Pediatric Surgery. General Principles and Newborn Surgery 9783662435878, 9783662435885, 9783662435892

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Prem Puri Editor

Pediatric Surgery General Principles and Newborn Surgery

Pediatric Surgery

Prem Puri Editor

Pediatric Surgery General Principles and Newborn Surgery

With 487 Figures and 114 Tables

Editor Prem Puri Department of Pediatric Surgery Beacon Hospital Dublin, Ireland School of Medicine and Medical Science and Conway Institute of Biomedical Research University College Dublin Dublin, Ireland

ISBN 978-3-662-43587-8 ISBN 978-3-662-43588-5 (eBook) ISBN 978-3-662-43589-2 (print and electronic bundle) https://doi.org/10.1007/978-3-662-43588-5 © Springer-Verlag GmbH Germany, part of Springer Nature 2020 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-Verlag GmbH, DE, part of Springer Nature. The registered company address is: Heidelberger Platz 3, 14197 Berlin, Germany

To my brother, Kailash, for his love, support, and inspiration throughout my life and career.

Preface

During the past two decades, major advances in prenatal diagnosis, imaging, anesthesia, and intensive care, as well as the introduction of new surgical techniques including minimally invasive surgery and robotic technology, have radically altered the management of newborns, infants, and children with surgical conditions. In recent years, important basic science advances in the fields of regenerative medicine and tissue engineering, pharmacotherapy, genetics, immunology, embryology, and developmental biology offer hope of the translation of basic science discoveries to new clinical therapies for children in the future. Pediatric Surgery provides an authoritative, comprehensive, and up-to-date international reference on the surgical management of both common and rare diseases in infants and children, written by the world’s foremost experts. The vast amount of information included in Pediatric Surgery is divided into three volumes, to be published separately: General Principles and Newborn Surgery; General Pediatric Surgery, Tumors, Trauma and Transplantation; and Pediatric Urology. There are three different publication formats of the reference works: (1) printed book, (2) a static e-version on SpringerLink that mirrors the printed book, and (3) a living reference also on SpringerLink that is constantly updateable, allowing the reader to rapidly find up-to-date information on a specific topic. Each chapter is organized in the form of a welldefined and structured review of the topic that allows readers to search and find information easily. General Principles and Newborn Surgery has 85 chapters focusing on general principles and newborn surgery. The first 38 chapters are devoted to general principles including important topics such as fetal counseling for congenital malformations, surgical safety in children, innovations in minimally invasive surgery, fast-track pediatric surgery, ethical considerations in pediatric surgery, childhood obesity, surgical problems of children with physical disabilities, clinical research and evidence-based pediatric surgery, tissue engineering and stem cell research, patient- and family-oriented pediatric surgical care, and surgical implications of human immunodeficiency virus infection in children. The remaining 47 chapters in General Principles and Newborn Surgery are devoted to the management of congenital malformations in the newborn, each chapter providing a step-by-step detailed practical guide on the operative approach including high-quality color illustrations to clarify and simplify various operative techniques. vii

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Preface

My hope is that Pediatric Surgery will act as a reference book for the management of childhood surgical disorders, providing information and guidance to pediatric surgeons, pediatric urologists, neonatologists, pediatricians, and all those seeking more detailed information on surgical conditions in infants and children. I wish to thank most sincerely all the contributors from around the world for their outstanding work in the preparation of this innovative international reference book on the management of surgical conditions in infants and children. I also wish to express my gratitude to Dr. Julia Zimmer, Dr. Hiroki Nakamura, and Dr. Anne Marie O’Donnell for their help in the preparation of this book. I wish to thank the editorial staff of Springer, particularly Ms. Audrey Wong-Hillmann and Ms. Nivedita Baroi, for all their help during the preparation, production, and publication of this important reference book. Dublin, Ireland January 2020

Prem Puri

Contents

Volume 1 Part I

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1

Embryology of Congenital Malformations Dietrich Kluth and Roman Metzger

..............

3

2

The Epidemiology of Birth Defects . . . . . . . . . . . . . . . . . . . . . Edwin C. Jesudason

35

3

Prenatal Diagnosis of Congenital Malformations . . . . . . . . . Tippi C. MacKenzie and N. Scott Adzick

49

4

Fetal Counseling for Congenital Malformations . . . . . . . . . . Kokila Lakhoo

65

5

Anatomy of the Infant and Child . . . . . . . . . . . . . . . . . . . . . . Mark D. Stringer

83

6

Perinatal Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Carlos E. Blanco and Eduardo Villamor

7

Fetal Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Aliza M. Olive, Aimee G. Kim, and Alan W. Flake

8

Specific Risks for the Preterm Infant . . . . . . . . . . . . . . . . . . . 137 Emily A. Kieran and Colm P. F. O’Donnell

9

Pediatric Clinical Genetics . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Andrew J. Green and James J. O’Byrne

10

Transport of Sick Infants and Children . . . . . . . . . . . . . . . . . 167 Julia Zimmer and Prem Puri

11

Pediatric Respiratory Physiology . . . . . . . . . . . . . . . . . . . . . . 181 Bettina Bohnhorst and Corinna Peter

12

Pediatric Cardiovascular Physiology . . . . . . . . . . . . . . . . . . . 201 Albert P. Rocchini and Aaron G. DeWitt

13

Pediatric Hepatic Physiology . . . . . . . . . . . . . . . . . . . . . . . . . 219 Mark Davenport and Nedim Hadzic ix

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Contents

14

Metabolism of Infants and Children . . . . . . . . . . . . . . . . . . . 231 Faraz A. Khan, Jeremy G. Fisher, Eric A. Sparks, and Tom Jaksic

15

Fluid and Electrolyte Balance in Infants and Children . . . . . 245 Joseph Chukwu and Eleanor J. Molloy

16

Vascular Access in Infants and Children . . . . . . . . . . . . . . . . 263 Hiroki Nakamura, Rieko Nakamura, and Thambipillai Sri Paran

17

Nutrition in Infants and Children . . . . . . . . . . . . . . . . . . . . . . 273 Agostino Pierro and Simon Eaton

18

Access for Enteral Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . 287 Julia Zimmer and Michael W. L. Gauderer

19

Tracheostomy in Infants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 Martin Lacher, Jan-Hendrik Gosemann, and Oliver J. Muensterer

20

Pediatric Airway Assessment . . . . . . . . . . . . . . . . . . . . . . . . . 329 Eimear Phelan and John Russell

21

Stomas of Small and Large Intestine . . . . . . . . . . . . . . . . . . . 339 Andrea Bischoff and Alberto Peña

22

Preoperative Assessments in Pediatric Surgery . . . . . . . . . . . 351 Linda Stephens and John Gillick

23

Principles of Pediatric Surgical Imaging . . . . . . . . . . . . . . . . 375 David Rea, Clare Brenner, and Terence Montague

24

Hematological Problems in Pediatric Surgery . . . . . . . . . . . . 387 Ciara O’Rafferty and Owen Patrick Smith

25

Surgical Safety in Children . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 George G. Youngson and Craig McIlhenny

26

Anesthesia and Pain Management . . . . . . . . . . . . . . . . . . . . . 427 Aidan Magee and Suzanne Crowe

27

Immunology and Immunodeficiencies in Children . . . . . . . . 443 Saima Aslam, Fiona O’Hare, Hassan Eliwan, and Eleanor J. Molloy

28

Sepsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461 Scott S. Short, Stephanie C. Papillon, and Henri R. Ford

29

Principles of Minimally Invasive Surgery in Children . . . . . 477 Steven Rothenberg and Samiksha Bansal

30

Innovations in Minimally Invasive Surgery in Children . . . . 487 Todd A. Ponsky and Gavin A. Falk

Contents

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31

Fast-Track Pediatric Surgery . . . . . . . . . . . . . . . . . . . . . . . . . 505 M. Reismann and Benno Ure

32

Ethical Considerations in Pediatric Surgery . . . . . . . . . . . . . 513 Jacqueline J. Glover and Benedict C. Nwomeh

33

Childhood Obesity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 Regien Biesma and Mark Hanson

34

Surgical Problems of Children with Physical Disabilities . . . 541 Casey M. Calkins and Keith T. Oldham

35

Clinical Research and Evidence-Based Pediatric Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 Dennis K. M. Ip, Kenneth K. Y. Wong, and Paul Kwong Hang Tam

36

Tissue Engineering and Stem Cell Research . . . . . . . . . . . . . 577 Paolo De Coppi

37

Patient- and Family-Oriented Pediatric Surgical Care . . . . . 593 Katelynn C. Bachman, Ronald C. Oliver, and Mary E. Fallat

38

Surgical Implications of Human Immunodeficiency Virus Infection in Children . . . . . . . . . . . . . . . . . . . . . . . . . . . 603 Alastair J. W. Millar, Jonathan Karpelowsky, and Sharon Cox

Part II

Newborn Surgery: Head and Neck . . . . . . . . . . . . . . . . . . .

615

39

Choanal Atresia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617 Eimear Phelan and John Russell

40

Macroglossia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625 Abdulrahman Alshafei and Thambipillai Sri Paran

41

Pierre Robin Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631 Udo Rolle, Aranka Ifert, and Robert Sader

42

Lymphatic Malformations in Children . . . . . . . . . . . . . . . . . 641 James Wall, Karl Sylvester, and Craig Albanese

43

Stridor in the Newborn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649 Sam J. Daniel

Volume 2 Part III Newborn Surgery: Esophagus . . . . . . . . . . . . . . . . . . . . . . .

659

44

Esophageal Atresia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661 Michael E. Höllwarth and Holger Till

45

Congenital Esophageal Stenosis . . . . . . . . . . . . . . . . . . . . . . . 681 Masaki Nio, Shintaro Amae, and Motoshi Wada

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Contents

46

Esophageal Duplication Cyst . . . . . . . . . . . . . . . . . . . . . . . . . 691 Dakshesh Parikh and Melissa Short

47

Esophageal Perforation in the Newborn David S. Foley

Part IV

. . . . . . . . . . . . . . . . 705

Newborn Surgery: Chest . . . . . . . . . . . . . . . . . . . . . . . . . . . .

713

48

Congenital Airway Malformations . . . . . . . . . . . . . . . . . . . . . 715 Richard G. Azizkhan

49

Vascular Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733 Benjamin O. Bierbach and John Mark Redmond

50

Pulmonary Air Leaks of the Neonate . . . . . . . . . . . . . . . . . . . 751 Prem Puri and Jens Dingemann

51

Chylothorax and Other Pleural Effusions in Neonates . . . . . 761 Richard G. Azizkhan

52

Congenital Malformations of the Lung . . . . . . . . . . . . . . . . . 775 Keith T. Oldham and Kathleen M. Dominguez

53

Congenital Diaphragmatic Hernia . . . . . . . . . . . . . . . . . . . . . 797 Julia Zimmer and Prem Puri

54

Extracorporeal Membrane Oxygenation for Neonatal Respiratory Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817 Jason S. Frischer, Charles J. H. Stolar, and Ronald B. Hirschl

Part V

Newborn Surgery: Gastrointestinal . . . . . . . . . . . . . . . . . .

827

55

Pyloric Atresia and Prepyloric Antral Diaphragm . . . . . . . . 829 Girolamo Mattioli and Sara Costanzo

56

Infantile Hypertrophic Pyloric Stenosis . . . . . . . . . . . . . . . . . 841 Takao Fujimoto

57

Gastric Volvulus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855 Alan E. Mortell and David Coyle

58

Gastric Perforation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865 Adam C. Alder and Robert K. Minkes

59

Duodenal Obstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875 Yechiel Sweed and Alon Yulevich

60

Malrotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897 Augusto Zani and Agostino Pierro

61

Congenital Hyperinsulinism . . . . . . . . . . . . . . . . . . . . . . . . . . 905 Augusto Zani and Agostino Pierro

Contents

xiii

62

Jejunoileal Atresia and Stenosis . . . . . . . . . . . . . . . . . . . . . . . 913 Alastair J. W. Millar, Alp Numanoglu, and Sharon Cox

63

Colonic and Rectal Atresias Tomas Wester

64

Duplications of the Alimentary Tract . . . . . . . . . . . . . . . . . . . 935 Mark D. Stringer

65

Mesenteric and Omental Cysts . . . . . . . . . . . . . . . . . . . . . . . . 955 Suzanne Victoria McMahon, Dermot Thomas McDowell, and Brian Sweeney

66

Necrotizing Enterocolitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963 Stephanie C. Papillon, Scott S. Short, and Henri R. Ford

67

Meconium Ileus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 973 Pietro Bagolan, Francesco Morini, and Andrea Conforti

68

Meconium Peritonitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 993 Jose L. Peiró and Emrah Aydin

69

Neonatal Ascites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003 Elke Zani-Ruttenstock and Augusto Zani

70

Hirschsprung’s Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1011 Prem Puri, Christian Tomuschat, and Hiroki Nakamura

71

Hirschsprung-Associated Enterocolitis . . . . . . . . . . . . . . . . . 1031 Farokh R. Demehri, Ihab F. Halaweish, Arnold G. Coran, and Daniel H. Teitelbaum

72

Variants of Hirschsprung Disease . . . . . . . . . . . . . . . . . . . . . . 1045 Prem Puri, Jan-Hendrik Gosemann, and Hiroki Nakamura

73

Anorectal Malformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1059 Andrea Bischoff, Belinda Hsi Dickie, Marc A. Levitt, and Alberto Peña

74

Congenital Pouch Colon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087 Amulya K. Saxena and Praveen Mathur

75

Congenital Segmental Dilatation of the Intestine . . . . . . . . . 1099 Yoshiaki Takahashi, Yoshinori Hamada, and Tomoaki Taguchi

76

Short Bowel Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1107 Michael E. Höllwarth

Part VI 77

. . . . . . . . . . . . . . . . . . . . . . . . . . 925

Newborn Surgery: Liver and Biliary Tract . . . . . . . . . . . . 1125

Biliary Atresia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1127 Mark Davenport and Amy Hughes-Thomas

xiv

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Contents

Congenital Biliary Dilatation . . . . . . . . . . . . . . . . . . . . . . . . . 1145 Atsuyuki Yamataka, Geoffrey J. Lane, and Joel Cazares

Part VII

Newborn Surgery: Anterior Abdominal Wall Defects . . . 1165

79

Omphalocele . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1167 Jacob C. Langer

80

Gastroschisis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1177 Marshall Z. Schwartz and Shaheen J. Timmapuri

81

Omphalomesenteric Duct Remnants . . . . . . . . . . . . . . . . . . . 1189 Kenneth K. Y. Wong and Paul Kwong Hang Tam

82

Conjoined Twins Juan A. Tovar

Part VIII

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1197

Newborn Surgery: Spina Bifida and Hydrocephalus . . . 1211

83

Spina Bifida and Encephalocele . . . . . . . . . . . . . . . . . . . . . . . 1213 Jonathan R. Ellenbogen, Michael D. Jenkinson, and Conor L. Mallucci

84

Hydrocephalus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1237 Jonathan R. Ellenbogen, J. Kandasamy, and Conor L. Mallucci

Part IX Newborn Surgery: Long-Term Outcomes in Newborn Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1257 85

Long-Term Outcomes in Newborn Surgery . . . . . . . . . . . . . . 1259 Risto J. Rintala, Mikko P. Pakarinen, and Antti Koivusalo

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

About the Editor

Prem Puri is the Newman Clinical Research Professor at the University College Dublin School of Medicine and Medical Science and Consultant Paediatric Surgeon and Director of Surgical Research at the Beacon Hospital. He is currently the President of the World Federation of Associations of Pediatric Surgeons (WOFAPS) Foundation and Secretary of the International Board of Pediatric Surgical Research. He is Past President of the World Federation of Associations of Pediatric Surgeons (WOFAPS) and of the European Paediatric Surgeons’ Association (EUPSA). He is Editor-in-Chief of Paediatric Surgery International and also on the Editorial Board of several other journals. He was the Director of Research (1989–2009) and President (2009–2016) of the National Children’s Research Centre, Our Lady’s Children’s Hospital, Dublin. He has been awarded many Honorary Fellowships, including the American Surgical Association (ASA), American Academy of Pediatrics, American Pediatric Surgical Association, Canadian Association of Paediatric Surgeons, Japanese Society of Pediatric Surgeons, and also Argentinean, Austrian, Canadian, Czech, Croatian, Cuban, Indian, South African, and Ukrainian pediatric surgical associations.

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About the Editor

Professor Puri is known internationally for his research into underlying mechanisms causing birth defects, and innovative treatments, which have benefited children all over the world. He is a multi-award-winning researcher whose previous awards include People of the Year Award (Highest Irish National Award), the prestigious Denis Browne Gold Medal by the British Association of Paediatric Surgeons, and Rehbein Medal by the European Paediatric Surgeons’ Association for outstanding contribution to pediatric surgery. He has been a Visiting Professor to many leading universities all over the world and invited speaker at over 250 international scientific meetings. He has published 10 books, 147 chapters in textbooks, and over 700 articles in peer-reviewed journals. He is the Editor of Newborn Surgery, regarded as the authoritative book in the field, and the fourth edition is now published, and also of the widely acclaimed Pediatric Surgery (Atlas Series), which is in its second edition. His research has been cited over 20,000 times in peer-reviewed articles.

Contributors

Craig Albanese New York Presbyterian Hospital, New York, NY, USA Adam C. Alder Division of Pediatric Surgery, Children’s Medical Center Plano, Center for Pectus and Chest Wall Anomalies, Division of Pediatric Surgery, Children’s Health, Department of Surgery, UTSW, Dallas, TX, USA Abdulrahman Alshafei Paediatric Surgery, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Shintaro Amae Department of Surgery, Miyagi Children’s Hospital, Sendai, Japan Saima Aslam Discipline of Paediatrics, Trinity College, The University of Dublin, Dublin, Ireland Tallaght Hospital and Coombe Women’s and Infants University Hospital, Dublin, Ireland Emrah Aydin The Center for Fetal, Cellular and Molecular Therapy, Pediatric General and Thoracic Surgery Division, Cincinnati Children’s Hospital Medical Center (CCHMC), Cincinnati, OH, USA Richard G. Azizkhan Children’s Hospital and Medical Center, University of Nebraska College of Medicine, Omaha, NE, USA Katelynn C. Bachman University of Louisville School of Medicine, Louisville, KY, USA Pietro Bagolan Neonatal Surgery Unit, Department of Medical and Surgical Neonatology, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy Samiksha Bansal Department of Pediatric Surgery, Rocky Mountain Hospital for Children at Presbyterian/St. Luke’s, Denver, CO, USA Benjamin O. Bierbach Department of Paediatric Cardiac Surgery, German Paediatric Heart Center Sankt Augustin, Sankt Augustin, Germany Regien Biesma Department of Epidemiology and Public Health Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland Andrea Bischoff Division of Pediatric Surgery, International Center for Colorectal and Urogenital Care, Children’s Hospital Colorado, Aurora, CO, USA xvii

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Carlos E. Blanco Department of Neonatology, National Maternity Hospital, Dublin, Ireland Bettina Bohnhorst Department of Pediatric Pulmonology, Allergology and Neonatology, Hannover Medical School, Hannover, Germany Clare Brenner Department of Radiology, Our Lady’s Children’s Hospital, Dublin, Ireland Casey M. Calkins Division of Pediatric Surgery, Medical College of Wisconsin, The Children’s Hospital of Wisconsin, Milwaukee, WI, USA Joel Cazares Department of Pediatric General and Urogenital Surgery, Juntendo University School of Medicine, Tokyo, Japan Department of Pediatric Surgery, Hospital Regional de Alta Especialidad Materno Infantil, Monterrey, Mexico Joseph Chukwu Clinical Research Unit, National Children’s Research Centre, Our Lady’s Children’s Hospital, Dublin, Ireland Andrea Conforti Neonatal Surgery Unit, Department of Medical and Surgical Neonatology, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy Arnold G. Coran Section of Pediatric Surgery, C.S. Mott Children’s Hospital and the University of Michigan School of Medicine, Ann Arbor, MI, USA Sara Costanzo Department of Paediatric Surgery, University of Genoa, Genoa, Italy Paediatric Surgery Unit, “V. Buzzi” Children’s Hospital, Milan, Italy Sharon Cox Division of Paediatric Surgery, Faculty of Health Sciences, University of Cape Town, Red Cross War Memorial Children’s Hospital, Cape Town, South Africa David Coyle Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Suzanne Crowe Our Lady’s Children’s Hospital Crumlin, Dublin, Ireland Sam J. Daniel Department of Pediatric Surgery, Montreal Children’s Hospital, McGill University, Montreal, QC, Canada Mark Davenport Department of Paediatric Surgery, Kings College Hospital NHS Foundation Trust, London, UK Paolo De Coppi Great Ormond Street Hospital and UCL Institute of Child Health, London, UK Farokh R. Demehri Section of Pediatric Surgery, C.S. Mott Children’s Hospital and the University of Michigan School of Medicine, Ann Arbor, MI, USA Aaron G. DeWitt Department of Pediatric and Communicable Diseases, C.S. Mott Children’s Hospital, Congenital Heart Center, University of Michigan, Ann Arbor, MI, USA

Contributors

Contributors

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Belinda Hsi Dickie Colorectal and Complex Pelvic Malformation Center, Department of Surgery, Boston Children’s Hospital, Boston, MA, USA Jens Dingemann Centre of Pediatric Surgery Hannover, Hannover Medical School and Bult Children’s Hospital, Hannover, Germany Kathleen M. Dominguez Pediatric Surgery, Marshfield Clinic, Marshfield, WI, USA Simon Eaton Department of Paediatric Surgery, UCL Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust, London, UK Hassan Eliwan Discipline of Paediatrics, Trinity College, The University of Dublin, Dublin, Ireland Tallaght Hospital and Coombe Women’s and Infants University Hospital, Dublin, Ireland Jonathan R. Ellenbogen Department of Neurosurgery, Alder Hey Children’s NHS Foundation Trust, Liverpool, UK Department of Neurosurgery, The Walton Centre NHS Foundation Trust, Liverpool, UK Gavin A. Falk Division of Pediatric Surgery, Miami Children’s Hospital, Miami, FL, USA Mary E. Fallat University of Louisville School of Medicine, Louisville, KY, USA Hiram C. Polk, Jr. Department of Surgery, Division of Pediatric Surgery, University of Louisville School of Medicine, Louisville, KY, USA Norton Healthcare, Norton Children’s Hospital, Louisville, KY, USA Jeremy G. Fisher Center for Advanced Intestinal Rehabilitation, Department of Surgery, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Alan W. Flake Center for Fetal Diagnosis and Therapy, Children’s Hospital of Philadelphia, Philadelphia, PA, USA David S. Foley Department of Surgery, University of Louisville School of Medicine, Louisville, KY, USA Henri R. Ford Division of Pediatric Surgery, Children’s Hospital Los Angeles, Los Angeles, CA, USA Jason S. Frischer Colorectal Center, ECMO Program, Division of Pediatric General and Thoracic Surgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA Takao Fujimoto Department of Paediatric Surgery, Imperial Gift Foundation, Aiiku Maternal and Children’s Medical Center, Tokyo, Japan Michael W. L. Gauderer University of South Carolina School of Medicine Greenville, Greenville, SC, USA

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John Gillick Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Children’s University Hospital, Dublin, Ireland Jacqueline J. Glover Department of Pediatrics and Center for Bioethics and Humanities, University of Colorado Anschutz Medical Campus and The Children’s Hospital Colorado, Aurora, CO, USA Jan-Hendrik Gosemann Department of Pediatric Surgery, University of Leipzig, Leipzig, Germany Andrew J. Green Department of Clinical Genetics, Our Lady’s Hospital, Crumlin, Dublin, Ireland School of Medicine and Medical Science, University College Dublin, Belfield, Dublin, Ireland Nedim Hadzic Paediatric Liver Centre, Kings College Hospital, London, UK Ihab F. Halaweish Section of Pediatric Surgery, C.S. Mott Children’s Hospital and the University of Michigan School of Medicine, Ann Arbor, MI, USA Yoshinori Hamada Department of Surgery, Kansai Medical University, Osaka, Japan Mark Hanson Institute of Developmental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK Ronald B. Hirschl Section of Pediatric Surgery, C.S. Mott Children’s Hospital, University of Michigan, Ann Arbor, MI, USA Michael E. Höllwarth Department of Paediatric and Adolescent Surgery, Medical University of Graz, Graz, Austria Amy Hughes-Thomas Department of Paediatric Surgery, Kings College Hospital, London, UK Aranka Ifert Carolinum, Institute of Dentistry, Frankfurt, Germany Dennis K. M. Ip School of Public Health, The University of Hong Kong, Hong Kong, China Tom Jaksic Center for Advanced Intestinal Rehabilitation, Department of Surgery, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Michael D. Jenkinson Department of Neurosurgery, The Walton Centre NHS Foundation Trust, Liverpool, UK Edwin C. Jesudason NHS Lothian, Edinburgh, UK J. Kandasamy Department of Neurosurgery, Western General Hospital, Edinburgh, UK Jonathan Karpelowsky Paediatric Oncology and Thoracic Surgery, Children’s Hospital at Westmead Children’s cancer research Unit, University of Sydney, Sydney, Australia

Contributors

Contributors

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Faraz A. Khan Center for Advanced Intestinal Rehabilitation, Department of Surgery, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Emily A. Kieran Department of Neonatology, The National Maternity Hospital, Dublin, Ireland National Children’s Research Centre, Dublin, Ireland School of Medicine and Medical Science, University College Dublin, Dublin, Ireland Aimee G. Kim Center for Fetal Diagnosis and Therapy, Children’s Hospital of Philadelphia, Philadelphia, PA, USA Dietrich Kluth Department of Pediatric Surgery, University Hospital, University of Leipzig, Leipzig, Germany Antti Koivusalo Department of Pediatric Surgery, Children’s Hospital, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland Martin Lacher Department of Pediatric Surgery, University of Leipzig, Leipzig, Germany Kokila Lakhoo Paediatric Surgery, Children’s Hospital Oxford, Oxford University Hospitals, University of Oxford, Oxford, UK Geoffrey J. Lane Department of Pediatric General and Urogenital Surgery, Juntendo University School of Medicine, Tokyo, Japan Jacob C. Langer Division of General and Thoracic Surgery, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada Marc A. Levitt Center for Colorectal and Pelvic Reconstruction, Nationwide Children’s Hospital, Columbus, OH, USA Tippi C. MacKenzie Eli and Edythe Broad Center for Regeneration Medicine, Fetal Treatment Center, University of California, San Francisco, CA, USA Aidan Magee Our Lady’s Children’s Hospital Crumlin, Dublin, Ireland Conor L. Mallucci Department of Neurosurgery, Alder Hey Children’s NHS Foundation Trust, Liverpool, UK Praveen Mathur Department of Pediatric Surgery, SMS Medical College, Jaipur, Rajasthan, India Girolamo Mattioli Department of Paediatric Surgery, Giannina Gaslini Research Institute and University of Genoa, Genoa, Italy Dermot Thomas McDowell Department of Paediatric Surgery, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Craig McIlhenny Forth Valley Royal Hospital, Larbert, Scotland, UK Suzanne Victoria McMahon Department of Paediatric Surgery, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland

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Roman Metzger Department of Paediatric and Adolescent Surgery, Paracelsus Medical University Salzburg, Salzburg, Austria Alastair J. W. Millar Emeritus Professor of Paediatric Surgery, Faculty of Health Sciences, Department of Paediatric Surgery, University of Cape Town, Red Cross War Memorial Children’s Hospital, Cape Town, Rondebosch, South Africa Robert K. Minkes Division of Pediatric Surgery, Golisano Children’s Hospital Lee Health, Fort Myers, FL, USA Eleanor J. Molloy Department of Neonatology, Paediatrics, National Maternity Hospital, Dublin, Ireland UCD School of Medicine and Medical Sciences, University College Dublin, Dublin, Ireland Neonatology, Our Lady’s Children’s Hospital, Dublin, Ireland Paediatrics, Royal College of Surgeons in Ireland, Dublin, Ireland Discipline of Paediatrics, Trinity College, The University of Dublin, Dublin, Ireland Tallaght Hospital and Coombe Women’s and Infants University Hospital, Dublin, Ireland Terence Montague Department of Anesthesia, Our Lady’s Children’s Hospital, Dublin, Ireland Francesco Morini Neonatal Surgery Unit, Department of Medical and Surgical Neonatology, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy Alan E. Mortell Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Children’s University Hospital, Dublin, Ireland Oliver J. Muensterer Department of Pediatric Surgery, University Medicine Mainz, Johannes Gutenberg University, Mainz, Germany Hiroki Nakamura National Children’s Research Centre, Our Lady’s Children’s Hospital, Dublin, Ireland Department Pediatric General and Urogenital Surgery, Juntendo University School of Medicine, Tokyo, Japan Rieko Nakamura Department of Anesthesiology, Nihon University School of Medicine, Tokyo, Japan Masaki Nio Department of Pediatric Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan Alp Numanoglu Division of Paediatric Surgery, Faculty of Health Sciences, University of Cape Town, Red Cross War Memorial Children’s Hospital, Cape Town, South Africa Benedict C. Nwomeh Department of Surgery, Ohio State University College of Medicine, Columbus, OH, USA Nationwide Children’s Hospital, Columbus, OH, USA

Contributors

Contributors

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James J. O’Byrne Department of Clinical Genetics, Our Lady’s Hospital, Crumlin, Dublin, Ireland Colm P. F. O’Donnell National Maternity Hospital, Dublin, Ireland School of Medicine, University College Dublin, Dublin, Ireland National Children’s Research Centre, Crumlin, Dublin, Ireland Fiona O’Hare Discipline of Paediatrics, Trinity College, The University of Dublin, Dublin, Ireland Tallaght Hospital and Coombe Women’s and Infants University Hospital, Dublin, Ireland Ciara O’Rafferty Department of Haematology, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Keith T. Oldham Division of Pediatric Surgery, Medical College of Wisconsin, Children’s Hospital of Wisconsin, Children’s Corporate Center, Milwaukee, WI, USA Aliza M. Olive Center for Fetal Diagnosis and Therapy, Children’s Hospital of Philadelphia, Philadelphia, PA, USA Ronald C. Oliver Norton Healthcare, Norton Children’s Hospital, Louisville, KY, USA Mikko P. Pakarinen Department of Pediatric Surgery, Children’s Hospital, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland Stephanie C. Papillon Division of Pediatric Surgery, Children’s Hospital Los Angeles, Los Angeles, CA, USA Thambipillai Sri Paran Paediatric Surgery, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Trinity College, Dublin, Ireland Dakshesh Parikh Birmingham Children’s Hospital NHS FT, Birmingham, UK Alberto Peña Division of Pediatric Surgery, International Center for Colorectal and Urogenital Care, Children’s Hospital Colorado, Aurora, CO, USA Colorectal Center for Children, Division of Pediatric Surgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA Jose L. Peiró University of Cincinnati, Cincinnati, OH, USA Pediatric General and Thoracic Surgery Division, Cincinnati Fetal Center, Cincinnati Children’s Hospital Medical Center (CCHMC), Cincinnati, OH, USA Corinna Peter Department of Pediatric Pulmonology, Allergology and Neonatology, Hannover Medical School, Hannover, Germany Eimear Phelan Our Lady’s Children’s Hospital Crumlin, Dublin, Ireland

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Contributors

Agostino Pierro Division of General and Thoracic Surgery, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada Department of Surgery, University of Toronto, Toronto, Canada Todd A. Ponsky Division of Pediatric Surgery, Akron Children’s Hospital, Akron, OH, USA Prem Puri Department of Pediatric Surgery, Beacon Hospital, Dublin, Ireland School of Medicine and Medical Science and Conway Institute of Biomedical Research, University College Dublin, Dublin, Ireland David Rea Department of Radiology, Our Lady’s Children’s Hospital, Dublin, Ireland John Mark Redmond Our Lady’s Children’s’ Hospital, Dublin, Ireland Mater Misericordiae University Hospital, Dublin, Ireland M. Reismann Department of Pediatric Surgery and Urology, Astrid Lindgren Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden Risto J. Rintala Department of Pediatric Surgery, Children’s Hospital, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland Albert P. Rocchini Department of Pediatric and Communicable Diseases, C.S. Mott Children’s Hospital, Congenital Heart Center, University of Michigan, Ann Arbor, MI, USA Udo Rolle Department of Pediatric Surgery and Pediatric Urology, Goethe University Frankfurt, Frankfurt, Germany Steven Rothenberg Department of Pediatric Surgery, Rocky Mountain Hospital for Children at Presbyterian/St. Luke’s, Denver, CO, USA John Russell Our Lady’s Children’s Hospital Crumlin, Dublin, Ireland Robert Sader Department of Oral, Maxillofacial, and Plastic Facial Surgery, Goethe University Frankfurt, Frankfurt, Germany Amulya K. Saxena Department of Pediatric Surgery, Chelsea and Westminster Hospital NHS Foundation Trust, Imperial College London, London, UK Marshall Z. Schwartz Drexel University College of St. Christopher’s Hospital for Children, Philadelphia, PA, USA

Medicine,

N. Scott Adzick The Division of Pediatric General and Thoracic Surgery, The Center for Fetal Diagnosis and Treatment, Children’s Hospital of Philadelphia, Philadelphia, PA, USA Melissa Short Department of Paediatric Surgery, Birmingham Children’s Hospital, Newcastle upon Tyne, UK Scott S. Short Division of Pediatric Surgery, Children’s Hospital Los Angeles, Los Angeles, CA, USA

Contributors

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Owen Patrick Smith Department of Haematology, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland University College Dublin, Dublin, Ireland Eric A. Sparks Center for Advanced Intestinal Rehabilitation, Department of Surgery, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA Linda Stephens Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Charles J. H. Stolar Emeritus Professor of Surgery and Pediatrics, Columbia University, College of Physicians and Surgeons, New York, NY, USA California Pediatric Surgery Group, Goleta, CA, USA Morgan Stanley Children’s Hospital, Division of Pediatric Surgery, New York, NY, USA Mark D. Stringer Department of Paediatric Surgery, Wellington Hospital, Wellington, New Zealand Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand Yechiel Sweed Department of Pediatric Surgery, Galilee Medical Center, Azrieli Faculty of Medicine, Bar-Ilan University, Safed, Israel Brian Sweeney Department of Paediatric Surgery, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Karl Sylvester Lucile Packard Children’s Hospital at Stanford University, Stanford, CA, USA Tomoaki Taguchi Department of Pediatric Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan Yoshiaki Takahashi Department of Pediatric Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan Paul Kwong Hang Tam Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China Daniel H. Teitelbaum Section of Pediatric Surgery, C.S. Mott Children’s Hospital and the University of Michigan School of Medicine, Ann Arbor, MI, USA Holger Till Department of Paediatric and Adolescent Surgery, Medical University of Graz, Graz, Austria Shaheen J. Timmapuri Rutgers/Robert Wood Johnson Medical School, Bristol–Myers Squibb Children’s Hospital, New Brunswick, NJ, USA Christian Tomuschat National Children’s Research Centre, Our Lady’s Children’s Hospital, Dublin, Ireland Juan A. Tovar Department of Pediatric Surgery, Hospital Universitario La Paz, Universidad Autonoma de Madrid, Madrid, Spain

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Benno Ure Center of Pediatric Surgery Hannover, Hannover Medical School and Children’s Hospital Bult, Hannover, Germany Eduardo Villamor Department of Pediatrics, School for Oncology and Developmental Biology (GROW), Maastricht University Medical Center (MUMC+), Maastricht, The Netherlands Motoshi Wada Department of Pediatric Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan James Wall Pediatric General Surgery, Stanford University, Stanford, CA, USA Tomas Wester Department of Pediatric Surgery, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden Kenneth K. Y. Wong Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China Atsuyuki Yamataka Department of Pediatric General and Urogenital Surgery, Juntendo University School of Medicine, Tokyo, Japan George G. Youngson Department of Paediatric Surgery, University of Aberdeen, Royal Aberdeen Children’s Hospital, Aberdeen, Scotland, UK Alon Yulevich Department of Pediatric Surgery, Galilee Medical Center, Bar-Ilan University, Safed, Israel Augusto Zani Division of General and Thoracic Surgery, The Hospital for Sick Children, Toronto, Canada Department of Surgery, University of Toronto, Toronto, Canada Elke Zani-Ruttenstock Division of General and Thoracic Surgery, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada Julia Zimmer National Children’s Research Centre, Our Lady’s Children’s Hospital, Crumlin, Dublin, Ireland Department of Pediatric Surgery, Hannover Medical School, Hannover, Germany

Contributors

Part I General

1

Embryology of Congenital Malformations Dietrich Kluth and Roman Metzger

Contents Misconceptions and/or Outdated Theories Concerning Normal and Abnormal Embryology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Shortage of Study Material (Both Normal and Abnormal Embryos) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Shortage of Explanatory Images of Embryos and Developing Embryonic Organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Difficulties in the Interpretation of Serial Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Animal Models Used for Applied Embryology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Embryos of Different Species for the Study of Normal Embryology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Surgical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Chemical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Genetic Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Spontaneous Malformations Without Genetic Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Scanning Electron Microscopic Atlas of Normal and Abnormal Development in Embryos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Foregut Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Development of the Diaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Development of the Hindgut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Development of the External Genitalia and the Urethra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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D. Kluth (*) Department of Pediatric Surgery, University Hospital, University of Leipzig, Leipzig, Germany e-mail: [email protected]; [email protected] R. Metzger Department of Paediatric and Adolescent Surgery, Paracelsus Medical University Salzburg, Salzburg, Austria e-mail: [email protected]; [email protected] © Springer-Verlag GmbH Germany, part of Springer Nature 2020 P. Puri (ed.), Pediatric Surgery, https://doi.org/10.1007/978-3-662-43588-5_1

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D. Kluth and R. Metzger The Development of the Midgut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Testicular Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Abstract

Today, the embryology of numerous congenital anomalies in humans is still a matter of speculation. This is due to a number of reasons which include: • Misconceptions and/or outdated theories concerning normal and abnormal embryology • A shortage of study material (both normal and abnormal embryos) • A shortage of explanatory images of embryos and developing embryonic organs • Difficulties in the interpretation of serial sections In recent years, a number of animal models had been established which helped to overcome the shortage of both normal and abnormal embryos. However, a general agreement on when, why, and how abnormal development takes place still does not exist. As a result, many typical malformations are still not explained satisfactorily and pediatric surgeons of all specialties are still confused when they are confronted with the background of normal and abnormal embryologic development. Keywords

Human birth defects · Animal models · Teratology · Human embryology

Misconceptions and/or Outdated Theories Concerning Normal and Abnormal Embryology Our understanding of the normal and abnormal development of embryos is still influenced by two theories: (a) The “biogenetic law” after Haeckel (1975) (b) The theory of “Hemmungsmißbildungen” (Schwalbe 1906)

According to Haeckel’s “biogenetic law,” a human embryo recapitulates in its individual development (ontogeny) the morphology observed in all lifeforms (phylogeny). This means that during its development, an advanced species (a human embryo) seems to pass through stages represented by adult organisms of more primitive species (Gilbert 2003). This theory has been used to “bridge” gaps in the understanding of normal embryonic development and still has an impact on the nomenclature of embryonic organs. This explains why human embryos have “cloacas” like adult birds and “branchial” clefts like adult fish. The term “Hemmungsmißbildung” stands for the theory that malformations actually represent “frozen” stages of normal embryonic development. This theory too has been used to “bridge” gaps in the understanding of normal embryonic development in a manner which could best describe as “reversed embryology.” As a result, our knowledge of normal embryology stems more from pathological-anatomic interpretations of observed malformations than from proper embryological studies. The theory of the “rotation of the gut” as a step in normal development is a perfect example for this misconception (Fig. 1a). Others are “failed fusion of the urethral folds” (hypospadia, Fig. 1b), “failed closure of the pleuroperitoneal canals” (congenital diaphragmatic hernia, Fig. 1c), or “persistent cloaca” (Fig. 1d).

A Shortage of Study Material (Both Normal and Abnormal Embryos) Today, a growing number of animal models exist which allow embryological studies in various embryological fields. This includes studies in normal as well as in abnormal embryos. Especially for the studies of esophageal and anorectal malformations, a number of animal models had been established.

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Fig. 1 Theory of “Hemmungsmißbildungen”: typical examples. (a) Schematic drawing of the “rotation of the gut” (After McVay et al. 2007, with permission from Elsevier). Impaired rotation causes “malrotation.” (b) Schematic drawing of urethral development (Modified after Hamilton et al. 1962). Hypospadia as a result of impaired fusion of urethral folds (UG). AP anal pit, GP glans penis, UO urethral opening, US urethral sulcus, SS scrotal swelling. (c) Schematic drawing of diaphragmatic

development (Modified after Bromann 1902): impaired closure of diaphragmatic membranes causes diaphragmatic hernia. AO aorta, E esophagus, L diaphragm derived from lateral body wall, PN phrenic nerve, P pericardium, PPM pleuroperitoneal membrane, VC vena cava, PPC pleuroperitoneal canal, M diaphragm derived from dorsal mesenterium. (d) Schematic drawing of cloacal development (Stephens 1963). Impaired formation of the urorectal septum causes anorectal malformations

A Shortage of Explanatory Images of Embryos and Developing Embryonic Organs

(a) Serial sectioning of embryos and timeconsuming three-dimensional reconstructions are not necessary. (b) The embryo can be studied in all three dimensions “online.” (c) The images and photographs are of superior quality (Fig. 2).

Advanced technology in a number of fields gives much better insights into human development. This includes ultrasonography of fetuses as well as magnetic resonance imaging (MRI). For detailed embryological studies, scanning electron microscopy is still a very useful tool. Recently, STEDING published a scanning electron microscopic atlas of human embryos which provides detailed insights into normal human embryology (Steding 2009). Scanning electron microscopy is the perfect tool to document embryonic structures:

Difficulties in the Interpretation of Serial Sections Although a number of specific tasks demand the serial section of embryos, the difficulties in the interpretation must not be underestimated. Three-

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Fig. 2 Scanning electron microscopy (SEM) electron microscopy enables a wide range of magnification and a superior quality of photographs: perineal region of a

female rat, ED 20. The highest magnification shows detailed structures on the cell surface (SEM Pictures © D. Kluth)

dimensional (3D) reconstructions, although feasible, are tainted with a loss of information, not only caused by the sectioning itself but also by the use of 3D image software.

animal models, the detailed study of normal embryos of the same species is mandatory. We used scanning electron microscopy (SEM) in chicken, rat, and murine embryos in order to study certain embryological processes of the normal embryology of the foregut, the hindgut, the midgut, the testicular descent, and the development of the external genitalia. The advantage of chicken embryos is the high availability at low costs. They are easily accessible in the eggshell, and further breeding is possible when the eggs are treated accordingly. Embryos of rats and mice can be obtained in comparable large numbers; however, local regulations may limit the usage of mammalian embryos. (a) The chicken embryo was used to study foregut development. The aim was to clarify whether lateral ridges occur in the developing foregut or not and, when present, if they fuse to form the tracheoesophageal septum (Kluth et al. 1987; Metzger et al. 2011a) (Fig. 3). (b) Rat embryos were used to study, i.e., developmental processes during testicular descent, to clarify if “rotation” takes place during gut development (Fig. 4a), to assess the question if “cloacas” actually exist in rat embryos, and how the differentiation of the developing hindgut takes place (Fiegel et al. 2011; Metzger et al. 2011a; Kluth et al. 2011a) (Fig. 4b).

Animal Models Used for Applied Embryology Over the last two decades. a number of animal models have been developed with the potential to gain a better understanding of the morphology of not only malformed but also normal embryos. These animal models can be grouped in five subgroups: 1. Embryos of different species for the study of normal embryology 2. Surgical models 3. Chemical models 4. Genetic models 5. “Spontaneous” malformations of unclear cause

Embryos of Different Species for the Study of Normal Embryology Human embryos are rare. Human embryos displaying typical anomalies are extremely rare. Therefore it makes sense to study specific developmental processes in embryos of animals with humanlike abnormalities. However, in all cases of

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Embryology of Congenital Malformations

Fig. 3 Animal models: chicken model is used to study the normal development of the foregut. (a) Schematic drawing of the developing foregut (Modified after Gray and Skandalakis 1972c). Dotted arrows indicate the growth directions of the esophagus (gray) and trachea (white). The small arrow in between indicates the growth direction of the assumed septum. The thick arrows point to the

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lateral ridges (insert) which are thought to appear in the foregut and which form the epithelial tracheoesophageal septum. (b) Schematic picture of the “water tap theory.” The lung anlage forms as a diverticulum which grows caudal and thus forms the trachea (Drawing modified after Merei and Hutson 2002)

Fig. 4 Animal models: rat embryos were used to study midgut development (a) and hindgut development (b) (SEM Pictures © D. Kluth)

(c) Mouse embryos were studied in the SD-mouse model (Fig. 5). Here, normal and abnormal hindgut development was studied (Kluth et al. 1995a).

Surgical Models In the past, the chicken was an important surgical model to study embryological processes. As mentioned above, the easy access to the embryo, its broad availability, and its cheapness make it an ideal model for experimental studies. It has been

widely used by embryologist especially in the field of epithelial/mesenchymal interactions (Goldin and Opperman 1980; Steding 1967; Jacob 1971). Pediatric surgeons have used this model to study morphological processes involved in intestinal atresia formation (Molenaar and Tibboel 1982; Schoenberg and Kluth 2002), gastroschisis (Aktug et al. 1997), and Hirschsprung’s disease (Meijers et al. 1992). The Czech embryologist Lemez (1980) used chicken embryos in order to induce tracheal agenesis with tracheoesophageal fistula (Fig. 6).

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Fig. 5 Animal models: SD-mice were used to study anorectal malformations. (a) Notice the short tail in a heterocygotic SD mouse. (b) Histology of the pelvic organs in a newborn heterozygous SD-mouse. The features

of an anorectal malformation with rectourethral fistula (F) and a blind ending rectal pouch (RP) are detectable. U urethra. (c) The spectrum of malformations seen in SD-mice

Apart from these purely embryonic models, a large number of fetal models had been developed in the last 30 years. Although they were mainly created to study the feasibility of fetal interventions (Harrison et al. 1980), they also contributed to our current knowledge of normal and abnormal fetal development and fetal organ systems.

(e) Nitrofen (Ambrose et al. 1971; Tenbrinck et al. 1990; Kluth et al. 1990; Costlow and Manson 1981; Irtani 1984) (f) Suramin and trypan (Männer and Kluth 2003, 2005)

Chemical Models It is well known that a number of chemicals (drugs, chemical fertilizers) can alter normal development of humans and animals alike. Some of these had been used to induce malformations similar to those found in humans. Most important today are: (a) The adriamycin model (Thompson et al. 1978; Diez-Pardo et al. 1996; Beasley et al. 2000) (b) Etretinate (Kubota et al. 1998; Liu et al. 2003) (c) All-trans-retinoic acid (ATRA) (Bitoh et al. 2002; Hashimoto et al. 2002; Sasaki et al. 2004) (d) Ethylenethiourea (Arana et al. 2001; Qi et al. 2002)

Models (a–d) have been used to study atresia formation in the esophagus, the midgut, and the anorectum. Model (e) was developed to study malformations of the diaphragm, the lungs, the heart, and kidneys (hydronephrosis). Model (f) was used in chicken embryos to study the formation of cloacal exstrophy. We used the nitrofen model to study the morphology of diaphragmatic hernia formation in rat embryos (Fig. 7).

Genetic Models Many aspects make genetic models the ideal model for the studies of abnormal development. In the past, a number of genetic models have been used for embryological studies of

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Fig. 6 Animal models: experimental embryology in chicken embryos. Metal clips were used to induce tracheal atresia (Lemez 1980). (a) Schematic drawing of the

technique, (b) arrows indicate the area where the clips were positioned (SEM picture of a chicken embryo). (SEM Picture and schematic drawing © Dietrich Kluth)

Fig. 7 Animal models: the nitrofen model of diaphragmatic hernia. (a) Newborn rat with diaphragmatic hernia after nitrofen exposure at day 11.5. (b) Results of nitrofen

exposure on days 9.5, 10.5, 11.5, 12.5, and 13.5. Most hernias were seen after nitrofen exposure on day 11.5

malformations. While older models were mostly the product of spontaneous mutations, newer models are, in most instances, the result of genetic manipulations mainly in mice (transgenic mice). The following models have been used by pediatric surgeons:

(a) Models of spontaneous origin: The SD-mouse model (Dunn et al. 1940; Kluth et al. 1991). In the SD-mouse model, anorectal malformations are combined with anomalies of the kidneys, the spine, and the external genitalia (Fig. 5).

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(b) Inheritance models: the pig model of anal atresia (van der Putte and Neeteson 1984; Lambrecht and Lierse 1987) (Fig. 9). In pigs, anorectal malformations are seen quite frequently. One out of 300 newborn piglets present with anorectal malformations without evidence of genetical alterations. (c) “Knockout” models. (d) Viral models. The number of transgenic animal models is currently growing fast. For pediatric surgeons those models are of major importance, which result in abnormalities of the fore- and hindgut. Here, interference with the Sonic hedgehog (Shh) pathway has proven to be very effective (Litingtung et al. 1998; Kim et al. 2001; Mo et al. 2001). There are two ways to interfere with that pathway: I. Targeted deletion of Sonic hedgehog (Litingtung et al. 1998; Kim et al. 2001) II. Deletion of one of the three transcription factors Glil, Gli2, and Gli3 (Kim et al. 2001; Mo et al. 2001) It has been demonstrated, that targeted deletion of Sonic hedgehog resulted in homozygous Shh null mutant mice in the formation of foregut malformations like esophageal atresia/stenosis, tracheoesophageal fistulas, and tracheal/lung anomalies (Litingtung et al. 1998). In the hindgut, the deletion of Sonic hedgehog caused the formation of “cloacas” (Kim et al. 2001), while Gli2 mutant mice presented with the “classic” form of anorectal malformations and Gli3 mutants showed minor forms like anal stenosis (Kim et al. 2001; Mo et al. 2001). Interestingly, the morphology of Gli2 mutant mice embryos resembles that of heterozygous SD-mice embryos, while Shh null mutant mice embryos had morphological similarities with homozygous SD-mice embryos. It is interesting to note that after administration of adriamycin, abnormal pattern of Shh distribution could be demonstrated in the developing foregut (Arsic et al. 2004).

D. Kluth and R. Metzger

Recently, Botham et al. studied developmental disorders of the duodenum in mutations of the fibroblast growth factor receptor 2 gene (Fgfr2IIIb) (Botham et al. 2012). They noted an increased apoptotic activity in the duodenal epithelium of Fgfr2IIIb -/- embryos at day 10.5, followed by a disappearance of the endoderm at day 11.5. Interestingly, the duodenal mesoderm also disappeared within 2 days, and an atresia was formed. Similar processes had been observed in newborn piglets whose esophageal epithelium was removed via endoscopy (Booß and Okmian 1974; Komfält and Okmian 1973). This procedure resulted in esophageal atresias in these piglets. In humans, viral infections are known to cause malformations. Animal models that use viral infections important for pediatric surgeons are very rare. One exception is the murine model of extrahepatic biliary atresia (EHBA) (Petersen et al. 1997). In this model, newborn Balb/c mice are infected with rhesus rotavirus group A45. As a result, the full spectrum of EHBA develops as it is seen in newborn with this disease. However, this model is not a model to mimic failed embryology. But it highlights the possibility that malformations are not caused by embryonic disorders but caused by fetal or even postnatal catastrophes.

Spontaneous Malformations Without Genetic Background In chicken embryos, a number of spontaneous malformations can be observed. It is not quite clear which processes cause them. One reason may be a prolonged storage (more than 3 days) in fridges below 8  C before breeding is started (Sydow H, Göttingen, Germany, “personal communication”). Spontaneous malformations of the head anlage (i.e., double anlage of the head, Fig. 8), the anlage of the heart, as well as abnormalities of the embryonic position (heterotaxia) are frequently seen (Sydow H, Göttingen, Germany, “personal communication”) (Fig. 9). This part on embryology and animal models highlights not only the importance to study

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Scanning Electron Microscopic Atlas of Normal and Abnormal Development in Embryos

Fig. 8 Spontaneous malformation seen in a chicken embryo: double anlage of the head fold (Picture courtesy of H. Sydow, Göttingen, Germany)

In this section we want to present examples of normal and abnormal development as we have seen them in our studies in our labs over the past 30 years using scanning electron microscopy (SEM). We use the form of an embryological atlas following the old motto “A picture says more than a thousand words.” We focus on the following developmental processes: 1. Normal and abnormal foregut development (chicken embryos) 2. Normal and abnormal development of the diaphragm (rat embryos) 3. Development of the midgut (rat embryos) 4. Normal and abnormal development of the hindgut (mice and rats) 5. The development of the external genitalia and the urethra (rat embryos) 6. Testicular descent (rat embryos)

Foregut Development Normal Foregut Development Traditionally, foregut malformations like esophageal atresias and tracheoesophageal fistulas are explained by a faulty formation of the so-called “tracheoesophageal septum.” It is believed that normal septation takes place in two steps: Fig. 9 Animal models: a newborn piglet with anorectal malformation (Picture courtesy of W. Lambrecht, Hamburg, Germany)

embryos with experimental malformations but also the study of normal animal embryos. Today, much information in current textbooks on human embryology stems actually from studies done in animals of varies species. Many of these are outdated. The wide use of transgenic mice in order to mimic congenital malformations makes morphological studies of the organ systems in normal mice mandatory. Otherwise the interpretation of the effects by deletion of genetic information can be very difficult or even misleading.

I. Lateral endodermal ridges appear in the primitive foregut which fuse and form the tracheoesophageal septum. II. This solid endodermal septum is partly removed by apoptosis and substituted by mesenchymal cells (Fig. 3). This theory had been described in detail by Rosenthal (1931) and Smith (1957). However, neither Zaw Tun (1982) nor O’Rahilly and Müller (1984) were able to confirm these sequences of embryological events. According to them, the term “separation” is a misnomer as the formation of the trachea is simply the result of the

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Fig. 10 Embryology of the esophagus: SEM studies in chicken embryos. (a) The foregut of a chicken embryo of stage 20/21, 3.5 days old. (b) The foregut is opened from lateral. The inner surface of the foregut is seen. Notice the absence of lateral folds (arrows). ES esophagus, TR trachea, * = tip of the tracheoesophageal fold. (c) View into the foregut from cranial. The tip of the tracheoesophageal fold can be seen. Notice the absence of fusion (higher

magnification in (d). ES esophagus, TR trachea. (e) Process of fusion in the outflow tract of an embryonic heart (chicken embryo). Cushions in the outflow tract of the heart (c) fuse to form a septum. (f) Notice the fusion line which can be seen in an older embryo (arrows) (Pictures 10 e, f courtesy of G. Steding, Göttingen, Germany). SEM Pictures 10a–d © Dietrich Kluth

downgrowth of the respiratory diverticulum (Fig. 3) (Merei and Hutson 2002). Using SEM, we studied the normal development of the foregut in chicken embryos (Kluth et al. 1987; Metzger et al. 2011a; Kluth and Habenicht 1987). The first goal of these studies was to see if lateral endodermal ridges appear inside the foregut and if they fuse (Fig. 10). However, in our

studies we were unable to identify ridges in the lateral foregut wall. Furthermore, signs of fusions of lateral foregut components were also not seen. As a reference, we added SEM pictures of the outflow tract in chicken hearts (pictures 10e, f courtesy of G. STEDING, Göttingen, Germany). Here, ridges appear which fuse and form the septa of the conus and the truncus. Note that a line of fusion can be seen as an indicator that fusion

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Fig. 11 Embryology of the esophagus: formation of the respiratory tract. (a) Lung buds are the forerunners of the bronchi (LB). CF common space of the foregut. (b) The bronchi start to develop (L Br). A trachea is not visible yet. CF common space of the foregut. (c) The trachea (Tr) is

still part of the common foregut. LaF larynx anlage, ES esophagus, L Br bronchi, St stomach, ** = fold which marks the border between the pharynx and esophagus. (SEM Pictures © Dietrich Kluth)

actually took place. As no signs of fusion can be demonstrated in the foregut, theories dealing with improper formations of the tracheoesophageal septum are obsolete (Zaw Tun 1982). The second goal was to visualize the early formation of the lung bud (Fig. 11). In our series of embryos, we could demonstrate that after the formation of the early lung anlage, two lung buds appear, which are the forerunners of the bronchi. The anlage of the trachea itself is seen later as the floor of a “common foregut” chamber (Metzger et al. 2011a). Thus, not the trachea but the bronchi are the first organs of the respiratory tree that develop. This speaks against the idea of a simple downgrowth of the tracheal anlage as assumed by Zaw Tun and O’Rahilly and Müller (Zaw Tun 1982; O’Rahilly and Muller 1984). The third goal was to identify possible mechanisms of differentiation of the foregut into the larynx, pharynx, trachea, and esophagus. In our embryos, we could identify typical markers in the foregut (Fig. 12). In the dorsal aspect of the foregut, a fold appears which marks the borderline between the pharynx and esophagus. Cranially the larynx develops, and caudally, a fold appears between the developing trachea and the esophagus. In the next developmental steps, these folds approach each other but do not fuse. As a result,

the area of the common foregut is reduced in size and later forms the pharyngo-tracheal canal (Kluth et al. 1987). The formation of esophageal atresia (Fig. 13) Although a number of models for abnormal foregut development exist, a clear morphological description of the embryological events that finally lead to esophageal atresias is still missing. Based on our observations, the development of the malformation can be explained by disorders either of the formation of the folds or of their developmental movements (Kluth et al. 1987; Metzger et al. 2011a; Kluth and Habenicht 1987): (a) Atresia of the esophagus with fistula (Fig. 13C1): The dorsal fold of the foregut bends too far ventrally. As a result the descent of the larynx is blocked. Therefore the common tracheoesophageal space remains partly undivided and lies in a ventral position. Due to this ventral position, the common space differentiates into trachea. (b) Atresia of the trachea with fistula (Fig. 13C2): The foregut is deformed on its ventral side. The developmental movements of the folds are disturbed, and the tracheoesophageal space is dislocated in a dorsal direction, where it differentiates into esophagus.

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Fig. 12 Embryology of the esophagus: the common space of the foregut is reduced in size by a system of folds. (a) The trachea is still part of the common space (CF). LaF Larynx anlage. (b) The size of the CF common foregut is reduced by the growth of folds, which are formed by the

larynx fold (LaF) from cranial, the tracheoesophageal fold (*) from caudal, and the fold between the pharynx and esophagus (**) from dorsal. (SEM Picture and schematic drawing © Dietrich Kluth)

(c) Laryngo-tracheo-esophageal clefts (Fig. 13C3): Faulty growth of the folds results in the persistence of the primitive tracheoesophageal space.

the diaphragmatic development. For practical reasons it is essential to note that the early diaphragm consists of two parts: (a) The septum transversum which, in young embryos, is identical to the floor of the pericardium (b) The structures that surround the pleural cavity. They are: I. The posthepatic mesenchymal plate (PHMP) (Irtani 1984), which covers the dorsal aspect of the liver and is in continuity to the septum transversum ventrally and cranially. II. The pleuroperitoneal fold (PPF) which separated the pleura from the peritoneal cavity. This fold connects ventrally to the septum transversum and the PHMP and dorsally to the mesonephric ridge (Mayer et al. 2011). This PPF is a structure that is identical to the pleuroperitoneal membrane of the old literature (Kluth et al. 1989). III. The dorsal mediastinum which contains the esophagus, the trachea, and the aorta.

In our collection of chicken embryos, we came across an embryo with abnormal foregut features (Fig. 13b). When compared to normal embryos of the same age group (Fig. 13a), the following statements can be made: (I) Obviously, the pharynx ends blindly. (II) The dorsal part of the common foregut space is missing. (III) The ventral part of the common space has the size of a trachea. (IV) This foregut looks like the hypothetical form C1 in Fig. 13.

Development of the Diaphragm Normal Development The traditional theories of diaphragmatic development have been summarized by Kluth et al. (1989). Using SEM, we have recently restudied

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Fig. 13 Embryology of the esophagus: hypothetical formation of foregut malformations. (a) Normal foregut of a chicken embryo, view from lateral into the foregut. Notice the reduced size of the common foregut space (***) due to the development of the folds. La Larynx. (b) Chicken embryo with a spontaneous foregut malformation. The pharynx ends blindly. Part of the trachea is in normal position and of tracheal size. The dorsal part of the common foregut space is missing (*). (c) Hypothetical explanation of foregut maldevelopment. (C1) The dorsal fold (*) between the pharynx and larynx grows too deep into the

common foregut space. Consequently, the rest of the common space develops into trachea, and an esophageal atresia with lower fistula develops. (C2) The common foregut space is reduced in size from ventral (*). Consequently the rest of the common space develops into esophagus, and a tracheal atresia with fistula occurs (very rare). (C3) Impaired development of the dorsal fold and the tracheoesophageal fold leads to an undivided common foregut space and a laryngo-tracheo-esophageal cleft. (SEM Picture and schematic drawing © Dietrich Kluth)

According to our SEM studies, the PHMP plays the most important role in normal diaphragmatic development. In Figs. 14 and 15, the closure

process of the pleuroperitoneal openings (PPO) is depicted. At embryonic day (ED) 13, the formation of the PHMP and its lower border can be seen

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Fig. 14 Normal development of the diaphragm: caudal growth of the posthepatic mesenchymal plate (PHMP) (Irtani 1984). (a) Rat embryo, ED 13. View at the dorsal part of the diaphragm. The dorsal diaphragm is short. The black line marks the caudal border of the PHMP. Arrows

indicate the direction of future PHMP growth. Note the large area of the liver still uncovered by the PHMP. (b) Rat embryo 13.5 days. Note the caudal growth of the PHMP within 12 h (second dark line). The uncovered liver is markedly smaller. (SEM Pictures © Dietrich Kluth)

(Fig. 14a). The PHMP then expands dorsolaterally at embryonic day 13.5 (Fig. 14b), establishing a new lower border. In Fig. 15, the final closure of the PPO is shown. In this process the PHMP starts to cover the last free areas of the liver (Fig. 15a). In this process, the pleuroperitoneal fold (PPF) plays only a minor role. In the literature, the nomenclature of the various parts of the diaphragm is confusing. We use the term PPF for a structure which was formally known as pleuroperitoneal membrane (Kluth et al. 1989; Mayer et al. 2011). The term PPF is used differently by Greer and coworkers (Clugston et al. 2010). Their PPF is very similar to the PHMP as described by IRITANI and us but seems to include the ventral part of our PPF.

(b) Failure of muscularization of the lumbocostal trigone and pleuroperitoneal canal, resulting in a “weak” part of the diaphragm (Gray and Skandalakis 1972a; Holder and Ashcraft 1979) (c) Pushing of the intestine through posterolateral part (foramen of Bochdalek) of the diaphragm (Bremer 1943) (d) Premature return of the intestines into the abdominal cavity with the canal still open (Gray and Skandalakis 1972a; Holder and Ashcraft 1979) (e) Abnormal persistence of the lung in the pleuroperitoneal canal, preventing proper closure of the canal (Gattone and Morse 1982) (f) Abnormal development of the early lung and posthepatic mesenchyme, causing non-closure of pleuroperitoneal canals (Irtani 1984)

Abnormal Development In the past, several theories were proposed to explain the appearance of posterolateral diaphragmatic defects: (a) Defects caused by improper development of the pleuroperitoneal membrane (Grosser and Ortmann 1970; Gray and Skandalakis 1972a; Holder and Ashcraft 1979)

Of these theories, failure of the pleuroperitoneal membrane to meet the transverse septum is the most popular hypothesis to explain diaphragmatic herniation. However, using SEM techniques (Kluth et al. 1989; Mayer et al. 2011), we could not demonstrate the importance of the pleuroperitoneal membrane for the closure of the so-called pleuroperitoneal canals (Fig. 15).

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of congenital diaphragmatic hernia (CDH) development lacks any embryological evidence. Furthermore the proposed timing of this process is highly questionable (Kluth 1993).

Animal Model An animal model for diaphragmatic hernia has been developed (Ambrose et al. 1971; Tenbrinck et al. 1990; Kluth et al. 1990; Costlow and Manson 1981; Irtani 1984) using nitrofen as noxious substance. In these experiments CDHs were produced in a reasonably high percentage of newborns (Kluth et al. 1990). We collected a number of affected embryos of different age groups and studied these using SEM (Kluth and Tander 1995; Kluth 1993). Our results (Figs. 16 and 17) are as follows:

Fig. 15 Normal development of the diaphragm: closure of the pleuroperitoneal openings (PPO). Rat ED 15 (a) and ED 16 (b). Most of the liver (Li) is covered by the posthepatic mesenchymal plate (PHMP). At ED 16 the only intra-abdominal organ seen is the tip of the gonads (Go). (SEM Pictures © Dietrich Kluth)

It is still speculated that delayed or inhibited closure of the diaphragm will result in a diaphragmatic defect that would allow herniation of the gut into the fetal thoracic cavity. In a series of normal staged embryos, we measured the width of the pleuroperitoneal openings and the transverse diameter of gut loops (Kluth et al. 1995a). On the basis of these measurements, we estimated that a single embryonic gut loop requires at least an opening of 450 μm size to herniate into the fetal pleural cavity. However, in none of our embryos, the observed pleuroperitoneal openings were of appropriate dimensions. This means that delayed or inhibited closure of the pleuroperitoneal canal cannot result in a diaphragmatic defect of sufficient size. Herniation of the gut through these openings is therefore impossible. Thus the proposed theory about the pathogenetic mechanisms

(a) Timing of diaphragmatic defect appearance. Iritani (Irtani 1984) was the first to notice that nitrofen-induced diaphragmatic hernias in mice are not caused by an improper closure of the pleuroperitoneal openings but rather the result of a defective development of the posthepatic mesenchymal plate (PHMP). In our study in rats, clear evidence of disturbed development of the diaphragmatic anlage was seen on ED 13 on the left and ED 14 on the right diaphragm anlage (Fig. 14) (Kluth and Tander 1995; Kluth et al. 1996). In all embryos affected, the PHMP was too short. This age group is equivalent to 4–5 week-old human embryos (Kluth and Tander 1995). (b) Location of diaphragmatic defect. In our SEM study, the observed defects were localized in the area of the PHMP (Fig. 14). We identified two distinct types of defects (Haeckel 1975): large “dorsal” defects and (Schwalbe 1906) small “central” defects (Kluth and Tander 1995). Large defects extended into the region of the pleuroperitoneal openings. In these cases, the closure of the pleuroperitoneal openings was usually impaired by the massive ingrowth of the liver (Figs. 14 and 15). If the defects were small, they were consistently isolated from the pleuroperitoneal openings which closed normally at the 16th or 17th day of gestation. Thus, in our embryos with

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Fig. 16 Dorsal diaphragms after nitrofen exposure at rat ED 11.5. (a, b) Rat embryo at ED 14. The abnormal anlage of the right diaphragm is easy to see. Dotted arrows mark the diameter of the uncovered liver (Li). On the left, the development of the posthepatic mesenchymal plate (PHMP) is normal. On the right, the PHMP stopped to grow to caudal. (c) Rat ED 17. A small hernia (liver) can be seen. Note the position close to the vena cava (large arrow). The small

arrow points to the closed pleuroperitoneal openings (PPO). (d) Rat ED 18. The hernia is big. Two lobes of the liver project into the thorax. The big arrow points to the vena cava. Small arrows mark the border of the PPO, which is open due to the ingrowth of the liver. Note that the size of the diaphragmatic defect is much larger than the PPO itself. (SEM Pictures © Dietrich Kluth)

CDH, the region of the diaphragmatic defect was a distinct entity and was separated from that part of the diaphragm where the pleuroperitoneal “canals” are localized. We conclude therefore that the pleuroperitoneal openings are not the precursors of the diaphragmatic defect. (c) Why lungs are hypoplastic. Soon after the onset of the defect in the 14-day-old embryo, the liver grows through the diaphragmatic defect into the thoracic cavity (Fig. 14). This indicates that from this time on, the available thoracic space is reduced for the lung, and

further lung growth is hampered. In the following stages, up to two- thirds of the thoracic cavity can be occupied by the liver (Figs. 16 and 17). Herniated gut was found in our embryos and fetuses only in late stages of development (21 days and newborns) (Fig. 17). In all of these, the lungs were already hypoplastic, when the bowel entered the thoracic cavity (Kluth and Tander 1995).

Based on these observations, we conclude that the early ingrowth of the liver through the

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Fig. 17 Huge hernias after nitrofen exposure. (a) Rat ED 20. In none of our embryos, the gut could be found in this age group. (b) Rat ED 21. In this age group and older

animals, the gut can be found inside the thoracic cavity. (SEM Pictures © Dietrich Kluth)

diaphragmatic defect is the crucial step in the pathogenesis of lung hypoplasia in CDH. This indicates that growth impairment is not the result of lung compression in the fetus but rather the result of growth competition in the embryo: the liver that grows faster than the lung reduces the available thoracic space. If the remaining space is too small, pulmonary hypoplasia will result.

thus form the septum. Van de Putte (vd Putte 1986) denied the existence of any process of septation. In the recent years we studied the cloacal development in rats and SD-mice embryos using SEM techniques (Kluth et al. 1995a, 2011a; Kluth and Lambrecht 1997). The first goal of these studies was to see if lateral ridges appear inside the “cloaca” and if these actually fuse to form an endodermal septum (Fig. 18). As in the foregut of chick embryos, we were unable to see lateral ridges (Fig. 18c) projecting into the cloacal lumen. Signs of median fusion of lateral cloacal parts were also lacking (Fig. 18a, b). However, in contrast to Van de Putte (vd Putte 1986), our SEM studies indicate that downgrowth of the tip of the urorectal fold takes place (Fig. 19a, b), although it is probably not responsible for the formation of cloacal malformations. Our findings on normal embryology of the hindgut were:

Development of the Hindgut Normal Development As in the foregut, a process of septation has been postulated for the proper subdivision of the “cloaca” into the dorsal anorectum and the ventral sinus urogenitalis. Disorders in this process of differentiation are thought to be the cause of cloacal anomalies such as persistent cloaca and anorectal malformations (Stephens 1963). However, for many years, this process of septation has been under dispute. Some authors (Toumeux 1888; DeVries and Friedland 1974) believe that the descent of a single fold separates the urogenital part from the rectal part by ingrowth of mesenchyme. Others (Retterer 1890) think that lateral ridges appear in the lumen of the cloaca, which progressively fuse along the midline and

(a) The “cloaca” is not subdivided into two equal parts (Fig. 19a, b). The much larger ventral part gives rise to the future distal urethra. (b) The dorsal “cloaca” contains the future anorectal region. The future anal opening is situated in the dorsal part of the “cloacal’ membrane,” close to the tail fold (Fig. 19b).

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Fig. 18 Normal development of the hindgut. Rat ED 14. (a) The ventral part of the cloaca is removed. As in the foregut, signs of fusion are lacking. (b) Schematic drawing of the situation in (a). (c) After removal of the lateral wall of the cloaca, internal ridges which could form an urorectal septum are not detectable. (SEM Pictures and schematic drawing © Dietrich Kluth)

Fig. 19 Normal development of the hindgut. a, b The “cloaca” (c) in a rat embryo ED 14.5 has the following features: proximal urethra (PU), distal urethra (DU), rectum (HG), tail gut (TG), cloacal membrane. The line marks the border between the rectum and urethra. The schematic drawing shows the situation in a rat embryo ED 14. Note

that the “cloaca” is not equally divided by the line. The gray area in the schematic drawing marks the area of the future anus. It lies in the dorsal part of the cloacal membrane close to the tail fold. (SEM Pictures and schematic drawing © Dietrich Kluth)

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Fig. 20 Normal (a) and abnormal hindgut (c) in heterozygous SD-mouse embryos. Note that in the abnormal hindgut, the dorsal cloaca, which contains the area of the future anus, is completely missing. As a result, the rectum keeps in contact with the urethra too high (so-called

fistula). The cloacal membrane (CM) is too short. In (b, d) the findings are summarized in schematic drawings. A future bladder, U ureter, W WOLFF duct, HG rectum (hindgut), C “cloaca,” TG tail gut. (SEM Pictures and schematic drawing © Dietrich Kluth)

Abnormal Development As already mentioned, a number of animal models exist which allow embryological studies of abnormal hindgut development. In our studies we used embryos obtained from SD-mice. The SD-mouse is a spontaneous mutation of the house mouse, characterized by a short tail (Fig. 5). Homozygous or heterozygous offspring of these mice shows skeletal, urogenital, and anorectal malformations (Kluth et al. 1991). Therefore, these animals are ideal for detailed studies of anorectal malformations.

In all affected embryos, we made the following observations (Fig. 20a–d): (a) Compared to normal embryos (Fig. 20a, b), we found abnormally shaped cloacas. The dorsal part was always missing (Fig. 20c, d). (b) The cloacal membrane was always too short (Fig. 20c, d). In all cases the dorsal part of the cloacal membrane was absent. (c) The proximal hindgut joined the cloaca at an abnormal position (Fig. 20c, d).

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Figure 21 summarizes the developmental processes in a sketch.

Development of the External Genitalia and the Urethra

D. Kluth and R. Metzger

Impairment of this process of fusion is thought to result in the different forms of hypospadias (Gray and Skandalakis 1972b). In order to get more information about this process, we studied the formation of the external genitalia in staged rat embryos and fetuses (Kluth et al. 1988, 2011a).

Many investigators (Felix 1911; Spaulding 1921; Glenister 1958) believe that the urethra develops by fusion of the paired urethral folds (Fig. 22) which takes place following the disintegration (rupture) of the ventral part of the cloacal membrane, the so-called “urogenital membrane.”

Normal Development of the External Genitalia This study was carried out in normal rat embryos and fetuses between embryonic day 17.5 (Fig. 22) and embryonic day 20 (Fig. 24).

Fig. 21 Hypothetical line of events in anorectal malformations. (a) In young embryos, the cloacal membrane is too short. (b) As a result, the dorsal part of the

“cloaca” is missing, which normally contains the area of the future anal canal. (c) The rectum remains attached to the future urethra. (Schematic drawing © Dietrich Kluth)

Fig. 22 Normal genital development. It is a common assumption that the “cloacal membrane” ruptures not only in the dorsal (anal) part but also in the ventral (urethral) part. This would lead to a situation as depicted in (a). AP anal pit, GP glans penis, UO urethral opening, US

urethral sulcus, SS scrotal swelling. In (b) the phallus of a normal rat embryo is shown. In this age group (ED 17,5), the sex of the embryo cannot be estimated by the appearance of the outer genitals. (SEM Picture © Dietrich Kluth)

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Fig. 23 Rupture of the dorsal cloacal membrane in a rat embryo (ED 17.5). (a, b) The rupture of the membrane is clearly seen. (c) In high magnification the situation is visible in detail. Half of the genitals is removed by micro preparations. The tip of the urorectal fold can be seen (URF). Ventrally the opening of the urethra is seen (UO). The rectum (Re) opens dorsally (AO). Fusion of the URF with the cloacal membrane, as assumed by some researchers, does not take place. EC ectoderm, CP cloacal plate, d Ur distal urethra, p Ur proximal urethra. (SEM Pictures © Dietrich Kluth)

(a) Rupture of the cloacal membrane (Fig. 23). At embryonic day 17.5, the dorsal disintegration of the cloacal membrane can be seen (Fig. 23a, b). The ventral (urethral) part of the cloacal membrane remains intact. In Fig. 23c, this process of disintegration is seen in more detail. The ectodermal part of the cloacal membrane shows clear signs of disintegration. The tip of the urorectal fold is seen which later forms the perineum. Ventral to the tip of the urorectal fold, an opening is seen which is in connection to the distal urethra. Dorsally the anal opening is seen. At this time point, the external genitals allow no differentiation between the sexes. (b) Further development of the external genitalia.

A rupture of the ventral part of the cloacal membrane cannot be seen in older embryos and fetuses. In males, the transient urethral opening disappears. Later a “raphe” is seen in this position (Fig. 24a). In females, this “raphe” is missing (Fig. 24b). (c) Special dissections of a rat embryo at embryonic day 18.5 allow the following statements (Fig. 25a–c): The urethra is composed of two parts, the proximal and the distal part. The epithelium of the distal part reaches to the tip of the phallus. It is interesting to see that the urethra is connected to the perineal region by a short canal, the so-called “cloacal canal.” In our opinion this is the future female urethra.

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Fig. 24 Rat fetuses ED 20, (a) male rat, (b) female rat. The sex is discernable by external inspection of the genitals. Note the “raphe” (*) in (a), which is typical for the

Summarizing our results we found: (a) In rats, the urethra is always present as a hollow organ during urethral embryogenesis and that it is always in contact with the tip of the genitals. (b) Initially a double urethral anlage exists. The differentiation in female and male urethra happens in rats more than 18.5 days old. (c) We had no evidence for the disintegration of the urogenital cloacal membrane and a fusion of lateral portions within the perineum.

Abnormal Development of the External Genitalia (Hypospadia Formation) In our opinion, more than one embryological mechanism is at play in the formation of the hypospadia complex (Kluth et al. 1988, 2011a). The moderate degrees, such as the penile and glandular forms, represent a developmental arrest of the genitalia. They take their origin from a situation comparable to the 20-day-old embryo. Consequently the penis, not the urethra, is the primary organ of the malformation. Perineal and scrotal hypospadias are different from the type discussed previously. Pronounced signs of feminization in these forms suggest that we are dealing

male phallus. This raphe is not the result of fusion, as generally believed. In female rats this “raphe” is missing. (SEM Pictures © Dietrich Kluth)

with a female-type urethra. Origin of this malformation complex is an undifferentiated stage as may be seen in the 18.5-day-old rat embryo.

The Development of the Midgut Traditional Theories Traditionally, the midgut development is described as a process of “rotation.” In this process the following parts are involved: the distal part of the duodenum, the small bowel, and most parts of the big bowel. The process of rotation takes place in two phases (Mall 1898; Frazer and Robbins 1915): (a) In the first phase, the midgut loop develops inside the umbilicus (so-called “physiological herniation of the midgut”). Here, a 90-anticlockwise rotation around the axis of the mesentery is thought to take place. (b) After the “return” of the midgut into the abdominal cavity, another anti-clockwise “rotation” of 180 is thought to take place inside the abdominal cavity (second phase). As a result, the region of the cecum moves to the right, thus overcrossing the mesenteric

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Fig. 25 Phallus of a rat ED 18.5. (a) The sex is not discernable by external inspection. The lateral portion of the phallus and the lateral wall of the urethra are removed. p Ur proximal urethra, d UR distal urethra, Re rectum. (b) The sketch describes the situation in (a): p Ur proximal urethra, d UR distal urethra, CC urethral opening in females. Note that the urethra in this stage is not sexually determined. The female urethra is short and ends at the CC opening. (c) The male urethra is formed by the distal urethra, which extends to the tip of the phallus. Sy symphysis, Ur urethra, C cloacal membrane, Re rectum. (SEM Pictures and schematic drawings © Dietrich Kluth)

root, while the flexura duodeno-jejunalis is pushed to the left beneath the root of the mesentery (see schematic drawing in Fig. 1b) (Mall 1898; Frazer and Robbins 1915). These two phases sum up 270 . In contrast to this description, Grob (1953) subdivides this intra-abdominal process of rotation into two steps of 90 each.

Own Observations We studied midgut development in rat embryos using SEM (Figs. 26, 27, and 28) (Metzger 2011a; Kluth et al. 1995b, 2003). Starting at embryonic day 13, the following parts of the midgut loop can be seen (Fig. 26a):

(a) A central part with the duodenum and the distal colon close to the root of the mesentery. (b) A ventral part inside the extra embryonic coelom of the umbilicus (so-called “physiological herniation”). Here the cecum and the distal small bowel can be identified. (c) A middle part which connects the central part with the ventral part inside the umbilicus. Here the umbilical vessel, the small bowel on the right, and the proximal part of the colon on the left can be seen (Figs. 26b and 27d). In the further development (ED 14–16), growth activities are seen in the area of the duodenum and inside the extraembryonic coelom.

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Fig. 26 Normal development of the midgut. (a) Rat embryo ED 13. The early midgut consists of three parts: a central part with the primitive duodenal loop (du), an extraembryonal part in the extraembryonic sac of the umbilicus (ce), and a straight part in between (sb). (b, c) The

development of the central part, the duodenal loop (du), is seen. Note that the duodenojejunal junction is pushed beneath the root of the mesentery (arrows in c). This is caused by longitudinal growth of the duodenum. sb mall bowel loops, li liver. (SEM Pictures © Dietrich Kluth)

Figure 26 shows the steps important for the duodenal developmental. In Fig. 26b (rat embryonic day 15) the duodenojejunal loop has been formed due to longitudinal growth of the duodenum. Further growth pushes this loop beneath the root of the mesentery (Fig. 26c). Figure 27 shows the development of the intraumbilical loops. These loops are the result of longitudinal lengthening of the small gut. Note the absence of any signs of rotation around the axis of the mesentery in Fig. 27d in a phase of active loop development inside the extra embryonic coelom. Figure 28 shows the “return” of the midgut into the abdominal cavity. The cecum is seen inside the abdominal cavity in a ventral position close to the abdominal wall (embryonic day 17). The colon is entirely to the left in this phase of development. It is a small bowel loop which is still extraembryonic inside the umbilicus. In this phase of small bowel “return,” the bowel loops have already developed locally inside the abdominal cavity (Fig. 26c). We conclude from our observations that the midgut can be subdivided in three parts, of whom the central and the ventral parts are of major importance. Localized longitudinal growth in the area of the duodenum leads to the formation of the duodenojejunal loop and its final position beneath the root of the mesentery. At the same time, localized growth of the small bowel has led

to the formation of bowel loops inside the umbilicus and, later, inside the abdominal cavity. The growth activity of the large bowel is minimal, compared to that of the small bowel. Neither in the phase of loop formation inside the extraembryonic coelom of the umbilicus nor in the phase following the “return” of the gut into the abdominal cavity rotation of the gut around the axis of the mesentery can be observed. All processes in midgut development are the result of longitudinal lengthening of gut.

Testicular Descent Since John Hunter in 1762, many researchers studied the embryology of testicular descent. In many of these studies, the importance of the gubernaculum during this process has been highlighted. However, a clear illustration of this rather simple process is still lacking (Heyns and Hutson 1995). Today, most researchers in the field (Heyns 1987; Hullinger and Wensing 1985; Wensing 1988; Hutson et al. 2015) see two developmental phases during testicular descent: (a) The intra-abdominal descent: In this phase, the testis, which initially lies in close contact to the kidney, moves into the inguinal area.

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27

Fig. 27 Normal development of the midgut. (a) Rat ED 13. The cecum and the most distal part of the small gut are seen in the extraembryonic sac of the umbilicus. Dotted arrows indicate the border between extraembryonic and intraembryonic coelom. (b, c) Rapid lengthening of the small bowel leads to the formation of loops

inside the extraembryonic sac of the umbilicus. Arrows indicate the direction of growth. (d) Note that during this process, rotation around the axis of the mesentery does not take place. ce cecum, sb small bowel, co colon, mV mesenteric vessel. (SEM Pictures © Dietrich Kluth)

(b) The inguinal descent: In this phase the testis moves into the area of the scrotum.

both gonads are initially in close approximation to the kidneys. Starting at embryonic day 16.5, the testis moves away from the lower pole of the kidney. On ED 19 the testis is located between the lower kidney pole and the roof of the bladder (Fig. 30a) and moves toward the bladder neck at ED 21 (Fig. 30b). This brings the intraabdominal descent to an end and the inguinal descent starts. At the end of the intra-abdominal descent (ED 22), the bulb of the gubernaculum is still visible. (Fig. 31a). A little later, around birth

We (Fiegel et al. 2010, 2011) studied the morphology of testicular descent in rat embryos between embryonic day 15 and 20 using SEM in order to illustrate in detail the various steps of the testicular development. While in rat embryos at embryonic day 15 male and female gonads look still identical (Fig. 29a), they become clearly distinguishable in rats of embryonic day 16 (Fig. 29b). The male gonad is getting thicker and slightly shorter than the female gonad, but

28

Fig. 28 Normal development of the midgut. Rat ED 17. (a) The cecum (ce) is found in the abdominal cavity. A small bowel loop is still outside in the umbilical sac

D. Kluth and R. Metzger

(arrow). Co colon, du duodenum. (b) Higher magnification of the area of the ventral body wall. Ce cecum, co colon. (SEM Pictures © Dietrich Kluth)

(embryonic day 22), the bulb disappears partially and the processus vaginalis peritonei (PVP) develops (compare with Fig. 31b). Notice the rest of the bulb at the lower pole of the PVP. In this phase, the corda of the gubernaculum is still visible and attached to the caudal part of the epididymis, which has entered the PVP. At birth and later, the testis finally enters the PVP (Fig. 31c).

Fig. 29 Descensus of the testis. Rat ED 15, female rat in (a), male rat in (b). Notice the difference in the size of the male and female gonads (go). Both gonads lie in close approximation to the kidneys (ki). (SEM Pictures © Dietrich Kluth)

The Role of the Gubernaculum In our series, we studied the formation and the fate of the gubernaculum (Fig. 32). In rat embryos at embryonic day 16, the gubernaculum consists of two parts, the gubernacular bulb and the corda of the gubernaculum (Fig. 32a). The corda is rather attached to the lower anlage of the epididymis (Fig. 32a–c) than to the testis, as it is often described in the literature. Furthermore, it is often assumed that the testis is pulled downward by corda and bulbus. While this – in initial stages – seems to be morphologically possible, we identified later stages, where the testis and gubernaculum were positioned in such a way that pulling of the testis by the gubernaculum seems to be impossible (Fig. 32c, e).

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29

Fig. 30 Testicular descent: intra-abdominal descent (first phase). (a) Male rat, ED 19. The gonads (go) have lost contact to the lower pole of the kidneys (ki) and lie in the middle portion between the kidney and bladder (bl). (b) Male rat, ED 21. The gonads are now

close to the bladder in the inguinal area. This movement relative to the urinary bladder cannot be attributed to the relatively ascent of the kidneys. (SEM Pictures © Dietrich Kluth)

Fig. 31 Testicular descent: inguinal descent (second phase). (a) Male rat ED 21. The testis (T ) has reached a position close to the inguinal region. The bulbic gubernaculum (GB) is still present. BL bladder, AE epididymis. (b) Male newborn rat, D 0. The bulbic part of the gubernaculum (GB) disappeared, and the processus vaginalis peritonei is formed (PVP). The border between peritoneal cavity and PVP is marked

by arrows. The epididymis has entered the PVP. The corda of the gubernaculum is still visible. (c) Male newborn D 1–5. Not only the epididymis but also half of the gonads (T ) has entered the PVP. The gubernaculum has completely disappeared. Arrows mark the border between the peritoneal cavity and the PVP. AE epididymis. (SEM Pictures © Dietrich Kluth)

Thus in our findings, we cannot support the opinions about the role of the gubernaculum during the testicular descent. Its main role seems to be its transformation into the PVP.

We believe that intra-abdominal pressure probably plays an active role at least in the phase of the inguinal phase of testicular descent.

30

Fig. 32 Testicular descent: in this series of SEM pictures, the morphology of the gubernaculum is shown (rat ED 19). (a, b) Here the gubernaculum consists of two parts, the corda of the gubernaculum (arrows in a, b) and the bulbus of the gubernaculum (GB). The corda inserts rather into the caudal anlage of the epididymis (AE)/mesonephric ridge than into the testis (T ), as often assumed. BL bladder. (c) While in (a, b) tension caused by the gubernaculum seems to be theoretically possible, (c) demonstrates that the testis (T ) is rather blocked by the bulb of the gubernaculum (GB) than pulled. Rat ED 21, AE epididymis. (d) Many

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The Epidemiology of Birth Defects Edwin C. Jesudason

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Birth Prevalences Are the Cornerstone of Birth Defects Epidemiology . . . . . . . . . . . . . . . . Why Is It Important to Collect Birth Defects Data? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Practical Challenges of Birth Defects Epidemiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethical and Scientific Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On the “Causation” of Birth Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Birth Defects Epidemiology and the Pediatric Surgeon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

36 36 36 38 38 40 42

Conclusion and Future Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Cross-References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Abstract

Birth defects are emerging as the leading cause of infant death worldwide. Their epidemiological investigation was prompted by the recognition of congenital rubella syndrome and of thalidomide-related phocomelia. Pediatric surgeons require good data on birth defects as a baseline for reporting their own outcomes. Hence, birth defects data are the foundation to quality control and improvement in neonatal surgery. However, good epidemiological study of birth defects is challenged practically by limited resources and dispersed populations and scientifically by prioritization of reductionist

genetic investigations. Instead, it may be more helpful to see birth defects as complex systems problems, akin to surgical errors. As such, better understanding of birth defects may require surgeons equipped with “engineer style” training in statistics, modelling, and complex dynamic systems, rather than the current vogue for molecular biology approaches. Finally, birth defects are sensitive to widely different influences ranging from assisted reproduction to depleted uranium weapons. So for a broad swathe of population health issues, birth defects may provide an early warning signal – that can be heeded only with proper epidemiological measurement. Keywords

E. C. Jesudason (*) NHS Lothian, Edinburgh, UK e-mail: [email protected]; [email protected]

Birth defects · Epidemiology · Epigenomics · Complex systems · Teratology · Fetal diagnosis and therapy

© Springer-Verlag GmbH Germany, part of Springer Nature 2020 P. Puri (ed.), Pediatric Surgery, https://doi.org/10.1007/978-3-662-43588-5_2

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36

Introduction Through human history, the most feared outcomes of pregnancy have included maternal death and birth defects. As affluence has increased, mothers now die far less often. However, affluence also affords technologies for assisted reproduction and more lethal warfare that both appear to swell the ranks of children born with birth defects (Davies et al. 2012; Hindin et al. 2005). With the decline in deaths from infectious disease, birth defects will soon be the leading cause of infant mortality (Carmona 2005). For many pediatric surgeons, birth defects represent a small but important sample of their overall work – either because rates are relatively low – or afflicted children do not live to reach them. However, if neonatal surgeons are properly to judge their outcomes and to advise expectant parents, they need to have regard for the epidemiology of particular birth defects in their catchment – and to have a feel for which of the above best explains their local rates. Modern birth defects epidemiology arose from two hazards that became apparent during the course of the last century. The first was the recognition of congenital rubella as a distinct malformation syndrome – and the later insight that this problem could be subdued through vaccination programs (Monif et al. 1965; Condon and Bower 1993). The second were the children with missing limb segments – whose mothers, badly sickened by pregnancy, had tried thalidomide as a refuge from nausea and vomiting (Taussig 1962). These children with phocomelia warned clinicians of the need for greater watchfulness, not just for ancient infections but also modern drugs (Khoury 1989).

Birth Prevalences Are the Cornerstone of Birth Defects Epidemiology Birth defects epidemiology rests on the counting of a particular birth anomaly within an overall cohort of births. This generates a birth prevalence rather than, as is often quoted, a birth incidence. Birth incidences are impractical because of the

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large and unknowable numbers of defects that will be missed over a given census period due to unrecorded miscarriage and the like. That said, birth prevalences are not straightforward either. Databases differ in whether they will include terminations for defects and also the circumstances in which they will include fetal deaths as stillbirths or exclude them as miscarriages. The latter choice is commonly made according to gestational age, but unhelpfully some registries use a weight cutoff instead. Given that many of these defects are rare, methodological choices like these can produce large artifacts in overall birth prevalences (Duke et al. 2009). Fortunately, concerted investment in multinational registries like EUROCAT has smoothed some of these differences, allowing clinicians a readier comparison between countries and over time. Inevitably, however, human choices over measurement are associated with their corresponding problems. One such is the issue of “terathanasia,” which has been suggested as a mechanism by which folate reduces the birth prevalence of neural tube defects (Stockley and Lund 2008; Wald 1991). The argument goes that folate may in fact enhance fetal loss in cases of neural tube defect (Hook and Czeizel 1997). If this loss occurs earlier and gets classified as miscarriages, the apparent birth prevalence of the particular defect falls, even though the drug is increasing the losses overall.

Why Is It Important to Collect Birth Defects Data? Given these problems, one might ask why registries strive to collect such data? The first reason is that pediatric surgeons need to judge their results in light of true prevalences and with proper appreciation of any hidden mortality, in order to improve care (Dindo et al. 2010). Neonatal surgeons have a particular need to contend with the problem of “hidden mortality” as described by Harrison et al. for congenital diaphragmatic hernia (CDH) (Harrison et al. 1978). Jaffray et al.

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showed that neglecting the presurgical deaths in CDH led to over optimistic estimates of CDH survival (Stege et al. 2003). Therefore, birth defects epidemiology sets a kind of baseline under later audits in neonatal surgery. Second, the advent of antenatal ultrasound to screen for birth defects has made it important to collect data so that worried parents can be properly informed. This is a responsibility that the profession must bear for the parents, having overseen the introduction of such diagnostic techniques. However, even though parental counselling and ultrasound screening rely on epidemiological information, the screening itself may confound good data collection: parents may seek to terminate, meaning that cases can be missed from any census without the knowledge of the researchers; alternatively, new awareness of the defect may add to the count of such birth defects (where previously none would have presented); screening may change a host of treatment choices that impact on final outcome. Congenital lung malformations fall into this category, where some lesions would likely not have presented were it not for prenatal diagnosis. Congenital diaphragmatic hernia is another example where birth prevalences and outcomes are important for the advisement of parents when considering the value of fetal interventions (Harrison et al. 2003). In the CDH field, surgeons have spent the last decade trying to establish whether tracheal occlusion is better than best postnatal management. All the while, investigators have struggled with epidemiological questions. For example, is the antenatally treated group representative of all comers or are some CDH cases being terminated beyond the notice of fetal surgeons? Regarding prognosis, do measures of fetal lung size prospectively distinguish those CDH fetuses who will survive without prenatal intervention, from those who will not? (Ba’ath et al. 2007). The third reason to audit birth defects is that, as well as becoming the leading cause of infant mortality, they are also associated with preterm birth and with long-term disability (Lumley 2003). Both are hugely costly both emotionally and financially, so study of birth defects epidemiology

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is worthwhile to try and understand these problems and to underpin the planning and provision of services. Fourth, the developing human is constantly threatened by the evolution of infectious disease, by new drugs, and by other chemicals. Birth defects monitoring is essential to ensure that new agents do not repeat the disasters seen with rubella and with thalidomide. For example, certain strains of influenza pose a greater risk to pregnant women, prompting advice that they be vaccinated. However, the safety profile of such vaccination can only sensibly be judged by epidemiological examination of their birth cohort relative to unvaccinated cohorts (Pasternak et al. 2012). Influenza is only one example where evolving infectious diseases will continue to pose new threats. So continual surveillance is needed both to check for effects of the agent itself and for the impact of any countermeasures we may recommend. Fifth, there is emerging evidence that certain types of childhood cancer are more common in those children who have had birth defects (Carozza et al. 2012; Botto et al. 2013). This risk is not shared by all defects and does not seem to apply to all pediatric cancers. However, the association is an important and instructive one. In adults the strongest population risk factor for cancer is age. In children, this does not apply straightforwardly. Instead, childhood cancer could be seen as more of a developmental defect, where even largely normal cells persist abnormally or get stuck at abnormal locations where their onward fate then becomes cancerous (Carter et al. 2012). In this paradigm, it is important to pick up the children with birth defects and to be able to follow them over time in order to understand the different possible links between the original lesion and the subsequent tumor. Finally, good birth registries can help fight the crime of selective female feticide, by pinpointing where and how these children disappear from the record (Abrejo et al. 2009). This is a vast problem that can be highlighted, by thoughtful epidemiological study of births and birth defects.

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The Practical Challenges of Birth Defects Epidemiology Ascertainment problems reverberate throughout the practice of neonatal surgery to affect issues ranging from birth defects data to postnatal problems like necrotizing enterocolitis (NEC) (Duke et al. 2009; Stege et al. 2003; Boyd et al. 2005; Forrester and Merz 2001). In the UK, NEC is now the leading cause of postsurgical death in children (NCEPOD 2011). As a problem of the preterm, it is more common in those with birth defects and early hospitalization. Yet our data collection in this population leaves much to be desired. In a recent UK audit of deaths after surgery in children, major units simply failed to submit case notes in more than 60% of deaths. The auditors were unable to do more than ask again but to no avail (NCEPOD 2011). This illustrates that collection of data for surgical outcomes in neonatal surgery leaves substantial room for improvement in the twenty-first century. In well-resourced countries, it is hard to understand why such data collection remains so problematic. One may conclude simply that surgeons do not accord such data reporting the priority it deserves. Failures to collect birth defects data are more comprehensible in settings where mothers live in remote regions, undergo seasonal migration, or are nomadic. In such circumstances, birth defects epidemiology may appear to be a low priority relative to the daily challenges of subsistence. However, this would be to overlook an important opportunity to understand population health and even the scientific basis of birth defects. For example, Africa features the greatest human genetic diversity in the world, so studies there are well placed to pinpoint any roles for genetic variation in the origins of human malformation, or other diseases too (Campbell and Tishkoff 2010). Investment in good birth defects registries is one strategy to try and embed comprehensive data collection at the earliest stage in the life course. The aim is then to recapture these children, first identified at birth, as they progress and develop. Children with birth defects remain at higher risk of needing further surgery, so it makes sense to

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follow them closely ab initio. In this approach, birth defects epidemiology can become the cornerstone for improved surgical audit from the neonatal period onward (Horton 1996, 2010).

Ethical and Scientific Considerations There is an argument that epidemiological study of birth defects is a moral good because improved understanding helps to remove the fear and blame historically associated with congenital anomalies. By showing how birth defects are common and how they feature in every population, clinicians can help parents struggling with unwarranted feelings of personal guilt. The importance of this for the parents, their affected child, and indeed other siblings should never be disregarded (Horan 1982). Similarly, good birth defects surveillance can assuage public panic when novel threats are perceived, whether from new medicines, infections, or technologies. The public is often keen to learn if new agents pose a risk to them or to their unborn children. Without proper registries, clinicians are condemned to tackle such questions from a position of ignorance, which only exacerbates population fears (Yu et al. 2005). Then there is the case that epidemiological study can help not only with the practical management of birth defects but also in the longerterm scientific understanding of such lesions. Day-to-day, surgeons treat individual patients providing an invaluable perspective. However from this vantage, clinicians may struggle to see or explain broader changes in disease patterns. For example, in recent years, epidemiological study has confirmed surgeons’ hunches that, for reasons that are unclear, the prevalence of gastroschisis has risen (Kilby 2006; Fig. 1). The identification of new factors to explain this trend will most likely require prior and ongoing surveillance of birth defects. Specifically, gastroschisis has been linked with young maternal age, vasoactive drugs, and subtle clotting defects – the latter two supporting the thesis that the defect results from a late vascular insult that leads to involution of part of the abdominal wall (Feldkamp et al. 2007). However,

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Fig. 1 “Liver-out” gastroschisis in a newborn (Image used courtesy of the author)

epidemiological surveillance has continued to add valuable information to this mix. Injuries to mothers during pregnancy are not uncommon. In fact intentional abusive injuries are well recognized. Associated with this are certain birth defects including gastroschisis (Tinker et al. 2011). In this model, the abdominal wall defect may still arise from clotting, but the latter may occur as a result of a maternal injury response. Without birth defects epidemiology, we have little way to explore such potential causes in our search for mechanism and prevention. This exploration becomes more important when it is appreciated that many adult diseases, often lifelong and expensive, appear to be set up by prenatal life (Barker 2007). So birth registries can measure fetal health to help understand the coming burden of adult disease and the preparations necessary to meet it. This thesis is most fully expanded for cardiovascular health, hypertension, and the

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metabolic syndrome, but there is reason to believe that it applies to other organ systems too. In this model, population health depends on maternofetal health, so birth defects monitoring becomes a barometer for societal well-being. The scientific enquiry into birth defects can of course dig deeper than epidemiological pattern recognition. But even for more sophisticated genomic study of birth defects, index cases need collecting and tracking to minimize bias from missing cases. So even if unmoved by the clinical and practical reasons for birth defects monitoring, it is clear that registries are a vital stepping stone for large genomic investigations looking for fundamental causes. This type of scientific investigation is important not only for the individual birth defects but also for what it tells us about such defects in general and also what it can tell the parents about causation. Here, there is an unfortunate tendency to elide congenital with genetic, i.e., to take what was present at birth, as genetic. This manifests as a tendency to pretend each congenital anomaly has a gene defect that is responsible and lends itself to popular narratives characterized as “the race to find the gene for X.” As far as possible, this unhelpful thinking needs to be addressed empirically (Lippman 1992; Gilbert and Sarkar 2000; Ahn et al. 2006). Rational genomic investigation of birth defects should really focus resources on African populations due to their greater genetic diversity (Campbell and Tishkoff 2010). Surgeons are often a little surprised and skeptical about this, imagining instead that the greatest genetic diversity lies in the mixed populations of the new world. However, the greater genetic diversity in Africa is straightforwardly explicable. Imagine each human genome represented by a particular choice of playing cards from the deck of 52. For the larger part of human history, this “deck of cards” was under development in Africa. When almost all the deck had been “finalized,” groups of humans left Africa with their card subsets, to colonize distant lands. Hence, the diversity of populations derived from this diaspora is limited more or less to the genomes with which their ancestors migrated away. Therefore, genetic diversity in Africa exceeds that in other

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continents. This has major but still unaddressed implications for medical research in general and genomic research in particular. Current genomewide association studies are often performed in very selected groups within the human species. This has every potential to omit key discoveries with great potential. So even if there is some significant and knowable genetic basis to common non-syndromic birth defects, it is important not to neglect the most diverse populations from the search (de Vries et al. 2011). And a key way to engage them is through perinatal care and birth defects monitoring. So far, it appears that few of the common birth defects arise from a single gene defect. When such genetic causes fail to materialize, it is tempting to race off toward the next big thing – epigenetics or similar (Bernal and Jirtle 2010). Imprinting can help understand syndromes like BeckwithWiedemann and Angelman (Piedrahita 2011). However, it is also unlikely that all birth defects will have a simply defined and modifiable epigenetic cause. Though initially, unsettling these observations are also liberating: they mean that in few cases do parents have to worry about repeated transmission of a problem to the next child. And for this reason, they may experience less guilt. While all this is helpful, it may be unsettling for the pediatric surgeon who is being asked to provide an answer to why this happened. For this reason, it is necessary to say something here about types of birth defects and their possible causes.

On the “Causation” of Birth Defects Conventionally, it has been helpful to teach that birth defects fall into two groups, early and late. The early ones are genuine problems in morphogenesis, and as early events, often associate with other anomalies. In this context, one can include, e.g., duodenal atresia or esophageal atresia, with their major structural lesion and common association with other malformations (Pedersen et al. 2012; Spitz et al. 1994). It has been tempting to assume that these earlier lesions have a poorer prognosis and are more likely to harbor a genetic cause. However this is not straightforwardly

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correct. For example, isolated duodenal atresia, often but not inevitably, is associated with Downs, and it often has a good prognosis – subject to any cardiac lesion (Grosfeld and Rescorla 1993). The second set of defects that confront surgeons are the late ones, and here the example is gastroschisis, an abdominal wall defect of uncertain origin. The contested argument made with gastroschisis and its associated small bowel atresias is that they result from relatively late vascular accidents (Feldkamp et al. 2007; Curry et al. 2000). This is contrasted with omphalocele – an early lesion that is sometimes multisystem and genetically based. Again, however, none of these stories is straightforward. For example, intestinal atresias can be induced in genetic knockout mice where they would seem to be early events (Nichol et al. 2011; Fairbanks et al. 2005). Similar uncertainties are present for a host of other defects too. In CDH, it is unclear how the diaphragmatic defect relates to the lung one and whether the Bochdalek lesion is a failure of closure of the pleuroperitoneal canals or a separate hole (Keijzer et al. 2000; Jesudason et al. 2000). It would seem therefore that the distinction between early and late lesions has utility mainly in reminding clinicians when they need to look most diligently for associated anomalies. Its explanatory power in terms of mechanism is perhaps not as strong as once believed. The famous experiments to induce small bowel atresia in pups by ligating the mesentery in utero, show only one way to arrive at the lesion, not necessarily the way (Nichol et al. 2011); the same point is more obvious in the field of CDH with its various surgical and nonsurgical models, each of which can produce a type of lung hypoplasia (Jesudason 2002; Mortell et al. 2006). Perhaps because genomics for birth defects has failed to yield target after target, there has been a swing back toward interest in the mechanics of development, i.e., toward a theory, for at least some defects, where physical forces contribute significantly to the observed phenotype (Nelson et al. 2005; Nelson and Gleghorn 2012). Here, however, might be a good point to call a truce and to consider an alternative and

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more practical way to see birth defects and their epidemiology. In this view, birth defects are complex phenomena with multiple inputs, ranging from the genome to physical forces (Gilbert and Sarkar 2000; Goldberger et al. 2002). In that regard, they are similar to surgical errors in as much as the majority are systemic failures that arise when several circumstances align (McCulloch and Catchpole 2011; Reason 1995, 2000). In comparison, surgeons do not seek the genomic reasons for the surgical error. Moreover, there is an acceptance that some error is inevitable in any human system – not that this excuses efforts to reduce it. By analogy, birth defects are propensities waiting to be realized when various circumstances align (Reason 1995, 2000). In other words, human development is a program that has evolved to yield mostly normal newborns but which has a finite and inherent error rate. Therefore, it is conceivable that many birth defects arise simply from variation in the normal program, without needing to posit a trigger lesion as a cause (Elowitz et al. 2002). In this model, there are multiple ways to arrange the trachea and esophagus, the most common of which is the normal anatomy. However, if for any reason this lowest free energy route is not claimed, then the organism defaults, not to randomness (any type of connection or lack thereof), but to an ordered constellation of anomalies that arise with predictable frequency. So the Type C atresia is the next commonest variant – itself echoing aspects of older evolutionary anatomy. Similarly with imperforate anus, if normality does not develop there is a default to older versions like the cloaca. If most birth defects represent error rates inherent within a normal program then it makes less sense striving to extract every piece of genetic data on them. It may be more helpful to look at the distribution of lesions between populations to test if the same alternative forms arise with the same frequencies when the normal path of development is not achieved (Pedersen et al. 2012). This view of development accords with Waddington’s famous epigenetic landscape in which the organism is represented as a ball rolling

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down the landscape to emerge between any number of potential valleys, the final choice reflecting the phenotype (Waddington 1942). In this model, development is about “canalizing” the organism, reducing its potential forms into an actual one. Again, if Waddington is right, it may be somewhat nonsensical to expect every birth defect to yield an ultimate cause. Instead much of what presents as birth defects to pediatric surgeons may represent just the stochastic error inherent in any program for normal development. Added to this, perturbations at vulnerable phases may then change the final phenotype by tipping Waddington’s ball from one valley to the next. Fortunately, most of development is robust to challenges like this, but it can be seen that a short infection (rubella), a drug exposure, or even a physical trauma at a critical time may suffice to tilt the system. Thereafter, the program will still work but now leads on to produce what we call a birth defect. Here, the difference between congenital and genetic becomes very sharp. Antenatal events may have little or nothing to do with genetics, but be manifest as congenital defects (Tinker et al. 2011). So the effort to find every case and to sequence every nucleic acid needs to be viewed with some circumspection. Not only is there the present cost and distraction of pursuing such research enterprises, there is the longer-term question about whether children’s genetic privacy is being given up before they are old enough to decide on this for themselves (de Vries et al. 2011; Grosse et al. 2010). We have already seen that anonymity can readily be breached by careful comparison of “anonymized” genomic studies and publicly available named data (Homer et al. 2008; Wjst 2010; Hayden 2013). If genomic screening is not going to yield what we need, why subject children to it at the beginning of life? (Slaughter 2007). By comparison, birth defects epidemiology can provide information for parents, surgeons, and service providers at a fraction of the current costs of genomic studies. Investing in these registries may also help determine to what extent common birth defects represent the inherent error rate of the human development program. This is a serious question given the tendency to cut

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resources for such databases, even as genetic studies are advanced. In many countries, the resources do not yet exist for large genetic studies, and it would be a pity if they were distracted from the simpler task of collecting good data on birth defects first (Boyd et al. 2005; Grosse et al. 2010).

Birth Defects Epidemiology and the Pediatric Surgeon At the end of the discussion above, a pediatric surgeon could be forgiven for feeling overwhelmed by the uncertainty and complexity of the situation, and rather put off by the inability to give simple concrete answers as to why certain birth defects arise. Reflection will however emphasize that this discomfort is useful. First, it simulates in small measure the confusion and lack of control experienced by parents when confronted by a birth defect (Horan 1982). Second, it helps reinforce that whatever the relatives may opine, the cause of birth defects is rarely straightforward and almost never reducible to an act or acts during pregnancy or periconceptual life. It is easy to forget how much human society craves explanation and – next to that – blame (Wright 2010). With each new birth defect, the focus of attention can rapidly become the parents, even at the time they are most vulnerable. Surgeons can act as protectors and advocates for the parents, by emphasizing what is not known as well as what is; by standing by the idea that such defects are usually manifestations of complex systems that are inherently unpredictable. However, some surgeons may insist on reductionist explanations, or argue it is a “cop out” not to discuss cause. It is ironic therefore that when they err in theatre, the same surgeons adhere to complex system explanations that tend not to apportion individual responsibility (Cuschieri 2003). The systems approach also has consequences for the training of pediatric surgeons. It will be appreciated that time spent peering into the genetics of birth defects using highly atypical murine models may not be the best investment for the surgical trainee or their future patients. Indeed,

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these trainees may be better off studying complex dynamic systems so they can apply this to both birth defects and to surgical safety (Lippman 1992; Gilbert and Sarkar 2000; Goldberger et al. 2002). In this context, a systems approach to birth defects represents a generic education for dealing with complex dynamics in healthcare (McCulloch and Catchpole 2011; Reason 1995, 2000). Similarly, a fuller training in statistics may be very helpful for surgeons to inform their patients. A recent study suggested that birth defect rates were doubled in babies of first cousin marriages in the Born in Bradford study (Sheridan et al. 2013). However, as the astute accompanying commentator noticed, this represented a rise from about 3–6%, which was the same uplift in risk associated a maternal age of 34 years or more. Similarly, the expert commentator unearthed some paradoxical relationships with smoking, showing that a keen sense of statistics and an appreciation of research are each helpful to interpreting papers (Bittles 2013). Together, this shows that surgeons also need to be alive to the power and pitfalls of research data in this evocative field. Having established that birth defects epidemiology is important and that surgeons need to know about it, where do surgeons go for this type of information? Unfortunately, many surgical reports on birth defects have been small institutional series with inadequate power to explain. Therefore calls for greater registration of patients in trials and databases are well founded. Such registries can help surgeons use better data. Both EUROCAT (http://www.eurocat-network. eu/accessprevalencedata/prevalencetables) and the International Clearing House for Birth Defects (http://www.icbdsr.org) are good starting resources for surgeons wishing to know more about this topic (Pedersen et al. 2012). Books like this provide useful pointers as do colleagues in clinical genetics who, despite their name, will often catalogue unusual anomalies without obvious cause. Applied scientists can also be a useful resource – because complex systems are frequent in engineering and safety (Davidz and Nightingale 2008; Park and Park 2004). Their insights can help surgeons to move beyond linear models

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reliant on the central dogma of molecular biology. Not only is DNA insufficient to explain all birth defects, but the information that it carries is dwarfed by that carried, e.g., in posttranslational modifications like glycosylation (Turnbull and Field 2007). This point – perhaps nonobvious at first – is that glycosylation and other posttranslational processing vastly diversify the tertiary structures determined strictly by the genome. This reinforces how genomic information may be fundamentally insufficient to explain birth defects: e.g., intrauterine influences from the environment could instead be transduced via altered posttranslational protein modifications (Thompson et al. 2007, 2009, 2010, 2011). Therefore, pediatric surgeons need access to wide expertise to best advise families with birth defects – at times of great need, misunderstanding and fear. A humbling uncertainty surrounds much of what is taught and told academically about such defects. Frank sharing of this can help the parents understand that they are not alone in their struggle to understand their new reality. For the time being, surgeons have to begin with the data currently available. The tables included here show the commonest birth defects by organ system (Table 1) and then list those that are likely to present to pediatric surgeons (Table 2). The data is drawn from the EUROCAT databases and is therefore subject to the important caveats listed on their website.

Conclusion and Future Directions It has been argued here that birth defects are best interrogated with a systems approach rather than via molecular biology. A similar shift away from linear drug-receptor paradigms in noncommunicable adult diseases may alleviate the current stagnation within the blockbuster drug pipeline (DiMasi et al. 2004). Computing is more powerful than ever and data storage becoming relatively cheap (Stein 2010). Therefore tantalizing possibilities exist to use bigger data to delve into birth defects epidemiology. For example, scientists have been able to use social media like Facebook and Twitter to

43 Table 1 Birth prevalence of malformations 2007–2011 grouped by EUROCAT category. Note rates for each category are inclusive of cases with chromosomal lesions and derived from registries with EUROCAT membership

Organ system All Congenital heart disease Limb Chromosomal Urinary Nervous system Genital Digestive system Orofacial clefts Other malformations Respiratory Abdominal wall defects Genetic syndromes + microdeletions Eye Ear, face, neck Teratogenic syndromes with malformations

Live birth + fetal death + termination/10,000 births (to 2 s.f.) 210 65 35 29 27 20 19 14 13 10 5.4 5.3 3.8 3.5 2.8 1.0

track the impacts of adverse weather, earthquakes, or even impeding flu epidemics (Hattori and Ieee 2012). Store purchases may also give an early hint of such events. Given what store chains can divine about individual lifestyles, it remains to be seen whether their techniques, such as collaborative filtering, can be used to identify obscure risk factors for birth defects (Cho et al. 2002). Certainly, the present generation of children are perhaps the first in which a store card records most purchases to which they have ever been exposed. At present, this seems like an area ripe for exploration. Another advance that one may see is the introduction of near patient interfaces that allow the parent to enter more of their information and that of their child in cases of birth defects. Shifting data ownership may be an effective way to increase participation, particularly when resources for dedicated data gatherers are scarce. The question then arises whether nations, rich and poor, are building healthcare teams equipped

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Table 2 Birth prevalence of malformations of relevance to pediatric surgery (2007–2011) grouped by diagnosis from registries with EUROCAT membership. Note rates for each category are inclusive of cases with chromosomal lesions; (b) these are birth prevalences (including fetal death/terminations) and not necessarily the prevalences at pediatric surgical units

Anomaly Downs Hypospadias Congenital hydronephrosis Spina bifida Edward’s Anorectal malformations Diaphragmatic hernia Exomphalos Gastroschisis OA/TOF Duodenal atresia/ stenosis Bilateral renal agenesis Hirschsprung disease Intestinal atresia/ stenosis CCAM Posterior urethral valves/prune belly Indeterminate sex Bladder exstrophy/ epispadias Situs inversus Amniotic band Biliary atresia Conjoined twins

Live birth + fetal death + termination/10,000 births (to 2 s.f.) 18 14 7.8 4.3 3.9 2.7 2.3 2.5 2.4 2.2 1.1 0.90 0.90 0.70 0.70 0.68 0.59 0.55 0.55 0.41 0.21 0.14

to do such work. Medicine is still taught around the great empires of biomedicine. To help the shift from biological reductionism, these new challenges will require a reintroduction of engineering know-how into medicine: to improve quantitative modelling, to manipulate complex systems, and to program computers to explore these data-rich opportunities (Putnam 2006). Looking at wider policy, birth registries are too important to neglect. Births show demographers how the world’s population will look in the

future. By this standard, birth defects monitoring provides an early warning system for humanity as a whole. Therefore, if climate change exerts subtle effects, it may be that these will be detected first in the birth prevalences of key defects (Rylander et al. 2011; Van Zutphen et al. 2012; Auger et al. 2017). Similarly, increased use of genetically modified crops seems likely to fuel public demand for good data on birth defects – to ensure that risk to humans is minimal (Islam and Miah 2006). Finally, areas of Iraq exposed to depleted uranium shells report increased birth defect rates (Hindin et al. 2005; Marshall 2008; Busby et al. 2010). Disturbingly, the World Health Organization is alleged to have been complicit in efforts to suppress this “bad news” (Ahmed 2013). Birth defects epidemiology is often difficult in peacetime, so it is understandable there would be controversy about conflict-related birth defects. However, healthcare professionals have a responsibility to speak truth to power even on these uncomfortable matters. Otherwise, Katz highlights how technical language, and rhetoric can be used all too expediently to ignore the true depth of even major problems (Katz 1992).

Cross-References ▶ Clinical Research and Evidence-Based Pediatric Surgery ▶ Embryology of Congenital Malformations ▶ Fetal Counseling for Congenital Malformations ▶ Fetal Surgery ▶ Long-Term Outcomes in Newborn Surgery ▶ Pediatric Clinical Genetics

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46 Horton R. Surgical research or comic opera: questions, but few answers. Lancet. 1996;347:984–5. Horton R. What is the point of surgery? Lancet. 2010;376 (9746):1025. Islam AS, Miah SA. Transgenic plants: risks, concerns and effects on ecosystem and human health. Plant Tissue Cult Biotechnol. 2006;16(2):139–64. Jesudason EC. Challenging embryological theories on congenital diaphragmatic hernia: future therapeutic implications for paediatric surgery. Ann R Coll Surg Engl. 2002;84:252–9. Jesudason EC, Connell MG, Fernig DG, Lloyd DA, Losty PD. Early lung malformations in congenital diaphragmatic hernia. J Pediatr Surg. 2000;35:124–7; discussion 128. Katz SB. The ethic of expediency – classical rhetoric, technology, and the Holocaust. Coll Engl. 1992;54:255–75. Keijzer R, Liu J, Deimling J, Tibboel D, Post M. Dual-hit hypothesis explains pulmonary hypoplasia in the nitrofen model of congenital diaphragmatic hernia. Am J Pathol. 2000;156:1299–306. Khoury MJ. Epidemiology of birth defects. Epidemiol Rev. 1989;11:244–8. Kilby MD. The incidence of gastroschisis – is increasing in the UK, particularly among babies of young mothers. Br Med J. 2006;332:250–1. Lippman A. Led (Astray) by genetic maps – the cartography of the human genome and health-care. Soc Sci Med. 1992;35:1469–76. Lumley J. Defining the problem: the epidemiology of preterm birth. Bjog Int J Obstet Gynaecol. 2003;110:3–7. Marshall AC. Gulf war depleted uranium risks. J Expo Sci Environ Epidemiol. 2008;18:95–108. McCulloch P, Catchpole K. A three-dimensional model of error and safety in surgical health care microsystems. Rationale, development and initial testing. BMC Surg. 2011;11:23. Monif GRG, Avery GB, Korones SB, Sever JL. Postmortem isolation of Rubella virus from 3 children with Rubella-syndrome defects. Lancet. 1965;1 (7388):723–4. Mortell A, Montedonico S, Puri P. Animal models in pediatric surgery. Pediatr Surg Int. 2006;22:111–28. National Confidential Enquiry into Patient Outcome and Death (NCEPOD). Surgery in children: are we there yet? 2011. http://www.ncepod.org.uk/2011sic.html Nelson CM, Gleghorn JP. Sculpting organs: mechanical regulation of tissue development. Annu Rev Biomed Eng. 2012;14(14):129–54. Nelson SM, Hajivassiliou CA, Haddock G, Cameron AD, Robertson L, et al. Rescue of the hypoplastic lung by prenatal cyclical strain. Am J Respir Crit Care Med. 2005;171:1395–402. Nichol PF, Reeder A, Botham R. Humans, mice, and mechanisms of intestinal atresias: a window into understanding early intestinal development. J Gastrointest Surg. 2011;15:694–700.

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Prenatal Diagnosis of Congenital Malformations Tippi C. MacKenzie and N. Scott Adzick

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Ultrasound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 MRI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Amniocentesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Chorionic Villus Sampling (CVS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Biochemical Markers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Percutaneous Umbilical Blood Sampling (PUBS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Fetal Cells in the Maternal Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Prenatal Diagnosis of Specific Surgical Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Neck Masses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Sacrococcygeal Teratoma (SCT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Congenital Chest Lesions: Congenital Pulmonary Adenomatoid Malformation and Bronchopulmonary Sequestration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Congenital Diaphragmatic Hernia (CDH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Gastrointestinal Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Esophageal and Bowel Atresias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abdominal Wall Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prenatal Diagnosis of Renal Anomalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Upper Urinary Tract Obstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lower Urinary Tract Obstruction (LUTO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

58 58 58 59 60 60

T. C. MacKenzie (*) Eli and Edythe Broad Center for Regeneration Medicine, Fetal Treatment Center, University of California, San Francisco, CA, USA e-mail: [email protected] N. Scott Adzick The Division of Pediatric General and Thoracic Surgery, The Center for Fetal Diagnosis and Treatment, Children’s Hospital of Philadelphia, Philadelphia, PA, USA e-mail: [email protected] # Springer-Verlag GmbH Germany, part of Springer Nature 2020 P. Puri (ed.), Pediatric Surgery, https://doi.org/10.1007/978-3-662-43588-5_3

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T. C. MacKenzie and N. Scott Adzick Myelomeningocele . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Conclusion and Future Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Cross-References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Abstract

The convergence of progress in genetic and radiographic methods for prenatal diagnosis now makes it possible to diagnose most congenital anomalies early in gestation. Thus, it is now possible to accurately counsel affected families about their prognosis and to plan for appropriate perinatal care using a multidisciplinary team approach. In rare cases of severe or fatal anatomic abnormalities, fetal intervention may be offered by experienced centers. In this chapter, we discuss common prenatal diagnostic tools as well as the management strategies for patients with surgical diseases such as neck masses, congenital diaphragmatic hernias (CDH), lung masses, sacrococcygeal teratomas (SCTs), and myelomeningocele. There are strategies that have been developed through decades of experience with animal models and collaborative analysis of clinical outcomes worldwide. Our understanding of the underlying disease processes that contribute to prognosis is rapidly evolving and will continue to refine the current recommendations for these patients.

mode of delivery and, in some cases, may lead to elective termination of the pregnancy. In rare cases, various forms of in utero therapy may be possible (Table 1). Multidisciplinary care and nondirective counseling are the crux of appropriate prenatal management of most congenital anomalies. The perinatal care of the patients involves many different medical disciplines, including obstetricians, sonographers, neonatologists, geneticists, pediatric surgeons, and pediatricians. It is essential that the affected family be treated using a team approach and that information and experience be exchanged freely. Prenatal diagnosis has defined a “hidden mortality” for some lesions such as congenital diaphragmatic hernia (CDH), bilateral hydronephrosis, sacrococcygeal teratoma (SCT), and cystic hygroma. These lesions, when first Table 1 Diseases amenable to fetal surgical intervention in selected cases

Keywords

Malformation Congenital diaphragmatic hernia

Prenatal diagnosis · Fetal surgery · Congenital anomalies

CPAM or BPS

Introduction Advances in prenatal diagnosis now allow accurate identification of many congenital anatomic defects so that affected families may be counseled appropriately. For most congenital malformations diagnosed in utero, planned delivery at term can allow appropriate medical and surgical therapy after birth. The benefit of prenatal diagnosis is that the process can influence the timing or the

Sacrococcygeal teratoma

Effect on development Pulmonary hypoplasia, respiratory failure Pulmonary hypoplasia, hydrops

In utero treatment Tracheal occlusion and release Maternal steroids, thoracoamniotic shunting, lobectomy Excision

Massive arteriovenous shunting, placentamegaly, hydrops Urethral Hydronephrosis, Vesicoamniotic obstruction lung hypoplasia shunting, laser ablation of PUV Myelomeningocele Damage to the Closure of defect spinal cord, paralysis

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evaluated and treated postnatally, demonstrate a favorable selection bias. The most severely affected fetuses often die in utero or immediately after birth, before an accurate diagnosis has been made. Consequently, such a condition detected prenatally may have a worse prognosis than the same condition diagnosed after delivery. In this chapter, we will present a brief summary of commonly used diagnostic methods and then review the prenatal diagnosis of several pediatric surgical diseases.

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nervous system, the ability to obtain crosssectional imaging has made this tool a crucial adjunct to ultrasound for many pediatric surgical diseases, including measurement of lung sizes in CDH and evaluation of airway anatomy in neck masses. Although the modality is sometimes limited by patient comfort at later gestational ages, improvements in scanning techniques continue to bring MRI to the forefront of prenatal diagnosis.

Amniocentesis Ultrasound It is now routine to perform a prenatal evaluation of fetal anatomy by ultrasound for almost all pregnancies. It is especially important to perform ultrasound screening for pregnancies with maternal risk factors (e.g., age over 35 years, diabetes, previous child with anatomic or chromosomal abnormality) and if there is an elevation in maternal serum alpha-fetoprotein (MSAFP). Most defects can be reliably diagnosed in the late first or early second trimester by a skilled sonographer. Early in gestation, nuchal translucency measurements can often detect chromosomal abnormalities. Since these measurements can be made by transvaginal ultrasound at 10–15 weeks’ gestation, ultrasound can be a critical early test for high-risk pregnancies. Nuchal cord thickening may also be a marker for congenital heart disease and may be a valuable initial screen to detect high-risk fetuses for referral for fetal echocardiography. It is important to remember that sonography is operator-dependent; the scope and reliability of the information obtained is directly proportional to the skill and experience of the sonographer.

Amniocentesis has become the gold standard for detecting fetal chromosomal abnormalities. Amniocentesis is usually performed at 15–16 weeks’ gestation and involves a very low risk of fetal injury or loss. However, amniocentesis earlier in gestation (11–12 weeks) can entail a higher rate of pregnancy loss, increased risk of iatrogenic fetal deformities, and increased postamniocentesis leakage rate. For this reason, the most reliable method for first trimester diagnosis remains chorionic villus sampling. In addition to screening for the most common chromosomal abnormalities using karyotyping, modern sequence analysis and microarrays have revolutionized our ability to detect small deletions or duplications that are not apparent with karyotyping. A recent study comparing the efficacy of karyotyping to microarray determined that the latter is more sensitive in identifying small deletions and duplications in 6% of samples with a normal karyotype but less sensitive in identifying balanced translocations or fetal triploidy (Wapner et al. 2012). Given the expense of microarray analysis and the realization that it sometimes reveals copy number variations of uncertain clinical significance, it is currently reserved for patients in whom there is a high pretest suspicion for genetic abnormalities.

MRI Fetal MRI has greatly enhanced our ability to diagnose and treat fetal malformations. The use of ultrafast scanning techniques has eliminated the artifacts caused by fetal motion. While MRI is most commonly used to evaluate the fetal central

Chorionic Villus Sampling (CVS) CVS involves sampling the chorion frondosum, the precursor for the placenta, using either a transcervical or transabdominal approach under

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ultrasound guidance. Since CVS may be performed at 10–14 weeks’ gestation, it can be a useful test for patients with advanced maternal age and other risk factors for chromosomal anomalies. Similar to amniocentesis, the cells obtained may be subjected to a variety of tests including karyotype, microarray analysis, and enzymatic activity. However, CVS can lead to diagnostic errors due to maternal decidual contamination or genetic mosaicism of the trophoblastic layer of the placenta. When performed by experienced operators, the pregnancy loss rate is equivalent to second trimester amniocentesis.

Biochemical Markers Fetal anomalies such as Down’s syndrome and neural tube defects are associated with elevations of particular enzymes in maternal blood, which forms the basis for biochemical screening. One of the most common prenatal diagnostic tests is the so-called triple test, which includes measuring serum alpha-fetoprotein with human chorionic gonadotropin and unconjugated estriol. This screening is performed in the early second trimester, and the detection rate for Down’s is 69%, with a 5% false-positive test (Wald et al. 1997). A positive result on the serum screening test indicates a need for chromosome analysis by amniocentesis.

T. C. MacKenzie and N. Scott Adzick

Fetal Cells in the Maternal Circulation Maternal-fetal cellular trafficking is the bidirectional passage of cells between the fetus and the mother during gestation, which has clinical implications for multiple diseases. Since fetal cells cross into maternal blood, the detection of fetal cells and cell-free DNA in the maternal circulation could form the basis for a noninvasive method of prenatal genetic diagnosis. While the number of intact cells in the circulation is limited, amplification of fetal cell-free nucleic acids using real-time polymerase chain reaction (PCR) has growing utility in early prenatal diagnosis (Maron and Bianchi 2007). Fetal DNA can be detected reliably by 9 weeks and increases with gestational age. This method can be used for gender determination in the first trimester (if Y chromosome sequences are found, the fetus is male and, if not, assumed to be female) and can thus be helpful in counseling for X-linked disorders. Rhesus factor determinations are also accurate and can avoid unnecessary treatment of Rh-negative mother if the fetus is also negative. In the future, it may be expanded to detecting paternally inherited single gene mutations. Non-invasive prenatal testing is becoming the routine screening test for prenatal diagnosis of aneuploides.

Prenatal Diagnosis of Specific Surgical Lesions Neck Masses

Percutaneous Umbilical Blood Sampling (PUBS) Although more invasive, obtaining fetal blood directly from the umbilical cord allows the ability to diagnose various metabolic and hematological disorders. For diseases such as Rh disease, the technique can also allow transfusion of the fetus. The procedure is performed at around 18 weeks’ gestation under ultrasound guidance. In various large series, the mortality from the procedure has been reported to be 1–2%, with increasing mortality with long procedure times and multiple punctures.

Prenatal diagnosis and appropriate management can be lifesaving for fetuses with airway obstruction. The fetal airway can be compromised either due to extrinsic compression from a solid tumor such as a cervical teratoma or due to intrinsic defects in the airway such as congenital high airway obstruction syndrome (CHAOS). Although large congenital neck masses causing airway obstruction previously carried an enormous perinatal mortality, the advent of the ex utero intrapartum treatment (EXIT) procedure (Mychaliska et al. 1997) has improved their outcome by providing a means of controlling the

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airway during delivery and converting an airway emergency into an elective procedure. Cystic hygroma is a severe diffuse lymphatic malformation which is frequently associated with hydrops, polyhydramnios, and other abnormalities. Chromosomal abnormalities are very common. There are two groups of prenatally diagnosed cervical lymphangiomas: those diagnosed in the second trimester are usually in the posterior triangle of the neck, have a high incidence of associated abnormalities, and carry a very poor prognosis (Gallagher et al. 1999). Those diagnosed later in gestation are most often isolated lesions and generally do not lead to hydrops. Hydrops is an ominous finding in fetuses with cystic hygroma, and it is important to monitor the fetus for development of hydrops by serial evaluations. Cervical teratomas are asymmetrical lesions that are frequently unilateral, with well-defined margins. They may also be multiloculated, irregular masses with solid and cystic components. Most teratomas contain calcifications. Fetal MRI is a very useful adjunct to ultrasound in evaluating giant neck masses in defining the position of the airway with respect to the mass and the presence of tracheal deviation and esophageal compression. T1-weighted images may help differentiate teratomas from lymphangiomas. Careful mapping of the airway allows adequate preparation for the various strategies to secure the airway during the EXIT procedure. The EXIT procedure, originally designed for removal of tracheal clips in patients with CDH (Mychaliska et al. 1997), has proven lifesaving for many fetuses with giant neck masses or large oral lesions. This procedure involves performing a maternal hysterotomy and obtaining control of the fetal airway while the fetus remains on placental support. In order to prevent uterine contractions during the procedure, the mother is given inhalational anesthetic and tocolytics, warm saline is infused through a level I device, and only head and shoulders of the fetus are delivered. After attaching a pulse oximeter to the fetal hand to monitor heart rate and oxygen saturation, direct laryngoscopy and, if possible, endotracheal

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Fig. 1 EXIT procedure for giant neck mass (Adapted from Mackenzie and Adzick 2011, reprinted with permission)

intubation are performed (Fig. 1). If the airway cannot be secured in this way, a rigid bronchoscope is inserted to determine the anatomy. If necessary, a tracheostomy can be performed. After securing the airway, surfactant is administered for premature fetuses, the cord is clamped, and the infant is taken to an adjacent operating room for resuscitation. In a recent review of 87 EXIT procedures, we found that the EXIT procedure is a safe mode of delivery for patients with giant neck masses and potential airway obstruction at birth. We had a 100% success rate in accessing the airway under placental support, and the procedure-related mortality rate was zero. The success of an EXIT procedure depends on a thorough evaluation of the prenatal images for surgical planning and a highly skilled multidisciplinary team approach (Laje et al. 2012). The EXIT procedure has also been useful in the perinatal resuscitation of fetuses with a range of anomalies expected to cause hemodynamic compromise at birth, such as giant lung masses (EXIT to resection), CHAOS, severe congenital heart disease with CDH (EXIT to extracorporeal membrane oxygenation, ECMO), and even thoracopagus conjoined twins with a single heart. The most critical component of the EXIT

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procedure is deep inhalational anesthesia, which maximizes uteroplacental blood flow to avoid fetal hypoxia. It is therefore critically different from a Cesarean section and carries the risk of significant maternal blood loss if there is not careful coordination between the surgical and anesthetic teams.

Sacrococcygeal Teratoma (SCT) Sacrococcygeal teratoma is the most common newborn tumor and may arise due to misdirected migration of primordial germ cells during development. The Altman classification defines four types with differing prognoses: type 1 tumors are external, with at most a small presacral component and carry the best prognosis. Type 2 tumors are predominantly external with a large intrapelvic portion. Type 3 lesions are predominantly intrapelvic with abdominal extension with only a minor external component and type 4 lesions are entirely intrapelvic and abdominal. The latter have the worst prognosis since they are difficult to diagnose, sometimes less amenable to surgical resection, and frequently malignant at the time of diagnosis because of the delay in diagnosis. Overall, prenatally diagnosed SCT has a worse prognosis than those diagnosed at time of birth. On prenatal ultrasound, SCT appears as a mixed solid and cystic lesion arising from the sacrum. The tumor frequently contains calcifications. Since there is acoustic shadowing by the fetal pelvic bones, it is not always possible to determine the most cephalad portion of the tumor by ultrasound. Fetal MRI (Fig. 2) may determine the intrapelvic dimensions of the tumor as well as the presence of hemorrhage. Those fetuses with mainly solid and highly vascular SCT have a higher risk of developing hydrops. High-output cardiac failure may occur as a result of the hemodynamic effects of the large blood flow to the tumor, and anemia from hemorrhage into the tumor may compound this problem. In severe cases, the mother with placentamegaly develops “mirror syndrome,” a severe preeclamptic state with vomiting, hypertension, proteinuria, and edema. This phenomenon may be mediated

Fig. 2 MRI of large sacrococcygeal teratoma (Adapted from Mackenzie and Adzick 2011, reprinted with permission)

by the release of vasoactive compounds from the edematous placenta. As with other fetal masses, the development of hydrops is a grave sign. The prediction of which fetuses with SCT are at highest risk for developing hydrops is the critical issue in prenatal management. A thorough prenatal evaluation with US, MRI, and fetal echocardiography is important in defining such a group. Factors such as rapid tumor growth and large solid component have been associated with a higher risk of developing hydrops. Since hydrops is likely an indicator of hemodynamic compromise, echocardiographic measurements are superior to anatomic ones in defining the worst cases. For example, in a recent evaluation of numerous echocardiographic measurements in fetuses with SCT and twin reversed arterial perfusion syndrome (TRAP), measurements indicating high output were correlated with worse outcome (Byrne et al. 2011). These include a high cardiothoracic ratio, combined cardiac output (CCO) >550 ml/kg/min, aortic valve regurgitation, and aortic or mitral Z score >2. In another series (Wilson et al. 2009), rapid tumor growth (>150 cm3/week) and a high CCO identified a group of fetuses with a higher risk of prenatal

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mortality. The solid component of the mass is an important prognostic indicator: a recent report showed that when the solid tumor volume is normalized to the head volume, fetuses with a ratio 1 have 61% mortality (Sy et al. 2009). Recently the Cincinnati Fetal Center reported that the overall survival rate to discharge was 25% in patients with hydropsfetalis, 67% in patients with high cardiac output status in utero, and 100% in patients with normal fetal cardiac output (Peiro et al. 2016). Prenatal interventions for SCT include cyst aspiration (for those with a dominant cystic component), amnioreduction (for those with severe, symptomatic polyhydramnios), amnioinfusion (for those with bladder outlet obstruction, to facilitate placement of a vesicoamniotic shunt), or open fetal surgery for resection of the mass. The latter option should only be considered for fetuses with impending high-output failure, rapid growth, type I lesion amenable to resection, and gestational age between 20 and 32 weeks. For fetuses older than 32 weeks and impending hydrops, emergent delivery with postnatal resection should be considered. Fetal resection of SCT has led to some survivors, but remains plagued by a high perinatal mortality, likely because a fetus that is already moribund secondary to hydrops does not tolerate the operation. It is important to note that the purpose of fetal resection is debulking, and a complete oncologic resection is usually performed postnatally. Given a high rate of preterm labor after open fetal surgical resection, some groups have attempted minimally invasive treatments such as radiofrequency ablation (RFA), but the difficulty in controlling heat from the RFA device precludes widespread use of this approach.

Congenital Chest Lesions: Congenital Pulmonary Adenomatoid Malformation and Bronchopulmonary Sequestration Congenital pulmonary adenomatoid malformation (CPAM) represents a spectrum of diseases characterized by cystic lesions of the lung which

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can be microcystic, macrocytic, or both. Prenatal ultrasound can generally distinguish individual cysts in macrocystic disease, while microcystic lesions usually have the appearance of an echogenic, solid lung mass. Bronchopulmonary sequestration (BPS) is an aberrant lung mass that is nonfunctional and usually has a systemic blood supply. It may be difficult to distinguish microcystic CPAM from BPS on ultrasound. Indeed, there is growing evidence that the two lesions may be related embryologically, with several reported cases of hybrid lesions which have CPAM-like architecture and a systemic blood supply. Some of these lesions may decrease in size during prenatal period, but postnatal evaluation is still warranted to detect residual disease for resection because of the risk of pulmonary infections and the development of tumors such as pleuropulmonary blastoma. The critical information needed for accurate prenatal diagnosis and counseling is the size of the lesion, the presence of large cysts that may be amenable for drainage for large lesions, the presence of hydrops, and the presence of a systemic feeding vessel. A combined approach with US and MRI can answer these questions. MRI is useful in delineating the normal lung from abnormal and in distinguishing BPS from the surrounding lung due to its high signal intensity and homogeneous appearance. However, ultrasound is more accurate in demonstrating systemic feeding vessels. Fetuses with large chest masses can develop hydrops, which is the primary prognostic factor for survival. While the exact cause of hydrops in these patients is not known, is it believed to be secondary to obstruction of the vena cava or cardiac compression from extreme mediastinal shift. Historically, the development of hydrops has indicated a grave prognosis with 100% mortality, and it is important to predict which fetuses are at high risk for this complication. The volume of the CPAM compared to the head circumference (CPAM volume ratio, CVR) is an important prognostic indicator: fetuses with a CVR greater than 1.6 are more likely to develop hydrops (Crombleholme et al. 2002). It is also important to recognize that there is an expected period of growth during the second trimester, after which

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Fig. 3 Ultrasound image of large CCAM following the placement of a thoracoamniotic shunt. L lung (Adapted from Mackenzie and Adzick 2011, reprinted with permission

the mass usually gets smaller with respect to the fetus. Therefore, CVR should be measured at multiple consecutive visits. Fetuses with BPS can also develop pleural effusions. For fetuses with a large macrocystic CPAM containing a dominant cyst, or a large pleural effusion causing pulmonary hypoplasia, thoracoamniotic shunting (Fig. 3) may be lifesaving: in one series of 19 high-risk fetuses who underwent prenatal shunt placement (Wilson et al. 2004), survival was 67% (6/9) in the pleural effusion group and 70% (7/10) for the CPAM group, with an average age of delivery at 33+ weeks. Fetuses with large microcystic CPAMs (thus not amenable for shunting) and signs of hydrops require a different approach. Although open fetal surgery was initially performed, the recognition that maternal administration of steroids can reverse hydrops has been an exciting new development in the antenatal management of this disease. Multiple centers have reported on the experience with maternal steroids in large CPAM with CVR >1.6 and impending hydrops (Curran et al. 2010; Morris et al. 2009; Peranteau et al. 2007). Overall, there are 31 reported patients with microcystic CPAM with CVR >1.6 and/or hydrops who were treated with steroids (reviewed in Curran et al. 2010), with resolution of hydrops in 80% and survival to discharge in 87%. If hydrops does not resolve, a second course of

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steroids may be offered. In addition, the strategy is only effective for microcystic CPAMs and is less likely to be effective for macrocystic or mixed lesions (Morris et al. 2009). The mechanism by which steroids reverse hydrops remains unknown: their beneficial effects cannot simply be ascribed to reductions in the size or rate of growth of the CPAM as there was variable growth in these patients, and a natural growth plateau is welldescribed. Further studies into the basic biology of CPAM to understand how steroids may influence alveolar maturation or hydrops are areas of active research interests in many laboratories.

Congenital Diaphragmatic Hernia (CDH) The prenatal diagnosis and management of CDH continues to evolve. This disease is usually diagnosed on a screening ultrasound evaluation, which can show herniated abdominal viscera, abnormal upper abdominal anatomy, mediastinal shift away from the side of herniation, and, in severe cases, polyhydramnios. The presence of abdominal contents seen in the chest on a transverse sonographic scan at the level of a fourchamber view of the heart is required for diagnosis. The extent of pulmonary hypoplasia, which is a major contributor to postnatal morbidity, is proportional to the timing of herniation, the size of the diaphragmatic defect, and the amount of viscera herniated. Right-sided CDH is less common than on the left but is a more severe disease with a particularly high rate of prenatal complications such as polyhydramnios, premature rupture of membranes, and preterm labor (Hedrick et al. 2004). The best predictor of outcome in CDH has been the right lung-to-head circumference ratio (LHR), defined as right lung area (measured at the level of the transverse four-chamber cardiac view) divided by head circumference (Fig. 4). The utility of LHR in predicting survival has been validated in a recent multicenter trial (Jani et al. 2006), with LHR 95% with associated anomalies, low birth weight, and prematurity contributing to the 15 mm in length and > 17 mm in diameter) on prenatal ultrasound scan is indicative of bowel obstruction.

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Fig. 8 Prenatal and postnatal imaging of intestinal atresia

much less sensitive in diagnosing large bowel anomalies than those with small bowel anomalies (Patel et al. 2004). Since the large bowel is mostly a reservoir, with no physiologic function in utero, defects in this region such as anorectal malformations or Hirschsprung’s disease are very difficult to detect. Bowel dilatation and echogenic bowel may be associated cystic fibrosis; therefore, all such fetuses should undergo postnatal evaluation for this disease (Al-Kouatly et al. 2001). Prenatally diagnosed small bowel atresia does not select for a group with a worse prognosis, and survival rates are 95–100%.

diagnoses include extralobar pulmonary sequestration and pancreatic, splenic, urachal, and adrenal cysts. Almost all cysts are benign and many are self-limiting; however, these cysts create a high level of anxiety for the prospective parents, especially suspected adrenal cyst. Regular antenatal consultation and fetal counseling by the appropriate team may reduce parental anxiety levels. There is a very small role for fetal intervention. Resolution of these cysts was reported in 25% of cases, and 30% came to surgical intervention (Sherwood et al. 2008). Postnatal imaging is essential.

Abdominal Cysts

Sacrococcygeal Teratomas

Abdominal cystic lesions are not uncommonly diagnosed at antenatal ultrasound (US) examination (Fig. 9). A cystic mass identified in this way may represent a normal structural variant or a pathological entity requiring surgical intervention postnatally. Despite increasingly sophisticated equipment, some congenital anomalies have significant false-positive rates on US, and fetal cystic abdominal masses in particular can be difficult to diagnose accurately (Sherwood et al. 2008). Excluding cysts of renal origin, the differential diagnosis includes ovarian cysts, enteric duplication cysts, meconium pseudocyst, mesenteric cysts, and choledochal cysts. Less common

Sacrococcygeal teratoma (SCT) is the commonest neonatal tumor accounting for 1 in 35,000 to 40,000 births (Fig. 10; Pauniaho et al. 2013). Four types have been defined, namely (Altman et al. 1974), type 1 external tumor with a small presacral component, type 2 external tumors with a large presacral component, type 3 predominantly presacral with a small external component, and type 4 entirely presacral. Type 4 carries the worst prognosis (Koivusalo et al. 2005) due to delay in diagnosis and malignant presentation. Doppler ultrasound is the diagnostic tool; however, fetal MRI provides better definition of the intrapelvic component. SCT is a highly vascular tumor, and

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Fig. 9 (a) Prenatal abdominal cyst; (b) prenatal ovarian cyst

Fig. 10 Prenatal MRI and postnatal image of sacrococcygeal teratoma

the fetus may develop high cardiac output failure, anemia, and ultimately hydrops with a mortality of almost 100%. Fetal treatment of tumor resection or ablation of feeding vessel has been attempted in hydropic patients with minimal success. Caesarean section may be offered to patients with large tumors to avoid the risk of bleeding during delivery. Postnatal outcomes following surgery in type 1 and 2 lesions are favorable; however, type 3 and 4 tumors may present with urological and bowel problems with less favorable outcomes (Tailor et al. 2009). Long-term follow-up with alpha-fetoprotein and serial pelvic

ultrasounds is mandatory to exclude recurrence of the disease (Usui et al. 2012).

Renal Anomalies Urogenital abnormalities are among the commonest disorders seen in the perinatal period and account for almost 20% of all prenatally diagnosed anomalies (Brand et al. 1994). Many structural anomalies of the kidney and urinary tract can be detected by antenatal ultrasound, allowing early diagnosis and opportunity

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to counsel parents and plan further investigations and management (Marokakis et al. 2016). The routine use of antenatal ultrasound scans has resulted not only in the early detection of these conditions but in selected cases has led to the development of management strategies, including fetal intervention aimed at preservation of renal function. Two major issues are the indications for intervention in bladder outlet obstruction and early pyeloplasty in infancy in cases with hydronephrosis (Chevalier 2004). Prenatal evaluation of a dilated urinary tract is based on serial ultrasound scans as well as measurement of urinary electrolytes. Ultrasonography provides measurements of the renal pelvis, assessment of the renal parenchyma, as well as the detection of cysts in the cortex. In severe disease, lack of amniotic fluid may make ultrasound assessment of the renal tract difficult, and MRI may be helpful. Oligohydramnios is indicative of poor renal function and poor prognosis owing to the associated pulmonary hypoplasia. Urogenital anomalies coexist with many other congenital abnormalities, and amniocentesis should be offered in appropriate cases. It is estimated that 3% of infants will have an abnormality of the urogenital system, and half of these will require some form of surgical intervention (Steinhart et al. 1988).

Upper Urinary Tract Obstruction Antenatal hydronephrosis accounts for 0.6–0.65% pregnancies (Davenport et al. 2013). The most common cause of prenatal hydronephrosis is pelvi-ureteric junction (PUJ) obstruction, others being transient hydronephrosis, physiological hydronephrosis, multicystic kidney, posterior urethral valves, ureterocele, ectopic ureter, etc. The prognosis is excellent in antenatally diagnosed unilateral hydronephrosis and in renal pelvic diameter of 1.6 at the time of steroid administration. This compares to a mortality of 100% in fetuses with hydrops and a 56% mortality in fetuses with a CVR >1.6 among historical controls. In contrast to microcystic CPAMs, macrocystic CPAMs do not consistently respond to steroid treatment and should be treated by thoracoamniotic shunting if hydrops are evolving. A current algorithm for management of fetuses with CPAM is shown in Fig. 3. When maternal-fetal surgery is required, the arm and hand on the affected side are exposed, and the fetus is rotated to expose the chest wall, leaving the head and remainder of the body within the amniotic sac. Once intravenous access is obtained and a pulse oximeter is attached, the fetus is treated with atropine and volume loaded to counter reflexive bradycardia and cardiovascular collapse, which are often seen with acute decompression of the chest when the tumor is exposed. Electrocautery is used to create a large posterolateral thoracotomy at the sixth intercostal space. The lobe containing the CPAM is exteriorized (Fig. 4a). The attachments to surrounding lung tissue are divided, and the lobar pulmonary artery is ligated prior to ligation of the vein and bronchus in order to avoid lobar congestion. The bronchus is ligated next, followed by the pulmonary vein (Fig. 4b). The thoracotomy is then closed followed by uterine closure as described

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Detailed Sonography Ultrafast MRI Fetal Echocardiogram (Amniocentesis)

Associated Anomalies

Isolated CPAM without fetal hydrops Low Risk CVR < 1.6 Follow up with Serial US

Isolated CPAM

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EXIT-to-CPAM resection

Delivery at tertiary center - Neonatal Resection

Delivery at term Elective resection

Fig. 3 Algorithm for management of congenital pulmonary airway malformation (CPAM)

Fig. 4 (a) Resection of a fetal CCAM. The picture illustrates the fetal position with the arm and chest wall exposed, with the head inside the uterus. Continuous echocardiographic monitoring is performed during the procedure. In this image, a thoracotomy has been performed, and

the tumor can be seen bulging from the incision. (b) A hilar dissection has been performed, and the pulmonary artery and bronchus have been divided. The pulmonary vein is being ligated prior to removal of the tumor

above. Delivery following maternal-fetal surgery should be planned as late as possible to avoid complications associated with prematurity.

Outcomes Open fetal surgical resections for microcystic CCAM are associated with 60% survival with

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most patients enjoying a good quality of life. Thoracoamniotic shunt placements for macrocystic CCAM have been reported to decrease CCAM mass volumes by an average of 50% and up to 80% and are associated with approximately 75% survival.

Congenital Diaphragmatic Hernia Congenital diaphragmatic hernia (CDH) is a developmental defect in the diaphragm, which leads to herniation of abdominal viscera into the chest. CDH affects 1 in 3000 live births and is most often sporadic, although familial cases have been reported. CDH is often syndromic; 25–57% of live born cases and 95% of stillborn fetal cases occur with associated abnormalities. These associated anomalies include hydronephrosis, congenital heart defects, renal agenesis, extralobar sequestrations, and neurologic defects including hydrocephalus, spina bifida, and anencephaly. Of prenatally diagnosed cases, 10–20% of CDH cases are associated with chromosomal abnormalities including trisomies 13, 18, and 21.

Pathophysiology The diaphragmatic defect seen in CDH is the result of failure of the foramen of Bochdalek to close between 8 and 10 weeks of gestation. The pathophysiology of CDH consists of fixed pulmonary and vascular hypoplasia and reversible pulmonary vascular reactivity. The herniation of abdominal contents occurs at a critical phase of lung development when branching morphogenesis generates the normal bronchial and arterial tree. The resultant pulmonary hypoplasia includes varying degrees of reduced airway branching, alveolar structures, and vascular components. This leads to decreased lung surface area for gas exchange as well as a fixed increase in pulmonary vascular resistance. The pulmonary vasculature is also morphologically abnormal, with hypermuscular peripheral pulmonary arteries that have a thickened media. This causes increased pulmonary vasoreactivity and pulmonary hypertension. This resulting pulmonary hypertension leads to persistence of the fetal circulation, with shunting

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through the ductus arteriosus or foramen ovale, which then causes acidosis and hypoxemia. The severity of CDH is related to the timing of herniation as well as the volume occupied by the herniated abdominal viscera in the thoracic cavity. If herniation occurs after lung development is nearly complete, the manifestations of the disease are much less severe, and a better outcome is seen. If, however, herniation occurs earlier in development, severe lung hypoplasia occurs, leading to a poorer prognosis. CDH therefore can be thought of as a spectrum of disease, ranging from mildly affected infants with relatively normal lungs to those with such severe hypoplasia that survival is unlikely.

Diagnosis CDH is most often diagnosed prenatally on screening anatomic ultrasound, with the differential diagnosis including diaphragmatic eventration, bronchogenic cysts, bronchial atresia, enteric cysts, congenital cystic adenomatoid malformation, bronchopulmonary sequestration, and teratoma. Diagnosis of CDH on ultrasound depends on visualization of abdominal organs in the chest. The pathognomonic finding is a fluidfilled stomach on a transverse view posterior to the left heart in the lower thorax. Other features that are often seen on ultrasound include small abdominal circumference, right mediastinal shift, and no evidence of the stomach below the diaphragm. When CDH is present on the right, the right lobe of the liver is usually herniated, which often leads to misdiagnosis because the liver has similar echogenicity to the lung. In this case the diagnosis is often missed altogether or confused with a solid chest mass. However, hepatic vasculature can be identified by ultrasound and MRI techniques (Fig. 5a) to allow excellent discrimination. Because CDH has a wide range in severity and a high frequency of associated anomalies, a complete prognostic assessment is critical (Hedrick 2013). This includes high-resolution ultrasound, fetal MRI, echocardiography, and genetic testing, all between 20 and 24 weeks gestation. This time frame allows for complete counseling for families, with the option for elective termination. The

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a

Liv

b

Fetal CDH Associated Anomalies

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Detailed sonography Ultrafast MRI Fetal echocardiogram Amniocentesis

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Isolated Anomaly

Prognostic evaluation Gestational age Degree of herniation Polyhydramnios O/E LHR < 25% Liver up

Fetoscopic balloon tracheal occlusion if within the context of a clinical trial

Planned delivery with postnatal therapy

Fig. 5 (a) Sagittal section of fetal MRI demonstrating liver (Liv) herniated above the diaphragm. The stomach (S) is also seen in the thorax posterior to the liver. (b) Algorithm for the management of fetal CDH

extreme importance of accurate counseling has led to investigation of factors predictive of poor outcome in CDH fetuses. CDH with associated major anomalies has a very poor prognosis. The

only reports of CDH survivors with congenital heart disease (CHD) have a combination of relatively mild CDH and cardiac biventricular anatomy. Mortality associated with severe CDH and

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univentricular CHD nears 100%, and comfort care should be offered. Poor outcomes are also associated with familial CDH, bilateral CDH, CDH associated with specific genetic abnormalities, and syndromic CHD. Liver herniation has historically been the most important poor prognostic indicator in CDH and can be assessed by ultrasound or MRI. In leftsided CDH, the presence of liver in the chest is associated with a very large defect, indicative of early herniation of viscera, causing severe pulmonary hypoplasia. A recent study showed mortality of 65% when the liver is up versus 7% when the liver is below the diaphragm. In addition, liver position proved to be predictive of the need for postnatal extracorporeal membrane oxygenation (ECMO), with 80% of liver up patients requiring ECMO, versus 25% of liver down patients. In addition to herniation of the liver, various indirect measurements of lung volume have been developed with prognostic relevance to CDH. The ratio between right lung area (measured at the level of the four-chamber heart view) and head circumference (LHR) can be measured by ultrasound and has been validated as a prognostic indicator when measured between 22 and 24 weeks gestation. The clinical utility of LHR is controversial, as the measurements are subjective and widely dependent on the skill and experience of the sonographer. The most widely used lung measurement to predict morbidity and mortality is the observed to expected lung area to head circumference ratio (O/E LHR), which is measured by ultrasound or MRI. However, many CDH patients who have what appears to be an adequate lung volume for survival have significant morbidity and mortality from the disease due to pulmonary hypertension. Therefore, it is unlikely that prenatal lung volume estimations will ever provide complete prognostic accuracy due to the poor correlation between lung volume and pulmonary vascular bed reactivity.

Treatment of CDH Prenatal management of CDH begins with thorough counseling, which relies heavily on an accurate diagnosis. It is paramount that the family understands the severity of CDH and the possible

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pre- and postnatal events that accompany it. The potential for poor outcome in a severe case of CDH, including death and severe pulmonary, gastrointestinal, and neurologic morbidity, should be discussed. The standard prenatal management for CDH is expectant, with ultrasound screening for prenatal complications. The majority of pregnancies with isolated CDH deliver at term, with a 3–8% stillbirth rate. CDH infants with polyhydramnios due to kinking of the gastroesophageal junction are at increased risk of preterm labor. Prematurity and its associated pulmonary insufficiency are often lethal when combined with the pulmonary hypoplasia seen in severe CDH. Ultrasound is recommended once a month up to 32 weeks gestation and then weekly to screen for polyhydramnios. The current algorithm for management of fetuses with CDH is shown (Fig. 5b). The first attempted fetal intervention for CDH involved a patch repair of the defect. However, fetuses with liver up did not tolerate this intervention due to kinking of the umbilical vein, which led to intrauterine demise. In addition, there was no significant difference in survival for liver down-treated CDH fetuses repaired in utero when compared with postnatal repairs. Because of these limitations, open fetal repair was abandoned (Harrison et al. 1997). Tracheal occlusion (TO) (Deprest et al. 2010) is a more recent fetal intervention of interest for CDH and treatment of pulmonary hypertension. The theory behind TO for CDH is that fetal lungs are net producers of lung fluid and that lung growth is related to airway fluid pressure, normally regulated by laryngeal mechanisms. It has been shown in animal models that shunting fluid from the lungs to the amniotic space can induce pulmonary hypoplasia but that fetal lungs undergo hyperplastic growth when the trachea is occluded. Accelerated lung growth and improved pulmonary function have been shown in the rat nitrofen and fetal lamb models of TO in CDH. However, clinical trials for TO using open and fetoscopic approaches have shown mixed results, including a prospective trial performed at Children’s Hospital of Philadelphia (Flake et al. 2000) showing that neonates with CDH treated with TO had severe respiratory compromise, even when lung growth

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had occurred. A randomized, controlled trial of fetoscopic TO from UCSF failed to show benefit. More recently, Jan Deprest et al. (2011) along with the Eurofetus study group have applied a minimally invasive method for TO using a deployable balloon inserted through a single small trocar. The initial reported results are promising, and a multicenter randomized controlled trial in North America and Europe known as the Tracheal Occlusion to Accelerate Lung Growth trial has recently begun and will evaluate the efficacy of this technique. At the present time the efficacy of TO for CDH is unproven, and there is potential for harm using this technique. It should only be done in the context of a well-designed clinical trial to establish efficacy prior to further clinical dissemination.

Outcomes in CDH Currently, survival for infants born with CDH at a tertiary center is 70–92%, which represents an improvement in survival relative to several decades ago. However, it is important to note with any discussion of CDH survival that comparisons can only be made between patients that are accurately stratified for severity. Improved survival is credited to a shift from early surgical intervention and aggressive ventilatory management to delayed surgery and parenchymal sparring strategies such as permissive hypercapnia and early ECMO if ventilatory criteria are exceeded. These numbers do not take into account cases of CDH that die outside a tertiary center or fetal loss due to abortion or stillbirth. Transport of infants with CDH is associated with worse survival than infants who are born at a tertiary center. Morbidity for CDH survivors includes respiratory, musculoskeletal, nutritional, gastrointestinal, and neurological complications. The CHOP Pulmonary Hypoplasia Program has prospectively evaluated over 300 CDH survivors. Of the 41 CDH survivors initially studied, 90% were found to have abnormal muscle tone at 6 months and 51% at 24 months. Many CDH survivors suffer from diminished neurocognitive and language skills, and the risk of autism significantly increased (Danzer et al. 2016).The high incidence

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of morbidity combined with the increasing survival of CDH patients to discharge creates the prerogative for ongoing coordinated care for these patients.

Myelomeningocele Myelomeningocele (MMC) occurs in approximately 1 in every 3000 live births and remains one of the most common congenital defects despite widespread appreciation of the preventative effects of folic acid supplementation. This condition is characterized by a defect in the vertebral arches allowing protrusion of the meninges and neural elements with devastating neurologic consequences including paralysis of the lower extremities, developmental delay, and incontinence of bowel and bladder. MMC represents the first application of fetal surgery to a nonlethal disorder, culminating in the recent publication of the Management of Myelomeningocele Study (MOMS), which demonstrated a clear advantage of prenatal closure of MMC compared to standard postnatal treatment (Adzick et al. 2011; Adzick 2013).

Pathophysiology and Natural History The conceptualization and validation of the “two-hit” hypothesis were a critical step in the consideration of MMC as a compelling target disorder for fetal therapy, despite its nonlethal nature. The first “hit” is the primary failure of neural tube closure, allowing for the resultant second “hit,” which is exposure of the neural elements to amniotic fluid and mechanical trauma within the intrauterine environment. There is a body of clinical and experimental evidence supporting the concept that the majority of the neural damage is related to the second hit, creating the compelling rationale for fetal surgical closure. The fetal lamb MMC model was most influential in supporting a clinical trial of prenatal MMC closure by confirming that amniotic fluid exposure of the exposed neural elements resulted in severe neural damage which could be prevented by prenatal closure of the defect (Meuli et al. 1995). In addition to

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the open neural defect, almost all fetuses with MMC display a constellation of neuroanatomic abnormalities referred to as the Arnold-Chiari II malformation, characterized by descent of the posterior fossa contents through the foramen magnum, with resultant hindbrain herniation, inferior displacement of the cerebellar vermis, and elongation and kinking of the medulla. The hindbrain herniation impairs normal circulation of cerebral spinal fluid and results in development of hydrocephalus requiring shunt placement in 80–90% of cases. Almost half of these patients experience shunt complications, including failure secondary to obstruction or infection within the first year. This contributes significantly to the morbidity and mortality of MMC as well as the cognitive deficit. Although 70% of postnatally repaired MMC patients have an IQ higher than 80, only half are able to live independently as adults, even with adapted accommodations.

Diagnosis Expectant mothers may be referred to a fetal surgery center with abnormal screening blood work, such as an elevated maternal serum AFP level, which is suggestive of a neural tube defect (NTD) and a concerning screening ultrasound. These patients will likely require further workup including a dedicated ultrasound and MRI to characterize the spinal cord defect as well as any associated brain abnormalities. An amniocentesis should also be performed to detect potential associated syndromes. MMC lies on one end of a spectrum of spinal dysraphism that includes myelocele, meningocele, and lipomyelomeningocele, among others, and counseling a family with regard to options and outcomes necessitates clarity of the diagnosis. Ultrasonography is still the mainstay of MMC imaging and is used to assess for lower extremity function, clubfoot anomalies, and spinal level of the defect and to rule out other associated gross structural malformations. Ultrafast sequencing techniques for fetal MRI are a particularly useful adjunct to better elucidate the defect and associated CNS abnormalities, including hindbrain herniation and hydrocephalus (Fig. 6a, b).

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Treatment The algorithm for treatment of MMC is shown (Fig. 6c). Fetal MMC repair is offered to patients based on the inclusion criteria established in the MOMS trial, including singleton pregnancy with an MMC at level T1 through S1, Arnold-Chiari II malformation, gestational age 19 to 25 weeks, and normal karyotype without coexisting severe anomalies. The operative procedure begins with a low transverse laparotomy, followed by creation of a hysterotomy as described above. The fetus is positioned to expose the MMC lesion. Continuous intraoperative fetal echocardiographic monitoring is critical. Fetal anesthesia is provided by the maternal inhalational anesthetic, and a narcotic dose is delivered intramuscularly to the fetus. The cystic membrane of the MMC is excised and the spinal cord untethered. The dura is reflected over the defect and closed with a running suture, followed by the paraspinal myofascial flaps, and then the skin. If the skin cannot be closed primarily, an acellular dermal graft is used to assist with the closure. Cesarean delivery is mandated for this and all subsequent pregnancies. Outcomes The MOMs trial was powered to recruit 200 participants but was halted after randomization of 183 patients when a planned interim analysis demonstrated clear benefit for prenatal surgery (Adzick et al. 2011). The fetal surgery group showed significant reduction in rates of shunt placement at 1 year (40% versus 82%) and improvement in neuromotor function by 30 months of age, including the ability to walk without orthotics (42% vs. 21%). The degree and presence of hindbrain herniation were also improved, with no hindbrain herniation in 36% of fetal surgery patients and 4% of postnatal surgery patients and severe hindbrain herniation in 6% of fetal surgery patients and 22% of postnatal surgery patients. The benefits of fetal repair outweighed the complications related to prematurity and the maternal morbidity seen in the study (Golombeck et al. 2006).

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b

a

HB

HB

c

Fetal MMC Detailed sonography Ultrafast MRI Fetal echocardiogram Amniocentesis

Associated Anomalies

Hindbrain Herniation and T1 –S1

Counsel

Prenatal Repair

GA < 26 weeks

No Hindbrain Herniation and/or S2 and below

Isolated anomaly/No maternal exclusions

GA >26 weeks

Term cesarean delivery with postnatal surgery

Fig. 6 (a) MRI appearance of hindbrain (HB) herniation in Arnold-Chiari II malformation. (b) Reversal of hindbrain herniation 3 weeks after fetal repair of MMC. Fluid

spaces in the cisterna magna are uniformly restored after fetal repair. (c) Algorithm for management of fetal MMC

Sacrococcygeal Teratoma

and a small external component, and type IV tumors are entirely presacral without external or intrapelvic extensions.

Sacrococcygeal teratoma (SCT) is the most common solid tumor in the neonate with an incidence of 1 in 40,000 births and a female-to-male ratio of 4:1. These tumors arise from the primitive streak and are composed of elements from all three germ layers. The American Academy of Pediatrics Surgical Section classifies SCTs according to their relation to the pelvis: type I tumors are external, with a small presacral component, type II tumors are predominantly external with intrapelvic extension, type III tumors are predominantly internal with intrapelvic and intra-abdominal extension

Pathophysiology and Natural History SCTs are predominantly benign, though they have malignant potential. The majority of patients diagnosed late in gestation or postnatally do well after complete resection, which includes complete removal of the coccyx to prevent recurrence. The mortality rate for a prenatally diagnosed SCT ranges from 30% to 50%. This high mortality is attributed to a variety of factors. These prenatally diagnosed tumors are often large, and mass effect

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131

Diagnosis Ultrasound can be used to confirm the diagnosis and characterize the mass in terms of size, composition (cystic versus solid), and vascularity. Frequent surveillance is key in following high-risk tumors, defined as large, rapidly growing, predominantly solid tumors that exhibit high blood flow. Surveillance includes frequent echocardiography and Doppler blood flow measurements to assess the evolution of high-output physiology. MRI aids in providing anatomic definition and assessing intrapelvic extension (Fig. 7a).

compression against the rim of the hysterotomy in this position, and the fetus should be continuously monitored for signs of cord compression. Care must be taken to keep the remainder of the fetus within the amniotic sac; inadvertent delivery of the whole fetus can lead to uterine contraction, inability to place the fetus back in the amniotic sac, and preterm labor. Once the tumor is exteriorized, a Hegar dilator should be placed in the rectum to delineate anatomy, and the skin around the anorectal sphincter is incised. Fetal skin around the base of the tumor is then incised, controlling the large subcutaneous veins. A tourniquet is applied around the base of the tumor where the skin has been incised to restrict blood flow to the tumor. A handheld harmonic scalpel is then used to divide the tumor at its base, using suture ligation for larger vessels. Any intrapelvic component of the tumor should be left as well as the coccyx, to be excised at the time of definitive resection postnatally. Once the tumor bed is hemostatic, the fetus can be returned to the amniotic cavity and the hysterotomy closed, as described in previous sections. Postoperatively, because of the risk of maternal mirror syndrome, maternal fluid balance should be closely monitored, and fetal echocardiography should also be performed frequently to follow resolution of the hydrops and placentomegaly.

Treatment The evolution of high-output physiology and secondary hydrops in a fetus with SCT is nearly always associated with fetal demise and supports the rationale for performing open fetal surgery. Fetuses with large type I tumors exhibiting clear evidence of early hydrops related to tumor flow prior to 28 weeks gestation are candidates for open fetal surgery with debulking of the tumor. Fetal intervention aims to prevent progression of vascular steal phenomenon and high-output physiology. If hydrops or placentomegaly should develop after 28 weeks, early delivery with debulking is recommended. This allows stabilization of the critically ill newborn in the neonatal intensive care unit (NICU) prior to definitive resection. The hysterotomy site is chosen to allow exteriorization of the tumor and the caudal end of the fetus. However, the umbilical cord is at risk for

Outcomes Fetal SCT represents the most challenging of the anomalies treated by open fetal surgery. The derangement of fetal and maternal physiology results in a high rate of preterm labor with relatively short intervals between fetal intervention and delivery. For appropriately selected fetuses, survival rates of 50–70% can be expected; however, quality of life is variable with a high potential for severe morbidity. Parents should be fully informed of both the negative and positive outcomes after fetal intervention, and fetal surgery should only be undertaken when the specific indication of high-output cardiac failure is present with evidence of impending cardiac decompensation and early hydrops. After 27–28 weeks, preemptive cesarean delivery at the first sign of fetal or maternal decompensation is preferable to fetal surgery with immediate debulking of the tumor

can lead to maternal-obstetric complications and preterm labor with associated fetal demise. More acutely, SCTs can hemorrhage internally causing rapid enlargement of the tumor, leading to fetal anemia. SCTs can also rupture into the amniotic cavity, resulting in sudden death. Arteriovenous shunting and the associated vascular steal phenomenon can lead to high-output cardiac failure, placentomegaly, and fetal hydrops. Fetal mortality approaches 100% once these latter processes develop. Prenatal indicators of poor prognosis include tumor size, rate of growth, predominantly solid composition, high vascularity, signs of highoutput cardiac failure, placentomegaly, hydrops, and the occurrence of maternal complications.

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a

b

Fetal SCT

US, fetal echocardiogram, MRI, amniocentesis High Risk SCT Serial US, echocardiography

AAPSS Type 1 Progressive Evolution of High output cardiac failure < 30 weeks

Progressive Evolution of High output cardiac failure > 30 weeks

Precipitous development of high output cardiac failure > 27 weeks

Low Risk SCT

Type II, III, IV

Tumor Hemorrhage, Impending Preterm labor Abnl Dopplers, Abnl due to biophysical profile, fetal heart tracings polyhydramnios/ tumor, > 27 weeks >27 weeks

Early Delivery

Fetal Surgery

Active Preterm labor, Maternal Mirror, Placentomegaly

No maternal or placental compromise

Emergency CS

EXIT Procedure

Elective CS after 36 weeks

Fig. 7 (a) Coronal section on MRI of fetus with large SCT. (b) Algorithm for management of fetal SCT

and transfer to the NICU (Roybal et al. 2011). An algorithm for management of the fetus with SCT is shown in Fig. 7b.

prevalence of TTTS is approximately 1 in 2000 pregnancies and usually occurs during the second trimester. TTTS has a variable and unpredictable course. If untreated, it is associated with a nearly 90% mortality rate for both fetuses.

Twin-to-Twin Transfusion Syndrome Twin-to-twin transfusion syndrome (TTTS) is a fetal malformation that affects 10–15% of monochorionic diamniotic pregnancies. The overall

Pathophysiology of TTTS TTTS is caused by chorionic plate anastomoses between the two fetal circulations that cause unbalanced circulation exchange. Studies using a

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radiologic tracer have shown that inter-twin transfusion is nearly universal in TTTS. True connections between pairs of arteries (AA) or veins (VV) from the two fetal circulations are located on the chorionic plate. These anastomoses are bidirectional, and the net flow direction is determined by pressure differences between the circulations. Anastomoses between a chorionic vein and the twin’s chorionic artery lead to transfusion of blood from one twin to the other in a single direction and are referred to as arteriovenous (AV) anastomoses. These AV anastomoses are often multiple and balanced by other AV anastomoses in the opposite direction. TTTS is most often seen when AV anastomoses are present without AA anastomoses. In TTTS, the donor twin becomes hypovolemic and oliguric, while the recipient twin becomes hypervolemic and polyuric. Because of these changes, the donor twin has activation of the renin-angiotensin system in an effort to preserve intravascular volume. This leads to hypertension, reduced placental perfusion, and growth retardation. On the other hand, the recipient twin has increased renal perfusion and urine output to counter the volume overload and also may be exposed to renin-angiotensin upregulation through placental shunts. The recipient commonly has cardiac abnormalities, including myocardial hypertrophy, increased velocities of pulmonic and aortic outflow, AV valve regurgitation, as well as right ventricular outflow obstruction and pulmonic stenosis, which may be from increased cardiac afterload caused by systemic hypertension.

Diagnosis of TTTS Diagnosis of TTTS begins with a monochorionic twin gestation with a single placental mass, a thin inter-twin membrane often less than 2 mm thick, concordant fetal gender, and the absence of a “twin peak” sign. All monochorionic diamniotic twin gestations should be screened frequently, starting in the second trimester. The first sign of TTTS on ultrasound is unequal amniotic fluid volumes between the two amniotic sacs. To make the diagnosis, the donor fetus must have oligohydramnios with a deepest vertical pocket of 8 cm) Stage I plus no visible bladder in donor fetus Stage II plus Doppler abnormality of reverse flow in the ductus venosus, absent or reverse end diastolic flow in the umbilical artery, or pulsatile flow in the umbilical vein Stage II or III and hydrops fetalis in either fetus Demise of one or both fetuses

polyhydramnios with a deepest vertical pocket of >8 cm. In addition, a severely abnormal Doppler waveform will be seen in the donor umbilical artery. As the disease progresses, evidence of an abnormal ductus venosus waveform, cardiomyopathy, and hydrops may be seen. The presence or absence of a visible bladder provides important staging information and should be assessed. TTTS is staged clinically based on guidelines proposed by Quintero in 1999 (Table 2) (Quintero et al. 1999). The Quintero staging system is useful to compare treatment results as well as to decide which management strategy to employ. The Quintero system does not, however, include cardiovascular factors that are important for prognosis. The CHOP cardiovascular scoring system described by Rychik and colleagues (Rychik et al. 2007) is more useful for assessing disease severity and selecting appropriate fetal intervention candidates. It should be noted that TTTS does not progress from one stage to the other in an orderly fashion. A full anatomic scan should be performed to rule out other defects, ascites, hydrops, or preexisting brain damage, as well as assessment of maternal cervical length to determine if cerclage is necessary. Fetal echocardiography should also be performed to evaluate cardiac function.

Treatment of TTTS The current mainstay for treatment of TTTS is fetoscopic selective laser photocoagulation (SLPC) targeting the anastomoses that contribute to the imbalance of flow, performed between 18 and 26 weeks gestation (Senat et al. 2004). Historically, amnioreduction was the primary treatment modality for TTTS but is now rarely applied as primary therapy unless TTTS develops outside

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the gestational age where SLPC is safe. The treatment for Stage I TTTS is a controversial subject because most Stage I patients do not progress to a later stage, but a trial of SLPC for Stage I disease is currently underway in Europe. SLPC is performed percutaneously, most often under local anesthesia. A 2–3 mm fetoscope is inserted, with or without a trocar, under ultrasound guidance. The placental vasculature is mapped using direct visualization as well as Doppler ultrasound to identify anastomoses and to define the placental equator. All anastomoses between the two placental circulations are targeted for ablation with a 30–50 W diode laser. Amnioreduction may also be performed at the end of the procedure if necessary to reduce intrauterine pressure. Because of the incidence of both early and late complications of SLPC, close follow-up is important for all patients.

Outcomes of TTTS The Eurofetus trial was a multicenter randomized controlled trial that compared serial amnioreduction to SLPC for TTTS. The laser therapy group had higher survival of at least one fetus to at least 28 days of age, 76% vs. 56% in the amniocentesis group. In addition, the laser group had a higher mean gestational age at delivery, with an average of 33 vs. 29 weeks in the amniocentesis group. Most importantly, at 6-month followup, the laser group had improved neurologic outcomes, with a decreased risk of periventricular leukomalacia. While SLPC is much less invasive than it once was, there are still significant complications that accompany the procedure. Aside from the complications associated with fetoscopy itself, SLPC can be complicated by pseudoamniotic band sequence, TTTS recurrence, iatrogenic monoamnionicity, and twin anemia polycythemia sequence, which is defined as anemia in one fetus and polycythemia in the co-twin with normal AFV in both fetal sacs. A major long-term concern for TTTS survivors is neurodevelopmental abnormalities, affecting 6–25% of patients treated with SLPC (van Klink et al. 2016). These range from minor defects to major abnormalities

A. M. Olive et al.

including cerebral palsy, blindness, hemiparesis, and spastic quadriplegia.

Conclusion and Future Directions Fetal surgery has seen dramatic progress in the last three decades, especially in the ability to diagnose, appropriately select, and treat fetuses with structural malformations that, if left untreated, would result in fetal demise or severely affect quality of life. In some cases, fetal surgery has clearly altered the natural history of the disease and improved outcomes, namely, CCAM, TTTS, and MMC. In order for the field to continue to grow, several areas require continued study. First, maternal and fetal risk remain high, and renewed efforts to reduce morbidity and mortality associated with maternal-fetal intervention are paramount, including improvement in maternal tocolysis to control frequent preterm delivery. In addition, further innovations in endoscopic instrumentation and imaging modalities will contribute to more advanced minimally invasive approaches to replace open procedures. Furthering capabilities for image-guided interventions to safely permit diagnosis and treatment at even earlier gestational time points will decrease the risk of preterm labor and premature delivery. Randomized controlled trials when appropriate are essential to establish a clear benefit of maternal-fetal surgery for patients, allowing experimental therapies to move into clinical application.

Cross-References ▶ Congenital Airway Malformations ▶ Congenital Diaphragmatic Hernia ▶ Congenital Malformations of the Lung ▶ Extracorporeal Membrane Oxygenation for Neonatal Respiratory Failure ▶ Fetal Counseling for Congenital Malformations ▶ Prenatal Diagnosis of Congenital Malformations ▶ Spina Bifida and Encephalocele

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References Adzick NS. Open fetal surgery for life-threatening anomalies. Semin Fetal Neonatal Med. 2010;15(1):1–8. Adzick NS. Fetal surgery for spina bifida: past, present, future. Semin Pediatr Surg. 2013;22(1):10–7. Adzick NS, Kitano Y. Fetal surgery for lung lesions, congenital diaphragmatic hernia, and sacrococcygeal teratoma. Semin Pediatr Surg. 2003;12(3):154–67. Adzick NS, Thom EA, Spong CY, et al. A randomized trial of prenatal versus postnatal repair of Myelomeningocele. N Engl J Med. 2011;364 (11):993–1004. Bouchard S, Johnson MP, Flake AW, et al. The EXIT procedure: experience and outcomes in 31 cases. J Pediatr Surg. 2002;37:418–26. Bulas D. Fetal magnetic resonance imaging as a complement to fetal ultrasonography. Ultrasound Q. 2007;23 (1):3–22. Chervenak FA, McCollough LB. Ethics of maternal-fetal surgery. Semin Fetal Neonatal Med. 2007;12 (6):426–31. Danzer E, Hoffman C, D’Agostino JA, et al. Neurodevelopmental outcomes at 5 years of age in congenital diaphragmatic hernia. J Pediatr Surg. 2016; pii: S0022–3468(16)30284–6. Deprest JA, Flake AW, Gratacos E, et al. The making of fetal surgery. Prenat Diagn. 2010;30:653–67. Deprest J, Nicolaides K, Done’ E, et al. Technical aspects of fetal endoscopic tracheal occlusion for congenital diaphragmatic hernia. J Pediatr Surg. 2011;46:22–32. Flake AW, Crombleholme TM, Johnson MP, et al. Treatment of severe congenital diaphragmatic hernia by fetal tracheal occlusion: clinical experience with fifteen cases. Am J Obstet Gynecol. 2000;183:1059–66. Geaghan SM. Fetal laboratory medicine: on the frontier of maternal-fetal medicine. Clin Chem. 2012;58 (2):337–52. Golombeck K, Ball RH, Lee H, et al. Maternal morbidity after maternal-fetal surgery. Am J Obstet Gynecol. 2006;194(3):834–9.

135 Harrison MR, Golbus MS, Filly RA, et al. Fetal surgery for congenital hydronephrosis. N Engl J Med. 1982;306:591–3. Harrison MR, Adzick NS, Bullard KM, et al. Correction of congenital diaphragmatic hernia in utero VII: a prospective trial. J Pediatr Surg. 1997;32:1637–42. Hedrick HL. Management of prenatally diagnosed congenital diaphragmatic hernia. Semin Pediatr Surg. 2013;22 (1):37–43. Hopkins LM, Feldstein VA. The use of ultrasound in fetal surgery. Clin Perinatol. 2009;36(2):255–72. Jancelewicz T, Harrison MR. A history of fetal surgery. Clin Perinatol. 2009;36(2):227–36. Meuli M, Meuli-Simmen C, Hutchins GM, et al. In utero surgery rescues neurologic function at birth in sheep with spina bifida. Nat Med. 1995;1:342–7. Moldenhauer JS. Ex utero intrapartum therapy. Semin Pediatr Surg. 2013;22(1):44–9. Quintero RA, Morales WJ, Allen MH, et al. Staging of twin-twin transfusion syndrome. J Perinatol. 1999;19(8 Pt 1):550–5. Roybal JL, Moldenhauer MS, Khalek N, et al. Early delivery as an alternative management strategy for selected high-risk fetal sacrococcygeal teratomas. J Pediatr Surg. 2011;46:1325–32. Rychik J, Tian Z, Bebbington M, et al. The twin-twin transfusion syndrome: spectrum of cardiovascular abnormality and development of a cardiovascular score to assess severity of disease. Am J Obstet Gynecol. 2007;197(4):392.e1–8. Senat MV, Deprest J, Boulvain M, et al. Endoscopic laser surgery versus serial amnioreduction for severe twinto-twin transfusion syndrome. N Engl J Med. 2004;351:136–44. van Klink JM, Koopman HM, Rijken M, Middeldorp JM, Oepkes D, Lopriore E. Long-term neurodevelopmental outcome in survivors of Twin-to-Twin Transfusion Syndrome. Twin Res Hum Genet. 2016;19(3):255–61. Wilson RD, Johnson MP, Flake AW, et al. Reproductive outcomes after pregnancy complicated by maternalfetal surgery. Am J Obstet Gynecol. 2004;191 (4):1430–6.

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Specific Risks for the Preterm Infant Emily A. Kieran and Colm P. F. O’Donnell

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Respiratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Respiratory Distress Syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pneumothorax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pulmonary Hemorrhage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bronchopulmonary Dysplasia (BPD) and Chronic Lung Disease (CLD) . . . . . . . . . . . . . Apnea of Prematurity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

139 139 140 140 140 141

Cardiovascular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Patent Ductus Arteriosus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Congenital Heart Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Central Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

141 141 141 142 142

Retinopathy of Prematurity (ROP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Gastrointestinal Tract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Feeding and Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Necrotizing Enterocolitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spontaneous Bowel Perforation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

143 143 143 144

E. A. Kieran Department of Neonatology, The National Maternity Hospital, Dublin, Ireland National Children’s Research Centre, Dublin, Ireland School of Medicine and Medical Science, University College Dublin, Dublin, Ireland C. P. F. O’Donnell (*) National Maternity Hospital, Dublin, Ireland School of Medicine, University College Dublin, Dublin, Ireland National Children’s Research Centre, Crumlin, Dublin, Ireland e-mail: [email protected] # Springer-Verlag GmbH Germany, part of Springer Nature 2020 P. Puri (ed.), Pediatric Surgery, https://doi.org/10.1007/978-3-662-43588-5_9

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E. A. Kieran and C. P. F. O’Donnell Inguinal Hernia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Umbilical Hernia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Infection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hyperbilirubinemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

145 145 145 145

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

Abstract

Preterm birth – birth before 37 completed weeks of gestation – occurs in approximately 5–18% of births worldwide. Babies born preterm have increased mortality and are at a greater risk of morbidity and long-term adverse outcomes than infants born at term. Though the rate of preterm birth is relatively lower in developed countries than in developing countries, prematurity is the leading cause of neonatal mortality in both developing and developed countries. Infants born prematurely have less time to develop in utero, and their organs and body systems are still undergoing physiological development process at the time of birth. This immaturity of body organs combined with low birth weight puts preterm infants at risk of developing various short- and long-term complications. Babies born extremely preterm (60 breaths per minute); expiratory grunting; intercostal, subcostal, and sternal recessions; nasal flaring; cyanosis; and low oxygen saturations and may be further complicated by apnea and bradycardia. Significant advances in the prevention and management of RDS have occurred over the last 40 years. Administration of intramuscular corticosteroids to women who are at risk of delivering

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preterm reduces the risk of death from and severity of respiratory disease in preterm infants (Liggins and Howie 1972; Papageorglou et al. 1979; Gamsu et al. 1989). Exogenous surfactant therapy reduced mortality and respiratory morbidity in preterm infants with RDS (Fujiwara et al. 1980; Hallman et al. 1985; Enhorring et al. 1985; Shapiro et al. 1985; Jobe 1993; Wiswell 2001). Improvements in knowledge and methods of invasive and noninvasive ventilation in preterm infants have also improved their outcome (Chernick 1973; Cox et al. 1974; Kattwinkel et al. 1973; Rhodes and Hall 1973; Morley et al. 2008; SUPPORT Study Group 2010).

Pneumothorax Pneumothoraces in preterm infants are associated with increased mortality and severity of lung disease along with other long-term morbidities. The main precipitator of pneumothoraces is RDS, and, similar to RDS, the risk of pneumothorax is largest in the more preterm infants with approximately 7% of infants born 20 ml/kg over 24 h) ii. Hyperglycemia >140 mg/dL without alternative etiology

sepsis were medically related (84.4%) and most sources of sepsis were respiratory (47.8%), followed by blood stream infections (21%) and central nervous system infections (16.2%) (Wolfler et al. 2008). While prospective multicenter data from the United States are lacking, several large retrospective studies have reported an annual incidence of sepsis at 0.56 cases per 1,000 children each year (Watson et al. 2003). A 2009 study from Washington State reported a mortality rate of 6.8% for children admitted with a diagnosis of severe sepsis. While this number is much lower than the European reports, another 6.5% of this cohort

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later died on readmissions for recurrent sepsis (Czaja et al. 2009). These children generally had comorbid conditions, and their study demonstrated an overall mortality of 34.2% in children with significant comorbidities. Despite the uncertainty regarding its true prevalence, sepsis remains one of the top four killers of children as reported by the World Health Organization and the cause of death for more than 25% of the general population (Watson et al. 2003). Nevertheless, improved understanding of the pathophysiology and treatment of sepsis has resulted in dramatic decreases in sepsis-related mortality from reports as high as 97% in the 1960s to an estimated 10% today (Czaja et al. 2009). Continued improvements may occur if adequate resuscitation and guidelines are effectively utilized.

shedding of cells (skin, respiratory tree, gastrointestinal tract). Other ubiquitous mechanisms include the relative acidic environment of the skin, gastric acidity, and intestinal peristalsis. Immunoglobulin-A (IgA) secretions are prevalent in the tracheobronchial tree and intestine and act to diminish bacterial adherence. For any infection to occur, these barriers must be breached. Numerous factors play a role in altering barrier function; these include polymicrobial sepsis, trauma, malnutrition, burns, shock, immunosuppression, immaturity, reperfusion injury, and various medications. These factors, combined with virulent bacteria, may result in loss of barrier integrity with subsequent tissue edema and epithelial activation, which may lead to progressive dysfunction.

Pathogenesis

Host Response

The pathogenesis of sepsis is multifactorial, with host defense mechanisms and bacterial virulence factors as its principal determinants. The process is initiated by the pathogen’s ability to evade host defenses including mucous, lysozymes, and defensins to bind to the epithelial barrier. Subsequently, bacterial-epithelial interactions lead to induction of virulence genes and expression of virulence factors. This is followed by host pathogen recognition and activation of pro-inflammatory signaling pathways. Undoubtedly, premature infants, immunocompromised children, and children with significant comorbidity will have altered host defenses and increased vulnerability to infection. Progression of the inflammatory cascade can then enter a positive feedback loop characterized by a pathologic or exuberant cytokine response with resultant sepsis, progression to severe sepsis, MODS, and death.

Cellular Immunity

Barriers to Infection There are numerous host defense mechanisms that limit bacterial adherence to the epithelium. These include anatomic barriers such as mucous production, the commensal flora, and the routine

The primary defense in response to infection or tissue injury is the neutrophil, which follows an orchestrated sequence of events including neutrophil adherence, diapedesis to site of injury, and activation of the neutrophil. Binding of the neutrophil to the epithelium is coordinated by expression of selectins, integrins, and immunoglobulins. The process generally begins by expression of Eselectins on activated epithelium, to which the Lselectins present on neutrophils will bind. Once this binding occurs, there is further adherence with the binding of β2 integrin on the neutrophil with ICAM-1 on the endothelial cell, a necessary step prior to initiation of PECAM-1-dependent diapedesis (Liu et al. 2012). Once the neutrophil is able to reach the source of infection, it engulfs microbes with subsequent microbial death. To accomplish this task, the neutrophil must sufficiently differentiate the microbe as different from self. Key to this process is the recognition of pathogen-associated molecular patterns or PAMPS. Examples include mannans in the yeast cell wall, lipopolysaccharides, lipoteichoic acid, and formylated peptides present in Gram-negative and Gram-positive bacteria.

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Ultimately the organisms are absorbed into phagolysosomes with subsequent exposure to lysozyme, elastase, lactoferrin, cathepsin, and defensins, which contribute to bacterial permeability and act synergistically with free radicals produced with the respiratory burst of the neutrophil. Mediators of the respiratory burst include hydroxyl radicals generated by superoxide dismutase and oxidizing chloramines, which effect microbial death.

Macrophages Macrophages are derived from monocytes and act to clear the host of cellular debris, bacteria, viruses, and tumor cells. Like the neutrophil, the macrophage plays a critical role in host cellular defense and is activated following recognition of PAMPS. Further activation occurs following stimulation by inflammatory mediators such as interferon-γ, tumor necrosis factor α, lipopolysaccharide (LPS), and heat shock protein. Further, macrophages secrete IL-12 and IL-23, activators of the humoral immune response, which further promote excretion of the pro-inflammatory cytokines IL-1 and IL-6 and chemotactic factors. Once activated, macrophages phagocytose microbes and effect cytotoxicity by generating reactive nitrogen and oxygen species via NADPH oxidases. In some cases, such as in severe sepsis, an exuberant response can occur with overproduction of these reactive species resulting in local injury thereby contributing to hepatic and pulmonary injury seen during sepsis (Laskin et al. 2011).

Lymphocytes While monocytes and neutrophils are key players in the immune response, they are not without vulnerability. Lymphocytes are derived from lymphoid progenitors in the bone marrow and complement the immunologic arsenal. They come in three varieties: the B cell, the T cell, and the natural killer (NK) cell. T cells develop following maturation in the thymus, whereas B cells develop in the bone marrow.

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Under normal circumstances, B cells represent approximately 15% of circulating lymphocytes and are characterized by their ability to produce immunoglobulins. To allow for recognition of a large variety of foreign antigens, B cells undergo a process of differential antigen recognition from rearrangement of their heavy and light chains during development. Prior to antigen stimulation, “naive” B cells will enter the periphery as IgM and IgD secreting cells. Later following stimulation by T cells with IL-10, the B cell may undergo antigen rearrangement, affinity maturation, and isotype switching for subsequent production of IgG. Other cytokines such as IL-3 can induce isotype switching for production of IgE, and TGF-beta can induce secretion of IgA (Chaplin 2010). T cells require presentation of antigen for activation. Antigen presentation occurs by sensing of cell surface proteins known as major histocompatibility (MHC) proteins. These proteins come in two classes: class I are expressed by all nucleated cells while class II are only present on antigen presenting cells (APC) such as macrophages, dendritic cells, and B cells. APCs ingest foreign material, cells, or microbes and process the proteins for presentation in association with MHC class II protein. CD4-positive T cells interact with class II MHC and function to regulate cellular and humoral immune responses. CD8-positive T cells interact with class I MHC and primarily act by killing cells with alien, altered, or diminished MHC class I expression. Both CD4 and CD8 require activation prior to effecting responses. For activation of the T cell to occur, its receptor complex (CD3) must interact with the APC, and the CD4/8 ligand must bind to the appropriate MHC class. These interactions will partially activate the T cell. Further interactions with CD28 on the T cell and CD80 or CD86 on the APC result in full activation (Nurieva et al. 2009). In CD4-positive cells, this activation process results in differentiation into T helper 1 or T helper 2 subsets depending on their cytokine profile, while in CD8-positive cells, it may lead to activation of kinases and release of cytotoxic granules, perforins, and serine proteases. Release of perforins results in “perforations” of cells with

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subsequent osmotic lysis, while serine proteases activate apoptotic pathways. Recently, a subset of CD25-positive CD4 T cells known as T regulatory cells (Tregs) have been identified. They serve as additional mediators of the inflammatory response to sepsis and are known to have strong immunosuppressive activities that are important in regulating host response to infection. It is thought that Tregs play a role in T-cell anergy seen in major trauma and burn injury and may be partially responsible for subsequent increased incidence of secondary infectious complications seen in these populations. Furthermore, elevated levels of Tregs following the onset of septic shock have been correlated with increased mortality and have been implicated in both reduced lymphoproliferative response and Treg-induced immunoparalysis (Jiang et al. 2012). Several animal studies utilizing anti-CD25 therapies have attempted to blunt or eliminate the counter-regulatory effects of Tregs in sepsis with variable effect. To date the mechanisms of Treg function remain unclear, and no human studies modulating Treg response to sepsis have been attempted. Natural killer cells (NK) differ from the other T cells in that they do not undergo maturation in the thymus; rather, they develop in the bone marrow under the influence of IL-2 and IL-15. NK cells make up a small portion of the T-cell population and act as executioners only restrained by recognition of self-MHC proteins. Cells that express either too little self-MHC or alien MHC are terminated. NK cells therefore play a critical role in destruction of tumor cells and those infected with virus, which are known to have altered or diminished MHC I expression.

Humoral Factors While cell-mediated immunity is critical in host defenses, the initiation of the cellular response which includes activation of complement and production of immunoglobulins and cytokines is equally crucial for effective immunologic response.

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Complement The purpose of complement is to effectively develop and implement the “membrane attack complex.” This attack complex is the end result of three different and distinct pathways of complement activation, which result in osmotic lysis of foreign pathogens. The first pathway is the classical pathway and is dependent upon antigen-antibody interactions. Following these interactions, there are sequential activation of C1, C4, and C2, which act to generate C3 convertase. This generates C3a, a potent vasodilator and anaphylatoxin, and C3b, which covalently binds the activating antigen. C3b then activates C5 and forms the loci for development of the membrane attack complex. In the event that the attack complex fails to result in cellular lysis, C3b also acts as an opsonin, thereby enhancing phagocytosis by macrophages and neutrophils. The second pathway or alternate pathway is antibody independent and is stimulated by microbial structures such as mannans. These microbial structures bind inhibitors of spontaneous complement activation resulting in efficient deposition of C3b and subsequent development of the membrane attack complex. The third pathway is known as the lectin pathway and is also stimulated by microbial cell wall structures such as mannans. Plasma mannan-binding lectins interact with microbial mannans to generate proteases that sequentially activate C4 and C2 with subsequent generation of C3b. The importance and regulation of the complement pathway should not be underestimated. Uncontrolled activation of the pathway results in marked levels of C3a, which may a play a role in capillary leak syndromes and asthma, and with C5a (cleavage product of activated C5) sepsis. Overproduction of C5a has many detrimental effects including diminished neutrophil response, consumptive coagulopathy, and increased mortality (Klos et al. 2009). However, deficiencies in the complement pathways are associated with pathologic diseases. Deficiency of C1 results in episodes of angiogenic edema. C3 deficiency is associated with severe and often fatal pyogenic infections. C2 and C4 deficiencies are associated

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with lupus-like disease, and defects in the membrane activation complex result in increased susceptibility to Neisseria (Chaplin 2010).

Immunoglobulins Immunoglobulins are produced by B cells and the memory B cells (aka plasma cells) to effect a number of responses. These include opsonization, a process where microbes are made more susceptible to phagocytosis, complement activation, and neutralization of toxins and virulence factors. Prior to isotype switching and affinity maturation, only immunoglobulins IgM and IgD are produced. Of these, IgM is the most abundant and accounts for more than 80% of circulating immunoglobulins and constitutes the major initial response to antigenic stimuli. B-cell interactions with T cells and cytokines result in isotype switching to the other major immunoglobulins IgG, IgA, and IgE. IgG is the predominant immunoglobulin or antibody to act on viruses and bacteria. IgG binds these organisms with its FAB (fragment antigen-binding) portion, a part of the antibody with a highly variable region, which allows binding to a variety of foreign cells. The conserved portion of the antibody then binds the Fc receptor of neutrophils, monocytes, or macrophages. The FAB portions may also form immune complexes with autoantigens that can capture C3b and precipitate activation of the complement system (Lutz 2012). Several human studies have evaluated the use of intravenous IgG (IVIG) as a therapeutic modality. A recent Cochrane review of ten randomized or semi-randomized controlled trials inclusive of more than 300 neonates given IVIG for treatment of bacterial or fungal infections reported reductions in clinically suspected sepsis and mortality. However, the overall methodology of the studies was poor, and as a result the data do not clearly support IVIG as a beneficial modality (Ohlsson and Lacy 2010, 2015). A more recent study was unable to demonstrate any benefit from the use of IVIG in suspected or proven neonatal sepsis; thus the use of IVIG in

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this population remains unclear (Brocklehurst et al. 2011). Nonetheless, data from older populations suggest that significant benefit may be obtained from IVIG administration. A 2007 meta-analysis found particular efficacy with IgGAM and reported a 0.66 relative risk of mortality following therapy (Kreymann et al. 2007). Nevertheless, like the neonatal study, methodologic flaws in studies of IVIG have limited recommendations for its use and the 2012 Surviving Sepsis campaign advised against its use (Dellinger et al. 2013). IgA develops under the influence of TGF-beta and is particularly prevalent in the intestinal tract and tracheobronchial tree. It is secreted as a heterodimer with antiseptic properties and serves as an antigenic barrier. IgA plays a critical role for bacterial attachment and colonization thereby limiting overgrowth and invasion. In addition to excluding bacteria from the host, it plays a role in the prevention of epithelial injury and antigen presentation. Studies have demonstrated IgA’s ability to counteract cholera toxin and inhibit bacterial motility and uptake of luminal antigens for presentation to lymphoid cells (Pabst 2012). It is thought that premature neonates in particular are relatively deficient in IgA and therefore at higher risk of developing diseases such as necrotizing enterocolitis (NEC). Furthermore, analysis of breast milk indicates that TGF-beta may be important for stimulating production of IgA in infants (Ogawa et al. 2004).

Cytokines Cytokines constitute an important arm of the immunologic arsenal against foreign microbes. They are produced by a wide variety of cells including neutrophils, B cells, T cells, NK cells, endothelial cells, and fibroblasts, to name a few. Cytokine effects may be pro- or anti-inflammatory in nature. Pro-inflammatory cytokines include TNF-alpha, IL-1, IL-6, IL-8, IL-11, and IL-18, whereas mediators such as IL-10 and TGF-beta are anti-inflammatory. Other cytokines influence immunogenic responses and include Il-2, IL-4, IL-12, and IL-13.

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One of the early mediators of the infection response is TNF-alpha, which has a number of pro-inflammatory effects including enhanced leukocyte adhesion, neutrophil response, production of other inflammatory cytokines, priming of neutrophils and macrophages, up-regulation of thrombotic and fibrinolytic pathways, and stimulation of nitric oxide release. LPS, peptidoglycans, and other bacterial products stimulate its release. As such, elevated levels of TNF-alpha are often found in septic patients, and animal models have demonstrated multi-organ dysfunction following TNF-alpha therapy (Qiu et al. 2011). Studies in murine models of peritonitis and sepsis suggest that treatment with TNFalpha inhibitors may provide some benefit (Bojalil et al. 2013). While data remain limited, at least one study demonstrates that anti-TNF alpha therapy is associated with decreased ventilator days and ICU days among adults with severe sepsis (Rice et al. 2006). IL-1, another early cytokine associated with the inflammatory response, is produced in response to LPS or TNF-alpha stimulation. IL-1 acts to induce IL-2, IL-6, and IL-8 and mediates the febrile response. There are two isoforms of IL-1: membrane associated, or IL-1alpha, and membrane secreted, or IL-1 beta. Preliminary data demonstrate that administration of docosahexaenoic acid, an omega-3 fatty acid, is associated with attenuated IL-1 beta response and modulation of sepsis in neonates (LopezAlarcon et al. 2012). IL-6, another pro-inflammatory cytokine and a key regulator of hepatic acute phase reactants, stimulates B-cell differentiation and potentiates the development of cytotoxic T cells. Increased levels of IL-6 have been associated with the development of sepsis and may predict future sepsis (Wang et al. 2013). IL8, a pro-inflammatory cytokine produced by monocytes, macrophages, T cells, endothelial cells, and platelets, is a potent chemotactic and activating factor for neutrophils. In children with sepsis, serum levels of IL-8 less than 220 pg/ml predict survival with 94% accuracy at 28 days (Wong et al. 2008). Interferon-gamma represents another key proinflammatory mediator that is produced primarily

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by NK cells and T helper 1 cells following antigenic stimulation. It is an important activator of macrophages and increases cytokine production by antigen-presenting cells. It is known to potentiate the efficacy of antibiotic therapy and to promote intracellular production of free radicals to eliminate bacteria (Smith et al. 2010). Interferongamma’s ability to control intracellular pathogens may be partially mediated by induction of inducible nitric oxide synthase and further activation of NK cells. This is particularly important in controlling fungal, mycobacterial, viral, and intracellular bacterial infections.

Bacterial Virulence Virulence is defined as a pathogen’s ability to “enter into, replicate within, and persist in host sites that are inaccessible to commensal species” (Webb and Kahler 2008). The development of an infection is relatively rare given the constant bacterial-host interactions. This is due to both physical and immunologic barriers, as described earlier. Nonetheless just as the human has many defensive strategies, bacteria have a variety of offensive strategies, some of which can be very effective. These offensive strategies include bacterial adhesion, invasion of the host, intra- and extracellular survival mechanisms, nutrient acquisition, damage to the host, motility, biofilm production, and regulation of virulence factors. While detailed description of each strategy is beyond the scope of this chapter, we will outline a few of the key mechanisms. Bacterial adherence is critical in order for most pathogens to invade the host. A key to this interaction is the bacterial pili. Examples include Enterobacteriaceae whose pili attach to d-Mannose receptor sites on epithelial cells, with some species retracting their pili after binding. This process drags the bacteria into the cell after binding to surface receptors. Other bacterial species can expose host binding sites through breakdown of mucous following expression of sialidases. Sialidases have the added benefit of generating bacterial nutrients and can participate in biofilm

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formation. Bacteria such as B. fragilis, V. cholera, P. aeruginosa, S. pneumoniae, H. influenzae, and G. vaginalis are known to utilize sialidases (Lewis and Lewis 2012). Others such as S. aureus bind to fibronectin or other receptors on epithelial surfaces to facilitate adhesion. Following bacterial adhesion to the cell, invasion can occur via transcellular or paracellular routes. Transcellular invasion may be initiated by the host or it may be induced by the bacteria. Normally, host phagocytes will recognize bacteria by their opsonized components or by their PAMPS. This process elicits an immune response that can result in bacterial killing. However, some bacteria have developed methods to avoid this cytotoxic response and elude epithelial cells and their receptors to gain entrance into the host. Listeria monocytogenes uses E-cadherin and the heparin growth factor receptor to gain entry. Other bacteria such as N. meningitis, H. influenza, and P. aeruginosa use capsules to mask their immunogenic properties. In contrast, others have developed mechanisms to evade activation of complement or Toll-like receptors 2/4 (Sarantis and Grinstein 2012). Following phagocytosis, some species have developed methods to inhibit maturation of the phagosome (L. pneumophilia, B. abortus), escape from the cytotoxic effect of the phagolysosome, or even survive within the phagosome (M. tuberculosis). Paracellular invasion is typically accompanied by dysfunction of the epithelial barrier that can be precipitated by activation of the immune response or by the direct cytopathic effects of some virulent strains. The development of biofilms is another effective method for bacteria to evade host defenses following invasion. A biofilm creates a protective environment where colonies of bacteria can thrive in an extracellular matrix that is resistant to both host response and antibiotic therapy. Staphylococci and Pseudomonas species are notorious for their ability to form biofilms and can be particularly problematic when they colonize foreign materials such as central venous catheters or endotracheal tubes (Webb and Kahler 2008).

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Neonatal Defenses Relative to older children and adults, neonates have deficient immune systems, and infection is responsible for more than 3,000 neonatal deaths each day (Lawn et al. 2005). Early-onset neonatal sepsis typically occurs within the first 24 h of life and is characterized by vertical transmission of pathogens. The preterm infant is particularly susceptible to this form of transmission because the host response is dependent upon innate immunity, which is underdeveloped in these children. The etiology of sepsis in this cohort can be multifactorial and includes preterm labor, prolonged rupture of membranes, maternal presence of group B streptococci (GBS), and chorioamnionitis. Primary responsible pathogens include GBS (41%) and E. coli (17%) (Wynn and Levy 2010). Similar to older children, the first barriers to pathogenic invasion are physical ones. In term or near-term infants, the skin has an additional protective layer provided by the vernix, something that may be absent in the preterm. The mucosa of the tracheobronchial tree and intestine provide additional barriers. However, host defense mechanisms that are present in older children are either deficient or underdeveloped in the preterm. Examples include relative surfactant deficiency and increased goblet cell activity in the tracheobronchial tree with subsequent airway irritation and poor mucous clearance. Furthermore, the intestine is relatively deficient in IgA production, defensins, commensal, or beneficial bacteria and has decreased activity of the migratory motor complex resulting in diminished peristalsis. This leads to increased risk of overgrowth by pathogenic bacteria, adhesion to the epithelium, and subsequent gut barrier dysfunction that can result in the development of necrotizing enterocolitis in the premature infant. The nature and diversity of bacterial colonization also appear to play a critical role in intestinal immunity in the preterm infant. Initial colonization of the gastrointestinal tract is random and is dependent upon maternal vaginal flora at the time of delivery, degree of maturity, type of feeds (breast milk vs. formula), and the local

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Table 2 Age group-specific definitions for abnormal vital signs and leukocyte count Age group Newborn (0 day to 1 week) Neonate (1 week to 1 month) Infant (1 month to 1 year) Toddler/preschool (2–5 years) School-age child (6–12 years) Adolescent/young adult (13 to 180 or 180 or 180 or 140 >130 >110

RR (breaths/ minute) >50 >40 >34 >22 >18 >14

SBP (mm Hg) 10% total body weight fluid overload H. Deep vein thrombosis prophylaxis a. No recommendations in prepubertal children with severe sepsis I. Stress ulcer prophylaxis a. No recommendations in prepubertal children with severe sepsis J. Nutrition a. Provide enteral nutrition when possible

inotrope or vasopressor therapy is indicated. Choice of therapy depends on the clinical state of the patient, which may be “cold shock” characterized by low cardiac index (CI) with or without presence of hypotension and “warm shock” characterized by high CI and hypotension. In children there are multiple options for inotropic support, and these include dopamine, dobutamine, or (nor)epinephrine. Dopamine is generally used at moderate rates of infusion (5–9 μg/kg/min) for inotropic support and at higher rates (>9 μg/kg/min) for vasopressor effects. This commonly used drug works well

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for fluid-resistant hypotensive shock with low systemic vascular resistance (SVR). Dobutamine offers inotropic support but may be associated with hypotension. Norepinephrine, a first-line medication in adults, is often reserved for children resistant to dopamine therapy. Other suggested therapies include the agent terlipressin, a vasopressin-like drug, and thyroid hormone. Terlipressin is a catecholamine receptor agonist that has been evaluated in several series, but efficacy has not yet been established; neither terlipressin nor vasopressin has been incorporated into current treatment algorithms. Children and adults with sepsis are known to be relatively thyroid deficient, and it is though that hypothyroidism may diminish catecholamine responsiveness to shock (Todd et al. 2012). Nonetheless, reports on thyroid therapy for sepsis are lacking. The use of blood products during the resuscitative phase is not clear, and optimal hemoglobin level in children with sepsis is unknown. The TRIPICU trial, a randomized non-inferiority clinical trial demonstrated that a hemoglobin of 7 g/dl or greater would be safe in stabilized children with sepsis (Lacroix et al. 2012). Another recent randomized prospective trial assigned children to superior vena cava oxygen saturation (ScVO2) goal-directed therapy or control. Their protocol for children with ScVO2