CHOLEDOCHAL CYSTS CHOLANGITIS

Choledochal cysts :
Most commonly found in children, this is associated with biliary atresia, in which the distal ‘blind’ end of the duct dilates into a rounded, cystic mass in response to raised intrahepatic pressure. Choledochal cysts in adults are rare, and tend to be asymptomatic unless associated with stones or other biliary disease. They are sometimes associated with an anomalous insertion of the CBD into the pancreatic duct. The mechanism of the subsequent choledochal cyst formation is unclear, but it is thought that the common channel, which drains into the duodenum, is prone to reflux of pancreatic enzymes into the biliary duct. This can cause a biliary stricture, with subsequent proximal dilatation of the duct, forming a choledochal cyst. Less commonly the dilatation is due to a nonobstructive cause in which the biliary ducts themselves become ectatic and can form diverticula. This may be due to a focal stricture of the duct which causes reflux and a localized enlargement of the duct proximal to the stricture. Complications of choledochal cysts include cholangitis, formation of stones and progression of the condition to secondary biliary cirrhosis, which may be associated with portal hypertension. It may be difficult to differentiate a choledochal cyst, particularly if solitary, from other causes of hepatic cysts. The connection between the choledochal cyst and the adjacent biliary duct may be demonstrated with careful scanning.

Cholangitis :
Cholangitis is an inflammation of the biliary ducts, most commonly secondary to obstruction. It is rarely possible to distinguish cholangitis from simple duct dilatation on ultrasound, although in severe cases the ductal walls appear irregular and debris can be seen in the larger ducts. The walls of the ducts may appear thickened. Care should be taken to differentiate this appearance from tumour invasion and further imaging is often necessary to exclude malignancy. Bacterial cholangitis is the most common form, due to bacterial infection which ascends the biliary tree. Bacterial cholangitis is also associated with biliary enteric anastomoses. It may be complicated by abscesses if the infection is progressive and untreated. Small abscesses may be difficult to diagnose on ultrasound, as they are frequently isoechoic and ill-defined in the early stages and biliary dilatation makes evaluation of the hepatic parenchyma notoriously difficult. Contrast CT will often identify small abscesses not visible on ultrasound, and MRCP or ERCP demonstrates mural changes in the ducts.

Other forms of cholangitis include:
● Primary sclerosing cholangitis, a chronic, progressive cholestatic disease, which exhibits ductal thickening, focal dilatation and strictures.

● AIDS-related cholangitis which causes changes similar to that of primary sclerosing cholangitis.

● Recurrent pyogenic cholangitis (Oriental cholangiohepatitis) which is endemic in Southeast Asia and is associated with parasites and malnutrition. Intrahepatic biliary stones are also a feature of this condition.