Sphincter of Oddi dysfunction (SOD)

Does Sphincter of Oddi Dysfunction Even Exist Anymore?

Published on Feb 9, 2017

Speaker: Grace H. Elta, MD, FACG
Learning Objective: Discuss the current understanding of SOD in the modern era of evidence-based medicine.
Source: 2016 ACG Postgraduate Course, Las Vegas, NV

https://www.youtube.com/watch?v=78xn5hwEWqk

Diseases: Pancreas and Biliary Tree: Sphincter of Oddi Dysfunction

Gallstones are the most common cause of gallbladder dysfunction and symptoms such as pain and infection (cholecystitis). However, sometimes the gallbladder can become inflamed and partially obstructed in the absence of stones.

The normal gallbladder contracts through muscular activity in response to food, forcing bile through its exit channel (the cystic duct) and into the bile duct for passage into the intestine (through the sphincter of Oddi or the papilla of Vater). If these movements are not appropriately coordinated, the pressure can rise and result in gallbladder type pain.

In this condition, the gallbladder may appear normal on the standard ultrasound scan; abnormalities are only detected when the gallbladder is stimulated to contract, with food or after an injection of a stimulating hormone (cholecystokinin – CCK). Failure of the gallbladder to contract properly, especially if the patient's pain is reproduced, is good evidence of gallbladder dysfunction. This can also be investigated by a special type of isotope scan (HIDA scan) during which the behavior of the bile can be watched and the emptying of the gallbladder measured (the ejection fraction). Patients with clearcut symptoms and positive test results respond well to removal of the gallbladder (laparoscopic cholecystectomy).

Papillary Stenosis: Sphincter of Oddi Dysfunction
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.

Sphincter of Oddi dysfunction and papillary stenosis are conditions which occur when this sphincter (opening) mechanism is disturbed. When the hole is too tight, there is a backup of bile and pancreatic juices. This can cause pain (biliary colic). More prolonged obstruction may result in bile leaking back into the blood stream, resulting in abnormalities of the liver function tests, or even yellow jaundice (discoloration of the eyes and skin). Also, blockage to the pancreatic orifice can cause pancreatic pain or attacks of pancreatitis.

Papillary Stenosis can be caused by passage of stones, or scarring after treatments (i.e. endoscopic or surgical sphincterotomy). Papillary stenosis usually results in sufficient backup of bile flow that there is stretching (dilatation) of the bile duct. This can be recognized by scans (such as ultrasound , CT and MRCP) and various x-rays, including ERCP (Endoscopic Retrograde CholangioPpancreatography). Papillary stenosis requires endoscopic or surgical treatment. The hole is enlarged by cutting, to improve drainage. Occasionally it is necessary to do a surgical bypass (choledochoduodenostomy, or Roux-en-Y hepaticojejunostomy) to insure that drainage is effective.

Sphincter of Oddi dysfunction (SOD)
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 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 gives good relief in most patients (but not all). The performance of 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.

http://www.ddc.musc.edu/public/problems/diseases/pancreas/sphincterOddi.cfm