Biliary cysts are rare and have an incidence of 1 in 100 000 in the Western world, although rates are higher in Asian populations with incidence as high as 1 in 1000 in specific populations. Almost two-thirds of cases are seen in Japan.
The majority of patients will present in childhood, before the age of 10 years. Choledochal cysts are more common in women (male:female ratio of approximately 3-4:1). They are associated with a variety of developmental anomalies, primarily abnormalities in the pancreaticobiliary junction or biliary, duodenal, or colonic atresia.
Common findings include a palpable abdominal mass, right upper quadrant abdominal pain, and jaundice. In many instances, choledochal cysts are asymptomatic. Approximately half of choledochal cysts are diagnosed before the patient is 10 years old, although they can be diagnosed at any age.
There are several types of biliary cysts, termed for their location and appearance.
Type I (50%-85% of cysts) – Segmental dilation of the extrahepatic bile duct.
- Ia – cystic dilation of entire extrahepatic biliary tree sparing the intrahepatic tree
- Ib – focal segmental dilation of the extrahepatic bile duct
- Ic – smooth fusiform dilation of the entire extrahepatic bile duct
Type III – Extrahepatic bile duct dilation within the duodenal wall.
Type IV – Intrahepatic and extrahepatic duct cysts.
Type V – Intrahepatic dilation and cysts (Caroli disease).
Some cysts are benign, while others portend an increased malignant potential, particularly for cholangiocarcinoma. Cancer risk is highest in older patients with choledochal cysts and in type I and type IV cysts, but all types of choledochal cysts have been associated with malignancy. Cysts can also predispose patients to obstructive stones, cholangitis, bleeding, biliary perforation, volvulus, and intussusception.
Biliary cysts often go unrecognized unless symptomatic.