What is the Sphincter of Oddi?

The sphincter of Oddi is a small, muscular valve through which the digestive juices secreted by several internal organs enter the small intestine for the essential breaking down of food. It is named for Ruggero Oddi, an Italian physician of the turn of the 19th century who detailed its anatomical form and function. Rarely, it might be called Glisson’s sphincter, for the English physician who first identified it. Commonly, it also is referred as the hepatopancreatic sphincter, because of its function as the terminal end of tubular ducts originating from the organs of the liver and pancreas.

Along the human digestive system, just beyond the stomach’s large and muscular bottom sphincter, is an S-shaped tract of the small intestine called the duodenum. About 2.75-4.0 inches (7-10 cm) along the duodenum, within its descending stretch, is the sphincter of Oddi, an opening normally pinched shut by a small knot of circular and longitudinal smooth muscle fibers. When the duodenum senses the presence of chyme, the partially digested food expelled by the stomach, its lining tissue secretes a hormone called cholecystokinin that, in turn, induces the muscles of the sphincter of Oddi to relax. The sphincter is the opening to the ampulla of Vater, named for a German anatomist, also called the hepatopancreatic ampulla. This small, urn-shaped sac contains a brew of digestive enzymes that is ejected into the duodenum through a protruding nozzle called the bile papilla.

Among the many functions of the human liver is the production of bile, which is stored in the adjoining gall bladder. The bile juices leave the gall bladder via a tube called the cystic duct, which merges with the common bile duct and finally ends at the ampulla of Vater. The main digestive components in bile are organic salts that emulsify fats into smaller pieces for enzymes such as lipase to break down more effectively. Pancreatic juices include sodium hydrogencarbonate, which neutralizes the acidity of chyme, thus also allowing other enzymes to more efficiently break down the food slurry. The pancreas’ chemical output also flows through the pancreatic duct to the ampulla of Vater by merging with the common bile duct.

Given the functional importance of the sphincter of Oddi, its dysfunction is correspondingly serious. The most common problem occurs when the orifice is obstructed, either by a gallstone or by stenosis, a narrowing of either the orifice or its leading pathways. In addition to digestive problems, the obstruction will create complications for all of the upstream organs, possibly pancreatitis or cirrhosis of the liver. If the sphincter itself becomes inflamed, the condition is called odditis. If the muscles that control its function as a valve fail for any reason — a condition called sphincter of Oddi dyskinesia — then the physiological complications, diagnosis difficulty and treatment decisions increase substantially.