Sphincter of Oddi dysfunction
Sphincter of Oddi dysfunction or SOD is a condition where the opening of a duct that connects to the gallbladder and the pancreas does not open and close regularly but spasms. Most patients are women between 30 and 50 who have had cholecystectomies (that is, have had their gallbladders surgically removed). Doctors do not know why this is, but SOD is so common among patients who have had their gallbladders removed that some call it post-cholecystectomy syndrome.
Definition & Facts
It is important for the Sphincter of Oddi to open when a person eats so that enzymes and juices from the pancreas and gallbladder or liver can enter the duodenum and help the body digest food. Because the sphincter does not function well, it causes a backup of bile and pancreatic juices that leads to abdominal pain. Severe cases can lead to pancreatitis, an inflammation of the pancreas.
There are three categories of SOD. They are I, II and III, though some medical professionals no longer recognize type III. There are also two types of SOD. In one type, the enzymes back up into the pancreas, and in the other, bile and other digestive juices back up into the bile ducts.
Symptoms & Complaints
Jaundice, the yellowing of the skin and the whites of the eyes (sclera), is also a symptom of SOD as are chills, fever, nausea, and vomiting. That patient also experiences diarrhea. The taking of opiates sometimes makes SOD symptoms worse, especially in patients who have had a cholecystectomy or who have had weight loss surgery.
Doctors do not know what causes SOD. Some medical experts believe it can be caused by tiny stones in the bile or an inflammation of the upper part of the small intestine, or the duodenum. Other health care professionals believe that the problem is caused by hormones found in the gut or peptides such as cholecystokinin, or CCK which triggers the body to digest proteins and fats. CCK also appears to regulate how the sphincter opens and closes.
Diagnosis & Tests
Because the symptoms of SOD resemble the symptoms of other disorders, the doctor must first rule out other causes of abdominal distress such as cancer, ulcers, or gallstones. In some patients, heart disease can express itself as abdominal pain.
Doctors diagnose SOD through blood tests that check the levels of pancreatic and liver enzymes like transaminases. They also use quantitative hepatobiliary scintigraphy. In this test, a physician injects a radioisotope into the patient’s blood and watches how it circulates through the biliary system. If the radioisotope takes a long time to pass, SOD may be the cause.
Another test is called an ERCP or endoscopic retrograde cholangiopancreatography. In this test, a doctor inserts a long, flexible tube with a tiny camera on the end into the patient’s mouth and down through the gastrointestinal tract to the area where the pancreatic and bile ducts open into the duodenum. The doctor then gives the patient a contrast material, measures the diameters of the ducts and notices how long it takes them to drain.
Doctors may also use ultrasound and computed tomography (CT) scans during the diagnostic process. Another imaging test is magnetic resonance cholangiopancreatography, or MRCP. This is a magnetic resonance imaging (MRI) test which checks the ducts that come from the pancreas and the liver. Another test is endoscopic ultrasound, or EUS. This uses an endoscope with a transducer on the end. The transducer sends sound waves into the GI tract that produces images of the area.
These tests work with category I and II SOD, but not with category III. In this category, doctors cannot find any abnormalities that may suggest SOD. The patient just has the symptoms of the disorder. This leads some doctors to conclude that these patients aren’t suffering from SOD at all but from something else.
The common bile duct in patients with the type of SOD that affects the bile ducts is often dilated. In one test, the patient is given a meal high in fats then the diameter of the bile duct is measured after about 45 minutes. If SOD is suspected, the duct expands. Normally, the duct does not expand or may even shrink. Still, doctors do not think this test is extremely accurate.
The most accurate test to diagnose SOD is sphincter of Oddi manometry, which is usually done at the same time as ERCP. This test measures the pressure of the sphincter. High pressure means that it is malfunctioning. The one drawback of this test is that it can cause a bout of pancreatitis.
Treatment & Therapy
Doctors treat SOD by placing the patient on a low fat diet and prescribing non-opioid painkillers and drugs that ease the spasms of the sphincter. They also prescribe nitroglycerin and nifedipine. Converted into nitric oxide when it’s ingested, nitroglycerin serves as a vasodilator, which means it widens blood vessels. Nifedipine is usually taken to lower high blood pressure.
Botox injections into the sphincter have been known to relax its spasms. Botox, or botulinum toxin, works by paralyzing the sphincter muscle. If the less invasive treatments do not work, the sphincter can be cut or removed surgically.
Most people find relief of their symptoms after the sphincter is removed, though sphincterotomy is difficult and comes with risks. Some patients have a recurrence of symptoms because of scar tissue caused by the surgery. During the sphincterotomy, the doctor checks to make sure there are no stones in the gallbladder if it is still there or in the patient’s bile ducts.
Prevention & Prophylaxis