Alan Daneman Pediatric BodyCT With 317 Figures Springer-Verlag London Berlin Heidelberg New York Paris Tokyo Alan Daneman, MBBCh, BSc, MRACR, FRCP(C) Associate Professor of Radiology, University of Toronto, Ontario, Canada. Staff Radiologist, Head, Division of Ultrasound and Body CT Department of Radiology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G lX8, Canada ISBN-13:978-1-4471-3139-7 e-ISBN-13:978-1-4471-3137-3 DOl: 10.1007/978-1-4471-3137-3 Library of Congress Cataloging-in-Publication Data Daneman, Alan, 1947- Pediatric body CT. Includes bibliographies and index. 1. Tomography. 2. Pediatric radiography. 1. Title. [DNLM: 1. Tomography, X-Ray Computed - in infancy and childhood. WN 240 D179p] RJ51.T65D36 1986 618.92'007'572 86--3795 ISBN-13:978-1-4471-3139-7 (U.S.) This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under §54 of the German Copyright Law where copies are made for other than private use, a fee is payable to 'Verwertungsgesellschaft Wort' Munich. © Springer-Verlag Berlin Heidelberg 1987 Softcover reprint of the hardcover 1st edition 1987 The use of registered names, trademarks etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. Product Liability: The publisher can give no guarantee for information about drug dosage and application thereof contained in this book. In every individual case the respective user must check its accuracy by consulting other pharmaceutical literature. Filmset by Computerised Typesetting Services Limited, Finchley, London N12 8LY 2128/3916 543210 Dedicated to Louise, Natasha, and Nadine. Preface Pediatric body CT began in earnest in 1976 when for the first time a body CT machine was installed in a pediatric institution, the Hospital for Sick Children in Toronto. The first images were received with great enthusiasm. More recently, newer equipment with faster scan times and better resolution has enabled us to delineate disease processes with even greater accuracy. In the past 9 years we have performed more than 5000 body scans in children. With this experience our examination techniques have changed and the indications for CT in children have been modified. CT has come to occupy an important and specific place in the management of pediatric patients. The performance of body CT studies in children is not always easy. Excellent diagnostic studies can be obtained only with a special understanding of the problems of pediatric patients and pediatric pathology. The information contained herein is a review of our experience with pediatric body CT, how we use body CT in children, and its relationship to other modalities in this department. This book illustrates the CT appearances of the normal anatomy and the common as well as the rare pathological entities involving the chest, abdomen, pelvis, neck, and musculoskeletal system in children. In the Radiology Department at the Hospi tal for Sick Children in Toronto, CT studies of the head, face, and spinal cord are supervised by our pediatric neuroradiologists. These areas have thus been excluded from consideration. For a detailed account of the use of CT metrizamide myel ography in children, the reader is referred to CT and Myelography of the Spine and Cord, authored by Drs. Holger Pettersson and Derek Harwood-Nash, which deals extremely well with our departmental approach to CT ot the spine in children. However, the relationship of CT metrizamide myelography to general body CT studies is described in the present book in the sections dealing with paras pinal and vertebral lesions. Most of the illustrations are from studies performed with the General Electric 9800 (2-s scanner) and 8800 (4.8-, 5.7-, 9.6-s scanner) CT machines and thus reflect imaging with state of the art equipment. A few illustrations are from studies performed with our original Ohio Nuclear Delta 50 scanner (2-min scan time). The reason for including these old images is either that they illustrate rare conditions that we have not had the opportunity to study on our newer scanners at the Hospital for Sick Children, or because at that time CT was used more commonly to delineate certain entities that are now better delineated with other less expensive modalities. The information contained in this book will be of vital interest not only to all viii Preface pediatric radiologists, but also to adult radiologists who are involved with perform ing body CT examinations in children, as well as to pediatricians, pediatric oncolo gists and radiotherapists, pediatric general surgeons, thoracic surgeons, and orthopedic surgeons. It is hoped that the information provided will be of assistance to these groups of physicians, will help others in making accurate diagnoses, and will aid in the efficient management of pediatric patients. At the time of writing, the use of nuclear magnetic resonance scanning in children is still in its infancy. The role of nuclear magnetic resonance and its relationship to body CT in the pediatric age group have thus yet to be defined and will require continuing critical reassessment of our use of CT. It is hoped, however, that the information set forth will lay a foundation for the understanding of the cross sectional images also obtained with nuclear magnetic resonance. Acknowledgements I would like to express my gratitude to the following people: Dr. David Martin (presently at the Ottawa Children's Hospital) and Dr. Gordon Culham (presently at the Vancouver Children's Hospital), who taught me the uses and technique of body CT in children. Their hours of teaching and encouragement laid the foundations for this book. My radiological colleagues, including Drs. David Martin, Gordon Culham, Bernard Reilly, and David Stringer, who have taken part in body CT studies in the Radiology Department of the Hospital for Sick Children, Toronto, in the past and at present, for their advice and professional contributions. Dr. Derek Harwood-Nash, Radiologist-in-chief, the Hospital for Sick Children, Toronto, for his constant encouragement, advice, and enthusiasm. Dr. Charles Fitz, former Head, Division of Special Procedures, for his cooperation and advice. Dr. Helen Chan, Division of Hematology and Oncology, Department of Pediatrics, for her enthusiasm, advice, and endless hours of work in obtaining clinical infor mation on the patients reported in our previous papers and in this book. The technical and nursing staff in the Radiology Department, whose valuable expertise plays an important role in the continuing performance of high-quality body CT examinations in this institution. The secretaries, in particular Lori Fearon, Julete Harris, and Gladys Clarke for their hours toiling over the manuscript so efficiently and also more recently Karen Fennell. The photographic personnel in the Department of Visual Education, for their exper tise and cooperation. The past and present Fellows of our department who have helped in the perform ance of body CT studies and who have also taken part in the numerous projects that have been published and presented at radiological meetings, in particular Veronica Donoghue, Chris Farrelly, Peter Liu, Geoff Robey, Piyoosh Kotecha and Alan Sprigg. Lastly, and most important of all, I would like to thank my wife and daughters for still accepting me as part of the family during the preparation of this book. Ontario, February 1986 Alan Daneman Contents SECTION I: INTRODUCTION Chapter 1 General Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Factors Affecting Choice of Modality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 GeneralCon~derations ............................................ 6 Clinical and Radiological Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 References .......... .' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Chapter2 Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Prescan Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Patient Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Instructions and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Sedation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Immobilization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Environment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Contrast Administration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Scan Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Computed Radiographs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Axial Scans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Posts can Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Guidance Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Summary............................................................ 17 x Contents SECTION II: CHEST Chapter3 Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Window Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Pseudomasses and Anatomical Variations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23 Bones............... .......... .................... ..... ..... ..... 23 Vessels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Chapter4 Mediastinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Anatomical Compartments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Thymus.............................................................. 27 Trachea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Heart and Pericardium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34 Mediastinal Masses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Anterior Mediastinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36 Middle Mediastinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 42 Posterior Mediastinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Other Masses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 52 Chapter 5 Lung Parenchyma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Diffuse Parenchymal Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Mass Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Pulmonary Nodules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Appearances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 61 Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 63 Differentiation from Vessels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67 Chapter 6 Chest Wall and Pleura. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69 Superficial Soft Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 BonyThorax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Extrapleural Tissues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Pleura. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Postradiation Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 82 SECTION III: ABDOMEN Chapter7 Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Gastrointestinal Contrast Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Contents xi Intravenous Contrast Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86 Scan Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Chapter 8 Retroperitoneum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Anatomy............................................................. 89 Pathology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 LymphNodes............................................ ..... .... 95 Neoplasms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 98 Sympathetic Nervous System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 100 Soft Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 100 Blood Vessels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 103 NonpalpableTestis ................................................ 104 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 104 Chapter 9 Pancreas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107 Anatomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107 Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 109 Size ................................. ',' . . . . . . . . . . . . . . . . . . . . . . . . . .. 109 Displacements. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 112 Pathology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 112 Pancreatitis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 112 Trauma ........................................................... 112 Neoplasms ........................................................ 116 Cystic Fibrosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 118 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 120 ChapterlO Adrenals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 121 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 121 Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 121 Anatomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 122 Shape and Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 122 Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 122 Hyperplasia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 123 Pseudotumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 123 Neoplasms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 125 Medullary and Sympathetic Nervous System Lesions. . . . . . . . . . . . . . . . .. 126 Adrenocortical Neoplasms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 137 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 141 AdrenalHemorrhage .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 141 Adrenal Calcification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 141 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 141 Chapter 11 Kidneys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 145 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 145 Indications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 145 Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 146 Anatomy ............................................................. 147 Normal Variants and Congenital Anomalies. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 148 xii Contents Pathology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 148 Cysts ............................................................. 148 Renal Vein Thrombosis ............................................. 151 Attenuation Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151 Inflammation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 152 Neoplasia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 153 Trauma ........................................................... 169 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 170 Chapter12 Liver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 173 Introduction .......................................................... 173 Anatomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 173 Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 173 Attenuation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 173 Vessels ........................................................... 174 Lobes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174 Pathology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174 Diffuse Parenchymal Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174 Portal Hypertension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 179 Masses ........................................................... 180 Trauma ........................................................... 193 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 196 Chapter 13 Biliary Tract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 197 Introduction .......................................................... 197 Anatomy ............................................................. 197 Gallbladder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 197 Bile Ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 198 Pathology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 201 Gallbladder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 201 Bile Ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 203 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 207 Chapter14 Spleen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 209 Introduction .......................................................... 209 Anatomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 209 Size .................................................................. 209 Normal Variations and Congenital Anomalies. . . . . . . . . . . . . . . . . . . . . . . . . . .. 210 Shape ............................................................ 210 Position. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 212 Displacements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 214 Attenuation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 216 Pathology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 217 Neoplasms ........................................................ 217 Cysts ............................................................. 218 Trauma ........................................................... 219 Asplenia/Polysplenia Syndrome. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219