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THE PANCREAS 123 the patient’s left. The spleen also makes a good window to the tail in coronal section. If you can’t see the pancreatic head properly, turn the patient left side raised, which moves the duodenal gas up towards the tail of the pancreas. Right side raised may demonstrate the tail better. If these manoeuvres still fail to demonstrate the organ fully, try: —asking the patient to perform the Valsalva manoeuvre with abdominal protrusion —scanning the patient erect —filling the stomach with a water load to create an acoustic window through which the pancreas can be seen. Ultrasound appearances The texture of the pancreas is rather coarser than that of the liver. The echogenicity of the normal pancreas alters according to age. In a child or young person it may be quite bulky and relatively hypoechoic when compared to the liver. In adulthood, the pancreas is hyperechoic compared to normal liver, becoming increasingly so in the elderly, and tending to atrophy (Fig. 5.2). The pancreas does not have a capsule and its margins can appear rather ill-defined, becoming infiltrated with fat in later life. These age-related changes are highly significant to the sonographer; what may be considered normal in an elderly person would be abnormally hyperechoic in a younger one, and may represent a chronic inflammatory state. Conversely a hypoechoic pancreas in an older patient may represent acute inflammation, whereas the appearances would be normal in a young person. The main pancreatic duct can usually be visualized in the body of pancreas, where its walls are perpendicular to the beam. The normal diameter is 2 mm or less. The common bile duct can be seen in the lateral portion of the head and the gastroduodenal artery lies anterolaterally. The size of the uncinate process varies. Pitfalls in scanning the pancreas The normal stomach or duodenum can mimic pancreatic pathology if the patient is insufficiently fasted. A fluid-filled stomach can be particularly difficult when looking for pancreatic pseudocysts in patients with acute pancreatitis. Giving the patient a drink of water usually differentiates the gastrointestinal tract from a collection. Epigastric or portal lymphadenopathy may also mimic a pancreatic mass. If careful scanning and appropriate patient positioning are unable to elucidate, CT is normally the next step. Biochemical analysis In many pancreatic diseases, the production of the digestive pancreatic enzymes is compromised, either by obstruction of the duct draining the pancreas or by destruction of the pancreatic cells which produce the enzymes. This can result in malabsorption of food and/or diarrhoea. The pancreas produces digestive enzymes, amylase, lipase and peptidase, which occur in trace amounts in the blood. If the pancreas is damaged or inflamed, the resulting release of enzymes into the blood stream causes an increase in the serum amylase and lipase levels. The enzymes also pass from the blood stream into the urine and therefore urinalysis can also contribute to the diagnosis. Congenital anomalies of the pancreas The normal pancreas is the result of the fusion of two embryonic buds: the ventral bud arises from the CBD, forming the uncinate process and part of the head, and the dorsal arises from the posterior wall of the duodenum. Developmental anomalies of the pancreas occur as a result of a failure of the dorsal and ventral pancreatic ducts to fuse, that is pancreas divisum. This arrangement may cause inadequate drainage of the pancreatic duct, leading to pancreatitis. A rare developmental anomaly of the ventral bud may occur, pancreas annulare, in which pancreatic tissue encircles the bowel. In this latter case, patients can present with proximal small-bowel obstruction in infancy, but this may also be an incidental finding at autopsy. These relatively uncommon anomalies cannot usually be diagnosed on ultrasound. Increasingly, magnetic resonance cholangiopancreatography (MRCP) is replacing ERCP in the
124 ABDOMINAL ULTRASOUND A B C Figure 5.2 (A) Pancreas in a young person, demonstrating normal hypoechogenicity. (B) The normal adult pancreas is slightly more echogenic than the liver. (C) The pancreas becomes hyperechoic in an older patient. evaluation of the pancreas and ductal system, due to its relative non-invasive nature and low risk compared with ERCP. 1, 2 Agenesis of the pancreas is very rare, usually in association with other defects, and children usually die soon after birth. PANCREATITIS Inflammation of the pancreas may be acute or chronic and is usually a response to the destruction of pancreatic tissue by its own digestive enzymes (autodigestion), which have been released from damaged pancreatic cells.
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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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Chapter 3 41 Pathology of the gallb
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PATHOLOGY OF THE GALLBLADDER AND BI
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Page 86 and 87: 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 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
Page 150 and 151: Chapter 6 137 The spleen and lympha
Page 152 and 153: THE SPLEEN AND LYMPHATIC SYSTEM 139
Page 166 and 167: Chapter 7 153 The renal tract CHAPT
Page 168 and 169: THE RENAL TRACT 155 As with any oth
Page 170 and 171: THE RENAL TRACT 157 A B q 0 LRA AO
Page 172 and 173: THE RENAL TRACT 159 junctions of or
Page 174 and 175: THE RENAL TRACT 161 A B Figure 7.5
Page 176 and 177: THE RENAL TRACT 163 carcinomas, the
Page 178 and 179: THE RENAL TRACT 165 the vesicourete
Page 180 and 181: THE RENAL TRACT 167 Table 7.1 Sourc
Page 182 and 183: THE RENAL TRACT 169 A B Figure 7.13
Page 184 and 185: 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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