HIDA scan

An overview of HIDA scan

A HIDA scan, also known as a hepatobiliary iminodiacetic acid scan, is an imaging procedure used to diagnose problems with the liver, gallbladder, and bile ducts. It involves injecting a radioactive tracer into a vein in the arm, which then travels to the liver, gallbladder, and small intestine. A gamma camera tracks the tracer's movement and creates images for analysis. A HIDA scan can help diagnose conditions such as gallbladder inflammation, bile duct obstruction, and liver transplant assessment. The risks of the scan are minimal and may include allergic reactions, bruising, and small radiation exposure.

What is HIDA scan used for?

A HIDA scan is used to diagnose problems of the liver, gallbladder, and bile ducts. It helps evaluate the gallbladder, assess the bile-excreting function of the liver, and track the flow of bile from the liver into the small intestine. A HIDA scan may be used to diagnose conditions such as gallbladder inflammation, bile duct obstruction, congenital problems in the bile ducts, postoperative complications, and assess the liver transplant. It is also used to measure the rate at which bile is released from the gallbladder, known as gallbladder ejection fraction.

How to prepare for HIDA scan?

Before an HIDA scan test, you will need to make some preparations. Your healthcare provider will likely ask you to:

How is HIDA scan conducted?

An HIDA scan test is conducted by injecting a radioactive tracer into a vein in the arm, which travels through the bloodstream to the liver, gallbladder, and bile ducts. A gamma camera tracks the flow of the tracer and creates computer images. During the procedure, you may receive an IV injection of sincalide or morphine to help contract and empty the gallbladder. After the test, drink plenty of water to flush the tracer out of your system. Your healthcare provider will consider your symptoms, test results, and other factors to make a diagnosis.

How are HIDA scan results reported?

HIDA scan results are reported based on the movement of the radioactive tracer through the body, primarily focusing on the liver, gallbladder, and bile ducts. The scan results include:

1. Typical: The radioactive tracer moved freely with the bile from the liver into the gallbladder and small intestine.
2. Slow movement of radioactive tracer: This might indicate a blockage, obstruction, or a problem in liver function.
3. No radioactive tracer seen in the gallbladder: Inability to see the radioactive tracer in the gallbladder might indicate acute inflammation, called acute cholecystitis.
4. Low gallbladder ejection fraction: The amount of tracer leaving the gallbladder is low after medicine is given to make it empty. This might indicate chronic inflammation, known as chronic cholecystitis.
5. Radioactive tracer detected in other areas: Radioactive tracer found outside of the biliary system might indicate a leak. The results of a HIDA scan are generally interpreted in combination with the patient's symptoms and other test results to make a diagnosis. Your healthcare provider will discuss the results with you and determine the appropriate course of action based on the findings.

Understanding the report

HIDA scan results are interpreted by evaluating the movement of the radioactive tracer through the body and its appearance in images captured by the gamma camera. Based on the results, the healthcare provider can diagnose various diseases and conditions related to the liver, gallbladder, and bile ducts. The five possible results of a HIDA scan are:

1. Typical: The radioactive tracer moves freely with the bile from the liver into the gallbladder and small intestine.
2. Slow movement of radioactive tracer: This might indicate a blockage, obstruction, or problem in liver function.
3. No radioactive tracer seen in the gallbladder: Inability to see the tracer in the gallbladder could suggest acute inflammation (acute cholecystitis).
4. Low gallbladder ejection fraction: A low amount of tracer leaving the gallbladder after it's emptied might indicate chronic inflammation (chronic cholecystitis).
5. Radioactive tracer detected in other areas: Tracer found outside the biliary system could indicate a leak.

The healthcare provider will consider the results in conjunction with the patient's symptoms and other test results to make a diagnosis.

Limitations and Considerations

Limitations of the HIDA scan test include:

1. Incomplete visualization: The HIDA scan may not always provide a complete picture of the biliary system, especially in cases of severe inflammation or scarring. Other imaging tests, such as magnetic resonance cholangiopancreatography (MRCP) or endoscopic ultrasound (EUS), may be needed to supplement the findings.
2. Inaccurate results in certain conditions: The test may not always accurately diagnose bile duct obstruction, as it relies on the tracer passing through the obstructed area. In cases of acute inflammation, the tracer may not be visible in the gallbladder due to the inflammation itself, leading to false-negative results.
3. Time-consuming: The procedure can take up to an hour, during which the patient needs to remain still. This might be challenging for young children or those with mobility issues.
4. Limited evaluation of liver function: The HIDA scan mainly focuses on the gallbladder and bile ducts. It may not provide detailed information on the overall liver function or other liver-related conditions.
5. Radiation exposure: Although the radiation exposure from a HIDA scan is small, it is still a consideration for patients who are pregnant or breastfeeding, as well as for individuals undergoing multiple nuclear medicine tests in a short period.