A congenital anatomic malformation of a bile duct, including cystic dilatation of the extrahepatic bile duct or the large intrahepatic bile duct. Classification is based on the site and type of dilatation. Type I is most common.

A rare biliary tract disease characterized by congenital fusiform or cystic dilatation of intra- and/or extrahepatic bile ducts. Females are much more often affected than males. Clinical signs and symptoms include abdominal pain, jaundice, presence of a palpable abdominal mass, nausea, vomiting, or fever. Depending on the age of the patient, the condition may be complicated by stone formation, hepatomegaly, rupture with subsequent bile peritonitis, cholangitis, cholecystitis, biliary strictures, pancreatitis, or secondary biliary cirrhosis. The risk of malignancy, particularly cholangiocarcinoma, is significantly increased.

Cystic dilatation of the hepatic duct or bile duct.

Choledochal cysts are congenital bile duct anomalies. These cystic dilatations of the biliary tree can involve the extrahepatic biliary radicles, the intrahepatic biliary radicles, or both.