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.