Increased secondary bile acids in a choledochal cyst. Possible role in biliary metaplasia and carcinoma

Choledochal cysts are uncommon congenital or acquired lesions of the biliary tree. The incidence of biliary tract carcinoma in patients with choledochal cysts is 5-35 times greater than that of the general population. Factors responsible for the increased risk of carcinoma are unknown. The case of a young woman who underwent excision of a choledochal cyst 16 years after initial diagnosis and treatment by choledochocystduodenostomy is reported. Metaplasia of the epithelial lining of the cyst was found in the resected specimen. The relative composition of bile acids in cyst contents was as follows: lithocholate, 2%; deoxycholate, 88%; chenodeoxycholate, 5%; and cholate, 5%. Virtually all bile acids were recovered in unconjugated form. In contrast, the bile acid composition of hepatic bile was as follows: lithocholate, 0%; deoxycholate, 34%; chenodeoxycholate, 43%; and cholate, 23%. Bile acids were fully conjugated. These data suggest that stasis of bile within choledochal cysts contributes to bacterial overgrowth and generation of unconjugated secondary bile acids.