A kidney scan is a nuclear scanning test that is done to evaluate kidney function.

During a kidney scan, a radioactive tracer substance is injected into a vein in the arm and then travels through the bloodstream to the kidneys. The tracer flows through the blood vessels in the kidneys. A special camera (gamma) takes pictures of the tracer in the kidneys. This helps show cell activity and function in the kidneys. Areas of the kidneys where the tracer shows up in higher-than-normal amounts, such as in some types of cancer, result in bright or "hot" spots in the pictures. Areas where the tracer does not show up appear as dark or "cold" spots. Cold spots can indicate narrowing or blockage of the blood vessels, pockets of fluid (cysts), some cancers, or pockets of infection (abscesses).

Two types of kidney scans can be done:

• A perfusion study can be done to evaluate the blood flow through the kidneys.
• A function study can be done to measure the amount of time it takes for the tracer to move through the kidney, collect in the urine, and drain into the bladder. See an illustration of the tracer in the kidneys and bladder.

These two types of kidney scans are often done at the same time.

A kidney scan may be done for people who are allergic to the special dye (contrast material) used for the kidney X-ray test called an intravenous pyelogram (IVP).

Why It Is Done

A kidney scan is done to:

• Check the blood flow through the kidneys. normal flow may mean narrowed renal arteries that can cause a type of high blood pressure called renovascular hypertension.
• See how a transplanted kidney is working.
• Evaluate the extent of kidney damage caused by an injury.
• Detect an obstruction in the kidney or ureter, such as from a kidney stone.
• Detect growths in the kidneys (rare).

How To Prepare

Before your kidney scan, tell your doctor if:

• You are or might be pregnant.
• You are breast-feeding. Use formula (discard your breast milk) for 1 to 2 days after the scan until the radioactive tracer has been eliminated from your body.
• You are taking any medications, especially blood pressure or heart medications.
• Within the past 4 days, you have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medication (such as Pepto-Bismol) that contains bismuth. Barium and bismuth can interfere with test results.
• You have had an X-ray test using contrast material in the last 48 hours. X-ray tests with contrast material may include an intravenous pyelogram (IVP) or abdominal computed tomography (CT) scan.

You may be asked to drink 2 to 3 glasses of water right before the scan.

You may be asked to sign a consent form before the test. Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).