A renal perfusion scintiscan is a nuclear medicine test that uses a small amount of a radioactive substance to create an image of the kidneys.

Before the scan, you will be asked to drink plenty of water so that you stay hydrated and to take a blood pressure medicine called an ACE inhibitor. The drug may be taken by mouth, or given through a vein (IV). The medicine increases the accuracy of the test.

You lie on the scanner table shortly after taking the medicine. The health care provider will inject a small amount of radioactive material (radioisotope) into one of your veins. Images of your kidneys are taken as the radioactive material flows through the arteries in the area. It is very important to remain still for the entire test. The scan takes about 30 minutes.

About 10 minutes after you receive the radioactive material, you be given a a diuretic ("water pill") through a vein. This medicine also increases the test's accuracy.

You can return to normal activities immediatley after the test. You should drink plenty of fluids to help remove the radioactive material from the body.

No special preparation is needed.

If you are currently taking an ACE inhibitor for high blood pressure, you may be asked to stop taking your medication before the examination. Always consult with your health care provider before stopping any medication.

You may be asked to wear a hospital gown. Remove all jewelry and metallic objects before the scan.

You may feel a small amount of pain when the needle is inserted.

You must remain still during the scan. You will be instructed by the technologist when to change positions.

There may be some discomfort as your bladder fills with urine during the examination. Inform the technologist if you must urinate before the completion of the scan.

The test evaluates blood flow to the kidneys. It is used to diagnose narrowing of the arteries that supply the kidneys, a condition called renal artery stenosis. Significant renal artery stenosis may be a cause of high blood pressure and kidney problems.

Blood flow to the kidneys appears normal.

Abnormal findings on the scan may be a sign of renal artery stenosis. This condition may be confirmed by doing a similar study that does not involve the use of an ACE inhibitor.

If you are pregnant or nursing, your health care provider may want to postpone the test to prevent exposing the baby to the medications and radioisotopes used. There are certain risks involved with ACE inhibitors. Pregnant women should not take such medicines.

The amount of radioactivity in the injection is very small, and virtually all activity is gone from the body within 24 hours.

Reactions to the materials used during this test are rare, but may include rash, swelling, or anaphylaxis.

Risks of a needle stick are slight but include infection and bleeding.

The accuracy of this test may be reduced in individuals with pre-existing kidney disease. You should talk to your health care provider to determine if this test is appropriate for you.

Victor RG, Kaplan NM. Systemic hypertension: mechanisms and diagnosis. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 40.