Mucosal cell proliferation activity of the gallbladder in children with anomalous arrangement of the pancreaticobiliary duct.

Anomalous arrangement of the pancreaticobiliary duct (AAPBD) is an anatomical maljunction of the bile duct and the pancreatic duct that is frequently associated with gallbladder carcinoma. In patients with AAPBD, it has been postulated that pancreatic juice regurgitates into the biliary tree, and the mixture of refluxed pancreatic juice and stagnant bile juice acts as an irritant factor to the biliary tract epithelium, leading to chronic inflammation and metaplasia. Eventually these mucosal changes may progress to invasive carcinoma. We reviewed clinicopathologic studies on epithelial changes of the gallbladder in patients with AAPBD to clarify the implications relevant to carcinogenesis. Conventional histological studies have shown that the most characteristic change observed in the gallbladder of children with this anomaly was epithelial hyperplasia. Furthermore, the incidence of mucosal hyperplasia was significantly increased in the gallbladder of children in whom the pancreatic duct joined the common bile duct (P-C type) compared with the incidence in children in whom the common bile duct joined the pancreatic duct (C-P type). In addition, cell kinetic studies have demonstrated increased cellular proliferative activity of the gallbladder in children with AAPBD. Cell proliferative activity was significantly elevated in children with the P-C type of AAPBD compared with that in children with the C-P type of anomaly. In conclusion, AAPBD may yield increased cell proliferation in the gallbladder of patients with this anomaly in early childhood, resulting in epithelial hyperplasia. Although it remains unknown which agents are responsible for promoting the activation of cellular function, it seems that bile acids and refluxed pancreatic proteases are likely play a role in such promotion. Further investigations are needed to elucidate the mechanism of increased cellular function.