Identification of risk factors for acute pancreatitis from routine radiological investigation of the biliary tract.

The size and shape of gallstones, the diameter of the common bile duct and the presence of reflux into the pancreatic duct were studied by examining routine contrast investigations of the biliary tract in 174 patients with gallstones. Patients were divided into two groups: 69 who had been admitted to hospital with an attack of acute pancreatitis (group 1) and 105 patients with gallstones who had not had a known attack of pancreatitis (group 2). Four or more gallstones were present in 38 (78 per cent) of 49 visualized gallbladders in group 1 compared with 45 (52 per cent) of 87 in group 2 (P less than 0.005). The smallest gallbladder stone was less than 4 mm in diameter in 69 per cent of group 1 and 44 per cent of group 2 gallbladders (P less than 0.005). Twenty-nine per cent of gallbladder stones in group 1 were clearly faceted compared with 20 per cent in group 2. There were no significant differences in the diameter of the common bile duct or the presence of stones in the common bile duct, although the latter were more common in group 1. Reflux of contrast into the pancreatic duct (on operative or T tube cholangiogram) was more common in group 1 (50 per cent) than group 2 (25 per cent) (P less than 0.025). This study supports the role of numerous small stones and a 'common channel' at the ampulla as aetiological factors in patients who develop acute pancreatitis as a complication of gallstones.