What is cholescintigraphy (HIDA scan)?
Cholescintigraphy is a test done by nuclear medicine physicians to diagnose obstruction of the bile ducts (for example, by a gallstone or a tumor), disease of the gallbladder, and bile leaks. It sometimes is referred to as a HIDA scan or a gallbladder scan.
How is cholescintigraphy (HIDA scan) done?
For cholescintigraphy, a radioactive chemical is injected intravenously into the patient. The test chemical is removed from the blood by the liver and secreted into the bile which is produced by the liver. The test chemical then disperses everywhere that the bile goes-into the bile ducts, the gallbladder, and the intestine. A camera that senses radioactivity (like a Geiger counter) is then placed over the patient's abdomen and a "picture" of the liver, bile ducts, and gallbladder is obtained which corresponds to where the radioactive chemical has traveled within the bile-filled liver, bile ducts, and gallbladder. Cholescintigraphy takes approximately two hours.
How are the results of cholescintigraphy (HIDA scan) used?
There are various patterns of radioactivity that can be seen following the injection of the radioactive chemical, and each has a different meaning. If the test chemical is not detected in the liver, a diseased liver is probably indicated. If the chemical is absorbed by the liver but not secreted into the bile ducts, there probably is a complete obstruction of the bile ducts exiting the liver. When the test chemical fails to appear in the gallbladder, but is detected in the intestine, there probably is an obstruction of the cystic duct leading to and from the gallbladder. (Obstruction is most commonly caused by gallstones and, less commonly, by tumors. Parasites, and blood clots also may obstruct infrequently.) Finally, if the chemical appears outside the liver, bile ducts, gallbladder, or intestine, there probably is a bile leak from the bile ducts or gallbladder.
Cholescintigraphy is most commonly used to diagnose problems with the gallbladder when other more commonly-performed tests, particularly ultrasonography, are normal. Cholescintigraphy can be modified with the addition of an intravenous injection of cholecystokinin, the hormone that is normally released by the body after a meal. This hormone causes the gallbladder to contract and squeeze out its bile into the intestine. Reduced contraction of the gallbladder following cholecystokinin (i.e., reduced emptying of the radioactivity from the gallbladder) may mean that there is disease of the gallbladder itself, particularly inflammation or scarring of the wall.