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 makes the test more accurate.
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. You will need 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 diuretic ("water pill") through a vein. This medicine also helps make the test more accurate.
You can return to normal activities right 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 medicine before the exam. Always talk to your health care provider before you stop any of your medicines.
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 told when you need to change positions.
There may be some discomfort as your bladder fills with urine during the exam. Tell the person conducting the exam if you must urinate before the scan is complete.
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. This is 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. A similar study that does not use an ACE inhibitor can be done to confirm the diagnosis.
If you are pregnant or nursing, your provider may want to postpone the test. There are certain risks involved with ACE inhibitors. Pregnant women should not take these medicines.
The amount of radioactivity in the injection is very small. Nearly all radioactivity 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.
This test may be less accurate in people who already have kidney disease. Talk to your provider to determine if this is the right test for you. Alternatives to this test are an MRI or CT angiogram.
Rottenberg G, Andi AC. Renal transplantation. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 6th ed. New York, NY: Elsevier Churchill Livingstone; 2014:chap 37.
Scott Miller, MD, urologist in private practice in Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.