Alternative names: SOD
The Sphincter of Oddi is a smooth muscular valve surrounding the shared end of the bile and pancreatic ducts. When this valve loses its ability to contract and relax during a meal, the flow of digestive juices (bile and pancreatic juice) into the small intestine is obstructed, leading to severe abdominal pain and other possible complications.
More than half a million gallbladder removal surgeries are performed annually in the United States. Some 10-20% of these patients experience continuing or recurrent pains, sometimes caused by Sphincter of Oddi Dysfunction.
Sphincter of Oddi Dysfunction is usually seen in female patients, typically 30-50 years old, who have had their gallbladders removed.
The main symptom of Sphincter of Oddi Dysfunction is recurring upper-right quadrant or epigastric abdominal pain, also known as biliary colic. The pain is usually steady, usually severe, and often made worse by meals – especially fatty meals. It is caused by the back-up of digestive juices.
In order to diagnose Sphincter of Oddi Dysfunction, a blood test is used to look for abnormal liver and pancreatic enzyme levels. Quantitative Hepatobiliary Scintigraphy is a procedure that is used to measure the uptake and clearance of an injected radioactive isotope from the liver and biliary tract.
In about half of all presenting cases, laboratory testing or imaging (blood test, ultrasound, CT scan, or MRCP) will suggest a definite abnormality such as a bile duct stone. MRCP (magnetic resonance cholangiopancreatography) is a good non-invasive procedure to determine the state of the biliary and pancreatic drainage systems.
In patients with severe symptoms, a risky procedure called ERCP (endoscopic retrograde cholangiopancreatography) is often employed. This procedure facilitates examination or treatment of the bile and pancreatic ducts but carries a significant risk of serious complications. Complications include an attack of pancreatitis in 5-10% of cases, necessitating a stay in hospital ranging from (usually) a few days to (rarely) weeks or months, as well as bleeding, perforation, and possible narrowing of a duct due to scarring.
The gold standard diagnostic procedure is called a 'sphincter of Oddi manometry' (SOM). This allows a doctor to take a close look at the sphincter of Oddi to see if it is functioning normally. A small plastic tube is inserted into the pancreas duct or bile duct near the sphincter of Oddi to measure pressure when it contracts and expands. High pressures indicate dysfunction.
In cases where the pain is not too severe, medical treatment is usually the preferred option. There are no drugs specifically for SOD; pain medication, antispasmodics, non-addictive analgesics, nifedipine and nitroglycerin are among those used. The side-effects of these drugs usually limit their usefulness.
In cases where the pain is severe, tests have confirmed Sphincter of Oddi Dysfunction, and medical treatment has failed, a surgical procedure (sphincterotomy) may be used to remove any stones or to relieve any scarring or spasm of the sphincter by cutting a muscle. It is a difficult procedure with a significant risk of complications.
Other invasive treatment modalities include endoscopic injection of botulinum toxin (Botox) into the sphincter, and endoscopic or surgical ablation of the sphincter of Oddi.
About 70% of patients who have undergone endoscopic or surgical procedures experience long-term pain relief.
Sphincter of Oddi Dysfunction can lead to pancreatitis.
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