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.
Is there any special preparation prior to the test?
The tracer material is made precisely for the time of your exam. It is veryimportant for you to arrive on time if
you are undergoing this procedure as an outpatient.
You physician will give you instructions about eating or taking medications prior to your exam.
Is there any special follow-up care after the test?
You should be able to resume your normal activities after the test. The tracer material passes quickly from the body
through normal bodily functions.
Unless you are on a fluid restriction, your physician may recommend that you drink plenty of water or fluids after the test to help your body to get rid of the tracer more quickly.
If you were asked to temporarily stop taking medications prior to the test, or if your physician changed the usual dosage because of the test, be sure to ask when and if you should resume taking your medications.
Is there a danger from the radioactive material?
The smallest amount of radioactive material possible is used to perform the scan and it is short-lived, so exposure to
radiation is limited.
For female patients, if there is any possibility you may be pregnant or if you are breastfeeding, it is important to tell this to your physician and the technologist before the procedure.
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.
What are the limitations of cholescintigraphy (HIDA scan)?
Nonvisualization (the failure of the gallbladder to appear on a cholescintigraphy scan) of the gallbladder occurs because of disease of the gallbladder, particularly gallstones.
However, nonvisualization does not necessarily mean that the obstruction is the cause of the patient’s problem. For example, patients with gallstones often have a nonvisualizing gallbladder due to obstruction of the cystic duct, but the obstruction causes no symptoms.
Thus, cholescintigraphy is helpful only if the patient’s problem is likely-based on the history and physical examination-to be due to disease of the gallbladder or bile ducts.
With the use of cholecystokinin, poor contraction of the gallbladder can be seen in some normal individuals. Therefore, reduced contraction does not always mean that the gallbladder is diseased.
Again, cholescintigraphy with cholecystokinin is helpful only if the patient’s problem is likely-based on the history and physical examination-to be due to disease of the gallbladder or bile ducts.
Another limitation of cholescintigraphy is that this test does not work when the patient’s serum bilirubin is greater than 15-20 mg%.
What are the side effects of cholescintigraphy (HIDA scan)?
There are few side effects to cholescintigraphy. Reactions to the radioactive chemical and cholecystokinin are rare. The amount of radioactivity that patients are exposed to is small.
The radioactive compound is eliminated in the stool, and the radioactivity deteriorates rapidly within hours.
What alternatives are there tocholescintigraphy (HIDA scan)?
Other common means of evaluating the gallbladder and bile ducts include ultrasonography and computerized tomography (CT or CAT scan).
Cholangiography, either percutaneous (through the skin) or endoscopic (ERCP) (inserted down the throat), is a radiological procedure in which dye is injected into the gallbladder and bile ducts and then x-rays are taken.
Newer procedures include endoscopic ultrasonography and magnetic resonance imaging (MRI) cholangiography.
Oral cholecystography in which x-rays are taken of the gallbladder following ingestion of a dye that is concentrated in the gallbladder, is rarely done.