Type VI biliary cyst: report of a case.

An isolated cyst of the cystic duct is an extremely rare lesion. Only single case reports are documented in the literature. The most accepted classification system of biliary cysts, the Todani classification, does not include this lesion. We report a case of isolated cyst of the cystic duct. The initial referral was for evaluation of a gallbladder mass discovered during evaluation of abdominal pain. Preoperative diagnosis was challenging as multiple imaging studies were unable to differentiate this lesion from a choledochal cyst. Surgical planning thus included cyst excision and biliary reconstruction. Operative exploration revealed a type VI biliary cyst and cholecystectomy with cystic duct ligation near the common bile duct was curative.