The sphincter of Oddi (also known as sphincter of ampulla) is a muscular valve that controls the flow of bile and pancreatic juice through the ampulla of Vater into the second part of the duodenum. Increased tone of the sphincter or disturbance in the coordination of contraction of the biliary ducts prevents normal emptying of the biliary tree. This may result in biliary pain, common bile duct dilation and episodes of pancreatitis.