The human sphincter of Oddi. Physiology and pathophysiology

The sphincter of Oddi (SO) is critically located at the junction of the common bile duct (CBD), main pancreatic duct, and the duodenum. It is a high-pressure zone with phasic contractions that regulate bile and pancreatic juice flow. The SO is probably regulated by several gastrointestinal hormones, and its basal pressure and phasic contractions can be elevated or decreased significantly by exogenous drugs. Its role in gallstone formation is probably negligible, but severing the SO allows one to extract CBD stones with an endoscope. Abnormal function of the SO can cause biliarylike pain. Of patients with persistent pain after cholecystectomy, 14% have abnormal SO manometric findings. Endoscopic or surgical sphincterotomy can cure these patients of their pain. The SO may play a significant role in the development of pancreatitis in certain patients, either because of the relationship of the CBD orifice to the pancreatic duct orifice created by the SO or because of the response of the SO to exogenous agents, such as alcohol.