Morphological changes in the biliary mucosa in pediatric patients with congenital biliary dilatation are more influenced by the duration of amylase exposure than by amylase levels in the gallbladder.

Purpose: We investigated the relationship between bile amylase (AMY) levels and biliary epithelial changes in pancreaticobiliary maljunction (PBM), a congenital anomaly characterized by pancreaticobiliary reflux due to duct fusion outside the duodenal wall.

Methods: We enrolled 43 children with congenital biliary dilatation (CBD) of Todani types Ia, Ic, and IVa who underwent surgery at the Hokkaido Medical Center for Child Health and Rehabilitation between November 2007 and June 2023. We defined total AMY exposure in bile as bile AMY levels multiplied by the patient's age (months), representing amount of estimated AMY exposure until surgery. We retrospectively investigated the relationships between bile AMY levels and clinicopathological findings.

Results: All patients exhibited hyperplasia in the gallbladder and bile duct epithelium, with dysplasia observed in 13 cases, but no carcinoma. Exposure to bile AMY ≥ 662,400 IU/L × months was an independent risk factor for dysplasia.

Conclusion: The amount of estimated AMY exposure in bile rather than AMY levels in the bile is an independent risk factor for dysplasia in the biliary mucosa.