The EPISOD study is no longer accepting patients. The number needed has been reached. Results are being analyzed and will be published sometime in spring or summer 2014.
The sphincter of Oddi is the muscular valve surrounding the exit of the bile duct and pancreatic duct into the duodenum, at the papilla of Vater. The sphincter is normally closed, opening only in response to a meal so that digestive juices can enter the duodenum and mix with the food for digestion.
SOD describes the situation where the sphincter goes into “spasm”, causing temporary back up of biliary and panctreatic juices, resulting in attacks of abdominal pain (or pancreatitis). The pain symptoms are very similar to those caused by bile duct or gallbladder stones. Indeed, sphincter of Oddi dysfunction most frequently occurs in patients who have previously undergone removal of the gallbladder (cholecystectomy). SOD may be one manifestation of other muscular spasm problems in different areas of the body (such as the esophagus, or intestine – irritable bowel syndrome). However, in some patients, it is the prevailing complaint, and requires focal attention.
Diagnosis of SOD
Initially, tests are aimed to make sure that there are no other problems present, like a stone or small tumor. Standard ultrasound and CT scans are helpful, but not very accurate in detecting or excluding small stones. Newer techniques such as MRCP and endoscopic ultrasound (EUS) are more sensitive, and useful. Most patients are investigated with ERCP, with Sphincter of Oddi Manometry (SOM). For ERCP, the doctor passes a special flexible endoscope (under sedation or anesthesia), to examine the drainage hole of the bile duct at the papilla of Vater. Dye is injected into the bile duct and pancreatic duct to double-check for stones and other forms of obstruction. The possibility of sphincter spasm (dysfunction) is tested during the ERCP by measuring the “squeeze pressure” in the sphincter, with manometry (SOM). SOM is performed only in special referral hospitals. Like all types of ERCP examination, there are risks, particularly the chance of suffering an attack of pancreatitis. For this reason, ERCP in this context is usually done only after other simpler tests have been exhausted.
Treatment of SOD
Mild forms of SOD can be managed by anti-spasm medicines. When attacks of pain cause considerable disturbance with life activities, a decision has to be made whether to cut the sphincter (sphincterotomy), during ERCP. When sphincter of Oddi manometry has confirmed that the pressures are high, sphincterotomy can give relief, but not in all patients. The purpose of the EPISOD study is to establish better criteria for offering sphincterotomy, ie which patients are likely to respond, or not to respond. This is very important, since sphincterotomy carries a risk of complications, such as bleeding and perforation, in addition to pancreatitis. There is also the possibility of recurrent symptoms after months or years due to scarring of the sphincterotomy. Further cutting (repeat sphincterotomy) is sometimes possible, but there are limits; surgical treatment with a transduodenal sphincteroplasty may be necessary. Transduodenal sphincteroplasty may also be recommended in lieu of ERCP in patients who have undergone previous gastric surgery.
Sphincter of Oddi Dysfunction is a difficult condition, which should be approached and managed with considerable care. Patients may warrant referral to specialist centers, who often have special research protocols.
The “EPISOD” study is based at the Medical University of South Carolina, headed by Dr. Peter Cotton.