A HIDA scan (hepatobiliary iminodiacetic acid scan) with calculation of ejection fraction is done to evaluate the function of the gallbladder. In this test, we see how well the gallbladder empties. A gallbladder which empties poorly can cause pain, nausea and symptoms similar to a gallbladder attack.
How is a HIDA scan done?
This test is done by injecting a radioactive pharmaceutical into the vein. The pharmaceutical is taken up by liver cells and is excreted into the bile ducts, the gallbladder and intestine. The pharmaceutical gives off radiation which is imaged with a camera while it travels through the body.
The gallbladder usually fills with the radioactive pharmaceutical when there is gallbladder dysfunction but does not empty well. Often the gallbladder is otherwise normal without sludge or stones on ultrasound.
We administer cholecystokinin which is a hormone that stimulates bile release or give the patient a fatty meal after we see that the gallbladder has filled. We image for an additional hour and see how much of the radiopharmaceutical has left the gallbladder.
We calculate this emptying of the gallbladder as a percentage. Usually 40% or greater is normal and under 40% represents gallbladder dysfunction. The patients with low gallbladder ejection fraction are often treated with gallbladder removal and experience symptoms relief.
A low gallbladder ejection fraction can also be seen with chronic cholecystitis. This is a chronic inflammation of the gallbladder. On ultrasound, the gallbladder will often be abnormal with sludge, stones, and wall thickening. Patients will sometimes have history of biliary colic or gallbladder attacks.
Chronic cholecystitis on a nuclear medicine HIDA scan will show delayed filling of the gallbladder with the radiopharmaceutical. This mean that the gallbladder will fill between 1-4 hours instead of during the first hour. In acute cholecystitis, the gallbladder will not fill at all after 4 hours. The patient will also have a low gallbladder ejection fraction. Treatment is with surgical removal of the gallbladder.
A HIDA scan with addition of gallbladder ejection fraction is a useful test for patients who have normal imaging of the gallbladder like ultrasound but have symptoms which are thought to be related to the gallbladder. These patients will often have a low gallbladder ejection fraction. The gallbladder will not empty as well following CCK administration or a fatty meal. Treatment is often surgical.