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Harvard Medical School
The test is performed by a gastroenterologist in a procedure room or in a hospital. You are usually given a sedative through an IV line. You wear a hospital gown for the procedure and lie on your side against a backrest on an x-ray table. If you wear dentures, remove them. A local anesthetic is sprayed into your throat to prevent you from having a gag reflex (choking feeling) when the endoscope is placed inside. The endoscope is about a third of an inch in diameter and 2 1/2 feet long with a light on the end. It also has holes at the end that allow your doctor to pump air into your intestine, squirt fluid, and suck out liquid or air.
You are asked to swallow at the moment the tube is placed into your throat. This helps guide the endoscope into your esophagus. You are likely to feel pressure against your throat while the tube is in place and you might experience a "full" feeling in your stomach. The doctor or doctor's assistant gently advances the tube until it reaches your duodenum, the first part of the small intestine.
Next, the doctor inserts a slender tube, called a cannula, through the endoscope, and places the tip of the cannula into the bile duct or the pancreatic duct. These ducts are natural tubes of tissue that drain liquids out of the liver and pancreas. Once the tip of the cannula is lodged inside one of these ducts, the doctor injects contrast dye (usually iodine) through the cannula. The dye can be seen by x-rays, so it lights up the ducts clearly on an x-ray image, showing any obstruction (such as from gallstones or cancer) or unusual widening of the ducts (indicating an obstruction in the past). It also can light up the gallbladder in the X-Ray picture. The gallbladder connects to the bile duct. This test also helps the doctor to visualize the liver and pancreatic tissue around the ducts.
Depending on what the x-rays show, the doctor may undertake different interventions using tools operated through the endoscope. The doctor can remove gallstones or take biopsies of suspicious tissue. He or she can prop open narrowed bile ducts with a stent, a tube-shaped object that can be inserted through the scope. Depending on what is done, the test can take from 30 minutes to two hours.