Type III choledochal cysts, also called choledochoceles, are rare cystic dilatations of the terminal biliary tree. We report the case of a 'closed choledochocele', in which the bile and ventral pancreatic ducts emptied into the cyst, but because there was no outlet into the duodenum, drainage was retrograde via the accessory duct. This type of choledochocele variant has never previously been described in the medical literature.