Abstracts
1997 Digestive Disease Week

Control of unidirectional flow across the sphincter of Oddi in opossums: evidence against biliary-pancreatic reflux.

NS Runkel, HJ Buhr, FG Moody. Departments of Surgery, Benjamin Franklin Medical Center, Free University of Berlin, Germany, and The University of Texas Medical School, Houston, TX.

Biliary-pancreatic reflux is regarded as an important mechanism for the development of necrotizing pancreatitis (Opie's theory), however, this hypothesis has not been proven in the laboratory. This study examines systematically fluid movements across the sphincter of Oddi (SO) in the opossum in-vivo. This animal model has the advantage of an extraduodenal SO with a long common channel. Furthermore, necrotizing pancreatitis can be induced by SO ligation. Methods: The pancreatic duct (PD) and the common bile duct (CBD) were cannulated (pentobarbital anesthesia) and connected to a "propulsion evaluation system" which measured duct pressures (cmH20) and fluid movements simultaneously. Electromyography of the SO (proximal, middle, distal) was also recorded and remained stable throughout the experiments. Results: Patent common channel (n=12): Saline perfusion of either the CBD and PD (0.03ml/min each) resulted in pressures of 18±8.2 in CBD and 18.4±11.9 in PD, respectively. Stepwise increase in perfusion volumes to 0.3 ml/min induced a rise in pressures to 43.7±8.1 (CBD) and 42.8±11.6 (PD), respectively. Pressure in the unperfused ducts remained unchanged when the alternate duct was perfused. Acute common channel obstruction (n=12): Pressures of 50 in PD and < 20 in CBD resulted in fluid movements from the PD to the CBD in all animals until pressure equalled. Fluid failed to move when pressures were set at <20 in PD and 50 in CBD in 10 animals. Fluid movements (reflux) were observed in only 2 animals. Chronic (48 h) common channel o struction): Increase in PD pressure to 50 with the CBD pressure set at <20 was followed by reflux into the CBD in all 6 animals until pressure equallized. The increase in CBD pressure to 50 with a PD pressure <20 resulted in reflux into the PD in only 1 of 6 animals. Conclusions: The SO regulates the direction of movements of fluid along the commmon channel. Acute and chronic common channel obstruction allows free flux from the PD into the CBD but fluid movements in the PD remain unidirectional thus preventing reflux into the pancreas. Opie's hypothesis is questioned in the opossum model.