The Sphincter of Oddi (SO) is a fibromuscular sheath that encircles the terminal portion of the common bile duct, pancreatic duct, and common channel in the second portion of the duodenum; It is made up of smooth muscle; Three interconnected sphincters exist: choledochus, pancreaticus, and ampulla

SOD Dysfunction (SOD): a benign disorder characterized by functional or structural obstruction at the level of the sphincter; It is suspected in patients with RUQ pain suggestive of a biliary or pancreatic origin

Risk for SOD: Females in 3rd to 5th decades of life (up to 90%)

Symptoms often apparent after cholecystectomy; Incidence is approximately 1% in post cholecystectomy patients

Long-term opiate use can precipitate SOD due to increased pressures in the biliary ducts

Function of SO: Regulates bile and pancreatic juice into the duodenum, reduces duodenal reflux into the pancreatic/biliary ducts, contracts tonically during the interdigestive portion to promote gallbladder filling, contracts phasically in the digestion period (cholinergic stimulation) to promote flow of bile

Two abnormalities that can lead to SOD:

Symptoms can be biliary or pancreatic in nature: Pain in RUQ with radiation to back and may be meal related; episodic or continuous

Symptoms of IBS often co-exist and it can often be difficult to distinguish SOD from Non-ulcer dyspepsia