Experimental and numerical investigation of the mechanism of pancreaticobiliary maljunction

Pancreaticobiliary maljunction is a potential cause of biliary malignancy due to pancreatic enzyme activation from pancreatic juice reflux. Although this reflux phenomenon has been frequently observed in clinical studies, its underlying mechanism has been rarely explored. This study investigated pancreaticobiliary flow in patients with choledochal cysts (CCs) and cholangiocarcinoma, and to explore possible scenarios of how reflux occurs using computational fluid dynamics (CFD). Patient-specific models were first constructed based on two patients with CCs and one with both CCs and cholangiocarcinoma. Particle image velocimetry was used to first visualize the local velocity field and CFD simulations were then performed to visualize and analyze pancreaticobiliary flows (e.g., hepatic bile, gallbladder bile, and pancreatic juice), as well as pancreatic juice reflux. Results showed that for patients with both CCs and cholangiocarcinoma, their digestive function can be impaired compared to those with only CCs, as bile flow movement was reduced by nearly 25%. Bile flow recirculation was more likely to occur in lower region of pancreaticobiliary system in CCs patients with cholangiocarcinoma, implying an increased likelihood of pancreatic enzyme activation due to extended time needed for pancreatic juice to mix with bile in the common channel. Escalating wall shear stress was observed in patients with CCs and cholangiocarcinoma. CFD simulations demonstrated that sphincter of Oddi dysfunction during the bile refilling process can be one of reasons for inducing pancreatic juice reflux. The simulations visualized that concentration of pancreatic juice could reach between 59.2% and 83.8% in common bile duct and cystic duct.