The sphincter of Oddi is a muscular valve that surrounds the exit of the bile duct and pancreatic duct. Both of these ducts drain into the duodenum, which is the tube that comes off the end of the stomach. The sphincter is usually closed but opens to allow drainage of bile and pancreatic juices to flow to aid in digestion of food.

Sphincter of Oddi dysfunction (SOD) is not completely understood but it is thought the sphincter goes into spasm causing the back up of pancreatic and bile juices and in turn causes abdominal pain.