Background. A reflux of pancreatic juice into the biliary tract caused by pancreaticobiliary maljunction (PBM) has been considered important in the development of biliary tract carcinogenesis in choledochal cysts. We excised extrahepatic bile ducts in patients with choledochal cysts to terminate the reflux of pancreatic juice. We investigated whether this surgery could stop the development of the residual bile duct carcinoma. Methods. Fifty-six patients with a diagnosis of PBM with choledochal dilatation underwent surgical excision of extrahepatic bile ducts. We applied a person-year method to compare the relative risks (observed number/expected number) of biliary tract carcinoma before and after surgery. Results. In 3 patients, bile duct carcinoma developed in residual dilated segments 19 years 6 months, 8 years 8 months, and 2 years 5 months, respectively, after surgery. Although the relative risk in the post-surgery group was slightly decreased by surgery, it was still high compared with that of the general population. Conclusions. The incidence of bile duct carcinoma is still high, even after excision of extrahepatic bile ducts in PBM patients with choledochal dilatation. For these patients, careful long-term follow-up is necessary, especially after operations that leave the dilated bile ducts, such as cases of Todani's type IV-A.
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