus, and in this setting, there will be no separate vaginal opening on the perineum [1]. The internal female pelvic organs will develop normally. Ultrasound plays an important role in the diagnosis of CAH. The adrenal glands are diffusely enlarged, often with a “cerebriform” appearance (Fig. 16.24). The uterus and ovaries appear normal. Reflux of urine into the vagina and uterus in patients with a urogenital sinus can lead to hydrometrocolpos. Recently, contrast-enhanced ultrasound (CEUS) has been proposed as an alternative method to conventional genitography and voiding cystourethrography for delineation of the anatomical abnormalities associated with urogenital sinus [27]. Early and accurate identification of CAH is imperative as patients are at risk for developing primary adrenal insufficiency. If untreated, this disorder can lead to hypoglycemia, hyponatremia, hyperkalemia, cardiac arrhythmias, and shock. Management requires a multidisciplinary approach that includes input from specialists in genetics, endocrinology, surgery, psychology, or psychiatry in order to provide a

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Fig. 16.24  Congenital adrenal hyperplasia (CAH) in a 7-day-old female. Sagittal grayscale ultrasound images of the right (a) and left (b) adrenal glands demonstrate enlargement with a typical “cerebriform”

Cloacal Malformation Cloacal malformations are a group of non-hereditary anorectal malformations that result from interruption of the typical development of the urinary, genital, and gastrointestinal tracts. Failure of formation of the urorectal septum or urovaginal septum results in incomplete separation of these tracts. The result is a “cloaca,” a single channel that connects the urinary bladder, uterus/vagina, and rectum to the perineum. The etiology of cloacal malformation is not completely understood but is thought to result from a combination of genetic abnormality and hormonal influences. There is frequently an associated failure of fusion of the müllerian ducts which leads to duplication of the uterus and proximal vagina. The association of cloacal malformation and virilized external genitalia in 46,XX females without evidence of congenital adrenal hyperplasia is well recognized [29]. These patients are typically identified in infancy. Ultrasound in the early neonatal period plays an important role in diagnosis with evaluation of the pelvic organs, identification of the gonads and exclusion of adrenal hyperplasia. When a diagnosis is made, additional imaging with ­genitography and/or voiding cystourethrography as well as contrast material-enhanced examination of the distal limb of the colostomy is needed to detail anatomy. Recently, the use of CEUS in the elucidation of the connections between the urinary, genital, and gastrointestinal tracts has been proposed as an alternative to conventional fluoroscopic studies (see Chap. 17) [27]. Pelvic MR imaging is performed at a later stage when a pull-through procedure and closure of the colostomy are anticipated [30]. Treatment of the genitourinary abnormalities as well as of the associated congenital anomalies is complex and often requires many reconstructive operations.

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appearance. (c) Sagittal grayscale ultrasound image of the pelvis shows a normal neonatal uterus (arrow). B, Bladder

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Adnexal Masses The most common clinical symptoms of an adnexal mass are pelvic or abdominal pain. Occasionally a patient may present with a palpable abnormality on physical examination. Pelvic ultrasound is the initial imaging study of choice and is used to define the site of origin, document size, and determine the cystic, solid, or complex internal architecture of the mass.

Ovarian Masses Functional Cyst Functional ovarian cysts are the most commonly seen benign ovarian mass in all females, both pediatric and adult. Functional cysts occur when a dominant follicle fails to ovulate or when a corpus luteum does not regress after ovulation. While functional cysts are most frequent in postpubertal girls, they can also occur in neonates with follicular development in response to maternal hormone stimulation [31]. On ultrasound, simple functional cysts have anechoic internal contents, a thin wall, and posterior acoustic enhancement (Figs.  16.25 and 16.26). Differentiation between a functional cyst and a physiologic follicle is based on size. Functional cysts usually range between 3 and 5 cm in diameter, while physiologic follicles are less than 3 cm. The “daughter cyst” sign, a peripherally based simple cyst within a larger simple cyst, has also been described as a specific indicator of a stimulated ovarian follicle leading to a functional ovarian cyst, particularly in infants and young children (Fig. 16.27). Simple cysts typically resolve

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spontaneously in 2–3  months or over the course of 2–3 menstrual cycles. Consensus guidelines from the Society of Radiologists in Ultrasound (SRU) suggest follow-up ultrasound in patients with simple ovarian cysts measuring more than 5 cm in diameter. Repeat ultrasound is recommended at 2–6 months and again at 6–12 months to evaluate change in size and appearance over time [32]. If a simple cyst resolves or decreases in size at follow-up ultrasound and the patient remains asymptomatic, further imaging is not indicated. Surgery for functional simple cysts in the adolescent is indicated when there are significant symptoms or the cyst does not resolve on follow-up ultrasound. Debate about the risk of adnexal torsion in larger cysts applies to the adolescent patient as well as to adults, with some surgeons recommending intervention for larger cysts [31]. Once a decision is made to operate, surgical options include cyst aspiration, fenestration, or cystectomy. Ovarian cysts in the newborn may present with symptoms of abdominal pain or urinary tract obstruction if they are extremely large. Other possible presentations include acute torsion or spontaneous intracyst hemorrhage, which can be significant enough to lead to shock. All newborns with symptomatic ovarian cysts require surgical intervention to treat the underlying cyst [33]. Functional cysts may develop internal hemorrhage when theca interna vessels rupture into the cyst cavity. Most patients with hemorrhagic ovarian cysts present with acute onset of intermittent lower abdominal or pelvic pain, thought to result from sudden distension of the ovarian cyst by blood. On ultrasound, hemorrhagic ovarian cysts display a spectrum of findings reflecting the age of the blood products.

Fig. 16.25  Simple ovarian cyst in a 16-year-old female. Sagittal (a) and transverse (b) grayscale ultrasound images demonstrate a simple anechoic cyst (calipers) of the right ovary. (c) Longitudinal color Doppler ultrasound image reveals that the cyst is avascvular

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Fig. 16.26  Corpus luteum cyst in a 15-year-old female. Longitudinal (a) and transverse (b) grayscale ultrasound images of the right ovary on day 21 of the menstrual cycle show a cyst (calipers) with internal echoes

and thin internal septations. Note appropriate thickening of the endometrium (arrowhead) in the adjacent uterus (u)

Fig. 16.27  “Daughter cyst” sign in a 22-month-old female. Sagittal grayscale ultrasound image of the pelvis demonstrates an anechoic cyst arising from the left ovary that contains a peripheral internal cyst (arrowhead)

Fig. 16.28  Hemorrhagic ovarian cyst in a 16-year-old female. Transverse grayscale ultrasound image demonstrates a cyst in the left ovary (LT OV) with internal lacy septations. UT, Uterus

Acute blood products are usually hyperechoic, becoming more heterogeneous and eventually anechoic as the blood clots and then resorbs. Internal “lacy” or “cobweb” avascular septations are a classic imaging finding (Fig. 16.28). Rupture of a hemorrhagic ovarian cyst should be suspected if echogenic fluid is seen in the pelvis or peritoneal cavity.

Similar to simple cysts, hemorrhagic ovarian cysts should decrease in size and involute completely with time. Observation with repeat ultrasound examination at 6-week intervals is recommended [32]. Cysts that persist for several menstrual cycles may need to be investigated further with MR imaging to exclude cystic neoplasm.

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Endometrioma Endometriomas, also known as “chocolate cysts,” are a localized form of endometriosis that occurs within the ovary. While the mean age of diagnosis is in the third decade, endometriosis is not uncommon among adolescents. Typical symptoms include pelvic pain and dysmenorrhea. On ultrasound, endometriomas are characteristically unilocular cysts with diffuse internal “ground glass” echoes. However, atypical features are seen in up to 50% of cases. These features include multilocular cyst, hyperechoic mural foci, and a mixed cystic-solid appearance [34]. Endometriomas may be unilateral or bilateral. If bilateral, the echogenicity of the internal contents may be slightly different. Endometriomas, hemorrhagic cysts, and cystic neoplasms (discussed elsewhere in this chapter) can overlap in ultra-

sound appearance. Serial ultrasound imaging may be considered; however, MR imaging has been shown to have greater specificity for the diagnosis of endometriomas than other noninvasive imaging techniques and is recommended for further evaluation if the diagnosis is in question. Although endometriomas are usually benign, there is a reported malignant transformation rate of approximately 1% in adulthood. If the lesions are not surgically excised, yearly ultrasound follow-up is suggested to evaluate for changes in imaging characteristics or size.

Germ Cell Tumors Germ cell tumors (GCTs) are by far the most commonly seen ovarian neoplasm in the pediatric population. Table  16.3 summarizes the most important clinical, pathologic, and imaging features of ovarian tumors in children.

Table 16.3  Clinical, pathologic, and imaging features of ovarian tumors in children Tumor type Germ Cell Tumors Mature cystic teratoma

Age range Clinical features

Imaging features

10 – 20 years

Unilocular cystic mass with echogenic mural nodule and “tip of the iceberg” sign

Immature teratoma

10 – 20 years

Dysgerminoma

15 – 19 years

Yolk sac tumor

10 – 30 years

Non-gestational choriocarcinoma Epithelial tumors Cystadenoma

Mean age 14 years

Borderline (low malignant potential) Cystadenocarcinoma Sex Chord Stromal Tumors Fibroma – Thecoma

Most common ovarian neoplasm in pediatrics 10% bilateral Torsion may occur in 1/3 Often large May metastasize to liver, peritoneum and lung Most common malignant ovarian neoplasm in pediatrics Elevated serum LDH Elevated serum AFP

Very rare Elevated serum β-hCG

< 20 years Rare before puberty May be large, causing abdominal distension < 20 years Rare before puberty

< 20 years Rare in children

> 30 years Thecoma – estrogen production leads to precious puberty

Juvenile granulosa cell tumor < 30 years Most common sex chord stromal tumor in pediatrics Precocious puberty (75%) Sertoli-Leydig cell tumor Other Gonadoblastoma

< 30 years Virilization DICER-1 mutation < 20 years XY gonadal dysgenesis

Predominantly solid mass with internal fat and calcific foci Vascular solid components suspicious for malignancy Large, solid mass with internal fibrovascular septa

Mixed cystic and solid mass Rapidly growing Local and distant metastases common at diagnosis Highly vascular solid tumor with internal cystic, hemorrhagic, and necrotic regions Unilocular or multilocular cystic masses Serous – simple fluid Mucinous – low-level internal echoes Unilocular or multilocular cystic masses Thick, irregular septations Papillary projections Mixed cystic and papillary/solid masses Up to 20% bilateral Homogeneous or heterogeneous solid mass Fibroma – Meigs syndrome with associated ascites and pleural effusion Mixed cystic and solid mass Internal vascularity Uterine enlargement and thickening of endometrial stripe from tumor estrogen production Predominantly solid mass with peripheral or intratumoral cysts Large, lobulated, predominantly solid mass Internal fibrovascular septa

Abbreviations: LDH, Lactate dehydrogenase; AFP, alpha fetoprotein; β-hCG, beta human chorionic gonadotropin

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Ovarian GCTs develop from ova-producing cells and are composed of tissue derived from more than one of the three primitive embryonic layers: ectoderm, mesoderm, and endoderm. Because they arise from primitive cells, they have variable degrees of cellular differentiation, cellular maturity, and variable neoplastic potential. Up to 30% of ovarian GCTs in children and adolescents are malignant. As defined by the World Health Organization, the histologic subtypes of ovarian GCTs include teratoma, dysgerminoma, yolk sac tumor, embryonal carcinoma, non-­ gestational choriocarcinoma, and mixed GCT [35]. Germ cell tumor should be suspected when ultrasound demonstrates a solid or mixed cystic and solid mass associated with the ovary. In general, ultrasound imaging cannot reliably distinguish between the various GCT types although it can usually identify which masses are benign or malignant based on the proportion of soft tissue to cystic components. Benign tumors are usually cystic, whereas malignant tumors usually consist of greater than 50% soft tissue components [36]. Cystic areas reflect hemorrhage or necrosis and their walls may be thick and irregular. Due to the heterogeneous nature of ovarian germ cell tumors, treatment is determined by the histology of a particular tumor and may include one of the following approaches: surgical resection followed by careful monitoring for disease recurrence; initial surgical resection followed by platinum-­ based chemotherapy; or diagnostic tumor biopsy and preoperative platinum-based chemotherapy followed by definitive tumor resection. Teratoma Ovarian teratomas can be divided into two main subtypes, mature and immature, according to the degree of cellular differentiation of their components.

a

b

Fig. 16.29  Mature cystic teratoma in a 16-year-old female. (a) Lon­ gitudinal and (b) transverse grayscale ultrasound images of the pelvis demonstrate a cystic adnexal mass inseparable from the left ovary that contains a densely echogenic peripheral nodule (arrow) with posterior

Mature cystic teratoma (MCT), often called ovarian dermoid cyst, is the most common and accounts for up to 50% of all pediatric ovarian neoplasms [35]. MCTs are composed of mature or well-differentiated tissues derived from more than one germ cell layer. The characteristic imaging appearance of MCT on ultrasound is a cystic adnexal mass inseparable from the ovary with a densely echogenic peripheral nodule (Rokitansky nodule or dermoid plug) that demonstrates posterior acoustic shadowing (Fig. 16.29). The solid echogenic components may represent fat, sebaceous material, hair, and/or calcification from teeth or bone (Fig. 16.30). Shadowing may obscure deeper parts of the mass, a finding called the “tip of the iceberg” sign. Other ultrasound features of MCT include fat-fluid levels, floating echogenic debris, or multiple thin echogenic bands attributable to hair within the lesion (Fig. 16.31). No internal vascularity should be present on Doppler evaluation. Careful attention should be paid to the contralateral ovary as MCTs are bilateral in up to 26% of cases [35]. Immature teratomas are composed of primitive embryonal tissues admixed with mature tissues derived from the three germ cell layers. These tumors tend to be larger and more aggressive than MCT [35–37]. In contrast to MCT, immature teratomas are predominantly solid on ultrasound and often appear heterogeneous due to internal foci of fat. They may contain numerous small cystic areas and punctate calcifications may be present. Optimal treatment of GCT in the pediatric population is surgical excision due to a small risk of malignant transformation and the risk of associated ovarian torsion. Gonadoblastoma Gonadoblastoma is a rare ovarian tumor which typically occurs in the gonads of patients with XY gonadal dysgen-

c

acoustic shadowing. (c) Axial T2-weighted, fat-suppressed MR image shows the mass (arrowhead) with loss of signal in the peripheral nodule in keeping with fat

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b

a

C C

Fig. 16.30  Mature cystic teratoma in a 12-year-old female. (a) Lon­ gitudinal grayscale ultrasound image of the pelvis reveals a predominantly cystic pelvic mass (C) with complex peripheral nodule (arrow).

B

Fig. 16.31  Mature cystic teratoma in a 17-year-old female. Longitudinal grayscale ultrasound image of the left adnexa reveals a predominantly cystic mass containing an echogenic, fat-containing mural nodule (arrow) and a clump of hair (arrowheads) manifested as thin, radiating bands of tissue. B, Bladder. (Image courtesy of Dr. Casey Sams, Warren Alpert Medical School, Brown University, RI, USA)

esis (mixed gonadal dysgenesis or mosaic Turner syndrome) [38]. Occurrence in phenotypically and chromosomally normal females is extremely rare. Gonadoblastomas contain a mixture of germ cells and sex cord-stromal derivatives. On ultrasound, these lesions

(b) Coronal contrast-enhanced computed tomography (CT) image shows a mixed cystic and solid mass (C) containing focal calcification/ ossification (arrowhead)

are typically large, lobulated, and predominantly solid with internal fibrovascular septa. Associated simple and complex free fluid in the pelvis has also been reported [35, 38, 39]. Although gonadoblastoma is benign, it frequently coexists with a malignant germ cell tumor, most often dysgerminoma. For patients with dysgenetic gonads, bilateral oophorectomy and hysterectomy are usually recommended. In patients with a 46,XX karyotype, the necessity of bilateral gonadectomy is less clear. If the contralateral gonad is left in place in an attempt to preserve fertility, surveillance ultrasound should be performed. Dysgerminoma Dysgerminoma originates from undifferentiated germ cells in the ovary and is the histologic counterpart to testicular seminoma in boys. As with gonadoblastoma, these tumors may arise in dysgenetic gonads. However, they are just as frequently seen in genetically normal gonads. While most cases of dysgerminoma occur in the second and third decades of life, approximately 10% develop in adolescence [35]. Serum lactate dehydrogenase may be elevated in some patients with dysgerminoma. On ultrasound, a dysgerminoma appears as a predominantly solid, multilobulated mass that may contain foci of hemorrhage and necrosis and punctate calcification. Doppler evaluation can demonstrate internal fibrovascular septations [36, 37]. Dysgerminoma occurs bilaterally in up to 15% of cases and occasionally spreads to the regional lymph nodes (Fig. 16.32) [35]. For that reason, the contralateral ovary and adjacent pelvic and retroperitoneal nodal

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b

Fig. 16.32  Bilateral dysgerminomas in a 12-year-old 46,XY phenotypic female. (a) Sagittal grayscale ultrasound image of the mid-pelvis shows a juvenile uterus (arrow). Sagittal grayscale ultrasound images of the left (b) and right (c) pelvis reveal a dysplastic appearance of both

a

c

ovaries (arrowheads) that contain central echogenic foci and no recognizable follicles. Both ovaries were subsequently removed and each contained tissue consistent with dysgerminoma

b

Fig. 16.33  Yolk sac tumor in an 18-year-old female. (a) Sagittal color Doppler ultrasound image of the pelvis depicts a predominantly solid mass containing small cystic spaces and a minimal amount of blood

flow. There is a small amount of free pelvic fluid (asterisk). (b) Sagittal contrast-enhanced CT image reveals low attenuation of the mass (arrow) that may reflect necrosis. Asterisk, Free pelvic fluid

chains should be closely evaluated at diagnosis and on follow-up imaging.

Close evaluation for local and distant metastases should be performed. Most patients are treated with surgical resection and chemotherapy.

Yolk Sac Tumor Yolk sac tumor, also called endodermal sinus tumor, is a rare, aggressive, malignant GCT that often grows rapidly. Local and distant nodal metastases as well as peritoneal metastases are commonly seen at the time of diagnosis. This tumor produces alpha fetoprotein (AFP), which can be used to support the diagnosis and as a tumor marker for follow-up [36]. On ultrasound, yolk sac tumor is typically large at the time of diagnosis and predominantly solid but may contain internal cystic spaces due to necrosis and internal hemorrhage (Fig. 16.33). Ascites may be present.

Choriocarcinoma Choriocarcinoma most often occurs as a malignant transformation of a molar pregnancy (gestational choriocarcinoma). Very rarely, non-gestational primary ovarian choriocarcinoma can arise as a germ cell tumor. A non-gestational ovarian choriocarcinoma may be mixed with other germ cell tumors or arises as a primary pure choriocarcinoma of the ovary. Serum beta human chorionic gonadotropin (β-hCG) levels can be used to assist in diagnosis and follow-­up after treatment.

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On imaging, choriocarcinoma appears as a highly vascular solid tumor with internal cystic, hemorrhagic, and necrotic regions [36]. Of note, the presence of an adnexal mass in association with elevated β-hCG levels in patients of reproductive age may cause significant clinical confusion, and careful evaluation should be performed to exclude an ectopic pregnancy, a far more common condition than ovarian choriocarcinoma [40]. Mixed Germ Cell Tumor Ovarian mixed germ cell tumor is composed of more than one germ cell element. The most commonly occurring are dysgerminoma, teratoma, and yolk sac tumor, although other elements such as choriocarcinoma and embryonal carcinoma may be present [39]. A large number of histologically malignant elements are associated with more aggressive clinical behavior. The ultrasound appearance is variable and reflects the number and types of different tumor components present in the mass. Intralesional fat or calcification may be seen if an immature teratoma element is present (Fig. 16.34) [36]. Definitive diagnosis is made at pathology. a

b

Epithelial Tumors Epithelial ovarian tumors develop from the cells that cover the outer surface of the ovary and account for 15–20% of all pediatric ovarian tumors [35]. These tumors are potentiated by hormone production and their incidence increases with patient age, with most developing after the onset of menarche. Epithelial ovarian tumors can be classified as benign, borderline (of low malignant potential), or malignant depending on their histologic characteristics and clinical behavior. Cystadenoma Benign cystadenoma is the most common ovarian epithelial tumor seen in children. There are two subtypes: (1) serous, which contains clear watery fluid, and (2) mucinous, which contains thick viscous mucin [37]. On ultrasound, a ­cystadenoma appears as a thin-walled unilocular or multilocular cystic mass. These tumors can be very large at the time of diagnosis, measuring up to 20–30 cm and extending superiorly into the abdomen. Low-level internal echoes within cystic fluid should suggest mucinous content (Fig.  16.35). Conservative surgery with cystectomy is the appropriate treatment. c

Fig. 16.34  Mixed germ cell tumor in an 8-year-old female (a). Sagittal grayscale and (b) transverse color Doppler ultrasound images demonstrate a large, mixed cystic and solid mass arising from the right adnexa. The mass contains a small amount of internal blood flow. (c) Axial

contrast-enhanced CT image shows inhomogeneous tumor enhancement. Pathology revealed a mixed germ cell tumor (60% teratoma, 40% yolk sac tumor)

Fig. 16.35 Mucinous cystadenoma in a 15-year-old female. (a) Longitudinal grayscale ultrasound image of the pelvis reveals a large cystic mass with peripheral papillary projections (arrowheads) and containing internal echoes suggestive of mucin. (b) Sagittal T2-weighted, fat-sup-

pressed MR image depicts the mass anterior to the uterus (arrowhead) and extending superiorly into the abdomen. The mass contains multiple thin septations. (c) Axial contrast-enhanced, T1-weighted, fat-suppressed MR image shows no significant enhancement of the internal septations

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E. L. Riedesel and H. J. Paltiel

Borderline Epithelial Tumor and Cystadenocarcinoma Borderline epithelial tumor (also called a tumor of low malignant potential) and malignant cystadenocarcinoma are exceedingly rare in the pediatric population, accounting for less than 1% of all ovarian tumors in children and adolescents [41]. Both borderline and malignant epithelial ovarian tumors are usually of low grade and stage in pediatric patients and therefore have a better prognosis compared with adults. An elevated serum cancer antigen (CA)-125 level may suggest a borderline or malignant tumor type. Findings on ultrasound that should raise concern for a borderline tumor include a cyst greater than 10 cm in diameter with thick and irregular walls, vascular septations, papillary or solid components with flow on color Doppler imaging, and associated ascites [41]. Malignant cystadenocarcinoma is more likely to contain complex solid components which can demonstrate internal hemorrhage and necrosis. Up to 20% of more advanced tumors (borderline masses and carcinomas) can be bilateral [36]. Additional MR imaging is suggested in these patients to better evaluate for pelvic organ invasion, implants (peritoneal, omental, mesenteric), or evidence of nodal metastases. Borderline ovarian tumors in children and adolescents are treated conservatively, with fertility-preserving techniques and surveillance associated with good outcomes. The role of adjuvant therapy is not currently known [41].

Stromal Tumors Sex chord stromal tumors (SCST) are a rare class of tumor that develop from the stroma of the ovary and are composed of a variable combination of granulosa cells, theca cells, Leydig and Sertoli cells, and fibrous connective tissue cells. SCSTs account for 10–20% of all pediatric ovarian tumors, particularly in girls less than 15 years of age. While fibromas are the most commonly seen tumor type in adult, juvenile

a

b

Fig. 16.36  Juvenile granulosa cell tumor in a 15-year-old female. (a) Transverse grayscale ultrasound image shows a solid right adnexal mass containing numerous cystic spaces of varying size. (b) Transverse color Doppler ultrasound image with spectral analysis shows vessels within the

granulosa cell tumor (JGCT) and Sertoli-Leydig cell tumors are the most commonly seen in the pediatric age group [36]. As with other ovarian tumors, SCSTs present with the typical symptoms of an adnexal mass, including abdominal pain, distention, and rarely ovarian/adnexal torsion. SCSTs also frequently manifest signs of hormonal production by their cellular components [35]. Thecoma-Fibroma These tumors are rare in children and adolescents and account for less than 2% of all pediatric ovarian tumors. They usually occur in patients more than 30 years of age [35]. Thecomas are composed of lipid-containing theca cells and a variable number of fibroblasts, while fibromas are characterized by fibrous components. On ultrasound these tumors are typically solid masses which may be homogeneous or heterogeneous. Internal calcifications can be seen. Associated ascites and pleural effusion (Meigs syndrome) suggests ovarian fibroma, while estrogen effect with uterine enlargement and thickening of the endometrial stripe should suggest thecoma. Juvenile Granulosa Cell Tumor Juvenile granulosa cell tumor (JGCT) is the most common SCST seen in the pediatric population. Up to 75% of these tumors produce estrogen resulting in isosexual precocious puberty. These tumors have variable imaging characteristics. By ultrasound, the most typical appearance is a large, unilateral, multilocular cystic mass with an internal solid portion and occasionally with irregular septa (Fig. 16.36). However, JGCT can also appear as a predominantly solid mass with variable cystic areas. Internal vascularity – peripheral, central, or both – is typically seen on Doppler evaluation. Secreted estrogen from these tumors may cause uterine enlargement

c

mass containing arterial and venous flow. (c) Coronal T2-weighted, fatsuppressed MR image of the pelvis confirms the numerous cystic spaces within the mass

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and endometrial thickening. Metastases are uncommon, but when seen are typically to the peritoneal surfaces and liver. JGCT has a favorable prognosis in patients with stage I disease after surgical resection alone. Adjuvant chemotherapy may be indicated for patients with higher-stage tumors [42].

autopsy; however, they are rarely clinically detected during the course of disease. Ovarian infiltration at presentation of pediatric non-­ Hodgkin lymphoma (NHL) accounts for less than 2% of all pediatric ovarian tumors [45]. It occurs most often with Burkitt lymphoma and is considered a local manifestation of systemic disease rather than metastatic disease (Fig. 16.37). Metastatic spread to the ovaries occurs through four pathways: hematogenous spread, lymphatic spread, surface implantation from free intraperitoneal tumor cells, or direct spread from adjacent neoplasm. In one study, the most commonly seen hematogenous metastases to the ovary were from mucinous adenocarcinoma of the colon, rhabdomyosarcoma, Wilms’ tumor, neuroblastoma, and retinoblastoma. Surface implantation was also reported in colon cancer [45]. Findings suggestive of ovarian metastasis rather than a primary ovarian tumor are concurrent presence of metastatic foci in other organs and bilateral ovarian involvement. Treatment of ovarian metastases depends on the primary tumor type.

Sertoli-Leydig Cell Tumor Sertoli-Leydig cell tumor is a rare stromal lesion that accounts for less than 0.5% of all malignant ovarian neoplasms in children [35]. Patients may present with virilization and hirsutism due to excess androgen secretion by the tumor [43]. These tumors are usually detected early due to their clinical symptoms and are often confined to the ovary on initial diagnostic imaging. Small tumors may be difficult to identify on transabdominal ultrasound, and additional MR imaging should be considered if clinical suspicion is high. On ultrasound the tumor ranges from cystic to solid. It typically appears as a predominantly solid mass with peripheral or intratumoral cysts. DICER1 syndrome is associated with Sertoli-Leydig cell tumors. Patients with this diagnosis should undergo surveillance screening for other DICER1-related tumors [44]. This is often accomplished with whole body MR imaging.

Paraovarian Cyst A paraovarian cyst can be of mesothelial, mesonephric, or paramesonephric origin and is found along the broad ligament adjacent to the ovary. The classic ultrasound appearance is of a round or oval, anechoic, thin-walled cyst in the adnexa separate from the ovary (Fig. 16.38). Cyst fluid may be anechoic or echogenic. Unlike a functional ovarian cyst, a paraovarian cyst is not hormonally sensitive and therefore does not show cyclical changes and does not regress on follow-­up ultrasound examination. A paraovarian cyst

Secondary Tumors Although rare, secondary ovarian tumors should be considered in the differential diagnosis of ovarian and adnexal masses [35, 37, 45]. Similar to the testes, the ovaries may serve as a “sanctuary site” for surviving leukemic cells in children after chemotherapy. Leukemic infiltrates of the ovary are often found at

a

b

U

Fig. 16.37  Burkitt lymphoma of the ovary in a 7-year-old female. (a) Transverse grayscale ultrasound image of the pelvis reveals a solid, hypoechoic mass in the right adnexal region posterior to the uterus (U). A normal right ovary was not identified. (b) Coronal contrast-enhanced

CT image demonstrates bulky nodal disease in the pelvis (arrowhead) and enlargement of the right ovary (arrow) due to lymphomatous involvement

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can be identified during the ultrasound examination by using gentle compression to separate the ovary from the paraovarian cyst. Paraovarian cysts can sometimes be complicated by hemorrhage, torsion, or rupture. Large or symptomatic cysts are

B C

Fig. 16.38  Paraovarian cyst in a 16-year-old female. Longitudinal grayscale ultrasound image of the left adnexa demonstrates a simple cyst (C) separate from the left ovary (arrow). B, Bladder

a

often resected, and a laparoscopic approach can be used [46]. Smaller asymptomatic cysts are treated conservatively.

Peritoneal Inclusion Cyst A peritoneal inclusion cyst develops when peritoneal fluid absorption is significantly impaired in the setting of peritoneal inflammation and extensive peritoneal adhesions. Non-­ absorbed peritoneal fluid becomes trapped, creating a cyst-like fluid pocket [47]. Patients with a peritoneal inclusion cyst typically present with acute or chronic pelvic pain in the setting of prior surgery, trauma, or pelvic inflammatory disease. Peritoneal inclusion cysts may manifest as unilocular or multilocular fluid collections in the adnexa. Unlike ovarian or paraovarian cysts, the fluid conforms to the contours of the pelvis (Fig. 16.39). Adhesions may form irregular and thick septations within the fluid collection. The ipsilateral ovary may become “entrapped” within adhesive bands and fluid and is sometimes described as having the appearance of a spider sitting inside a spider web. Conservative treatment is typically advocated for peritoneal inclusion cysts. Oral contraceptive use may suppress ovulation to decrease ovarian fluid production, the predominant source of pelvic free fluid. Surgical intervention is reserved for select cases as it may exacerbate the underlying problem.

b

B

B U

Fig. 16.39  Peritoneal inclusion cyst in a 12-year-old female with a history of many prior abdominal operations. (a) Longitudinal grayscale ultrasound image of the pelvis demonstrates a fluid collection (asterisk)

superior to the bladder (B). U, Uterus. (b) Coronal T1-weighted MR image shows the fluid collection (asterisk) indenting the dome of the bladder (B)

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Adnexal Torsion Adnexal torsion is the fifth most common gynecologic emergency in the United States, with approximately 30% of cases occurring in females less than 20 years of age [48]. Adnexal torsion in young children and adolescent females most often occurs spontaneously as a result of increased mobility of the adnexal structures from ligamentous laxity and a relatively increased potential space within the pelvis that permits twisting [49]. When torsion is associated with an adnexal mass, the most common are benign functional ovarian cyst and benign ovarian teratoma. Torsion of the adnexal structures occurs around the vascular pedicle of the broad ligament. Twisting results in obstruction of the venous and lymphatic drainage of the affected ovary as well as arterial inflow, resulting in ovarian edema followed by infarction and necrosis. Transabdominal ultrasound is the imaging study of choice in pediatric patients with suspected adnexal torsion. The most reliable finding is unilateral ovarian enlargement. In this population, comparison of ovarian volume with established normal values at various ages and stages of development is extremely important (Table 16.1) [50]. In pre-menarchal girls, ovarian enlargement to 6–8  cm3 should raise concern for torsion. In post-menarchal girls, ovarian volume greater than 45–60 cm3 should increase suspicion for torsion [50, 51]. Size comparison with the contralateral ovary is also helpful. In the setting of adnexal torsion, affected ovaries are typically 3 to 4 times the volume of the normal, contralateral ovary. An ovarian volume 20 follicles per ovary. Other morphological features of the polycystic ovary that have been described but do not contribute to the formal ultrasound diagnostic criteria include peripheral location of follicles (“string of pearls” sign) and hyperechoic central ovarian stroma (Fig. 16.53). Most importantly, international experts now endorse that the performance of ultrasound criteria for diagnosis of PCOS is poor in adolescents due to overlap with normal findings of multi-follicular ovaries at this stage of life. In summary, while ultrasound findings may provide supportive evidence of PCOS, it is no longer required for definitive diagnosis of PCOS in the adolescent [89, 91]. When ultrasound is performed, strict use of the adjusted Rotterdam criteria is reserved for patients who are more than 8 years beyond menarche. a

c

b

Fig. 16.53 Polycystic ovary syndrome (PCOS) in a 19-year-old female. Longitudinal (left panel) and transverse (right panel) grayscale ultrasound images of the (a) right and (b) left ovaries demonstrate bilateral enlargement (volumes >10 mL) with increased echogenicity of

the central ovarian stroma and multiple peripheral follicles. (c) Sagittal T2-weighted, fat-suppressed MR image shows >20 follicles in the right ovary. A similar number were seen in the left ovary, thereby meeting Rotterdam criteria for diagnosis of PCOS

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Canal of Nuck Disorders The processus vaginalis is a normal embryologic outpouching of the parietal peritoneum that passes through the anterior abdominal wall at the internal inguinal ring and extends caudally toward the scrotum in males and the labia majora in females. In females, the patent processus vaginalis is called the canal of Nuck. A patent processus vaginalis can result in a communicating hydrocele or organ herniation, most often involving the bowel and pelvic organs [92]. Because obliteration of the processus vaginalis begins during gestation, disorders of the canal of Nuck are associated with prematurity [92]. The differential diagnosis for a palpable lump in the groin of a female patient includes a canal of Nuck

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hydrocele or hernia, a subcutaneous cyst such as a dermoid/ epidermoid cyst, and a lymph node or nodal abscess. Ultrasound evaluation of the canal of Nuck in females should be approached in a fashion similar to evaluation of the inguinal canal in males. Use of a high-frequency linear transducer is recommended. The inferior epigastric vessels are a critical landmark (see Fig. 15.43). These vessels originate from the external iliac artery and vein immediately above the inguinal ligament. There are usually three vessels that run together – two veins and an artery  – which are best identified in the transverse plane over the rectus abdominis, just below the umbilicus. These vessels can be traced inferiorly along the anterior abdominal wall to a point at which they pass from superficial to deep to the rectus abdominis muscles (Fig. 16.54). This point is the medial boundary of the deep inguinal ring and marks the superior aspect of the canal of Nuck. Once the deep inguinal ring is identified, ultrasound images should be obtained in a transverse plane along the course of the canal of Nuck from the deep inguinal ring to the labia majora. Longitudinal images are obtained by rotating the ultrasound probe along the long axis of the inguinal ligament, angled obliquely toward the labia majora.

Hydrocele of the Canal of Nuck Fig. 16.54  Ultrasound identification of the inguinal canal/canal of Nuck. Transverse color Doppler image of the right anterior abdominal wall demonstrates a normal appearance of the inferior epigastric vessels (arrow) deep to the rectus abdominis muscle. The deep inguinal ring (asterisk) is located just lateral to the inferior epigastric vessels

An entirely patent processus vaginalis can result in a communicating hydrocele. On ultrasound, a communicating canal of Nuck hydrocele appears as a tubular, anechoic inguinal structure extending from the deep inguinal ring (Fig. 16.55).

Fig. 16.55  Hydrocele of the canal of Nuck in a 17-year-old female. (a) Transverse grayscale ultrasound image of the right pubic region demonstrates a simple, anechoic fluid structure. (b) Longitudinal grayscale

ultrasound image shows extension of the fluid from the deep inguinal ring along the expected course of the canal of Nuck

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Visualization may be limited when ultrasound is performed in the supine position in a calm child [93]. Evaluation is improved when intra-abdominal pressure is increased with crying or a Valsalva maneuver. Alternatively, older children can be asked to stand for ultrasound evaluation. If only the inferior part of the processus vaginalis remains patent, an encysted hydrocele can form analogous to a hydrocele of the spermatic cord in males. Cysts of the canal of Nuck are typically found in the superior aspect of the labia majora [92]. On ultrasound, encysted hydrocele of the canal of Nuck should be suspected in any well-circumscribed, anechoic cystic structure in the subcutaneous tissues of the groin.

Hernia of the Canal of Nuck Hernias of the canal of Nuck are uncommon, occurring most often in premature infants. As the deep inguinal ring is at the superior end of the canal of Nuck and lateral to the inferior epigastric vessels, the canal of Nuck hernia is classified as an indirect hernia. Herniation of the bowel or ovary is seen most commonly (Fig. 16.56). Herniation of the uterus with the ovary has also been reported (Fig. 16.57). Although hernias of the canal of Nuck are rare, they can result in serious complications that require prompt diagnosis and clinical management. Incarceration, where the herniated structure is trapped in the canal of Nuck and cannot be readily reduced to its original location, has been reported in up to 43% of inguinal hernias involving an ovary. One possible explanation is that the herniated, edematous ovary is less compressible than herniated bowel [92]. Doppler evaluation should be performed to assess the blood flow in herniated pelvic organs. Strangulation, where blood flow to the herniated structure is compromised, may lead to necrosis. This finding requires urgent surgical intervention.

Fig. 16.56  Hernia of the canal of Nuck in a newborn female. Transverse grayscale ultrasound image shows the left ovary in the proximal inguinal canal. (Image courtesy of Dr. Casey Sams, Warren Alpert Medical School, Brown University, RI, USA)

Fig. 16.57  Hernia of the canal of Nuck in a 12-day-old female with mixed gonadal dysgenesis. Longitudinal grayscale ultrasound image shows a hemi-uterus (arrow) in the inguinal canal

References 1. Paltiel HJ, Phelps A. US of the pediatric female pelvis. Radiology. 2014;270(3):644–57. 2. American College of Radiology. ACR-AIUM-SPR-SRU Practice Parameter for the Performance of Ultrasound of the Female Pelvis. [Internet] 2019; Available at https://www.acr.org/-/media/ACR/Files/ Practice-Parameters/US-Pelvis.pdf?la=en. Accessed December 1, 2019. 3. Benacerraf B. Three-dimensional volume imaging in gynecology. Obstet Gynecol Clin N Am. 2019;46(4):755–81. 4. Son JK, Taylor GA. Transperineal ultrasonography. Pediatr Radiol. 2014;44(2):193–201. 5. Gilligan LA, Trout AT, Schuster JG, Schwartz BI, Breech LL, Zhang B, et al.  Normative values for pelvic organs throughout childhood and adolescence. Pediatr Radiol. 2019;49(8):1042–50. 6. Benjaminov O, Atri M. Sonography of the abnormal fallopian tube. AJR Am J Roentgenol. 2004;183:737–42. 7. Ssi-Yan-Kai G, Rivain AL, Trichot C, Morcelet MC, Prevot S, Deffieux X, De Laveaucoupet J.  What every radiologist should know about adnexal torsion. Emerg Radiol. 2018;25(1):51–9. 8. Langer JE, Oliver ER, Lev-Toaff AS, Coleman BG. Imaging of the female pelvis through the life cycle. Radiographics. 2012; 32(6):1575–97. 9. Troiano RN, McCarthy SM.  Mullerian duct anomalies: imaging and clinical issues. Radiology. 2004;233(1):19–34. 10. Marten K, Vosshenrich R, Funke M, Obernaeur S, Baum F, Grabble E. MRI in the evaluation of müllerian duct anomalies. Clin Imaging. 2003;27(5):346–50. 11. Buttram VC Jr, Gibbons WE.  Müllerian anomalies: a proposed classification. Fertil Steril. 1979;32(2):40–6. 12. Brännström M, Dahm Kähler P, Greite R, Mölne J, Díaz-García C, Tullius SG.  Uterus transplantation: a rapidly expanding field. Transplantation. 2018;102(4):569–77. 13. ACOG Committee Opinion No. 728: Mullerian agenesis: diagnosis, management, and treatment. Obstet Gynecol. 2018;31(1):e35–42. 14. Herlin M, Bay Bjørn AM, Jørgensen LK, Trolle B, Petersen MB.  Treatment of vaginal agenesis in Mayer-Rokitansky-­ Küster-Hauser syndrome in Denmark: a nationwide comparative study of anatomical outcome and complications. Fertil Steril. 2018;110(4):746–53. 15. Bhagavath B, Ellie G, Griffiths KM, Winter T, Alur-Gupta S, Richardson C, Linheim SR.  Uterine malformations: an update of diagnosis, management, and outcomes. Obstet Gynecol Surv. 2017;72(6):377–92.

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E. L. Riedesel and H. J. Paltiel 80. Jallouli M, Trigui L, Gargouri A, Mhiri R. Vaginal polyp in a newborn. Eur J Pediatr. 2008;167(5):599–600. 81. Reck-Burneo CA, Villanueva J, Veleck FT. Vaginal mullerian papilloma: an unusual cause of vaginal bleeding in a toddler. J Pediatr Adolesc Gynecol. 2009;22(5):e124–6. 82. Huo D, Anderson D, Palmer JR, Herbst AL.  Incidence rates and risks of diethylstilbestrol-related clear-cell adenocarcinoma of the vagina and cervix: update after 40-year follow-up. Gynecol Oncol. 2017;146(3):566–71. 83. Chauhan S, Nigam JS, Singh P, Misra V, Thakur B.  Endodermal sinus tumor of vagina in infants. Rare Tumors. 2013;5(2):83–4. 84. Yang X, Sun L, Ye J, Li X, Tao R.  Ultrasonography in detection of vaginal foreign bodies in girls: a retrospective study. J Pediatr Adolesc Gynecol. 2017;30(6):620–5. 85. Boyse TD, Fessel DP, Jacobson JA, Lin J, van Holsbeek MT, Hayes CW.  US of soft tissue foreign bodies and associated complications with surgical correlation. Radiogaphics. 2001;21(5):1251–6. 86. Wolf RM, Long D. Pubertal development. Pediatr Rev. 2016;37(7):​ 292–300. 87. Klein DA, Emerick JE, Sylvester JE, Vogt KS. Disorders of puberty: an approach to diagnosis and management. Am Fam Physician. 2017;96(9):590–9. 88. Bradley SH, Lawrence N, Steele C, Mohamed Z. Precocious puberty. BMJ. 2020;368:l6597. 89. Senaldi L, Gopi RP, Milla S, Shah B.  Is ultrasound useful in the diagnosis of adolescents with polycystic ovary syndrome? J Pediatr Endocrinol Metab. 2015;28(5-6):605–12. 90. Costello MF, Misson ML, Balen A, Boyle J, Devoto L, Garad RM, et  al. Evidence summaries and recommendations from the international evidence-based guideline for the assessment and management of polycystic ovary syndrome: assessment and treatment of infertility. Hum Reprod Open. 2019;2019(1):hoy021. 91. Rotterdam ESHRE/ASRM-Sponsored PCOS Consensus Workshop Group. Revised 2003 consensus on diagnostic criteria and long-­ term health risks related to polycystic ovary syndrome (PCOS). Hum Reprod. 2004;19(1):41–7. 92. Chan D, Kwon JK, Lagomarsino EM, Veltkamp JG, Yang MS, Pfeifer CM.  Canal of Nuck hernias. Acta Radiologica Open. 2019;8(12):1–5. 93. Rafailidis V, Varelas S, Apostolopoulou F, Farailidis D. Nonobliteration of the processus vaginalis: sonography of related abnormalities in children. J Ultrasound Med. 2016;35(4):805–18.

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Urinary Tract Ghadir H. Kassab, Ian Robinson, Roisin Hayes, Harriet J. Paltiel, D. Gregory Bates, Harris L. Cohen, Richard A. Barth, and Gabrielle Christina Maria Colleran

Abbreviations AAST American Association for the Surgery of Trauma ACKD Acquired cystic kidney disease AIDS Acquired immunodeficiency syndrome AKI Acute kidney injury AVF Arteriovenous fistula ATN Acute tubular necrosis ATRT Atypical teratoid rhabdoid tumor CEUS Contrast-enhanced ultrasound CeVUS Contrast-enhanced voiding urosonography CKD Chronic kidney disease COG Children’s Oncology Group CPDN Cystic partially differentiated nephroblastoma CT Computed tomography DMSA Dimercaptosuccinic acid eGFR estimated glomerular filtration rate ESRD End-stage renal disease FDG Fluorodeoxyglucose IVC Inferior vena cava MAG3 Mercaptoacetyltriglycine

MCDK Multicystic dysplastic kidney MIBG Metaiodobenzylguanidine MR Magnetic resonance MRU MR urography PET Positron emission tomography PNET Primitive neuroectodermal tumor PSV Peak systolic velocity PUNLMP Papillary urothelial neoplasm of low malignant potential PUV Posterior urethral valves RAS Renal artery stenosis RCC Renal cell carcinoma RI Resistive index RVT Renal vein thrombosis SIOP International Society of Paediatric Oncology STING Subureteric transurethral injection SWE Shear wave elastography TCC Transitional cell carcinoma Tc Technetium UPJO Ureteropelvic junction obstruction (abbreviations continue)

Electronic Supplementary Material The online version of this chapter (https://doi.org/10.1007/978-3-030-56802-3_17) contains supplementary material, which is available to authorized users. G. H. Kassab Department of Radiology, Children’s Health Ireland at Temple Street, Dublin, Ireland

D. G. Bates Department of Radiology, Nationwide Children’s Hospital, The Ohio State University College of Medicine, Columbus, OH, USA

I. Robinson ∙ G. C. M. Colleran (*) Department of Radiology, National Maternity Hospital and Children’s Health Ireland at Temple Street, University College Dublin School of Medicine, Dublin, Ireland e-mail: [email protected]

H. L. Cohen Department of Radiology, Le Bonheur Children’s Hospital, University of Tennessee Health Science Center, Memphis, TN, USA

R. Hayes Department of Radiology, Children’s Health Ireland at Crumlin, Dublin, Ireland

R. A. Barth Department of Radiology, Lucile Packard Children’s Hospital, Stanford University School of Medicine, Stanford, CA, USA

H. J. Paltiel Division of Ultrasound, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA © Springer Nature Switzerland AG 2021 H. J. Paltiel, E. Y. Lee (eds.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-56802-3_17

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(abbreviations continued) UTD UTI UVJ UVJO VCUG VHL VUR

Urinary tract dilation Urinary tract infection Ureterovesical junction Ureterovesical junction obstruction Voiding cystourethrography Von Hippel–Lindau Vesicoureteral reflux

Introduction Ultrasound is the imaging modality of choice for the assessment of the urinary tract in children, particularly in the workup of hydronephrosis, urinary tract infection, kidney masses, and bladder abnormalities. Other important applications include the evaluation of stone disease, kidney failure, renovascular disease, and kidney transplants. This chapter reviews the development and anatomy of the urinary tract followed by an overview of ultrasound imaging features of urinary tract disorders in children. Brief discussions of clinical presentation and treatment approach are also included.

Technique Patient Positioning Examination of the kidneys is usually performed with the patient supine or in a lateral decubitus position, using the liver or spleen as an acoustic window. A posterior approach with the patient prone can be used if bowel gas obscures visualization of the kidneys and is also useful for less cooperative patients. The supine and lateral decubitus positions are best for visualization of the upper renal poles, while prone positioning is optimal for imaging of the lower renal poles. The kidneys of uncooperative younger children can also be scanned from the back, while seated on a caregiver’s lap. Bladder images are acquired with the patient supine. Sedation is rarely required during the examination. Infants can be fed or given a pacifier. Children older than a year of age can usually be distracted by playing with toys, reading a book, or watching a movie.

Ultrasound Transducer Selection Studies should be performed using the highest frequency transducer that will penetrate the region being examined to optimize image resolution. A curved linear or sector trans-

ducer should be used for evaluating the kidneys. A curved linear transducer is used to obtain bladder images.

Imaging Approaches No special preparation is required for most patients. A moderately full urinary bladder is desirable when a study is ­performed for urinary tract stones or hematuria. Children undergoing renal Doppler evaluation should have nothing to eat or drink prior to the study for a time period that varies according to patient age. Image acquisition in infants should begin with the urinary bladder as they may void suddenly. Post-void images of the bladder are obtained in patients who are toilet-trained. Images of the kidneys are acquired in transverse and longitudinal planes [1, 2]. In order to assess renal parenchymal echogenicity, longitudinal images must include a portion of the liver and the spleen. The ureters are assessed at their origin from the renal pelvis and where they enter the bladder.

Grayscale Imaging Grayscale imaging is the cornerstone of the renal ultrasound examination and is used to assess renal size and parenchymal echogenicity, document urinary tract dilation, and diagnose stones and masses. Harmonic imaging is often helpful to minimize artifacts.

Doppler Ultrasound Doppler ultrasound is used in the evaluation of the renal vasculature when arterial or venous disease is suspected, as well as in the routine evaluation of renal transplants.

Contrast-Enhanced Ultrasound Contrast-enhanced ultrasound (CEUS) involves the intravenous or intracavitary administration of ultrasound microbubbles and can be used for real-time evaluation of the renal microvasculature. This can be particularly beneficial in suspected vascular disorders (infarction, cortical necrosis); differentiating between solid and cystic renal lesions and between tumors and pseudotumors; characterization and follow-up of complex cystic masses; and identification of renal abscesses. It can be a valuable alternative to computed tomography (CT) or magnetic resonance (MR) imaging where CT or MR imaging contrast is contraindicated [3]. Contrast-enhanced voiding urosonography

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is a nonionizing radiation alternative to conventional voiding cystourethrography.

Somites

Nephrotome region

Elastography Chronic kidney disease eventually results in intra-renal fibrosis, with fibrosis degree correlating with disease severity. Shear wave elastography (SWE) is an imaging technique that permits the noninvasive assessment of renal stiffness. SWE uses focused acoustic energy pulses to produce microscopic tissue displacement, which induces perpendicular shear waves that are tracked by ultrasound as they progress through tissue. Based on the physical principal that stiffer tissues produce higher shear waves velocities, higher SWE values correlate with higher degree of renal fibrosis. This may permit earlier detection of chronic renal disease, allowing for prompt institution of appropriate treatment [4–6]. However, there is currently very little published data on the use of elastography in pediatric chronic kidney disease.

Gut

Mesonephric region

Allantois

Metanephric region

Cloaca

Ureteric bud

Fig. 17.1  Diagram of the embryo depicting the nephrotome, mesonephric, and metanephric regions from which the pronephros, mesonephros, and metanephros will respectively arise. The pronephros and mesonephros will regress, while the metanephros develops into the permanent kidney

Normal Development and Anatomy

Aorta

Glomerulus

Posterior cardinal vein

Normal Development Development of the urinary tract starts in the fourth gestational week. A longitudinal ridge of mesodermal tissue, the urogenital ridge, arises from the posterior wall of the abdominal cavity along both sides of the abdominal aorta. The urogenital ridge develops into the nephrogenic cords, the origins of the urinary system; and the gonadal ridge, which ultimately forms the genital system. Three pairs of excretory organs develop sequentially in the human embryo, from cranial to caudal: the pronephros, the mesonephros, and the metanephros (Fig. 17.1). The glomeruli and mesonephric tubules arise from the mesonephros and drain into the mesonephric (wolffian) duct (Fig. 17.2). The mesonephric duct in turn opens into the cloaca, the common embryonic excretory cavity (Fig. 17.3). At the end of the first trimester, the mesonephros regresses. The ureteric bud, a diverticulum of the mesonephric duct, along with the metanephric blastema, which arise from the nephrogenic cord, gives rise to the metanephros in the fifth week of gestation (Fig. 17.4). The stalk of the ureteric bud becomes the ureter, and the branching of the ureteric bud forms the renal pelvis, calyces, and collecting tubules. The metanephric blastema leads to the formation of the glomerulus, proximal tubule, loop of Henle, and distal tubule. The cloaca is separated by the urorectal septum into the urogenital sinus anteriorly and the rectum posteriorly in the fourth to sixth weeks of gestation. The urinary bladder

Mesonephric tubule

Mesonephric duct

Gut

Glomerular capsule

Subcardinal vein

Fig. 17.2  Diagram of the functional unit of the mesonephros

develops from the superior portion of the urogenital sinus, and its development is complete by the fourth gestational month. The inferior portion of the urogenital sinus leads to the development of the membranous urethra in both males and females. In males, the caudal portion of the urogenital sinus also gives rise to the spongy portion of the urethra that meets the penile urethra. The penile urethra is derived from a cord of ectoderm that grows from the tip of the glans penis (Fig. 17.5).

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Nephrotomes tomes

Degenerating nephrotomes

Primary nephric duct

Gonad

Mesonephric tubules Mesonephric duct

Uninduced intermediate mesoderm

Metanephrogenic blastema Ureteric bud

Cloaca

Fig. 17.3  Diagram showing, from left to right, sequential development of the mesonephros, drainage of its duct into the cloaca, and early appearance of the metanephros. Gonadal development proceeds in parallel with renal development and is depicted in the far-right panel

a

b Gut

Mesonephric duct

Urachus

Allantois

Mesonephric duct

Metanephric diverticulum

Bladder

Renal pelvis

Cloaca

Cloaca

c

d

Ureter

e Cephalic major calyx

Renal pelvis Ureter

Renal pelvis Caudal major calyx Ureter

Buds of arched collecting tubules Primary straight collecting tubules Metanephrogenic tissue Developing minor calyces

Fig. 17.4  Diagram demonstrating sequential development of the kidney from the ureteric bud and metanephros

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a

b Mesonephros

Urogenital sinus

Mesonephric duct

Cloacal membrane

Metanephric diverticulum

Mesonephros

Metanephric diverticulum

Urorectal septum

Mesonephric duct

c

d

Allantois Vesical part Genital tubercle

Pelvic part

Mesonephros Urogenital sinus

Mesonephric duct

Phallic part

Metanephros (primordium of permanent kidney)

Rectum

Ureter

Mesonephric duct Mesonephros

e

f

Gonad Mesonephros

Metanephros Urinary bladder

Metanephros Ureter Ureter

Urorectal septum

Rectum

Mesonephric duct Pelvic part of urogenital sinus

g

h Uterine tube

Urachus

Uterus

Kidney

Urachus

Ovary

Urinary bladder

Kidney Testis Ureter

Penis

Clitoris Vagina

Ductus deferens

Spongy urethra

Female

Fig. 17.5  Diagram depicting the sequential division of the cloaca into the urogenital sinus and the rectum, as well as development of the urinary bladder and urethra. The association between the developing kid-

Male

neys and gonads, as well as their relationships to the cloaca, urogenital sinus, and bladder are shown. Panels a, c, e, g, and h are lateral views. Panels b, d, and f are dorsal views

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Normal Anatomy Kidney The normal kidney is a bean-shaped organ that has a smooth convex contour along its anterior, posterior, and lateral borders. The concave medial surface of the kidney is the renal hilum, which is in continuity with the renal sinus, a centrally located cavity. The renal sinus contains the collecting system of the kidney including the calyces and pelvis, as well as the main branches of the renal artery and renal vein. The remainder of the renal sinus contains fat that increases with age. Infant The anatomy and ultrasound appearance of the kidney vary with age. In the premature infant and neonate, the echogenicity of the renal cortex is equal to or greater than that of the liver. This is probably due to a greater volume of glomeruli in the renal cortex compared to adults. The renal pyramids are more prominent and hypoechoic in the neonatal kidney than in the older child and adolescent (Fig.  17.6). This likely reflects the relatively larger medullary volume in the neonatal kidney relative to the older child or adult. In newborns, a transient increase in echogenicity of the tips of the renal pyramids is commonly seen. This is physiologic and usually resolves after a few days as the glomerular filtration rate increases [7]. The pyramids attain an adult appearance by around 12 months of age. The renal sinus is less echogenic in the neonatal kidney relative to the adult. This is believed to be due to a paucity of renal sinus fat in the neonatal kidney [8]. Older Child and Adolescent Renal cortical echogenicity decreases in the first year of life and becomes isoechoic or slightly less echogenic than

L

Fig. 17.6  Normal appearance of the kidney in a neonate. Longitudinal grayscale ultrasound image of the right kidney in 1-week-old boy reveals renal cortical echogenicity equal to that of the adjacent liver (L). The renal pyramids (arrows) appear markedly hypoechoic, and there is a paucity of renal sinus fat (asterisk)

the liver and spleen. The renal pyramids also become less prominent and more echogenic (Fig. 17.7). Renal sinus fat increases with age resulting in increased echogenicity. At any age, the maximum anteroposterior diameter of the renal pelvis should not exceed 1 cm [1]. Anatomic Variants Fetal Lobulation

These are remnants of interlobar grooves that develop during progressive fusion of the embryonic renal parenchymal lobules termed “renunculi” (Fig. 17.8). They may be mistaken for renal scars or tumors. However, the indentations are regularly spaced and spare the pyramids, whereas the parenchyma overlying the pyramids is thinned with scarring [9].

L

Fig. 17.7  Normal appearance of the kidney in a 4-year-old female. Longitudinal grayscale ultrasound image of the right kidney demonstrates renal cortical echogenicity less than that of the adjacent liver (L). The renal pyramids (arrowheads) are much less perceptible compared to those of the neonate, and the echogenic central renal sinus (asterisk) is more prominent

S

Fig. 17.8  Fetal lobulations in a 6-month-old male. Longitudinal grayscale ultrasound image of the left kidney depicts an undulating contour related to parenchymal indentations (arrowheads) that are located between the renal pyramids. S, Spleen

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Junctional Parenchymal Defect

Partial fusion of renunculi results in the so-called junctional parenchymal defect, which appears as an echogenic triangle in the renal cortex. This should be differentiated from a parenchymal scar by its characteristic location, at the border of the upper pole and interpolar region of the kidney, and its continuity with the renal sinus (Fig.  17.9). A parenchymal scar is characterized by loss of renal cortex, whereas a junctional parenchymal defect is not [10]. Dromedary Hump

A dromedary hump is a focal protrusion in the lateral border of the midportion of the left kidney caused by indentation of the renal cortex by the adjacent spleen. It is one of the

classical “renal pseudotumors”; however, the characteristic location, similar echogenicity to renal cortex, and further extension of the adjacent calyx into the dromedary hump relative to other calyces are helpful distinguishing features (Fig. 17.10) [11]. Hypertrophied Column of Bertin

A hypertrophied column of Bertin is another anatomical variant that can be mistaken for a renal tumor. It appears as an oval or round mass of similar echogenicity to the renal cortex and extends to the renal sinus between two medullary pyramids. A smooth overlying renal contour is a unique feature that helps differentiate a hypertrophied column of Bertin from a renal mass (Fig. 17.11) [12].

L

Fig. 17.9  Junctional parenchymal defect in a 3-year-old female. Longitudinal grayscale ultrasound image demonstrates a peripheral triangular echogenic focus (arrowhead) in the upper pole of the right kidney. L, Liver

a

Fig. 17.10  Dromedary hump in a 2-year-old female. (a) Longitudinal grayscale ultrasound image reveals a focal protrusion of the lateral aspect of the left kidney (between arrows) that has a mass-like appearance. A normal medullary pyramid (arrowhead) is seen in the central

Fig. 17.11  Hypertrophied column of Bertin in a 12-year-old male. Longitudinal grayscale ultrasound image of the right kidney (cursors) demonstrates an oval mass (arrows) of similar echogenicity to the renal cortex located between 2 pyramids (asterisks) and extending to the renal sinus. The contour of the kidney overlying the “mass” (arrowheads) has a smooth contour

b

portion of the “mass,” and the surrounding renal parenchyma is normal in thickness and echogenicity. (b) Longitudinal color Doppler ultrasound image depicts normal vessels (arrowheads) within the mass-like zone

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Fig. 17.12  Compensatory hypertrophy of the left kidney in a 3-year-­old male with a non-functioning right multicystic dysplastic kidney (MCDK). Longitudinal grayscale ultrasound images of the right (a) and left (b)

flanks show an MCDK (arrowheads) on the right surrounded by abnormal echogenic parenchyma. The normal left kidney (cursors) is larger than expected for age, measuring 8.9 cm in length

Fig. 17.13  Compound calyx in a 15-year-old male. Longitudinal grayscale ultrasound image demonstrates a branching, hypoechoic focus in the lower renal pole (arrow). The overlying renal contour is normal without parenchymal thinning

Compensatory Hypertrophy

Compensatory hypertrophy of the kidney is a common cause of unilateral renal enlargement. It can occur in association with a contralateral renal congenital anomaly such as a multicystic dysplastic kidney (MCDK) where there is reduced or absent renal function, or in association with acquired abnormalities such as unilateral scarring or following nephrectomy (Fig.  17.12). It occurs in almost all children with a single kidney. Compensatory renal hypertrophy can be detected in utero and eventually develops regardless of whether or not the nonfunctioning kidney is removed [13, 14]. Compound Calyx

Compound calyces are associated with compound pyramids and they usually appear as branching, hypoechoic foci in the upper and lower renal poles. They are associated with a normal renal contour without cortical thinning or calyceal dis-

tortion (Fig. 17.13). These features help to distinguish them from abnormalities such as obstruction of the upper pole of a duplex system, focal caliectasis, simple cyst, hydrocalyx due to infundibular stenosis, or a hypoechoic mass [15]. Accessory Renal Artery

Accessory renal arteries are a very common, clinically relevant variant of renal vasculature, especially in the assessment of renal transplant donors, renal artery embolization, or diagnostic search for renal artery stenosis. They occur in up to one third of the population (30% unilateral; 10% bilateral; very rarely more than two). Accessory renal arteries can be hilar or polar arteries; the former typically demonstrates a similar caliber to the main renal artery, while the latter is usually smaller (Fig. 17.14). The most common origin of a single renal artery is at the level of L1-L2, whereas accessory renal arteries can arise

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Fig. 17.14 Accessory polar renal artery in a one-month-old male. Longitudinal color Doppler ultrasound images of the left kidney with spectral analysis show (a) the main renal artery (arrow) extending from

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the aorta (A) to the renal hilum. (b) An accessory polar renal artery (arrowhead) arises more distally (arrowhead) from the aorta (A) and extends to the lower renal pole

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Fig. 17.15  Retroaortic left renal vein in a 9-year-old male. (a) Transverse grayscale ultrasound image shows a markedly compressed retroaortic left renal vein (arrowheads) as it passes behind the aorta (A).

C, Inferior vena cava (IVC); L, proximal left renal vein. (b) Axial contrast-enhanced CT image confirms the presence of a retro-aortic left renal vein (arrow). C, IVC; L, proximal left renal vein

from the aorta or iliac arteries anywhere from the level of T11 to the level of L4. They can also very rarely arise from the lumbar or mesenteric arteries [16, 17].

the aorta to join the inferior vena cava (IVC) (Fig. 17.15), or less commonly the iliac veins. Preoperative recognition of this variant is very important in donor nephrectomy, especially for a laparoscopic approach. Retroaortic left renal vein can present clinically as hematuria secondary to venous congestion from compression of the renal vein against the spine [18].

Retroaortic Left Renal Vein

Retroaortic left renal vein is a rare (2–3%) vascular variant of renal anatomy where the left renal vein courses dorsal to

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b RK C

RK

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C A

Fig. 17.16  Circumaortic left renal vein in a 10-day-old female. (a) Coronal color Doppler ultrasound image with spectral analysis shows normal venous flow in the left renal vein (arrowheads) proximal to its bifurcation. A, Aorta; C, IVC; RK, right kidney. (b) Coronal color Doppler ultrasound

image of the aorta and IVC shows that the left renal vein bifurcates into an anterosuperior branch (arrows) and a posteroinferior branch (arrowheads) that encircle the aorta (A) before each drains separately into the IVC (C). RK, Right kidney. The left kidney is outside the field of view

Circumaortic Left Renal Vein

is believed that the presence of a ureteral jet is a sign of a non-obstructed UVJ. The complete absence of a ureteral jet on either side is suggestive of ipsilateral UVJ obstruction [21, 22].

Circumaortic left renal vein is the most common anatomical variant of the left renal venous system, occurring in about 5–7% of the population. The left renal vein bifurcates into anterior and posterior branches that encircle the abdominal aorta (Fig. 17.16). Recognition of a circumaortic left renal vein is critical during retroperitoneal surgery or nephrectomy to avoid potentially fatal hemorrhage [19].

Ureter Normal Anatomy The ureter is a tubular structure that extends through the retroperitoneum from the kidney to the bladder. The proximal ureter tapers smoothly from its origin at the ureteropelvic junction (UPJ) and terminates at the ureterovesical junction (UVJ). The distal portion of the ureter extends obliquely through the bladder wall and opens into the bladder lumen at the ureteral orifice. The ureteral wall consists of three muscular layers with an outer adventitial layer that contains blood vessels and lymphatics. The ureter lies adjacent to the psoas muscle and passes anterior to the common and external iliac vessels as it enters the pelvis. Ureteral Jets When urine in the ureter approaches the vesicoureteral junction, it is ejected into the urinary bladder by smooth muscle contraction at the vesicoureteral sphincter. Prior research has shown that color Doppler imaging is more sensitive for demonstrating ureteral jets compared to grayscale ultrasound [20]. On grayscale ultrasound, ureteral jets are seen as a burst of low intensity echoes emitted from the ureteral orifice into the urinary bladder (Fig. 17.17). It

Bladder Normal Anatomy The bladder is located in the pelvis, posterior to the pubic bones and anteroinferior to the peritoneal cavity. The peritoneum is reflected off the anterosuperior aspect of the bladder. The bladder trigone is a smooth triangular region within the inner posterior portion of the bladder that is demarcated by the ureteric and internal urethral orifices. The bladder neck is the zone at the base of the trigone that surrounds the internal urethral orifice and opens into the urethra. Specialized ­detrusor smooth muscle bundles encircle the bladder neck and form the internal urethral sphincter. The bladder neck and trigone are constant in shape and position, whereas the remainder of the bladder undergoes changes in shape and position depending on the volume of contained urine. The normal urinary bladder has a thin wall. Bladder volume and wall thickness are affected by the degree of bladder filling (Fig. 17.18). The distal ureters may be visible at the bladder base, especially if the child is well hydrated, likely related to the normal transient passage of urine associated with peristalsis. Bladder wall thickness can increase with inflammation or muscular hypertrophy. In infants, the urinary bladder is partially intra-abdominal in location and only assumes a more pelvic position with growth. It does not truly become pelvic until about the sixth year of life, and the ureters are completely intra-abdominal in location until then as well.

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Fig. 17.17  Ureteral jets in a 15-year-old male. Transverse color Doppler ultrasound images of the bladder show jets of urine from the right (a) and left (b) ureteral orifices

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d

Fig. 17.18  Normal bladder in a 4-year-old male. Transverse (a) and longitudinal (b) grayscale ultrasound images obtained with a moderate degree of filling show a thicker bladder wall (arrowheads) than trans-

verse (c) and longitudinal (d) images obtained several minutes later with the bladder markedly filled

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Fig. 17.19  Bladder ears in a 2-week-old male. Transverse grayscale (a) and contrast-enhanced voiding urosonography (ceVUS) (b) images of the pelvis demonstrate outpouchings (asterisks) from the right and

left anterolateral aspects of the bladder in keeping with bladder ears. (c) Image from a voiding cystourethrogram (VCUG) depicts the bladder ears (arrows) protruding into the right and left inguinal canals

The urachal remnant connects the bladder to the umbilicus. The dome of an unfilled bladder lies midway between the pubis and the umbilicus. With filling, the bladder dome may reach the umbilicus [23].

Bladder ears are usually asymptomatic and resolve spontaneously. Nevertheless, failure of recognition during inguinal hernia repair can potentially result in injury due to partial or complete excision of bladder ears contained in the hernia sac [25].

Anatomic Variants

Urethra

Bladder Ears

Normal Anatomy The urethra is a tubular structure that connects the urinary bladder neck to the urethral meatus for excretion of urine from the body. In males and females, the internal and the external sphincters control urethral function. The involuntary internal sphincter is formed by the smooth muscles lining the bladder neck and urethra and is innervated by the sympathetic nervous system. The somatic external sphincter is innervated by the pudendal nerve. The proximal urethra can be imaged via a transabdominal approach, while a transperineal approach is useful for imaging the more distal portions of the urethra in both genders. In

Bladder ears are a normal physiologic finding in young infants, where the lateral portions of the urinary bladder protrude into the inguinal canals. The higher relative position of the urinary bladder in infants compared to its position in adults places it in close proximity to the internal inguinal rings. Bladder ears can be demonstrated on voiding cystourethrography, intravenous pyelography, ultrasound, and CT. On ultrasound, bladder ears are seen as fluid-filled diverticula extending from the lateral aspect of the bladder (Fig. 17.19). Unlike true diverticula, they are smooth walled, with a wide neck, and more transient in nature [24].

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Fig. 17.20  Normal urethra in a 38-day-old male. (a) Longitudinal transperineal grayscale ultrasound image depicts the urethra (arrowheads) extending from the base of the bladder (B) along the length of the penis with a small amount of anechoic urine (arrow) within the

U

V R

proximal urethra. (b) Longitudinal transperineal ceVUS image shows a normal urethra (arrowheads). B, Bladder. (c) Image from a VCUG confirms a normal bladder and urethra

of the urethra. The narrowest portion of the urethra is the membranous portion where it passes through the external urethral sphincter. The external sphincter in males is located just inferior to the prostate gland and surrounds the membranous urethra. The penile urethra extends through the corpus spongiosum along the length of the penis (Fig. 17.20). The urethral glands (glands of Littré) drain into the penile urethra. Female Urethra

Fig. 17.21  Normal female urethra. Transperineal longitudinal grayscale ultrasound image depicts the urethra (U), vagina (V), and rectum (R)

older, sexually active teenage girls, a transvaginal approach can also be considered [26, 27]. Urine is anechoic on ultrasound where it is seen centrally in the tubular urethra. The urethra is located anterior to the vagina in females, anterior to the rectum in males, and deep to the pubic symphysis in both genders. Male Urethra

The male urethra originates at the bladder neck and opens at the external urethral meatus. The male urethra is approximately 5 cm in length at birth, 8 cm at 3 years of age, and 17 cm in adulthood. The prostatic and membranous segments comprise the posterior urethra in males, while the bulbar and penile segments comprise the anterior urethra. The prostatic utricle, ejaculatory ducts, and prostatic ducts drain into the verumontanum, a ridge in the floor of the posterior urethra at the junction of the prostatic and membranous segments

The female urethra extends from the bladder neck and opens directly onto the perineum between the clitoris and the vagina (Figs. 17.21 and 17.22). It is approximately 2 cm in length at birth, 2.5 cm at 5 years of age, and 4 cm in adulthood. The external urethral sphincter is located within the distal two thirds of the urethra and is composed of striated muscle. The urethra plane extends obliquely in an anteroinferior direction. The proximal two-thirds of the female urethra are lined by transitional epithelium, whereas the distal one third is lined by stratified squamous epithelium.

Congenital Anomalies  nomalies of Renal Number, Position, Fusion, A and Growth Congenital renal anomalies are not uncommon, occurring in 3–5 per 1000 live births. They are considered the leading cause of renal failure in children and may predispose to stone formation, infection, hypertension, and renal failure [28].

Renal Agenesis Renal agenesis refers to complete absence of one or two kidneys that results from failure of induction of the metanephric blastema by the ureteric bud. Renal agenesis can be diagnosed on prenatal ultrasound imaging. Bilateral renal agenesis is

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Fig. 17.22  CeVUS of the urethra in a 17-month-old female. (a) Longitudinal transperineal image shows a normal urethra (arrowheads). B, Bladder. (b) Image from a VCUG confirms a normal bladder and urethra

is more common than renal agenesis). Knowledge of the embryological pathway of the normal ascent of the kidney is important to avoid missing a kidney in an abnormal position somewhere along this path. L

Fig. 17.23  “Lying down” adrenal sign in a 6-year-old female with right renal agenesis. Longitudinal grayscale ultrasound image of the right renal fossa demonstrates absence of the kidney and a flattened, elongated appearance of the adrenal gland (arrows). L, Liver

usually incompatible with life; it results in oligohydramnios that leads to severe pulmonary hypoplasia [28]. Unilateral renal agenesis is much more common, occurring in 1/1300 pregnancies. Most children with unilateral renal agenesis are asymptomatic and have a normal life expectancy [29]. Ultrasound features include absence of the kidney and ipsilateral renal artery with a flattened appearance of the ipsilateral adrenal gland, the so-called “lying down” adrenal sign (Fig. 17.23). Careful examination of the abdomen should be carried out to search for an ectopic kidney (which

Renal Duplication Renal duplication is the most common congenital renal tract anomaly, with an incidence of 0.7% in the general population and 2–4% in patients investigated for urinary tract infection (UTI) [30]. It is much more common in girls than boys. Renal duplication can be unilateral or bilateral, partial or complete. The spectrum of partial duplication ranges from a bifid pelvis with a single ureter to bifid ureters, which unite at some point before emptying into the urinary bladder. Partial duplication accounts for 95% of cases of all renal duplications, is usually asymptomatic, and is clinically insignificant with no increased risk of urinary tract disorders compared to the general population. In a complete duplication, there are two ureters that drain separately into the urinary bladder. Patients with complicated renal duplication may present with UTI, failure to thrive, abdominal mass, hematuria, or symptoms of bladder outlet obstruction related to a ureterocele. According to the Weigert-Meyer rule, the future lower pole ureter separates early from the wolffian duct and migrates superiorly and laterally during bladder growth, inserting orthotopically into the bladder trigone, whereas the upper pole ureter remains with the wolffian duct longer and inserts ectopically in the bladder or into a wolffian duct remnant [31]. In a complete duplication, the lower pole ureter is prone to vesicoureteral reflux (VUR), whereas the upper pole ureter is more likely to insert ectopically with or without a uretrocele and is often obstructed.

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Fig. 17.24  Renal duplication in a 10-year-old female. Longitudinal grayscale ultrasound image of the right kidney shows an oblique band of normal renal parenchyma (asterisk) that divides the renal sinus (arrows) into two parts

On ultrasound, a duplex kidney is sometimes larger than a normal single-system kidney. The echogenic renal sinus may appear divided by an intervening column of renal parenchyma (Fig.  17.24). If there is associated vesicoureteral reflux to the lower moiety or obstruction of the upper moiety, hydronephrosis may be present (Figs. 17.25 and 17.26). Hydronephrosis of differing severity in the upper and lower moieties is a useful indicator of the presence of a completely duplicated system. It is not uncommon for the upper pole moiety to be dysplastic and replaced by cysts. The vast majority of duplex kidneys do not require intervention. Depending on the function of the upper moiety, an ectopic ureter may be treated surgically with ureteroureterostomy (where the ectopic upper pole ureter is anastomosed to the normally located lower pole ureter) or with reimplantation to the urinary bladder. A nonfunctioning or dysplastic renal moiety may require heminephrectomy and resection of the proximal ureter [32].

Supernumerary Kidney A supernumerary kidney is an accessory kidney, a very rare congenital anomaly thought to result from an abnormal division in embryonic life of the nephrogenic cord into two metanephric blastemas with or without division of the ureteric bud. The supernumerary kidney may have partially or completely duplicated ureters [33]. It is usually located on the left side of the abdomen caudal to the normotopic kidney and very rarely may be bilateral. The accessory kidney is usually small in size with reduced function. Patients may present with fever, abdominal pain, or abdominal mass, which are related to hydronephrosis, pyelonephritis, stone disease, or tumor. A supernumerary kidney can be evaluated by ultrasound (Fig. 17.27), CT, MR imaging, or nuclear scintigraphy.

c

Fig. 17.25  Bilateral duplex kidneys in a 3-month-old female with vesicoureteral reflux and unilateral obstruction. (a) Longitudinal grayscale ultrasound image reveals a duplex right kidney (cursors) with marked dilation of the lower pole collecting system (asterisk) and diffuse thinning of the overlying renal parenchyma. The upper pole moiety appears normal. (b) Longitudinal grayscale ultrasound image of the left kidney demonstrates significant dilation of the upper pole collecting system (asterisk) with diffuse thinning of the overlying renal parenchyma. Mild dilation of the lower pole collecting system (arrowhead) is also present. (c) Image from a fluoroscopic VCUG shows reflux (arrowheads) into the right upper and lower pole renal collecting systems with partial ureteral duplication, and into the left lower pole moiety. The absence of reflux to the dilated left upper pole moiety indicates obstruction

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Fig. 17.26  Duplex kidney with ectopic ureterocele in a 12-month-old female. (a) Longitudinal grayscale ultrasound image reveals a duplex left kidney with severe collecting system dilation (asterisk) and a tortuous, dilated ureter (arrows). There is also mild dilation of the lower pole

collecting system (arrowhead). (b) Longitudinal grayscale ultrasound image of the pelvis demonstrates the dilated distal left ureter (U) and the ectopic ureterocele (asterisk) at the base of the bladder (B)

Renal Ectopia Simple Ectopia During embryological development, the kidneys normally ascend from the pelvis to the retroperitoneum. Renal ectopia occurs as a result of arrested migration of the kidney. Ectopia can be either simple or crossed. In simple ectopia, the kidney and the ureter are on the expected side of the spine and are usually located in the pelvis. On ultrasound imaging, the kidney is customarily smaller, malrotated, and has a dysmorphic configuration (Fig. 17.28). Due to the superficial position of the pelvocalyceal system compared to the normal kidney, the normal sinus echo complex is absent in an ectopic kidney [34]. The ureter is usually short. The ectopic kidney retains the embryonic aorto-iliac branches that usually degenerate during normal ascent. Very rarely, an ectopic kidney can be located in the posterior thorax, usually on the left side.

Fig. 17.27  Supernumerary kidney in a 6-year-old male. (a) Longitudinal grayscale ultrasound image of the right renal fossa demonstrates two fused kidneys (cursors). K1, Kidney 1; K2, kidney 2. (b) Longitudinal grayscale ultrasound image of the left renal fossa reveals a single normalappearing kidney (cursors)

Ultrasound is useful for morphological characterization, while nuclear scintigraphy and MR urography (MRU) are useful for functional assessment. Owing to the frequent presence of associated pathology, two-thirds of these kidneys are symptomatic and will ultimately require nephrectomy.

 rossed Renal Ectopia C In crossed renal ectopia, the ectopic kidney is positioned on the side opposite to its expected location in the retroperitoneum. The left kidney is more often involved than the right. The upper pole of the ectopic kidney usually fuses with the lower pole of the orthotopic kidney. The ureter draining the ectopic kidney crosses the midline to drain into the bladder in a normotopic location on the trigone. Ultrasound will show a “mass” consisting of the fused kidneys with two renal sinuses and absence of a kidney in the contralateral renal fossa (Figs. 17.29 and 17.30). Crossed renal ectopia can be an incidental finding, although there is an increased risk of hydronephrosis, renal stones, and infection in these kidneys [35].

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Fig. 17.28  Ectopic left kidney in a 3-month-old male. (a) Longitudinal grayscale ultrasound image of the left pelvis shows a small, dysplastic kidney (arrow) with a dilated ureter (U) adjacent to the bladder (B).

B

(b) Longitudinal grayscale ultrasound image of the left flank reveals an empty renal fossa. S, Spleen

RK

Fig. 17.29  Crossed renal ectopia in a 2-year-old male. Oblique longitudinal grayscale ultrasound image of the right upper quadrant demonstrates fusion of the lower pole of a normally located right kidney (R) to the upper pole of the ectopic left kidney (L)

Fig. 17.30  Crossed renal ectopia in a 6-month-old female with a multicystic dysplastic kidney (MCDK). Oblique longitudinal grayscale ultrasound image of the right upper quadrant shows fusion of the lower pole of the right kidney (RK) to the upper pole of an ectopic left MCDK (arrows)

Horseshoe Kidney Horseshoe kidney is the most common congenital renal fusion anomaly, occurring in approximately one in 400 live births with a male predominance of 2:1 [35]. It is reported in about 20% of individuals with trisomy 18 and in at least one third of females with Turner syndrome [36]. In this anomaly, the lower poles of both kidneys fuse to produce an isthmus, either fibrous or parenchymatous, that crosses the midline anterior to the aorta. The isthmus hinders the cranial ascent and normal rotation of the kidney as it encounters the inferior mesenteric artery. As a result, the lower poles of the kidneys are rotated medially and the kidney is low-lying. A horseshoe kidney usually receives anomalous blood supply either from the lower aorta or iliac arteries. There is an increased incidence of stone formation, infection, and risk of renal obstruction due to abnormal orientation

of the ureters. A horseshoe kidney is also more susceptible to traumatic injury. A horseshoe kidney is associated with additional congenital anomalies in about one third of patients, that can include vertebral, anorectal, tracheal, and esophageal malformations [37]. Ultrasound features include abnormal rotation and inferior location of the kidney resulting in poor visualization of the inferior pole and frequent underestimation of the length of the right and left moieties. The renal pelves are located anteriorly, and an isthmus of tissue is seen crossing anterior to the spine and retroperitoneal vessels (Fig. 17.31).

Pancake Kidney Pancake kidney, sometimes referred to as a cake, discoid, or lump kidney, is a very rare anomaly representing less than 2% of renal fusion anomalies [38]. It results from fusion of the

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Fig. 17.31  Horseshoe kidney in a 5-year-old male. Transverse grayscale ultrasound image through the mid-abdomen shows fusion of the lower poles of the right (K) and left kidneys (L) by an isthmus of renal parenchyma (cursors) anterior to the spine (S)

superior and inferior poles of the kidneys with no intervening septum. It is usually located in the pelvis anterior to the aortic bifurcation. With very few exceptions, a pancake kidney is drained by two separate, anteriorly located ureters that enter the urinary bladder in a normal location. Pancake kidney is at risk of similar complications as horseshoe kidney.

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To address the perceived need for a unified classification system with a widely accepted terminology for the diagnosis and management of antenatal and postnatal urinary tract dilation, a classification system was devised in 2014 during a consensus meeting of eight medical societies involved in the prenatal and postnatal diagnosis and management of urinary tract dilation [40, 41]. The urinary tract dilation or UTD grading system is correlated with the risk of postnatal uropathy and is based on six ultrasound features: (1) anterior-posterior renal pelvic diameter, (2) calyceal dilation with differentiation between postnatal central and peripheral calyceal dilation, (3) renal parenchymal thickness, (4) renal parenchymal appearance, (5) bladder abnormalities, and (6) ureteral abnormalities (Fig. 17.32). For antenatal studies, an additional ultrasound feature that is reported is the quantity of amniotic fluid. Normal imaging parameters are also defined. A postnatal follow-up scheme has also been proposed based on the UTD classification (Fig. 17.33) [40]. The hope is that future comparisons of the grading system with clinical outcomes such as renal function and the need for surgical intervention will lead to refinements in the classification scheme and thereby increase its value in guiding the clinical management of infants and children with hydronephrosis.

 reteropelvic Junction Obstruction U Ureteropelvic junction obstruction (UPJO) is the most comRenal Hypoplasia mon cause of neonatal hydronephrosis and congenital uriRenal hypoplasia, which is a congenitally small kidney with nary tract obstruction. Congenital UPJO is usually caused by fewer calyces and papillae than normal (less than 6), results intrinsic stenosis of the proximal ureter at the UPJ and less from incomplete renal development. The function of a hypo- commonly by extrinsic compression from a crossing renal plastic kidney can be normal or slightly reduced. vessel. Although the underlying mechanism is uncertain, it Renal hypoplasia is usually unilateral and can be global or is thought that there is abnormal development of the circusegmental. Global hypoplasia can be differentiated from renal lar musculature and/or collagen fibers of the proximal ureatrophy resulting from chronic pyelonephritis by the smooth ter. The majority of cases are identified antenatally, although outline and normal calyceal system in the former compared to UPJO can present at any age. the irregular outline and focal dilation of renal calyces resultIn the neonatal period, UPJO is usually asymptomatic and ing from scarring in the latter. Differentiation of global hypo- presents with a palpable abdominal mass while in older chilplasia from a small kidney with a smooth outline resulting dren it can present with abdominal pain, hematuria, recurrent from chronic vascular disease is challenging. Segmental renal urinary tract infection, stone formation, and occasionally, hypoplasia, also known as Ask-Upmark kidney, is a curable intermittent pain after drinking large volumes of fluid or flucause of secondary hypertension in young adults [28, 39]. ids with a diuretic effect. Renal dysplasia may develop as a result of congenital UPJO, with the degree of dysplasia dependent on the severity Anomalies of the Renal Collecting System of the obstruction and its time of onset during gestation [42]. and Ureter If obstruction is incomplete and develops after the 36th week of gestation, varying degrees of hydronephrosis are present Classification of Prenatal and Postnatal without histologic evidence of renal dysplasia. Incomplete Hydronephrosis obstruction that develops between the 10th and 36th week of Urinary tract dilation is identified in 1–2% of fetuses on prena- gestation may result in dysplastic parenchymal changes with tal ultrasound imaging and is associated with a wide range of or without cyst formation along with hydronephrosis. At the possible postnatal outcomes. The relative absence of evidence-­ most severe end of the spectrum, multicystic dysplastic kidbased information correlating the severity of prenatal dilation ney results from complete obstruction before 8–10 weeks of to postnatal urologic abnormalities has led to significant varia- gestation [43]. tion in the clinical management of infants and children with Rupture of the renal collecting system from severe obstrucantenatally diagnosed urinary tract dilation. tion can also occur in utero resulting in urinary ascites and

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Fig. 17.32  Urinary Tract Dilation (UTD) Risk Stratification—Postnatal Presentation for UTD P1 (Low Risk), UTD P2 (Intermediate Risk), and UTD P3 (High Risk). Stratification is based on the most concerning ultrasound finding. APRPD, Anterior-posterior renal pelvic diameter; abnl,

abnormal. (From Nguyen HT, Benson CB, Bromley B, Campbell JB, Chow J, Coleman B, et al. Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system. J Pediatr Urol. 2014;10(6):982–98. [40])

Fig. 17.33  Management schema based on Urinary Tract Dilation (UTD) classification system risk stratification of UTD P1, UTD P2, and UTD P3. (From Nguyen HT, Benson CB, Bromley B, Campbell JB, Chow J,

Coleman B, et al. Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system. J Pediatr Urol. 2014;10(6):982–98. [40])

subcapsular urinoma. Congenital UPJO may be associated with other genitourinary abnormalities, including vesicoureteral reflux, ureterovesical junction obstruction (UVJO), duplex kidney, horseshoe kidney, and crossed fused ectopia. Ultrasound imaging will often show dilated calyces communicating with a dilated renal pelvis (Fig.  17.34). The proximal ureter appears collapsed and the urinary bladder is normal. Occasionally, the ipsilateral ureter may be

dilated due to associated vesicoureteral reflux or UVJO. Renal parenchymal thickness and echogenicity are variable depending on the chronicity of the condition and the degree of associated parenchymal dysplasia, if present. Renal dysplasia manifests as increased cortical echogenicity with or without cysts. Doppler ultrasound is useful in differentiating a dilated renal pelvis from prominent renal vessels and can also identify aberrant renal vessels [43].

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Fig. 17.34  Ureteropelvic junction obstruction in a 6-year-old female. Longitudinal (a) and transverse (b) grayscale ultrasound images of the right kidney demonstrate moderate-to-severe hydronephrosis with mild diffuse thinning of the renal parenchyma (arrowheads). Anteroposterior

pelvic diameter measurement is obtained at the renal hilum (cursors). (c) Image from technetium (Tc)-99m-mercaptoacetyltriglycine (MAG3) diuretic reno­graphy obtained 1 hour after injection shows retention of radioisotope in the right renal collecting system (arrow). R, Right side

Indications for surgical intervention include pain, infection, and renal stones; massive hydronephrosis with a renal pelvic diameter greater than 5 cm; increasing hydronephrosis and decreased renal function (generally less than 40% of split renal function or serial loss of more than 10% function); and patient and/or parental request for definitive treatment [44]. Surgery usually consists of a dismembered pyeloplasty, where the obstructed segment is excised and the renal pelvis is re-anastomosed to the ureter.

plastic and have a semilunar configuration rather than a normal triangular shape. Calyceal fornices and papillary impressions are absent. The abnormal calyces are also increased in number and have a faceted, polygonal appearance. The renal pelvis is usually normal in size. Patients are generally asymptomatic. However, the dilated calyces can predispose to stasis, infection, and stone formation. Rarely, congenital megacalyces can coexist with primary ­megaureter, and recognition of their coexistence is important in order to avoid unnecessary surgery on the ureteropelvic junction [46, 47]. Ultrasound findings include a large kidney with normal cortical thickness [48]. The calyces will appear dilated while the renal pelvis will usually be normal in size, a potential clue to the diagnosis. If there is coexisting primary megaureter, vesicoureteral reflux, or another cause of distal obstruction, the renal pelvis may appear dilated (Fig.  17.35). MRU or contrast-­enhanced CT will demonstrate the polygonal appearance of the dilated calyces. No treatment is required unless the condition is complicated by infection or stone formation, which then may require specific management.

Ureteropelvic Junction Obstruction Caused by Crossing Vessel About 10% of cases of ureteropelvic junction obstruction (UPJO) are caused by an aberrant or accessory renal artery that crosses the lower pole of the kidney resulting in compression of the UPJ and blockage of urine flow. Approximately 60% of patients will present with recurrent renal colic (pain, nausea, vomiting) compared to only10% with intrinsic UPJO. Since vascular obstruction is usually intermittent, most patients have normal renal function. Ultrasound imaging during a symptomatic episode is usually necessary to make the diagnosis of UPJO. Color Doppler ultrasound can sometimes directly visualize the crossing vessel. If UPJO is thought to be caused by a crossing vessel, a dismembered pyeloplasty is performed. An open surgical approach is recommended rather than an endoscopic or laparoscopic pyelotomy in order to avoid potential vascular complications [45]. Re-anastomosis is performed anterior to the crossing vessel.

Congenital Megacalyces Congenital megacalyces is an anomaly characterized by nonobstructive, nonprogressive calyceal dilation that can mimic hydronephrosis. The medullary pyramids are hypo-

 ongenital Infundibulopelvic Stenosis C Infundibulopelvic stenosis is an exceedingly rare form of congenital calyceal dilation resulting from stenosis of the infundibula, which drain to a variably hypoplastic or stenosed renal pelvis. Some authors consider this disorder an obstructive dysplastic renal disease. It can be unilateral or bilateral and is often associated with other congenital anomalies in the ipsilateral or contralateral kidney (e.g., renal malrotation, megaureter, multicystic dysplastic kidney, renal agenesis, and vesicoureteral reflux). Associated malformations can also involve the skeletal, cardiovascular, gastrointestinal, and nervous systems [49].

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Fig. 17.35  Congenital megacalyces in an 11-year-old female with a neurogenic bladder. Longitudinal grayscale ultrasound images of the right (a) and left (b) kidneys reveal an increased number of calyces with an abnormal faceted appearance. The renal pelves (asterisks) are mod-

erately dilated, and the renal parenchyma is diffusely thinned. VCUG images demonstrate moderate-to-severe reflux into the right-sided (c) and left-sided (d) renal collecting systems. (e) The neurogenic bladder has an abnormally thickened, trabeculated wall

Ultrasound findings include mild-to-severe calyceal dilation without associated pelvic dilation (Fig. 17.36). MRU or contrast-enhanced CT will provide more detailed anatomical information. There are limited data on the natural history of infundibulopelvic stenosis. However, many cases of unilateral involvement have been observed without evidence of deterioration in renal function. Surgical correction appears unnecessary

in nonprogressive cases, but long-term follow-up and serial renal function monitoring are required. Intervention should be considered in cases of progressive calyceal dilation or renal insufficiency [49]. The goal of surgical intervention is to offer an opportunity to arrest or reduce progressive renal insufficiency. Preoperative three-dimensional modeling with MRU has been used to guide placement of multiple calicocalicostomies that drain to a lower pole ureterocalicostomy [49].

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Fig. 17.36  Congenital infundibulopelvic stenosis in a 16-year-old female. Longitudinal (a) and transverse (b) grayscale ultrasound images of the right kidney demonstrate dilated upper pole calyces (arrowheads). A small stone (white arrows) with distal shadowing is present in

the lower dilated calyx. The renal hilum (black arrow) appears normal, without pelvic dilation. Coronal contrast-enhanced CT images (c, d) depict the dilated upper pole calyces (arrowheads) and stone (white arrow). The renal hilum (black arrow) is normal

Calyceal Diverticulum A calyceal diverticulum is a urine-containing outpouching within the renal parenchyma that communicates with the pelvocalyceal system by a narrow neck. Calyceal diverticula are usually congenital lesions, although some are acquired following infection or rupture of a simple cyst into the collecting system. There are two recognized types. Type 1 is the more common form, which is related to a minor calyx and usually located in the upper pole. Type 2 is less common, larger, and communicates with the pelvis or a major calyx in the central portion of the kidney [50]. Calyceal diverticula are usually asymptomatic and found incidentally on imaging, although they may be complicated by stone formation and infection. They can sometimes be

mistaken for more serious disorders such as a tumor or abscess [51]. On ultrasound examination, a calyceal diverticulum may appear similar to a simple cyst. Demonstration of an infundibulum between the cystic lesion and the collecting system is diagnostic but not always visible (Fig. 17.37). The presence of mobile echogenic material within a calyceal diverticulum is consistent with milk of calcium and also suggests the correct diagnosis [52]. No treatment is required for the majority of calyceal diverticula. However, they may rarely cause renal colic, urinary tract infection, and hematuria, and appropriate treatment will be required. Prior to surgical intervention, confirmation of the diagnosis by MRU or contrast-enhanced CT is required.

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Fig. 17.37  Calyceal diverticulum in a 7-year-old male. (a) Longitudinal grayscale ultrasound image reveals an anechoic cystic structure (calipers) in the interpolar region of the left kidney. (b) Longitudinal color Doppler ultrasound image demonstrates the avascular nature of the

lesion. (c) Right posterior oblique projection from an intravenous pyelogram obtained 30  minutes after contrast administration demonstrates contrast filling of the lesion (arrow), thereby proving its connection with the pelvocalyceal system of the left kidney

 ongenital Ureterovesical Junction Obstruction C Congenital ureterovesical junction obstruction (UVJO) results from narrowing and aperistalsis of the distal ureter or from an ectopic insertion. In “primary megaureter,” the juxtavesical ureter may demonstrate muscular hypoplasia and/ or mural fibrosis, whereas the submucosal tunnel and ureteral orifice are normal. Ultrasound findings include variable dilation of the ureter proximal to the site of narrowing and of the intrarenal collecting system (Fig. 17.38). The lower ureter is often disproportionately dilated compared with the upper ureter and renal collecting system. Hyperperistalsis of the dilated lower ureter is frequently present, with to-and-fro movement of urine readily detectable with real-time imaging [53]. Technetium (Tc)-99m-mercaptoacetyltriglycine (MAG3) diuretic renography is used to assess the degree of obstruction. Most children with congenital UVJO are managed conservatively with a high rate of spontaneous resolution after

1–3 years. Patients with persistent upper tract dilation generally require long-term follow-up since symptoms can occur later in childhood as well as in adulthood. There are no universally accepted guidelines regarding the appropriate timing of surgical intervention for congenital UVJ obstruction. A consensus statement published by the British Association of Paediatric Radiologists in 2014 recommends surgery when the initial differential renal function is less than 40%, especially when associated with massive hydroureteronephrosis; and when there is failure of conservative management (i.e., breakthrough febrile urinary tract infections pain, worsening dilation, or deteriorating differential renal function on serial renographic scans). In patients more than 1 year of age with significant obstru­ ction, ureteral tapering and reimplantation are performed. This procedure may be challenging in infancy with proposed alternatives including insertion of a temporary JJ stent or performance of a refluxing reimplantation [54].

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Fig. 17.38  Ureterovesical junction obstruction in a 6-month-­old female. (a) Longitudinal grayscale ultrasound image of the left kidney (calipers) demonstrates moderate dilation of the pelvocalyceal system. P, Renal pelvis; C, Calyces. (b) Longitudinal grayscale ultrasound image of the

U

pelvis reveals a dilated distal left ureter (U) posterior to the bladder (B). Voiding cystourethrogram was normal (not shown). (c) MAG3 diuretic renography post-­void image obtained at 1 hour reveals delayed washout of radiotracer from the collecting system and ureter. L, Left side

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B

Fig. 17.39  Ectopic ureter in an 8-year-old female. Longitudinal grayscale ultrasound image of the pelvis reveals a dilated distal ureter (calipers) that extends below (arrows) the expected location of the ureterovesical junction. B, Bladder

Ectopic Ureter Ectopic ureter is a ureter that does not insert on the trigone of the urinary bladder. Ectopic ureteral insertion results from caudal, instead of normal cephalic, migration of the ureteral bud due to failure of separation from the wolffian duct with the ureteral opening situated inferior to its usual location. In females, an ectopic ureter may insert anywhere from the bladder neck to the perineum, including into the vagina, uterus, or rectum (Fig. 17.39). When an ectopic ureter terminates distal to the bladder neck and external urethral sphincter, it results in continuous incontinence of urine [31]. In males, an ectopic ureter always inserts above the external sphincter or pelvic floor into the lower bladder, seminal vesicle, vas deferens, or ejaculatory duct so that urinary continence is not affected (Fig.  17.40). However, ectopic ureters in males are frequently associated with obstructive symptoms. Ectopic ureter is associated with a duplex renal collecting system in 70% of cases and is much more common in girls than boys. According to the Weigert-Meyer rule, in a duplex system, the ectopic ureter will drain the upper pole moiety, which inserts inferior and medial to the orifice of the ureter draining the lower renal moiety. The most commonly associated anomaly with an ectopic ureter is dysplasia of the associated renal moiety, with strong correlation between the degree of ectopia and the degree of renal dysplasia. Ultrasound imaging is used to determine whether or not a duplex kidney is present, to document the presence of hydroureter and site of ureteral insertion, and to identify an ectopic ureterocele [55]. Non-dilated ectopic ureters are difficult to demonstrate by ultrasound. In these cases, MRU or contrast-­ enhanced CT can often provide this information [56]. The surgical options for treatment of an ectopic ureter include upper pole hemi-nephrectomy in the setting of

severe upper pole hydronephrosis or poor function. If there is mild hydronephrosis and reasonable function of the upper pole moiety, ureteroureterostomy with anastomosis of the ectopic ureter to the normally located lower moiety ureter with ureteral reimplantation is performed.

Ectopic Ureterocele An ectopic ureterocele is a cystic dilation of the distal submucosal portion of an ectopic ureter that protrudes into the bladder lumen. It is almost invariably associated with a duplex renal collecting system and represents the termination of the ureter from the upper renal moiety. An ectopic ureterocele can be unilateral or bilateral. It is far more common in girls compared to boys [57]. In cecoureterocele, an uncommon type of ectopic ureterocele, the intravesical portion dissects submucosally below the trigone with a tongue-­ like projection of the lumen extending beyond the orifice. This projection may herniate into the urethra and present as a perineal mass [58]. On ultrasound, an ectopic ureterocele appears as a round, thin-walled, anechoic intravesical cystic structure (Fig. 17.26). In the majority of cases, the ureterocele can be seen to connect with a dilated upper pole moiety of a duplex renal system draining into a dilated tortuous ureter [59]. Ectopic ureterocele is usually treated by endoscopic incision and unroofing, after which the ureterocele is collapsed and appears as an echogenic lesion in the urinary bladder base. The ectopic ureter associated with the ureterocele is treated as previously described. Retrocaval Ureter Retrocaval ureter, also known as circumcaval ureter, describes the abnormal course of the proximal ureter posterior to the IVC, after which it emerges to the right of the aorta, eventually lying anterior to the right iliac vessels. It results from anomalous development of the IVC, in particular, failure of development of the right s­ upracardinal system, and persistence of the right posterior cardinal vein. This anomaly almost invariably occurs on the right side. Although retrocaval ureter is usually asymptomatic, it can predispose to partial right ureteral obstruction or recurrent urinary tract infections. Ultrasound will show pelvocalyceal and ureteral dilation down to the level where the ureter crosses behind the IVC. If symptomatic, this anomaly can be treated by surgical relocation of the ureter anterior to the IVC [18]. Vesicoureteral Reflux Vesicoureteral reflux (VUR) is a common abnormality in children where there is abnormal flow of urine from the bladder into the upper urinary tract. The prevalence of VUR is about 1% and is identified in 30–50% of all children, boys and girls, presenting with a first urinary tract infection [60]. It results from an abnormal anti-reflux valve mechanism, usu-

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Fig. 17.40  Ectopic ureter in a 10-year-old male who presented with a palpable right-sided abdominal mass. (a) Longitudinal grayscale ultrasound image reveals an empty right renal fossa. A normal right kidney was not identified. L, Liver. Transverse (b) and longitudinal extended field of view (c) grayscale ultrasound images demonstrate a multicystic structure with an elongated inferior component extending along the right

flank into the pelvis. (d) Coronal contrast-enhanced, T1-weighted, fatsuppressed, magnetic resonance (MR) image shows a dysplastic, multicystic kidney (arrowhead) and markedly distended ureter (asterisk) extending into the pelvis where it ends blindly. (e) Intraoperative photograph shows the dilated ureter (U) terminating in an atretic segment that inserted into the vas deferens

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ally due to primary immaturity of the vesicoureteral junction or a short distal ureteric submucosal tunnel in the bladder. It can occur in isolation or in association with other congenital urinary tract abnormalities. The majority of VUR cases are primary, although it can develop secondary to bladder outlet obstruction, neurogenic bladder, or voiding dysfunction. Children with VUR are at increased risk of renal infection (pyelonephritis) and postinfectious renal scarring due to intra-renal reflux of infected urine; this risk is especially high in neonates and infants. Renal scars are of prognostic importance, as they are associated with the long-term development of hypertension and deterioration of renal function. Therefore, early detection of VUR is crucial to allow prompt prophylactic antibiotic treatment to decrease the risk of renal scarring [61].

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Grayscale ultrasound is useful in imaging of patients with VUR for evaluation of renal size, thickness, and appearance of the renal parenchyma, presence of collecting system and ureteral dilation, bladder wall thickness, and pre-void and post-void bladder volume in children who are toilet-trained (Fig.  17.41). Congenital malformations of the kidneys and bladder can also be identified [62]. In some patients with VUR, intermittent dilation of the collecting system and ureter is seen. Patients born with severe VUR, such as infant males with the so-called megacystis-megaureter syndrome, will have a large, thin-walled bladder, massive bilateral hydroureteronephrosis, and small dysplastic-­appearing kidneys [63]. In the majority of patients with VUR, however, the kidneys will appear normal. It is important to recognize that a normal ultrasound study does

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Fig. 17.41  Bilateral vesicoureteral reflux in a 2-month-old male with urosepsis. Longitudinal grayscale ultrasound images of the right (a) and left (b) kidneys demonstrate moderate-to-severe bilateral hydronephrosis and proximal hydroureter. Echogenic material representing purulent debris (arrowheads) is identified in both renal pelves. (c) Transverse

grayscale ultrasound image of the pelvis demonstrates dilated distal ureters (arrowheads). Echogenic debris in the distal ureters and bladder (B) is identified, as well as multiple short, linear echogenic foci thought to represent air from recent bladder catheterization. (d) VCUG image demonstrates bilateral severe vesicoureteral reflux

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not exclude the presence of VUR. Further evaluation of the urinary tract with a voiding cystourethrogram (VCUG) may be indicated in selected patients, regardless of the ultrasound findings.

tions, children with significant side effects from continuous prophylactic antibiotics, patient noncompliance with either antibiotic prophylaxis or failed follow-up after a febrile illness, and family preference.

Contrast-Enhanced Ultrasound Diagnosis of Vesicoureteral Reflux Contrast-enhanced voiding urosonography (CeVUS) is now widely accepted as an effective imaging technique for the investigation and management of vesicoureteral reflux (VUR).  In addition to its enhanced safety profile and the complete lack of ionizing radiation, CeVUS is more sensitive and detects higher grades of reflux compared with VCUG [64]. The bladder is catheterized, and a solution of ultrasound microbubbles in normal saline is infused under gravity while sequential imaging of the bladder and kidneys is performed during bladder filling and voiding (Fig. 17.42). Transperineal images of the urethra are obtained during voiding [65]. Static images, as well as cineclips, are used to document the examination. The diagnosis of VUR is based on detecting retrograde passage of the microbubbles to the ureter and/or renal pelvis from the urinary bladder. Intra-renal reflux appears as multiple punctate hyperechoic foci more commonly found in the polar regions of the kidney or as diffuse enhancement of the renal parenchyma [64, 66]. The severity of VUR can be graded using an I-V category scale comparable to the International Grading System used for conventional fluoroscopic VCUG [65]. In most children, VUR will ultimately resolve, and treatment is conservative, with prophylactic antibiotics and serial follow-up ultrasound studies and cystography. Patients with bladder and bowel dysfunction are identified and treated appropriately. Surgery is generally reserved for patients with Grade IV or V reflux that persists beyond 2 or 3 years of age, those who fail medical therapy with breakthrough infec-

Imaging of Endoscopically Placed Bulking Agents Endoscopic submucosal, subureteric injection of bulking agents is an accepted treatment method for VUR, first popularized in the 1980s as the STING (subureteric transurethral injection) procedure. The most commonly used injectable material is Deflux, a dextranomer-hyaluronic acid copolymer which is biodegradable, with volume stability and a relatively large particle size that prevents distant migration. Other previously used materials such as Teflon and silicone are no longer recommended due to the risk of distant migration and granuloma formation. The bulking agent is injected submucosally under cystoscopic guidance into the intravesical portion of the ureter in order to narrow the ureteric orifice, thereby preventing reflux. Familiarity with the characteristic imaging appearance of bulking agents will prevent misdiagnosis and unnecessary interventions [67]. On ultrasound, the bulking agent appears as a focal, round, or oval isoechoic or hyperechoic mound in the trigonal region of the posterior bladder wall that may protrude into the bladder lumen (Fig. 17.43). The mound may calcify and display posterior shadowing, occasionally simulating a distal ureteral stone [68].

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Anomalies of the Bladder Urachal Anomalies The urachus is the fibrous vestigial remnant of the allantois, a connection between the urinary bladder and the umbilical cord during fetal life. The urachus is located in the retropubic space and anterior to the peritoneum in the space of Retzius. Before

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Fig. 17.42  Vesicoureteral reflux in a 4-year-old male depicted by ceVUS. Transverse (a) and longitudinal (b) images from a ceVUS study show reflux (white arrowheads) into the distal right ureter. Shadowing from an intravesical catheter (black arrowhead) is noted. B, Bladder. (c)

Longitudinal ceVUS image of the right flank shows grade II–III reflux of contrast material into the renal collecting system and proximal ureter. (d) Image from VCUG performed 1 year earlier demonstrates a similar degree of right-sided reflux

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Fig. 17.43  Bilateral subureteric Deflux mounds used to treat reflux in a 3-year-old female. (a) Transverse grayscale ultrasound image of the bladder shows bilateral ovoid, echogenic subureteric mounds (aster-

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isks) in the trigonal region of the posterior bladder wall. (b) Longitudinal grayscale ultrasound image shows the left-sided mound protruding into the bladder lumen

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Fig. 17.44  Urachal remnant in a 5-year-old male. (a) Longitudinal and (b) transverse grayscale images demonstrate an ovoid, hypoechoic structure (arrows) in the anterosuperior wall of the urinary bladder

birth, the lumen of the urachus usually obliterates and forms the median umbilical ligament, a midline parietal peritoneal fold, extending from the apex of the bladder to the umbilicus. A normal urachal remnant is frequently seen as a small hypoechoic structure superior to the bladder on routine urinary tract ultrasound in children (Fig. 17.44) [69]. If the urachal lumen is not completely obliterated, a spectrum of urachal remnants may persist, including patent urachus, urachal sinus, vesicourachal diverticulum, umbilicourachal sinus, and urachal cyst (Fig. 17.45) [70]. Congenital urachal remnant abnormalities frequently coexist with congenital lower urinary tract obstruction

such as posterior urethral valves or prune-belly syndrome, and ventral abdominal wall defects such as omphalocele [55]. Surgical excision has historically been the standard approach to treating urachal anomalies owing to concern for infection and the rare chance of developing a urachal malignancy later in life. However, there is no evidence demonstrating that urachal anomalies in pediatric patients increase the likelihood of future urachal malignancy. In recent years, nonoperative management of symptomatic patients has gained increasing recognition as a reasonable alternative to surgical treatment [71, 72].

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Urachal sinus

Patent urachus

Anterior abdominal wall

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Fig. 17.45  Diagram of urachal anomalies

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Fig. 17.46  Patent urachus in a 2-day-old female with urine leakage from the umbilicus. (a) Longitudinal grayscale ultrasound image of the bladder (B) reveals a tubular structure (arrowheads) containing anechoic urine extending from the bladder dome toward the umbilicus (U). (b)

Transverse grayscale ultrasound image shows a large amount of fluid in the center of the umbilicus (asterisk). (c) Lateral image of the bladder (B) at VCUG shows contrast filling a patent urachus (arrowheads) and draining anteriorly through the umbilicus (U)

Patent Urachus A patent urachus is characterized by a persistent connection between the bladder and the umbilicus, presenting with urine leakage from the umbilicus. On ultrasound imaging, a patent urachus appears as a tubular structure extending between the anterosuperior aspect of the bladder and the umbilicus (Fig. 17.46) [73, 74].

Vesicourachal Diverticulum A vesicourachal diverticulum develops when the distal end of the urachus fails to close, resulting in an outpouching from the anterosuperior aspect of the bladder (Fig.  17.47). This anomaly is usually asymptomatic and identified incidentally as a urine-filled diverticulum extending from the bladder dome [73, 74].

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B U

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Fig. 17.47  Vesicourachal diverticulum in a 12-year-old male. Sagittal grayscale ultrasound image of the bladder (B) demonstrates a complex cystic structure (asterisk) at the bladder dome that extends superiorly and is in continuity (arrow) with the bladder lumen. U, Umbilicus

Umbilicourachal Sinus An umbilicourachal sinus results when the umbilical end of the urachus persists while the bladder end obliterates, resulting in a blind-ending umbilical tract. These lesions may be asymptomatic or can present with infection manifesting as abdominal pain and drainage of fluid. On ultrasound imaging, a thickened and fusiform dilation of the urachus at the umbilical end is identified, which does not communicate with the bladder [73, 74]. Urachal Cyst A urachal cyst occurs when there is obliteration of both the proximal and distal ends of the urachal lumen with persistence of a fluid-filled intervening portion. Urachal cysts are asymptomatic unless complicated by infection or bleeding. On ultrasound, a urachal cyst appears as a simple cystic structure in the midline of the anterior abdominal wall between the umbilicus and the bladder dome. An infected urachal cyst (Fig.  17.48) will demonstrate echogenic contents and a thickened wall [73, 74].

Bladder Diverticula Bladder diverticula may be congenital (primary) or acquired (secondary). Congenital bladder diverticula are noted incidentally in 2% of children, usually males [55]. They can be unilateral or bilateral and consist of herniated bladder mucosa through fibers of the detrusor muscle. They have also been described in children with connective tissue disorders such as Ehlers-Danlos syndrome [75]. Secondary bladder diverticula are usually related to bladder

Fig. 17.48  Infected urachal cyst in a 14-year-old female. Longitudinal grayscale ultrasound image demonstrates a heterogeneous fluid collection (arrows) superior to the dome of the bladder (B) with posterior acoustic enhancement (arrowheads). The bladder contains a moderate amount of echogenic debris (asterisk)

outlet obstruction, as with neurogenic bladder or posterior urethral valves. Diverticula are commonly identified at the ureterovesical junction where they are often associated with VUR because they alter the normal oblique insertion of the ureter into the bladder [76]. It is important to differentiate between bladder diverticula and bladder ears in male infants. As previously discussed, bladder ears are lateral outpouchings of the urinary bladder into the inguinal canals that resolve with age. Lateral imaging at VCUG usually helps to distinguish between these two conditions. On ultrasound, a bladder diverticulum appears as a round or oval anechoic fluid collection, often arising from the bladder base or adjacent to the ureteral orifice (Fig. 17.49). VCUG is the reference standard technique for identification of bladder diverticula. Surgical excision of a bladder diverticulum is only indicated if it is associated with infection, obstruction, or VUR. Recurrence after surgery is common [75].

Bladder Exstrophy Bladder exstrophy is a rare congenital malformation characterized by an infraumbilical abdominal wall defect, incomplete bladder closure with mucosal continuity with the anterior abdominal wall, epispadias, and associated abnormalities of the pelvic bones and musculature. This malformation is one part of the exstrophy-epispadias complex, with epispadias at the mild end of the spectrum and cloacal exstrophy at the severe end. Bladder exstrophy is the most common of these abnormalities and usually occurs in boys. Clinical findings of bladder exstrophy include bladder eversion, epispadias, wide diastasis of the pubic bones, and anterior displacement of the anus secondary to muscular deficiency. In males, the penis is short with wide separation of the corporal attachments and a dorsal curvature. In girls, there is a bifid clitoris. The ureters insert low in the bladder with a typical

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Fig. 17.49  Bladder diverticula in a 1-year-old female. (a) Transverse grayscale ultrasound image reveals two rounded fluid collections (asterisks) arising from the bladder (B). (b) The presence of diverticula (arrowheads) is confirmed on VCUG. B, Bladder

J-shaped course due to an enlarged recto-uterine pouch with inferolateral displacement of the ureters. All patients with bladder exstrophy will develop VUR after exstrophy closure, so ureteral reimplantation is performed at the time of repair [77]. Modern staged repair of bladder exstrophy is a three-step process in males and a two-step process in females. In stage I, the bladder and abdominal wall defects are closed in both sexes 2–3  days after birth, with epispadias repair only in females. Iliac osteotomies may be performed at this time if the pubic diastasis is greater than 4 cm or if the malleability of the pelvis is poor. In stage II, the male urethra is closed, usually between 6 and 12 months of age. In stage III, bladder neck reconstruction and bilateral ureteral reimplantation are performed in males and females when the child can take part in a voiding program, generally at 4–5 years of age [78]. After repair, ultrasound imaging will show a small bladder with irregular contours and a thickened wall (Fig. 17.50). The kidneys usually appear normal, although hydronephrosis may occur as a result of vesicoureteral reflux, bladder outlet obstruction, or urethral stricture. Renal scarring can develop from obstructive uropathy after bladder neck reconstruction or recurrent pyelonephritis. Bladder augmentation using a segment of bowel is often performed in children who cannot undergo bladder neck reconstruction because of a low bladder capacity, abnormal bladder compliance, or incontinence. Ileocystoplasty is the usual choice, although other bowel segments can be used. The augmented bladder segment with an undulating contour is identified by ultrasound above the native bladder. The characteristic “gut signature” of the augmented segment is usually evident (Fig.  17.51) [79]. Echogenic intraluminal mucus or debris is frequently noted.

Cloacal Exstrophy Cloacal exstrophy is the most severe manifestation of the exstrophy-epispadias complex where there is abnormal embryological development of the cloacal membrane. In contrast to bladder exstrophy where normal separation of the bladder and hindgut occurs, in cloacal exstrophy the urorectal septum fails to form. It is a multisystem anomaly that is often referred to as the OEIS complex (omphalocele-­exstrophy-imperforate anusspinal defects) and includes other malformations of the gastrointestinal, urogenital, and ­skeletal systems, and neurospinal axis. Males and females are equally affected. The classic presentation of cloacal exstrophy includes two exstrophied hemi-bladders separated by a segment of exstrophied cecum, and usually accompanied by a segment of prolapsed ileum. The hindgut is shortened and often blind-ending, with an imperforate anus. A split phallus is present with one half on either side of a widened pubic diastasis [80]. Immediately after birth and stabilization of the newborn, the exposed organs and mucosal surfaces are protected by moistening surfaces with saline and covering with sterile plastic wrapping or by enclosing the lower torso in a bowel bag. These measures help to prevent evaporative losses, trauma, and infection. Initial imaging of cloacal exstrophy includes ultrasound evaluation of the kidneys, since abnormalities of the upper urinary tract have been reported in 41–66% of patients, including hydronephrosis, pelvic kidney, horseshoe kidney, fusion anomalies, and unilateral renal agenesis [81]. The surgical management of cloacal exstrophy includes pelvic osteotomies and immobilization, bladder and abdominal wall closure, ureteral reimplantation, and usually augmentation cystoplasty with continent urinary diversion.

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Fig. 17.50  Repaired bladder exstrophy in a 12-week-old female. (a) Transverse grayscale ultrasound image of the bladder obtained soon after complete primary repair shows mural thickening and irregularity

B

Fig. 17.51  Ileocystoplasty in a 20-year-old male with bladder exstrophy. Longitudinal grayscale ultrasound image shows the bladder (B) with the augmented segment (asterisk) located superiorly. The augmented segment has an undulating contour with an inner hyperechoic mucosal layer (arrowhead) and an outer hypoechoic muscular layer (arrow)

Cloacal Malformation Cloacal malformations are characterized by a single perineal orifice and confluence of the distal portions of the urinary, genital, and gastrointestinal tracts. They represent the most

(arrowheads). (b) Image from a postoperative VCUG shows a small capacity bladder with a mildly lobulated contour. There is significant symphyseal diastasis (asterisks)

complex end of the spectrum of female anorectal malformations and are rare, occurring in only 1 of 50,000 live births. On physical examination, there is a single perineal orifice and no anal opening [82]. There is frequently failure of mullerian duct fusion with duplication of the uterus and proximal vagina, a persistent urogenital sinus and abnormal lower vagina and hymen. At birth, patients undergo immediate colostomy and creation of a mucous fistula to decompress the gastrointestinal tract. The role of imaging in patients with cloacal malformation is to establish the connections between the urethra, vagina(s), rectum, and common channel and to determine their relationship to the spine [83]. This information will help to determine the surgical approach to repair. When the cloaca is mainly located below the tip of the spine, a posterior sagittal approach can be used rather than a combined anterior and posterior sagittal approach. Ultrasound evaluation of the pelvis and kidneys is performed in the early management of patients with a cloacal malformation in order to determine whether significant hydrocolpos is present and if it is associated with hydronephrosis, which will determine the need for vaginal drainage (Fig.  17.52). Other imaging techniques, including fluoroscopy, three-dimensional (3D) CT, and MR imaging are currently used to further characterize the various anatomical abnormalities. Recently, contrast-enhanced genitosonography (ceGS) has been described as a potentially useful, nonionizing radiation technique similar to conventional genitography that provides superb anatomical detail of the opacified organs (Fig. 17.53) [84].

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Fig. 17.52  Cloacal malformation in a 4-day-old female. (a) Transverse grayscale ultrasound image of the pelvis reveals duplicated vaginas (V) massively dilated with fluid. (b) VCUG image shows a catheter (arrow)

V

in the bladder (B). Refluxed contrast material is present in each vagina (V) and in the rectum (R) that joins the cloaca between the 2 vaginas (arrowheads)

The long-term functional outcome of females with the cloacal malformation depends on the position of the anus and the length of the cloaca, with a shorter cloaca ( 3 years ≤ 24 months

Atypical/recurrent UTI All children

≤ 36 months < 2 years > 2 years < 2 years > 2 years

All children All children Not specified All children Pyelonephritis; atypical/recurrent UTI or risk factors for recurrent UTIc –

All children

VCUG Atypical/recurrent UTI Atypical/recurrent UTI AND specific featuresa Not indicated Abnormal US or other specific circumstances Abnormal US or risk factorsb Abnormal US; recurrent UTI Abnormal US Atypical/recurrent febrile UTI; abnormal US; family history of VUR VCUG or DMSA in bottom-up or top-down approach

DMSA Atypical/recurrent UTI Atypical/recurrent UTI Recurrent UTI – Abnormal US or VUR Only when diagnosis of UTI is in doubt Recurrent pyelonephritis, VUR III-IV VCUG or DMSA in bottom-up or top-down approach

NICE, National Institute for Health and Care Excellence; AAP, American Academy of Pediatrics; ISPN, Italian Society of Pediatric Nephrology; CPS, Canadian Paediatric Society; PSPN, Polish Society of Pediatric Nephrology; EAU, European Association of Urology; ESPU, European Society for Pediatric Urology US, Ultrasound; UTI, urinary tract infection; VCUG, voiding cystourethrography; DMSA, dimercaptosuccinic acid scintigraphy; VUR, vesicoureteral reflux a Dilation on ultrasound, poor urine flow, non-Escherichia coli infection, family history of VUR b First-degree relative with VUR, septicemia, chronic kidney disease, age  200 cm/sec at the stenotic site with evidence of post-stenotic turbulence causing spectral broadening; (2) a renal artery to aorta PSV ratio > 3.5; and (3) in severe RAS, a tardus-parvus waveform in the parenchymal arteries (acceleration index < 300 cm/sec2), with a prolonged acceleration time (> 0.07 seconds) [167]. Given the uncertainty regarding Doppler velocity criteria, it has been recommended that pediatric patients with hypertension and no clinical, laboratory or ultrasound evidence of vascular disease whose blood pressure is controlled on one or two drugs be monitored closely without further imaging. In children where the probability of renal vascular disease is very high, digital subtraction angiography should be performed regardless of the renal Doppler ultrasound findings [168].

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g Fig. 17.82  Renal artery stenosis secondary to fibromuscular dysplasia in a 14-year-old female with hypertension. Longitudinal grayscale ultrasound images of the right (a) and left (b) kidneys reveal a size discrepancy with the left diffusely smaller than the right. Longitudinal color Doppler ultrasound images with spectral analysis of (c) the left proximal main renal artery demonstrates a markedly elevated peak systolic velocity of 339 cm/sec. Peak systolic velocity in (d) an upper pole branch of the left main renal artery measures 138 cm/sec, a normal value. However,

the waveform is abnormal, with a delayed systolic upstroke (pulsus ­tardus). (e) There is a pulsus tardus and a low arterial resistive index (RI) in  a left upper pole artery indicative of significant upstream stenosis. (f)  Peak systolic velocity in the abdominal aorta is 131.9 cm/sec. (g) Angiographic image shows a “string of beads” appearance (arrow) of the left main renal artery in its mid-to-distal portion extending to the level of the trifurcation

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The arterial resistive index (RI) is elevated in RAS although it should be interpreted with caution based on the child’s age. The RI can be as high as 0.9 in preterm infants, 0.6–0.8 in neonates and infants, and only reaches adult values of 0.5–0.7 after the first year of life. An RI >0.85  in neonates and >0.7  in children are considered abnormal [168]. Asymptomatic cases are clinically observed. Management of symptomatic cases with renovascular hypertension includes antihypertensive therapy, percutaneous angioplasty of severe stenosis, and reconstructive surgery.

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ommended for monitoring of kidney function, early detection and management of hypertension and chronic kidney disease [173].

Renal Artery Pseudoaneurysm

Renal artery pseudoaneurysm is an uncommon vascular finding, with the majority occurring after an intervention such as percutaneous renal biopsy or percutaneous nephrostomy. Pseudoaneurysms can also complicate renal transplantation, blunt abdominal trauma, as well as renal inflammatory and neoplastic processes [174]. A pseudoaneurysm develops Renal Artery Thrombosis when the wall of the renal artery is injured with leakage of blood into the adjacent soft tissues. This collection is eventuRenal artery thrombosis is a rare condition in the pediatric pop- ally enclosed in a layer of fibrous tissue. Although usually ulation. In infants, it is nearly always associated with a history asymptomatic, these lesions can rupture, leading to lifeof umbilical artery catheterization. It can also occur in infants threatening hemorrhage [175]. of diabetic mothers, infants with dehydration or sepsis, or from A pseudoaneurysm appears as an anechoic cystic lesion an embolism through a patent ductus arteriosus [169]. In older on grayscale ultrasound. Doppler imaging plays a key role in children, renal artery thrombosis is usually related to trauma, diagnosis, showing a swirling pattern of blood flow within the vasculitis, and valvular heart disease. It presents clinically with pseudoaneurysm with a “yin-yang” pattern of to-and-fro flow abdominal pain and hematuria with leukocytosis and elevated (Fig. 17.84). Pulsed Doppler evaluation of flow at the neck of serum lactate dehydrogenase levels [170]. Segmental renal the pseudoaneurysm shows disordered bidirectional flow. artery infarction can result in hypertension with salt depletion Endovascular selective coil embolization is the mainstay (hyponatremia-hypertension syndrome) [171]. of treatment for pseudoaneurysms [176]. Main renal artery Grayscale ultrasound shows global or segmental wedge-­ pseudoaneurysms may require stent placement or surgical shaped, hypoechoic zones with an absence of blood flow ligation. on color and spectral Doppler (Fig.  17.83). This can be confirmed by CEUS as hypoperfusion or absence of enhancement in the infarcted regions compared to normal Renal Vein Thrombosis parenchymal enhancement [172]. Over time, hyperechoic scars will develop at the sites of infarction. Renal vein thrombosis (RVT) is the most common vascular Management of neonatal renal artery thrombosis requires abnormality of the newborn kidney, accounting for approxia multidisciplinary team that includes neonatologists, radiol- mately 10% of all venous thromboemboli in newborns. ogists, pediatric hematologists, and nephrologists. In addition Almost 80% of all cases of RVT present within the first to removal of the umbilical catheter and supportive therapy, month of life, most often in the first week. RVT is bilateral prophylactic heparin is administered in most cases to pre- in about 25% of cases [177]. The most common predisposvent thrombus extension. Thrombolytic therapy is reserved ing factors in newborns include dehydration, sepsis, birth for bilateral thrombosis compromising kidney function. asphyxia, maternal diabetes, polycythemia, and an indwellIn older children, treatment depends on the acuity of ing umbilical venous catheter. Prenatal cases have also been thrombosis and the underlying predisposing disorders. described, particularly in fetuses of diabetic mothers [178]. Thrombolytic therapy, surgical thrombectomy, and arteIn older children, RVT can be associated with trauma, rial bypass are therapeutic options. Long-term sequelae, neoplastic processes, or nephrotic syndrome. There are two such as kidney atrophy, systemic hypertension, and mechanisms of renal vein thrombosis. In the first, more comchronic kidney disease are common, and follow-up is rec- mon form in neonates, thrombosis is initiated at the level of

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Fig. 17.83  Renal artery thrombosis in a 14-year-old male with acute myocarditis and severe biventricular dysfunction. (a) Longitudinal grayscale ultrasound image shows a swollen left kidney with a blotchy appearance of the parenchyma and loss of normal corticomedullary differentiation. (b) Longitudinal color Doppler ultrasound image of the left renal hilum does not show a normal renal artery. Small hilar vessels (arrowheads) are noted.

V,  Main renal vein. Longitudinal color Doppler ultrasound images with spectral analysis reveal (c) low amplitude, low resistance arterial flow in the small hilar vessels, and (d) low amplitude, slightly dampened venous flow in the main renal vein. (e) Coronal contrast-enhanced CT image shows a linear thrombus (arrow) in the left main renal artery. The left renal parenchyma demonstrates a complete absence of enhancement (arrowhead)

the arcuate and interlobular veins, with proximal extension into the larger renal veins and ultimately into the IVC. In the second form, the thrombus arises initially in the IVC and extends in a retrograde fashion into the renal vein. This latter mechanism occurs in older children [179]. Clinically, the presence of a flank mass, gross hematuria, or thrombocytopenia raises the suspicion of RVT, especially in a neonate with risk factors. Adrenal hemorrhage is a recognized association with RVT, especially on the left side due to extension of thrombosis to the adrenal vein.

The ultrasound appearance of RVT varies depending on when the examination is performed relative to the onset and extent of thrombosis. Early grayscale ultrasound features include renal swelling, increased parenchymal echogenicity, and loss of corticomedullary differentiation. Small parenchymal venous thrombi initially appear as highly echogenic streaks that persist for several days. Renal vein and vena caval thrombi may appear as intraluminal echogenic foci. Since thrombi are initiated in small venules and subsequently propagate toward the hilum, early parenchymal

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Fig. 17.84  Pseudoaneurysm in a 17-year-old male with a history of a left lower pole kidney laceration. (a) Longitudinal grayscale ultrasound image of the left kidney shows an anechoic lower pole cystic structure (arrow). (b) Longitudinal color Doppler ultrasound image reveals a “yin-yang” pattern of blood flow (arrow) due to swirling of blood

within the pseudoaneurysm. There is prominent blood flow (arrowheads) within the adjacent lower pole vessels feeding and draining the pseudoaneurysm. (c) Longitudinal color Doppler ultrasound image with spectral analysis reveals disordered aneurysmal blood flow that appears both above and below the baseline

abnormalities are frequently present without visualization of a renal vein thrombus (Fig.  17.85). Kidney swelling progresses over the first week, the cortex becomes more echogenic, and the renal pyramids appear relatively more hypoechoic. Subsequently, the kidney becomes more heterogeneous in appearance due to focal areas of edema and hemorrhage [180]. Over the next 1–2 weeks, a ring of reduced echogenicity develops around the affected pyramids, and an echogenic band may develop at the extreme apex of the pyramid. These findings represent focal apical changes and fibrosis related to renal tubular damage [181]. The long-term sequelae of RVT depend on the extent of thrombosis and the formation of collateral veins. If there are sufficient collateral vessels to maintain renal perfusion, the affected kidney may recover completely. Otherwise, hemorrhagic infarction will result from venous congestion, which later heals by fibrosis, resulting in the formation of renal scars or diffuse renal atrophy [182].

Doppler ultrasound findings in RVT include absent or decreased renal venous flow, and high-resistance arterial flow with decreased, or reversed diastolic arterial flow. Even when low venous flow is demonstrated, as with non-occlusive thrombus or in the presence of renal vein collaterals, the venous flow appears relatively monotonous, with absence of the usual transmitted pulsations from the right atrium [182]. Since the left adrenal vein drains into the left renal vein, a renal vein thrombus can propagate directly into the left adrenal vein, which commonly manifests as adrenal hemorrhage.

Arteriovenous Fistula An arteriovenous fistula (AVF) is an abnormal direct communication between an artery and a vein without an intervening capillary network. The majority of cases are acquired lesions occurring after renal biopsy, nephrostomy, blunt or penetrating trauma, inflammation, malignancy, or

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AV

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Fig. 17.85  Renal vein thrombosis and adrenal hemorrhage in a 14-day-­old female. Longitudinal grayscale ultrasound images of the left flank reveal (a) a swollen, echogenic kidney with loss of normal corticomedullary differentiation and multiple linear, echogenic parenchymal streaks (arrowheads) representing venous thrombi. (b) There is a fluid collection in the left adrenal region (asterisk) displacing the left kidney inferiorly and containing echogenic, dependent debris (arrow)

consistent with blood products. (c) Longitudinal color Doppler ultrasound image of the left kidney shows flow in the main renal artery (A) and main renal vein (V). Longitudinal color Doppler ultrasound images with spectral analysis show (d) a normal waveform in the main renal vein. The arterial waveform in the main renal artery (e) is highly abnormal, with increased velocity and reversal of end-diastolic flow. This pattern is an indirect but characteristic sign of renal vein thrombosis

renal surgery. Small renal AVFs are asymptomatic. A large AVF can result in vascular steal and may present with flank pain, hematuria, hypertension, high output cardiac failure, renal insufficiency, massive hemorrhage, or thromboembolism. Clini­cally, a continuous abdominal bruit or palpable thrill may be present [183]. Grayscale ultrasound often reveals no abnormality or an AVF can appear as a cystic lesion. With color Doppler, an AVF may demonstrate soft tissue color artifact caused by tissue vibration (Fig. 17.86). Pulsed Doppler findings include high ­systolic velocity and high diastolic flow leading to a low-resistance waveform in the afferent artery; turbulent flow at the site of fistula; and arterialized flow in the efferent vein [183, 184]. Small, asymptomatic AVFs do not require treatment and may regress spontaneously. Symptomatic AVFs can be treated with angioembolization or surgical ligation [184].

Medical Renal Disease Medical renal disease may result in acute kidney injury or chronic kidney disease.

Acute Kidney Injury Acute kidney injury (AKI), previously referred to as acute renal failure, is a rapid deterioration of renal function, resulting in an inability to maintain fluid, electrolyte, and acid-­ base balance. It is clinically defined as a 50% or greater rise in serum creatinine or a 25% or greater fall in estimated glomerular filtration rate (eGFR) known or presumed to have occurred within the preceding 7 days. Causes of AKI can be classified into pre-renal, renal, and post-renal categories. Pre-renal causes are most common in

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a

b

c

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Fig. 17.86  Post-biopsy arteriovenous fistula (AVF) in a 15-year-old male with end-stage renal disease. (a) Longitudinal grayscale ultrasound image shows a small kidney with echogenic parenchyma and loss of normal corticomedullary differentiation. There is an ovoid anechoic focus (arrowhead) in the lower renal pole. A hypoechoic perirenal hematoma (asterisks) is present. (b) Longitudinal color Doppler ultrasound image of the left kidney reveals markedly increased blood flow at the lesion site (white arrowhead), as well as adjacent soft tissue color

artifact (black arrowheads) associated with tissue vibration. There is a subcapsular hematoma (white arrows) in addition to the perirenal hematoma (asterisk). (c) Longitudinal color Doppler ultrasound image obtained with a significantly increased velocity setting depicts the feeding and draining vessels (arrows) associated with the AVF (arrowhead). (d) Longitudinal color Doppler ultrasound image with spectral analysis of the AVF demonstrates high-amplitude, low-­resistance arterial flow above the baseline and arterialized venous flow below the baseline

children, especially in the neonatal period (about 70–80% of cases), including renal hypoperfusion due to severe dehydration, heart failure, and septic shock. Intrinsic renal causes such as acute glomerulonephritis, acute tubular necrosis, hemolytic-uremic syndrome, Henoch-Schönlein purpura,

nephrotic syndrome, and drug nephrotoxicity account for 10% of AKI cases and usually affect older children. Postrenal causes account for about 10% of cases and include urinary obstruction, especially from posterior urethral valves in early childhood [185].

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a L

Fig. 17.87 Acute kidney injury secondary to cardiogenic shock in an 18-day-old female. (a) Longitudinal grayscale ultrasound image of the right kidney shows increased parenchymal echogenicity compared to the

liver (L). Asterisk, Ascites. (b) Transverse color Doppler ultrasound image with spectral analysis reveals increased arterial pulsatility and an elevated RI of 0.84

Renal ultrasound is the imaging modality most often used in the evaluation of patients with AKI. The main role of ultrasound is to determine renal size and to exclude anatomical abnormalities as the cause of AKI [186]. Doppler techniques yield information regarding renal perfusion and vascular abnormalities (Fig. 17.87). Ultrasound is also used to guide percutaneous renal biopsy. Functional information can be obtained from nuclear medicine studies that can help differentiate between pre-renal, renal, and post-renal causes of AKI. Treatment of AKI depends on the underlying cause.

whereas the incidence of glomerulonephritis increases in children more than 12 years of age [188]. Imaging plays a crucial role in diagnosis, assessment of renal function, and monitoring of the results of treatment in children with CKD. As with AKI, ultrasound is the main imaging modality used to investigate CKD and to guide percutaneous biopsy. Assessment of renal and bladder morphology permits the diagnosis of congenital anomalies and determination of renal size. Monitoring of renal size is essential for long-term follow-up. Hypoplastic/dysplastic and scarred kidneys are usually small, whereas enlarged kidneys occur with obstruction, glomerulonephritis, and some cystic disorders. As CKD progresses, there is a gradual reduction in kidney size and loss of corticomedullary differentiation. Most patients will also have echogenic renal parenchyma. Treatment of CKD is supportive. Renal transplantation is the treatment of choice for children with end-stage renal disease, with improved patient survival and quality of life compared to dialysis.

Chronic Kidney Disease Chronic kidney disease (CKD) is a clinical syndrome characterized by a gradual loss of kidney function over time. The Kidney Disease: Improving Global Outcomes guidelines have defined CKD as abnormalities of kidney structure or function present for more than 3 months [187]. CKD can have a devastating impact on children, potentially leading to malnutrition, growth impairment, developmental delay, bone growth disorders, anemia, and hypertension. The most common causes of CKD in children are congenital abnormalities of the kidney and urinary tract, (e.g., renal hypoplasia, renal dysplasia, reflux nephropathy, and obstructive uropathy), steroid-resistant nephrotic syndrome, chronic glomerulonephritis, and renal ciliopathies. Other less common causes include polycystic kidney disease (both autosomal recessive and autosomal dominant), thrombotic microangiopathies (especially atypical hemolytic-­ uremic syndrome), nephrocalcinosis/nephrolithiasis, interstitial kidney disease, and infection. Structural causes of CKD (e.g., renal hypoplasia or posterior urethral valves) predominate in younger patients,

Renal Transplantation Renal transplantation is the treatment of choice for patients with end-stage renal disease who are maintained on peritoneal dialysis or hemodialysis. There are three types of allografts: mismatched cadaveric renal grafts, nonidentical living-related grafts, and human lymphocyte antigen–identical grafts with reported 1-year survival rates of 80%, 90%, and 95%, respectively [189]. Ultrasound and radionuclide imaging are the imaging modalities employed in renal transplantation assessment. Ultrasound is used in the postoperative period and for long-­term follow-up. It is also helpful in guiding diagnostic or therapeutic interventions,

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including biopsy drainage of fluid collections. Radionuclide imaging is performed to assess graft function.

Surgical Technique An understanding of the surgical techniques commonly used for renal transplantation is essential prior to imaging in order to anticipate and recognize complications, and to provide guidance regarding further imaging and intervention. Surgical techniques vary with patient age and by institution.

In younger children, the renal transplant is placed intraperitoneally. An end-to-side anastomosis is created between the donor renal artery and vein and the recipient distal aorta and IVC, respectively. In older children, the renal transplant is placed retroperitoneally in the iliac fossa with the external iliac artery and vein most commonly chosen for anastomosis (Fig.  17.88). An antirefluxing ureteral anastomosis to the urinary bladder is created. In complex cases, the native ureter of the recipient can be used as a conduit.

Diseased kidneys

Incision

Transplanted kidney

Bladder

Donor kidney Donor renal artery and vein attached to external iliac vessels External iliac artery and vein Donor ureter attached to bladder

Fig. 17.88  Diagram of retroperitoneal surgical technique used for renal transplantation in older children

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Fig. 17.89  Normal appearance of a renal allograft in a 12-year-old female. (a) Longitudinal grayscale ultrasound image of a renal allograft (cursors) in the right iliac fossa shows normal corticomedullary differentiation and echogenic renal sinus fat. (b) Longitudinal color Doppler

c

ultrasound image demonstrates normal intraparenchymal blood flow. (c) Color Doppler ultrasound image with spectral analysis of an interlobar renal artery shows a sharp systolic upstroke with antegrade flow throughout diastole

Normal Posttransplant Imaging On ultrasound, the normal renal transplant has a similar appearance to the normal native kidney (Fig.  17.89). The proximity of the transplant kidney to the anterior abdominal wall accentuates the contrast between the renal cortex, medulla, and renal sinus.

Complications Vascular Complications Children are at increased risk of early vascular thrombosis following transplantation compared with adults because of their small size and frequent discrepancies between the size of the donor and recipient vessels. Renal Artery Thrombosis Renal artery thrombosis with graft infarction is a rare complication of renal transplantation, occurring in only 3–4% of all pediatric renal transplants [190, 191]. It usually develops within the first 2 days after transplantation and is associated with en bloc transplants from young cadaveric donors that contain paired renal allografts, as well as the ureters, main renal arteries, and veins, and segments of the juxtarenal aorta and IVC. Most cases are related to arterial kinking or intimal dissection. Segmental infarction sometimes occurs in the early postoperative period in allografts with multiple renal arteries (Fig. 17.90), although these lesions more often develop as a late complication in association with acute or chronic rejection (Fig. 17.91). Clinical symptoms of infarction include tenderness and swelling over the graft and anuria. Optimization of Doppler imaging parameters for the detection of slow flow is mandatory to prevent misdiagnosis of arterial thrombosis when acute rejection is present, since severe rejection has

Fig. 17.90  Lower pole arterial thrombosis 1 day after renal transplantation in a 16-year-old female. Longitudinal color Doppler ultrasound image reveals a complete absence of blood flow (arrow) to the lower pole of the allograft

Fig. 17.91  Segmental infarction of renal allograft in a 12-year-old male 4  years after transplantation. Longitudinal grayscale ultrasound image reveals increased cortical echogenicity with poor corticomedullary differentiation. Focal wedge-shaped hypoechoic zone of cortical thinning (arrow) in the upper pole of the allograft represents an old infarct

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been reported to cause markedly diminished blood flow that mimics arterial thrombosis. Graft failure is the usual outcome of arterial thrombosis, although urgent thrombolytic therapy or thrombectomy can be attempted. Renal Artery Stenosis Renal artery stenosis is a late complication of renal transplantation, with a reported incidence of 4–18% [192, 193]. Clinical presentation includes new or progressive hypertension, marked hypertension refractory to medical therapy, hypertension associated with graft dysfunction in the absence of rejection, and hypertension associated with a systolic bruit audible over the graft. The incidence of transplant renal artery stenosis in children is difficult to determine as there is no consensus regarding what degree of arterial narrowing is clinically significant. The most widely accepted criterion is elevation of peak systolic velocity at the site of narrowing, although the literature conflicts regarding optimal cutoff values. In adults, peak systolic values greater than 250 or 300 cm/sec are highly sensitive and specific for the diagnosis of transplant renal artery stenosis [194, 195]. However, data regarding the usefulness of these criteria in children are minimal [196]. Color and spectral Doppler ultrasound evaluation reveals elevated velocities in the narrowed segment with spectral broadening of the arterial waveform. Occasionally, there is an associated downstream tardus-parvus waveform in the intrarenal arteries with associated low resistive indices. There may be color aliasing within the stenotic portion of the artery and perivascular soft tissue vibration artifacts caused by turbulent flow in the stenotic segment. The velocity measurements in the main renal artery, iliac artery, and the segmental renal arteries should be interpreted together. MR or CT angiography can be performed prior to conventional angiography, the current reference standard imaging test. These additional studies may detect a significant stenosis of the transplant main renal artery. There is frequently stable graft function in patients with a significant stenosis identified by imaging, and many patients will respond well to conservative treatment. When there are functional consequences of renal artery stenosis, percutaneous transluminal angioplasty with or without stent placement can be performed.

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Renal Vein Thrombosis Renal vein thrombosis (RVT) is a rare complication of renal transplantation that usually occurs in the first week of the postoperative period. Predisposing factors include shock or dehydration, venous compression from a peritransplant fluid collection, surgical technique, and decreased flow secondary to rejection. Left lower quadrant allografts are at higher risk of RVT due to compression of the left common iliac vein between the sacrum and the left common iliac artery (May-Thurner or “silent iliac compression” syndrome). Clinical suspicion for RVT is raised when a patient has abrupt cessation of urinary function, swelling, and tenderness over the allograft [197]. On grayscale ultrasound, the allograft may appear swollen and hypoechoic with echogenic material in the renal vein representing thrombus material. There will be absent or reduced flow in the renal vein with increased resistance in the renal artery resulting in reversed diastolic flow on pulsed Doppler imaging (Fig. 17.92) [198]. Prompt diagnosis of RVT is crucial because the renal transplant can sometimes be salvaged by urgent thrombectomy. Nevertheless, graft infarction may be inevitable even with early diagnosis, and transplant nephrectomy may be required. Arteriovenous Fistula An arteriovenous fistula (AVF) is the most common complication of graft biopsy and is almost never of clinical significance. Most AVFs are asymptomatic and more than 75% will spontaneously resolve. The ultrasound features of AVF in a renal homograft are the same as those described in the native kidney earlier in this chapter: possibly inapparent on grayscale imaging, but obvious with color and spectral Doppler evaluation (Fig. 17.93) [199]. Symptomatic fistulas leading to ischemia are treated with embolization. Pseudoaneurysm Pseudoaneurysm is another complication of renal allograft biopsy. It also tends to be asymptomatic and to resolve spontaneously. As previously described for the native kidney, a pseudoaneurysm is depicted as a cystic structure on grayscale ultrasound with a “yin-yang” pattern of to-and-fro flow on color and spectral Doppler imaging (Fig.  17.94). Progressive enlargement or a diameter greater than 2  cm are indications for embolic treatment [199].

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Fig. 17.92  Renal vein thrombosis 1 day after kidney transplantation in a 20-month-old male. (a) Longitudinal grayscale ultrasound image of the right lower quadrant renal allograft demonstrates diffuse swelling with echogenic parenchyma and decreased corticomedullary differentiation. Longitudinal color Doppler ultrasound images with spectral analysis reveal (b) diminished

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flow in the main renal vein with a dampened waveform and (c) markedly pulsatile flow in the main renal artery with reversal of end-­diastolic flow. (d) Axial contrast-enhanced CT image shows an extensive thrombus (arrow) in the main renal vein of the allograft. The allograft (asterisk) is nonperfused except for a thin rim of tissue at the periphery (arrowheads)

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Fig. 17.93  Post-biopsy AVFs of renal allograft in a 10-year-old female. (a) Longitudinal grayscale ultrasound image shows two hypoechoic lesions (arrowheads) in the lower pole of the allograft. A tubular anechoic

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structure (arrow) extending from the more proximal lesion represents a draining vein. (b) Longitudinal color Doppler ultrasound image demonstrates disordered blood flow within each lesion

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Fig. 17.94  Post-biopsy pseudoaneurysm of renal allograft in a 15-year-old male. (a) Longitudinal grayscale ultrasound image reveals an anechoic cystic structure (calipers) in the mid-kidney. (b) Longitudinal color Doppler

ultrasound image demonstrates a “yin-yang” pattern of swirling blood flow in the pseudoaneurysm. (c) Spectral analysis of the pseudoaneurysm depicts disordered blood flow

Parenchymal Complications Parenchymal complications of renal transplantation present as decreased renal function, and ultrasound evaluation is generally most helpful in ruling out causes of graft dysfunction such as a large vessel abnormality, urinary collecting system obstruction, or perinephric fluid collection. US-guided biopsy is usually needed to identify the specific cause of graft failure. Parenchymal complications include acute tubular necrosis, rejection, and drug toxicity and are discussed further below.

cally characterized by poor renal function and oliguria and is thought to result from prolonged ischemia and reperfusion injury. ATN affects cadaveric grafts more than grafts from living related donors (35% vs 10%) and usually resolves spontaneously over the first 2 weeks after transplantation [200]. Ultrasound findings of ATN include diffuse allograft enlargement, increased or decreased cortical echogenicity, loss of corticomedullary differentiation, prominent pyramids, urothelial thickening, and effacement of the central renal sinus echo complex. In severe cases, pulsed Doppler evaluation may show increased arterial resistive indices (>0.8) and reversed diastolic flow (Fig. 17.95) [189]. These findings are nonspecific and can also be seen with acute graft rejection and drug toxicity.

Acute Tubular Necrosis Acute tubular necrosis (ATN) occurs to some degree in most renal transplants immediately postoperatively. ATN is clini-

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Fig. 17.95  Acute tubular necrosis 3 days after renal transplantation in a 12-year-old male. (a) Longitudinal grayscale ultrasound image demonstrates diffuse swelling of the renal allograft with increased cortical

echogenicity and decreased corticomedullary differentiation. (b) Color Doppler ultrasound image with spectral analysis of an interlobar artery depicts abnormally pulsatile flow with an RI = 0.8

Rejection Rejection is the most common cause of allograft failure and can be classified into hyperacute, acute, and chronic types. Hyperacute rejection is characterized by ischemia and necrosis of the graft that occurs from the time of transplantation up to 48 hours after transplantation. It is believed to be caused by cytotoxic antibodies present in the recipient that respond to tissue antigens on the donor organ. Patients with hyperacute rejection are not usually imaged. Antibody-­ mediated rejection is frequently associated with graft loss. However, early and less severely affected kidneys can occasionally be salvaged by increasing the dosages of the immunosuppressant medication and administering antilymphocyte antibodies. In highly presensitized cases with high levels of circulating antibodies, plasmapheresis can be attempted if the patient is hemodynamically stable. Acute rejection is common, with up to 50% of patients experiencing at least one episode in the first year after transplantation. Clinically, the patient may present with oliguria, malaise, fever, weight gain, or tenderness over the allograft; or they may be asymptomatic, particularly if they are receiving cyclosporine [201]. There are two histological types of acute rejection: interstitial (or cellular), which is more common, and vascular (or humoral). In interstitial rejection, there is cellular infiltration of the renal interstitium with sparing of the arterioles and glomeruli so that diastolic flow and vascular impedance are not affected. Vascular rejection results from endovasculitis with subsequent vascular damage and thrombus formation resulting in increased vascular impedance. The clinical and ultrasound features of acute rejection are similar to those of ATN, with the two entities best differentiated by their differing time course. Acute rejection rarely occurs in the first few days after transplantation, usually

presenting as a progressive decrease in renal function within the first 3 months after transplantation. Pulsed Doppler findings depend on the subtype of acute rejection. In interstitial rejection, vascular impedance is not affected, and the arterial resistive index (RI) is normal (Fig.  17.96). In vascular rejection, there is increased vascular impedance with a high arterial RI (Fig. 17.97) [202]. Chronic rejection is the most common cause of late graft failure, occurring 3  months to years after transplantation. Patients will usually present with azotemia and hypertension. Renal function progressively declines and eventually fails. Renal biopsy is essential for the diagnosis and demonstrates proliferation of graft arteries and arterioles, interstitial cellular infiltration and fibrosis, tubular atrophy, and glomerular changes [201]. Ultrasound findings of chronic rejection include a small kidney; a thin, echogenic cortex; decreased corticomedullary differentiation; and mild hydronephrosis. Drug Toxicity Drug nephrotoxicity is another cause of decreased renal function and allograft failure. The calcineurin inhibitors cyclosporine and tacrolimus are the foundation of immunosuppressive therapy in pediatric renal transplantation. However, their nephrotoxic potential can result in graft injury. Clinical features are similar to those associated with ATN and rejection, including abdominal pain, fever, rising serum creatinine, and decreased urine output. Ultrasound features of drug nephrotoxicity are nonspecific, with graft enlargement, loss of corticomedullary differentiation, and decreased diastolic arterial blood flow with elevated resistive indices [203]. Treatment consists of a reduction in the dose of the immunosuppressive drugs [204].

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Fig. 17.96  Biopsy-proven acute interstitial rejection in a 7-year-old male with a renal allograft. (a) Longitudinal grayscale ultrasound image demonstrates a swollen kidney with preservation of normal

parenchymal echogenicity and corticomedullary differentiation. (b) Color Doppler ultrasound image with spectral analysis of an interlobar artery reveals normal arterial waveforms with an RI of 0.68

Fig. 17.97  Biopsy-proven acute vascular rejection in a 9-year old female with a renal allograft. (a) Longitudinal color Doppler ultrasound image of the right iliac fossa demonstrates poor corticomedullary differentiation of the allograft. There is only a small amount of

central blood flow with absent peripheral flow. (b) Color Doppler ultrasound image with spectral analysis of the main renal artery shows abnormal pulsatility with reversed end-diastolic flow

Urologic Complications Ureteroneocystostomy is the reconstructive technique currently used for restoration of urinary tract continuity in patients who undergo renal transplantation. This has led to a lower incidence of urologic complications (4–8%) compared to older procedures such as ureteroureterostomy or ­pyeloureterostomy (10–25%). About 60–70% of early urologic complications,

including urine leak and obstruction, occur in the first few weeks after transplantation [205, 206]. Transplant Urine Leak Urine leak is a rare complication of transplantation and is usually apparent in the first 2 weeks after surgery. Urine extravasation can occur anywhere from the renal calyces to

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Fig. 17.98  Urinoma in a 16-year-old male related to necrosis of the renal pelvis and ureter 2 weeks after kidney transplantation. (a, b) Longitudinal grayscale ultrasound images of the left iliac fossa show a multiloculated fluid collection (arrows) along the inferolateral aspect of

the renal allograft. There is moderate dilation of the renal collecting system (arrowheads). (c) Nephrostogram image shows contrast leakage (arrow) arising from the ureteropelvic junction and extending along the inferolateral aspect of the allograft (arrowheads)

the ureteroneocystostomy site. A urine leak can result in a localized perinephric urinoma or in urine ascites, depending on whether the graft is intra- or extraperitoneal in location. Urine leak can result from ureteral necrosis secondary to ischemia or increased pressure related to obstruction. Urine leak is clinically suspected when there is decreased urine output, swelling and tenderness around the graft, ipsilateral leg swelling, and scrotal or labial edema. On grayscale ultrasound, a urinoma can appear as an amorphous, anechoic fluid collection surrounding the graft or may have a more complex appearance. A urinoma can compress the ureter, leading to hydronephrosis (Fig.  17.98). Follow-up ultrasound studies are useful in documenting changes in collection size. Ultrasound-guided percutaneous aspiration can be performed when further characterization of the fluid is required. Technetium (Tc)-99m-­ mercaptoacetyltriglycine (MAG3) radio­nuclide studies are often used to distinguish a urinoma from a lymphocele or seroma since they are typically indistinguishable on imaging. Radiotracer excreted by the kidneys accumulates in a urinoma, but a lymphocele demonstrates persistent photopenia. Excretory MR urography is an alternative imaging technique that provides both functional and anatomic information without radiation exposure [203]. Close patient monitoring or stent placement can be used for small, non-obstructing collections. However, approximately half the patients with a urine leak will eventually require surgical intervention [207].

Patients usually present with deteriorating renal function. Diagnosis of renal obstruction is sometimes delayed by the absence of renal colic typically associated with obstruction because of denervation of the allograft during transplantation. The presence or absence of mild-to-moderate dilation of the urinary tract correlates poorly with the presence or absence of urinary tract obstruction in the posttransplant patient [209]. However, depiction of moderate-to-severe hydronephrosis and hydroureter that increases progressively over time warrants further evaluation to rule out obstruction. Tc-99m-MAG3 radionuclide studies or MRU can be performed, with the more invasive percutaneous antegrade urography used to localize the site of obstruction. A nephrostomy tube can be placed for purposes of urinary tract decompression and to permit stenting or balloon ureteroplasty [203].

Transplant Ureteral Obstruction Urinary obstruction complicates 2% of renal allografts, almost always within the first 6 months after transplantation. The most common site of obstruction is at the ureteroneocystostomy and is related to ischemia or rejection, technical anastomotic failure, or ureteral kinking. Other less common causes include intrinsic lesions causing intraluminal obstruction (e.g., calculi, papillary necrosis, fungus ball, and clot) or external compression from adjacent peritransplant fluid collections [208].

Transplant Vesicoureteral Reflux Vesicoureteral reflux (VUR) in the setting of pediatric renal transplantation occurs in approximately 12% of patients [210]. There is increased incidence of posttransplant VUR in children with a noncompliant bladder, detrusor overactivity, posterior urethral valves, or urethral stenosis [211]. However, the presence of VUR does not appear to be associated with either an increased frequency of posttransplant UTI or decreased long-term graft function [212, 213]. As previously discussed earlier in this chapter, the ultrasound features associated with VUR are usually nonspecific but can be associated with hydronephrosis and/or renal scarring (Fig. 17.99). Fluoroscopic and radionuclide voiding cystography are currently the standard imaging techniques for detection of VUR, although there will probably be an increasing role for ceVUS in the future. Low-grade VUR is managed with surveillance and long-­ term antibiotic prophylaxis, whereas high-grade reflux may require surgical reimplantation of the ureter. Revision of the ureterovesical anastomosis can be challenging due to scar tissue and vascular insufficiency of the transplant ureter that increase the risk of necrosis and anastomotic failure [210].

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Fig. 17.99 Vesicoureteral reflux into the renal allograft of a 10-year-­old female. (a) Longitudinal grayscale ultrasound image of the left-sided kidney transplant shows mild-to-moderate dilation of the collecting system

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(arrows). (b) Coronal radionuclide cystography image shows a moderate degree of reflux into the transplant ureter and renal collecting system. L, Left

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Fig. 17.100  Pyelonephritis of a renal allograft in a 17-year-old female. (a) Longitudinal grayscale ultrasound image of the renal allograft demonstrates diffuse parenchymal swelling with urothelial thickening (arrowheads). (b) Longitudinal grayscale ultrasound image of the allograft ureter

also shows diffuse urothelial thickening (arrowheads). Asterisk, Renal allograft. (c) Transverse grayscale ultrasound image of the bladder shows echogenic intraluminal debris (arrow) related to urinary tract infection

Transplant Pyelonephritis Infection is very common in renal transplant recipients, especially in the first year after surgery, and can manifest as pyelonephritis, parenchymal or perinephric abscess, pyonephrosis, or fungus ball. Pyelonephritis is associated with vesicoureteral reflux in pediatric renal transplant recipients. Renal infection can be an early or late complication. In the first few weeks after transplantation, the causative organisms are similar to those that typically develop in nonimmunocompromised patients after surgery. Opportunistic infections occur 1–6  months after transplantation, while infections common in the general population are seen after 6 months.

On ultrasound evaluation, the transplant kidney usually appears normal in the setting of pyelonephritis, but may occasionally demonstrate swelling and altered parenchymal echogenicity (Fig.  17.100). A parenchymal abscess is an unusual complication of graft pyelonephritis. Abscesses usually appear within the first postoperative month. Although the ultrasound appearance of an abscess is relatively nonspecific, prominent septations, internal debris, and mural hyperemia all suggest an infectious etiology. In the setting of pyelonephritis, the presence of mobile, hyperechoic foci within a dilated collecting system should raise concern for pyonephrosis [214]. Fungus balls appear as discrete intraluminal masses [215].

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Prompt diagnosis and treatment of infection are essential to prevent graft loss and improve outcome. Parenchymal abscesses can be treated with either ultrasound- or CT-guided percutaneous drainage and systemic antibiotics [215].

Perinephric Fluid Collections Transplant Lymphocele Lymphocele is the most frequently encountered perinephric collection that occurs in about 15% of patients 1–2  months after surgery. These collections develop due to surgical disruption of the lymphatic channels along the iliac vessels or of the hilar lymphatics of the transplanted kidney. Most lymphoceles are asymptomatic, incidentally discovered, and do not require therapy. However, they can potentially exert mass effect on the kidney causing obstruction or renal functional impairment. Lymphoceles can occasionally present with edema of the abdominal wall, scrotum, labia, or lower extremity [216]. On ultrasound imaging, a lymphocele appears as a unilocular or multilocular collection with internal septations located between the kidney and urinary bladder (Fig. 17.101). It can cause hydronephrosis if it exerts mass effect on the ureter. Percutaneous aspiration with drain placement is reserved for symptomatic patients. Recurrent collections can be treated with surgical marsupialization or transcatheter sclerotherapy [203]. Transplant Urinoma See earlier section on Transplant Urine Leak. Transplant Hematoma and Seroma A hematoma or seroma can develop immediately after transplantation and are expected sequelae of surgery [200]. The clinical significance of a hematoma depends on it size and location. A small hematoma is usually clinically insignificant, whereas a large hematoma can cause urinary obstruction from mass effect or a drop in hematocrit. A seroma is

Fig. 17.101  Lymphocele in an 8-year-old female with a renal allograft. Longitudinal grayscale ultrasound image shows two fluid collections (asterisks) adjacent to the renal allograft. The lower collection is separate from the bladder (not shown) and contains a small amount of echogenic, dependent debris (arrow)

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distinct from a hematoma as it contains almost no red blood cells. It is thought to develop as plasma from local bleeding accumulates at the site of recent tissue disruption from surgery or trauma. The ultrasound appearance of a hematoma depends on its age. In the immediate postoperative period, a hematoma will appear as an anechoic or hypoechoic collection. Once clotting has occurred, an acute hematoma will appear moderately echogenic, with homogeneous echotexture. As it matures, a hematoma demonstrates an increasingly heterogeneous internal structure, with peripheral organizing clot and thick internal septa superimposed on an anechoic serous component (Fig. 17.102). A hematoma can completely resolve over time or develop into a chronic seroma with imaging characteristics of simple fluid [202]. A seroma manifests as a simple fluid collection. It can develop nodular margins as it matures. Aspiration is not recommended for an asymptomatic collection because of its typically transient nature and the risk of introducing infection. Percutaneous image-guided aspiration of a perinephric hematoma or seroma can be performed if there is concern for superimposed infection. When a subcapsular hematoma causes impaired graft function, percutaneous drainage or surgical capsulotomy are treatment options. In the setting of active extravasation with hypotension, angiography with transcatheter embolization is the treatment of choice [203]. Transplant Abscess Perinephric abscesses usually develop within the first few weeks after transplantation. They usually result from bacterial seeding of a lymphocele, hematoma, or urinoma or, less commonly, are associated with pyelonephritis.

Fig. 17.102  Hematoma adjacent to the renal allograft of a 10-year-old male. Transverse grayscale ultrasound image reveals a heterogeneous collection (arrows) medial to the allograft (asterisk). Percutaneous aspiration of the collection revealed blood

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Fig. 17.103  Perinephric abscess of renal allograft in a 16-year-old male. (a) Longitudinal grayscale ultrasound image of the right iliac region shows an ill-defined collection (arrowheads) with both cystic and solid components inferior to the allograft (asterisk). V, External iliac vein. (b) Transverse color Doppler ultrasound image shows the ill-­defined collection (arrowheads) abutting the medial aspect of the allograft (asterisk) in

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the region of the renal sinus and encircling the iliac vessels. A, External iliac artery; V, external iliac vein. (c) Coronal contrast-enhanced CT image shows the minimally enhancing, irregular collection (arrowheads) abutting the renal sinus (asterisk). Purulent material was subsequently drained via a percutaneous approach

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Fig. 17.104  Posttransplant lymphoproliferative disorder (PTLD) in a 20-year-old female with a renal allograft. (a) Longitudinal grayscale ultrasound image of the right iliac fossa shows the lower pole of a renal allograft (asterisk) with an echogenic, solid mass (arrows) arising from

the wall of an adjacent bowel loop (B). (b) Coronal contrast-enhanced CT image shows the mass (arrows) arising from a loop of bowel (arrowheads) next to the renal allograft (asterisk)

Immunosuppression may obscure the symptoms of infection in these patients, although they may present with fever, pain or symptoms related to the pressure of the abscess on the transplanted kidney. Fever should be treated with a high index of suspicion in transplant patients and any perirenal fluid collection should be treated as infected in febrile transplant recipients until proven otherwise. On ultrasound, abscesses appear as hypoechoic complex fluid collections with debris and/or septations (Fig. 17.103). Highly reflective echoes with acoustic shadowing are caused by the presence of gas.

Abscesses are treated with either ultrasound- or CT-guided percutaneous drainage and systemic antibiotics.

Posttransplant Tumors Long-term immunosuppression predisposes renal transplant recipients to the development of tumors, both within the transplant kidney and in other organs. Posttransplant lymphoproliferative disorder (PTLD) and inflammatory myofibroblastic tumor have both been described. The imaging appearance of PTLD depends on the site of involvement (Fig. 17.104). When the transplant is affected,

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it usually appears as multiple ill-defined, hypoechoic parenchymal masses [206]. Inflammatory myofibroblastic tumor is a rare and usually benign neoplasm that is described later in this chapter in the Renal Tumors section.

Urinary Tract Calcification Renal Cortical Calcification Renal cortical calcification, also known as cortical nephrocalcinosis, results from pathological deposition of calcium in the renal cortex and is much less common than medullary nephrocalcinosis. The usual causes of cortical calcification are chronic glomerulonephritis and acute cortical necrosis. Less common causes include Alport syndrome, chronic hypercalcemic states, ethylene glycol poisoning, oxalosis, and sickle cell disease. Cortical calcification can also be seen in renal transplants in the setting of chronic rejection. On ultrasound, cortical calcification appears as a thin, echogenic rim outlining the cortex with a “tramline” appearance (Fig.  17.105). Less commonly, calcium deposition in necrotic glomeruli results in a spotty appearance [217]. There is no specific treatment for renal cortical necrosis.

Medullary Nephrocalcinosis Medullary nephrocalcinosis is the most common form of nephrocalcinosis and refers to the deposition of calcium salts in the medulla of the kidney. It is almost always bilateral, diffuse, and symmetric in distribution. The most common causes of medullary nephrocalcinosis are hyperparathyroidism and

Fig. 17.105  Renal cortical calcification in a 1-year-old male with a history of cortical necrosis. Longitudinal grayscale ultrasound image of the right kidney demonstrates a diffusely thinned, markedly echogenic cortex (arrowheads) in keeping with calcification

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distal renal tubular acidosis (type 1). Asymmetric medullary nephrocalcinosis can be seen in medullary sponge kidney as a result of calcium deposition within dilated collecting ducts. Medullary nephrocalcinosis tends to occur early in life and is frequently associated with inborn errors of metabolism, prematurity, and the use of certain medications, especially furosemide. Nephrocalcinosis is clinically asymptomatic and is usually identified incidentally during imaging performed for other reasons. On ultrasound, early nephrocalcinosis may be seen as a peripheral rim of increased medullary echogenicity with relative sparing of the central pyramid. A sequence has been described where this peripheral pattern progressively fills the pyramid leading to a diffuse increase in medullary echogenicity without distal shadowing (Fig. 17.106). High-­resolution, ­focused ultrasound reveals that the most peripheral portion of the pyramid is spared, appearing as a narrow hypoechoic rim [7]. Even with diffuse involvement of the medullary pyramids, renal function is often normal. A pattern of medullary nephrocalcinosis characterized by focal increased echogenicity at the tip of the renal pyramid is most commonly seen in preterm infants where small calculi develop in the calyces adjacent to the affected papillae. This finding has previously been attributed to furosemide therapy, although it is also seen in preterm infants who have never received furosemide, and therefore other factors are presumably involved [7]. Treatment is aimed at correcting the underlying cause of nephrocalcinosis. Prognosis depends on the underlying etiology, with the majority of the cases without an associated genetic defect resolving spontaneously in the first few years of life. Progression to end-stage renal failure is uncommon. Follow-up ultrasound imaging is recommended to document resolution or progression.

Fig. 17.106  Medullary nephrocalcinosis in a 3-year-old female with renal tubular acidosis type 1. Longitudinal grayscale ultrasound image of the right kidney reveals diffusely hyperechoic renal pyramids (arrows) due to calcium deposition

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Fig. 17.107  Dystrophic calcification in a 7-year-old male with prior upper pole nephrectomy for treatment of an ectopic ureter. Longitudinal (a) and transverse (b) grayscale ultrasound images of the right kidney

reveal a dense focus of calcification (arrows) in the upper pole nephrectomy bed with associated distal shadowing

Renal Vein Thrombosis Calcifications

Urolithiasis

Finely branching calcifications often develop within the renal cortex and medulla following renal vein thrombosis that represent microthrombi within the intrarenal veins (Fig. 17.85a) [182].

Urolithiasis refers to macroscopic calcifications that occur in the kidney, ureter, or bladder. Renal stones in children are uncommon, but their frequency has been increasing in recent years. Underlying causes include urinary tract infection, structural abnormalities of the renal tract, and metabolic disorders. Dietary, genetic, and climatic factors also influence the risk of developing renal stones. Approximately 40–60% of stones are predominantly composed of calcium oxalate, 10–20% are mainly calcium phosphate, 10–25% are mixed stones containing both calcium oxalate and calcium phosphate, 17–30% are magnesium ammonium phosphate (struvite or infection related), 6–10% are cystine, and 2–10% are uric acid [219]. Flank pain and hematuria are typical presenting symptoms [220]. Adequate hydration prior to imaging is important to maximally distend the portions of the urinary tract proximal to the obstruction and to optimize visualization of stones in the distal ureters and bladder [221]. Ultrasound is the initial imaging modality of choice, with noncontrast CT performed only when ultrasound is not diagnostic. By ultrasound, renal stones are identified as echogenic foci with or without posterior acoustic shadowing (Fig. 17.109). The color Doppler twinkling (or twinkle) artifact can be helpful in the diagnosis of small stones that are not associated with shadowing, hydronephrosis, or hydroureter (Fig. 17.110). This artifact appears as a discrete focus of alternating color Doppler

Dystrophic Calcification Dystrophic calcification of abnormal tissue can occur anywhere in the urinary tract, including the wall of a cyst, at sites of inflammation, or within a tumor (Fig. 17.107) [218].

Urinary Stasis Any form of urinary stasis predisposes to calcium deposition. The tubular ectasia that occurs in autosomal polycystic kidney disease and in medullary sponge kidney is frequently associated with deposits of calcium in the pyramids, at sites of dilated tubules. Similarly, milk of calcium, a viscous colloidal suspension of various calcium salts, may deposit in calyceal diverticula or in the renal pelvis in the setting of ureteropelvic junction obstruction. Staghorn calculi are occasionally seen in children with renal obstruction and infection. Stones can also develop in the setting of bladder diverticula, bladder outlet obstruction, and neurogenic bladder (Fig. 17.108) [218].

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Fig. 17.108  Staghorn calculus in an 18-year-old male with a neurogenic bladder. (a) Longitudinal grayscale ultrasound image of the left kidney demonstrates extensive echogenic foci within the renal collecting

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system with prominent distal shadowing (arrowheads). (b) Radiograph of the upper abdomen shows a large branching stone (arrow) in the left renal calyces and pelvis

Doppler can help in the diagnosis of obstructive stones at the UVJ by documenting the absence or decreased velocity of the ureteral jet (Fig. 17.111) [107].

Risk Factors Approximately 70% of children with urolithiasis have an underlying predisposing condition such as chronic infection, urinary stasis, or hypercalciuria [219].

Fig. 17.109  Renal stone in a 13-year-old female. Longitudinal grayscale ultrasound image demonstrates an echogenic focus (calipers) in the renal pelvis with posterior acoustic shadowing. There is associated mild renal collecting system dilation

signal immediately deep to the object that causes it, with or without an associated color comet-tail artifact [222, 223]. This sign has a high false-­positive rate when compared with 5-mm thick, unenhanced CT images [223]. The different types of urinary tract stone cannot be differentiated by ultrasound. A common pitfall in the ultrasound diagnosis of urinary tract calculi is mistaking air for a stone. Air in the collecting system usually results from recent catheterization or urinary diversion. Air can be differentiated from a stone by its “dirty” or poorly defined shadowing compared to the “clean” or sharply defined shadowing associated with stones. Color

Kidney Stone Risk Factors In children, idiopathic hypercalciuria is the most common underlying metabolic abnormality and is associated with the formation of calcium-containing stones. Primary oxlauria and secondary oxaluria increase the risk of developing calcium oxalate stones, as in patients with fat malabsorption related to cystic fibrosis and inflammatory bowel disease. Infection with urease-producing bacteria such as Proteus species predisposes to the formation of struvite stones, especially in boys less than 5 years of age with structural abnormalities of the urinary tract such as primary megaureter, bladder exstrophy, and neurogenic bladder. Uric acid stones commonly develop after treatment of myeloproliferative disorders or in the Lesch-Nyhan syndrome, a rare metabolic disorder affecting the uric acid pathway [217, 218]. Bladder Stone Risk Factors Urinary bladder stones usually occur in the setting of stasis. Risk factors include infection with urease splitting organisms (usually Proteus), an intravesical foreign body, neurogenic bladder, bladder augmentation or reconstruction, bladder diverticulum, and congenital bladder anomalies [217, 218].

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Fig. 17.110  Color Doppler twinking artifact with color comet-tail artifact in an 18-year-old female with a tiny renal stone. (a) Longitudinal grayscale ultrasound image of the left kidney shows a tiny echogenic focus (arrowhead) in the lower pole without associated distal shadowing or calyceal dilation. (b) Longitudinal color Doppler ultrasound image reveals a

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zone of alternating colors (arrowhead) at the site of the echogenic focus seen in (a) that is in continuity with a linear band of aliased color extending away from the ultrasound transducer. (c) Axial nonenhanced CT image confirms the presence of a small left lower pole renal stone (arrow)

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Fig. 17.111  Absence of ureteral jet in a 16-year-old female with a ureterovesical junction (UVJ) stone. Longitudinal (a) and transverse (b) grayscale ultrasound images of the bladder reveal a small stone (arrowheads) in a mildly dilated distal right ureter (arrows). (c) Transverse

color Doppler ultrasound image of the bladder demonstrates a normal left-sided ureteral jet (arrow). There is no right-sided ureteral jet. The right-sided UVJ stone (arrowhead) is associated with a prominent color Doppler twinkling artifact and color comet-tail artifact

Trauma

 ontrast-Enhanced Ultrasound Diagnosis of C Trauma Contrast-enhanced ultrasound (CEUS) diagnosis of visceral injury in the setting of abdominal trauma is of particular interest in children who are more vulnerable to the hazards of ionizing radiation than adults. CEUS is useful in stable pediatric patients with isolated blunt, low-to-­moderate energy abdominal trauma to rule out solid organ injuries; to further evaluate uncertain CT findings; and in the follow-up of conservatively managed traumatic injuries. CEUS can detect abnormalities that may not be apparent by conventional ultrasound, including infarcts, pseudoaneurysms, and active bleeding. Following the intravenous bolus administration of ultrasound contrast material, the renal cortex usually enhances immediately and very intensively, while the pyramids enhance from the periphery to the center in about 30 seconds. The optimal time frame for detection of renal injuries is up to about 2.5  minutes after contrast injection. Each kidney is assessed with a separate bolus [228]. The typical appearance of a renal laceration on CEUS is an absence of parenchymal perfusion compared to the adjacent normally perfused kidney (Fig. 17.112, Cineclip 17.1). Active hemorrhage can be detected as focal extravasation of

Renal Trauma Children are at increased risk for renal trauma due to several anatomic characteristics that expose the kidneys and make them more vulnerable to injury, such as larger kidney size relative to body size, positioning lower in the abdomen and therefore less protected by the rib cage, a smaller amount of perirenal fat, weaker abdominal wall musculature, and a weaker, less calcified thoracic rib cage. The renal capsule and Gerota’s fascia are less developed than in adults, creating a greater potential for parenchymal laceration and extravasation of urine [224]. In contrast to adults, hematuria is a very unreliable sign in determining the need to screen for renal injures in children [225]. Contrast-enhanced CT is the current modality of choice for initial imaging in clinically stable patients with suspected renal trauma. However, contrast-enhanced ultrasound has recently become an appealing alternative to contrast-enhanced CT in the evaluation of pediatric patients with blunt abdominal trauma, particularly with respect to the potential reduction of population-level exposure to ionizing radiation, as discussed below [226, 227].

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a

b

Fig. 17.112  Renal laceration and perirenal hematoma in a 15-year-old male. (a) Longitudinal grayscale ultrasound image reveals an illdefined zone of hypoechoic parenchyma (arrowheads) in the left midkidney with a surrounding anechoic fluid collection (asterisk). (b) Longitudinal CEUS image demonstrates a linear parenchymal defect

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(arrow) in the mid-­kidney that extends to the hilum (see Cineclip 17.1) in keeping with a grade IV American Association for the Surgery of Trauma (AAST) injury. Asterisk, Anechoic fluid collection. (c) Axial contrast-enhanced CT image confirms the presence of a deep renal laceration (arrowhead) and perirenal hematoma (asterisk)

b B L

Fig. 17.113  Bladder rupture in a 4-day-old female. (a) Transverse color Doppler ultrasound image of the abdomen reveals a large amount of ascites (asterisk) in the peritoneal cavity. L, Liver. (b) Longitudinal

CEUS image of the bladder (B) demonstrates a posterosuperior defect (calipers) of the bladder wall with extensive extravasation of contrast (arrowhead) into the peritoneal cavity. FC, Foley catheter

contrast material. However, since ultrasound contrast agents remain intravascular and are not filtered or excreted by the kidney, CEUS is unable to directly image traumatic lesions of the collecting system or ureter which can only be inferred by the presence of a fluid collection. The American Association for the Surgery of Trauma (AAST) divides traumatic renal injuries into five categories. Grade I–III injuries are managed conservatively, while grade V injuries generally require surgical exploration and repair. Management of patients with grade IV injury remains controversial although there has been a recent shift toward conservative management and the use of interventional radiological procedures as long as the patient remains clinically stable [229].

to extend into the abdomen where it is not afforded the same protection as when surrounded by the bony pelvis. Blunt trauma is the most common cause of urinary bladder injury in children [230]. Bladder injury can lead to extraperitoneal or intraperitoneal rupture, or a combination of the two [231]. In the setting of trauma, bladder injury should be suspected when there is anuria, inability to insert a urinary catheter, and free fluid in the abdomen. Conventional grayscale ultrasound is generally not helpful in the diagnosis of bladder injury, with fluoroscopic VCUG or CT cystography the traditional imaging modalities of choice. With the advent of contrast-enhanced voiding urosonography, there may be an expanded role in the future for ultrasound diagnosis of these injuries (Fig. 17.113). Extraperitoneal rupture occurs approximately 60% of the time as a result of pelvic fracture or penetrating trauma with extra-peritoneal extravasation of contrast material noted on imaging. Intraperitoneal rupture is identified by the presence of contrast material around bowel

Bladder Trauma Bladder injury occurs as a result of blunt, penetrating, or iatrogenic injury. The risk of bladder injury in children is greater than in adults due to the tendency of the full bladder

17  Urinary Tract

loops, between mesenteric folds and in the paracolic gutters [231]. Treatment of extra-peritoneal bladder rupture is usually conservative. Treatment of intraperitoneal bladder rupture usually requires surgical repair.

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the kidney is normal, imaging evaluation will be tailored to the relevant organ.

Benign Renal Tumors

Most abdominal masses in children arise from the kidney, with hydronephrosis and multicystic dysplastic kidney (MCDK) the most frequent diagnoses. Solid tumors are much less common. Initial imaging usually includes ultrasound and an abdominal radiograph. Ultrasound can usually determine the site of origin of the mass, whether it is cystic or solid, and assess its vascularity. If the mass arises from the kidney and is cystic, the differential diagnosis is between a hydronephrotic kidney and MCDK.  The appearance of the cysts by ultrasound and, if necessary, the presence of function on nuclear renography can usually distinguish between these two diagnoses. If the mass is solid and related to the kidney, a Wilms’ tumor is most likely. Tumor invasion of the renal vein or inferior vena cava and the presence of metastases are determined during the ultrasound examination. Tumor staging is usually done with CT or MR imaging. If the mass is related to another organ and

Mesoblastic Nephroma Mesoblastic nephroma is rare, accounting for only 3–6% of all pediatric renal tumors, but is the most common solid renal tumor in neonates and infants, generally presenting within 6 months of age [232]. It manifests clinically as a palpable flank mass or, occasionally, with hypertension. Although mesoblastic nephroma is usually considered a benign tumor, it can spread through local invasion. There are two main histologic subtypes of mesoblastic nephroma: classic and cellular, with 10–20% of tumors composed of a mixture of both patterns [233]. The cellular subtype is more common (about two-thirds of cases), more aggressive, tends to be larger, and occurs in older patients (>3 months of age). Chromosomal abnormalities are only identified in the cellular type [234]. On ultrasound, classic mesoblastic nephroma appears  as  a homogeneous, solid mass with concentric hyperechoic  and hypoechoic rims surrounding the tumor, the so-called “ring” sign [235]. This ring is vascular on color or spectral Doppler. Although involvement of the renal hilum is frequent (Fig. 17.114), there is no invasion of the renal vessels. Calcifications are uncommon. The cellular subtype appears heterogeneous and often contains fluid-filled spaces representing hemorrhage, necrosis, and cyst formation [236, 237].

Fig. 17.114  Mesoblastic nephroma in an 8-month-old male. (a) Lon­ gitudinal grayscale ultrasound image demonstrates a large, homogeneous, solid mass arising from the hilum of the left kidney (K).

(b) Longitudinal color Doppler ultrasound image shows minimal internal tumor vascularity with prominent flow in the adjacent compressed renal hilar vessels (arrowheads)

Tumors and Malformations Renal Tumors

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Fig. 17.115  Bilateral renal angiomyolipomas in a 12-year-old male with tuberous sclerosis. Longitudinal grayscale ultrasound images of the right (a) and left (b) kidneys reveal innumerable hyperechoic parenchymal nodules of varying size

Rarely, mesoblastic nephroma may appear predominantly cystic. These cystic tumors are larger than the classic subtype and frequently cross the midline due to a relatively aggressive growth pattern. In addition, they have the propensity to encase vessels and invade adjacent organs. Surgery is usually curative. Approximately 10% of mesoblastic nephromas will relapse, and the majority that relapse are cellular in type. Recurrences typically occur within 1 year of initial diagnosis [237]. Angiomyolipoma Angiomyolipoma is a benign solid tumor composed of varying proportions of mature adipose tissue, thick-walled blood vessels, and smooth muscle. Approximately 80% of angiomyolipomas are sporadic, with the remaining 20% occurring in association with tuberous sclerosis as discussed earlier in this chapter. Angiomyolipomas that occur in the setting of tuberous sclerosis are usually bilateral, multifocal, and larger in size than the sporadically occurring lesions [232, 238]. They are generally asymptomatic and discovered incidentally, although large tumors can present with flank pain, fullness, and hematuria. The vascular component of angiomyolipomas is elastin-­poor and can lead to the formation of aneurysms, which may bleed. The risk of retroperitoneal bleed-

ing depends on the size of the tumor. Masses exceeding 3.5  cm in diameter have a significantly higher risk of bleeding [239]. Angiomyolipomas can be classified as “fat-rich,” “fatpoor,” or “fat-invisible” based on their imaging appearance and fat content. On ultrasound, a “fat-rich” lesion appears as a highly echogenic (more echogenic than the renal sinus fat), non-shadowing focus (Fig.  17.115). “Fat-poor” and “fatinvisible” tumors can be missed on ultrasound since they may be isoechoic to the renal parenchyma. They can sometimes be indistinguishable from a Wilms’ tumor or renal cell carcinoma. If CT and MR imaging fail to reveal the correct diagnosis, image-guided percutaneous renal biopsy may be necessary despite the potential risk of bleeding [240]. Color and spectral Doppler can depict pseudoaneurysms with their characteristic “to-and-fro” flow. In patients with tuberous sclerosis, routine ultrasound surveillance is recommended for early detection of angiomyolipomas. Symptomatic masses and masses greater than 4  cm are treated. Treatment with mTOR inhibitors such as sirolimus or everolimus are recommended for tumors larger than 3 cm [241, 242]. Coil embolization is the treatment of choice for hemorrhagic tumors, and partial nephrectomy is an option when embolization fails.

17  Urinary Tract

Multilocular Cystic Renal Tumor Multilocular cystic renal tumor is an umbrella term that encompasses two histologically distinct but radiologically similar benign tumors arising from the metanephric ­blastema: cystic nephroma and cystic partially differentiated nephroblastoma (CPDN) [243]. These tumors have a bimodal age and sex distribution, being more common in young males (3  months to 4  years of age) and adult females (40–60 years of age) [244]. Tumors usually present as a painless abdominal mass, or occasionally with hematuria. The DICER1 gene encodes an enzyme that is important to RNA synthesis. Individuals with germline DICER1 mutations are at increased risk for developing multiple benign and malignant tumors. The typical renal manifestation of a DICER1 mutation is a pediatric cystic nephroma distinct from other lesions that can have a similar appearance, including adult cystic nephroma, cystic Wilms’ tumor, and CPDN [145]. Pediatric cystic nephromas, including those related to DICER1 mutations, occur equally in males and females, and almost all are diagnosed in the first 4 years of life. Increasing evidence indicates that most childhood cystic nephromas are probably related to DICER1 mutations. On ultrasound imaging, a pediatric renal cystic nephroma appears as a complex lesion that usually contains multiple thin septations and may abut or protrude into the renal hilum (Fig. 17.116). A small amount of blood flow can usually be demonstrated within the septa. Herniation of the tumor into the renal collecting system is a typical feature. Portions of the lesion may appear solid as many of the tiny cysts are below the resolution limits of ultrasound [234]. Calcifications may sometimes occur. These lesions may be smaller and less complex in younger children. On cross-­ sectional imaging, the septa typically enhance after contrast administration. Although a pediatric cystic nephroma is a benign lesion, it cannot be readily distinguished from other cystic renal neoplasms, including a cystic Wilms’ tumor. Surgical resection is the treatment of choice for multilocular cystic renal tumor, with nephron conserving surgery the preferred option when the diagnosis is suspected preoperatively [245]. Although surgical resection is generally curative, CPDN histology requires close imaging follow-up as it contains microscopic blastemal elements, and local recurrence is possible albeit

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Fig. 17.116  Multilocular cystic nephroma in a 2-year-old male. Trans­ verse grayscale ultrasound image shows a complex mass (cursors) containing cysts of different sizes separated by thin septations

rare [246]. Clinical examination and ultrasound are performed for follow-­up evaluation. Metanephric Adenoma Metanephric adenoma is a purely epithelial tumor derived from the metanephric blastema. It typically occurs in middle-­ aged females, although it also develops in children older than 14 months of age. It is frequently found incidentally, but can also present with a palpable mass, hematuria, and hypertension. In 12% of cases, metanephric adenoma is associated with polycythemia [247]. Although these tumors are considered benign, there have been a few cases where metastases have occurred [248]. On ultrasound, metanephric adenoma is typically welldefined and echogenic (Fig.  17.117) but can occasionally contain cysts and hypoechoic foci from prior hemorrhage or necrosis [249]. Calcifications are commonly seen. The tumor is hypovascular on Doppler evaluation [250]. Although considered a benign tumor, there is potential for malignant transformation. Treatment consists of nephron sparing surgery or partial nephrectomy [251].

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Fig. 17.117  Metanephric adenoma in a 14-year-old male. (a) Longi­ tudinal grayscale ultrasound image shows a well-circumscribed, echogenic and homogeneous mass (arrow) arising from the upper renal pole.

(b) Longitudinal color Doppler ultrasound image depicts minimal vascularity within the mass

Inflammatory Myofibroblastic Tumor Inflammatory myofibroblastic tumor, also known as inflammatory pseudotumor, is a rare lesion composed of myofibroblasts and inflammatory infiltrates. Although originally described in the lung, it has subsequently been described in multiple extrapulmonary sites. It can develop following solid organ and bone marrow transplantation. When it arises in the urogenital tract, it usually originates in the urinary bladder but can rarely occur in the kidney [252]. Although it may present at any age, it is unusual in children. Ultrasound findings of inflammatory myofibroblastic tumor are nonspecific and can mimic malignant tumors such as Wilms’ tumor and renal cell carcinoma (Fig. 17.118). Surgical excision is curative with no risk of local recurrence [253].

Although it is considered benign, all reported cases of ossifying renal tumor of infancy have been treated with partial or total nephrectomy. Given its rarity and unknown natural course, long-term follow-up is recommended [256].

Ossifying Renal Tumor of Infancy Ossifying renal tumor of infancy is an extremely rare benign tumor that arises from the papillary region of the renal pyramid. Histology reveals an osteoid core, osteoblast-like cells, and spindle cells. The tumor has a male predilection and typically occurs in infancy [254]. It can present with an abdominal mass and gross hematuria from extension into the renal pelvis. Ultrasound imaging demonstrates a heterogeneously echogenic intrarenal mass with posterior acoustic shadowing due to the osteoid component. Its appearance can closely mimic that of a staghorn calculus [232, 255]. Intra-tumoral blood flow can be seen with color Doppler.

Primary Malignant Renal Tumors Wilms’ Tumor Wilms’ tumor is the most common renal tumor in the pediatric age group, accounting for at least 90% of renal tumors in this population [257]. It arises from pluripotential mesodermal precursors of the renal parenchyma and occurs most often in children younger than 5  years of age, with a peak incidence at age 2–3 years [258]. Wilms’ tumor is usually solitary but can be multifocal and bilateral, and synchronous or metachronus. Although most cases occur sporadically, there is a known association between Wilms’ tumor and several disorders, including hemihypertrophy, Beckwith-­Wiedemann syndrome, and WAGR syndrome [259]. Children with Wilms’ tumor are usually asymptomatic and a palpable abdominal mass is identified by a parent or caregiver. Malaise, painless hematuria, and hypertension are other modes of presentation. The lung is the most common site of tumor metastasis followed by the liver. Bone metastases are rare [244]. At ultrasound, Wilms’ tumor appears as a heterogeneous mass of renal origin with distortion and compression of the surrounding renal parenchyma. Sharp margins formed by the normal renal parenchyma stretched around the mass give rise to the “claw” sign (Fig.  17.119). The mass may

17  Urinary Tract

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Fig. 17.118  Inflammatory myofibroblastic tumor in an 11-year-old female on chronic immunosuppression after renal transplantation. Longitudinal grayscale (a) and color Doppler (b) ultrasound images of the right-sided renal allograft demonstrate a lobulated, iso-to-­hypoechoic solid mass (M) in the renal sinus that displays minimal internal vascularity and peripherally displaces the sinus vessels (arrowheads). (c) Longitudinal color Doppler

ultrasound image of the right iliac fossa reveals extension of the mass into the ureter (U) with significant ureteral expansion and posterior displacement (arrow) of the adjacent iliac vessels. (d) Coronal contrast-enhanced CT image depicts extensive tumor involvement of the renal collecting system and ureter (arrows)

contain hypoechoic and anechoic areas representing hemorrhage, necrosis, and/or cysts (Cineclip 17.2). Shadowing echogenic calcifications can also occur. Color Doppler imaging is used to assess for tumor invasion of the ipsilateral renal vein and inferior vena cava, findings that affect

management (Fig.  17.120). Screening of the contralateral kidney is also imperative because of the possibility of synchronous or metachronous lesions (Fig. 17.121) [260]. Wilms’ tumor must be differentiated from neuroblastoma, a common tumor that occurs in a similar location and age

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M

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Fig. 17.119  Wilms’ tumor in a 9-year-old male. (a) Longitudinal grayscale ultrasound image reveals a large, heterogeneous mass (M) replacing most of the left kidney with a rim of normal parenchyma (asterisk) along its inferior margin, a “claw” sign. (b) Longitudinal color Doppler ultrasound image reveals displacement (arrowheads) of the normal renal hilar vessels around the mass. The mass appears rela-

tively avascular. (c) Longitudinal CEUS image reveals multiple enhancing tumor nodules (asterisks) with a large avascular zone (arrows). (d) Longitudinal contrast-enhanced CT image depicts nearcomplete replacement of the left kidney by tumor with residual normal parenchyma (arrow) along its inferoposterior margin

group. Features that suggest Wilms’ tumor rather than neuroblastoma include the “claw” sign described above, and venous tumor invasion compared to vascular encasement and displacement in neuroblastoma. Tumor that crosses the midline and extends through neural foramina into the spi-

nal canal, and skeletal metastases are all features commonly seen with neuroblastoma but not Wilms’ tumor [232, 234]. Calcification occurs in 15% of Wilms’ tumors compared to 80–90% of neuroblastomas [234].

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Fig. 17.120  Wilms’ tumor with invasion of the renal vein and IVC in a 3-year-old female. (a) Longitudinal grayscale ultrasound image demonstrates a large, echogenic mass (arrow) arising from the upper and mid-portions of the left kidney (LK). (b) Transverse grayscale ultrasound image shows extension of the mass (M) into the left renal vein

a

(V). (c) Transverse color Doppler ultrasound image reveals compression and distortion of the IVC (arrow) by tumor in the left renal vein (V). RK, Right kidney. (d) Axial contrast-enhanced CT image shows infiltration of tumor (arrowhead) into the anterior aspect of the IVC (C). M, Mass; V, left renal vein

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Fig. 17.121  Bilateral Wilms’ tumors in a 3-year-old female. (a) Transverse grayscale ultrasound image shows a large, mildly heterogeneous mass (arrow) arising from the right kidney (R). (b) Longitudinal grayscale ultra-

sound image reveals a similar solid mass (arrow) in the mid and lower portions of the left kidney (L). (c) Coronal contrast-enhanced CT image depicts bilateral heterogeneous, hypo-­enhancing renal masses (asterisks)

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The role of renal biopsy in Wilms’ tumor is controversial due to the risk of tumor seeding and unrepresentative sampling. In most centers, if the age of the child and the appearance of the mass are strongly suggestive of unilateral Wilms’ tumor, a biopsy is not performed. In North America, management usually follows the Children’s Oncology Group (COG) recommendations and includes initial total nephrectomy followed by chemotherapy, and in some cases radiotherapy. In Europe, children are treated according to the International Society of Paediatric Oncology (SIOP) protocol, with chemotherapy given prior to surgical nephrectomy in order to reduce the size of the tumor and the risk of intra-operative rupture. Bilateral tumors are treated with neoadjuvant chemotherapy followed by nephron-sparing surgery.

Nephrogenic rests can appear as rounded, ovoid, or poorly defined foci of variable echogenicity compared to the adjacent renal parenchyma (Fig.  17.122). Diffuse nephroblastomatosis manifests as renal enlargement, diffuse hyperechogenicity, and loss of corticomedullary differentiation. The typical appearance of a peripheral rind of abnormal tissue that displaces the normal renal parenchyma centrally is usually better evaluated by CT or MR imaging than with ultrasound [234]. Management of nephroblastomatosis in the absence of Wilms’ tumor is controversial. While some institutions prefer to give chemotherapy, others question its effectiveness and instead recommend close follow-up with serial ultrasound studies every 3 months up to the age of 8 years [244, 259]. A child with nephroblastomatosis should also be screened for associated syndromes.

Nephrogenic Rests and Nephroblastomatosis

Nephrogenic rests are foci of persistent metanephric blastema in the kidney after 36 weeks of gestation. When they are multiple or diffuse, they are referred to as nephroblastomatosis. They are considered precursors for Wilms’ tumor and account for 30–40% of unilateral and almost all bilateral Wilms’ tumors [251, 259]. In addition, they are associated with multiple genetic syndromes such as sporadic aniridia with or without WAGR syndrome, Beckwith-Wiedemann syndrome, hemihypertrophy, and Denys-Drash syndrome [244]. Nephrogenic rests may be perilobar or intralobar in distribution. Perilobar rests are seen at the periphery of the renal lobule, either in the columns of Bertin or in a subcapsular location. Intralobar rests are found within the renal lobule and may be located in the renal sinus, pelvocalyceal wall, or deep in the cortex. Both types of rest may be focal, multifocal, or diffuse. Patients with diffuse rests are usually less than 2 years of age and present with unilateral or bilateral flank masses. Focal and multifocal rests are usually asymptomatic and are incidentally discovered during a screening examination or at the time of imaging evaluation of Wilms’ tumor.

a

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Fig. 17.122  Diffuse nephroblastomatosis in a 22-month-old female. (a) Transverse grayscale ultrasound image of the right kidney reveals multiple nodular, hypoechoic, subcapsular masses (arrows). (b) Longitudinal grayscale ultrasound image of the left kidney reveals a similar appearance

Renal Cell Carcinoma Renal cell carcinoma (RCC) is the second most common pediatric renal malignancy after Wilms’ tumor, with an incidence of four cases per million children. However, it is more common than Wilms’ tumor in the second decade of life with a median age of 9  years at diagnosis [261]. The incidence of RCC increases with age with an equal gender distribution [262]. Pediatric RCC differs from adult RCC and is considered a separate entity. It is associated with von Hippel-Lindau disease, tuberous sclerosis, and Beckwith-Wiedemann syndrome. The most frequent histologic subtypes of RCC in the pediatric age group are translocation carcinoma, papillary carcinoma, and medullary carcinoma, with chromophobe and clear cell carcinoma being quite rare, whereas in adults, papillary, chromophobe and clear cell carcinoma are the most common subtypes [263]. In addition, spread of RCC to the regional lymph nodes is more common in children and is associated with a more favorable prognosis compared to adults [261].

c

and distribution of subcapsular masses (arrows). (c) Axial contrastenhanced CT image shows multiple bilateral hypo-enhancing renal masses surrounding and compressing the normally enhancing renal parenchyma (arrowheads)

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Clinical presentation includes macroscopic hematuria, flank pain, palpable abdominal mass, anemia, and fever. At ultrasound, RCC has a variable appearance. It may appear as a hypo-, iso-, or hyperechoic intrarenal mass with homogeneous or heterogeneous echotexture, depending on the presence of calcification, necrosis, and hemorrhage. It can be well-defined and surrounded by a pseudocapsule or unencapsulated and infiltrating (Fig.  17.123). Some tumor subtypes have a characteristic appearance: translocation RCC has “egg-shell” calcifications mimicking benign renal tumors [264]. RCC can invade retroperitoneal structures, the renal vein, and the inferior vena cava. It can metastasize to local or distant lymph nodes, lung, liver, and bones. It is not possible to differentiate between Wilms’ tumor and RCC by ultrasound, although the older age of the patient at presentation is a helpful guide to the correct diagnosis [232]. Radical nephrectomy is the treatment of choice for RCC in the pediatric population, with a possibility for nephronsparing surgery in small tumors [265]. This tumor is resistant to chemotherapy and radiotherapy. Therefore, adequate surgical resection and sampling of lymph nodes are critical. Prognosis depends on tumor staging with the survival rate ranging from >90% for stage I disease to 6–12 weeks 50–59

Rounded

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Covers the femoral head Covers the femoral head Covers the femoral head Covers the femoral head, β  80%) and splanchnic (50–70%) branches of the aorta. In most patients there is diffuse or segmental narrowing of the abdominal and/or distal descending

19  Vascular Imaging

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Fig. 19.37  Normal abdominal aorta in a 15-year-old female. (a) Sagittal grayscale ultrasound image depicts the echogenic walls of the aorta and the anechoic lumen. (b) Sagittal color Doppler ultrasound

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image with spectral analysis reveals a characteristic high-resistance triphasic waveform. (c) Spectral Doppler analysis of the celiac artery shows a normal biphasic, low-resistance waveform

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Fig. 19.38  Aortic thrombosis in an 8-day-old female with a right femoral arterial catheter. (a) Sagittal grayscale ultrasound image of the abdominal aorta reveals an intraluminal catheter (arrow). (b) Sagittal grayscale ultrasound image shows echogenic clot (arrowheads) on the

distal catheter tip. (c) Sagittal color Doppler ultrasound image shows nonocclusive thrombus (arrowheads) along the posterior aortic wall. (d) Spectral Doppler ultrasound evaluation of the aorta distal to the thrombus shows low-velocity, low-resistance waveforms

thoracic aorta, with varying involvement of the renal and visceral branches. Mid-aortic syndrome is an important cause of renovascular hypertension in children and adolescents. Most patients present with symptoms of severe hypertension, absent femoral pulses, an abdominal bruit, and lower leg claudication. Children with long-standing refractory hypertension may develop encephalopathy and retinopathy. Grayscale, color, and spectral Doppler ultrasound reveal narrowing of the abdominal aorta as well as variable narrowing of the major aortic branch vessels, especially the renal arteries (Fig.  19.39) [106]. Collateral vessels can also be identified. In the setting of Takayasu arteritis, arterial wall thickening can be present. Doppler spectral analysis shows elevated velocities at sites of stenosis with distal diminished flow velocities. Management of mid-aortic syndrome is aimed at controlling arterial blood pressure, preventing long-term complica-

tions related to hypertension, and preserving end-organ function (including the heart and kidneys). Treatment can be pharmacological, endovascular, or surgical [104].

Aneurysm Aortic aneurysms in infants are most often a complication umbilical arterial catheterization. The majority are mycotic in etiology and associated with bacteremia, especially Staphylococcus aureus and S. albus infection [107]. However, they can also be congenital and detected on prenatal ultrasound studies [108]. In older children, aortoiliac aneurysms are usually a manifestation of a connective tissue disorder such as Ehlers-Danlos syndrome or Marfan syndrome; inflammatory disorders such as Kawasaki disease and Takayasu arteritis; infection; or trauma [109]. In Marfan syndrome, there often is associated dilation of the aortic root. In Kawasaki disease, there may be multiple sites of aneu-

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Fig. 19.39  Aortic stenosis in a 5-year-old male with mid-aortic syndrome. (a) Sagittal grayscale ultrasound image of the abdominal aorta reveals marked narrowing (arrows) in its midportion. (b) Sagittal grayscale ultrasound image of the normal right kidney. (c) Sagittal grayscale ultrasound image of the small left kidney demonstrates loss of normal corticomedullary differentiation. (d) Sagittal color Doppler ultrasound image with spectral analysis shows a proximal aortic velocity of 145.6 cm/sec. (e) Sagittal color Doppler ultrasound image with spectral analysis of the narrowed por-

a

tion of the aorta shows an abnormally elevated velocity of 356.7 cm/sec. (f) Transverse color Doppler ultrasound image with spectral analysis of the left renal artery at its origin reveals an abnormal, high-resistance waveform due to stenosis. (g) Transverse color Doppler ultrasound image of the left main renal artery in the renal hilum shows an abnormal parvus-tardus waveform downstream from the stenotic arterial origin. (h) Sagittal contrast-enhanced maximum intensity projection (MIP) CT image shows the mid-abdominal aortic narrowing (arrowhead)

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Fig. 19.40  Mycotic abdominal aortic aneurysm in a 4-month-old former 29-week gestational age infant with clinical course complicated by methicillin-sensitive Staphylococcus aureus bacteremia. (a) Sagittal grayscale ultrasound image reveals a markedly dilated aorta (asterisk) with an irregular contour. (b) Transverse grayscale ultrasound image

demonstrates the widest portion of the aneurysm (asterisk) at the level of the left kidney (LK). (c) Sagittal color Doppler ultrasound image shows a swirling flow pattern within the aneurysm. (d) Sagittal MIP image from a contrast-enhanced CT shows superior displacement (arrow) of abdominal aortic branches by the aneurysm (asterisk)

rysm formation, including the coronary arteries; abdominal aorta; and iliac, femoral, and splanchnic arteries. When an aneurysm is suspected, ultrasound images and measurements of the abdominal aorta are obtained in transverse and longitudinal planes (Fig. 19.40). Grayscale ultrasound will show focal or diffuse aortic dilation. Mural thrombus may also be present. The Doppler ultrasound find-

ings will depend on the size of the aneurysmal neck, the amount of intraluminal thrombus, and the presence of calcification. The maximal aortic diameter is obtained perpendicular to the axis of the lumen of the aorta and measured from outer wall to outer wall. Longitudinal images are preferred for acquiring the most accurate measurements. Transverse imaging is important for identification of eccentrically located

19  Vascular Imaging

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Fig. 19.41  Dissection of the abdominal aorta in a 9-year-old male after motor vehicle collision. Sagittal (a) and transverse (b) grayscale ultrasound images show a subtle irregularity (arrowheads) of the inner

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aortic wall consistent with an intimal flap. (c) Coronal 3D reconstructed image from a contrast-­enhanced CT study confirms a dissection (arrowhead) of the infrarenal abdominal aorta

aneurysms. Normal age-related ultrasound measurements for the abdominal aorta in children can be consulted for reference purposes [110]. Treatment of aortic aneurysms in children varies according to the underlying cause [109]. Mycotic aneurysms are treated with antibiotics and surgical excision. With systemic inflammatory disorders, initial therapy is conservative and aimed at aneurysm prevention. Patients with Kawasaki disease receive anti-inflammatory medication in the acute phase, usually acetylsalicylic acid. If aneurysms subsequently develop, antithrombotic treatment is instituted to decrease the complication rate. Spontaneous aneurysmal rupture may occur that then requires surgical ligation or resection. Management of patients with Ehlers-Danlos syndrome is aimed at prevention of injury. Those with Marfan syndrome receive beta-blockers.

Dissection Abdominal aortic dissection is very unusual in children. It occurs most frequently in the setting of Marfan syndrome, where it is nearly always associated with thoracic aortic dissection. Ultrasound does not generally play a role in the diagnosis which is usually made by CT. Occasionally an intimal flap may be identified by ultrasound (Fig. 19.41, Cineclip 19.4), usually during a study performed for follow-up evaluation of an aneurysm.

Inferior Vena Cava  ormal Development and Anatomy N The IVC is the main channel through which venous blood from the lower extremities and abdominal viscera returns to the right atrium. Normal Development The IVC and the azygos-hemiazygos venous systems arise during the 4th to 8th weeks of gestation through a complex pattern of development, anastomosis, and regression that involves the vitelline vein and the paired posterior cardinal, supracardinal, and subcardinal veins.

Fig. 19.42  Diagram of embryologic segments leading to formation of the inferior vena cava. (© Catherine Delphia 2020)

Normal Anatomy The mature IVC has four segments: hepatic, suprarenal, renal, and infrarenal (Fig. 19.42) [111]. The vitelline vein contributes to the hepatic segment of the IVC. The suprarenal IVC is formed by a persistent portion of the right subcardinal vein. The renal segment of the IVC consists of the anastomosis between the right subcardinal and right

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Fig. 19.43  Diagram of embryological vessels leading to the development of the azygos and hemiazygos venous systems. The supracardinal veins (left panel) ultimately develop into the azygos and hemiazygos veins (right panel). (© Catherine Delphia 2020) Vertebral Internal jugular Superior vena cava Mediastinal Esophageal Internal thoracic Azygos Hepatic Renal Gonadal

External jugular Subclavian Brachiocephalic Axillary Cephalic Hemiazygos Intercostal Inferior vena cava Phrenic Adrenal

Lumbar

Common iliac Internal iliac External iliac

Fig. 19.44  Diagram of the major veins of the neck, chest, and abdomen

supracardinal veins. The infrarenal segment is derived from a p­ ersistent segment of the right supracardinal vein. The right posterior cardinal vein forms the distal-most IVC and its bifurcation into common iliac veins. The embryonic veins also lead to the development of the azygos, hemiazygos, and common iliac veins. The azygos

venous system arises from the supracardinal veins. The right supracardinal vein develops into the azygos vein, while the left supracardinal vein becomes the hemiazygos vein (Fig. 19.43). The IVC arises at the confluence of the common iliac veins at the level of the fifth lumbar vertebra (Fig. 19.44). It runs to the right of the aorta and anterior to the vertebral bod-

19  Vascular Imaging

ies. It extends through the diaphragm at the level of the eighth lumbar vertebra and after a short intrathoracic course drains into the right atrium. On ultrasound evaluation, the IVC has an anechoic lumen. Its wall is thinner and less echogenic wall than the aorta, and its size and contour vary with changes in respiration and intraabdominal pressure. With deep inspiration, there is a decrease in the diameter of the IVC, whereas the caliber of the IVC increases in expiration. The spectral Doppler waveform of the IVC varies according to location within the vessel. In the proximal IVC, a triphasic waveform is seen that reflects right atrial pulsatility and is similar to that within the hepatic veins. More distally, the waveform is less pulsatile and can be monophasic (Fig. 19.45) [3, 101]. In the setting of severe dehydration or hypovolemic shock, the IVC will appear collapsed with a relatively monophasic flow pattern. When right-sided heart pressures are elevated, the IVC will have an increased diameter, as in the setting of tricuspid insufficiency, right heart failure, or pericardial tamponade, and the spectral Doppler waveforms will appear exaggerated.

Congenital Anomalies Congenital anomalies of the IVC are the result of abnormal development of the embryological vitelline, posterior cardinal, subcardinal, and supracardinal veins. They occur in about 4% of the population and are most often asymptomatic [111, 112]. a

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Interruption of the IVC with Azygos Continuation Interruption of the IVC below the liver with azygos or hemiazygos continuation is due to a failure of anastomosis of the embryonic hepatic and prerenal portions of the IVC.  As a consequence, the suprarenal IVC drains either into the azygos vein and returns to the heart through the SVC or into the hemiazygos vein. The hepatic veins drain directly into the right atrium. This anomaly can occur as an isolated finding. However, it is frequently seen in patients with heterotaxy and complex congenital heart disease (i.e., the cardiosplenic syndromes) [113]. Although interruption of the IVC is much more common in the setting of polysplenia, it can also occur with asplenia [112]. Ultrasound features of interrupted IVC include absence of the intrahepatic portion of the IVC, drainage of the confluence of hepatic veins directly into the right atrium, and an enlarged right-sided azygos or left-sided hemiazygos vein. Unlike a normal IVC, an enlarged azygos vein will be located posterolateral to the aorta and dorsal to the right renal artery (Fig. 19.46). There is no specific treatment for this anomaly. However, it is important to not mistake an enlarged azygos or hemiazygos vein identified on ultrasound examination for retrocrural adenopathy [111]. Retrocaval Ureter Retrocaval ureter is a rare entity with a 3:1 male predominance. In the majority of cases, this anomaly is asymptomb

Fig. 19.45  Normal vena caval flow patterns. (a) Sagittal color Doppler ultrasound image with spectral analysis of the upper inferior vena cava (IVC) reveals a normal triphasic waveform. (b) Sagittal color Doppler ultrasound image of the mid-IVC demonstrates a less pulsatile waveform

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a

c

b S

K

L

H

V

Fig. 19.46  Azygos continuation of the IVC in a 2-year-old female with heterotaxy. (a) Transverse grayscale ultrasound image of the upper abdomen reveals a left-sided liver (L), a right-sided spleen (S) and stomach (asterisk). K, Right kidney. (b) Sagittal grayscale ultrasound

image shows the hepatic veins (V) draining directly into the heart (H). (c) Sagittal color Doppler ultrasound image shows a prominent azygos vein (arrowhead) posterior to the aorta (arrow). There is no intrahepatic IVC

atic. Symptomatic patients usually present with pain in the second to fourth decades of life. The infrarenal IVC usually develops from the embryological supracardinal vein. If instead it develops from the subcardinal vein, the ureter will pass posterior rather than anterior to the IVC. The aberrant course of the ureter is believed to result in obstruction. The ureter will then extend medially and anteriorly between the aorta and IVC to cross the right iliac vessels and enter the pelvis and bladder in the usual manner [114]. Two types of retrocaval ureter have been described. In the more common Type 1, the dilated ureter assumes a reversedJ or “fish hook” appearance. Ureteral obstruction develops at the edge of the iliopsoas at the site where the ureter turns cephalad before passing behind the IVC. In Type II, hydronephrosis is less severe, and the ureter passes horizontally behind the vena cava without an upward kink. Ureteral obstruction occurs at the lateral wall of the vena cava where the ureter is compressed behind the paravertebral muscles. Retrocaval ureter is best depicted by cross-sectional imaging such as magnetic resonance urography (MRU) or CT. MRU or diuretic renography can assess the degree of functional obstruction. Ultrasound imaging will show dilation of the right collecting system and proximal ureter. Occasionally, the compressed retrocaval ureter may be identified. Ultrasound is useful for follow-up of children with known retrocaval ureter to assess for evidence of complications. Treatment is needed only if there is significant obstruction, infection, urolithiasis, or increasing hydronephrosis. Surgery includes division of the retrocaval segment of ureter with excision of any stenotic segment and ureteropelvic or uretero-ureteric anastomosis anterior to the IVC.

infrarenal IVC segments. The left infrarenal IVC will join the left renal vein and drains into a normal suprarenal IVC. Identification of a duplicated IVC has implications for patient treatment in the setting of deep vein thrombosis and recurrent emboli if placement of an infrarenal IVC filter is contemplated. If this anomaly is not recognized, recurrent pulmonary embolism can subsequently develop with potentially fatal consequences [111]. On ultrasound imaging, a left-sided IVC will drain the left renal vein and then cross the midline to join the right-sided IVC.  A potential imaging pitfall is to mistake a left-sided IVC for an enlarged lymph node if the vessel is not followed along its course.

Duplicated IVC IVC duplication occurs when there is persistence of both the right and left supracardinal veins that form duplicated

Left-Sided IVC A left-sided IVC occurs when the right supracardinal vein regresses and there is abnormal persistence of the left supracardinal vein. As with a duplicated IVC, a left-sided IVC runs along the left side of the abdominal aorta, joins with the left renal vein, and empties into a normal right-sided suprarenal IVC (Fig. 19.47, Cineclip 19.5). Although a left-sided IVC is asymptomatic, if unrecognized it can lead to problems with central venous access during interventional procedures. A left-sided IVC may be confused with the abdominal aorta, limit access options for IVC filter placement, or complicate pulmonary thrombolysis procedures [111].

Thrombosis IVC thrombosis occurs in the setting of both non-neoplastic and neoplastic disorders. Non-neoplastic or “bland” thrombus is the main cause of IVC obstruction, with its attendant risk of pulmonary embolism. Risk factors for IVC thrombosis include venous stasis, focal compression, hypercoagulability, malignancy, and IVC filters. Bland thrombus in the IVC may occur in isolation, but usually develops as an extension of

19  Vascular Imaging

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a

b

A C

c

A C

Fig. 19.47  Left-sided IVC in an 8-year-old female. (a) Transverse grayscale ultrasound image shows the infrarenal IVC (C) located on the left side of the abdomen. A, Aorta. (b) Transverse grayscale ultrasound image at the level of the renal veins shows the crossing of the IVC

a

A

(arrowheads) from left to right, anterior to the aorta (A). (c) Transverse grayscale ultrasound image above the renal veins depicts the IVC (C) to the right of the midline. A, Aorta

c

b L

Fig. 19.48  Left lower extremity DVT extending from the popliteal vein to the low IVC in a 12-year-old female. (a) Sagittal power Doppler ultrasound image depicts extensive thrombosis (arrow) of the lower

IVC. (b) Sagittal color Doppler ultrasound image reveals that the upper IVC (arrow) is patent. L, Liver. (c) Sagittal power Doppler ultrasound image shows complete thrombosis (arrow) of the left external iliac vein

thrombosed pelvic or lower extremity deep vein thrombosis (Fig.  19.48). Unlike tumor thrombus, bland thrombus does not expand the caval lumen and demonstrates no enhancement after IV contrast administration [115]. Neoplastic invasion of the IVC in children most often occurs in the setting of Wilms’ tumor and is identified in approximately 4–8% of cases [116, 117]. Recognition of IVC tumor involvement is important as it may advance tumor staging, for example, from stage I to stage II, and necessitate an alteration in treatment approach. IVC extension of tumor is also associated with increased morbidity during nephrectomy. Other primary malignancies commonly associated with IVC invasion include renal cell carcinoma and hepatocellular carcinoma. Metastatic disease in the liver, kidneys, and adrenal glands can also involve the IVC via intravascular spread [111].

Both bland and malignant thrombi are echogenic and can partially or completely fill the caval lumen (Fig.  19.49). Bland thrombi are typically avascular on color and spectral Doppler imaging, while tumor thrombi may show internal vascularity as a result of neovascularization. When luminal occlusion is complete, flow will be absent in the IVC distal to the thrombus. With partial obstruction, there will be dampening of the spectral Doppler waveforms. Flow in collateral vessels can also be identified. IVC thrombi may completely resolve, leave a linear flap, or calcify. A calcified thrombus will be depicted as an echogenic, elongated intraluminal mass that may demonstrate posterior acoustic shadowing. Anticoagulation is the mainstay of therapy for bland IVC thrombosis. Vena caval filters can be placed if anticoagulation therapy is contraindicated [115, 118]. The presence of

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a

b

LK

c

RK

Fig. 19.49  IVC invasion in a 20-month-old male with Wilms’ tumor. (a) Longitudinal grayscale ultrasound image reveals a large mass (arrow) replacing most of the left kidney (LK). (b) Coronal color Doppler ultrasound image of the right kidney (RK) shows a patent right

renal vein (arrowhead) with expansile, echogenic tumor (asterisk) in the IVC. (c) Coronal contrast-enhanced CT image shows the large left renal mass (asterisk) and left renal vein tumor extending into (arrowhead) and distorting the IVC

tumor thrombosis significantly worsens prognosis and will have a significant impact on the approach to treatment which will vary according to tumor type [119].

able IVC filter can also be considered for patients with a history of pulmonary embolism [121, 122].

May-Thurner Syndrome Patients with May-Thurner syndrome, or iliac vein compression syndrome, are predisposed to iliofemoral thrombosis as a result of an anatomic variant where the right common iliac artery overlies and compresses the left common iliac vein against the lumbar spine [120]. The chronic compression leads to impaired venous return, and endothelial injury can lead to thrombosis with the potential for extensive DVT of the ipsilateral extremity. Patients who develop a left-sided DVT in the context of May-Thurner syndrome are typically young adults who will develop sudden swelling of the left lower extremity after surgery, during immobilization, or during pregnancy and the post-partum period. Adolescents can also be affected. Although ultrasound is used to confirm the presence of acute DVT, it is not generally able to image the underlying venous stenosis and compression of the iliac vessels due to their deep location within the pelvis. Contrast venography is the reference standard imaging diagnostic procedure but is rarely performed. More often, the diagnosis is made by CT or MR imaging [120]. Patients generally respond poorly to anticoagulation therapy alone. Catheter-delivered thrombolytics and percutaneous mechanical thrombectomy, either with or without angioplasty and stent placement, are the standard of care for symptomatic patients with May-Thurner syndrome. Postoperative treatment includes anticoagulation for at least 3 months to prevent re-thrombosis. A retriev-

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938 54. Moneta GL, Yeager RA, Antonovic R, Hall LD, Caster JD, Cummings CA, et  al. Accuracy of lower extremity arterial duplex mapping. J Vasc Surg. 1992;15(2):275–8. 55. Hatsukami TS, Primozich JF, Zierler RE, Harley JD, Strandness DE Jr. Color Doppler imaging of infrainguinal arterial occlusive disease. J Vasc Surg. 1992;16(4):527–31. 56. Mustapha JA, Saab F, Diaz-Sandoval L, Karenko B, McGoff T, Heaney C, et  al. Comparison between angiographic and arterial duplex ultrasound assessment of tibial arteries in patients with peripheral arterial disease: on behalf of the Joint Endovascular and Non-Invasive Assessment of LImb Perfusion (JENALI) Group. J Invasive Cardiol. 2013;25(11):606–11. 57. Lim S, Javorski MJ, Halandras PM, Kuo PC, Aulivola B, Crisostomo P. Epidemiology, treatment, and outcomes of acute limb ischemia in the pediatric population. J Vasc Surg. 2018;68(1):182–8. 58. Sadat U, Hayes PD, Varty K. Acute limb ischemia in pediatric population secondary to peripheral vascular cannulation: literature review and recommendations. Vasc Endovasc Surg. 2015;49(5–6):​1427. 59. Davis FM, Eliason JL, Ganesh SK, Blatt NB, Stanley JC, Coleman DM. Pediatric nonaortic arterial aneurysms. J Vasc Surg. 2016;63(2):​ 466–76. e1 60. Sivaharan A, Elsaid T, Stansby G. Acute leg ischaemia in a child due to a thrombosed popliteal aneurysm. EJVES Short Rep. 2018;42:1–3. 61. Wilson WR, Bower TC, Creager MA, Amin-Hanjani S, O’Gara PT, Lockhart PB, et  al. Vascular graft infections, mycotic aneurysms, and endovascular infections: a scientific statement from the American Heart Association. Circulation. 2016;134(20):e412–60. 62. Sörelius K, Mani K, Björck M, Nyman R, Wanhainen A. Endovascular repair of mycotic aortic aneurysms. J Vasc Surg. 2009;50(2):269–74. 63. Mansour MA, Gorsuch JM. Diagnosis and management of pseudoaneurysms. Perspect Vasc Surg Endovasc Ther. 2007;19(1):58–64. 64. Hall HA, Minc S, Babrowski T. Peripheral artery aneurysm. Surg Clin North Am. 2013;93(4):911–23. 65. Ford EG, Stanley P, Tolo V, Woolley MM.  Peripheral congenital arteriovenous fistulae: observe, operate, or obturate? J Pediatr Surg. 1992;27(6):714–9. 66. Li JC, Cai S, Jiang YX, Dai Q, Zhang JX, Wang YQ. Diagnostic criteria for locating acquired arteriovenous fistulas with color Doppler sonography. J Clin Ultrasound. 2002;30(6):336–42. 67. González SB, Busquets JC, Figueiras RG, Martin CV, Pose CS, de Alegria AM, Mourenza JA.  Imaging arteriovenous fistulas. AJR Am J Roentgenol. 2009;193(5):1425–33. 68. Gooding GA, Hightower DR, Moore EH, Dillon WP, Lipton MJ.  Obstruction of the superior vena cava or subclavian veins: sonographic diagnosis. Radiology. 1986;159(3):663–5. 69. Needleman L, Cronan JJ, Lilly MP, Merli GJ, Adhikari S, Hertzberg BS, et al. Ultrasound for lower extremity deep venous thrombosis: multidisciplinary recommendation from the Society of Radiologists in Ultrasound consensus conference. Circulation. 2018;137(14): 1505–15. 70. Bundens WP, Bergan JJ, Halasz NA, Murray J, Drehobl M. The superficial femoral vein. A potentially lethal misnomer. JAMA. 1995;274(16):1296–8. 71. Lin EP, Bhatt S, Rubens D, Dogra VS. The importance of monophasic Doppler waveforms in the common femoral vein: a retrospective study. J Ultrasound Med. 2007;26(7):885–91. 72. Lockhart ME, Sheldon HI, Robbin ML.  Augmentation in lower extremity sonography for the detection of deep venous thrombosis. AJR Am J Roentgenol. 2005;184(2):419–22. 73. Noren A, Ottosson E, Sjunnesson M, Rosfors S. A detailed analysis of equivocal duplex findings in patients with suspected deep venous thrombosis. J Ultrasound Med. 2002;21(12):1375–83. 74. Miller N, Obrand D, Tousignant L, Gascon I, Rossignol M. Venous duplex scanning for unilateral symptoms: when do we need a contralateral evaluation? Eur J Vasc Endovasc Surg. 1998;15(1):18–23. 75. Naidich JB, Torre JR, Pellerito JS, Smalberg IS, Kase DJ, Crystal KS. Suspected deep venous thrombosis: is US of both legs necessary? [ comment]. Radiology. 1996;200(2):429–31.

H. J. Paltiel 76. Stevens SM, Elliott CG, Chan KJ, Egger MJ, Ahmed KM. Withholding anticoagulation after a negative result on duplex ultrasonography for suspected symptomatic deep venous thrombosis. Ann Intern Med. 2004;140(12):985–91. 77. Weber TM, Lockhart ME, Robbin ML. Upper extremity venous Doppler ultrasound. Radiol Clin North Am. 2007;45(3):513–24. 78. Goldfisher R. Lower-extremity venous ultrasound – past, present and future. Pediatr Radiol. 2017;47(9):1209–13. 79. Hamper UM, DeJong MR, Scoutt LM. Ultrasound evaluation of the lower extremity veins. Radiol Clin North Am. 2007;45(3):525–47. 80. Lee BB. Venous embryology: the key to understanding anomalous venous conditions. Phlebolymphology. 2012;19(4):170–81. 81. Casella IB, Presti C, Yamazaki Y, Vassoler AA, Furuya LA, Sabbag CD. A duplex scan-based morphologic study of the femoral vein: incidence and patterns of duplication. Vasc Med. 2010;15(3):​197–203. 82. Sadowska A, Spodnik JH, Wójcik S. Variations in popliteal fossa venous anatomy: implications for diagnosis of deep-vein thrombosis. Folia Morphol (Warsz). 2013;72(1):51–6. 83. Quinlan DJ, Alikhan R, Gishen P, Sidhu PS. Variations in lower limb venous anatomy: implications for US diagnosis of deep vein thrombosis. Radiology. 2003;228(2):443–8. 84. Screaton NJ, Gillard JH, Berman LH, Kemp PM. Duplicated superficial femoral veins: a source of error in the sonographic investigation of deep vein thrombosis. Radiology. 1998;206(2):397–401. 85. Park ES, Choi HS, Lee KS, Kim SW, Lee JM.  Venous thromboembolism in children and young adults in Korea: analysis of the Korean Health Insurance Review and Assessment Service Database. J Korean Med Sci. 2019;34(49):e316. 86. Heit JA. Epidemiology of venous thromboembolism. Nat Rev Cardiol. 2015;12(8):464–74. 87. Sandoval JA, Sheehan MP, Stonerock CE, Shafique S, Rescorla FJ, Dalsing MC.  Incidence, risk factors, and treatment patterns for deep venous thrombosis in hospitalized children: an increasing population at risk. J Vasc Surg. 2008;47(4):837–43. 88. Bates SM, Jaeschke R, Stevens SM, Goodacre S, Wells PS, Stevenson MD, et  al. Diagnosis of DVT: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e351S–418S. 89. Ageno W, Squizzato A, Wells PS, Büller HR, Johnson G. The diagnosis of symptomatic recurrent pulmonary embolism and deep vein thrombosis: guidance from the SSC of the ISTH.  J Thromb Haemost. 2013;11(8):1597–602. 90. Wilbur J, Shian B. Diagnosis of deep venous thrombosis and pulmonary embolism. Am Fam Physician. 2012;86(10):913–9. 91. Wells PS. Integrated strategies for the diagnosis of venous thromboembolism. J Thromb Haemost. 2007;5(Suppl 1):41–50. 92. Le Gal G, Carrier M, Rodger M. Clinical decision rules in venous thromboembolism. Best Pract Res Clin Haematol. 2012;25(3):303–17. 93. Qaseem A, Snow V, Barry P, Hornbake ER, Rodnick JE, Tobolic T, et al. Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Fam Med. 2007;5(1):57–62. 94. Segal JB, Eng J, Tamariz LJ, Bass EB. Review of the evidence on diagnosis of deep venous thrombosis and pulmonary embolism. Ann Fam Med. 2007;5(1):63–73. 95. Wells PS, Anderson DR, Rodger M, Forgie M, Kearon C, Dreyer J, et al. Evaluation of D-dimer in the diagnosis of suspected deep-­ vein thrombosis. N Engl J Med. 2003;349(13):1227–35. 96. Chin EE, Zimmerman PT, Grant EG. Sonographic evaluation of upper extremity deep venous thrombosis. J Ultrasound Med. 2005; 24(6):829–38. 97. Malec L, Young G. Treatment of venous thromboembolism in pediatric patients. Front Pediatr. 2017;5:26. 98. Monagle P, Chan AK, Goldenberg NA, Ichord RN, Journeycake JM, Nowak-Göttl U, et al. Antithrombotic therapy in neonates and children: antithrombotic therapy and prevention of thrombosis, 9th

19  Vascular Imaging ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e737S–801S. 99. Hardman RL. Management of chronic deep vein thrombosis in women. Semin Intervent Radiol. 2018;35(1):3–8. 100. Lin PH, Chaikof EL. Embryology, anatomy, and surgical exposure of the great abdominal vessels. Surg Clin North Am. 2000;80(1): 417–33. 101. Coley BD. Pediatric applications of abdominal vascular Doppler imaging: part I. Pediatr Radiol. 2004;34(10):757–71. 102. Nagel K, Tuckuviene R, Paes B, Chan AK. Neonatal aortic thrombosis: a comprehensive review. Klin Padiatr. 2010;222(3):134–9. 103. Dieffenbach BV, Nath BD, Tracy ET, Kim HB. Management of symptomatic neonatal aortic thrombosis: when is surgery indicated? J Pediatr Surg Case Rep. 2019;47:101247. 104. Porras D, Stein DR, Ferguson MA, Chaudry G, Alomari A, Vakili K, et al. Midaortic syndrome: 30 years of experience with medical, endovascular and surgical management. Pediatr Nephrol. 2013;28(10): 2023–33. 105. Rumman RK, Nickel C, Matsuda-Abedini M, Lorenzo AJ, Langlois V, Radhakrishnan S, et al. Disease beyond the arch: a systematic review of middle aortic syndrome in childhood. Am J Hypertens. 2015;28(7):833–46. 106. Yan L, Li HY, Ye XJ, Xu RQ, Chen XY. Doppler ultrasonographic and clinical features of middle aortic syndrome. J Clin Ultrasound. 2019; 47(1):22–6. 107. Mendeloff J, Stallion A, Hutton M, Goldstone J.  Aortic aneurysm resulting from umbilical artery catheterization: case report, literature review, and management algorithm. J Vasc Surg. 2001;33(2):419–24. 108. Kim JI, Lee W, Kim SJ, Seo JW, Chung JW, Park JH. Primary congenital abdominal aortic aneurysm: a case report with perinatal serial follow-up imaging. Pediatr Radiol. 2008;38(11):1249–52. 109. Restrepo R, Ranson M, Chait PG, Connolly BL, Temple MJ, Amaral J, et  al. Extracranial aneurysms in children: practical classification and correlative imaging. AJR Am J Roentgenol. 2003;181(3):867–78. 110. Munk A, Darge K, Wiesel M, Troeger J. Diameter of the infrarenal aorta and the iliac arteries in children: ultrasound measurements. Transplantation. 2002;73(4):631–5.

939 111. Smillie RP, Shetty M, Boyer AC, Madrazo B, Jafri SZ. Imaging evaluation of the inferior vena cava. Radiographics. 2015;35(2):578–92. 112. Oliveira JD, Martins I. Congenital systemic venous return anomalies to the right atrium review. Insights Imaging. 2019;10(1):115. 113. Bartram U, Wirbelauer J, Speer CP. Heterotaxy syndrome – asplenia and polysplenia as indicators of visceral malposition and complex congenital heart disease. Biol Neonate. 2005;88(4):278–90. 114. Soundappan SV, Barker AP. Retrocaval ureter in children: a report of two cases. Pediatr Surg Int. 2004;20(2):158–60. 115. Kandpal H, Sharma R, Gamangatti S, Srivastava DN, Vashisht S.  Imaging the inferior vena cava: a road less traveled. Radiographics. 2008;28(3):669–89. 116. Khanna G, Rosen N, Anderson JR, Ehrlich PF, Dome JS, Gow KW, et al. Evaluation of diagnostic performance of CT for detection of tumor thrombus in children with Wilms tumor: a report from the Children’s Oncology Group. Pediatr Blood Cancer. 2012;58(4): 551–5. 117. Zhang L, Yang G, Shen W, Qi J.  Spectrum of the inferior vena cava: MDCT findings. Abdom Imaging. 2007;32(4):495–503. 118. Sheth S, Fishman EK.  Imaging of the inferior vena cava with MDCT. AJR Am J Roentgenol. 2007;189(5):1243–51. 119. Quencer KB, Friedman T, Sheth R, Oklu R.  Tumor thrombus: incidence, imaging, prognosis and treatment. Cardiovasc Diagn Ther. 2017;7(Suppl 3):S165–77. 120. Harbin MM, Lutsey PL. May-Thurner syndrome: history of understanding and need for defining population prevalence. J Thromb Haemost. 2020;18(3):534–42. 121. Xue GH, Huang XZ, Ye M, Liang W, Zhang H, Zhang JW, et  al. Catheter-directed thrombolysis and stenting in the treatment of iliac vein compression syndrome with acute iliofemoral deep vein thrombosis: outcome and follow-up. Ann Vasc Surg. 2014;28(4):957–63. 122. Carroll S, Moll S.  Inferior vena cava filters, May-Thurner syndrome, and vein stents. Circulation. 2016;133:e383–7.

20

Breast Nadia Nagra-Mahmood, Angie L. Miller, Jennifer L. Williams, and Harriet J. Paltiel

Abbreviations CT GCT IMLN MR PASH SMR

Computed tomography Granular cell tumor Intramammary lymph node Magnetic resonance Pseudoangiomatous stromal hyperplasia Sexual Maturity Rating

Introduction Ultrasound is the imaging modality of choice in evaluation of the pediatric breast. Mammography is rarely performed, as the developing breast is highly sensitive to the effects of ionizing radiation, and the large amount of fibroglandular tissue leads to low diagnostic sensitivity [1]. Since most pediatric breast lesions are benign, a conservative approach to management and treatment is warranted. Biopsy is generally avoided as the developing breast is uniquely vulnerable to iatrogenic injury which can lead to permanent disfigurement [2]. Most malignant breast masses in children are metastases from non-breast neoplasms. In this chapter, the ultrasound features of normal breast development, developmental N. Nagra-Mahmood (*) Edward B. Singleton Department of Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, USA e-mail: [email protected] A. L. Miller Department of Radiology, Children’s Hospital Colorado, University of Colorado School of Medicine, Aurora, CO, USA

anomalies, as well as benign and malignant lesions that affect the breast in children are discussed.

Technique Patient Positioning When performing breast ultrasound in young patients, it is important to ensure their comfort and to provide assurance while maintaining privacy with appropriate draping and positioning. Supine positioning is best for evaluating the medial half of the breast, while a contralateral posterior oblique position is better for evaluating the lateral half of the breast. It is critical to correlate the site of scanning with any palpable abnormality. Doppler ultrasound assessment of the breast should be performed using as little compression pressure as possible since intralesional flow can be decreased or completely obliterated if compression is overly zealous.

Ultrasound Transducer Selection High-frequency, high-resolution linear array transducers are most effective for breast tissue penetration and detection of lesions as small as 2 mm [3]. For superficial lesions, a stand-­ off pad may be used along with appropriate lesion placement in the focal zone to optimize image quality. Lower-frequency curved array transducers may be useful for imaging of deeper lesions. Power, gain, and focal zone settings must be optimized to permit a distinction between solid masses and cysts.

J. L. Williams Department of Radiology, University of Central Florida College of Medicine, Maitland, FL, USA

Imaging Approaches

H. J. Paltiel Division of Ultrasound, Department of Radiology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA

The imaging field of view should include all breast tissues from the skin surface to the chest wall. The pectoralis muscle can be used as a landmark to identify the posterior breast

© Springer Nature Switzerland AG 2021 H. J. Paltiel, E. Y. Lee (eds.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-56802-3_20

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border. Imaging must evaluate the nipple, subcutaneous fat, fibrofatty and fibroglandular tissue, pectoralis muscle, and ribs. Artifactual shadowing may occur due to Cooper ligaments, a prominent costochondral junction, or a rib posterior to the pectoralis muscle [4]. The nipple or the cartilaginous portion of a rib may be mistaken for a breast lesion. Appropriate compression of the breast tissue along with transducer angulation may reduce posterior acoustic s­ hadowing, further reducing the possibility of mistaking normal tissue for a mass. Doppler evaluation of breast lesions improves diagnostic accuracy when used in conjunction with grayscale imaging, particularly when attempting to differentiate a solid mass from a cyst. Color Doppler is also useful in aiding ­ultrasound-guided biopsies in order to avoid puncturing blood vessels that may result in bleeding or hematoma [5]. Elastography is a useful tool for measuring the stiffness of a lesion by applying mechanical stress [6]. Using a shear wave technique, the stiffness of a lesion in the breast is measured using kilopascals [7]. The stiffer the lesion, the more likely it is to be malignant. Although elastography is used to evaluate breast masses in adults, there is very little data on its utility in the pediatric population.

Normal Development and Anatomy Normal Development The breast is composed of lobules that connect to the nipple via a series of ducts (Fig. 20.1). Normal breast development occurs in two stages. The first stage begins at approximately 5 weeks of gestation with ectodermal thickening along the ventral surface of the body from the axilla to the groin to create the mammary crest or ridge (Fig. 20.2). This is followed by normal involution of the mammary ridge, except at the fourth intercostal space where the primary breast bud is located. Failure of involution of the mammary ridge results in the development of accessory nipples (polythelia) or accessory breast tissue (Fig. 20.3) [8]. Prior to the onset of puberty, the primitive breast tissue proliferates into epithelial lined ducts that end in terminal duct lobular units at the site of the primary breast bud [3]. These ducts are often prominent after birth as they respond to maternal hormones and can result in palpable breast nodules in the neonate. The second stage of breast development, known as thelarche, usually commences at approximately 9 years of age in Caucasians and between 7 and 8 years of age in African

Skin(cut)

First rib

Pectoralis major muscle Suspensory ligament Adipose tissue Lobe

Areola Nipple Opening of lactiferous duct Lactiferous sinus Lactiferous duct Lobule containing alveoli

Fig. 20.1  Diagram of normal breast anatomy

Lobe

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Level of section C Mammary ridge

Remnant of mammary ridge which produces primary mammary bud

a

b

Primary mammary bud (Primordium of mammary gland)

Site of depressed nipple

Mammary pit

Areola of breast

Epidermis Lactiferous duct

c

d Mesenchyme

e Dermis

Secondary mammary buds

f Mammary gland

Fig. 20.2  Diagram of normal mammary gland development. (a) Ventral view of an embryo at 28 days of gestation showing mammary ridges. (b) Similar view at 6 weeks of gestation showing the remnants of the mammary

ridges. (c) Transverse section of a mammary ridge at the site of the developing mammary gland. (d–f) Similar sections showing successive stages of breast development between the 12th week of gestation and birth

Americans [9]. During thelarche, estrogen secretion causes ductal and fat proliferation, while progesterone secretion leads to lobular growth and differentiation (Fig. 20.4). Tanner staging, also known as Sexual Maturity Rating (SMR), is an objective classification system that is used to document and track the development and sequence of second-

ary sex characteristics of children during puberty. The scale defines physical measurements of development based on external primary and secondary sex characteristics, including the size of the breasts, genitals, and development of pubic hair. There are five Tanner stages of breast development under hormonal stimulation (Fig. 20.5, Table 20.1) [10].

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Table 20.1  Correlation of Tanner stages of breast development with clinical and ultrasound features Tanner stage Clinical presentation I Papilla is elevated

II

III

IV

Breast mound forms with elevation of the papilla

Areola enlarges in diameter Breast and areola complex Increased size of hypoechoic breast bud and prominence continue to develop and of the ducts form a palpable subareolar nodule Elongation of hypoechoic Areola and papilla now glandular tissue with greater project to form a extension of ducts into the secondary mound above surrounding fibrofatty soft the breast tissue

Milk line

V

Ultrasound features Small amount of echogenic tissue in the subareolar region Nodular hypoechoic breast bud with a few developing ducts and surrounding fibrofatty tissue

Projection of the papilla as areola regresses

Subcutaneous fat may be identified Mature breast tissue composed of nodules of hypoechoic glandular tissue with surrounding stromal tissue Increased subcutaneous fat

Fig. 20.3  Diagram of the milk line or mammary ridge

Fig. 20.4  Normal fibroglandular breast tissue in a 16-year-old female. (a) Transverse grayscale ultrasound image of the breast reveals echogenic fibrous and fatty glandular tissue (asterisks) with hypoechoic nodules

(arrowheads). (b) Longitudinal grayscale ultrasound images of the right (RT) and left (LT) breasts show echogenic fibroglandular tissue (FG) and the pectoralis muscle (P) forming the posterior border of the breast

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Tanner staging of breast development

Stage I: No palpable glandular breast tissue

Stage II: Breast bud palpable under areola

Stage III: Breast tissue palpable outside areola. No areolar development

Stage IV: Areola elevated above contour of the breast

Stage V: Areolar mound recedes back into single breast contour with areolar hyperpigmentation and nipple protrusion

Fig. 20.5  Tanner staging of breast development

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Normal Anatomy In Tanner Stage I, the breast has a prepubertal appearance. Ultrasound demonstrates echogenic retroareolar tissue (Fig. 20.6a). In Tanner Stage II, there is a small breast bud. Ultrasound demonstrates a hypoechoic retroareolar nodule with centrally located, linear hypoechoic ducts (Fig. 20.6b). In Tanner Stage III, the breast bud enlarges beyond the areola, the areola becomes pigmented, and small glands form on the areola, the Montgomery glands (Fig. 20.6c) [2, 11]. There is further breast enlargement, but the contours a

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of the areola are not separate from the breast contours. Breast ultrasound demonstrates an increased size of the hypoechoic subareolar nodule and greater prominence of the ductal projections into the surrounding fibrofatty soft tissues. In Tanner Stage IV, the areola and nipple project above the contour of the breast to form a secondary mound. The areola enlarges and becomes more pigmented as does the nipple. Breast ultrasound reveals elongation of the hypoechoic nodular glandular tissue with greater extension of the ducts into the surrounding soft tissues (Fig.  20.6d). Subcutaneous adipose tissue is identified in some children [12]. b

c d

e

f

Fig. 20.6  Ultrasound features of normal female breast development. (a) Tanner Stage I in a 6-month-old female. Transverse grayscale ultrasound image shows a small focus of echogenic retroareolar tissue (arrows). (b) Tanner Stage II in an 8-year-old female. Longitudinal grayscale ultrasound image shows a small, hypoechoic retroareolar breast bud (asterisk) and a few central hypoechoic ducts (arrowheads) surrounded by echogenic fibrofatty tissue (arrows). (c) Tanner Stage III in a 10-year-old female. Longitudinal grayscale ultrasound image shows image shows increased size of the hypoechoic breast bud and prominence of the ducts

(arrowheads) extending into the surrounding soft tissues. (d) Tanner Stage IV in a 14-year-old female. Longitudinal grayscale ultrasound image shows elongation of the breast bud and greater extension of the ducts (arrowheads) into the surrounding fibrofatty tissue (arrows). (e, f) Tanner Stage V in a 20-year-old female. Longitudinal grayscale ultrasound images show (e) a well-defined nipple (asterisk) and a mature breast contour with prominent subcutaneous fat (arrowheads). There is loss of the hypoechoic central nodule. (f) There are innumerable hypoechoic, ovoid fibroglandular lobules (arrows)

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In Tanner Stage V, breast development is complete. Ultrasound demonstrates a mixture of hypoechoic and echogenic tissues reflecting nodules of glandular tissue dispersed within stromal tissue. The subareolar hypoechoic nodule noted in the previous stages is no longer visible (Fig. 20.6e and 20.6f) [12].

Surgical removal is indicated if the accessory breast tissue causes physical discomfort or for cosmetic reasons.

Anatomic Variants

Poland syndrome is a congenital partial or total absence of the pectoralis muscles, particularly the sternocostal head of the pectoralis major, resulting in absence of the anterior axillary fold. Webbing of the axilla with an anomalous fibrous band extending from the thorax to the humerus may sometimes occur. In addition, there is usually deformation or absence of ribs and hypoplasia or absence of the breast, areola, and subcutaneous tissue [15]. Poland syndrome usually presents at birth as an asymmetry of the chest with frequent ipsilateral abnormalities. There is no major role for ultrasound in either diagnosis or management. Treatment consists of reconstructive procedures tailored to the deformities present in individual patients.

Accessory Breast Tissue Accessory breast tissue results from a failure of regression of the primitive mammary tissue. It usually presents as an extension of tissue from the upper outer quadrant of the breast into the axilla, but can occur anywhere along the course of the embryologic mammary ridge, from the axilla to the groin and medial thigh. On ultrasound evaluation, accessory breast tissue is identical to normal breast tissue and should not be misdiagnosed as an abnormality (Figs. 20.7 and 20.8) [13, 14].

Congenital Anomalies Poland Syndrome

Polythelia/Polymastia

Axillary tail

Failure of regression of the mammary ridge results in polythelia (accessory nipples) or polymastia (accessory mammary glands) anywhere along the embryologic mammary ridge [4, 12, 16].

Amastia/Athelia/Amazia

Fig. 20.7  Diagram of accessory breast tissue. The normal extension of breast tissue into the axilla is known as the axillary tail or tail of Spence

a

Amastia/hypomastia is the congenital absence or underdevelopment of fibroglandular breast tissue [2, 16]. This entity is often associated with chronic systemic diseases such as Crohn disease or malnutrition. Athelia refers to absent development of one or both nipples. Amazia is the presence of a nipple and areola in the absence of one or both mammary glands. The most common cause is iatrogenic, related to biopsy of the immature breast or excision of the breast bud. Radiation therapy prior to puberty has also been reported as a cause of amazia [15]. b

Fig. 20.8  Accessory breast tissue in a 17-year-old female. (a) Longitudinal and (b) transverse grayscale ultrasound images of the left axilla show accessory breast tissue (asterisks)

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Developmental Anomalies Premature Thelarche Premature thelarche is defined as breast development in females younger than 8 years of age. It may occur in isolation or in association with precocious puberty. If there are signs of pubic or axillary hair development, further endocrinologic workup and pelvic ultrasound are indicated. If isolated thelarche is noted between the ages of 1 and 3 years, it is usually self-limited, and no further workup or treatment is required (Fig. 20.9) [4].

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If reduction treatment does not stop breast growth, a subcutaneous mastectomy with complete removal of the breast tissue is the procedure that is least likely to lead to recurrence but is more deforming. For patients requiring a mastectomy, psychosocial issues may contribute to stress, depression, anxiety, and difficulties with body image and acceptance by peers [20, 21].

Gynecomastia

Juvenile hypertrophy, also known as mammary gigantism, macromastia, or virginal hypertrophy, is a rare disorder. It is characterized by a rapid and disproportionate growth of one or both breasts in girls. Breast enlargement is usually symmetric and bilateral, but can be unilateral or asymmetric. This condition usually develops rapidly, within weeks to months, at a time of a hormonal surge such as puberty or pregnancy. It is thought to occur as a result of end-organ hypersensitivity to normal levels of sex hormones [17]. It has also been reported in the setting of autoimmune disease and in association with a variety of pharmacological agents where the pathogenic mechanisms are uncertain [18]. Dense fibroglandular tissue in both breasts without a focal mass has been documented by ultrasound and magnetic resonance (MR) imaging [19]. In girls with developing breasts, surgery should be avoided, and anti-estrogen agents such as tamoxifen should be the first line of treatment. Reduction mammoplasty results in an improved appearance of the breast, but it is important to advise the patient of the possibility of recurrence. Tamoxifen therapy following surgery may decrease the recurrence rate.

Gynecomastia is the presence of excessive breast tissue in males and is thought to be caused by an imbalance between the stimulatory effect of estrogen and the inhibitory effect of androgen on the breast tissue [22]. More recent data also appears to implicate leptin, an enzyme in adipose and breast tissue that increases estrogen, in the development of gynecomastia [23]. Physiological gynecomastia can develop in the neonatal period, during puberty, and in old age. It may also occur in association with various pathological conditions. Approximately 60% to 90% of all newborns will have gynecomastia due to transplacental passage of estrogen [23]. Gynecomastia in newborns usually regresses in 2 to 3 weeks and resolves within the first year of life (Fig. 20.10). Pubertal gynecomastia has a peak prevalence of 40% to 65% between 13 and 14 years of age and resolves over a period of months to 2 years in 85 to 90% of cases [23]. Clinically, patients present with a palpable retroareolar mass that is unilateral or bilateral. There can be associated tenderness. Prepubertal or pronounced gynecomastia generally requires further evaluation to rule out an estrogen-secreting mass such as a Sertoli-Leydig cell tumor or an adrenal cortical tumor. Choriocarcinoma, hepatoblastoma, or other gonadotropin-­ secreting tumors must also be considered. Additional medical conditions, including liver disease, Klinefelter syndrome, neurofibromatosis type I, and androgen insensitivity, can be associated with male breast enlargement. Anabolic steroids, corticosteroids, digitalis, marijuana, herbal remedies, and tricy-

Fig. 20.9  Maternal hormone stimulation in a 1-year-old female with a left breast mass. Transverse grayscale ultrasound images demonstrate

asymmetric enlargement of (a) the left (L) breast tissue (arrow) compared to (b) the normal right (R) breast tissue (arrow)

Juvenile (Virginal) Hypertrophy

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Fig. 20.10  Gynecomastia in a 13-year-old male with right breast development. Transverse grayscale ultrasound images demonstrate subareolar

tissue (arrows) asymmetrically enlarged in (a) the right (R) breast compared to (b) the left (L) breast. P, Pectoralis muscle

clic antidepressants have all been reported to cause gynecomastia [24]. Ultrasound evaluation is performed to exclude an underlying mass. Gynecomastia can have a variable appearance, including that of a heterogeneously dense breast (diffuse pattern), a fanshaped density radiating from the nipple (nodular pattern), or a flame-shaped subareolar density radiating from the nipple with finger-like projections interdigitating into the deeper adipose tissue (dendritic pattern) [25]. Pseudogynecomastia occurs in the setting of general obesity where there is an accumulation of subareolar adipose tissue rather than breast tissue. In these patients, ultrasound will show only adipose tissue without glandular breast tissue [3, 13, 17]. Since the majority of cases of gynecomastia are physiological, they do not require treatment other than reassurance. For pathological gynecomastia, the underlying cause should be addressed. If gynecomastia persists, tamoxifen is the treatment of choice. Reduction mammoplasty can be considered for resistant cases. Counseling is often important and should be considered in boys with issues of body image and self-esteem.

of the breast that results in breakdown of the skin overlying the nipple or mucous membranes and permits the entry of pathogens. It occurs more often in girls and is rarely bilateral. Less than 50% of all patients in this age group will present with fever, and fewer than 75% will have leukocytosis [26]. If the infection does not stay confined to the breast, other complications such as cellulitis, sepsis, or brain abscess can occur. Mastitis in older children is most often due to direct injury to the breast, infection, mammary duct obstruction, or lactation. Most cases develop in girls, with the usual pathogen being Staphylococcus aureus [3, 27, 28]. Most children present with a tender inflamed breast, often associated with fever and leukocytosis. An abscess is a localized collection of necrotic or inflammatory exudate and usually develops in lactating females as a complication of breast-feeding and mastitis. Skin breaks in the nipple are believed to lead to the development of a breast abscess. S. aureus is again the most common underlying pathogen [29]. Ultrasound is a key diagnostic tool in detecting neonatal mastitis and in identifying abscesses. Ultrasound features of mastitis include thickened, indurated, echogenic breast tissue caused by inflammation. Color Doppler images demonstrate increased vascularity. If an abscess is present, it appears as a hypoechoic, round, ovoid, or irregular mass containing a variable amount of internal echogenic debris. The walls of the abscess are often thickened, and color Doppler demonstrates peripheral increased vascularity with no central flow (Figs. 20.11 and 20.12). Antibiotic therapy is the treatment of choice. If intervention is required, ultrasound is useful in guiding aspiration and drainage.

Inflammatory Lesions Mastitis and Abscess Mastitis occurs most commonly in lactating females, but can also develop in children with a bimodal distribution. Neonatal mastitis refers to inflammation of the breast in the first 2 months of life, with or without an abscess [26]. It is uncommon and thought to be due to maternal estrogen stimulation

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Fig. 20.11  Mastitis and abscess in a 14-year-old female. Transverse (a) and longitudinal (b) grayscale ultrasound images of the left breast demon-

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strate an ill-defined hypoechoic abscess (A) with internal echoes. The surrounding soft tissues are diffusely echogenic, in keeping with mastitis

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Fig. 20.12  Breast abscess in an 18-year-old female. (a) Longitudinal grayscale ultrasound image of the right breast demonstrates a well-defined mass with thick walls and internal echogenic debris. (b) Longitudinal color

Doppler ultrasound image demonstrates increased vascularity at the periphery of the abscess

Non-neoplastic Lesions

respond to antibiotic treatment and ­termination of breast-feeding. Surgery may be indicated for those children who do not respond to conservative measures [30, 31].

Mammary Duct Ectasia Mammary duct ectasia or duct ectasia is a rare entity of unknown etiology that most often develops in infants and young children. Histologically there are dilated ducts ­surrounded by fibrosis and inflammation. Patients can present with nipple discharge, breast tenderness, or a palpable mass. Affected children are susceptible to infection, usually by S. aureus and Bacteroides species as a consequence of stagnant secretions. Ultrasound findings include dilated, tubular, hypoechoic structures which may contain internal echogenic debris secondary to hemorrhage (Fig.  20.13). Management depends on the clinical presentation. Most patients

 etroareolar Cysts (Obstructed Glands of R Montgomery) Retroareolar cysts or obstructed glands of Montgomery usually develop in adolescent females [32]. These cysts are located at the edge of the areola and are sebaceous glands intimately associated with the terminal portions of lactiferous ducts that arise from the mammary lobules [32]. They are believed to develop as a result of obstruction of the chan-

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Fig. 20.13  Ductal ectasia in a 14-year-old female. (a) Transverse grayscale ultrasound image demonstrates tubular, thin-walled anechoic structures (white arrow) with increased posterior through-­transmission

(arrowhead). Note the thick-walled duct containing echogenic debris (black arrow). (b) Transverse color Doppler ultrasound image shows hyperemia of the thick-walled duct

Fig. 20.14  Retroareolar (Montgomery) cysts in a 9-year-old female. (a) Transverse grayscale ultrasound image demonstrates multiple,

thin-walled, anechoic cysts in the retroareolar region. (b) Transverse color Doppler ultrasound image shows no flow within the cysts

nels that drain Montgomery’s areolar tubercles. Once the channel is obstructed, metaplasia of the squamous lining occurs, resulting in faulty resorption of duct secretions. The distended, obstructed channel and the acini in the accessory lobes lead to retroareolar cyst development. Retroareolar cysts may be asymptomatic or symptomatic. Ultrasound is useful in cyst characterization [32]. Cysts may be single or multiple and are usually anechoic, round, or tubular in shape with or without internal debris or a fluid-fluid level. They are often bilateral and generally measure less than 2 cm in diameter. When there is superimposed cyst infection, color Doppler will demonstrate mural hyperemia (Fig. 20.14). Asymptomatic cysts tend to be avascular by ultrasound. Patients with a painful areolar or tender breast mass may have cysts with mural vascularity and internal debris. Most retroareolar cysts resolve spontaneously. Conservative management is the treatment of choice for asymptomatic cysts with monitoring by serial ultrasound studies until resolution.

Patients with symptomatic cysts are treated with antibiotics and require more frequent follow-up. Incision and drainage are reserved for those rare cysts that develop into an abscess [33].

Fibrocystic Disease Fibrocystic disease is the most commonly encountered benign disease of the breast [34]. It most often occurs in adult women but can occasionally develop in adolescent girls. Fibrocystic breast disease is characterized by marked cell proliferation in response to fluctuations in estrogen or progesterone. Cyst formation is thought to result from a disequilibrium between fluid production and resorption, resulting in dilation of the lobular acini of the breast. Cysts can also form if a duct leading to a terminal lobule becomes obstructed. In adult females, benign fibrocystic disease has a low relative risk of malignancy. Only proliferating lesions with atypia

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Fig. 20.15  Fibrocystic disease in a 17-year-old female. (a) Transverse grayscale ultrasound image demonstrates a spherical anechoic structure (arrowheads) with posterior acoustic enhancement. Transverse g­ rayscale

(b) and color Doppler (c) ultrasound images demonstrate a smoothwalled, anechoic cyst with peripheral rim calcification (arrowhead), posterior acoustic enhancement (arrow), and no internal flow

are associated with a true risk of increased breast cancer [35], which is extremely rare in the pediatric population. Fibrocystic breast disease may present as single or multiple cysts throughout the breast parenchyma and occasionally as a palpable, non-tender mass. However, if the cysts become inflamed or infected, they can present as a tender palpable mass. Ultrasound demonstrates single or multiple dilated, hypoechoic cysts. The cysts often have thin, imperceptible walls and demonstrate posterior acoustic enhancement. Thick-walled cysts with internal echoes can be seen when there is superinfection (Fig. 20.15). Treatment of cysts associated with fibrocystic disease is conservative. If the cyst is symptomatic, aspiration is indicated. If the cyst appears complex and has a thick wall or superinfection is suspected, antibiotics are indicated. The differential diagnosis includes localized ductal ectasia, abscess, and galactocele.

in males [36]. Patients may present with painless, unilateral, or bilateral breast enlargement [37]. A galactocele is not usually associated with other endocrine disorders. Although the precise etiology is unknown, the cause is thought to be multi-­ factorial, and recently an association with hyperprolactinemia has been found [38]. The most common associations are (1) the presence of secretory epithelium that may be stimulated by prolactin as a result of prior trauma to the breast tissue [24, 39], and (2) ductal obstruction without fluid resorption, leading to fluid accumulation and galactocele formation. Ultrasound findings vary depending on the degree of milk or protein within the cyst. A galactocele may be anechoic or hyperechoic and often contains fat-fluid levels. When predominantly fluid, it will appear relatively hypoechoic. As the degree of protein or fat increases within the cystic mass, it will appear more echogenic (Fig. 20.16). MR imaging demonstrates a multiloculated mass with enhancing septa. On mammography, a fat-fluid level may be appreciated within a benign-appearing mass. Conservative management is the treatment of choice in prepubertal females in order to avoid damage to the developing breast tissue [37]. Fine needle aspiration of the lesion is sometimes performed. If an enlarging lesion occurs in a male,

Galactocele A galactocele is a thin-walled cyst that contains milk and is most often encountered in lactating women. Galactoceles are a rare cause of breast enlargement in children and can occur

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Fig. 20.16  Galactoceles in two different patients. (a) 17-year-old female with prior breast trauma. Transverse g­ rayscale ultrasound image depicts a well-circumscribed echogenic mass (arrowhead). (b) 20-year-

a

b

old female with recent cessation of breast-feeding. Transverse grayscale ultrasound image shows numerous dilated, communicating ducts (arrows) containing homogeneous echogenic debris

b

Fig. 20.17  Hematoma of the breast in a 13-year-old female. (a) Transverse grayscale ultrasound image shows a well-circumscribed mass (arrows)

containing internal debris. (b) Transverse color Doppler ultrasound image demonstrate no flow within the hematoma

surgical excision is recommended [40]. A galactocele can persist for months to years and should be considered in the differential diagnosis of an infant with an enlarging breast mass.

echoic with ill-defined borders. As the blood ages and liquefies, it becomes more hypoechoic and septated with increased definition of its walls. Fat-fluid levels can also be present (Fig. 20.17). A breast hematoma is followed with serial ultrasound monitoring until resolution. If it persists or causes pain, aspiration may be both diagnostic and therapeutic. It is important to distinguish a hematoma from an abscess or fat necrosis.

Hematoma A hematoma is a localized hemorrhage. In the breast, a hematoma develops most often after blunt trauma, frequently during athletic activity. It can also be iatrogenic. An adequate history and physical examination to detect bruising over the breast are key elements in diagnosis [4, 16]. Patients with coagulopathic conditions may also be more prone to developing a breast hematoma. Ultrasound appearance varies, depending on the age of the hematoma. In the acute phase, a hematoma appears hyper-

Fat Necrosis Fat necrosis typically develops after trauma as a result of fat saponification, the action of tissue lipases on released fat [2]. It can also occur after surgery, biopsy, infection, and duct ectasia, among other etiologies [41–43]. It may manifest as a

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fixed or mobile mass frequently located near the nipple or skin, locations that are particularly vulnerable to injury. The appearance of fat necrosis by ultrasound is variable and depends on the extent of the inflammatory response to the trauma. When there is a prominent inflammatory and fibrotic reaction, fat necrosis can appear as a solid, spiculated lesion or a complex cyst with mural nodules. When there is little tissue response, an anechoic oil cyst may develop. As the fat liquefies, the appearance of the lesion can change, and internal debris and fat-fluid levels may be identified. Occasionally the mass may become more solid in appearance. Typically these lesions become smaller over time. If serial examinations depict an increase in size, it should be biopsied.

Intramammary Lymph Node An intramammary lymph node (IMLN) may be benign or malignant and occurs with an incidence of approximately 0.7–48% on evaluation of post-surgical specimens [44, 45]. It can be detected on mammography, computed tomography (CT), MR imaging, or ultrasound. IMLN is most prevalent in the upper outer quadrant of the breast and can be differentiated from an axillary lymph node as it is surrounded by breast tissue. Ultrasound is a good tool for distinguishing benign from malignant IMLNs. Features of a benign IMLN include a welldefined, round or ovoid nodule usually measuring about 1 cm in diameter and containing an echogenic hilum (Fig. 20.18) [46]. Features of a malignant or suspicious IMLN include an irregular shape, indistinct borders, a thickened cortex, and loss of a distinct central fatty hilum. Color Doppler evaluation demonstrates increased vascularity compared to a normal or benign intramammary lymph node. Not all suspicious IMLNs are malignant. Some may have concerning features as a result of prior trauma, biopsy, radiation, or surgery. Mastitis or other infectious or inflammatory

a

Fig. 20.18 Intramammary lymph node in a 13-year-old female. (a) Transverse grayscale ultrasound image show a normal lymph node in the breast with a well-defined, echogenic hilum (arrow). (b) Transverse

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lesions of the breast can lead to the development of IMLNs. Systemic disease such as lymphoma can also be a source of enlarged IMLNs. Management depends on the underlying cause of enlargement. Differentiation between benign and malignant lesions should be made by fine needle aspiration.

Vascular Malformations Vascular malformations of the breast are due to developmental anomalies consisting of endothelial lined, dilated vascular channels [47]. These lesions are present from birth but may not become clinically evident until later in life. Vascular malformations are further divided according to channel type and may be lymphatic, venous, capillary, arterial, arteriovenous or combined. Of all the vascular malformations, venous malformations are the most common [48, 49]. They are more likely to be sporadic in nature rather than inherited. Ultrasound with color and spectral Doppler is an excellent modality for ­evaluation of vascular malformations as it is a noninvasive means of assessing lesion morphology and flow characteristics.

Venous Malformation Venous malformations can occur throughout the body, including the breast [50]. They often manifest as a bluish, painless, compressible mass that is present at birth and enlarges as the child grows. They can be localized or diffuse in extent. Enlargement of the lesions frequently occurs during puberty or pregnancy. Ultrasound features of venous malformations are variable and include both well-circumscribed and ill-defined masses that may be hypoechoic and contain numerous vascular channels of varying size. Depending on channel size, color Doppler imaging with spectral analysis may or may not be able to detect internal flow.

b

color Doppler ultrasound image demonstrates normal lymph node vascularity

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Treatment varies according to lesion size and extent. Sclerotherapy is often performed [51]. Surgery can be curative for localized lesions. Combination therapy is reserved for patients with extensive disease.

Lymphatic Malformation Lymphatic malformation of the breast is a rare, benign lesion of the lymphatic vessels. It consists of endothelial-lined dilated channels. As fluid collects within the channels over time, they enlarge and may communicate with the skin. Present from birth, they can be divided into three categories, depending on the size of their cystic spaces: microcystic, macrocystic, or combined [52]. Most lymphatic malformations of the breast are asymptomatic. They are most frequently located in the upper, outer quadrant of the breast, in the tail of Spence, or beneath the areola, likely related to the drainage pattern of breast lymphatics in the direction of the axilla and tail of Spence. Grayscale ultrasound findings of lymphatic malformation vary from a simple cyst to a multiseptated mass with varying cystic and apparently solid components. Microcystic lesions frequently appear solid due to the small size of the component lymphatic channels. Color Doppler imaging generally demonstrates no significant internal vascularity although small septal vessels are occasionally detected [47]. MR imaging is the most accurate technique for diagnosing these lesions and determining their overall extent. Differential diagnoses include simple cyst, fibrocystic change, lymphocele, and hematoma [53]. Treatment depends on the size and location of the lesion. Treatment options include surgery, sclerotherapy, or pharmacologic treatment with sirolimus [52].

Neoplasms A wide variety of neoplasms can occur within the breast. Table 20.2 lists benign and malignant breast tumors encountered in the pediatric population. Table 20.2  Benign and malignant breast mass classification Benign Fibroadenoma Hemangioma Intraductal papilloma Juvenile papillomatosis Pseudoangiomatous stromal hyperplasia (PASH) Lactating adenoma Desmoid tumor Granular cell tumor

Malignant Cystosarcoma phyllodes Carcinoma Angiosarcoma Hematologic malignancies Metastases

Benign Tumors Fibroadenoma Fibroadenoma is the most frequently encountered mass in the pediatric breast and comprises 91% of all pathologically proven solid breast masses [54]. The average age at diagnosis is 16  years [27], and is more frequent in the African American population. Histologically, fibroadenoma is a fibroepithelial mass that results from overgrowth of the connective tissue stroma surrounding the breast lobules. Fibroadenoma only occurs in females since breast lobules do not occur in males. Fibroade­ noma. These benign tumors are sensitive to the effects of estrogen and grow rapidly during puberty, pregnancy, and lactation. Fibroadenomas are categorized according to their size and histology. Classic fibroadenomas have a mean diameter of 2 to 3  cm. A giant fibroadenoma has a mean diameter greater than 5 cm. Giant fibroadenomas occur in adolescent girls. Juvenile fibroadenomas are rapidly growing, lesions that differ from classic fibroadenoma due to their abundance of stromal tissue. Fibroadenomas are usually solitary but can be multiple, especially juvenile fibroadenoma [54]. Patients present with a mobile, rubbery, non-tender mass. Most fibroadenomas grow slowly and may remain stable for months to years. Some lesions can undergo spontaneous regression. Ultrasound typically demonstrates an anechoic to hypoechoic oval mass with macrolobulations occurring in up to 57% [54]. Fibroadenomas are oriented parallel to the skin surface, and most display posterior acoustic enhancement. Features such as spiculated, angulated margins or posterior acoustic shadowing are concerning for other pathology. Internal microcalcification, hemorrhage, and debris may occur, resulting in a more complex appearance. Color Doppler imaging can show prominent vascularity (Fig. 20.19). Treatment of fibroadenoma varies according to lesion size. Short-term follow-up is recommended for a small mass with benign features and without rapid growth. For a mass greater than 5 cm in diameter or a mass that is painful, surgical excision is indicated regardless of its ultrasound characteristics. Hemangioma The most common vascular lesion found soon after birth in the pediatric breast is an infantile hemangioma [2]. These lesions are benign tumors that generally appear within the first month of life and undergo a phase of accelerated growth for about 1 year, followed by slow involution over several years. Ultrasound findings include an oval or lobulated mass of variable echogenicity with well-defined margins. Within the mass, dilated vascular channels are present that demonstrate prominent low resistance arterial blood flow with color and spectral Doppler. Pulsatile venous flow can also be detected

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Fig. 20.19  Fibroadenomas in two different patients. (a) Classic fibroadenoma of the breast in a 17-year-old female. Transverse grayscale ultrasound image demonstrates a wider-than-tall, hypoechoic elliptical mass with posterior acoustic enhancement (arrow). (b) Longitudinal color Doppler

ultrasound image reveals a small amount of internal vascularity. (c) Giant fibroadenoma of the breast in a 15-year-old female. Longitudinal grayscale ultrasound image demonstrates a large homogeneous hypoechoic mass (arrow)

due to the presence of microvascular arteriovenous shunting (Fig. 20.20) [47, 52]. Treatment of infantile hemangioma may not be necessary unless there are complications such as ulceration, bleeding, or cosmetic issues. Propranolol, a β-blocker, is the drug of choice for these lesions when therapy is indicated. Steroids can be used if an immediate response is required or if the lesion is unresponsive to propranolol. Topical timolol, also a β-blocker, is often prescribed for isolated skin lesions. Laser therapy is useful for ulcerated lesions. Surgery is not usually required.

it can occur at any age, intraductal papilloma is relatively rare in children, usually affecting middle-aged women. Patients present with a non-tender or tender mass with or without nipple discharge [55]. Ultrasound demonstrates a dilated duct containing a solid, elongated mass, often located near the nipple, that may or may not demonstrate hypervascularity with color Doppler (Fig.  20.21). The dilated duct may also contain anechoic fluid, depending on the degree of ductal obstruction. The mass can be densely calcified. Lesions are usually treated with surgical excision. Histology is necessary for a definitive diagnosis [56] as the imaging features cannot distinguish benign papilloma from a malignant lesion. Intraductal papillomas rarely recur and are associated with a good prognosis.

Intraductal Papilloma Intraductal papilloma is a benign condition that develops as a result of ductal epithelial cell growth and proliferation. It is located in the subareolar central ducts. Although

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Fig. 20.20  Infantile hemangioma of the breast in a 15-month-old female. (a) Longitudinal grayscale ultrasound image demonstrates a mildly lobulated, hypoechoic mass immediately deep to the nipple

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(arrowhead). (b) Longitudinal color Doppler ultrasound image shows multiple enlarged vessels coursing through the lesion

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Fig. 20.21  Intraductal papilloma of the breast in a 19-year-old female. acoustic enhancement (arrowhead) is noted (b) Longitudinal color (a) Longitudinal grayscale ultrasound image demonstrates a well-­ Doppler ultrasound image reveals mild peripheral hyperemia but no intercircumscribed intraductal cystic mass (arrow) containing debris. Posterior nal vascularity

Juvenile Papillomatosis Juvenile papillomatosis of the breast is a rare, non-­malignant, proliferative process that occurs in older adolescents and young women less than 30 years of age [2, 57]. It usually presents as a well-defined, mobile, firm mass located in the periphery of the breast. Although it is a benign disorder, approximately 33–58% of affected individuals have a strong family history of breast cancer, and co-existing breast cancer is present in approximately 10% [58, 59]. The gross pathologic appearance of juvenile papillomatosis is that of a mass containing multiple small cysts of varying size, hence the name “Swiss cheese disease” [27, 58]. Histologically, juvenile papillomatosis is characterized by multiple intraductal papillomas, ductal hyperplasia, ductal ectasia, perifocal sclerosing adenosis, and calcification [59]. Findings on ultrasound include hypoechoic masses clearly delineated from the normal breast parenchyma and filled with cysts of varying size. Microcalcifications can occur. Color Doppler shows no abnormally increased vascularity (Fig. 20.22) [16, 60]. These imaging features are typical but not specific. MR imaging can be useful in depicting the cysts on T2-weighted images as well as marked enhancement after intravenous contrast administration [16, 61]. Given the association of juvenile papillomatosis with breast cancer, adequate treatment requires complete surgical

excision with wide margins. Patients at an increased risk of recurrence are those with a family history of breast carcinoma, multiple sites of involvement, atypical ductal hyperplasia, and incomplete excision [60]. Annual monitoring for breast cancer is recommended, and female family members should undergo breast screening.

 seudoangiomatous Stromal Hyperplasia P Pseudoangiomatous stromal hyperplasia (PASH) is a myofibroblastic growth disorder that is thought to be hormonally mediated via progesterone. Myofibroblastic cell nuclei have been shown to express progesterone receptors [62, 63]. PASH can present anywhere from adolescence to old age, although it is most often seen in adolescent females [16, 24]. Both young and adult males with gynecomastia can also be affected. Clinically PASH presents as a painless mass that is mobile, rubbery, and firm and may display rapid growth in adolescents [62]. The ultrasound findings of PASH are nonspecific [16, 64]. Most often there is a well-defined, homogenous, and hypoechoic mass. Cysts are virtually never identified. Lesions tend to be oriented parallel to the long axis of the skin surface, similar to what is seen with fibroadenoma. This similarity in appearance may cause difficulty in distinguishing between the two entities (Fig. 20.23). Biopsy or complete excision is generally necessary to confirm the diagnosis of PASH.

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Fig. 20.22  Juvenile papillomatosis of the breast in a 17-year-old female. (a) Transverse grayscale ultrasound image demonstrates a mass consisting of multiple anechoic cysts (arrowheads) within an echogenic

a

stroma resulting in a characteristic “Swiss cheese” appearance. (b) Transverse color Doppler ultrasound image reveals the avascular nature of the lesion

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Fig. 20.23  Pseudoangiomatous stromal hyperplasia (PASH) of the breast in an 11-year-old female. (a) Longitudinal grayscale ultrasound image demonstrates a large, solid mass with well-defined borders and

homogeneous echotexture, similar in appearance to a giant fibroadenoma. (b) Longitudinal color Doppler ultrasound image reveals minimal peripheral vascularity

Since PASH is not a pre-malignant lesion, treatment is usually conservative with follow-up ultrasound studies to confirm lesion stability or, rarely, spontaneous regression. Surgery is indicated if there is rapid growth of the mass or if there is a strong family history of breast cancer [65, 66]. PASH will recur in up to 18% of patients if incompletely excised and can reappear in either the ipsilateral or contralateral breast [66–68].

Lactating Adenoma Lactating adenoma is a benign tumor that usually presents toward the end of pregnancy or during lactation as a result of hormonal fluctuations. Histologically it is characterized by ductal proliferation with a sparse stromal component [69, 70]. Lactating adenoma presents clinically as a palpable, painless mass in the third trimester of pregnancy.

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Ultrasound reveals a well-defined, wider-than-tall mass with lobulated borders that is hypoechoic and homogenous with posterior acoustic enhancement. Large tumors may be heterogeneous with spiculated, angulated margins and posterior acoustic shadowing suggestive of malignancy. Large cystic spaces can be present due to necrosis. Tiny hyperechoic foci within the masses may represent fat droplets and are often a key to the correct diagnosis [71]. Most lactating adenomas will involute spontaneously. However, lesions with ultrasound features concerning for malignancy or growing lesions should be surgically excised. Prognosis is excellent with recurrence being very rare.

Desmoid Tumor Desmoid tumor, also known as aggressive fibromatosis or desmoid-type fibromatosis, is a rare focally invasive lesion that does not metastasize. Histological features include interlacing bundles and fascicles of spindle cells with varying degrees of a

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surrounding collagen [72]. It most commonly occurs in the abdominal wall or extremities and accounts for only 0.2% of all breast tumors [73] and 3% of all solid tumors [74]. It is bilateral in 4% of patients [75]. Desmoid tumor of the breast is most often identified in women between the ages of 25 and 45. It can also develop in younger females and in males. Clinical associations include a history of silicone breast implants, chest irradiation and surgical trauma, as well as Gardner syndrome and familial adenomatous polyposis. Patients present with a firm, mobile, palpable mass with overlying skin thickening. If the mass is situated close to the nipple, nipple retraction may be seen. Ultrasound features of desmoid tumor mimic those of breast carcinoma, including a hypoechoic mass with lobulated, ill-defined borders and a thick, hyperechoic rim. Some masses may appear spiculated with posterior acoustic shadowing. MR imaging can be used to identify pectoralis muscle or chest wall invasion (Fig. 20.24). b

c

Fig. 20.24  Desmoid tumor of the breast in an 18-year-old female. (a) Longitudinal grayscale ultrasound image shows a well-defined, heterogeneous solid mass. (b) Sagittal T2-weighted magnetic resonance (MR) image reveals that the mass is hypointense to fluid but

hyperintense to the adjacent normal-appearing breast tissue, features suggestive of a cellular process. (c) Axial contrast-enhanced, T1-weighted, fat-suppressed MR image demonstrates avid enhancement of the mass

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Fig. 20.25  Granular cell tumor in a 19-year-old female. (a) Transverse grayscale ultrasound image demonstrates a hypoechoic mass (arrow-

head) with spiculated borders. (b) Transverse color Doppler ultrasound image reveals no significant internal flow

Desmoid tumors are locally invasive and have a high recurrence rate. Treatment is wide local excision with clear margins [75]. Aggressive and recurrent tumors may require additional treatment with chemotherapy and radiation.

Cystosarcoma Phyllodes Cystosarcoma phyllodes or phyllodes tumor is a rare fibroepithelial tumor [16, 27, 28, 82] and accounts for 0.3–1% of all breast masses [83]. Peak prevalence is in the fourth decade of life, although about 5% of phyllodes tumors occur in females less than 20 years of age. It is the most common primary breast malignancy in children and adolescents [16]. Histologically phyllodes tumor is characterized by a leaflike architecture resulting from enhanced intracanalicular growth, cleft-like spaces lined by epithelium, and hypercellular stroma [84]. It is categorized as benign, intermediate, or malignant, based on histological features. Although about 85% of cases in children are benign, some tumors can demonstrate invasion and recurrence. Rare fatalities have also been documented [2]. Clinically, patients present with a rapidly growing, mobile breast lump similar in presentation to a juvenile or giant fibroadenoma. A differentiating feature is that a phyllodes tumor tends to grow more rapidly. Patients with multiple masses or a strong family history of breast cancer should be evaluated for an underlying genetic predisposition [84]. Ultrasound features of phyllodes tumor are similar to those of a juvenile or giant fibroadenoma. There are well-defined, lobulated margins with heterogeneous low-level internal echoes. Small cysts or intralesional clefts may be identified (Fig. 20.26) [85]. Posterior acoustic shadowing can occur in up to 15% of cases with posterior acoustic enhancement in only 5%. Microcalcifications are rare. Pathological evaluation is required to distinguish between the benign and malignant forms of phyllodes tumor. Treatment is complete excision with wide margins to decrease the chance of recurrence which has been reported as being up to 40% [86]. Breast conservation is the goal in children, and mastec-

Granular Cell Tumor Granular cell tumor is a rare, benign lesion that usually occurs in the head and neck region, and infrequently in the breast, in approximately 5–6% of cases [76]. This tumor is most often seen in young, premenopausal African American females but has also been reported in women between the ages of 30 and 50 [77]. Granular cell tumor is of Schwann cell (perineural) origin. It presents as a firm, palpable mass close to the skin surface with associated skin retraction and can clinically mimic breast cancer [78]. The ultrasound appearance of granular cell tumor is nonspecific and varied, depending on the amount of reactive fibrosis, and ranges from hypo- to hyperechoic and well-­defined to ill-defined with spiculated margins (Fig. 20.25) [78]. Treatment is wide local excision with negative margins [79]. Incomplete excision may result in recurrence.

Malignant Tumors Malignant tumors of the breast are rare in children. Metastases to the breast are more common than primary breast neoplasms, and the most common neoplasms to metastasize to the breast are lymphoma, leukemia, and rhabdomyosarcoma [27]. Primary breast neoplasms account for fewer than 1% of all cancers in childhood and are more common in females [80, 81].

20 Breast

a

961

b

c

Fig. 20.26  Cystosarcoma phyllodes in two different patients. (a) Longitudinal grayscale ultrasound image in an 18-year-old female demonstrates a hypoechoic mass (arrow) with a well-defined capsule. (b) Longitudinal color Doppler ultrasound image shows markedly

increased flow throughout the mass. (c) Longitudinal grayscale extended field of view ultrasound image in a 20-year-old female demonstrates a well-circumscribed mass (calipers) with heterogeneous echotexture and a centrally located linear anechoic cleft (arrowhead)

tomy is only indicated for large tumors or in patients with small breasts [87]. Local recurrence usually occurs within the first few years after surgery, especially if the surgical margins were positive. Metastases develop in about 20% of tumors with malignant histology, particularly to the lungs [2].

and internal echoes are very concerning and should be biopsied (Fig. 20.27). Due to the rarity of primary breast carcinoma in children, there is no standard management approach. Most cases will be treated with surgical excision. Sentinel lymph node biopsy may be indicated for appropriate staging since axillary nodal metastases are identified in 20–30% of cases [2]. Secondary breast carcinomas are much more likely to occur in girls with a history of mantle cell radiation for Hodgkin lymphoma. The risk of a secondary breast cancer developing in this population is 75 times greater than in the general pediatric female population, and those irradiated between the ages of 10 and 16 years are at highest risk [93]. By 40  years of age, the incidence of breast cancer is 12–20% in patients with prior chest irradiation which is comparable to the incidence in patients with the BRACA 1 or 2 gene or in patients with hereditary cancer syndromes [16]. Therefore, thorough screening of Hodgkin lymphoma

Carcinoma Primary breast carcinoma is extremely unusual in children, with an incidence of 0.03 cases per 100,000 in those less than 20  years of age [16, 81]. Secretory carcinoma is the most common primary breast tumor in children and is less aggressive than infiltrating ductal carcinoma [28, 80, 81, 88, 89]. Primary breast carcinoma usually presents with an enlarging, painless, and fixed mass. Ultrasound features of a primary breast carcinoma are inconsistent and nonspecific [90–92]. Masses may appear hypoechoic with ill-defined or microlobulated margins. Lesions that are taller than wide with posterior acoustic shadowing

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Fig. 20.27  Invasive ductal breast carcinoma in a 17-year-old female. (a) Transverse and (b) longitudinal grayscale ultrasound images depict a large, heterogeneous breast mass with irregular borders. (c) Transverse color Doppler ultrasound image of the mass shows internal vascularity.

(d) Transverse color Doppler ultrasound image of the ipsilateral axilla reveals abnormally enlarged lymph nodes with prominent vascularity consistent with metastases

survivors with both mammography and MR imaging should begin at either 25 years of age or 8 to 10 years following completion of radiation treatment [24, 94].

cutaneous edema. Interestingly, up to 33% of angiosarcomas may not be detected on mammography [99, 101]. Angiosarcoma is treated by surgical excision. There is a low 5-year survival rate with the lungs the most frequent site of metastasis.

Angiosarcoma Angiosarcoma (also known as malignant hemangioendothelioma) is an aggressive spindle cell tumor that accounts for 0.04% of all breast malignancies with an average age at diagnosis of 40 years [95–100]. Primary angiosarcoma of the breast rarely occurs in children, although a low-grade form has been observed in the second decade of life and is most common in patients with a prior history of chest irradiation [97, 98]. Ultrasound findings include a large, ovoid, well-­circumscribed mass that may be hyper- or hypoechoic with internal heterogeneity or hemorrhage. Posterior acoustic enhancement is rarely seen, and posterior acoustic shadowing is absent. Color Doppler demonstrates increased vascularity with associated skin or sub-

Hematologic Malignancies Primary lymphoma of the breast is extremely rare. However, lymphoma and leukemia are the most common hematologic malignancies to metastasize to the breast [12, 46]. Burkitt lymphoma, a form of non-Hodgkin lymphoma, is the usual etiology [27]. Patients with metastases due to lymphoma or leukemia usually present with painful, enlarging, and bilateral breast masses that may be single or multiple. Associated axillary lymphadenopathy or chest wall invasion is common. Ultrasound demonstrates hypoechoic, lobulated masses with either well-defined or ill-defined margins. They may contain

20 Breast

a

R c

963

b

L d

Fig. 20.28  Juvenile myelomonocytic leukemia of the breast in a 9-year-old female. Longitudinal grayscale ultrasound images of the (a) right (R) and (b) left (L) breasts depict irregular, lobulated, heterogeneous masses

with  ill-defined borders. (c) Axial and (d) sagittal contrast-enhanced, T1-weighted, fat-suppressed MR images of both breasts (c) and the left breast (d) demonstrate diffusely enhancing masses

internal echoes with p­ osterior acoustic shadowing. Color Doppler may demonstrate internal vascularity (Figs. 20.28 and 20.29). Diagnosis is made by either fine needle aspiration or core biopsy. The prognosis associated with hematological malignancies metastatic to the breast is dismal.

ents as multiple hypoechoic masses. Hematologic malignancies are described in the prior section of this chapter. Less common tumors that can metastasize to the breast include sarcomas, especially Ewing sarcoma, primitive neuroendocrine tumor, and melanoma. Metastases may be single or multiple, although a single, enlarging mass is the most common presentation. By ultrasound, breast metastases are usually hypoechoic and heterogeneous with irregular borders and internal hyperechoic foci (Fig. 20.30) [2, 103–105]. Posterior acoustic shadowing and associated axillary lymphadenopathy are common. Chest wall invasion may occur with lymphoma. Any enlarging breast mass in a patient with a known extra-mammary primary malignancy must be biopsied to exclude metastatic disease.

Metastases Metastatic tumors are the most common neoplasm occurring in the pediatric breast [81]. Breast metastases occur much more often in females than in males, most frequently from rhabdomyosarcoma, neuroblastoma, and hematologic malignancies [16]. The most common malignancy to metastasize to the breast is the alveolar sub-­type of rhabdomyosarcoma with breast metastases seen in up to 6% of children [102]. Neuro­ blastoma also frequently metastasizes to the breast and pres-

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a

Fig. 20.29  Malignant B-cell lymphoma metastatic to the breast in a 19-year-old female. (a) Transverse grayscale ultrasound image shows a

a

b

round, heterogeneous mass (calipers). (b) Transverse color Doppler ultrasound image reveals internal flow

b

Fig. 20.30  Metastatic liposarcoma to the right breast in a 13-year-old female with a primary tumor of the right shoulder. (a, b) Transverse grayscale ultrasound images of the right breast demonstrate two sepa-

rate nodules of metastatic disease. The nodule in (a) contains both cystic (arrowhead) and solid components while the nodule in (b) is entirely solid

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Index

Page numbers followed by f indicate figures; t, tables A AAST. See American Association for the Surgery of Trauma Abscess(es) abdominal, 339, 494 adrenal, bacterial, 595–596 amebic, 378 bacterial, 375–376, 494 brain, 86–87, 88f breast, 949, 950f epidural, 120 epididymal, 645 fungal, 378, 494–497, 495f, 496f of kidneys acute pyelonephritis and, 769–770, 770f after kidney transplantation, 795–797, 797f liver fungal, 378, 378f complication of bile duct stricture, 472 complication of Caroli disease, 459 after liver transplantation, 423–425, 424f–425f parasitic, 378–380, 379f pyogenic, 375–376, 376f–377f pelvic, 339 peritoneal, 539f prostatic, 678 pulmonary, 184–185, 184f–186f retropharyngeal, 145f, 730 scrotal, 645–646, 646f soft tissue, 839–840, 840f splenic, 494, 494f, 497f, 501 subperiosteal, 851, 851f, 852 testicular, 644–645 Abdominal abscess(es), 339, 494 Accessory breast tissue, 947, 947f Accessory pancreatic lobe, 567, 569 Accessory renal artery, 736–737, 737f Accessory spleen, 487–490, 489f Acinar cell carcinoma, 166–167, 167f, 584–585 ACKD. See Acquired cystic kidney disease Acoustic impedance, 4–5, 5f, 12, 38, 175–176, 200 Acoustic radiation force impulse (ARFI) imaging, 34f, 34–35 and liver, 359, 359f, 359t Acoustic(s) acoustic impedance, 4, 5f, 12, 38, 175–176, 200 attenuation, 7–8, 8f compression, 3 distance measurement, 8–11 frame rate, 10–11 frame time, 11 frequency, 2, 2f frequency spectrum, 9, 9f pulse repetition frequency, 9, 10f, 43f, 334, 900

pulse repetition period, 9, 10f rarefaction, 3 reflection, 4–7, 5f, 6f specular reflection, 4–6 refraction, 7, 7f scattering, 4, 6, 5f–6f sound propagation, 2–4, 2f–3f speckle artifact, 6, 6f–7f wavelength, 2, 2f Acquired cystic kidney disease (ACKD), 779, 779f Acquired immune deficiency syndrome (AIDS), 472, 501, 502f, 515, 536, 609, 621, 772 ACR. See American College of Radiology Acute ischemic stroke (AIS), 78, 80f, 81f, 905–906 Acute kidney injury (AKI), 784–786, 786f Acute lymphoblastic leukemia, 261, 520f, 572f, 620, 668, 813 Acute pyelonephritis, 768–769, 769f Acute scrotal pain, 639, 649. See also Epididymitis; Epididymoorchitis; Testicular torsion Acute suppurative parotitis, 164 Acute suppurative thyroiditis, 159, 159f Acute tubular necrosis (ATN), 784, 791–792, 792f Adenoid cystic carcinoma, 167, 167f Adenomatoid tumor(s), 668, 672 Adenomyomatosis, 450–451, 451f Adenomyosis, 718–719, 719f Adnexa. See Female genital tract Adnexal masses. See Female genital tract Adnexal torsion. See Female genital tract ADPKD. See Autosomal dominant polycystic kidney disease Adrenal gland(s) adrenal cyst idiopathic adrenal cyst, 594, 594f adrenal hemorrhage, 596–597, 596f adrenal heterotopia, 593 adrenocortical tumors adrenocortical adenoma and carcinoma, 597, 597f–598f anatomic variants discoid adrenal gland, 590–591, 591f congenital anomalies adrenal rests, testicular, 592, 592f congenital adrenal agenesis, 591 fusion abnormalities circumrenal adrenal gland, 591–592 horseshoe adrenal gland, 592, 592f genetic disorders congenital adrenal hyperplasia, 593, 593f congenital lipoid adrenal hyperplasia, 593 Wolman disease, 594 hemangioma, infantile of adrenal, 608 infection

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970 Adrenal gland(s) (cont.) abscess, 595–596 congenital Herpes simplex viral infection, 595 granulomatous infection, 595, 595f xanthogranulomatous adrenalitis, 595 leiomyoma, 609 lymphoma, 609 metastases, 609 myelolipoma, 607–608 neural crest tumors ganglioneuroblastoma, 599–600, 600f ganglioneuroma, 598–599, 599f neuroblastoma, 601–602, 601t, 602f–605f, 606 fetal neuroblastoma, 601–602 normal anatomy, 589, 591f normal development, 589, 590f pheochromocytoma, 606–607, 606f–607f and hereditary syndromes, 606 technique imaging approaches, 588–589, 589f patient positioning, 588 ultrasound transducer selection, 588 teratoma, 608, 608f Adrenal rests, intratesticular, 592, 592f, 593, 660, 661f AFP. See Alpha-fetoprotein Aggressive fibromatosis, 548–549, 959–960, 959f Agyria. See Lissencephaly AIDS. See Acquired immune deficiency syndrome AIDS cholangiopathy, 472 AIS. See Acute ischemic stroke AKI. See Acute kidney injury Alagille syndrome, 372, 465, 468, 468f, 469 ALARA. See As low as reasonably achievable Aliasing in abdominal vascular imaging, 417f, 421f, 789 in color Doppler ultrasound, 42–43, 43f–44f Alobar holoprosencephaly, 64. See also Holoprosencephaly Alpha-fetoprotein (AFP) anencephaly and, 63 congenital hemangioma and, 389 gastric teratoma and, 300 liver masses and, 388t pancreatoblastoma and, 581 yolk sac tumor and, 663 Amebic abscess(es), 378 Amenorrhea, 683, 692–693, 698, 700–701, 715, 724 American Association for the Surgery of Trauma (AAST) and renal trauma, 802 and splenic trauma, 508–509, 510f American College of Radiology (ACR) and ALARA principle, 331 and hip ultrasound screening, 873 and lower extremity vein evaluation, 919 and TI-RADS, 153 Amplitude (A)-mode imaging, 14, 14f. See also Image display Anatomically related Doppler artifacts blooming artifact, 46–47, 46f spectral mirror image artifact, 44–45, 45f tissue vibration artifact, 45, 45f twinkle artifact, 45–46, 46f Anencephaly, 63, 63f, 64f Aneurysm(s) of abdominal aorta, 613f, 929–931,930f of carotid artery, 905 clinical and ultrasound features of, 918t of iliac arteries, 929

Index intracranial, 468, 775 and Kawasaki disease, 929–931 mycotic, 916, 931 of peripheral arteries, 916 and renal angiomyolipoma, 804 of renal artery, 779 and Takayasu arteritis, 613f, 903–904 and tissue vibration artifact, 45 and vein of Galen malformation, 90, 91f venous, 908 Angiosarcoma of bladder, 823–824 of breast, 962 of liver, 402–403 of spleen, 520–521 Anisotropy of muscles, 837 of tendons, 838, 838f, 867, 869f, 879 of peripheral nerves, 838f, 867 Ankle and hindfoot apophyseal avulsion injuries, 889, 889f calcaneal apophysis, 888f, 889 imaging approaches calcaneal apophysis, 888f, 889 joint effusion, 888–889, 888f joint effusion, 888–889, 889f normal anatomy, 887, 887f patient positioning, 888–888, 888f Anorchidism, 636–637 Anorectal malformations, 248, 335–336, 336f–337f, 702, 760 Anterior horn width, 92, 92f Antral web, 292. See also Gastric diaphragm Aorta aneurysm, 929–931, 930f dissection, 931, 931f normal anatomy, 927, 928f–929f normal development, 927 stenosis, 928–929, 930f thrombosis, 927–928, 929f Appendicolith, 539f, 612, 612f. See also Acute appendicitis; Fecalith Appendix acute appendicitis, 323, 331–333, 331f–332f, 331t, 541, 767 appendicolith, 539f, 612, 612f fecalith, 331, 332f benign masses mucocele, 333 cystic fibrosis, 332, 332f malignant tumors carcinoid, 333 lymphoma, 333–334, 333f normal anatomy, 330, 330f normal development, 291f, 330 technique imaging approaches, 330 patient positioning, 330 ultrasound transducer selection, 330 Arcuate uterus, 691–692, 691t ARFI. See Acoustic radiation force impulse imaging ARPKD. See Autosomal recessive polycystic kidney disease Array transducer, 10f, 12f, 19–22, 20f–22f, 24, 26, 26f, 52, 61, 92–93, 174, 196, 239–240, 271, 274f, 284, 356, 434, 482, 539, 564, 588, 629, 683, 686f, 910, 918, 941 Arteriovenous fistula (AVF) of dura, 90 of extremity vessels, 916–918 of GI tract, 327

Index of kidney, 783–784, 785f transplant biopsy and, 789, 791f of musculoskeletal system, 892, 894, 894f of neck, 140, 142f post-traumatic, 916–918, 918f, 918t and tissue vibration artifact, 45, 45f Arteriovenous malformation(s) (AVM) of musculoskeletal system, 892, 894, 894f of neck, 140–141 of scrotum, 671 vein of Galen malformation, 90, 91f Artery(ies). See specific arteries Arthritis. See also Rheumatic disorders septic, 850f, 851, 851f, 854, 854f, 877 Artifacts contrast agent blooming, 47 high-intensity transient signals, 47 systolic peak velocity increase, 47 Doppler, anatomically related spectral mirror image, 44–45, 45f blooming, 46, 46f tissue vibration, 45, 45f twinkling, 45–46, 46f Doppler, technically related absent Doppler signal, 42–43, 42f aliasing (wraparound), 43, 43f, 44f color Doppler noise, 43–44 flow directional abnormalities, 44, 44f inappropriate Doppler settings, 42–43, 42f grayscale comet-tail, 38, 39f enhancement, 39–40, 40f mirror image, 37, 37f partial volume, 40–41, 41f refraction, 37, 38f reverberation, 38, 38f, 39, 39f ring-down, 39 shadowing attenuation, 40–41, 40f–41f side lobe, 39, 39f three dimensional ultrasound, 47 Ascites, 528–530, 529f–530f Budd-Chiari syndrome, 383–384, 383f eosinophilic gastroenteritis and, 297–298, 320–321 biliary tract trauma and, 472–473 chemical peritonitis and, 537, 538f chylous, 531–532, 531f kaposiform lymphangiomatosis and, 513 lymphatic malformation, intra-abdominal, and, 542 pulmonary lymphangiectasia and, 188 cirrhosis and, 374–375, 375f Crohn disease and, 339 drainage of, 530 graft-versus-host disease of GI tract, 322–323, 323f hemolytic-uremic syndrome and, 343 hemoperitoneum, 530, 531f Henoch–Schönlein purpura and, 319–320, 320f after liver transplantation, 408t, 412 loculated, 529, 530f malpositioned umbilical venous catheter and, 380–382, 381f meconium ileus and, 311–312 meconium peritonitis and, 312–313, 653 mesenteric visualization and, 526, 527f–528f ovarian tumors and, 708, 710 Meigs syndrome, 705t, 710

971 neutropenic colitis and, 342–343 pancreatitis, necrotizing, and, 575f passive venous congestion of liver and, 386, 386f peritoneal tumor and, 551–555, 553f–555f portal hypertension, 375, 382, 508 pseudomembranous colitis and, 341–342 sclerosing encapsulating peritonitis and, 537–539, 538f serum-ascites-albumin gradient, 529, 529t sinusoidal obstruction syndrome, 384–385, 384f splenic rupture and, 520 tuberculous peritonitis and, 497 urine, 532, 532f, 746, 764, 794, 802f vascular anomalies of GI tract and, 327 viral gastroenteritis and, 316 Atelectasis, 183, 190, 200–201, 207f, 214f, 278 Atlanta classification, revised, of acute pancreatitis, 572 ATN. See Acute tubular necrosis Attenuation, 7–8, 8f, 13, 18, 24 ultrasound artifacts and, 37, 39–40, 40f–41f Augmentation cystoplasty, 824, 825f Autosomal dominant polycystic kidney disease (ADPKD), 369, 571, 571f, 775–778 Autosomal recessive polycystic kidney disease (ARPKD), 775, 775f Avascular necrosis (AVN), 873, 875 AVF. See Arteriovenous fistula AVM. See Arteriovenous malformation(s) AVN. See Avascular necrosis B Bacterial abscess(es), 375–376, 494 Bacterial infection, 86, 88, 144, 164, 201, 230, 254, 316, 375, 494, 501, 611, 773, 839 Bacterial parotitis, 164–165, 165f Baker (popliteal) cyst, 881, 881f Bartholin cyst, 721 Basal ganglia, 58–59, 63, 77, 79f, 85 Beam width artifact, 40–41 Beckwith-Wiedemann syndrome adrenocortical tumors and, 597, 597f hepatoblastoma and, 397 nephrogenic rests and, 810 pancreas and, 571 pancreatoblastoma and 631 pediatric renal cell carcinoma and, 810 rhabdomyosarcoma and, 551 Wilms’ tumor and, 806 Bell clapper deformity, 639, 639f, 640 Benign external hydrocephalus, 92–93, 92f Benign macrocrania of infancy. See Benign external hydrocephalus β-hCG. See Beta-human chorionic gonadotropin Beta-human chorionic gonadotropin gastric teratoma and, 300 ovarian tumors and, 705t, 708 testicular seminoma and, 663 Bezoars. See Gastric bezoar B-flow, 32 Bile plug syndrome, 463, 470–471, 470f Biliary atresia, 359, 368, 372, 374, 408, 433, 436, 437f, 458, 462–463, 463f, 464f, 465, 466f, 469, 475f, 509f Biliary dyskinesia, 447–448 Biliary tract anatomic variants, 456–457, 457f Caroli disease, 459–460, 462f congenital anomalies

972 Biliary tract (cont.) choledochal cysts, 457–459, 458f–461f Todani classification, 457, 458f normal anatomy, 455–456, 455f–456f normal development, 455 obstruction AIDS cholangiopathy, 472 Alagille syndrome, 465, 468, 468f, 469 bile duct stricture, 472 biliary atresia, 462–463, 462f–464f Kasai classification of, 463f Kasai procedure, treatment for, 463 Byler disease, 469 choledocholithiasis, 469–470, 469f inspissated bile syndrome, 470–471, 470f Mirizzi syndrome, 471–472 neonatal hepatitis syndrome, 443t, 463, 465, 467f sclerosing cholangitis, 471, 471f spontaneous perforation, of extrahepatic bile ducts, 472 trauma, 472–473 tumors benign masses bile duct adenoma, 473 granular cell tumor, 473 malignant bile duct tumors cholangiocarcinoma, 474 metastases, 474–475, 475f neuroendocrine tumor, 474, 475f rhabdomyosarcoma, 473–474, 474f Biloma after liver transplantation, 408t, 423–425, 424f–425f after spontaneous perforation of extrahepatic bile ducts, 472 after trauma, 453, 533, 534f Bladder agenesis, 762, 763f angiosarcoma, 823–824 bladder diverticula, 758, 759f bladder ears, 740, 740f bladder exstrophy, 759–760, 760f cloacal exstrophy, 759–760 cloacal malformation, 760–761, 761f duplication, 761–762, 762f fibroepithelial polyp, 818, 819f inflammatory myofibroblastic tumor, 818–819, 819f leiomyoma, 819 leiomyosarcoma, 823 lymphatic malformation, 816, 817f megacystitis-microcolon-intestinal hypoperistalsis syndrome, 763 nephrogenic adenoma, 820–821, 822f neurofibroma, 819, 820f neurogenic bladder, 749f, 754, 767, 767f, 800, 824 normal anatomy, 738–740 papillary urothelial neoplasm of low malignant potential, 818 paraganglioma, 819–820, 821f prune-belly syndrome, 762–763, 763f rhabdomyosarcoma, 821–822, 822f transitional cell carcinoma, 822–823, 823f trauma, 802, 802f, 803 urinary diversion, 824–825, 825f urothelial papillomas, 818 venous malformation, 816, 817f, 818 Blooming artifact, 46–47, 46f, 73f Blue rubber bleb nevus syndrome (BRBNS), 250, 327, 515f, 542, 545f of gastrointestinal tract, 250, 327 of mesentery, 545f of peritoneal cavity, 542

Index of spleen, 515f Blunt abdominal trauma, 281, 379, 380f, 453, 454f, 482, 508, 577, 597, 781, 801 B-mode flow imaging. See B-flow B-mode imaging, 14, 21, 27–30, 32–35, 47–48, 174, 196, 199, 200f, 272, 278 Bochdalek hernia, 274, 274f, 275f, 276f Bone(s)/Cartilage congenital rib anomalies, 849, 849f imaging approaches, 847–848, 848f normal anatomy, 847–848, 848f osteomyelitis, 850–851, 850f–851f trauma classic metaphyseal lesion, 852, 853f epiphyseal separation, 851–852, 852f tumors osteochondroma, 849f, 853–854 BPBP. See Brachial plexus birth palsy Brachial plexus birth palsy (BPBP), 858–859, 858f–859f Brain benign external hydrocephalus, 92–93, 93f congenital anomalies dorsal induction disorders anencephaly, 63, 63f Chiari malformation(s), 61–63, 62f, 65, 113, 121 Chiari I, 61, 62f Chiari II, 61–63, 62f and myelomeningocele, 62, 62f hydranencephaly, 63, 64f migration disorders gray matter heterotopia, 68, 69f lissencephaly (agyria), 68 post-migration disorders polymicrogyria, 67–68, 85 schizencephaly, 58t, 64, 67–69, 70f ventral induction disorders corpus callosum agenesis, 65–67, 66f callosal dysgenesis, 65, 67f lipoma of, 67, 67f Dandy-Walker syndrome, 58t, 65, 67–68, 67f holoprosencephaly, 63–64, 64f alobar, 64, 64f lobar, 64 semilobar, 64 septo-optic (pituitary) dysplasia, 64–65, 65f extracranial birth trauma, 95, 95f cephalohematoma, 93, 95, 95f subgaleal hematoma, 95, 95f hydrocephalus, 90, 92, 92f hypoxic-ischemic injury, 75–84 infectious disorders bacterial infections, 86–88, 87f–88f fungal infections, 88 viral infections, 84–86, 85f–86f intracranial hemorrhage, 70–75 neoplasms, of neonatal/infant brain and ventricle, 88–89, 89f neuronal proliferation disorders, 68 hemimegalencephaly, 68 normal anatomy basal ganglia, 58–59, 59f cerebral cortex, 58, 59f cisterna magna, 60–61, 61f connatal cysts, 59–60, 60f extra-axial fluid spaces, 61 forebrain structures, 57–58

Index hindbrain structures, 57–58 mega cisterna magna, 60–61, 61f midbrain structures, 57–58 thalami/thalamus, 59, 59f ventricles, 59–60, 59f–60f normal development, 57, 58f, 58t cerebral cortical formation, 57 primitive streak, 57 scalp masses (see Scalp masses) suture evaluation craniosynostosis, 61, 97–99, 98f plagiocephaly, positional, 97, 99 technique imaging approaches, 52–53, 53f–57f patient positioning, 52 ultrasound transducer selection, 52 vascular disorders high-flow malformations, 89–90, 91f vein of Galen malformation, 90, 91f low-flow malformations, 89–90 Branchial cleft cyst(s), 133–134, 134f, 135f, 163 BRBNS. See Blue rubber bleb nevus syndrome Breast accessory breast tissue, 947, 947f benign tumors, 955t desmoid, 959–960, 959f fibroadenoma, 955, 956f granular cell, 960, 960f hemangioma, 955–956, 957f intraductal papilloma, 956, 957f juvenile papillomatosis, 957, 958f lactating adenoma, 958–959 pseudoangiomatous stromal hyperplasia, 957–958, 958f congenital anomalies amastia, 947 amazia, 947 athelia, 947 hypomastia, 947 Poland syndrome, 947 polymastia, 947 polythelia, 947 developmental anomalies gynecomastia, 948–949, 949f juvenile hypertrophy, 948 premature thelarche, 948, 948f imaging field of view, 941–942 inflammatory lesions abscess, 949–950, 950f mastitis, 949, 950f malignant tumors, 955, 955t angiosarcoma, 962 carcinoma, 961–962, 962f and prior mantle radiation for Hodgkin lymphoma, 961 cystosarcoma phyllodes, 960–961, 961f hematologic malignancies, 962–963, 963f–964f metastases, 963, 964f non-neoplastic lesions fat necrosis, 953–954 fibrocystic disease, 951–952, 952f galactocele, 952–953, 953f hematoma, 953, 953f intramammary lymph node, 954, 954f lymphatic malformation, 955 mammary duct ectasia, 950, 951f retroareolar cysts (obstructed glands of Montgomery), 950–951, 951f

973 vascular malformation(s), 954 venous malformation, 954–955 normal anatomy, 942f, 946–947, 946f normal development, 942–943, 943f–945f, 944t Tanner staging, 943, 944t, 945f–946f, 946–947 technique imaging approaches, 941–942 patient positioning, 941 ultrasound transducer selection, 941 Bronchogenic cyst(s), 136, 179, 190, 229, 229f, 279, 285 Bronchopulmonary sequestration extralobar bronchopulmonary sequestration, 182 hybrid congenital lung anomalies, 183 intralobar bronchopulmonary sequestration, 181–182, 182f Budd-Chiari syndrome, 383, 383f Burkitt lymphoma breast, 962 chest wall, 261f Epstein-Barr viral infection and, 498 GI tract, 301, 303f, 329f, 329–330, 333, 345, 346f kidney, 814f mediastinum, 226 neutropenic colitis and, 342 ovary, 711, 711f pancreas, 585, 586f peritoneal cavity, 551, 552f testicle, 668 Byler disease, 469 C CAH. See Congenital adrenal hyperplasia Callosal agenesis, 66 Campylobacter, 316, 340 Canal of Nuck disorders differential diagnosis, 725 hernias, 726, 726f hydrocele, 725–726, 725f Capillary malformation–arteriovenous malformation (CM-AVM) syndrome, 140 Carcinoid tumor, 323, 333, 669 Carcinoma acinar cell, 166–167, 167f, 584–585 adenoid cystic, 167, 167f adrenocortical adenoma and, 597, 597f–598f clear cell adenocarcinoma, 722–723 embryonal, 663–664, 706 fibrolamellar hepatocellular, 401, 401f hepatocellular, 400, 400f mucoepidermoid, 166, 166f primary gastric adenocarcinoma, 303 renal cell, 778–779, 804, 810–811 renal medullary, 812 transitional cell, 822–823, 823f urothelial, 818, 822–823, 823f Cardiophrenic angle masses lymphadenopathy, 235–236, 236f pericardial cyst, 235, 235f Caroli disease, 373f, 457, 458f, 459–460, 462f, 469, 474 Cartilage. See Bones Castleman disease, 549–550, 549f CAT. See Cutaneovisceral angiomatosis with thrombocytopenia Cat-scratch disease of cervical lymph nodes, 146, 146f of spleen, 494

974 Cauda equina imaging, 104–105, 105f, 107f positional nerve root clumping (“pseudomass”), 110 and tethered cord, 116 Caudal regression syndrome, 103, 110, 118–119, 119f Cavitation. See Nonthermal bioeffects Cellulitis, 146, 255, 255f–256f, 838–839, 839f, 949 Cephalocele, 67, 93–94 Cephalohematoma, 93, 95, 95f Cerebellar hemorrhage, 53, 72, 74f and ECMO, 53, 72 Cerebral cortex, 58, 68, 74–75, 77 Cerebrospinal fluid (CSF) cerebrospinal fluid-containing defects, 116 cerebrospinal fluid pseudocyst, 532–533, 533f Cervical adenitis, 144–145, 144f. See also Lymphadenopathy Cervical extension of normal mediastinal thymus, 138 Cervical teratoma, 136–137 Cervical thymic cyst, 134 Cervix atresia, 698 benign tumors nabothian cyst, 719, 719f ectopic pregnancy and, 715 malignant tumors clear cell adenocarcinoma, 723 rhabdomyosarcoma, 720, 720f, 722 normal anatomy, 689 normal development, 689 PID and, 716, 716f CEUS. See Contrast-enhanced ultrasound Chest wall benign neoplasms lipoma, 257–258, 257f–258f mesenchymal hamartoma, 257–258 congenital anomalies vascular tumors and malformations clinical and ultrasound features, 248, 248t hemangioma, 248–249, 249f LUMBAR syndrome, 248 PHACE syndrome, 248 ISSVA classification, 247–248, 248t lymphatic malformation, 250, 250f–251f venous malformation, 250–251, 250f foreign bodies, 265–266, 265f–266f infectious disorders abscess, 256, 256f cellulitis, 255, 255f lymphoma, 261–262 malignant neoplasms Ewing sarcoma, 259–260, 260f lymphoma, 261f, 261–262f metastases, 262, 262f osteosarcoma, 260–261, 260f rhabdomyosarcoma, 258–259, 259f neoplastic disorders, 256–262 normal anatomy musculature, 244–246, 245f–246f thoracic skeleton, 243–244, 244f ultrasound appearance, 246–247, 246f–247f normal development soft tissues, 242–243, 243f thoracic skeleton, 241–242, 242f–243f osseous and cartilaginous lesions costochondral junction, asymmetric cartilaginous, 252–253, 253f–254f

Index enlarged rib end, 253, 254f, 255 osteochondroma/exostosis, 251–252, 252f technique contrast-enhanced ultrasound, 241 imaging approaches annotations, 241 protocols, 241 patient positioning, 239 ultrasound transducer selection, 239–240 traumatic disorders hematoma, 262–264, 263f rib fractures, 264–265, 264f Chiari malformation(s), 61–63, 62f, 65, 113, 121 Chiari I, 61, 62f Chiari II, 61–63, 62f and myelomeningocele, 62, 62f Child abuse. See also Non-accidental trauma; Trauma distal humeral epiphyseal separation and, 865f portal venous gas and, 386 rib fracture and, 264 Childhood ILD, 185 Children’s Oncology Group (COG) and neuroblastoma management, 233, 586 and Wilms’ tumor management, 810 Chimney phenomenon, 240t, 264 Chocolate cysts, 705 Cholangiocarcinoma, 458–459, 474 Cholecystitis acute acalculous, 447, 448f acute calculous, 444–447, 445f–446f gangrenous, 446, 446f chronic, 449, 449f porcelain gallbladder, 449, 450f Choledochal cyst(s), 457–459, 570 Choledocholithiasis, 441, 469, 469f, 470, 472 Cholelithiasis, 433, 438, 440–442, 441f–442f, 445, 447, 449, 471 Cholesterol polyp(s), 450–452, 451t, 452f Choriocarcinoma, 662, 664, 706, 708–709, 948 Choroid plexus tumors, 88–89, 89f Chronic granulomatous disease, 298, 298f, 494, 649, 678 Chronic kidney disease (CKD), 731, 768t, 781, 785–786, 882 Chylous effusion/chylothorax, 206–207 Circumcaval ureter, 752. See also Retrocaval ureter Cirrhosis biliary, 438f, 443t, 459, 462, 466f, 468–469, 471 of liver, 356t, 359f, 359t, 366, 371–372, 374–375, 375f, 382, 382t, 487t and ascites, 529f, 529t and Budd-Chiari syndrome, 383, 383t compared to chronic hepatosplenic schistosomiasis, 500 hyposplenia and, 492 and passive venous congestion, 386 and portal hypertension, 508, 509f and primary bacterial peritonitis, 536 Cisterna magna, 55f, 57f, 60–61, 61f–62f, 67, 90 CKD. See Chronic kidney disease Classic metaphyseal lesion (CML), 852, 853f Clear cell sarcoma, 811–812, 812f Cloacal malformation(s), 702, 761 Cloacal exstrophy, 759 exstrophy-epispadias complex and, 758 terminal myelocystocele and, 116 Closed defects complex, of spine, 114–116 simple, of spine, 113–114 CML. See Classic metaphyseal lesion

Index Coccyx dysmorphic, 110, 111f Colloid cysts, 152, 152f Colon benign masses duplication cyst, 345 juvenile polyp, 344–345, 345f and juvenile polyposis syndrome, 345 congenital anomalies anorectal malformations, 335–336, 336f–337f and association with VACTERL, 335 malignant tumors adenocarcinoma, 345, 347, 347f lymphoma, 345, 346f normal anatomy, 335 normal development, 291f, 334–335, 733f technique imaging approaches, 334 patient positioning, 334 ultrasound transducer selection, 334, 334f wall thickening Crohn disease, 339–340, 339f cystic fibrosis, 343 hemolytic–uremic syndrome, 343, 344f infectious colitis, 340–341, 340f–341f necrotizing enterocolitis, 337, 338f neutropenic colitis, 342–343, 342f pseudomembranous colitis, 341–342, 341f ulcerative colitis, 337–338, 338f Color Doppler ultrasound, 27, 31, 31f. See also Doppler ultrasound; Ultrasound artifacts; Ultrasound safety and brain neoplasms, 88 and bronchopulmonary sequestration, 181 differentiation from neuroblastoma, 233 and congenital portosystemic shunts, of liver, 371f and cortical veins of brain, 61, 93f and Crohn disease, 317, 318f differentiation of empyema from lung abscess, 185f and epididymo-orchitis, 644, 645f and infantile hemangioma of breast, 955–956, 957f and pleural effusion, 202 in pneumonia, 177f and portal vein thrombosis, 382, 418, 419f compared to power Doppler, 32 and “ring of fire” sign, in ectopic pregnancy, 715, 715f and soft tissue vascular anomalies, 890, 891f–892f, 893, 894f TCD, 82–84, 83f–84f, 83t in testicular torsion, 641, 641f and “thyroid inferno”, 159–160, 160f and tissue vibration artifact, 45, 784, 785f and twinkling artifact, for diagnosis of urinary tract stones, 799–800, 801f and ureteral jets, 738, 739f and varicocele, 659–660, 659f–660f and vascular chest wall lesions, 247–251, 248t, 249f–251f and vascular neck masses, 138, 140, 141f–144f, 166 and vascular scalp lesions, 95–96, 97f in vein of Galen malformation, 91f and venous malformation of bladder, 816, 817f in venous sinus thrombosis, 81, 82f and “whirlpool” sign of midgut volvulus, 310, 311f and “yin-yang” pattern of pseudoaneurysm, 918t of hepatic artery, in liver transplantation, 408, 418, 418f of peripheral arteries, 916, 917f of renal artery, 781, 783f after renal transplant biopsy, 789, 791f

975 Comet-tail artifact, 38 Common carotid artery (CCA), 148f, 900, 900f Compression. See also Elastography; Elastography imaging of abscess, 256, 256f of appendix, 330, 331t of arteriovenous fistula, 917 of breast, imaging approaches, 942 of colon, 334 of extremity veins, 919–920, 925, 926f extrinsic, of ureter, 767 of soundwave, 3, 3f, 4 Congenital adrenal hyperplasia (CAH) adrenal rests in, 592, 592f, 593, 593f, 660–661, 661f, 662t, 670 and disorders of sex development, 702, 702f and myelolipoma, 607 Congenital anomalies, of breast amastia, 947 amazia, 947 athelia, 947 hypomastia, 947 Poland syndrome, 947 polymastia, 947 polythelia, 947 Congenital benign cystic neck masses branchial cleft cyst, 133–134, 134f, 135f cervical thymic cyst, 134–136, 135f dermoid cyst, 136–137, 137f foregut duplication cyst, 136, 136f teratoma, 136–137, 137f thyroglossal duct cyst, 133, 133f–134f Congenital benign solid neck masses cervical extension of normal mediastinal thymus, 138, 138f ectopic thymus, 138, 138f fibromatosis colli, 138, 139f Congenital diaphragmatic anomalies, 274–278 Congenital diaphragmatic eventration, 277 Congenital diaphragmatic hernia (CDH), 274, 274f, 274t, 275f, 294, 310, 438f, 490, 638 Congenital goiter, 158f Congenital hemangioma non-involuting congenital hemangioma of liver, 388t, 389 of skin/subcutaneous tissues, 248–249, 248t, 890, 890t partially involuting congenital hemangioma of liver, 388t, 389, 390f of skin, subcutaneous tissues 248–249, 248t, 890, 891f peritoneal cavity, 517 rapidly involuting congenital hemangioma of liver, 388t, 389, 389f of skin/subcutaneous tissues, 248–249, 248t, 890, 891f Congenital knee dislocation, 882–883, 883f Congenital lobar hyperinflation, 178, 178f Congenital megacalyces, 748, 749f Congenital non-vascular neck masses. See Congenital benign cystic neck masses; Congenital benign solid neck masses Congenital patellar dislocation, 883, 884f Congenital pulmonary airway malformation (CPAM), 180, 180t, 181f Congenital ureterovesical junction obstruction (UVJO), 751, 751f Congenital vascular neck masses congenital hemangioma, 138 vascular malformations, 140 arteriovenous fistula, 140, 142f arteriovenous malformation, 140, 141f lymphatic malformation, 140, 144, 144f venous malformation, 140, 143f

976 Connatal cysts, 59–60, 60f Constant-range (C) mode, 14. See also Image display Continuous wave (CW) Doppler, 27, 29, 29f Contrast agents. See Ultrasound contrast agents Contrast-enhanced ultrasound (CEUS). See also Contrast-enhanced voiding urosonography; Ultrasound contrast agents in Crohn disease, 339, 339f in fungal abscesses of kidney, 771f of spleen, 495–496, 496f in IBD, 317 of liver, 358, 358f, 388t of lung, 174 of lymphatic malformation, intraperitoneal, 544f of mesenteric hemangioma, 328f in necrotizing enterocolitis, 337 of pericardial cyst, 235f of pleura, 204 of scrotum, 629 in trauma of bladder, 802, 802f of kidney, 730, 801, 802f of pancreas, 577–578, 577f of urogenital sinus, 702 Contrast-enhanced voiding urosonography (CeVUS), 730–731, 740f, 755, 802 Contrast-to-noise ratio, spatial compounding and, 24–25, 24f Corpus callosum, 53, 53f–55f, 58f, 64–66, 66f–67f anomalies of, 65–67, 66f–67f agenesis, 65–67, 66f callosal dysgenesis, 65, 67f lipoma of, 67, 67f Couinaud classification system and anatomic variants of bile duct anatomy, 456 of liver anatomy, 364, 364f, 366f, 367 and liver transplantation techniques, 409f, 410, 411f, 414f CPAM. See Congenital pulmonary airway malformation Cranial ultrasound. See Brain Craniocervical junction, 52, 104, 113 Craniosynostosis, 61, 97–99, 98f Crohn disease colon, 339–340, 339f small bowel, 317, 318f Cryptorchidism, 493, 636, 636f, 640, 653, 660, 763 CSF. See Cerebrospinal fluid Curvilinear arrays, 22 Cutaneovisceral angiomatosis with thrombocytopenia (CAT), 328 CW Doppler. See Continuous wave Doppler Cystic dysplasia of rete testis, 638, 660–661 Cystic fibrosis (CF) of appendix, 332, 332f cholecystitis, chronic, and, 449 cholelithiasis and, 440, 441f, 445 of colon, 343 gallbladder hypoplasia and, 436, 438f Gamna-Gandy bodies and, 524f gastrointestinal tract and, 321–322, 322f, 343 kidney stones and, 800 of liver, 356t, 359f, 372, 382t, 385, 529f meconium ileus and, 311 meconium peritonitis and, 537, 653 pancreas and, 570, 570f, 576 seminal vesicle agenesis and, 677 sialadenitis, chronic, and, 165 sialolithiasis and, 167

Index Cystic fibrosis transmembrane regulator (CFTR), 321, 343 Cystic partially differentiated nephroblastoma, 805 Cystosarcoma phyllodes, 960, 961f Cyst(s). See also Dermoid cyst(s); Duplication cyst(s); Epidermoid cyst(s); Lymphatic malformation(s); Pancreas, cystic neoplasms of; Pseudocyst(s); Polycystic liver disease; Renal cystic disease; Venous malformation(s) adrenal, 594, 594f arachnoid epidermoid/dermoid cyst differentiated from, 122 intraoperative spine ultrasound and, 121 mega cisterna magna differentiated from, 61 myelomeningocele and myelocele, associated with, 113 Baker, 881, 881f Bartholin, 721 branchial cleft, 133–134, 134f–135f breast cystosarcoma phyllodes and, 960 fat necrosis and, 953–954 fibrocystic disease and, 951–952, 952f galactocele, 952–953, 953f juvenile papillomatosis and, 957, 958f retroareolar, 950–951, 951f Byler disease, 443t, 469 of the canal of Nuck, 726 Caroli disease, 459–460, 462f cervical thymic, 134–136, 135f choledochal, 443t, 457–459, 458f–461f, 568f congenital pulmonary airway malformation and, 180, 180t, 181f connatal, 59–60, 60f daughter in Echinococcosis, 379–380, 379f, 499, 772 in functional ovarian cyst, 703, 704f of diaphragm, 269f, 279–280, 279f, 279t, 535, 535f filar, 109, 109f foregut duplication of GI tract, 285, 298–300, 324–326, 325f, 345 of mediastinum, 179–180, 179f–180f, 225t, 229–231, 229f–230f of neck, 136, 136f ganglion, 868, 868f Gartner duct, 720–721, 721f inclusion epidermal of peritoneum, 535, 535f, 712, 712f of vagina, 721 intramuscular, sequela of hematoma, 263 of kidneys, 774–779 echinococcal (hydatid), 772 in setting of posterior urethral valves, 764, 765f liver, 369, 369f autosomal dominant polycystic kidney disease and, 369–370, 370f echinococcal (hydatid), 378–380, 379f mesenchymal hamartoma, 392–393, 392f in mesoblastic nephroma, 803–804 müllerian duct, 675 in multilocular cystic renal tumor, 805f nabothian, 719, 719f neurenteric, 112t, 114–115 omental, 540 ovarian chocolate, 705 dermoid, 706, 706f–707f functional, 703–704, 703f–704f hemorrhagic, 703–704, 704f torsion and, 713

Index pancreatic, 569–570 autosomal dominant polycystic kidney disease and, 571, 571f “cystosis” in cystic fibrosis, 570, 570f VHL disease and, 571–572 parameniscal, 886, 886f paraovarian, 711–712, 712f parathyroid, 161–162, 162f paraurethral, 721–722, 722f peliosis hepatis, 385, 385f peliosis, splenic, 515–516 pericardial, 235, 235f peritoneal inclusion, 535, 535f, 712, 712f mesenteric, 326, 326f pilonidal, 120–121, 121f pleuropulmonary blastoma and, 189, 190f, 211–212, 212f in polycystic ovary syndrome, 724, 724f porencephalic, 72, 73f and PVL, 76–77, 77f–78f scrotal, extratesticular dermoid, 672 epididymal, 657, 669–670, 670f spermatocele, 669, 669f seminal vesicle, 675, 677f splenic, 487t,493, 493f echinococcal (hydatid),499 subependymal, 84, 85f sublingual, 163, 163f testicular, 657, 661–662, 661f, 662t cystic dysplasia of rete testis and, 638 dermoid, 666 epidermoid, 662t, 666, 667f thyroglossal duct, 133, 133f–134f thyroid colloid, 152, 152f hemorrhagic, 153f simple, 152, 152f and tight filum syndrome, 114 urachal, 756, 758, 757f–758f utricle, 675, 676f D Dandy-Walker syndrome, 58t, 61, 65, 67–68, 67f DDH. See Developmental dysplasia of the hip Deep vein thrombosis (DVT) acute, 923, 924f, 925–926, 925f causes, 923 chronic (residual), 926–927, 926f clinical evaluation, 923 Depth of penetration, 8–10, 10f, 11, 22, 24, 43, 220, 271, 836, 872 Dermal sinus, 104, 110, 113–114, 115f, 116 Dermoid cyst(s) of neck, 136–137, 137f of ovary, 706, 706f–707f of paratesticular soft tissues, 672 of scalp, 93, 94f of spine, 114, 123f of testicle, 666 Desmoid tumor, 548–549, 548f, 959, 959f, 960 Desmoid-type fibromatosis, 959 Desmoplastic small round cell tumor, 403, 475, 553, 554f Developmental dysplasia of the hip (DDH) overview, 872–873 imaging of, 873–874, 873f–875f, 874t treatment of, 875–876, 875f

977 Diaphragm acquired diaphragmatic disorders diaphragmatic dysfunction, 278–279, 278f diaphragmatic inversion, 279, 279f anatomy, 276, 276f congenital diaphragmatic anomalies Bochdalek hernia, 274–275, 275f–276f diaphragmatic hernia, 274, 274f, 274t hiatal hernia, 275, 277, 277f Morgagni hernia, 275, 276f eventration, 277–278, 277f normal anatomy, 273, 273f normal development, 272, 272f primary diaphragmatic masses benign, 279–280, 279f, 280t malignant, 280, 280f, 280t technique imaging approaches, 272 patient positioning, 271 ultrasound transducer selection, 271–272 traumatic diaphragmatic rupture, 280–281 Diaphragmatic inversion, 279, 279f Diaphragmatic paralysis, 277–278 Diastematomyelia, 113–115, 115f DICER1 gene, 189, 211, 392, 805 DICER1 mutation, 189, 190f, 551, 805 DICER1 syndrome, 211, 711 Diffuse parenchymal disease, of liver cirrhosis, 374–375, 375f fibrosis, 372–374, 372f–373f hemochromatosis, 374, 374f nonalcoholic fatty liver disease, 371–372, 372f Diffuse parenchymal lesions, of thyroid, 157–159 DIOS. See Distal intestinal obstruction syndrome Discoid meniscus, 885, 885f, 886 Disease-modifying anti-rheumatic drugs (DMARDS), 855 Disorders of sex development (DSD) cloacal malformation, 702 congenital adrenal hyperplasia, 702, 702f nomenclature and classification, 701 sex chromosome 45,X, 701, 701f 46,XX, 701 Turner syndrome, 701, 701f Distal intestinal obstruction syndrome (DIOS), and cystic fibrosis, 321, 322f Distance measurement, 8–11 Doppler angle, 21, 27–28, 28f, 29–32, 43–44 Doppler artifacts. See Ultrasound artifacts Doppler effect, 26f, 27 Doppler frequency shift, 27, 31, 43 Doppler modes, 27 Doppler shift, 27, 27f, 28, 28f, 29–32, 43–44 Doppler ultrasound. See also Color Doppler imaging; Ultrasound artifacts; Ultrasound safety blood flow detection, 27, 27f, 28, 28f, 357 continuous wave Doppler, 27, 29, 29f power Doppler, 31–32, 32f pulsed wave Doppler, 27, 29–30, 29f–30f source of error, 28 Dorsal induction disorders anencephaly, 63, 63f Chiari malformation(s), 61–63, 62f, 65, 113, 121 hydranencephaly, 63, 64f “Double bubble” sign, of duodenal atresia, 290, 306, 307f, 308 Down syndrome. See Trisomy 21

978 Duodenal atresia, 290, 306, 307f, 308, 567f Duodenal web, 306, 307f Duplication cyst(s) of colon, 345 of esophagus, 225t, 230f, 285 of mediastinum, 179–180, 179f–180f, 225t, 229, 229f, 231, 285 of neck, 136, 136f of small bowel, 314–315, 324–326, 325f of stomach, 298, 299f–300f, 300, 567 Dynamic elastography, 34 Dynamic range, 13, 13f, 47 Dysgenesis callosal, 62, 65, 67–68, 86 gonadal, 663, 701, 705t, 726f and gonadoblastoma, 707 of kidney with seminal vesicle cyst, 675 segmental spinal, 119 of thyroid gland, 151–152, 157 Dysgerminoma, 706–707, 708f, 709 Dyshormonogenesis, of thyroid gland, 152, 158 E ECA. See External carotid artery Ecchinococcal infection, 378–379, 499, 594, 772. See also Hydatid disease ECMO. See Extracorporeal membrane oxygenation Ectopia crossed renal, 744, 745f, 747, 764 gallbladder, 437–438 renal, 744, 745f testicular, 636f, 637 thyroid, 151 of ureter, 752 Ectopic pregnancy, 530, 709, 715–716, 716f Ectopic thymus, 138, 219, 223 Ectopic thyroid, 133, 151–152, 151f Ectopic ureter, 644, 720–721, 743, 744f, 752, 752f–753f, 770f, 799f, 824 EHE. See Epithelioid hemangioendothelioma Elastography, 2, 32–33, 33f, 34–35, 34f–35f, 317, 339, 359, 359t, 360f, 373, 373f, 382, 386, 411, 413f, 508, 629, 632, 641, 645, 659, 662–663, 666, 668, 731, 942 Elastography imaging dynamic elastography, 32, 34–35, 34f–35f acoustic radiation force impulse imaging, 34, 34f and liver fibrosis, 359, 359f shear wave speed imaging, 34 supersonic shear wave elastography, 35, 35f quasi-static strain elastography, 32–34, 33f Elbow annular ligament, 862, 862f congenital radial head dislocation, 863–864, 864f fat pads, 862, 863f imaging approaches, 860–862, 860f–862f joint effusion, 862, 863f normal anatomy, 860, 860f patient positioning, 860 trauma apophyseal avulsion, 864, 865f assessment, 864 distal humeral epiphyseal separation, 864, 865f pulled elbow, 866, 866f Embryonal carcinoma of ovary, 706, 709 of testicle, 662, 664

Index Embryonal rhabdomyosarcoma of biliary tree, 403 of bladder, 822 Empyema of brain, 87, 87f of pleural cavity, 202–204, 203f–204f Endometrioma 698, 705. See also Chocolate cysts End-stage renal disease (ESRD), 775, 785f, 786 Energy/amplitude Doppler, 31 Enhancement artifact, 39–40, 40f Enlarged rib end, 253, 254f, 255 Entamoeba histolytica infection, 378 Eosinophilic gastroenteritis, 297, 320–321 Epidermoid cyst(s), 93, 94, 94f, 114, 122–123, 136–137, 137f of canal of Nuck, 725 of paratesticular soft tissues, 672 of scalp, 93–94 of skin, 845 of spine, 114, 123f of spleen, 493, 493f of testicle, 662t, 666, 667f of vagina, 721 Epididymitis, 642, 643, 643f, 662, 670, 678 acute, 644 chronic, 649 Epididymo-orchitis, 639, 639t, 644, 645f Henoch-Schönlein purpura and, 646, 647f intratesticular varicocele and, 660 segmental testicular infarction and, 641–642 testicular abscess and, 645 Epidural abscess, 120 Epidural hemorrhage, 72–73 Epiploic foramen, 438, 525, 526f Epithelioid hemangioendothelioma (EHE), 402 Epstein-Barr virus Hodgkin lymphoma and, 226 inflammatory myofibroblastic tumor and, 516 primary hepatic lymphoma and, 404 PTLD and, 405–407, 405f smooth muscle tumors and, 621 and splenomegaly, 498, 498f Esophageal duplication cyst, 229, 285 Esophagus gastroesophageal reflux, 286, 287f hiatal hernia, 286, 288, 288f imaging approaches, 284 normal anatomy, 285–286, 285f–286f normal development, 284, 284f technique patient positioning, 284 ultrasound transducer selection, 284 imaging approaches, 284 Estimated glomerular filtration rate (eGFR), 784 Ewing sarcoma and breast metastases, 963 of chest wall, 240t, 259–260, 260f of diaphragm, 279t, 280 and peritoneal metastases, 555f of retroperitoneum, 621 Exostosis, 251, 853 External carotid artery (ECA), 131, 900f, 901–902, 904f Extra-axial fluid spaces, 61 Extracranial birth trauma, to cranial vault and scalp, 95, 95f Extralobar bronchopulmonary sequestration, 181–183 Extramedullary hematopoiesis mediastinum, 225t

Index retroperitoneum, 614 spleen, 516, 517f thalassemia major and, 505 Extramedullary tumors, of spine, 122–123 Extracorporeal membrane oxygenation (ECMO) and imaging of neonatal and infant brain, 53, 54, 72, 75 Extrapleural hematoma, 206 F Fallopian tube, 593, 637, 687f, 687–690, 693, 701, 714, 714f, 715 Far-field, of ultrasound beam, 15–18, 15f–17f. See also Fraunhofer zone in brain imaging, 53, 54f–55f FAST, See Focused assessment with sonography for trauma Fat necrosis, 840–841, 841f, 953–954 Fatty filum, 109, 110, 110f, 119 Fecalith, in acute appendicitis, 331, 332f Female genital tract adnexal masses, 703 adnexal torsion, 688t, 713, 713f isolated tubal torsion, 713–714, 714f massive edema, of ovary, 714–715 amenorrhea polycystic ovary syndrome, 724, 724f anatomic variants arcuate uterus, 692, 692f canal of Nuck disorders hernia, 726, 726f hydrocele, 725–726, 725f inferior epigastric vessels and, 725 cervical masses benign tumors nabothian cyst, 719, 719f malignant tumors rhabdomyosarcoma, 720, 720f congenital anomalies Müllerian duct anomalies, 692, 692t Mayer-Rokitansky-Küster-Hauser syndrome, 693, 694f Müllerian agenesis, 692–693 uterine agenesis, 693, 693f disorders of lateral fusion bicornuate uterus, 692f, 694, 695f, 696 septate uterus, 692f, 694, 695f unicornuate uterus, 692f uterus didelphys, 692f, 696, 696f disorders of vertical fusion atresia of cervix or vagina, 698, 700 imperforate hymen, 696–698, 698f OHVIRA syndrome (obstructed hemivagina and ipsilateral renal anomaly), 700–701, 700f transverse vaginal septum, 698, 699f disorders of sex development cloacal malformation, 702 congenital adrenal hyperplasia, 702 definition, 701 diagnosis, 701 nomenclature and classification, 701 sex chromosome disorders, 701 Turner syndrome, 701, 701f ectopic pregnancy, 715–716, 716f normal anatomy ovarian and uterine changes associated with menstrual cycle, 690–691, 691f, 691t ovary and fallopian tube, 688–689, 688t, 689f uterus and cervix, 689t, 690f vagina, 689–690, 690f

979 normal development external genitalia, 688 gonads and reproductive tract, 686–688 ovarian masses, 705t endometrioma, 698, 705 epithelial tumor(s) borderline epithelial tumor and cystadenocarcinoma, 710 cystadenoma, 709, 709f functional cyst, 703–704, 703f–704f germ cell tumors, 705–706 choriocarcinoma, 708–709 dysgerminoma, 707–708, 708f gonadoblastoma, 706–707 mixed germ cell, 709, 709f teratoma, 706, 706f–707f yolk sac, 708, 708f secondary tumors, 711 stromal tumors juvenile granulosa cell, 710–711, 710f Sertoli-Leydig cell, 711 thecoma-fibroma, 710 paraovarian cysts, 711–712, 712f pelvic inflammatory disease, 716, 716f–717f peritoneal inclusion cysts, 712, 712f pubertal disorders amenorrhea, 724, 724f polycystic ovary syndrome, 724, 724f precocious puberty, 723 technique three-dimensional ultrasound, 685f, 686 transabdominal ultrasound, 683–684, 684f transperineal ultrasound, 686, 686f transvaginal ultrasound, 684, 685f uterine masses benign masses adenomyosis, 718–719, 719f leiomyoma (fibroid), 717–718, 718f malignant tumors lymphoma, 719 vaginal foreign body, 723, 723f vaginal masses benign masses Bartholin cyst, 721 fibroepithelial polyp, 722 Gartner duct cyst, 720, 721f inclusion cyst, 721 Müllerian papilloma, 722 paraurethral duct cyst, 721–722, 722f malignant tumors, 722f, 722–723 clear cell adenocarcinoma and endodermal sinus tumor, 722–723 rhabdomyosarcoma, 722, 722f Femoral vein, 914, 916, 919, 921f Fetal goiter, 158 Fetal hypothyroidism, 157–158 Fetal neuroblastoma, 601–602 Fibroadenoma, of breast, 955, 956f, 957, 958f, 960 Fibrocystic disease, of breast, 951–952, 952f Fibroepithelial polyp of bladder, 818, 819f of gallbladder, 452 of ureter, 815 of vagina, 722 Fibrolamellar hepatocellular carcinoma, 401, 401f, 587f Fibromatosis colli, 138, 139f

980 Fibromuscular dysplasia renal artery stenosis and, 779, 780f Fibrosing mediastinitis, 232 Fibrosis bile ducts, 471 fibrothorax, 204, 205f hepatic, 34f, 359, 372–374, 413f, 459, 775 of mediastinum, 232 periportal, 500 pleural, 205f quadriceps tendon, 882 renal, 731 retroperitoneal, 613, 614 Fibrothorax, 204, 205f Fibrous pseudotumor, paratesticular, 670 Field of view (FOV) extended, for bowel imaging, 318f for breast imaging, 941, 961f for chest wall imaging, 241, 263f for spine imaging, 104, 107f for vascular imaging, 899 in image generation, 10f of standard ultrasound probes, 22f in transducer selection, 52 Fifth ventricle. See Ventriculus terminalis Filar cyst, 109, 109f Filar lipoma, 113–114, 114f, 119 First branchial cleft cyst, 163 FNH. See Focal nodular hyperplasia Focal foveolar hyperplasia, of stomach, 300 Focal hypoxic-ischemic injury arterial ischemic stroke, 78, 80f, 81 sickle-cell disease, 81–84, 83f, 83t venous sinus thrombosis, 81, 81f, 82 Focal nodular hyperplasia (FNH), 370, 386, 393, 394f–395f Focused assessment with sonography for trauma (FAST), 508 extended (e)-FAST, 380 Follicular adenoma, of thyroid, 152, 154, 154f Fontan procedure, and associated liver disease, 386 Fontanelle(s) bulging, in setting of brain neoplasms, 88 mastoid, 52, 57f, 72 posterior, 52–53, 66f, 72 scanning techniques, 25f Fontanelle, anterior imaging through, 52–53, 53f Foregut duplication cyst(s), 136, 179–180, 229 Foreign body(ies) in bladder, as risk factor for bladder stones, 800 chest wall, 240t, 265–266, 265f–266f scrotum, 656, 656f shadowing attenuation artifact and, 40 soft tissues, 841 ultrasound-guided localization and removal, 266, 841 vagina, 723, 723f Fournier gangrene, 649, 650f FOV. See Field of view FR. See Frame rate Frame rate (FR), 10–11, 25–26, 31, 34–35, 900 Frame time (FT), 11 Fraunhofer zone, of ultrasound beam, 15–16, 15f–16f. See also Far-field Frequency acoustics 2, 2f Doppler shift, 27, 31, 43 linear array transducer, 52, 61, 92, 482, 564

Index pulse repetition frequency, 9, 43f, 334, 900 Fresnel zone, of ultrasound beam, 15–16, 15f–16f. See also Near-field FT. See Frame time Fungal infection CNS, 88 hepatic, 377f, 378, 770, 771f pulmonary, 232 urinary tract, 770, 772 Fungal lymphadenopathy, 232 G Galactocele, 952–953, 953f Gallbladder anatomic variants, 436, 436f, 437f biliary dyskinesia, 447–449 cholecystitis acute acalculous, 447, 448f acute calculous, 444–447, 445f–446f gangrenous, 446, 446f chronic, 449, 449f porcelain gallbladder, 449, 450f cholelithiasis, 440–441, 441f–442f “wall echo shadow” (WES) sign, of cholelithiasis, 441, 442f congenital anomalies agenesis 436, 437f duplication, 439–440, 440f ectopia, 437–438, 438f hypoplasia, 436, 438f septate gallbladder, 438–439, 439f triplication, 439, 440f hydrops, 449, 450f normal anatomy, 434, 435f–436f normal development, 434 polyps, 451t adenomyomatosis, 451, 451f cholesterol, 451–452, 452f inflammatory, 452 other polypoid lesions, 452–453 sludge, 442–444, 443f–444f, 443t and hepatization of gallbladder, 442, 444f technique patient positioning, 433–434 imaging approaches, 434 ultrasound transducer selection, 434 torsion, 450 trauma, 453–454, 454f varices, 453, 453f Ganglion cyst, of wrist, 868, 868f Ganglioneuroblastoma of adrenal, 599–600, 600f of mediastinum, 225t, 233–234 of retroperitoneum, 617–618, 619f Ganglioneuroma of adrenal, 598–599, 599f of mediastinum, 225t, 233–235 of retroperitoneum, 617–618, 619f Gangrenous cholecystitis, 446, 446f Gartner duct cyst, 720–721, 721f Gastric atresia, 290 Gastric bezoar, 289, 301, 302f Gastric diaphragm (antral web), 292 Gastric duplication cyst, 298–299, 567 Gastric lipoma, 300 Gastric teratoma, 300 Gastric volvulus, 294–296, 296f, 490

Index Gastric wall thickening chronic granulomatous disease, 298, 298f eosinophilic gastroenteritis, 297–298 gastritis, 297, 297f Ménétrier disease, 297 Gastritis, 297, 297f, 300, 337 Gastroenteritis, 297, 316–317, 320–321, 330, 340–341 Gastroesophageal reflux (GER), 275, 277, 284, 286, 287f, 290 Gastrointestinal stromal tumor (GIST), 303, 304f of stomach, 303, 304f metastases to biliary tree, 475 to liver, 403 Gastrointestinal (GI) tract. appendix acute appendicitis, 331–332, 331f benign masses, 333 carcinoid, 333 cystic fibrosis, 332, 332f imaging, 330 lymphoma, 333–334 normal anatomy, 330, 330f patient positioning, 330 ultrasound transducer selection, 330 colon, 334–347 esophagus, 284–288 small bowel, 305–330 stomach, 288–304. See also specific organs Gaucher disease, spleen and, 506–507, 506f–507f Genu recurvatum. See Congenital knee dislocation GER. See Gastroesophageal reflux Germ cell tumors primary of mediastinum, 225–226, 225t of ovary, 705–709, 705t, 706f–709f of testis, 662–664, 662t, 663f–664f metastatic to peritoneal cavity, 546t, 555 to retroperitoneum, 620–621 GI tract. See Gastrointestinal tract Giant cell tumor of the tendon sheath, of hand, 869, 869f GIST. See Gastrointestinal stromal tumor Glenohumeral dysplasia, 856, 858f–859f Global hypoxic-ischemic injury preterm infants, 76–77, 78f term infants, 77–78, 79f–80f Glomerulocystic kidney disease, 777 Goiter fetal, 158 multinodular, 157 Gonadoblastoma of ovary, 705t, 706–707 of testicle, 662–663, 662t Graft-versus-host disease (GVHD), of GI tract, 322–323, 323f Granular cell tumor of bile duct, 473 of breast, 955, 955t of head and neck, 960, 960f Granulomatosis with polyangiitis, 504, 537 Granulosa cell tumor of ovary, 690 of testicle, 665–666, 666f Graves’ disease, 157, 159–160, 160f fetal goiter and, 157

981 Gray matter heterotopia, 62, 64, 67–68, 69f. See also Migration disorders Grayscale artifacts enhancement, 39–40 mirror image, 37 partial volume, 40–41 refraction, 37–38 reverberation, 38–39, 38f–39f shadowing attenuation, 40–41, 40f–41f side lobes, 39, 40f GVHD. See Graft-versus-host disease Gynecomastia, 661, 665, 948, 949, 949f, 957 H Harmonic imaging, 23f, 23–24, 36, 434, 482, 730 tissue harmonic imaging, 24 Hashimoto thyroiditis, 157–158, 160–161, 161f, 167f, 701 HCC. See Hepatocellular carcinoma Hemangioma. See also Congenital hemangioma; Infantile hemangioma; Non-involuting congenital hemangioma; Partially involuting congenital hemangioma of neck, 138 of testis, 667 Hemarthrosis, 855, 855f, 857f, 864, 865f Hematocele, 642, 651–652, 652f, 654f, 655, 655f, 656 Hematoma birth trauma-related, 93 breast, 953 duodenal, 319, 319f epidural, 95, 124, 124f extrahepatic, 423f extrapleural, 206 gallbladder, 454f intramuscular, 263, 841–842 perinephric, 613f, 796 perirenal, 802f retroperitoneal, 613, 614f scalp, 95 spermatic cord, 659 splenic, 522 subcapsular, 498, 509, 785 subdural, 74, 93, 124 subgaleal, 95, 95f testicular, 654–655 Hematomyelia, 124 Hematopoiesis, in fetus, 516 Hemimegalencephaly, 68. See also Neuronal proliferation disorders Hemochromatosis, 374, 374f, 523 Hemolytic–uremic syndrome (HUS), 343, 344f, 785–786 Hemorrhagic effusion, 205 Hemoperitoneum, 530, 531f Hemothorax, 202, 204–206, 252, 264–265, 279f, 508 Henoch–Schönlein purpura (HSP) and AKI, 785 and bowel wall thickening from hemorrhage, 316, 319–320, 320f and scrotum, 646, 647f–648f and small bowel intussusception, 314 Hepatic adenoma, 394–396, 396f–397f Hepatic artery pseudoaneurysm, 418, 418f Hepatic artery stenosis, 415, 417, 417f Hepatic artery thrombosis, 410, 415, 416f, 417 Hepatic circulation, 366 Hepatic mesenchymal hamartoma, 392

982 Hepatic vein(s) Budd-Chiari syndrome, 383f, 383–384 normal, 363, 366, 366f outflow obstruction, in liver transplantation, 420, 421f Hepatization of gallbladder, 442, 444f of lung, 176, 176f, 176t, 183 Hepatoblastoma, 190, 370, 397–398, 398f–399f, 400, 527f, 571, 581, 948 Hepatocellular carcinoma (HCC), 236f, 262f, 370, 373–375, 386, 400, 400f, 401, 401f, 587f, 935 Hereditary hemorrhagic telangiectasia, 140, 394 Herlyn-Werner-Wunderlich syndrome. See Obstructed hemivagina and ipsilateral renal anomaly Herpes simplex virus, congenital, 595 Hiatal hernia, 274, 274f, 275, 277f, 284, 286, 288, 288f High frequency linear array transducer, 52, 61, 92, 482, 564 High-intensity transient artifacts, 47 Hindfoot. See Ankle Hip developmental dysplasia overview, 872–873 imaging of, 873–874, 873f–875f, 874t treatment of, 875–876, 875f imaging approaches for hip dysplasia, 871–872, 871f for synovitis and effusion, 872, 872f normal anatomy, 869–870, 870f patient positioning, 870, 871f proximal focal femoral deficiency, 876, 876f septic arthritis, 877 slipped capital femoral epiphysis, 877–878, 877f synovitis and effusion, 871–872 transient synovitis, 877 Histiocytosis Langerhans cell of cervical lymph nodes, 146 of lung, 186t of scalp, 93 sclerosing cholangitis and, 471 of spleen, 487t, 521–522, 521f–522f of testicle, 669 sinus histiocytosis (Rosai-Dorfman-Destombes disease) of neck, 146 of scrotum, 662, 662t HIV. See Human immunodeficiency virus Hodgkin lymphoma. See also Burkitt lymphoma; Lymphoma; Non-Hodgkin lymphoma; specific organs chest wall, 261 mediastinum, 226–227, 227f neck, 149–150 retroperitoneum, 615 secondary breast carcinoma and history of, 961–962 spleen, 487t, 518–519, 519f–520f thyroid, 157f Holoprosencephaly, 63–64, 64f, 65, 67 alobar, 64, 64f lobar, 64 semilobar, 64 HPS. See Hypertrophic pyloric stenosis HSP. See Henoch–Schönlein purpura Human immunodeficiency virus (HIV), 84, 146, 375, 404, 472, 497, 501, 609 HUS. See Hemolytic-uremic syndrome Hyaline membrane disease, 186 Hybrid congenital lung anomalies, 183 Hydatid disease

Index of kidney, 772 of liver, 379, 379f of spleen, 499 Hydranencephaly, 63, 64f Hydrocephalus. See also Non-communicating hydrocephalus in bacterial meningitis, 87 benign external hydrocephalus, 92–93, 93f in Chiari I malformation, 61 in Chiari II malformation, 62 communicating, 90 in Dandy-Walker syndrome, 67, 67f in fungal infection, 88 in high-flow malformations, 90 non-communicating, 90 obstructive, 72, 812f post-hemorrhagic, 70, 70t, 71f, 72 in toxoplasmosis, 85 Hydromyelia, 113, 115–116, 125 Hydronephrosis bladder exstrophy and, 759 as cause of abdominal mass, 803 chronic rejection after renal transplantation and, 792 classification of, 746, 747f cloacal malformation and, 760 cloacal exstrophy and, 759 crossed renal ectopia and, 744 ectopic ureter and, 752 extrinsic ureteral obstruction and, 618f, 622f, 794, 794f, 796, 822 fungal infection and, 771 as indication for urinary diversion, 824 posterior urethral valves and, 532f, 764–765, 764f–765f retrocaval ureter and, 934 retroperitoneal fibrosis and, 613–614 UPJ obstruction and, 746–748, 748f ureteral extension of Wilms’ tumor and, 816 UTI and, 768 xanthogranulomatous pyelonephritis and, 773, 774f Hydrops of fetus, 614 of gallbladder, 449, 450f vein of Galen malformation and, 90 VUR and, 743, 754f, 794 Hyperparathyroidism parathyroid adenoma and, 162 parathyroid cyst and, 161 parathyroid hyperplasia and, 162, 162f treatment of, 163 Hyperplastic/adenomatoid nodules, of thyroid, 154 Hyperthyroidism Graves’ disease and, 159–160, 160f Hypertrophic pyloric stenosis (HPS), 292, 293f, 294–295, 386 Hypertrophy, compensatory of accessory spleen, 490 of kidney, 736, 736f, 776 of testis, 636 Hypothyroidism congenital, 151, 152 delayed anterior fontanelle closure and, 52 fetal, 157, 158f infantile hepatic hemangioma (IHH) and, 388t, 391 slipped capital femoral epiphysis and, 877 Hypoxic-ischemic encephalopathy (HIE), 75 Hypoxic-ischemic injury, of brain, 75–84, 76f focal hypoxic-ischemic injury arterial ischemic stroke, 78, 78f, 80f, 81 sickle cell disease, 81, 83–84 venous sinus thrombosis, 81–82

Index global hypoxic-ischemic injury preterm infants, 76–78 term infants, 77, 79–80 I IBD. See Inflammatory bowel disease ICA. See Internal carotid artery Idiopathic scrotal edema, 646, 649, 649f IJV. See Internal jugular vein ILD. See Interstitial lung disease Ileal atresia, 307–308, 312. See also Intestinal atresia Ileal stenosis, 308–309 Ileocolic intussusception, 314–316, 315f–316f, 329, 343 Image display, 14, 46f A-mode imaging, 14, 14f B-mode imaging, 14, 14f C-mode imaging, 14 M-mode imaging, 14, 14f Image storage, 14 IMT. See Intima-media thickness Inclusion cyst. See also Epidermoid cyst of peritoneum, 535, 535f, 712, 712f of vagina, 721 Indiana pouch, 824, 825f Inertial cavitation, 48 Infantile hemangioma of adrenal gland, 608 of breast, 955–956, 955t, 957f of gastrointestinal tract, 327, 328f of liver, 388t, 389, 391 of neck, 138, 139f, 140 of pancreas, 579 of peritoneal cavity, 542, 545, 546t of retroperitoneum, 608, 617 of salivary gland, 166 of scalp, 95–96, 96f of skin/subcutaneous tissues, 248–249, 889–890, 890f, 890t of spleen, 517 Infantile hepatic hemangioma, 389, 391 Infectious colitis, 340–341 Infectious enteritis, 316–317 Infectious lymphadenopathy mediastinal, 231–232, 232f Inferior vena cava (IVC) anatomy, 931–933, 932f development, 931 duplication, 934 interruption, 932, 934f left-sided, 934 May-Thurner syndrome, 936 normal anatomy, 931–933, 931f–933f normal development, 931 retrocaval ureter, 933–934 thrombosis, 934–936 Inflammatory bowel disease (IBD), 297, 305, 317, 471, 475, 535, 612, 800. See also Crohn disease Inflammatory myofibroblastic tumor bladder, 818–819, 819f kidney, 806, 807f pancreas, 580 peritoneal cavity, 546t, 550, 550f renal transplantation and, 797–798 retroperitoneum, 622 scrotum, 673 spleen, 487t, 516–517 stomach, 300–301

983 Inflammatory polyps, 452 Inflammatory pseudotumor, 550, 806 Infundibulopelvic stenosis, 748–749, 750f Inspissated bile syndrome, 470–471, 470f INSS. See International Neuroblastoma Staging System Instrumentation array transducer, 19–22, 20f, 21f harmonic imaging, 23–24 image display, 14, 14f image storage, 14 mechanical transducer, 14–19, 15f–19f receiver, 12–14 transducer, 11–12, 12f lead-zirconate-titanate, 4f, 12 transducer selection, 22–23, 22f transmitter, 11–12 Intensity, of ultrasound, 7–8, 8f, 13–14, 18, 23, 23f, 39, 44, 48, 189, 325–326, 400, 542, 551, 738 Internal carotid artery (ICA), 63, 83, 83f, 84, 900f, 902, 904f Internal jugular chain lymph nodes, 129 Internal jugular vein (IJV) anatomic variants, 906 development, 906 jugular vein phlebectasia, 906, 908f normal anatomy, 906, 907f stenosis, 908 thrombosis, 906, 908, 909f venous aneurysm, 908 International Neuroblastoma Risk Group Staging System (INRGSS), 586, 601t International Neuroblastoma Staging System (INSS), 233, 601, 601t International Society for the Study of Vascular Anomalies (ISSVA) classification chest wall vascular tumors, malformations and, 247–248, 248t gastrointestinal tract vascular anomalies and, 327 lymphatic malformations of mediastinum and, 227 musculoskeletal system vascular anomalies and, 889, 890t, 892 vascular disorders of brain and, 89 International Thymic Malignancy Interest Group (ITMIG), 221, 222f Interstitial lung disease (ILD), 185–186, 186t, 187f, 503f Intestinal atresia, 307–308, 308f, 653 Intestinal polyp(s), 327, 327f Intima-media thickness (IMT), 902, 903f Intra-articular hemorrhage, 855, 855f Intracranial hemorrhage preterm infants cerebellar hemorrhage, 72, 74f neonatal periventricular/intraventricular hemorrhage, 70, 70t, 71f, 72 Papile grading system, 70, 70t, 71f periventricular hemorrhagic infarction, 72, 72f–73f term infants epidural hemorrhage, 72, 74 parenchymal hemorrhage, 75 subdural hemorrhage, 74–75, 74f subpial hemorrhage, 75, 75f Intracranial lipoma, 67 Intraductal papilloma, 956, 957f Intralobar bronchopulmonary sequestration, 181–182 Intramammary lymph node, 954, 954f Intramedullary tumors, of spine, 122, 122f Intratesticular varicocele, 660, 660f Intusussusception ileocolic, 315–316, 315f–316f, 329, 343 small bowel, 313–315, 314f, 323–324, 327, 327f, 329f ISSVA. See International Society for the Study of Vascular Anomalies ITMIG. See International Thymic Malignancy Interest Group

984 IVC. See Inferior vena cava Ivemark syndrome, 491–492 J Jaundice Alagille syndrome and, 468 bile duct stricture and, 472 bile duct tumors and, 473–474, 474f biliary atresia and, 463, 464f Byler disease and, 469 Caroli disease and, 459 cholecystitis and, 444, 447 choledochal cyst and, 457 choledocholithiasis and, 469 cholelithiasis and, 440–441 cirrhosis and, 374 embryonal rhabdomyosarcoma and, 403 fungal liver infection and, 378 hemoglobinopathies and, 505 hepatic artery pseudoaneurysm rupture and, 418 hepatoblastoma and, 397 hepatocellular carcinoma and, 400 inspissated bile syndrome and, 470 lymphoma and, 404 mesenchymal hamartoma and, 392 Mirizzi syndrome and, 471 neonatal hepatitis syndrome and, 463 pancreatic tumors and, 579, 585–587 PTLD of liver and, 406 sclerosing cholangitis and, 471 spontaneous perforation of extrahepatic bile ducts and, 472 viral hepatitis and, 375 Jejunal atresia, 308, 308f. See also Intestinal atresia Jejunal stenosis, 308–309 Jejunoileal atresia. See Intestinal atresia JIA. See Juvenile idiopathic arthritis Joint effusion. See specific joints Joints hemarthrosis, 855, 855f juvenile idiopathic arthritis, 854–855, 855f septic arthritis, 854, 854f Jugular vein. See Internal jugular vein Jumper’s knee. See Sinding-Larsen-Johansson syndrome Junctional parenchymal defect, 735, 735f Juvenile fibroadenoma, of breast, 955 Juvenile granulosa cell tumor of ovary, 710–711, 710f of testicle, 665–666, 666f Juvenile idiopathic arthritis (JIA) joints and, 854–855, 855f spleen and, 503–504, 504f Juvenile papillomatosis, of breast, 957, 958f Juvenile polyposis syndrome, 327, 344–345 Juvenile polyp(s), 327, 344–345, 345f Juvenile (virginal) hypertrophy, of breast, 948 Juvenile xanthogranuloma, of scrotum, 670 K Kaposiform hemangioendothelioma (KHE) of musculoskeletal system, 891, 891f of pancreas, 586–587 of retroperitoneum, 608, 622, 622f of spleen, 521 Kaposiform lymphangiomatosis (KLA), of spleen, 513, 515

Index Kasabach-Merritt phenomenon (KMP), 521, 587, 622, 891 Kawasaki disease, 146, 503, 929, 931 KHE. See Kaposiform hemangioendothelioma Kidney. See also Urinary tract abdominal masses, 803 anomalies of renal collecting system calyceal diverticulum, 750, 751f arteriovenous fistula, 783–784, 785f cystic disease acquired cystic kidney disease, 779, 779f autosomal dominant polycystic kidney disease, 775, 775f autosomal recessive polycystic kidney disease, 775–776, 776f classification, 774–775 family history, 775 glomerulocystic kidney disease, 777, 778f imaging, 774, 774f multicystic dysplastic kidney, 736, 736f, 745f, 776–777, 776f–777f medullary cystic disease, 777 nephronophthisis, 776–777, 777f tuberous sclerosis, 778, 778f Von Hippel-Lindau disease, 778, 778f medical renal disease acute kidney injury, 784–786, 786f chronic kidney disease, 786 metastases neuroblastoma, 814–815 osteosarcoma, 814, 815f pseudoaneurysm, 781, 783f renal artery stenosis, 779, 780f, 781 renal artery thrombosis, 781, 782f renal vein thrombosis, 781–783, 784f trauma, 801–802 contrast-enhanced ultrasound diagnosis, 801–802, 802f tumors angiomyolipoma, 804, 804f clear cell sarcoma, 811–812, 812f imaging considerations, 803 inflammatory myofibroblastic tumor, 806, 807f lymphoma, 813–814, 814f leukemia, 813, 813f mesoblastic nephroma, 803–804, 803f metanephric adenoma, 805, 806f metastases neuroblastoma, 814, 815f osteosarcoma, 814, 815f multilocular cystic renal tumor cystic nephroma, 805, 805f cystic partially differentiated nephroblastoma, 805 nephroblastomatosis, 810 nephrogenic rests, 810, 810f ossifying renal tumor of infancy, 807 primitive neuroectodermal tumor, 812–813 renal cell carcinoma, 810–811, 811f renal medullary carcinoma, 812 sickle cell trait and, 812 rhabdoid tumor, 811, 812f atypical teratoid rhabdoid tumor of brain and, 811 primitive neuroectodermal tumor of brain and, 811 secondary tumors of, 711, 711f staging, 803 synovial cell sarcoma, 813 tumor invasion, 807 Wilms’ tumor, 806–808, 810, 808f–809f

Index nephrogenic rests, nephroblastomatosis and, 810, 810f renal vein and vena caval invasion by, 807, 809f KLA. See Kaposiform lymphangiomatosis Klippel-Trenaunay syndrome, 90, 816, 817f Knee alignment of, 878 articulations, 878 Baker (popliteal) cyst, 881, 881f Bipartite/multipartite patella, 884–885, 885f congenital knee dislocation (genu recurvatum), 882–883, 883f congenital patellar dislocation, 883–884, 884f discoid meniscus, 885–886, 885f–886f extensor mechanism, 879, 879f imaging approaches, 878f, 879 joint effusion, 881, 881f meniscal tears, 885–886, 885f–886f menisci, 880, 880f normal anatomy, 878, 878f Osgood-Schlatter disease, 844f, 886 patellofemoral joint, 878f, 879, 880f patient positioning, 879, 879f Sinding-Larsen-Johansson syndrome, 886–887, 887f tibial hemimelia, 882, 882f tibial tubercle, 880, 880f Kocher criteria, for differentiating septic arthritis and transient synovitis of the hip, 877 L Ladd bands, 309, 309f, 312f Langerhans-cell histiocytosis (LCH), 521–522, 521f–522f LCH. See Langerhans-cell histiocytosis Lead-zirconate-titanate (PZT), 4f, 12 Leiomyosarcoma bladder, 823 gastric, 303 paratesticular, 674 retroperitoneal, 621 Lemierre syndrome, 908 Lesser peritoneal sac, 525, 526f Levene index, for ventricular size measurement, 90 Leydig cell hyperplasia, 661 Leydig cell tumor, 661, 665, 665f Li-Fraumeni syndrome adrenocortical tumors and, 597 rhabdomyosarcoma and, 551, 720, 822 Lipoblastoma neck, 147–149, 148f peritoneal cavity, 546t, 547 retroperitoneum, 617 soft tissue, 846–847, 847f Lipoma(s) brain, 58t, 67, 67f chest wall, 240t, 257, 257f–258f diaphragm, 279–280, 279t filum terminale, 112t, 113–114, 114f gastric, 300 intraspinal, 319f, 116, 119, 120f neck, 147–149, 148f pancreas, 580 paratesticular, 671, 672f peritoneal cavity, 546, 546f, 546t retroperitoneum, 617 soft tissue, 846, 846f Lipomatosis chest wall, 257

985 peritoneal cavity, 546, 546t, 547f soft tissue, 846 Lipomyelocele, 116, 117f Lipomyelomeningocele, 116, 117f Lissencephaly (agyria), 68. See also Migration disorders Littoral cell angioma, 517–518 Liver anatomic variants, 367–369, 368f, 368 bacterial infection, 375–376, 377f benign masses congenital hemangioma, 387, 387f, 388t, 389, 389f–390f, 391 focal nodular hyperplasia, 388t, 393, 394f–395f hepatic adenoma, 388t, 394–396, 396f–397f infantile hemangioma, 388t, 391, 391f mesenchymal hamartoma, 388t, 392–393, 393f biliary atresia, 408 biliary complications of liver transplantation bile leak, 413, 414f biliary stricture, 414, 415f blunt abdominal trauma, 380, 380f, 381f Budd–Chiari syndrome, 383–384, 383f congenital anomalies congenital portosystemic shunts, 370, 371f cysts, 369, 369f polycystic liver disease, 369–370, 370f contrast-enhanced ultrasound, 358, 358f diffuse parenchymal disease cirrhosis, 374–375, 375f fibrosis, 372–374, 372f–373f hemochromatosis, 374, 374f nonalcoholic fatty liver disease, 371–372, 372f Doppler ultrasound, 357, 357f–358f elastography, 359, 359f, 359t, 360f fluid collections extrahepatic, 423–424, 423f–424f intrahepatic, 425, 425f fungal infection, 378, 378f grayscale imaging, 356–357, 356f, 356t imaging approaches, 356 infection viral hepatitis, 375, 375f bacterial infection, 375–376, 376f–377f fungal infection, 378, 378f parasitic infection, 378–380, 379f malignant tumors embryonal rhabdomyosarcoma, 403 epithelioid hemangioendothelioma, 402–403 fibrolamellar variant of HCC, 388t, 401, 401f hepatoblastoma, 388t, 397–400, 398f–399f hepatocellular carcinoma, 388t, 400, 400f leukemia, 407, 407f lymphoma, 404–405, 405f metastases, 403–404 posttransplant lymphoproliferative disorder, 405–407, 406f PRETEXT staging system, 398 rare primary tumors, 402–403, 404f undifferentiated embryonal sarcoma, 388t, 402 normal anatomy, 363–369, 363f–368f circulation, 366–367, 366f Couinaud classification system, 364, 364f, 366f, 367 ligaments, 364–365, 365f–366f parenchyma, 367, 367f normal development, 360–362, 361f–362f passive venous congestion, 386, 386f peliosis hepatis, 385, 385f portal hypertension, 382–383, 382f, 382t

986 Liver (cont.) Budd-Chiari syndrome, 383–384, 383f portal venous gas, 386–387, 387f sinusoidal obstruction syndrome(SOS), 384–385, 384f technique imaging approaches contrast-enhanced ultrasound, 358, 358f Doppler ultrasound, 357, 357f elastography, 359–360, 359f–360f, 359t grayscale imaging, 356–357, 356f, 356t patient positioning, 356 ultrasound transducer selection, 356 trauma blunt abdominal, 380, 380f–381f umbilical vein catheterization, 380–382, 381f Liver transplantation, 408–425, 408t biliary complications, 408t bile leak, 413, 414f biliary stricture, 414, 415f fluid collections, 408t, 423–425 extrahepatic collections abscess, 423–424, 424f biloma, 423–424, 424f hematoma, 423, 423f intrahepatic collections abscess, 425, 425f biloma, 425, 425f hematoma, 425 non-vascular postoperative complications, 408t normal liver transplant ultrasound, 412 preoperative and postoperative imaging considerations, 408t, 411 rejection, 412, 412f–413f surgical technique living-related donor and split liver grafts, 409–410, 409f, 411f whole liver transplantation, 409–410, 409f–410f vascular complications, 408t hepatic artery pseudoaneurysm, 418, 418f hepatic artery stenosis, 415, 417, 417f hepatic artery thrombosis, 415, 416f hepatic vein outflow obstruction, 420, 421f inferior vena caval stenosis and thrombosis, 422, 422f portal vein stenosis, 419–420, 419f–420f portal vein thrombosis, 418–419, 419f Lobar holoprosencephaly, 64 Longitudinal sound wave, 2f, 3 Lower extremities arteries anatomy, 913–914 development, 913 veins anatomy, 922–923, 923f deep and superficial systems, 922, 922f development, 922 Lung abscess, 184–185, 184f–185f air bronchograms, 176, 177f, 177t atelectasis, 183 bronchopulmonary sequestration, 180–183, 182f extralobar, 182–183 hybrid congenital lung anomalies, 183 intralobar, 181–182 congenital lung anomalies, 177–183 congenital lobar hyperinflation, 178–179, 178f congenital pulmonary airway malformation, 180, 180t, 181f foregut duplication cyst, 179–180, 179f–180f hybrid congenital lung anomalies, 183

Index consolidation, 177f, 183 hepatization, 176, 176f, 177t interstitial lung disease, 185–186, 186t, 187f M-mode appearance, 175f, 176 normal anatomy, 175 normal development, 174–175, 174f necrosis, 183 pulmonary lymphangiectasia, 188, 188f pulmonary masses, 188–191 benign pulmonary masses hamartoma, 189 malignant pulmonary neoplasms metastases, 190, 191f primary malignant pulmonary neoplasms pleuropulmonary blastoma, 189, 190f rhabdomyosarcoma, 189–190 technique contrast-enhanced ultrasound, 174 imaging approaches, 174 patient positioning, 173 ultrasound transducer selection, 173 ultrasound signs A-lines, 175f, 176, 177t B-lines, 176, 176f, 177t lung sliding, 175, 175f, 177t pleural line, 175, 175f “Lying down” adrenal sign, in renal agenesis, 742, 742f Lymph node(s) Castleman disease and, 549–550, 549f differentiation from parathyroid adenoma, 162–163 Epstein-Barr viral infection and, 498 infectious, 144–146, 144f–146f, 316, 494, 615 intramammary, 954, 954f intussusception and, 314 mediastinal, 198, 198f, 221, 225, 231–233 metastatic, 150, 167, 213, 236f, 259f, 397, 400, 473, 554, 616, 616f, 620, 663, 664f, 673, 707, 720, 810–813, 822, 961, 962f neck, 128–129, 129f neuroblastoma staging and, 601t parotid gland, 131, 132f pericardial, 235 peritoneal, 525 reactive, 408t, 412, 646, 648 retroperitoneal, 611 sarcoidosis and, 502 scalp, 93, 94 Lymphadenopathy bacterial parotitis and, 164–165 cervical, 146, 146f, 149, 149f, 150 intramammary, 954 mediastinal, 231–233, 232f mesenteric, 541–542, 541f, 648f pericardial, 235, 236f peritoneal, 536, 615 retroperitoneal, 615–616, 664f sialadenitis, chronic, and, 166 thyroid cancer and, 156, 156f, 156t viral infection of salivary glands and, 164 Lymphangiectasia, 188, 188f, 321, 321f Lymphatic malformation(s) bladder, 816, 817f breast, 955 diaphragm, 279–280, 279t mediastinum, 225, 225t, 227–229, 228f neck, 140, 144, 144f pancreas, 579

Index peritoneal, 542, 543f–544f, 594f retroperitoneal, 614, 615f salivary gland, 166 scrotum, 670–671, 671f soft tissue, 892, 893f spleen, 511–513, 514f thoracic, 206, 206f, 248t, 251, 251f–252f Lymphocele after renal transplantation, 794, 796, 796f scrotal, 652 Lymphoma. See also Burkitt lymphoma; Hodgkin lymphoma; Non-Hodgkin lymphoma; specific organs adrenal, 609 biliary tree, 475 breast, 960, 964f Castleman disease and risk of, 550 chest wall, 261–262, 261f, 963 chylous effusion and, 206–207 Epstein-Barr viral infection and, 498 gallbladder, 453 GI tract, 301–302, 303f, 315, 329–330, 329f, 333, 333f, 342, 345, 346f kidney, 813–814, 814f liver, 356t, 382t, 404–405, 405f mediastinum, 226–227, 227f neck, 149–150, 149f ovary, 711 pancreas, 585, 586f, 587 paratesticular, 673–674 peritoneal cavity, 546t, 551, 552f retroperitoneum, 615–616, 616f retroperitoneal fibrosis and, 613 secondary breast carcinoma and history of, 961–962 spleen, 487t, 518–519, 518f–520f testicle, 668 thyroid, 157, 157f uterus, 719 Lymphoproliferative disorder. See Posttransplant lymphoproliferative disorder Lysosomal storage diseases, 506–507, 506f–507f M Macrophage activation syndrome, 503–504 Male genital tract inguinal hernia direct, 658–659, 658f indirect, 657–658, 657f–658f Valsalva maneuver and, 657 paratesticular masses benign tumors adenomatoid tumor, 672 dermoid, 672 leiomyoma, 672 lipoma, 671, 672f neurofibroma, 672 papillary cystadenoma, 672–673 malignant tumors, primary inflammatory myofibroblastic tumor, 673 liposarcoma, 673 rhabdomyosarcoma, 673, 673f malignant tumors, secondary fibrosarcoma, 674 leiomyosarcoma, 674 leukemia, 673 lymphoma, 673–674

987 neuroblastoma, 673 Wilms’ tumor, 673 non-neoplastic lesions cystic dysplasia of epididymis, 670 ectopic adrenal rest, 670 epididymal cyst, 669–670, 670f fibrous hamartoma of infancy, 670 fibrous pseudotumor, 670 juvenile xanthogranuloma, 670 spermatic granuloma, 670 spermatocele, 669, 669f vascular anomalies arteriovenous malformation, 671 lymphatic malformation, 670–671, 671f venous malformation, 671 prostate and seminal vesicles congenital anomalies enlarged prostatic utricle, 675 Müllerian duct cyst, 675 prostatic utricle cyst, 675, 676f seminal vesical agenesis/hypoplasia, 677–678 seminal vesicle cyst, 675, 677f inflammatory disorders prostatic abscess, 678 prostatitis, 678 normal anatomy of prostate, 674, 674f of seminal vesicles, 675, 675f normal development, 674 technique imaging approaches, 674 patient positioning, 674 ultrasound transducer selection, 674 tumors of prostate and seminal vesicle, 678 leukemia, 678 rhabdomyosarcoma, 678 scrotum acute scrotal pain, 639t anatomical variants testicular appendages, 635, 635f vessels, 635 calcification loose bodies, 653, 653f meconium peritonitis, 653, 654f testicular microlithiasis, 652–653, 653f testicular tumors and, 653 congenital anomalies anorchidism, 636 bell clapper deformity, 639, 639f cryptorchidism, 636, 636f cystic dysplasia of rete testis, 638 polyorchidism, 637, 637f splenogonadal fusion, 638, 638f testicular agenesis, 636 testicular ectopia, 637–638 testicular hypoplasia, 637, 637f testicular regression syndrome, 636–637 fluid collections abdominoscrotal hydrocele, 651 hematocele, 651–652, 652f, 656 hydrocele, 649–650, 651f of spermatic cord, 650–651, 652f lymphocele, 652 inflammatory disorders acute epididymitis and epididymo-orchitis, 639t, 644, 645f chronic epididymitis, 649

988 Male genital tract (cont.) dancing megasperm, 649 epididymal abscess, 645 Fournier gangrene, 649, 650f Henoch-Schönlein purpura, 646, 647f–648f idiopathic scrotal edema, 646, 649f orchitis, isolated, 644–645 scrotal abscess, 645–646, 646f testicular abscess, 645 normal anatomy blood supply, 633–643, 633f–635f epididymis, 632 spermatic cord, 632, 633f testes, 631–632, 632f, 632t testicular appendages, 633, 633f normal development, 630–631, 630f segmental testicular infarction, 639t, 641–642, 662 arterial segmental testicular infarction, 642 venous testicular infarction, 642–643 technique imaging approaches, 630 patient positioning, 629 ultrasound transducer selection, 629–630 testicular masses ultrasound appearance and clinical features, 662t testicular masses, non-neoplastic, 660–662 adrenal rests, 660–661, 661f hamartoma, 661 Leydig cell hyperplasia, 661 simple cyst, 661–662, 661f sinus histiocytosis (Rosai-Dorfman-Destombes disease), 662 testicular torsion, 639–641, 639t, 640f–642f spermatic cord and, 639t, 640 torsion of testicular appendages, 643, 644f testicular tumors, primary, 662t adenomatoid, 668 “burned out” (Azzopardi), 662 choriocarcinoma, 664 dermoid cyst, 666 elastography, 663 embryonal carcinoma, 663–664 epidermoid cyst, 666, 667f fibroma, 666 follicular lymphoma, 668 germ cell, 662, 663f gonadoblastoma, 663 hemangioma, 667, 667f leiomyoma, 668 lipoma, 667 neurofibroma, 666 seminoma, 663 stromal tumors, 664–666 granulosa cell, 665–666, 666f Leydig cell, 665, 665f Sertoli cell, 665, 665f teratocarcinoma, 664 teratoma, 663, 664f other testicular tumors yolk sac, 662–663, 664f testicular tumors, secondary carcinoid, 669 Langerhans cell histiocytosis, 669 leukemia, 668, 668f neuroblastoma, 668–669 retinoblastoma, 669 rhabdomyosarcoma, 669

Index Wilms’ tumor, 669 trauma blunt scrotal trauma, 653–654, 654t foreign body, 656, 656f penetrating scrotal trauma, 656 repetitive scrotal microtrauma, 657 scrotal urinoma, 657 testicular fracture, 654t, 655, 655f testicular hematoma, 654–655, 654f, 654t testicular rupture, 654t, 655–656, 655f varicocele, 659, 659f intratesticular varicocele, 660, 660f Malignant gastric tumor(s) gastrointestinal stromal tumor, 303, 304f leiomyosarcoma, 303 lymphoma, 301–302, 303f primary gastric adenocarcinoma, 303 Malignant hemangioendothelioma of breast, 962. See also Angiosarcoma Malignant peripheral nerve sheath tumor (MPNST), 147 MALToma, 167 Mammary gigantism, 948 Mature cystic teratoma, of ovary, 706, 706f Mayer-Rokitansky-Küster-Hauser Syndrome (MRKH), 693, 694f May-Thurner syndrome iliofemoral thrombosis and, 936 transplant renal vein thrombosis and, 789 MCDK. See Multicystic dysplastic kidney Mechanical index (MI), 34 Mechanical transducer, 14–19, 15f–19f Meckel diverticulum, 323–324, 324f Meconium ileus, 311–312, 312f Meconium peritonitis, 312–313, 537, 538f, 653, 654f Meconium pseudocyst, 313, 313f Mediastinal neurenteric cysts, 229 Mediastinum cardiophrenic angle masses lymphadenopathy, 235, 236f pericardial cyst, 235, 235f normal anatomy, 221–225 compartment approach, 221, 222f, 223 esophagus, 224–225, 225f thymus, 220, 223, 223f trachea, 224, 224f normal development, 220–221, 221f paravertebral (posterior) mediastinal masses ganglioneuroblastoma, 233–234 ganglioneuroma, 234–235 neuroblastoma, 233, 234f prevascular (anterior) mediastinal masses lymphatic malformation, 227–229 lymphoma, 226–227, 227f teratoma, 225–226, 226f technique imaging approaches, 220 patient positioning, 219–220 ultrasound transducer selection, 220 visceral (middle) mediastinal masses foregut duplication cysts, 229–231, 229f–230f lymphadenopathy, 231–233, 232f Medullary cystic disease, of kidney, 777 Medullary nephrocalcinosis, 798, 798f Megacystitis-microcolon-intestinal hypoperistalsis syndrome (MMIHS), 763 Meigs syndrome, 705t, 710 Ménétrier disease, 297

Index Meningitis, neonatal/infant, 86–88, 88f Meningocele, 94, 111t, 112, 112t, 116, 118f–119f, 762, 767 Mesenchymal hamartoma of chest wall, 257–258 of liver, 388t, 392–393, 392f Mesenteric cyst, 326, 326f Methicillin-resistant Staphylococcus aureus (MRSA), 184f, 839, 851, 854 MI. See Mechanical index Microbubbles, 35–37, 36f Microgastria, 290, 292 Mid-aortic syndrome, abdominal aortic stenosis and, 44f, 928–929, 930f Midgut malrotation, 309–311, 309f–311f Mirizzi syndrome, 471–472 Mirror image artifact, 37, 37f Mitrofanoff appendicovesicostomy, 824, 825f MMIHS. See Megacystitis-microcolon-intestinal hypoperistalsis syndrome M-mode imaging, 14, 14f, 104–105, 175, 175f, 196, 199–200, 200f–201f, 202, 209, 209f, 278, 278f Monosomy X. See Turner syndrome Morgagni hernia, 274, 274f, 274t, 275, 276f MPNST. See Malignant peripheral nerve sheath tumor MRKH. See Mayer-Rokitansky-Küster-Hauser Syndrome Mucoepidermoid carcinoma, of salivary glands, 166, 166f Müllerian duct anomalies. See also Female genital tract, congenital anomalies müllerian duct cyst, 675 Multicystic dysplastic kidney (MCDK), 736, 736f, 745f, 776–777, 776f–777f Multifocal lymphangioendotheliomatosis with thrombocytopenia, 328 Multinodular goiter (nodular hyperplasia), 157–158, 158f Multipath reflection artifact. See Mirror image artifact Multiple hereditary exostoses (MHE), 252, 849f, 853 Musculoskeletal system. See also Ankle and hind foot; Bones; Elbow; Hip; Joints; Knee; Shoulder; Soft tissues; Wrist and hand normal development, 837 technique imaging approaches, 836–837, 836f patient positioning, 836 ultrasound transducer selection, 836 trauma, tendon tears, 844 vascular anomalies, 890t arteriovenous fistula, 893–894 arteriovenous malformation, 893–894, 894f congenital hemangioma, 890–891, 891f infantile hemangioma, 889–890, 890f kaposiform hemangioendothelioma, 891, 891f and Kasabach-Merritt phenomenon, 891 lymphatic malformation, 892, 893f venous malformation, 892, 892f–893f Mycobacterial infection, 145–146, 772 Mycobacterium tuberculosis lymphadenopathy, 231–232 Myelocele, 112–113 Myelomeningocele, 62, 62f, 112–113, 113f, 114, 117f, 767 Myofibromatosis, 146, 147f Myositis ossificans, 263, 843, 843f N Nabothian cyst, 719, 719f NAFLD. See Nonalcoholic fatty liver disease

989 Near-field, of ultrasound beam, 15–17, 15f–17f, 19. See also Fresnel zone NEC. See Necrotizing enterocolitis Neck benign neoplasms lipoblastoma, 147, 148f, 149 lipoma, 147, 148f, 149 myofibromatosis, 146, 147f neurofibroma, 147, 147f differentiation from malignant peripheral nerve sheath tumor, 147 congenital neck anomalies, 133–144 congenital non-vascular neck masses, 133–138, 134f–139f congenital vascular neck masses congenital hemangioma, 138 vascular malformations, 140, 144, 141f–144f imaging approaches, 128 infantile hemangioma, 138, 139f, 140 PHACES syndrome, 138 infectious and inflammatory disorders cat-scratch disease, 146, 146f histiocytosis, 146 human immunodeficiency virus infection, 146 Kawasaki disease, 146 lymphadenitis and abscess, 144–145, 144f mycobacterial infection, 145–146, 146f sarcoidosis, 146 malignant neck neoplasms lymphoma, 149, 149f neuroblastoma, 149–150, 150f rhabdomyosarcoma, 150, 151f metastatic cervical nodal disease, 149f, 150–151 neoplastic disorders, 146–151 normal development and anatomy, 128–133 anterior triangle, 128 lymph nodes, 129, 129f parathyroid glands, 130f, 131, 131f parotid gland, 131, 132f posterior triangle, 128 salivary glands, 131–133 sternocleidomastoid muscle, 128, 128f sublingual glands, 132f, 133 submandibular glands, 132, 133f Wharton duct, 132, 167 thyroid gland, 130–131, 130f technique imaging approaches, 128 patient positioning, 127 ultrasound transducer selection, 127–128 Necrotizing enterocolitis (NEC), 337, 338f patient positioning and, 305 portal venous gas and, 386, 387f Neonatal acute ischemic stroke, 78 Neonatal hepatitis syndrome, 443t, 463, 465, 467f Neonatal meningitis, 86 Nephroblastomatosis, 810, 810f Beckwith-Wiedemann syndrome and, 571 Nephrogenic rests, 810, 801f Nephronophthisis, 776–777, 777f Neurenteric cyst(s) of mediastinum, 229–230, 230f of spine, 114 Neurenteric fistula, 114 Neuroblastoma adrenal, 598, 601–602, 601t, 602f–605f, 606 Beckwith-Wiedemann syndrome and, 571

990 Neuroblastoma (cont.) biliary tree, 474–475 breast, 963 chest wall, 210, 262 differentiation from adrenal hemorrhage, 596–597 differentiation from Wilms’ tumor of kidney, 807–808 kidney, 814, 815f liver, 403 lung, 190 mediastinum, 225t, 233, 234f neck, 149–150, 150f ovary, 711 pancreas primary, 585–586 metastatic, 587 peritoneal cavity, 546t, 555 pleura, 214 retroperitoneum, 617–618, 620f scrotum, 668–669, 673 spleen, 521 Neuroendocrine tumor bile ducts, 474–475, 475f carcinoid of appendix, 333 metastases to liver, 403 pancreas, 571–572, 582–584, 584f Neurofibroma bladder, 819, 820f neck, 147, 147f pancreas, 580 paratesticular, 672 peritoneal, 546t, 547–548, 548f retroperitoneum, 617, 618f testicle, 666 Neurofibromatosis adrenal pheochromocytoma and, 606 GIST and, 303 lateral meningocele and, 116 neurofibroma of bladder and, 819, 820f, 822 neurofibroma of neck and, 147 neurofibroma of paratesticular tissues and, 672 neurofibroma of retroperitoneum and, 617, 618f neurofibroma of testicle and, 666 optic pathway astrocytoma and, 88 plexiform neurofibroma of mesentery and, 547, 548f renal artery stenosis and, 779 schwannoma of neck and, 147 Neurogenic bladder, 749f, 754, 767, 767f, 800, 824 bladder augmentation for, 767 Neuronal migration disorders gray matter heterotopia, 68, 69f lissencephaly, 68 Neuronal proliferation disorders, 58f, 68 Neutropenic colitis, 342–343, 342f NICH. See Non-involuting congenital hemangioma Niemann-Pick disease, 507 Non-accidental trauma. See also Child abuse; Trauma distal humeral epiphyseal separation and, 864, 865f duodenal hematoma and, 319 gallbladder and, 454f scrotum, 653–654 subdural fluid collection and, 74f Non-alcoholic fatty liver disease (NAFLD), 371–372, 372f Non-communicating hydrocephalus, 90 Nonfunctioning parathyroid cyst, 161 Non-Hodgkin lymphoma (NHL). See also Burkitt lymphoma; Hodgkin lymphoma; Lymphoma chest wall, 261

Index chylous effusion, 206–207 GI tract, 301, 329 kidney, 813 liver, 404 mediastinum, 226–227 neck, 149f, 150 ovary, 711 pancreas, 587 peritoneal cavity, 551 retroperitoneum, 615 spleen, 487t, 518, 518f uterus, 719 Non-involuting congenital hemangioma (NICH) of liver, 388t, 389 of skin/subcutaneous tissues, 248–249, 248t, 890, 890t Nonsteroidal anti-inflammatory drugs (NSAIDs), 504, 549, 844, 855, 877, 885 Nonthermal bioeffects, 48 NSAIDs. See Nonsteroidal anti-inflammatory drugs Nursemaid elbow. See Pulled elbow Nyquist limit(s), 30, 31, 43 O Obstructed glands of Montgomery, 950. See also Retroareolar cysts Obstructed hemivagina and ipsilateral renal anomaly (OHVIRA) syndrome, 700, 700f Obstructive hydrocephalus, 72, 87–88, 90, 92 OEIS complex. See Cloacal exstrophy OHVIRA syndrome. See Obstructed hemivagina and ipsilateral renal anomaly Omental cyst, 540 Orchitis, isolated, 644–645. See also Epididymo-orchitis Ortolani maneuver, for hip stability, 872 Oscillatory motion, 2 Osgood-Schlatter disease, 844f, 886 Ossification centers ankle, 887–888, 887f–888f calcaneal apophysis, 889 elbow, 860f hindfoot, 887, 887f humeral head, 856, 856f knee, 878, 878f long bones, 847 patella, 884, 885f pelvic bones, 870 ribs, 242, 242f spine, 104 sternum, 242, 243f, 247, 247f Ossifying renal tumor of infancy, 806 Osteochondroma/exostosis, 251–252, 252f, 253, 849f, 853–854 Osteomyelitis, 255, 850–851, 850f–851f Osteosarcoma, 190, 233, 260–262, 588f, 814, 815f Ovary(ies). See also Female genital tract anatomy, 688–689 development, 686–688 masses, 703–712 menstrual cycle and, 690–691 torsion, 713 P Pancreas acute pancreatitis acute peripancreatic fluid collections, 573, 573f Atlanta classification, revised, 572 definition, 572

Index diagnosis, 572 etiologies, 572 necrotizing pancreatitis, 575, 575f pancreaticopleural fistula, 575 pseudocysts, 573–574, 573f–574f ultrasound findings, 572, 572f vascular complications, 576, 576f acute recurrent pancreatitis, 576–577 anatomic variants lobulated parenchymal contour, 566 benign neoplasms cystic teratoma, 579–580, 589t infantile hemangioma, 579 inflammatory myofibroblastic tumor, 580 leiomyoma, 580 lipoma, 580 mucinous cystadenoma, 579 neurofibroma, 580 schwannoma, 580 serous cystadenoma, 579 chronic pancreatitis, 576–577, 576f–577f congenital abnormalities accessory pancreatic lobe, 567, 569 annular pancreas, 566–567, 566f–567f common pancreaticobiliary channel, 567, 568f congenital hyperinsulinism, 569 partial pancreatic agenesis, 567, 568f ectopic pancreas, 569 pancreas divisum, 566, 566f congenital pancreatic cyst, 569–570 cystic neoplasms of mucinous cystadenoma, 579 serous cystadenoma, 579 teratoma, 579–580, 580f genetic disorders autosomal dominant polycystic kidney disease, 571, 571f Beckwith-Wiedemann syndrome, 571 cystic fibrosis, 570, 570f Shwachman-Diamond syndrome, 570–571, 571f Von Hippel-Lindau disease, 571–572 malignant tumors acinar cell carcinoma, 584–585 ductal adenocarcinoma, 585, 585f fibrosarcoma, 587 islet cell, 582–584 kaposiform hemangioendothelioma, 586–587 lymphoma, 585, 586f metastatic disease, 587, 587f–588f neuroblastoma, 585–586 pancreatoblastoma, 580–582, 581f primitive neuroectodermal, 586 rhabdomyosarcoma, 587 solid pseudopapillary, 582, 582f normal anatomy, 564, 565f normal development, 564, 565f pancreatic transplantation, 588, 588f technique imaging approaches, 564 patient positioning, 564 ultrasound transducer selection, 564 trauma, 577–579, 577f–578f venous and lymphatic malformations, 579 Paraovarian cyst, 711–712, 712f Papillary urothelial neoplasm of low malignant potential (PUNLMP) of bladder, 818 Parapneumonic effusion, 203–204, 203f empyema, 204, 204f

991 fibrothorax, 204, 205f Parasitic infection. See also Echinococcal disease; Hydatid disease; Schistosomiasis of liver, 378–380, 379f of spleen, 498–501, 500f of small bowel, 316 of urinary tract, 772, 772f Parathyroid adenoma, 162–163, 162f Parathyroid cyst, 161–162, 161f Parathyroid glands, 128, 130f, 131, 131f. See also Hyperparathyroidism Parathyroid hyperplasia, 162 Paraurethral duct cyst, 721–722, 722f Paravertebral (posterior) compartment, of mediastinum, 221, 228f, 230 Paravertebral (posterior) mediastinal mass(es) ganglioneuroblastoma, 233–234 ganglioneuroma, 234–235 neuroblastoma, 233, 234f Parenchymal hemorrhage, of brain, 72, 75, 90 Parotid gland, 131–132, 132f, 164, 165f, 166–167, 167f Partial volume artifact, 40–41, 41f Partially involuting congenital hemangioma (PICH) of skin/subcutaneous tissues 248–249, 248t of liver, 388t, 389, 390f PASH. See Pseudoangiomatous stromal hyperplasia Passive venous congestion, of liver, 386, 386f PCOS. See Polycystic ovary syndrome Peliosis hepatis, 385, 385f Peliosis, splenic, 515–516 Pelvic inflammatory disease (PID), 716, 716f–717f Pericardial cyst, 235, 235f Peritoneal cavity. See also Peritonitis ascites chylous, 531–532, 531f exudate, 528 hemoperitoneum, 530, 531f serum-ascites-albumin gradient, 529, 529t transudate, 528 treatment, 530 ultrasound evaluation, 529, 529f–530f urine, 532, 532f benign masses, 545–551, 546t Castleman disease, 549–550, 549f desmoid tumor, 548–549, 548f inflammatory myofibroblastic tumor, 550–551, 550f infantile hemangioma, 545–546 lipoblastoma, 547 lipoblastomatosis, 547 lipoma, 546, 546f lipomatosis, 546, 547f neurofibroma, 547–548 plexiform neurofibroma, 547–548, 548f inflammation abscess, 539–540, 539f peritonitis, 535–539 localized fluid collections biloma, 533, 534f cerebrospinal fluid pseudocyst, 532–533, 533f diaphragmatic mesothelial cyst, 535, 536f pancreatic pseudocyst, 534 peritoneal inclusion cyst, 535, 535f malignant tumors, 546t, 551–555 metastatic disease adenocarcinoma, 555 germ cell tumor, 555 intracranial neoplasms, 555 neuroblastoma, 555

992 Peritoneal cavity (cont.) Wilms’ tumor, 555 primary desmoplastic small round cell tumor, 553–554, 554f lymphoma, 551, 552f Burkitt lymphoma, 551, 552f non-Hodgkin lymphoma, 551 malignant mesothelioma, 554–555 rhabdomyosarcoma, 551–553, 553f mesenteric lymphadenitis, 541–542, 541f normal anatomy, 524–528, 526f mesentery, 526, 527f–528f omentum, 526, 527f peritoneal fluid, 528, 529f peritoneum, 524–525 normal development, 524, 525f omental cyst, 540 pneumoperitoneum, 540, 540f segmental omental infarction, 540–541, 541f technique imaging approaches, 524 patient positioning, 524 ultrasound transducer selection, 524 vascular anomalies lymphatic malformation, 542, 543f–544f venous malformation, 542–543, 545f Peritoneal inclusion cyst, 712, 712f Peritonitis chemical, 537, 538f meconium, 312–313, 313f, 537, 538f, 653, 654f definition of, 535 granulomatous, 537 infective, 535–536, 537f tuberculous, 536 sclerosing encapsulating, 537–539, 539f Periventricular hemorrhagic infarction, 72, 73f Periventricular leukomalacia (PVL), 76–78, 77f–78f PFFD. See Proximal focal femoral deficiency PHACE(S) syndrome, 95–96, 138, 248, 388t PICH. See Partially involuting congenital hemangioma PID. See Pelvic inflammatory disease Pilomatricoma, 845–846, 846f Pilonidal cyst, 120–121, 121f Pilonidal sinus, 120–121 PKD1. See Polycystin 1 gene Plagiocephaly, positional, 97, 99 and SIDS, 97 Pleura anatomic variants, 199, 199f normal anatomy, 196–199, 197f–199f normal development, 197, 197f pleural masses, 210–214, 210f malignant pleural masses metastases, 214, 214f pleuropulmonary blastoma, 211–212, 212f rhabdomyosarcoma, 212–213, 213f pneumothorax, 207–210, 208f, 208t absent B-lines, 209 absent lung pulse, 209 absent lung sliding, 208–209 lung point sign, 209, 209f stratosphere/barcode signs, 209, 209f technique A-lines, 200, 200f B-lines, 200, 200f imaging approaches, 196, 196f patient positioning, 196

Index T-lines (“lung pulse” sign), 200, 201f ultrasound transducer selection, 196 Z-lines, 201, 201f Pleural effusion causes of, 201 chylous effusion (chylothorax), 206–207, 206f–207f clinical presentation, 201 complex pleural effusion, 202–203, 202f–203f parapneumonic effusion, 203–204, 203f quantification of fluid volume, 201 simple pleural effusion, 202, 202f traumatic effusion extrapleural hematoma, 206 hemorrhagic effusion, 205–206, 205f hemothorax, 205–206, 205f Pleuritic pain, 201 Pleuropulmonary blastoma (PPB), 189, 190f, 211, 212f and DICER1 mutation/syndrome, 189, 190f, 211, 212f Plexiform neurofibroma, 147, 547–548, 548f, 820f Plunging ranula, 163, 163f PNET. See Primitive neuroectodermal tumor Pneumoperitoneum, 540, 540f necrotizing enterocolitis and, 337, 338f Pneumothorax, 207–210, 208f, 208t Poland syndrome, 947 Polycystic kidney and hepatic disease 1 gene (PKHD1), 775 Polycystic liver disease, 369–370, 370f Polycystic ovary syndrome (PCOS), 724, 724f Polycystin 1 gene (PKD1), 775 Polymicrogyria, 67–68, 85. See also Post-migration disorders, of brain Polyorchidism, 637, 637f Popliteal cyst, 881, 881f Porcelain gallbladder, 449, 450f Portal hypertension, 382–383, 382t, 382f. See also Budd-Chiari syndrome; Portal vein stenosis; Portal vein thrombosis Alagille syndrome and, 469 ARPKD and, 775 Caroli disease and, 459 flow velocity and, 366 gallbladder varices and, 453, 453f Gamna-Gandy bodies and, 523, 524f hepatic fibrosis and, 372 peliosis hepatis and, 385 portal vein stenosis and, 419 schistosomiasis and, 500 sclerosing cholangitis and, 471 splenic vein thrombosis and, 576 splenomegaly and, 487t, 508, 509f ultrasound features, 375 Portal vein normal, 357f, 366 stenosis, 368, 419f, 419–420, 420f thrombosis liver cirrhosis and, 374 liver transplantation, complication of, 408t, 419, 419f pancreatitis, complication of, 529t portal hypertension, cause of, 382–383, 382t and splenomegaly, cause of, 487 umbilical vein catheterization and, 382 and varices of gallbladder, 453 Portal venous gas, 337, 386–387, 387f Posterior urethral valves (PUV), 532, 532f, 576, 675, 764–765, 764f–765f, 785, 794, 824 Post-migration disorders, of brain polymicrogyria, 68 schizencephaly, 58t, 64, 67–69, 70f Post-transplant lymphoproliferative disorder (PTLD), 405–407

Index after liver transplantation, 406f, 408t, 475f after renal transplantation, 797, 797f Power Doppler, 31–32, 32f in chronic pyelonephritis, for increased sensitivity of scar detection, 772–773 for low-flow detection, 910 in suspected carotid artery thrombosis, 904, 905f in suspected hepatic and portal vein thrombosis, 357 and motion sensitivity, 44 Premature thelarche, 723, 948, 948f PRETEXT staging system, for primary hepatic malignancies of childhood, 398 Prevascular (anterior) compartment, of mediastinum, 221 PRF. See Pulse repetition frequency Primary diaphragmatic neoplasms benign, 279–280, 279f malignant, 280, 280f, 280t Primitive neuroectodermal tumor (PNET) of brain, associated with rhabdoid tumor of kidney, 811 chest wall, 259 kidney, 812–813 pancreas, 586 Processus vaginalis canal of Nuck disorders and, 725–726 congenital hydrocele and, 650, 651f indirect inguinal hernia and, 658, 658f scrotal abscess from peritonitis and, 646 scrotal development and, 630, 630f scrotal extension of meconium peritonitis and, 653 scrotal hematocele from intraperitoneal hemorrhage and, 652 scrotal swelling from adrenal hemorrhage and, 596 scrotal urinoma from bladder rupture and, 657 spermatic cord hydrocele and, 650–651, 652f splenogonadal fusion and, 638 Prostaglandin-induced foveolar hyperplasia, 294, 295f Prostate gland. See Male genital tract, prostate and seminal vesicles Prostatitis, 678 Proximal focal femoral deficiency (PFFD), 876, 876f PRP. See Pulse repetition period Pseudoaneurysm(s) femoral, 916 hepatic artery, after liver transplantation, 418, 418f renal artery, 781, 783f after renal transplantation, 789, 791f splenic, 522 Pseudoangiomatous stromal hyperplasia (PASH), 957–958, 958f Pseudocyst(s) adrenal, 594 CSF, complication of ventriculoperitoneal shunt, 532–533, 533f gastric duplication cyst, differentiated from, 567 meconium, 312–313, 313f, 537 mesenteric cyst, differentiated from, 326 necrotizing pancreatitis, complication of, 575, 575f–576f pancreatic, complication of trauma, 578 pancreatitis and, 522, 534, 585 acute pancreatitis, complication of, 534, 572–574, 573f chronic pancreatitis, complication of, 534 pancreatic duplication cyst, differentiated from, 298–299, 570 Pseudogynecomastia, 949 Pseudomass of cauda equina nerve roots, 110 of pancreas, 566 Pseudomembranous colitis, 340–343 Pseudosinus tract, 110, 110f PTLD. See Post-transplant lymphoproliferative disorder Pubertal disorders, female genital tract

993 amenorrhea, 724 polycystic ovary syndrome, 724, 724f precocious puberty, 723 Puberty, definition, 723 Pulled elbow, 866, 866f Pulmonary abscess, 184–185, 184f Pulmonary lymphangiectasia, 188, 188f Pulmonary masses, 188–191 benign hamartoma, 189 malignant metastases, 190, 191f primary malignant pulmonary neoplasms pleuropulmonary blastoma, 189, 190f rhabdomyosarcoma, 189–190 Pulsed wave (PW) Doppler, 27, 29–30, 29f, 43f Pulse-echo technique, 2, 8 Pulse inversion imaging, 36–37, 36f Pulse repetition frequency (PRF), 9, 10f, 43f, 334, 900 Pulse repetition period (PRP), 9, 10f Pulser, 11 PUNLMP. See Papillary urothelial neoplasm of low malignant potential PUV See Posterior urethral valves PVL. See Periventricular leukomalacia PW Doppler. See Pulsed wave Doppler Pyelonephritis. See also Urinary tract infection acute, 768–769, 769f chronic, 772–773, 773f Pyloric stenosis. See Hypertrophic pyloric stenosis Pylorospasm, 293–294, 294f Pylorus, 288, 290, 293–294, 300, 305 Pyomyositis, 255, 839, 840f Pyonephrosis, 770, 770f PZT. See Lead-zirconate-titanate Q Quadrigeminal cistern, 53, 55f, 67 Quasi-static strain elastography methods, 32 R Ranula, 163, 163f Rapidly involuting congenital hemangioma (RICH) of liver, 388t, 389, 389f of skin/subcutaneous tissues, 248–249, 248t, 890, 891f Rarefaction, 3–4, 3f, 48 Rarefaction peak pressure, 48 RCC. See Renal cell carcinoma RDS. See Respiratory distress syndrome Receiver, 12–14, 13f Reflection in acoustics, 4–7, 5f–7f, 9, 24 multipath reflection artifact, 37–38, 37f–38f shadowing artifact caused by, 40, 40f–41f twinkling artifact and, 45–46, 46f Refraction, 7, 7f and grayscale artifacts, 37–38, 38f Renal agenesis, 592, 638, 675, 677, 693, 696, 700f, 741–742, 742f, 748, 759 Renal artery pseudoaneurysm, 781, 783f Renal artery stenosis, 736, 779, 780f, 781 renal transplantation and, 789 Renal artery thrombosis, 781–782, 782f renal transplantation and, 788–789, 788f Renal cell carcinoma (RCC), 571, 778–779, 804, 806, 807f, 810–811, 811f, 935

994 Renal cortical calcification, 798, 798f Renal cystic disease acquired cystic kidney disease, 779, 779f autosomal dominant polycystic kidney disease, 775–776, 776f autosomal recessive polycystic kidney disease, 775, 775f classification, 774 cystic renal dysplasia, 776, 776f glomerulocystic kidney disease, 777, 778f imaging, 775 medullary cystic disease, 777 multicystic dysplastic kidney, 736, 736f, 745f, 776–777, 776f–777f nephronophthisis, 776–777, 777f tuberous sclerosis, 778, 778f von Hippel-Lindau disease, 778, 778f Renal hypoplasia, 721, 746, 786 Renal medullary carcinoma, 812 Renal transplantation acute tubular necrosis, 791, 792f abscess, 796–797, 797f allograft types, 786 arteriovenous fistula, 789, 791f drug nephrotoxicity, 792 graft failure, 791 hematoma, 796, 796f lymphocele, 796, 796f normal renal transplant, 788, 788f posttransplant tumors, 797–798, 797f pseudoaneurysm, 789, 791f pyelonephritis, 795–796, 795f rejection, 792, 793f renal artery stenosis, 789 renal artery thrombosis, 788–789, 788f renal vein thrombosis, 789, 790f seroma, 796 surgical technique, 787, 787f ureteral obstruction, 794 urine leak, 793–794, 794f urinoma, 796 vesicoureteral reflux, 794, 795f Renal vein thrombosis (RVT), 781–783, 784f, 789, 799 renal transplantation and, 789, 790f Repetitive scrotal microtrauma, 657 Respiratory distress syndrome (RDS), 186 Retroareolar cysts, 950–951. See also Obstructed glands of Montgomery Retrocaval ureter, 752, 933–934 Retroperitoneal vessels. See Vascular imaging, retroperitoneal vessels Retroperitoneum, non-vascular disorders. See also Adrenal gland(s); Pancreas; Vascular imaging; specific vessels benign masses hemangioma, 608, 617 lipoblastoma, 617 lipoma, 617 mature teratoma, 617 neurofibroma and schwannoma, 617, 618f Ewing sarcoma, 621 extramedullary hematopoiesis, 614 fibrosis, 613–614 hemorrhage, 613, 613f infection and abscess, 611–613, 611f–612f inflammatory myofibroblastic tumor, 622 kaposiform hemangioendothelioma, 608, 622, 622f lymphadenopathy infection, 615 lymphoma, 615–616, 616f

Index metastatic disease, 616, 616f lymphatic malformations, 614, 615f malignant tumors infantile fibrosarcoma, 620 malignant germ cell tumor/immature teratoma, 620–621 rhabdomyosarcoma, 620, 621f neural crest tumors, 617–618, 619f–620f normal anatomy, 610, 610f, 611 normal development, 609 schwannoma, 617, 618f smooth muscle tumors, 621 technique imaging approaches, 609 patient positioning, 609 ultrasound transducer selection, 609 undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma), 621 venous malformations, 614 Reverberation artifact(s), 24, 38–39, 38f–39f A-lines, 175f, 176, 177t, 200, 200f B-lines, 176, 176f, 186 foreign bodies and, 265–266, 266f gas within abscess and, 539 inspissated thyroid colloid and, 154 normal trachea and, 224, 224f pneumothorax and stratosphere/barcode sign, 209, 209f pulmonary consolidation and loss of, 176, 176f, 177t Rhabdoid tumor(s) of brain, 811, 812f of kidney, 811, 812f of liver, 403 Rhabdomyosarcoma Beckwith-Wiedemann syndrome and, 571 biliary tree metastatic, 474–475 primary, 403, 473–474, 474f bladder, 678, 818, 821–822, 822f breast, metastatic, 960, 963 cervix, 720, 720f chest wall metastatic, 262 primary, 240t, 258–259 diaphragm, 279t, 280 lung, 189–190 neck metastatic, 149f, 150–151 primary, 150, 151f ovary, metastatic, 711 pancreas, 587 paratesticular, 669, 673, 673f adenomatoid tumor differentiated from, 672 fibrous pseudotumor differentiated from, 670 peritoneal cavity, 546t, 551–553, 553f pleura, 210, 212–213, 213f prostate, 678 retroperitoneal metastatic, 616 primary, 620, 621f salivary gland, 167 seminal vesicle, 678 testicle, 669 vagina, 720, 722–723, 722f müllerian papilloma differentiated from, 722 paraurethral duct cyst differentiated from, 721

Index Rheumatic disorders, 503–504, 854 macrophage activation syndrome and, 503–504 RICH. See Rapidly involuting congenital hemangioma Rib(s) fractures, 206, 240t, 264–265, 508 osseous and cartilaginous lesions, 251–255 Ring-down artifact, 38, 540, 540f Rosai-Dorfman-Destombes disease, 662 Rotavirus, 316, 340 S SAAG. See Serum-ascites albumin gradient Sacrococcygeal teratoma, 122, 123f, 124, 124f Salivary glands. See also Parotid glands; Sublingual glands; Submandibular glands benign masses infantile hemangioma, 139f, 166 lymphatic malformation, 144f, 166 congenital anomalies first branchial cleft cyst, 134f, 163 ranula, 163, 163f infectious and inflammatory disorders acute bacterial parotitis and abscess, 164–165, 164f viral (nonsuppurative), 164 recurrent and chronic chronic sialadenitis, 165, 165f malignant neoplasms acinar cell carcinoma, 166–167, 167f adenoid cystic carcinoma, 167, 167f lymphoma, 149–150 primary lymphoma (MALToma), 167 mucoepidermoid carcinoma, 166, 166f rhabdomyosarcoma, 167 sialoblastoma, 167, 167f parotid gland, 131, 132f sialolithiasis, 167–168, 168f sublingual glands, 132f, 133 submandibular glands, 132, 132f–133f Sarcoidosis cervical lymph nodes, 146 epididymitis, 644 interstitial lung disease, 186t mediastinum, 225t spleen, 487t, 502–503, 503f Scalp masses characterization of, 93 congenital scalp lesions cephalocele, 94, 94f dermoid and epidermoid cysts, 93–94, 94f extracranial birth trauma, 95, 95f high frequency linear array transducer, 92, 93f lymph node, 94 vascular scalp lesions infantile hemangioma, 95–96, 96f sinus pericranii, 96, 97f SCFE. See Slipped capital femoral epiphysis Schistosomiasis of bladder, 772, 772f of liver, 382t of spleen, 499–500, 500f Schizencephaly, 58t, 64, 67–69, 70f. See also Post-migration disorders, of brain Sclerosing cholangitis, 443t, 471, 471f, 472, 474

995 SCM. See sternocleidomastoid muscle Scrofula (tuberculous cervical lymphadenitis), 146f Scrotal and spermatic cord fluid collections, 649–652, 651f–652f Scrotum. See Male genital tract, scrotum Segmental spinal dysgenesis, 119 Segmental testicular infarction, 639t, 641–642, 662 Semilobar holoprosencephaly, 64 Seminal vesicles. See Male genital tract, prostate and seminal vesicles Septic arthritis, 850f, 851, 851f, 854, 854f, 877 Septo-optic (pituitary) dysplasia, 64–65 Sertoli cell tumors, 662t, 665, 665f Sertoli-Leydig cell tumor, 705t, 710–711, 948 Serum-ascites albumin gradient (SAAG), 529, 529t Sex chord stromal tumors, 705t, 710 Sexual maturity rating, 943 Shadowing attenuation artifact, 40, 40f–41f Shear wave speed imaging, 34 Shoulder glenohumeral dysplasia, 858–589, 858f–859f imaging approaches, 848f, 856–857, 856f–857f normal anatomy, 856, 856f patient positioning, 856 Shwachman-Diamond syndrome, 570–571, 571f Sialadenitis, 164f–165f, 165 chronic 165, 165f Sialoblastoma, 167 Sialolithiasis, 167–168, 168f Sickle-cell disease, 504–506, 505f brain, 81–84, 83t, 84f stroke and, 81–82 TCD ultrasound for, 82–84, 83t, 84f cholecystitis and, 445 extracranial stenosis of internal carotid artery and, 904 extramedullary hematopoiesis and, 516 gallbladder sludge and, 442 gallstones and, 440, 441f, 444 Gamna-Gandy bodies and, 523 pneumonia, 176f renal cortical calcification and, 798 Salmonella infection and, 316 spleen in, 487f, 491, 494, 505f, 506f Sickle-cell trait, 506, 812 renal medullary carcinoma and, 812 SIDS. See Sudden infant death syndrome Side lobe artifact, 39, 39f, 442, 444f Simple closed defect(s), of spine, 113–114, 114f–115f Simple cyst(s), of thyroid, 152, 152f Simple pleural effusion, 202, 207 Sinding-Larsen-Johansson syndrome (Jumper’s knee), 886–887, 887f Sinus histiocytosis, 662, 662t Sinusoidal obstruction syndrome (SOS), 382t, 384–385, 384f Sinus pericranii, 93, 96, 97f SIOP. See Society of Paediatric Oncology Slice thickness artifact, 24, 40–41, 41f Slipped capital femoral epiphysis (SCFE), 877, 877f Small bowel acquired obstruction intussusception ileocolic, 315–316, 315f–316f small bowel, 313–315, 314f benign masses duplication cyst, 324–326, 325f intestinal polyp, 327, 327f mesenteric cyst, 326, 326f vascular anomalies

996 Small bowel (cont.) blue rubber bleb nevus syndrome, 327–328 cutaneous angiomatosis with thrombocytopenia, 328 infantile hemangioma, 327, 328f congenital anomalies duodenal atresia, 306, 307f “double bubble” sign, 290, 306, 307f, 308 duodenal stenosis, 306 duodenal web, 306, 307f duplication cyst, 324–326, 325f ileal stenosis, 308–309 intestinal atresia, 307–308, 308f “triple bubble” sign, of jejunal atresia, 308 jejunal stenosis, 308–309 Meckel diverticulum, 323–324, 324f meconium ileus, 311–312, 312f meconium peritonitis, 312–313 meconium pseudocyst, 312–313, 313f midgut malrotation, 309–311, 309f–310f, 312f Ladd bands, 309, 309f, 312f malignant masses Hodgkin lymphoma, 329–330, 329f non-Hodgkin lymphoma, 329–330, 329f midgut volvulus, 309–310, 309f, 311f normal anatomy, 305, 306f normal development, 291f, 305 technique imaging approaches, 305 patient positioning, 305 ultrasound transducer selection, 305 wall thickening Crohn disease, 317, 318f cystic fibrosis, 321–322, 322f eosinophilic gastroenteritis, 320–321 graft-versus-host disease, 322–323, 323f hemorrhage Henoch–Schönlein purpura, 319–320, 320f trauma, 319, 319f infectious enteritis, 316–317, 317t lymphangiectasia, 321, 321f Small bowel intussusception, 313–315, 314f, 323–324, 327, 327f, 329f Society of Paediatric Oncology (SIOP), 810 and Wilms’ tumor management, 810 Society of Radiologists in Ultrasound (SRU) consensus guidelines for follow-up of ovarian cysts, 703 Soft tissues imaging approaches, 837–838, 837f–838f infectious/inflammatory disorders cellulitis, 838–839, 839f pyomyositis, 839, 840f soft tissue abscess, 839–840, 840f normal anatomy, 837, 837f muscles, 837–838, 837f–838f skin, 837, 837f subcutaneous tissues, 837, 837f tendons, 838, 838f trauma fat necrosis, 840–841, 841f foreign body(ies), 841, 842f intramuscular hematomas, 841–842 muscle hernia, 843–844, 844f muscle tears, 841–842, 842f myositis ossificans, 843, 843f tendinopathy, 844, 844f tendon tears, 844, 845f tumors

Index lipoblastoma, 846–847, 847f lipoma, 846, 846f pilomatricoma, 845–846, 846f subcutaneous granuloma annulare, 845, 845f SOS. See Sinusoidal obstruction syndrome Sound propagation, 2–4 Spatial compounding, 24, 24f Speckle-tracking algorithms, 33–34 Spectral broadening, of Doppler waveform, 28, 30f, 30–31, 43–44 in infantile hemangioma, 166 in peripheral arterial stenosis, 915 in renal artery stenosis, 779, 789 and variance, 31 Spinal cord injury epidural hematoma, 124 hematomyelia, 124 laceration and transection, 124 subdural hematoma, 124 Spinal dysraphism clinical presentation, 111 closed defect, 111, 112f, 112t, 113–116, 117f–118f cerebrospinal fluid-containing defects, 116, 118f complex, 114–116, 115f diastematomyelia, 115 neurenteric cyst, 114 neurenteric fistula, 114 lipomyelocele, 116, 117f lipomyelomeningocele, 116, 117f simple, 113–114, 114f–115f dermal sinus, 113–114, 115f, 116 filar lipoma, 113–114, 114f, 119 tight filum syndrome, 112t, 114 neonatal spine ultrasound screening, 112 open defect, 111, 111f, 111t meningocele, 112, 112t, 118f, 119f myelocele, 112–113, 113f myelomeningocele, 112–113, 112f–113f Spinal lipoma, 119, 120f Spine congenital anomalies caudal regression syndrome, 118–119, 119f dysmorphic coccyx, 110, 111f segmental spinal dysgenesis, 119 spinal dysraphism, 111–112, 111f, 111t–112t spinal lipoma, 119, 120f tethered cord, 116, 118, 118f extramedullary tumors, 122, 123f hydromyelia, 125 infectious and inflammatory disorders epidural abscess, 120 pilonidal sinus and cyst. 120, 121f neoplastic spinal disorders extramedullary tumors, 122, 123f intramedullary tumors, 122, 122f sacrococcygeal teratoma, 122, 123f–124f, 124 normal anatomy cauda equina, 105, 105f, 107f, 110 central canal, 108, 108f fatty filum, 109–110, 110f filar cyst, 109, 109f positional nerve root clumping (“pseudomass”), 110 pseudosinus tract, 110, 110f spinal cord, 107–108, 108f ventriculus terminalis, 108–109, 109f normal development, 104–105, 105f–106f pilonidal sinus and cyst, 120–121, 121f sacrococcygeal teratoma, 122–124, 123f–124f

Index syringomyelia, 125 syrinx, 125, 125f technique imaging approaches, 104 M-mode ultrasound, and nerve root pulsations, 104 patient positioning, 103–104 ultrasound transducer selection, 104 traumatic spinal disorders epidural/subdural hematoma, 124 hematomyelia, 124 lumbar puncture, 124, 124f spinal cord injury, 124 spinal cord laceration and transection, 124 Spleen acquired immunodeficiency syndrome, 501–502, 502f American Association for the Surgery of Trauma (AAST) classification of splenic injury, 508, 510f anatomic variants accessory spleen, 487, 489–490, 489f–490f lobulations and clefts, 487, 488f benign masses extramedullary hematopoiesis, 516, 517f hamartoma, 516, 516f hemangioma, 517 inflammatory myofibroblastic tumor, 516–517 Littoral cell angioma, 517–518 congenital anomalies asplenia, 491–492 hyposplenia, 491–492 nonparasitic splenic cysts, 493, 493f polysplenia, 491–492, 492f splenogonadal fusion, 493, 638f splenopancreatic fusion, 493–494 wandering spleen, 490, 491f contrast-enhanced ultrasound of peritoneal cavity, 524 of spleen, 482, 490, 494–495, 496f, 511, 512f, 520f Gamna-Gandy bodies, 500, 508, 523, 524f granulomatosis with polyangiitis, 504, 537 hemoglobinopathies, 504–506, 505f–506f infection Epstein-Barr viral infection, 498, 498f fungal abscess, 494–496, 495f–497f parasitic infection, 498–501 Babesiosis, 500–501 Echinococcus granulosus infection, 499 daughter cysts, 499 hydatid cysts, 499 Leishmaniasis, 501 Malaria, 499 Schistosomiasis, 499–500, 500f pyogenic abscess, 494, 494f tuberculous infection, 497, 497f inflammatory disorders rheumatic disorders, 503–504, 504f sarcoidosis, 502–503, 503f Langerhans-cell histiocytosis, 521–522, 521f–522f lysosomal storage diseases, 506–507, 506f–507f Gaucher disease, spleen and, 506–507, 506f–507f malignant tumors angiosarcoma, 520–521 kaposiform hemangioendothelioma, 521 leukemia, 519, 520f lymphoma, 518–519, 518f–520f metastatic disease neuroblastoma, 521 normal anatomy, 482, 484, 485f–486f, 486

997 normal development, 482, 484f pancreatitis, complications of, 522, 523f peliosis, 515–516 portal hypertension, 508, 509f sarcoidosis, 502–503, 503f splenomegaly, causes of, 486, 487t splenosis, 511, 513f technique imaging approaches, 482, 483f patient positioning, 482 ultrasound transducer selection, 482 trauma, 508–511, 510f–512f CEUS, 509, 511, 512f FAST scan, 508 vascular anomalies kaposiform lymphangiomatosis, 513, 515 lymphatic malformation, 511–513, 514f venous malformation, 513, 515f Splenogonadal fusion, 493, 638, 638f Splenomegaly, 482, 486, 487t, 497 Splenosis, 511, 513f SRU. See Society of Radiologists in Ultrasound SSWE. See Supersonic shear wave elastography Sternocleidomastoid muscle (SCM), 128, 130–131, 134–135, 138, 139f, 902, 903f, 906, 907f Stomach. See also Gastrointestinal tract acquired obstruction gastric volvulus, 294–296, 296f hypertrophic pyloric stenosis, 292–293, 292f–293f prostaglandin-induced foveolar hyperplasia, 294, 295f pylorospasm, 293–294, 294f, 295t benign masses focal foveolar hyperplasia, 300 gastric bezoar, 301, 302f gastric duplication cyst, 298–300, 299f–300f gastric lipoma, 300 gastric teratoma, 300 inflammatory myofibroblastic tumor, 300–301 other benign masses, 301 congenital anomalies gastric atresia, 290 gastric diaphragm (antral web), 292 microgastria, 290, 292 gastric wall thickening chronic granulomatous disease, 298, 298f eosinophilic gastroenteritis, 297–298 gastritis, 297, 297f Ménétrier disease, 297 imaging approaches, 289–290, 289f malignant tumors gastrointestinal stromal tumor, 303, 304f leiomyosarcoma, 303 lymphoma, 301–302, 303f primary gastric adenocarcinoma, 303 normal anatomy, 285f, 290 normal development, 290, 291f technique imaging approaches, 289, 290 patient positioning, 288 ultrasound transducer selection, 289 STOP. See Stroke Prevention in Sickle Cell Anemia Stroke Prevention in Sickle Cell Anemia (STOP), 82, 83t Subacute (De Quervain) thyroiditis, 159, 160f Subclavian artery, 45f, 128, 244, 902, 902f, 910f, 927 Subcutaneous granuloma annulare, 845, 845f Subdural hemorrhage, 74–75

998 Subgaleal hematoma, 95, 95f Sublingual glands, 132f, 133 Submandibular glands, 128, 132f, 133f, 164, 167, 168f Subpial hemorrhage, 75, 75f Sudden infant death syndrome (SIDS) and positional plagiocephaly, 97 Superficial femoral artery, 910, 913–914, 921f Superior sagittal sinus thrombosis, 82f Supersonic shear wave elastography (SSWE), 35, 35f Surfactant deficiency disease, 176, 186, 187f Syringomyelia, 113, 125 Syrinx, 61, 112t, 116, 121, 125 T Talocrural joint. See Ankle Tanner staging, of breast development, 943, 944t, 945f–946f, 946–947 Tardus-parvus waveform(s) in hepatic artery after liver transplantation, 408t, 415, 417, 417f stenosis, 408t, 417, 417f thrombosis, 408t, 415t in peripheral artery stenosis, 915, 915 in renal artery stenosis, 779 in renal artery stenosis after renal transplantation, 789 TCC. See Transitional cell carcinoma TCD. See Transcranial Doppler Teratoma(s) adnexal torsion and, 713 adrenal, 608, 608f of brain, 88 cervical, 136–137, 137f gastric, 300 mediastinal, 225–226, 226f ovarian, 705t, 706, 706f–707f pancreatic, 579–580, 580f retroperitoneal, 617, 620 sacrococcygeal, 122, 124, 123f–124f testicular, 662–663, 662t, 664f Terminal myelocystocele, 112t, 116 Testicular ectopia, 636f, 637–638 Testicular hypoplasia, 637, 637f Testicular mass(es) leiomyoma, 668 non-neoplastic lesions adrenal rests, 660–661, 661f hamartoma, 661 Leydig cell hyperplasia, 661 simple cyst, 661–662, 661f sinus histiocytosis, 662 primary testicular tumors, 662t adenomatoid , 668 capillary hemangioma, 667, 667f choriocarcinoma, 664 embryonal carcinoma, 663–664 epidermoid cyst, 666, 667f germ cell, 662, 663f gonadoblastoma, 663 leiomyoma, 668 lipoma, 667 seminoma, 663 stromal tumors, 665, 665f granulosa cell, 665, 666f Leydig cell, 665, 665f Sertoli cell, 665, 665f teratocarcinoma, 664 teratoma, 663, 664f

Index ultrasound appearance, 662, 662t yolk sac tumors, 662–663, 664f secondary testicular tumors carcinoid, 669 Langerhans-cell histiocytosis, 669 leukemia, 668 lymphoma, 668 neuroblastoma, 668–669 retinoblastoma, 669 rhabdomyosarcoma, 669 Wilms’ tumor, 669 Testicular microlithiasis, 652–653, 653f testicular tumors and, 653 Testicular regression syndrome, 636–637 Testicular torsion, 639–641, 639t, 640f–642f. See also Acute scrotal pain Testis-determining factor, 686, 687 Tethered cord, 113–114, 114f, 115f, 116–118, 118f Thalamo-occipital distance, 92, 92f Thalamus, 53, 56, 56f, 57–58, 58f, 59, 78, 80f, 86f, 88, 92, 92f Thecoma-fibroma, of ovary, 710 Thermal bioeffect(s), 47–48 Thermal index (TI), 48 THI. See Tissue harmonic imaging Thoracic skeleton, 241, 243 normal anatomy, 241, 243 normal development, 241–244 Three-dimensional (3D) ultrasound, 25–26, 25f, 52, 274, 685f, 686 Three-dimensional ultrasound artifacts, 47 Thrombosis. See also Deep vein thrombosis aorta, 927–928, 929f carotid artery, 902–905, 905f hepatic artery, after liver transplantation, 408t, 410, 414, 415, 416f IJV, central line placement causing, 906, 908, 909f IVC, 934–936, 935f–936f after liver transplantation, 408t, 422, 422f portal vein, 374, 382–383, 382t, 453, 453f, 487t, 529t after liver transplantation, 408t, 418–419, 419f after umbilical vein catheterization, 382 renal artery, 781, 782f after renal transplantation, 788–789, 788f renal vein, 781–783, 784f calcifications, 784f, 799 after renal transplantation, 789, 790f splenic vein, pancreatitis complicated by, 522, 523f, 576, 576f venous sinus, 81, 82f Thymus anterior mediastinal masses and, 225 cervical extension, 135f, 138, 138f ectopic, 138, 138f, 224f, 225t glands and, 131, 131f lymphoma, 226 normal anatomy, 220–221, 223, 223f normal development, 130f ultrasound imaging of, 220 Thyroglossal duct cyst, 133, 133f, 134f Thyroid cancer, 152–153, 155, 156f, 156t Thyroid gland congenital anomalies dysgenesis, 151–152, 151f dyshormonogenesis, 152 diffuse parenchymal lesions autoimmune, 159–161 Graves’ disease, 159–160, 160f congenital goiter, 158f fetal goiter, 158

Index fetal hypothyroidism, 157–158 Hashimoto thyroiditis, 160–161, 161f infectious thyroiditis acute suppurative (bacterial), 159 subacute (De Quervain), 159, 160f multinodular goiter (nodular hyperplasia), 157–159, 158f focal lesions cystic lesions colloid cysts, 152, 152f complex (hemorrhagic) cysts, 152, 153f simple cysts, 152, 152f solid lesions, 152–157, 154f–157f, 156t American College of Radiology (ACR) TI-RADS criteria, 153 benign follicular adenoma, 152, 154, 154f hyperplastic (adenomatous) nodules, 154–155, 155f malignant lesions lymphoma, 157, 157f thyroid cancer, 155–156, 156f, 156t Thyroid Imaging Reporting and Data System (TI-RADS), 153 Thyroid inferno, 160 Tibial hemimelia, 882, 882f Tietze syndrome, 253 Tight filum syndrome, 112t, 113–114 TI-RADS. See Thyroid Imaging Reporting and Data System Tissue harmonic imaging, 24. See also Harmonic imaging Tissue vibration artifact, 45 and arteriovenous fistula, 45f, 784, 785f, 917, 918f, 918t and renal artery stenosis, 789 TORCH infections and neonatal hepatitis, 463 and neonatal/infant brain, 84, 85f Torsion, testicular. See Testicular torsion Transcranial Doppler (TCD) ultrasound, for sickle-cell disease, 82–84, 83t, 84f Trachea normal anatomy, 221, 222f, 224, 224f normal development, 174, 220 Transducer, 12, 12f. See also specific organs array, 19–22, 20f–22f broad bandwidth, in harmonic imaging, 24 mechanical, 14–19, 15f–19f selection of, 22–23, 22f Transient tachypnea of the newborn (TTN), 186, 187f Transitional cell carcinoma, of bladder, 822–823, 823f Transmit beamformer, 11, 11f, 12, 19 Transmitter, 11–12, 29 Trauma. See also Child abuse; Foreign body(ies); Non-accidental trauma; Pseudoaneurysm(s) adrenal hemorrhage and, 597 apophyseal avulsion, 864, 865f, 889, 889f arteriovenous fistula of kidney, 783–784, 785f of liver, 366 of neck 140 ascites chylous, 531, 531f urine, 532 biliary tract, 472–473 biloma, 533, 534f birth chylous effusion, 206–207 cranial vault and scalp, 93, 95, 95f diaphragmatic dysfunction and, 278 intracranial, extra-axial hemorrhage, 70, 72, 74–75, 74f–75f

999 fibromatosis colli and, 138, 139f parenchymal hemorrhage, of brain, 75 spine, 124 venous sinus thrombosis, 81 bladder, 802–803 CEUS and, 802f chest wall, 240t, 262–265, 263f–264f foreign body(ies), 265–266, 265f–266f classic metaphyseal lesion, 852, 853f diaphragm eventration, acquired, 277 phrenic nerve injury, 278 rupture, 280 distal humeral epiphyseal separation, 864, 865f duodenum, 319, 319f epididymitis/epididymo-orchitis, 644 epiphyseal separation, 851–852, 852f fat necrosis, 840–841, 841f Fournier gangrene, as complication of, 649, 650f gallbladder, 453, 454f hemoperitoneum, 530 kidney, 801–802 CEUS and, 802, 802f liver blunt abdominal, 380, 380f–381f e-FAST and, 380 umbilical vein catheterization and, 380–382, 381f meniscal tears, 885–886, 886f pancreas, 577–579, 577f–578f pancreatitis and, 572–573 patellar tendon Osgood-Schlatter disease, 844f, 886 Sinding-Larsen-Johansson syndrome, 886–887, 887f peritoneal inclusion cyst, 535, 535f pleural effusion and, 205–207, 205f renal artery, 781, 783f renal vein, 781–783 retroperitoneum, 613 scrotum, 653–657, 654f–656f hematocele, 651–652 slipped capital femoral epiphysis, 877–878, 877f soft tissues cellulitis, 838–839, 839f foreign body(ies), 841, 842f muscle tears/intramuscular hematomas, 841–842, 842f myositis ossificans, 843, 843f pyomyositis, 839, 840f tendon tears, 844, 845f spine lumbar puncture, 103, 124, 124f spinal cord, 124 spleen, 508–511, 509f–512f CEUS and, 482 cyst and, 493 FAST and, 508 rupture, 505 splenosis and, 511, 513f testicle torsion, as etiology for, 640 vagina epidermal inclusion (epidermoid) cyst, 721 “Triple bubble” sign, of jejunal atresia, 308 Trisomy 21 annular pancreas, associated with, 567, 567f delayed closure of anterior fontanelle, associated with, 52 duodenal atresia, associated with, 306

1000 Trisomy (cont.) duodenal web, associated with, 306 enlarged prostatic utricle, associated with, 675 gastric atresia, associated with, 290 lymphangiectasia, diffuse, associated with, 321 splenopancreatic fusion, associated with, 493 TTN. See Transient tachypnea of the newborn Tuberous sclerosis, 779, 810 angiomyolipoma and, 804, 804f cysts of kidney and, 778, 778f glomerulocystic disease of kidney and, 777 hamartoma of spleen and, 516 renal artery stenosis and, 779 renal cell carcinoma and, 810 Turner syndrome, 140, 663, 701, 701f, 707, 745 Twinkling artifact, 45–46, 46f, 199, 312, 441, 451, 469f, 600f, 799, 801f calcified adrenal ganglioneuroblastoma and, 600f calcified meconium pseudocyst and, 312 choledocholithiasis and, 469f gallstones and, 441, 441f renal stones and, 42f, 45–46, 46f ureteral stone and, 801f Two-dimensional array transducers, 25–26, 26f U UCA. See Ultrasound contrast agents UDCA. See Ursodeoxycholic acid Ulcerative colitis, 317, 337, 338f, 339, 471f, 535f Ultrasound air bronchogram, 176, 177f, 177t, 183, 188, 599 Ultrasound contrast agents (UCA), 35–36, 36f, 257, 358, 802 microbubbles, 35–37, 36f and cavitation, 48 Ultrasound safety nonthermal bioeffects, 48 regulations and policies, 48 thermal bioeffects, 47–48 Umbilical artery aortic thrombosis and catheterization of, 927, 928 lower extremity development and, 913 renal artery thrombosis and catheterization of, 17 Umbilical vein liver development and, 360, 361f, 362, 362f. 365f perforation from malpositioned catheter in, 380–382, 381f portal hypertension as complication of catheterization, 382 portal vein atresia and, 368 portal venous gas secondary to catheterization, 386 recanalization in portal hypertension, 382, 383f Umbilical vein catheter (UVC), 380–382, 381f Undifferentiated embryonal sarcoma, 389t, 392, 402, 402f UPJ. See Ureteropelvic junction UPJO. See Ureteropelvic junction obstruction Upper extremity arteries anatomy, 913, 913f development, 913 subclavian artery, 913, 913f veins anatomy, 922, 922f development, 922 Urachal anomalies patent urachus, 757, 757f umbilico-urachal sinus, 758 urachal cysts, 758, 758f vesicourachal diverticulum, 757, 758f

Index Ureter acquired ureteral obstruction extrinsic compression, 767 intraluminal obstruction, 766–767, 767f bulking agents, as treatment for vesicoureteral reflux, 755, 756f contrast-enhanced voiding urosonography, 337, 740f–742f, 755, 755f, 765, 766f, 768, 794 congenital ureterovesical obstruction, 751 ectopic ureter, 752, 752f–753f ectopic ureterocele, 752 normal anatomy, 738, 738f primary ureteral tumors, 815–816 fibroepithelial polyp, 815 retrocaval ureter, 752, 933–934 secondary ureteral tumors, 816, 816f Wilms’ tumor extension, 816, 816f ureteral jets, 738, 739f ureteropelvic junction obstruction, 746–748, 748f urinary tract dilation classification, 746, 747f urothelial tumor, 816 vesicoureteral reflux, 752–755, 754f Ureteropelvic junction, 738 Ureteropelvic junction obstruction, 746–748, 748f Ureterovesical junction, 738, 801f Ureterovesical junction obstruction. See Congenital ureterovesical obstruction Urethra anterior urethral valves, 765–766 female urethra, 741, 741f male urethra, 741, 741f–742f normal anatomy, 740–741 posterior urethral valves (PUV), 764–765, 764f–766f urethral duplication, 766 urethral polyp, 824 Urinary diversion, 759, 771, 800, 824–825, 825f Urinary tract anatomic variants bladder bladder ears, 740, 740f kidney accessory renal artery, 736–737, 737f circumaortic left renal vein, 738, 738f compensatory hypertrophy, 736, 736f compound calyx, 736, 736f dromedary hump, 735, 735f fetal lobulations, 734, 734f hypertrophied column of Bertin, 735, 735f junctional parenchyma defect, 735, 735f retroaortic left renal vein, 737, 737f calcification dystrophic calcification, 799, 799f medullary nephrocalcinosis, 798, 798f renal cortical calcification, 798, 798f renal vein thrombosis calcifications, 784f, 799 urinary stasis, 799, 800f congenital anomalies bladder agenesis, 762, 763f cloacal exstrophy, 759 cloacal malformation, 760–761, 761f diverticula, 758, 759f duplication, 761–762, 762f exstrophy, 758, 760f megacystis-microcolon-intestinal peristalsis syndrome, 763 prune-belly syndrome, 762–763, 763f renal collecting system and ureter

Index calyceal diverticulum, 750, 751f congenital infundibulopelvic stenosis, 748–749, 750f congenital megacalyces, 748, 748f congenital ureterovesical junction obstruction, 751, 751f ectopic ureter, 752, 752f–753f ectopic ureterocele, 744f, 752 retrocaval ureter, 752, 933–934 ureteropelvic junction obstruction, 746–748, 748f ureteropelvic junction obstruction and crossing vessel, 748 vesicoureteral reflux, 752, 754–755, 754f contrast-enhanced ultrasound diagnosis of, 755, 755f imaging of endoscopically placed bulking agents, 755, 756f anomalies of renal number, position, fusion and growth crossed renal ectopia, 744, 745f horseshoe kidney, 745, 746f pancake kidney, 745–746 renal agenesis, 741–742, 742f renal duplication, 742–743, 743f–744f renal hypoplasia, 746 simple ectopia, 744, 745f supernumerary kidney, 743–744, 744f anomalies of urethra anterior urethral valves, 765–766 posterior urethral valves, 764–765, 764f–765f contrast-enhanced ultrasound diagnosis of, 765 urachal anomalies, 755–758, 756f–757f patent urachus, 757, 757f umbilico-urachal sinus, 758 urachal cyst, 758, 758f vesicourachal diverticulum, 757, 758f urethral duplication, 766 metanephric blastema, 731 normal anatomy bladder, 738–739, 739f kidney infant, 734, 734f older child and adolescent, 734, 734f ureter, 738 ureteral jets, 738, 739f urethra, 740–741, 741f–742f female, 741, 741f–742f male, 741, 741f normal development, 731, 731f–733f technique imaging approaches, 730 contrast-enhanced ultrasound, 730–731 elastography, 731 patient positioning, 730 ultrasound transducer selection, 730 trauma bladder, 802–803, 802f contrast-enhanced ultrasound diagnosis, 801–802, 801f renal, 801 urinary stasis, 799, 800f urogenital ridge, 731 urorectal septum, 731 Urinary tract dilation (UTD) classification, 746, 747f Urinary tract infection (UTI) acute pyelonephritis, 768–769, 769f chronic pyelonephritis, 772–773, 773f cystitis, 773–774, 774f fungal infection, 770–771, 771f imaging evaluation, 768, 768t opportunistic infection, 772

1001 parasitic infection, 772, 772f prevalence, 768 pyonephrosis, 770, 770f renal abscess, 769–770, 770f xanthogranulomatous pyelonephritis, 773, 774f Urolithiasis bladder stones, 767, 800, 801f causes, 799 color Doppler twinkling artifact and, 799 renal stones, 799, 800f, 801f risk factors, 800 ureteral jet and UVJ stone, 800, 801f Urothelial carcinoma, 822–823 Ursodeoxycholic acid (UDCA), and treatment for gallstones, 443 UTD classification. See Urinary tract dilation UTI. See Urinary tract infection UVC. See Umbilical venous catheter UVJ. See Ureterovesical junction UVJO. See Ureterovesical junction obstruction V VACTERL and anorectal malformations, 335 and duodenal atresia, 306 Vagina benign tumors Bartholin cyst, 721 fibroepithelial polyp, 722 Gartner duct cyst, 720–721, 721f inclusion cyst, 721 müllerian papilloma, 722 paraurethral duct cyst, 721–722, 722f foreign body, 723, 723f malignant tumors clear cell adenocarcinoma, 722–723 endodermal sinus tumor, 722–723 rhabdomyosarcoma, 722, 722f müllerian agenesis and, 692, 692f normal anatomy, 686f–687f, 687–690 Valsalva maneuver common bile duct size and, 456 deep vein thrombosis and, 922t, 925 inguinal hernia and, 630, 657 internal jugular vein and, 900, 906, 908 spermatic cord hydrocele and, 650 varicocele and, 630, 659–660, 659f–660f venous malformations and, 140, 250, 892 Varicocele, 659, 659f intratesticular varicocele, 660, 660f Vascular anomaly(ies). See also specific organs ISSVA classification, 889, 890t overview, 889 vascular malformations arteriovenous fistula, 893–894 arteriovenous malformation, 893–894, 894f lymphatic malformation, 892, 893f venous malformation, 892, 892f–893f vascular tumors congenital hemangioma, 890–891, 891f infantile hemangioma, 889–890, 890f kaposiform hemangioendothelioma, 891, 891f Vascular disorders, of brain high flow malformations, 90 low flow malformations, 90

1002 Vascular imaging extremities arteries anatomic variants, 914 aneurysm, 916, 918t arteriovenous fistula, 916–917, 918f, 918t grayscale imaging, 910, 912 lower extremity normal anatomy,913–914, 914f normal development, 913 pseudoaneurysm, 916, 917f, 918t stenosis and thrombosis, 914–916, 915f, 916t technique imaging approaches, 910, 910f–912f patient positioning, 909–910 ultrasound transducer selection, 910 upper extremity normal anatomy, 913, 913f normal development, 913 veins anatomic variants, 923, 924f deep vein thrombosis acute, 923, 925–926, 925f causes, 923 chronic, 926–927, 926f lower extremity normal anatomy, 922–923, 923f–924f normal development, 922 technique imaging approaches, 919–920, 920f–921f, 922, 922t patient positioning, 918 ultrasound transducer selection, 918–919, 919f upper extremity normal anatomy, 922, 922f normal development, 922 neck vessels carotid artery anatomic variants, 902 aneurysm, 905 color and power Doppler imaging, 900–901, 900f common carotid artery, 130, 148f, 900–901, 900f, 904f dissection, 905–906 external carotid artery, 902, 904f frequency spectrum, 902, 903f intima-media thickness, 902, 903f internal carotid artery, 63, 83, 83f, 900f, 901 normal anatomy, 902, 902f–904f normal development, 901 subclavian artery, 45f, 128, 244, 468, 902, 910f, 913, 927 thrombosis and stenosis, 902–904, 905f internal jugular vein anatomic variants, 906, 907f aneurysm, 908 development, 906 jugular vein phlebectasia, 900f, 906, 908f normal anatomy, 901f, 906, 907f normal development, 906 stenosis, 908 thrombosis, 906, 908, 909f venous aneurysm, 908 technique imaging approaches, 900–901, 900f–901f patient positioning, 899 ultrasound transducer selection, 899–900 retroperitoneal vessels aorta

Index aneurysm, 929–931, 930f dissection, 931, 931f normal anatomy, 927, 928f–929f normal development, 927 stenosis, 928–929, 930f thrombosis, 927–928, 929f inferior vena cava duplication, 934 interruption, 933, 934f left-sided, 934, 935f normal anatomy, 931–933, 931f–933f normal development, 931 retrocaval ureter, 752, 933–934 thrombosis, 934–936, 935f–936f May-Thurner syndrome, 936 technique imaging approaches, 927 patient positioning, 927 ultrasound transducer selection, 927 VACTERL association, 306, 335 VATER association, 116 Vein of Galen malformation (VOGM), 90, 91f Veno-occlusive disease. See Sinusoidal obstruction syndrome Velocity, 27 Venous malformation(s) (VMs). See also Blue rubber bleb nevus syndrome bladder, 816, 817f breast, 954 chest wall, 248t, 250, 250f GI tract, 327 musculoskeletal system, 890t, 892, 892f neck, 140, 143f peritoneal cavity, 542, 545f scalp, 89 scrotum, 671 spleen, 487t, 513, 515f Venous sinus thrombosis, 81, 82f Ventral induction disorders corpus callosum, 65–67, 66f–67f Dandy-Walker syndrome, 67–68, 67f holoprosencephaly, 63–64, 64f septo-optic dysplasia, 64–65, 65f Ventricles, 59–60, 59f–60f Ventriculus terminalis (fifth ventricle), 108–109, 109f Vesicoureteral reflux (VUR), 742–743, 743f, 752–755, 754f–755f, 759, 794, 795f VHL. See von Hippel-Lindau disease Viral hepatitis, 375, 375f Viral (nonsuppurative) inflammation, of salivary glands, 164, 164f Virginal hypertrophy of breast, 948 Visceral (middle) compartment, of mediastinum, 221 VOGM. See Vein of Galen malformation von Hippel-Lindau disease (VHL), 571–572 pheochromocytoma and, 606–607, 607f renal cell carcinoma and, 778, 810 renal cysts in, 778, 778f serous cystadenoma of pancreas and, 579 testicular cyst and, 661 W WAGR syndrome, 806, 810 Walker-Warburg syndrome, 67 “Wall echo shadow” (WES) sign, of cholelithiasis, 441, 442f Wall filter, 29, 30, 32, 42, 42f, 44, 174, 334, 910 Wandering spleen, 490, 491f

Index Waveform(s). See also Tardus-parvus waveform(s) aliasing and, 43 in adnexal torsion, 713, 713f of aorta, normal, 927, 929f in aortic stenosis, 928–929, 930f in aortic thrombosis, 927, 929f arterial, normal, 30f, 84f, 357, 357f, 483f, 634, 634f, 902, 903f–904f, 910, 910f–912f in arterial stenosis of extremity, 915, 915f in arteriovenous fistulas, 140, 142f, 784, 785f, 893 in arteriovenous malformations, 140, 141f, 671, 893, 894f in deep vein thrombosis of extremity, 923, 924f–925f, 925–926 hepatic vein in Budd-Chiari syndrome, 383, 383f in passive venous congestion, 386, 386f obstruction after liver transplantation, 420 in epididymitis/epididymo-orchitis, 639t of IVC, normal, 933, 933f in IVC thrombosis, 935 of liver vasculature after transplantation, 408t, 412 in internal jugular vein thrombosis, 908, 909f in pseudoaneurysm, 916–917, 917f in renal vein thrombosis after renal transplantation, 789, 790f in splenic vein thrombosis, 522, 523f in testicular torsion, 641, 642f in vascular masses, 93, 95–96, 96f–97f, 248, 248t, 249f, 817f, 890, 892, 892f venous, normal, 357, 357f, 367, 483f, 634, 635f, 919–920, 920f–921f in venous malformations, 140, 143f Wavelength, and medical applications of ultrasound, 2, 2f Weigert-Meyer rule, 742, 752 Wegener granulomatosis. See Granulomatosis with polyangiitis WFUMB. See World Federation for Ultrasound in Medicine and Biology Wharton duct, 132, 167 Whirlpool sign of adnexal torsion, 713 of apple peel intestinal atresia, 308, 310 of midgut volvulus, 310, 311f of segmental midgut volvulus, 310 of testicular torsion, 640 Wilms’ tumor, 40f, 803, 806–808, 808f–809f, 810 Beckwith-Wiedemann syndrome and, 571 differentiation from neuroblastoma, 807–808 metastases biliary tree, 474 liver, 403 lung, 190, 191f

1003 ovary, 711 peritoneal cavity, 546t, 555 pleura, 214, 214f retroperitoneal lymph nodes, 616 testicle and scrotal structures, 669, 673 ureteral extension of, 816, 816f nephroblastomatosis, and 810, 810f nephrogenic rests and, 810, 810f renal biopsy and, 810 screening of contralateral kidney, 807, 809f tumor invasion of renal vein and inferior vena cava, 807, 809f, 936f Wolman disease, 594 World Federation for Ultrasound in Medicine and Biology (WFUMB), 48 Wrist and hand normal anatomy, 866, 866f carpal boss, 869, 869f ganglia, 868, 868f giant cell tumor of the tendon sheath, 869, 869f imaging approaches, 867, 867f patient positioning, 867 X Xanthogranulomatous adrenalitis, 595 Xanthogranulomatous cholecystitis, 449 Xanthogranulomatous pyelonephritis, 773, 774f Y Yersinia, 316, 340 “Yin-yang” pattern of pseudoaneurysms, 918t of hepatic artery, in liver transplantation, 408, 418, 418f of peripheral arteries, 916, 917f of renal artery, 781, 783f and renal transplant biopsy, 789, 791f Yolk sac tumor diaphragm, 279t, 280, 280f ovary, 705t, 706, 708, 708f testicle, 662t, 662–663, 664f Z Zellweger syndrome, 68, 777 Zika virus, 86 Zona fasciculata, 589, 590f, 591f Zona glomerulosa, 589, 590f, 591f Zona reticularis, 589, 590f, 591f