A biliary stent is a plastic or metal tube that is inserted into a bile duct to relieve narrowing of the duct (also called bile duct stricture).
Biliary stenting is used to treat obstructions that occur in the bile ducts. Bile is a substance that helps to digest fats and is produced by the liver, secreted through the bile ducts, and stored in the gallbladder. It is released into the small intestine after a fat-containing meal has been eaten. The release of bile is controlled by a muscle called the sphincter of Oddi found at the junction of the bile ducts and the small intestine.
There are a number of conditions, malignant or benign, that can cause strictures of the bile duct. Pancreatic cancer is the most common malignant cause, followed by cancers of the gallbladder, bile duct, liver, and large intestine. Noncancerous causes of bile duct stricture include:
The overall incidence of bile duct stricture is not known. Approximately 0.2–0.5% of patients undergoing gallbladder surgery or other operations affecting the bile duct develop biliary stricture.
A biliary stent is a thin, tube-like structure that is used to support a narrowed part of the bile duct and prevent the reformation of the stricture. Stents may be made of plastic or metal. The two most common methods that are used to place a biliary stent are endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic cholangiography (PTC).
ERCP is an imaging technique used to diagnose diseases of the pancreas, liver, gallbladder, and bile ducts that also has the advantage of being used as a therapeutic device. The endoscope (a thin, lighted, hollow tube attached to a viewing screen) is inserted into a patient's mouth, down the esophagus, through the stomach, and into the upper part of the small intestine, until it reaches the spot where the bile ducts empty. At this point a small tube called a cannula is inserted through the endoscope and used to inject a contrast dye into the ducts; the term retrograde refers to the backward direction of the dye. A series of x rays are then taken as the dye moves through the ducts.
If the x rays show that a biliary stricture exists, a stent may be placed into a duct to relieve the obstruction. In order to do this, special instruments are inserted into the endoscope and a sphincterotomy (a cut into the sphincter of Oddi) is performed to provide access to the bile ducts. In some cases, the biliary stricture may first be dilated (expanded) using a thin, flexible tube called a catheter, followed by a balloon-type device that is inflated. The stent is then inserted into the bile duct.
PTC is similar to ERCP in that the test is used to diagnose and treat obstructions affecting the flow of bile from the liver to the gastrointestinal tract. The procedure is generally reserved for patients who have undergone unsuccessful ERCP. A thin needle is used to inject a contrast dye through the skin and into the liver or gallbladder; x rays are taken while the dye moves through the bile ducts. If a biliary stricture becomes evident, a stent may then be placed. A hollow needle is introduced into the bile duct, and a thin guide wire inserted into the needle. The wire is guided to the area of obstruction; the stent is advanced over the wire and placed in the obstructed duct.
Prior to ERCP or PTC, the patient will be instructed to refrain from eating or drinking for at least six hours to ensure that the stomach and upper part of the intestine are free of food. The physician should be notified as to what medications the patient takes and if the patient has an allergy to iodine, which is found in the contrast dye. Antibiotics will be started prior to surgery and continued for several days afterward.
After the procedure, the patient is monitored for signs of complications. In the case of ERCP, the patient generally remains at the hospital or outpatient facility until the effects of the sedative wear off and to ensure no complications occur. After PTC, the patient is instructed to lie on his or her right side for at least six hours to reduce the risk of bleeding from the injection site. To ensure that the stent is functioning properly, the patient will be frequently assessed for symptoms that indicate the recurrence of biliary stricture. These symptoms include changes in stool or urine color, jaundice (yellowing of the skin), itching, and abnormal liver function tests .
Complications associated with ERCP include excessive bleeding, infection, pancreatitis, cholangitis (inflammation of the bile ducts), cholecystitis (inflammation of the gallbladder), and injury to the intestine. PTC may result in bleeding, infection of the injection site, sepsis (spread of infection to the blood), or leakage of the dye into the abdomen. Complications specific to the stent include migration (movement of the stent out of the area in which it was placed), occlusion (blockage), and intestinal perforation.
In more than 90% of patients, the placement of a biliary stent relieves the obstruction and allows the bile duct to drain properly.
The rate of serious complications with ERCP is approximately 11%, and 5–10% with PTC. Stent occlusion occurs in up to 25% of patients, and stent migration in up to 6%. Recurrence of biliary stricture occurs in 15–45% of patients after an average time of four to nine years.
The major alternative to biliary stenting is surgical repair of the stricture. The most common method is resection (removal) of the narrowed area followed by the creation of a connection between the bile duct and the middle portion of the small intestine (called a choledochojejunostomy) or the hepatic duct and the small intestine (called a hepaticojejunostomy). Surgical stricture repair results in a cure for 85–98% of patients and is associated with a low risk of complications.
Feldman, Mark, et al. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 7th ed. Philadelphia: Elsevier Science, 2002.
American Gastroenterological Association. 7910 Woodmont Ave., 7th Floor, Bethesda, MD 20814. (301) 654–2055. http://www.gastro.org .
American Society for Gastrointestinal Endoscopy. 1520 Kensington Rd., Suite 202, Oak Brook, IL 60523. (630) 573–0600. http://www.asge.org .
Society of Interventional Radiology. 10201 Lee Highway, Suite 500, Fairfax, VA 22030. (800) 488–7284. http://www.sirweb.org .
Pande, Hemant, Parviz Nikoomanesh, and Lawrence Cheskin. "Bile Duct Strictures." eMedicine. June 3, 2002 [cited May 1, 2003]. http://www.emedicine.com/med/topic3425.htm .
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Stephanie Dionne Sherk
Biliary stenting is usually performed in the xray department of a hospital or outpatient facility in consultation with a general surgeon, a gastroenterologist (a medical doctor who specializes in the diagnosis and treatment of diseases of the digestive system), and/or an interventional radiologist (a medical doctor who specializes in the treatment of medical disorders using specialized imaging techniques).