HIDA Scan

What is a HIDA scan?

A HIDA scan (hepatobiliary iminodiacetic acid scan) is an imaging procedure that uses an injected chemical called a radioactive tracer (radiotracer) and a scanning camera to evaluate your gallbladder. The scan is performed in the department of nuclear medicine in radiology.

More specifically, the HIDA scan tracks the flow of bile from your liver to your small intestine. This is known as the biliary system.

Your liver makes bile (digestive fluid) that helps your body break down the fat in the food you eat. Certain ducts (biliary ducts) carry bile from your liver to your gallbladder for storage. Your gallbladder is a small sac under your liver on your right side at the level of your lower ribs. When you eat food, your gallbladder contracts (squeezes) and releases stored bile through ducts into the first part of your small intestine (the duodenum) to help break down the fats.

If any part of this process isn’t working properly, it can cause certain symptoms and conditions, which a HIDA scan can help diagnose.

Other names for a HIDA scan include cholescintigraphy and hepatobiliary scintigraphy.

What can be diagnosed with a HIDA scan?

Healthcare providers use a HIDA scan to help diagnose and evaluate the following conditions:

• Acute cholecystitis (gallbladder inflammation): This condition comes on suddenly and causes severe pain in your right upper belly, and may be associated with other symptoms, including fever. About 90% of people with acute cholecystitis have gallstones that cause biliary duct blockage.
• Chronic cholecystitis: This condition means you’ve had repeated attacks of inflammation and pain in your gallbladder. Pain tends to be less severe and there are often multiple episodes of discomfort. The repeated attacks are usually caused by gallstones blocking the cystic duct intermittently.
• Sphincter of Oddi dysfunction: In this condition, the sphincter (a muscle that opens and closes) that regulates the flow of bile and pancreatic juice (enzymes) doesn’t open when it should, causing a backup of digestive juices. This sphincter is called the sphincter of Oddi. This condition can cause severe pain.
• Biliary atresia: This is a condition in newborn babies in which bile is blocked from moving from their liver to their small intestine. It’s a rare but serious cause of newborn jaundice and can cause irreversible liver damage if it’s not surgically shunted within the first two to three months of life.
• Biliary leak: This condition happens when bile leaks out of any of the ducts that transport bile to your small intestine. When bile leaks out of your bile ducts, the surrounding area becomes painfully inflamed and can get infected. It usually happens after gallbladder surgery, after trauma (injury) or after liver transplantation.

When would I need a HIDA scan?

Healthcare providers perform HIDA scans to evaluate conditions that affect liver cells, the ducts of the biliary system and your gallbladder.

Your provider may recommend a HIDA scan if you have any of the following symptoms:

• Severe abdominal pain, especially if the pain is on your right side: This may be caused by a sudden inflammation of your gallbladder called cholecystitis. This is the most common reason for needing a HIDA scan.
• Pain or fever following certain surgeries: If you’ve had gallbladder or upper gastrointestinal tract surgery or have received a liver transplant and are experiencing fever and pain, you may need a HIDA scan.
• Severe jaundice in newborns: This could be due to biliary atresia, which is a life-threatening condition.

You may also need a HIDA scan if you’ve had a biliary stent placed. A biliary stent (bile duct stent) is a thin, hollow tube that’s placed in the bile ducts. The stent holds the duct open if it’s been blocked or partly blocked. Your provider may request a HIDA scan to make sure the stent is working properly.

If you’ve had a liver transplant, you may need multiple HIDA scans to evaluate the function of your liver after the transplant surgery.

Who performs a HIDA scan?

Three medical professionals are involved in performing a HIDA scan to calibrate the scanning equipment, provide radiopharmaceuticals (radiotracers) and interpret the results of the scan. These providers include:

• A board-certified physician in either nuclear medicine or nuclear radiology.
• A nuclear technologist.
• A medical physicist.

How does a HIDA scan work?

A HIDA scan (hepatobiliary iminodiacetic acid scan) uses small amounts of radioactive substances called radiopharmaceuticals or radiotracers that a healthcare provider typically injects into your bloodstream.

The radiotracer then travels through your liver and into your gallbladder and your small intestines. The radiotracer gives off energy in the form of gamma rays. Special cameras detect this energy and, with the help of a computer, create detailed pictures that show how your organs and tissues to evaluate their function.

How do I prepare for a HIDA scan?

Your healthcare team will give you specific instructions to prepare for a HIDA scan. Be sure to follow them. Here are some general guidelines to prepare for a HIDA scan:

• If you’re pregnant, think you might be pregnant or are breastfeeding, it’s important to tell your healthcare provider before undergoing a HIDA scan.
• Tell your healthcare team about any medications you’re taking, including vitamins and herbal supplements. Your provider may tell you to stop taking certain medications before your scan because they may interfere with the accuracy of the results.
• You should leave jewelry and accessories at home or remove them before the scan. These objects may interfere with the procedure.
• Tell your provider if you have a fear of closed or tight spaces before your exam begins since the scanning equipment needs to be positioned close to your body to get the best pictures. The camera is not a closed tube and is open on two sides. It’s usually positioned over your stomach and doesn’t cover your face.
• You’ll need to fast (not eat or drink anything except for water) for at least four hours before your HIDA scan. Your provider will let you know if you need to fast for longer.
• Newborn babies may need to be pretreated for three to five days prior to the scan, and the pediatric staff will give you instructions.

Do they put you to sleep for a HIDA scan?

HIDA scans don’t typically require anesthesia to put you to sleep (or to prevent pain). In fact, for some scans, you may need to move into different positions.

If you may have issues remaining still during the scan or if your newborn or child is getting the scan, you or your child may be given medicine (a sedative) that makes you relaxed and sleepy — but still awake —during the scan.

How long does a HIDA scan take?

A HIDA scan usually takes one to four hours. In some cases, you may need to return for additional imaging up to 24 hours after the first scan.

What should I expect during a HIDA scan?

A HIDA scan procedure can have slightly different steps depending on which part of your biliary system your healthcare provider is evaluating.

In general, you can expect the following during a HIDA scan:

• You’ll remove any clothing covering your belly, and you’ll have a medical gown to wear.
• You’ll lie on your back on an exam table.
• A nurse or technologist will likely insert an intravenous (IV) catheter into a vein in your hand or arm for the injection of the radiotracer.
• The technologist will place the scanning camera close over your belly.
• When imaging begins, the scanning camera will take a series of images. The camera may rotate around you or stay in one position. While the camera is taking pictures, it’s important to remain very still. This helps ensure the best quality of images.
• You may need to change positions in between images. Your technologist will let you know.
• After the technologist takes an initial series of images, they may give you a medication that causes your gallbladder to empty. This may cause cramping in your upper belly. As your gallbladder empties, they’ll take more images.
• Once the technologist has taken the necessary images, which may take up to four hours, the scan will be finished.

How painful is a HIDA scan?

The HIDA scan itself is painless. If you receive the radiotracer through an IV, you may feel a brief sting or pinch as your provider places the IV in your arm.

However, you may be in pain while undergoing a HIDA scan because of the condition your provider is trying to diagnose. For example, cholecystitis and sphincter of Oddi dysfunction often cause severe pain. And you may not be able to be on pain medication for the scan because some medications alter the function of your biliary system and would interfere with the accuracy of the test.

Opiates (like morphine and codeine), for example, need to be withheld for at least six hours before a HIDA scan.

What should I expect after a HIDA scan?

Depending on the reason for your HIDA scan, you may be able to go home or you’ll return to your hospital room.

Be sure to drink lots of fluids for the next 24 hours after your scan to help flush the radiotracer out of your body. Most of the radiotracer will leave your body through your urine or stool within a day.

Be sure to flush the toilet right after you use it, and wash your hands thoroughly with soap and water. The amount of radiation in the tracer is very small, so it isn't a risk for people to be around you after the scan.

If you’re breastfeeding, you’ll need to discard the milk you pump for 24 hours after the scan. This is because your breastmilk can have radiation in it from the radiotracer, which can harm your baby. You may wish to pump additional breast milk prior to the scan and safely store it or make alternate plans for your baby to receive nutrition for the one day after the scan.

What are the risks and side effects of a HIDA scan?

A HIDA scan has very few risks, including:

• Bruising at the injection site of the radiotracer.
• Small radiation exposure. During a typical HIDA scan, your radiation exposure is about the same amount of background radiation the average person experiences in a year.
• Possible allergic reaction to medications containing radiotracers used for the scan. This is very rare.

It’s important to tell your healthcare provider if you’re pregnant, think you might be pregnant or are breastfeeding. In most cases, providers don’t perform nuclear medicine tests, such as the HIDA scan, on someone who's pregnant due to potential harm to the developing fetus.

Nuclear medicine imaging, which includes a HIDA scan, provides unique information that providers can’t often get using other imaging procedures, such as ultrasound. Because of this, the benefits of a HIDA scan far outweigh the risks if you're not pregnant.

When should I know the results of the HIDA scan?

A radiologist will interpret the images of the HIDA scan, write a report and share the results with your healthcare provider. Your provider will then share the results with you. This process usually takes less than 24 hours.

What type of results do you get from a HIDA scan?

The results report for your HIDA scan may have different information depending on why you needed the scan. In general, the report will detail how the radiotracer flowed through your biliary system.

Healthcare providers use the results of a HIDA scan and other testing, such as blood tests, to make a final diagnosis.

The possible report findings for a HIDA scan may include:

• Normal: The radiotracer moved freely from your liver into your gallbladder and small intestine.
• Slow movement of radiotracer: This may indicate that you have a blockage or obstruction or your liver isn’t functioning properly.
• No radiotracer seen in the gallbladder: This may indicate that you have acute cholecystitis (gallbladder inflammation) due to a blockage.
• Abnormally low gallbladder ejection fraction: The ejection fraction of your gallbladder is based on how much bile your gallbladder can release (eject) once it’s been stimulated with medication. The gallbladder ejection fraction is considered normal when it’s above 30% to 35%. An abnormally low number might indicate chronic cholecystitis.
• Radiotracer detected in other areas: If the scan reveals radiotracer outside of your biliary system, it might indicate a biliary (bile duct) leak.

It’s important to remember that your provider will explain the results to you, whatever they may be. Feel free to ask them questions.