Gallstones, the choledochoduodenal junction and initiation of acute pancreatitis: are two stones the culprits rather than one stone?

Reflux of biliary secretions into the pancreatic duct following gallstone obstruction of the common biliary pancreatic ampulla has been implicated as a cause of acute pancreatitis. However, the pancreatic duct pressure is higher than the biliary pressure and, therefore, the simple obstruction of the choledochoduodenal junction by one gallstone does not result in biliary pancreatic reflux. We propose a mechanism whereby simultaneous migration and sequential impaction above and below the common biliary pancreatic ampulla of two gallstones allows for the creation of a toxic bile-pancreatic juice mixture in the common bile duct, subsequent reversal of the pressure gradient and reflux of the toxic secretions into the pancreatic duct.