A HIDA (hepatobiliary iminodiacetic acid) scan is an imaging procedure that provides a view of the liver, gallbladder, bile ducts, and small intestine. This test helps medical professionals assess the function of the gallbladder and observe the flow of bile through the biliary system. By tracking a radioactive tracer, the scan can identify potential issues within these organs. It offers insights into how effectively the liver produces bile, how the gallbladder stores and releases it, and whether there are any obstructions in the bile ducts.
Preparing for Your HIDA Scan
Preparing for a HIDA scan involves specific steps to ensure accurate results. Patients typically need to fast for four to six hours before the procedure. This fasting period is important as it allows the gallbladder to be in a resting state, optimizing its visualization during the scan. Patients may be allowed to drink clear liquids during this time.
It is important to discuss all medications and supplements with the healthcare provider beforehand. Some medications, particularly opioids, might interfere with the accuracy of the scan results and may need to be temporarily stopped, often for at least six hours prior. Certain antacids can also affect the scan, so a doctor’s guidance on medication adjustments is necessary.
For the scan, patients are usually asked to change into a hospital gown. It is advisable to leave jewelry and other metal accessories at home or remove them before the procedure, as these items can interfere with the imaging equipment.
What Happens During the HIDA Scan
Upon arrival for a HIDA scan, patients will typically be asked to change into a medical gown. They will then lie on their back on an exam table. A healthcare professional will insert an intravenous (IV) catheter, usually into a vein in the hand or arm, to administer the radioactive tracer.
The tracer, technetium-99m (99mTc-HIDA), travels to the liver, where it is absorbed by bile-producing cells and then excreted into the biliary system. A special camera, known as a gamma camera or nuclear medicine scanner, is positioned over the abdomen to detect the energy emitted by the tracer. This camera captures images as the tracer moves from the liver, through the bile ducts, into the gallbladder, and into the small intestine.
Patients must remain still during the imaging process to ensure clear and accurate pictures. The technologist may ask the patient to change positions periodically to obtain different views. The typical duration of a HIDA scan can range from 60 to 90 minutes, though it may extend to several hours or even involve delayed imaging up to 24 hours later if more detailed observation is needed.
During the scan, a medication called cholecystokinin (CCK) may be administered. CCK stimulates the gallbladder to contract and release bile, which helps assess its emptying function, known as the gallbladder ejection fraction. Patients might experience mild abdominal cramping or nausea after CCK administration, which is a normal response as the gallbladder contracts. In some cases, morphine may also be given to enhance the visibility of the gallbladder.
Understanding Your HIDA Scan Results
A “normal” result indicates that the radioactive tracer moved freely from the liver, filled the gallbladder, and then passed into the small intestine. This pattern suggests proper bile flow and gallbladder function.
“Abnormal” results can point to various conditions affecting the biliary system. If the tracer does not appear in the gallbladder within a certain timeframe, typically four hours, it may indicate acute cholecystitis, which is sudden inflammation of the gallbladder, often caused by a blockage in the cystic duct. This non-visualization signifies that bile is unable to enter the gallbladder.
A slow movement of the tracer through the bile ducts or into the small intestine can suggest a blockage or obstruction, or a problem with liver function. If the scan reveals a low gallbladder ejection fraction after stimulation with CCK, it indicates that the gallbladder is not contracting effectively. A normal ejection fraction is generally considered above 35% to 38%, with lower values possibly indicating chronic cholecystitis or gallbladder dysfunction.
Chronic cholecystitis involves repeated attacks of inflammation, often due to intermittent blockages. The HIDA scan can also identify biliary dyskinesia, a condition where the gallbladder doesn’t empty properly, even without stones. If the tracer is detected outside the biliary system, it may signal a bile leak.
After Your HIDA Scan
After a HIDA scan, patients can generally resume their normal activities immediately. The small amount of radioactive tracer injected during the procedure naturally leaves the body. Most of the tracer will be eliminated through urine and stool within 24 to 48 hours. Drinking plenty of fluids after the scan can help facilitate this process.
Results from a HIDA scan are usually communicated by the referring doctor within a few days. Patients should discuss these results with their healthcare provider, who will explain what the findings mean for their specific situation and determine any necessary follow-up care or treatment plans.