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PATHOLOGY OF THE LIVER AND PORTAL VENOUS SYSTEM 87 teristics of their adenomas, as malignant degeneration is a possible feature. Focal fatty change Focal fatty infiltration Fatty infiltration of the liver is a common occurrence which may affect the whole or part of the liver. It is associated with obesity and alcoholism, and can also occur in pregnancy, diabetes and with certain drugs. The deposition of fat confined to certain focal areas of the liver is related to the blood supply to that area. Fatty infiltration increases the reflectivity of the parenchyma, making it hyperechoic. This can simulate a focal mass, such as a metastasis. Unlike a focal lesion however, it does not display any mass effect and the course of related vessels remains constant. It has a characteristic straight-edged shape, rectangular or ovoid, corresponding to the region of local blood supply (Fig. 4.11). Foci of fatty change may be multiple or may affect isolated liver segments. The most common sites are in segment 4 around the porta, in the caudate lobe (segment 1) and in the posterior area of the left lobe (segment 3). Focal fatty sparing The reverse process may also occur, in which a diffusely fatty, hyperechogenic liver has an area which has been spared from fat deposition due to its blood supply. This area is less reflective than the surrounding liver and may mimic a hypoechoic neoplastic lesion, but as with focal fatty infiltration, it has regular outlines and shape and no mass effect. The most common sites for fatty sparing are similar to those for focal fatty infiltration; segment 4 just anterior to the portal vein (Fig. 4.11B), segment 1 (the caudate lobe) and frequently there are multiple areas throughout the liver. Unlike a true focal lesion, fatty change does not exhibit a mass effect and normal, undisplaced vasculature can be demonstrated with colour Doppler in areas both of focal fatty infiltration and fatty sparing. The administration of a contrast agent may also help to clarify the nature of the ‘mass’, as the area under consideration will behave exactly the same as the surrounding, normal liver in its uptake of the agent. A B Figure 4.11 (A) Focal fatty sparing in the left lobe. This sharply demarcated area of normal liver contrasts with the surrounding hyperechoic fatty liver. (B) Focal fatty infiltration anterior to the main portal vein, characteristically ‘square’ in shape. (Continued)
88 ABDOMINAL ULTRASOUND mass. The administration of an ultrasound contrast agent displays a characteristic ‘spoked-wheel’ pattern of arteries with a central scar. 7 The diagnosis can usually be confirmed on MRI scanning (which shows a similar vascular pattern to that of ultrasound contrast scanning) but may occasionally require biopsy proof. Management of this benign mass is usually conservative, with ultrasound follow-up, once the diagnosis has been established, but surgical resection may be necessary in larger lesions. C Figure 4.11 cont’d (C) Wedge-shaped area of fatty infiltration in the right lobe. Lipoma The hepatic lipoma is a relatively rare, benign hepatic tumour which is very similar in nature and acoustic appearance to focal fatty change. It differs in that it is a discrete tumour of fatty deposition rather than an infiltrative process and so can exert a mass effect on surrounding vessels if large. The fat content makes the lipoma hyperechoic compared to the surrounding liver tissue. Focal nodular hyperplasia This is a benign tumour made up of a proliferation of liver cells with hepatocytes, Kupffer cells and biliary and fibrous elements. It is most commonly found in young women and is usually discovered by chance, being asymptomatic. Its ultrasound characteristics vary, and it may be indistinguishable from hepatic adenoma. It tends to affect the caudate lobe and has the appearance of a homogeneous mass often of similar echogenicity to the liver (Fig. 4.12). It presents a diagnostic difficulty both with CT and ultrasound, as its characteristics can vary. 6 Colour Doppler shows an increased arterial flow in the Granuloma Granulomata are benign liver masses which are associated with chronic inflammatory liver diseases. They are particularly associated with primary biliary cirrhosis, sarcoidosis or TB. They may be multiple and small, in which case the liver often looks coarse and hyperechoic. More often they are small discrete lesions which may be hypo- or isoechoic, sometimes with a hypoechoic rim like a target, or calcified with distal shadowing (Fig. 4.13). They can undergo central necrosis. Differential diagnoses include metastases or regenerating nodules. Hepatic calcification Calcification occurs in the liver as a result of some pathological processes and may be seen following infection or parasitic infestation. It may be focal (usually the end stage of a previous abscess, haematoma or granuloma) which usually indicates that the lesion in question is no longer active. It may also be seen within some metastases. Calcification may also be linear in nature, following the course of the portal tracts. This can be associated with old TB or other previous parasitic infestations. Occasionally hepatic calcification is seen in children or in the fetus. This is usually not a significant finding but prenatal infection should be excluded with a TORCH (toxoplasmosis, rubella, cytomegalovirus and HIV) screen. Calcification, which casts a strong and definite shadow, should be distinguished from air in the biliary tree (Fig. 3.46), which casts a reverberative shadow and is
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Abdominal Ultrasound
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Abdominal Ultrasound How, Why and W
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v Contents Contributors Preface ix
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vii Contributors Rosemary Arthur FR
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ix Preface Ultrasound continues to
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ABBREVIATIONS xi MHA MHV MI MPV MRA
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Chapter 1 1 Optimizing the diagnost
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OPTIMIZING THE DIAGNOSTIC INFORMATI
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Chapter 2 17 The normal hepatobilia
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THE NORMAL HEPATOBILIARY SYSTEM 19
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Page 50 and 51: THE NORMAL HEPATOBILIARY SYSTEM 37
Page 52 and 53: THE NORMAL HEPATOBILIARY SYSTEM 39
Page 54 and 55: Chapter 3 41 Pathology of the gallb
Page 56 and 57: PATHOLOGY OF THE GALLBLADDER AND BI
Page 92 and 93: Chapter 4 79 Pathology of the liver
Page 94 and 95: PATHOLOGY OF THE LIVER AND PORTAL V
Page 134 and 135: Chapter 5 121 The pancreas CHAPTER
Page 136 and 137: THE PANCREAS 123 the patient’s le
Page 138 and 139: THE PANCREAS 125 Acute pancreatitis
Page 140 and 141: THE PANCREAS 127 E F G Figure 5.3 c
Page 142 and 143: A C DISTANCE = 3.43 CM 5%. 13 Over
Page 144 and 145: THE PANCREAS 131 G H I Figure 5.5 c
Page 146 and 147: THE PANCREAS 133 head of pancreas.
Page 148 and 149: THE PANCREAS 135 pancreatic juice i
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Chapter 6 137 The spleen and lympha
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THE SPLEEN AND LYMPHATIC SYSTEM 139
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Chapter 7 153 The renal tract CHAPT
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THE RENAL TRACT 155 As with any oth
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THE RENAL TRACT 157 A B q 0 LRA AO
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THE RENAL TRACT 159 junctions of or
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THE RENAL TRACT 161 A B Figure 7.5
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THE RENAL TRACT 163 carcinomas, the
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THE RENAL TRACT 165 the vesicourete
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THE RENAL TRACT 167 Table 7.1 Sourc
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THE RENAL TRACT 169 A B Figure 7.13
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THE RENAL TRACT 171 Table 7.2 Diffe
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THE RENAL TRACT 173 Ultrasound stil
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THE RENAL TRACT 175 CT is useful fo
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THE RENAL TRACT 177 Xanthogranuloma
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THE RENAL TRACT 179 As with acute t
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THE RENAL TRACT 181 der with increa
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THE RENAL TRACT 183 ● ● Morphol
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THE RENAL TRACT 185 ● ● hydrone
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THE RENAL TRACT 187 A Figure 7.27 A
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THE RENAL TRACT 189 vascular reject
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THE RENAL TRACT 191 B A C Figure 7.
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THE RENAL TRACT 193 computerised ul
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Chapter 8 195 The retroperitoneum a
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THE RETROPERITONEUM AND GASTROINTES
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Chapter 9 215 The paediatric abdome
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THE PAEDIATRIC ABDOMEN 217 A B SPLE
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THE PAEDIATRIC ABDOMEN 219 B A B Fi
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THE PAEDIATRIC ABDOMEN 221 probe de
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THE PAEDIATRIC ABDOMEN 223 When the
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THE PAEDIATRIC ABDOMEN 225 + 78 A 2
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THE PAEDIATRIC ABDOMEN 227 A B C D
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THE PAEDIATRIC ABDOMEN 229 Table 9.
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THE PAEDIATRIC ABDOMEN 231 A LT B C
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THE PAEDIATRIC ABDOMEN 237 mesenter
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THE PAEDIATRIC ABDOMEN 239 E F G Fi
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THE PAEDIATRIC ABDOMEN 241 system i
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Chapter 10 The acute abdomen 243 CH
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THE ACUTE ABDOMEN 245 scan of the p
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THE ACUTE ABDOMEN 247 LIVER LS GB S
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THE ACUTE ABDOMEN 249 D A RT B C E
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THE ACUTE ABDOMEN 251 17. Patlas M,
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Chapter 11 253 Interventional and o
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INTERVENTIONAL AND OTHER TECHNIQUES
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275 Bibliography and further readin
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277 Index A Abdomen, acute gastroin
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INDEX 279 Continuous ambulatory per
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INDEX 281 Intravenous urography (IV
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INDEX 283 Phrygian cap, 29 Pneumobi
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