Etiology of choledochal cysts: two instructive cases.

The etiology of choledochal cysts is controversial. The authors report two cases which show that type 1 cysts (axial dilatation of the common bile duct and common hepatic duct) may be caused by a biliary web and that some choledochoceles (type 3 cyst) may actually be duodenal duplications (i.e., having an outer wall of smooth muscle lined with gastrointestinal mucosa and being adherent to the gut).