Cholescintigraphy

A nuclear medicine imaging technique for the gallbladder and bile ducts

Cholescintigraphy, also known as hepatobiliary scintigraphy or a HIDA scan, is a diagnostic imaging technique used in nuclear medicine to evaluate the health and function of the gallbladder and the biliary system. This procedure involves the intravenous injection of a radioactive tracer, which is then taken up by the liver and excreted into the bile. The movement of the tracer through the biliary system is captured using a gamma camera, providing valuable information about the function and structure of the gallbladder and bile ducts.

Procedure

A HIDA scan showing normal gallbladder function

The procedure begins with the intravenous administration of a radiopharmaceutical, commonly a technetium-99m-labeled compound such as technetium-99m mebrofenin or technetium-99m disofenin. These compounds are selectively taken up by the liver and excreted into the bile. The patient is positioned under a gamma camera, which detects the gamma rays emitted by the tracer and creates images of its distribution in the body.

The scan typically takes about 1 to 2 hours to complete. During this time, images are taken at regular intervals to track the flow of the tracer from the liver into the gallbladder and through the bile ducts into the duodenum. In some cases, additional medications such as cholecystokinin (CCK) or morphine may be administered to stimulate gallbladder contraction or to enhance the visualization of the biliary system.

Indications

Cholescintigraphy is primarily used to diagnose conditions related to the gallbladder and biliary tract. Common indications for a HIDA scan include:

• Evaluation of acute cholecystitis, which is inflammation of the gallbladder often due to gallstones.
• Assessment of chronic gallbladder disease or biliary dyskinesia, where the gallbladder does not empty properly.
• Detection of bile duct obstruction, which can be caused by gallstones, tumors, or strictures.
• Evaluation of biliary atresia in infants, a condition where the bile ducts are abnormally narrow or absent.

Interpretation

The results of a HIDA scan are interpreted based on the pattern of tracer uptake and excretion. In a normal study, the tracer is rapidly taken up by the liver, appears in the gallbladder within 30 to 60 minutes, and is seen in the small intestine shortly thereafter. Delayed or absent visualization of the gallbladder may indicate acute cholecystitis, while delayed transit into the intestine may suggest a bile duct obstruction.

Advantages and Limitations

Cholescintigraphy is a non-invasive and highly sensitive method for evaluating gallbladder function and biliary tract patency. It provides functional information that cannot be obtained from anatomical imaging techniques such as ultrasound or CT scan. However, it has limitations, including exposure to ionizing radiation and the potential for allergic reactions to the radiopharmaceutical. Additionally, the test may be less accurate in patients with severe liver disease or those who have recently eaten.

Related pages

• Gallbladder
• Biliary tract
• Nuclear medicine
• Technetium-99m
• Cholecystitis