A hepatobiliary scan, also known as a HIDA scan or cholescintigraphy, is a diagnostic imaging procedure. It uses a small amount of a radioactive tracer to evaluate the function of the liver, gallbladder, bile ducts, and small intestine.
Why a Hepatobiliary Scan is Performed
It commonly diagnoses gallbladder inflammation (cholecystitis), which often causes severe abdominal pain. The scan also identifies blockages in the bile ducts that prevent bile flow, or evaluates complications after surgery, such as bile leaks. It helps determine how well the liver produces and secretes bile, and can assess the function of a liver transplant or the effectiveness of a biliary stent.
Preparing for Your Scan
Preparing for a hepatobiliary scan involves specific instructions for accurate results. You will need to fast for at least four hours before the scan. Inform your medical team about any medications you are taking, as some, like opioid pain relievers, can affect bile flow and may need to be temporarily stopped. If you are pregnant or breastfeeding, inform your healthcare provider, as these conditions might require special precautions or a postponement of the scan.
What Happens During the Scan
During a hepatobiliary scan, you will lie on an imaging table, usually on your back. A healthcare professional will insert a small needle into a vein, typically in your arm, to inject the radioactive tracer. This tracer then travels through your bloodstream to your liver, where it is absorbed by bile-producing cells and excreted into the bile. A special camera, called a gamma camera, is positioned over your abdomen to capture images as the tracer moves through your liver, into your gallbladder, and through the bile ducts to your small intestine.
The imaging process can take anywhere from one to four hours, depending on how quickly the tracer moves through your system and whether additional images are needed. It is important to remain as still as possible during this time to ensure clear images. In some cases, a medication such as cholecystokinin (CCK) might be administered to stimulate your gallbladder to contract and release bile, which helps assess its function. This may cause mild abdominal cramping.
Understanding Your Scan Results
After the scan, a radiologist, a medical doctor specializing in interpreting medical images, will analyze the pictures to understand how the tracer moved through your biliary system. A normal finding indicates the radioactive tracer moved freely from your liver into your gallbladder and then into your small intestine. Abnormal results can suggest issues like a blockage or inflammation if the tracer does not appear in the gallbladder, or if its movement is slow. If the gallbladder does not contract adequately after stimulation, it might suggest a problem with its function. These interpretations are provided in a report to your referring physician, who will discuss the findings with you and determine the next steps for diagnosis or treatment.
Safety Considerations
Hepatobiliary scans involve the use of a small amount of radioactive material, but the radiation exposure is generally considered low, comparable to that of a standard X-ray or a head CT scan. The radioactive material quickly loses its activity and is naturally eliminated from the body through urine and stool, typically within a day or two. To help with this elimination, you may be advised to drink plenty of fluids after the scan. While rare, potential side effects can include minor bruising at the injection site or, very infrequently, an allergic reaction to the tracer.