What is Sphincter of Oddi Dysfunction?

What is Sphincter of Oddi Dysfunction?

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.

Sometimes patients report they have symptoms similar to when they had their gallbladders (if the gallbladder has been removed).

What causes SOD?

Papillary stenosis and biliary dyskinesia are 2 conditions affecting the sphincter.

  • Papillary stenosis is when the drainage from the pancreatic duct and bile duct openings are disrupted. If the opening of the ducts is too tight, there is back up of the juices which can cause abdominal pain. If the pancreatic duct is too tight, abdominal pain and/or pancreatitis can result.
  • Biliary dyskinesia is where the bile ducts fail to open and close properly causing a delay in emptying of the gallbladder or the ducts of the liver. Biliary dyskinesia can might be a precursor to other GI problems such as pancreatitis, chronic pancreatitis or gallstones.

What are the symptoms?

  • Abdominal pain in the right upper abdomen or below the breast bone may be present. Some patients report pain in the upper abdomen radiating to the upper back or shoulder blades. It can be a dull, achy-type pain, or it can be severe enough to lead to an ER visit.
  • Jaundice occurs when the bile duct is blocked for a longer period of time. The bile leaks back into the bloodstream causing yellowing of the skin and eyes, dark tea colored urine, pale stools and abnormal liver function studies.

How is SOD diagnosed?

Sphincter of Oddi Dysfunction (SOD) is considered when the patient has severe attacks of abdominal pain persisting or recurring after gallbladder surgery and when all work up has failed to find an alternate diagnosis for the pain.

Blood work including liver function studies to look for abnormal liver function studies, CT scan and ultrasound to look for structural abnormalities and MRCP to look specifically at the bile and pancreatic ducts are performed to rule other causes of pain.

An Endoscopic Ultrasound is also sometimes done to again look for abnormalities including chronic pancreatitis, bile duct and pancreatic duct stones, tumors and cysts.

There are 2 types of SOD:

  • Type I SOD is seen in patients with biliary type pain, an enlarged bile duct and elevated liver studies.
  • Type II SOD patients have a dilated bile duct or liver function studies but not both.

How is SOD Treated?

Treatment of SOD will depend on the Type; however, often we start with conservative treatment as surgical procedural intervention carries risks. Mild forms are usually treated with medical management including, dietary modification, abstinence from alcohol and smoking, weight loss if BMI greater than 30. Anti-spasmodic and /or anti-depressant (neuromodulator) medication is also used for medical management.

When abdominal pain affects quality of life, a decision has to be made as to whether to proceed with ERCP. There is a possibility of recurrence of symptoms after ERCP months to years due to scarring of the previous sphincterotomy, so a decision to move forward with ERCP is not undertaken lightly.