Duodenal biliary drainage is a little-used procedure that sometimes can be helpful in diagnosing gallstones. Gallstones begin as microscopic particles of cholesterol or pigment that grow in size but once the particles grow large enough to become gallstones, they can obstruct the bile ducts and cause problems.
The patients with symptoms and complications of gallstones (biliary colic, cholecystitis, or pancreatitis) have only these microscopic particles in their gallbladders, particles too small to obstruct the bile ducts. For that, there are two possible explanations.
The first is that a small gallstone obstructed the bile ducts but finally passed through the bile ducts into the intestine and the second is that the particles passing through the bile ducts "irritate" the ducts, causing spasm of the muscle within the walls of the ducts (which obstructs the duct) or causing inflammation of the duct so that the wall of the duct swells (which also obstructs the duct).
Duodenal biliary drainage is useful in diagnosing problems related to gallstones when other tests such as ultrasonography have not demonstrated gallstones, but suspicion is high that gallstones are the cause of the patient's problem.
Sometimes cholesterol or pigment particles without gallstones may be present in patients who have no medical problems or problems that are not due to gallstones. Because of such individuals, it also is important not to assume that particles mean that gallstones are the cause of a medical problem. The medical problem and its symptoms should be typical of the types of problems caused by gallstones.
During the procedure, a thin plastic or rubber tube with several holes at its tip is passed through a patient's anesthetized nostril, down the back of the throat, through the esophagus and stomach, and into the duodenum where the bile and pancreatic ducts enter the small intestine with the help of fluoroscopy, a type of X-ray.
A synthetic hormone related to cholecystokinin is injected intravenously once the tube is in place. The hormone causes the gallbladder to contract and squeeze out its concentrated bile into the duodenum. The bile then is sucked up through the tube and examined for the presence of cholesterol and pigment particles under a microscope.
A modification of duodenal biliary drainage involves the collection of bile through an endoscope at the time of an upper gastrointestinal endoscopy – either by EGD (esophagogastroduodenoscopy) or by ERCP (endoscopic retrograde cholangio-pancreatography).
The risks to the patient of duodenal biliary drainage are almost nonexistent. The presence of the tube in the throat is uncomfortable for the 30-60 minutes that are necessary to complete the test.