What Is a HIDA Scan?

A hepatobiliary iminodiacetic acid (HIDA) scan is used to diagnose various conditions involving the gallbladder, liver, and bile ducts.

There are two parts of the test. For the first part, a healthcare provider will inject a radioactive chemical, known as a tracer, into your vein. The tracer emits rays as the substance makes its way through your system. For the second part of the test, a scanner detects the rays and takes images as the tracer goes through your biliary system (gallbladder and bile ducts) and liver. The images of where the tracer goes show if your organs and ducts are working properly.

A HIDA scan is also known as cholescintigraphy, hepatobiliary scintigraphy, or a gallbladder radionuclide scan. The test might be performed alongside other tests, like ultrasound, to reach a diagnosis.

Purpose

Your healthcare provider may recommend a HIDA scan to diagnose a variety of health conditions involving the liver, gallbladder and biliary ducts. A HIDA scan is generally used to check for liver cells' function, to see if the biliary duct is blocked, and to check if the gallbladder is contracting properly.

The test is usually done in people having severe pain that’s suspected to be stemming from a problem in the gallbladder.

One of the most common conditions for which healthcare providers order the scan is acute cholecystitis, which is acute inflammation of the gallbladder that can cause severe pain in the upper-right abdomen.

Other conditions a HIDA scan can help diagnose are:

• Chronic inflammation of the gallbladder (chronic cholecystitis)
• Biliary leak
• Blocked biliary ducts from something like a gallstone or tumor 
• Blockage of the bile ducts due to a congenital condition called biliary atresia

A HIDA scan is usually ordered as one part of the diagnostic process. Your healthcare provider will order other tests depending on your signs and symptoms to reach a final diagnosis.

What Do HIDA Scan Results Mean?

When the gamma-emitting tracer is injected into your body before the scan, the tracer collects in your liver. The tracer will then flow with bile into the gallbladder and then to the small intestine. As the tracer works its way through the system, the scanner will take images. These images will show where the tracer flowed—or did not flow. These results can signal potential blockages, leakages, or inflammation.

After the HIDA scan, your healthcare provider may come to a diagnosis by looking at other imaging and lab tests. HIDA scan results vary based on the condition. Below are some of the results of the HIDA scan and the diseases in which it may occur:

How to Prepare

Your healthcare provider will usually ask you to fast for three to four hours before injecting the tracer material. This gives the food time to pass and for your gallbladder to relax for the test.

If you are taking any opiates and you are undergoing the HIDA scan to check for potential biliary obstruction or chronic gallbladder disease, you will likely be told to stop taking the opiates for at least six hours before the test. The pain-relieving drugs can have an effect on your organs in a way that misleads findings.

Talk to your healthcare provider about the medications that you are taking before the HIDA scan to see if you need to temporarily change or stop the medication ahead of your test.

If you are receiving a HIDA scan to check for a biliary leakage, there might not be a need for any preparation like fasting or medication stoppage. Your prescribing healthcare provider will let you know.

What to Expect During a HIDA Scan

During the HIDA scan, the test administrator may ask you to lie on your back on a table. Above the table, there will be a device that will scan and take images. A healthcare professional injects the tracer—a small amount of radioactive material—usually in the vein of your arm.

The liver absorbs the tracer and, from the liver, the tracer flows into the gallbladder and bile ducts. As the tracer flows, the scanner above you detects the rays that come from the tracer. The scanner takes images of wherever the tracer flows every five to 15 minutes. In all, the test usually takes about one hour.

You should not feel any pain during the test.

Depending on what the initial images show and what the medical concern is, the test administrator may use different processes, including waiting to take images so that they can see how the tracer moves through the system past just the first hour. In some cases, the test can take up to four hours.

If the scan administrator is unable to see the gallbladder due to lack of filling, they might give you a small amount of morphine to help the tracer get into the gallbladder so that they can see the organ on imaging.

The administrator might also inject a medicine that will squeeze your gallbladder. This will show them whether your gallbladder is contracting well. Sometimes, instead of injecting the material, they might have you drink a high-density drink, such as a nutritional drink, to contract the gallbladder.

What to Expect After a HIDA Scan

The radiation from the tracer should be out of your body within a day or two. The only pain you might feel after the test is from where they inserted the needle—typical of anytime a needle is administered.

If you had morphine during the exam, you may feel tired.

Your healthcare provider will discuss the results of the scan and tell you about the best treatment option for your condition. This might include surgery.

Are HIDA Scans Safe?

A HIDA scan does expose you to radiation, but the risk of any side effects from it is small. The amount of radiation you will be exposed to during the exam is about the same amount of background radiation you are exposed to in a year.

A HIDA scan carries a small risk for people who are pregnant or breastfeeding. Because of this, the scan is usually delayed in pregnancy and while breastfeeding unless necessary.

There is also a slight chance for an allergic reaction to the tracer’s material, but this is very rare. 

A Quick Review

HIDA scans are generally considered safe and are important to confirm the diagnosis of some diseases of the gallbladder, bile ducts, and liver. The test is performed by injecting radioactive tracers that help visualize the organs and how well they work. A scanner then takes images of your organs and ducts as the tracer makes its way through your system. A HIDA scan usually takes about an hour. Before the test, your healthcare provider will give you instructions about fasting and stopping any medication. After the test, your provider will talk with you about their findings and, with your symptoms and other imaging test results, to which condition it all points. They will then discuss your next steps as far as treatment.