Advanced Imaging of the Abdomen

Advanced Imaging of the Abdomen

Jovitas Skucas

Advanced Imaging of the Abdomen

With 489 Figures in 1025 Parts

Jovitas Skucas, MD

Professor Emeritus, Department of Imaging Sciences, University of Rochester, Rochester, NY, USA

British Cataloging in Publication Data

A catalogue record for this book is available from the British Library.

Library of Congress Control Number 2005924309 ISBN-10: 1-85233-992-6 e-ISBN 1-84628-169-5 ISBN-13: 978-1-85233-992-0

Printed on acid-free paper.

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Preface

This book is an attempt to bridge the interface between referring clinicians and radiol- ogists when faced with a patient suspected of having a complex or unusual abdominal condition. The emphasis is on the choice of imaging procedures, expected diagnostic yield, a discussion of pertinent imaging findings, and the possible differential diagno- sis. The rapid proliferation of imaging techniques provides a bewildering array of choices to the referring physician. Thus when faced with a suspected biliary abnormality, should one suggest traditional endoscopic retrograde cholangiography, or is noninva- sive and noncontrast magnetic resonance (MR) cholangiography or even contrast-aided computed tomography (CT) cholangiography more appropriate? What is the role of CT virtual colonoscopy? Is it limited to colon cancer screening or does it have a role in cancer staging?

This book discusses imaging topics of those structures that fall in the purview of the gastroenterologist, urologist, general surgeon, and related specialist. The anatomic limits of the abdomen are somewhat stretched to include the esophagus superiorly, and the aorta, inferior vena cava, and adjacent structures posteriorly. The emphasis is on new imaging findings and innovations. This book also discusses the clinical aspects of a disease needed to formulate a rational diagnostic approach, but basic research, results of animal studies, and imaging research are not discussed as they are not pertinent to clinical medicine. Because of space limitations, fetal imaging and choosing a contrast agent are not discussed. Also, laboratory findings and therapeutic options are not dis- cussed, except for those having a bearing on subsequent diagnostic studies.

This book is intended to be used as a reference for the atypical and unique presenta- tion and newer diagnostic imaging modalities. Publications of unusual clinical and imaging finding are accentuated, and common imaging studies of common disorders are only mentioned in passing, if they are applicable.

Traditionally, radiology texts have used a pathologically oriented outline. Subse- quently it became the custom to discuss disorders from an imaging point of view. An attempt is made here to integrate clinical presentation with pertinent radiologic findings.

The material is organized primarily along anatomic organ systems, with some excep-

tions. For instance, disorders of the adnexa involve the peritoneal cavity, but they are

closely related to the female genital tract and thus are included in Chapter 12, Female

Reproductive Organs, rather than the peritoneum chapter. Within each organ system the

material is subdivided further along broad disorder categories, such as congenital,

inflammation, tumors, etc., but a pragmatic clinical approach is adopted. For example, a

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PREFACE

history of trauma is usually known and thus imaging findings associated with acute trauma are discussed in separate sections.

It has been said that “to steal from one author is plagiarism, if you steal from many, it’s research” (1). With that definition in mind, this work, I hope, is research. The refer- ences are rather wide-ranging, but to make the text more readable the number of refer- ences is deliberately kept low and information that has diffused in the medical community is not referenced further. The cited references serve both as an acknowl- edgment to the original authors and as a guide to a more in-depth source on a particu- lar topic.

An abbreviated format has been adopted in presenting published studies. Emphasis is on sensitivity and specificity (or false-positive rate), realizing that these provide an incomplete picture. Where applicable, the measurements given include a standard devi- ation. To maintain brevity, little additional statistical analysis is provided.

It is assumed that the reader has basic knowledge of abdominal imaging. The techni- cal details about performing and interpreting various imaging modalities are omitted except when pertinent to new techniques and applications. Thus a statement such as

Tc99m-DTPA scintigraphy and color duplex US . . . could reliably differentiate minimal and not perfused renal allografts . . .

omits that scintigraphy consisted of analogue scans up to 60 minutes postinjection and that time-activity curves over the first 60 seconds after injection of 370 to 440 MBq of technetium-99m-diethylenetriaminepentaacetic acid are obtained and classified by a perfusion score, the time between renal and iliac artery peaks and washout of the renogram curve; similarly, not mentioned is that color duplex ultrasonography (US) con- sists of a perfusion study in all sections of the graft and vascular anastomoses by color- coded duplex sonography and that maximal blood flow velocity and resistive index in the renal artery are determined by a pulsed Doppler device. Most of these details are intuitive to the specialist performing such a test.

To avoid repetition, the more common imaging findings are not repeated for each imaging modality. Thus if a lesion contains fat, it is stated as such; it is not stated that this fat is hypodense with CT, hyperechoic with US, or hyperintense with T1-weighted MR sequences. The exception is if a specific imaging appearance is unique.

Indications for magnetic resonance imaging (MRI) are still evolving. In addition, as new imaging technology becomes available the imaging modality recommended for a particular application today may not be optimal tomorrow. Thus multislice helical CT techniques continue to expand application of CT angiography and interventional pro- cedures, possibly at the expense of further rapid growth of MRI.

Numerous individuals contributed images to this book and their effort is gratefully acknowledged. Over the years many ex-residents have provided me with interesting studies from their daily practices and these are acknowledged. A special thanks goes to Jolanta Galdikaite, an illustrator in Kaunas, Lithuania, for the line drawings.

Jovitas Skucas, MD

Reference

1. Attributed to the Hollywood ne’er-do-well Wilson Mizner (1876–1933). Quoted in Green J. Chasing the Sun:

Dictionary Makers and the Dictionaries They Make. New York: Henry Holt, 1996:19.

Contents

PART I: DIGESTIVE SYSTEM . . . . 1

1. Esophagus . . . . 3

2. Stomach . . . . 55

3. Duodenum . . . . 107

4. Jejunum and Ileum . . . . 125

5. Colon and Rectum . . . . 185

6. Appendix . . . . 279

7. Liver . . . . 293

8. Gallbladder and Bile Ducts . . . . 419

9. Pancreas . . . . 501

PART II: GENITOURINARY SYSTEM . . . . 569

10. Kidneys and Ureters . . . . 571

11. Bladder . . . . 685

12. Female Reproductive Organs . . . . 719

13. Male Reproductive Organs . . . . 801

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CONTENTS

PART III: OTHER STRUCTURES . . . . 863

14. Peritoneum, Mesentery, and Extraperitoneal Soft Tissues . . . . 865

15. Spleen . . . . 933

16. Adrenals . . . . 953

17. Abdominal Vasculature . . . . 975

Index . . . 1047

Terminology

The term tumor is used in a broad sense for a focal growth, be it inflammatory, devel- opmental, or neoplastic in nature. In solid organ chapters tumor is used synonymously with nodule.

A number of terms are in general use to describe computed tomography (CT), ultra- sonography (US), and magnetic resonance (MR) imaging findings. Although the syn- onyms listed are self-evident to radiologists, they tend to be confusing to clinicians. For consistency, the following terminology is adopted:

Adopted Terms

Synonyms CT

:

Hypodense Hypoattenuating, low attenuation, low opacity Isodense Isoattenuating

Hyperdense Hyperattenuating, high attenuation, high opacity US:

Hypoechoic Hypogenic, hypoechogenic, echopenic, sonolucent

Isoechoic Isogenic

Hyperechoic Hypergenic, echogenic MR

:

Hypointense Low signal intensity

Isointense Intermediate signal intensity Hyperintense High signal intensity

1Density, echogenicity, and intensity are usually expressed in reference to an assumed internal standard, gen- erally normal adjacent tissue parenchyma.

2CT and MR precontrast and postcontrast appearances of a lesion varies. Also, the early postcontrast appear- ance (arterial phase) often differs from that seen on delayed images (venous phase or even later).

3MR findings vary depending whether T1- or T2-weighted sequences are imaged and on imaging parameters used. To avoid confusion, these MR terms are applied only to precontrast images. The terms hypo- and hyper- vascular are used to describe tissue appearance after intravenous contrast injection. The term contrast agent has a different meaning in MR than usually applied to barium sulfate or the iodinated agents used in angio- graphy and CT. MR contrast agents are not visualized directly; rather, their usefulness is based on their ability to change water proton relaxation times.

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