Narrow duct segment distal to choledochal cyst.

"Narrow segments" (or stenotic portions) of the common bile duct (CBD) distal to cysts in two patients (a 50-yr-old woman and a 25-yr-old man) with choledochal cyst (CholCyst) were studied macroscopically and histologically. The narrow segments of the ducts were patent and connected with the main pancreatic duct extraduodenally, whereas the CBD in controls were neither dilated nor stenotic, and joined the main pancreatic duct within the duodenal wall. These narrow segments were 1 cm long. In case 1, a minute orifice was found in the narrow segment of the duct macroscopically and was identified microscopically as a small duct from a pancreatic lobule. In case 2, a small pancreatic duct also joined the narrow segment of the duct. These small pancreatic ducts were derived from the ventral pancreas, based on distribution of PP-islets. Therefore, the narrow duct distal to the cyst in patients with CholCyst (or congenital biliary dilatation) was considered to be a branch of the ventral pancreatic duct.