ULTRASOUND IMAGES 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.

Ultrasound images Acute pancreatitis.

Clinical features Acute inflammation of the pancreas has a number of possible causes (Table A ), but is most commonly associated with gallstones or alcoholism. Clinically it presents with severe epigastric pain, abdominal distension and nausea or vomiting. In milder cases, the patient may recover spontaneously. If allowed to progress untreated, peritonitis and other complications may occur. Biochemically, raised levels of amylase and lipase (the pancreatic enzymes responsible for the digestion of starch and lipids) are present in the blood and urine. Acute inflammation causes the pancreatic tissue to become necrosed, releasing the pancreatic enzymes which can further destroy the pancreatic tissue and also the capillary walls, entering the blood stream.

Ultrasound images pancreatitis

Mild acute pancreatitis may have no demonstrable features on ultrasound, especially if the scan is performed after the acute episode has settled. In more severe cases the pancreas is enlarged and hypoechoic due to oedema. The main duct may be dilated or prominent. As the condition progresses, digestive enzymes leak out, forming collections or pseudocysts. These are most frequently found in the lesser sac, near the tail of the pancreas, but can occur anywhere in the abdomen—within the pancreatic tissue itself, anywhere in the peritoneal or retroperitoneal space or even tracking up the fissures into the liver—so a full abdominal ultrasound survey is essential on each attendance (Fig. below). Pseudocysts are so called because they do not have a capsule of epithelium like most cysts, but are merely collections of fluid surrounded by adjacent tissues. A pseudocyst may appear to have a capsule on ultrasound if it lies within a fold of peritoneum. Pseudocysts may be echo-free, but generally contain echoes from tissue debris and may be loculated. In a small percentage of cases, a pseudocyst or necrotic area of pancreatic tissue may become infected, forming a pancreatic abscess. Although acute pancreatitis usually affects the entire organ, it may occur focally. This presents a  diagnostic dilemma for ultrasound, as the appearances are indistinguishable from tumour. The clinical history may help to differentiate; suspicion of focal pancreatitis should be raised in patients with previous history of chronic pancreatitis, a history of alcoholism and normal CA 19–9 levels (a tumour marker for pancreatic carcinoma). The enlargement of the pancreas in acute pancreatitis may have other consequences, for example the enlarged pancreatic head may obstruct the common bile duct, causing biliary dilatation. Doppler ultrasound is useful in assessing associated vascular complications. Prolonged and repeated attacks of acute pancreatitis may cause the splenic vein to become encased and compressed, causing splenic and/or portal vein thrombosis, with all its attendant sequelae (Fig.below). Although ultrasound is used to assess the pancreas in cases of suspected acute pancreatitis, its main role is in demonstrating the cause of the pancreatitis, for example biliary calculi, in order to plan further management. The ultrasound finding of microlithiasis or sludge in the gallbladder is highly significant in cases of suspected pancreatitis, and has been implicated in the cause of recurrent pancreatitis.

Ultrasound images Acute pancreatitis in a patient with alcoholic liver disease. The pancreas is hypoechoic and bulky with a lobulated outline.

Ultrasound images Large pseudocyst near the tail of the pancreas in acute pancreatitis

Ultrasound images Necrotic tail of pancreas surrounded by exudate.

Ultrasound images Inflammatory exudate is seen around the right kidney in acute pancreatitis Table A Causes of acute pancreatitis Biliary calculi—most common cause. Obstructs the main pancreatic duct/papilla of Vater and may cause reflux of bile into the pancreatic duct. Alcoholism—alcohol overstimulates pancreatic secretions causing overproduction of enzymes Trauma/iatrogenic—damage/disruption of the pancreatic tissue, e.g. in a road traffic accident, or by surgery, biopsy or ESWL Drug-induced—a relatively uncommon cause. Some anticancer drugs can cause chemical injury . Infection—e.g. mumps. A rare cause of pancreatitis Congenital anomaly—duodenal diverticulum, duodenal duplication, sphincter of Oddi stenosis or choledochal cyst may obstruct the pancreatic duct, giving rise to pancreatitis Hereditary—a rare, autosomal dominant condition presenting with recurrent attacks in childhood or early adulthood. ESWL = extracorporeal shock wave lithotripsy.

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