Santorini's duct - Risk factor for acute pancreatitis or protective morphologic variant? Experiments in rabbits

Background and aims: Gallstone pancreatitis is assumed to result from stone passage through the choledochoduodenal junction. Stone impactions may either result in the obstruction of the pancreatic duct or occur below the confluence of the biliary tract and the pancreatic duct and, thus, may favour bile reflux into the pancreatic duel. We studied effects of a patent Santorini's duct upon secretory flow and pancreas morphology under both conditions. Methods: A catheter in the distal rabbit pancreatic duct created a second outlet for pancreatic juice and, thus, mimicked a patent Santorini's duct. A second catheter was introduced into the proximal pancreatic duct and into the common bile duct. This catheter mimicked a common channel behind a papillary obstruction. Clamping of this catheter mimicked a stone obstruction of the pancreatic duct. A catheter in the cystic duct allowed for the infection of bile with 10(7) Escherichia coli bacteria/ml. The flow direction of bile and pancreatic juice was directly observed. Pancreatic histology was analysed after 24h. Results: Pancreatic duct obstruction produced an oedema of the gland. Creation of a patent Santorini's duct prevented development of the histological changes caused by pancreatic duct obstruction. In rabbits in which a common channel obstruction was mimicked, Santorini's duct produced flow of bile along the pancreatic duct system. Flow of sterile bile along the duct did not cause pancreatic inflammatory lesions. Bile that was infected with E. coli bacteria produced an acute interstitial-oedematous pancreatitis. Conclusions: (1) A patent Santorini's duct protects the gland from the effects of main pancreatic duct obstruction; (2) Santorini's duct promotes biliary pancreatic reflux during obstruction of the common channel and subsequent development of pancreatitis caused by infected choledochal secretions; (3) Santorini's duct may thus be both a protective morphological variant and a risk factor for pancreatitis dependent upon the site of stone impaction within the choledochoduodenal junction.