You will be asked 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 will be given a a diuretic ("water pill") through a vein. This medicine also increases the test's accuracy.
You can return to normal activities immediately after the test. You should drink plenty of fluids to help remove the radioactive material from your body.
How to prepare for the test
You will be asked to drink plenty of water before the test.
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.
How the test will feel
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.
Why the test is performed
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.
What abnormal results mean
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.
What the risks are
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 persons with pre-existing kidney disease. Talk to your health care provider to determine if this test is appropriate for you. Alternatives to this test are an MRI or CT angiogram.
Rankin S. Renal parenchymal disease, including renal failure, renovascular disease and transplantation. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 39.
David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc. Louis S. Liou, MD, PhD, Chief of Urology, Cambridge Health Alliance, Visiting Assistant Professor of Surgery, Harvard Medical School.