Unusual presentation of an unusual type of choledochal cyst.

Type II choledochal cysts are rare congenital malformations of the biliary ductal system. We report a case in which a type II choledochal cyst presented as a mass in the porta hepatis without any demonstrable connection with the biliary tree. In the English literature, this is the first described case of this type in the absence of biliary tract malignancy. We hypothesize that the connection to the biliary tree was lost by either torsion of the cyst or fibrosis due to chronic inflammation.