A HIDA scan is a medical imaging procedure that allows a doctor to check the function of your liver or gallbladder. The scan requires a patient to get an injection of a radioactive material, which the machine can pick up in the scan. The test shows if the bile from the liver travels to the gallbladder and the small intestine properly and can help diagnose diseases such as gallstones or obstructed gall ducts.
In healthy people, the liver produces a substance called bile. Humans absorb food through the gastrointestinal system, but fats in food cannot move freely through the intestinal wall, unlike water. Therefore, the body needs to produce a substance that emulsifies the fat to make it absorbable. Bile performs this function.
The gallbladder is a small sac attached to the liver. It stores the bile until it is required. When the body receives fats through food ingestion, the gallbladder releases the bile into the small intestine. Medical problems can arise if the liver, the gallbladder, or the ducts that control the movement of bile are affected by disease.
Hepatobiliary iminodiacetic acid scan is what HIDA scan stands for. The procedure involves a moving, scanning camera and a scan table, which the patient lies on. Fasting is necessary for at least two hours before the test.
The patient has to have an injection of a radioactive substance immediately prior to the scan. This radioactive injection passes out of the body through urination after a day or two, and the dosage of radiation is small compared to the daily dose of cosmic radiation, so it poses little risk to health. The radioactive chemical travels through the body and settles in the cells of the liver that produce the bile. Then, it moves outward to the small intestine with the bile.
Imaging with the HIDA scan takes from 40 minutes to an hour as the radioactivity makes its way through the gastrointestinal system. During this time, the patient remains still. The doctor then looks at the resulting images to see if the bile moves normally through the body or if there are any obstructions or other problems.
If the gallbladder shows no radioactive traces, then it may be inflamed in a condition known as cholecystitis. If the HIDA scan picks up radioactivity outside of the normal bile pathway, then there may be leaks present in the organs. An abnormally slow bile movement can indicate duct blockages or that the liver is not producing a healthy amount of bile.