Three common reasons for having a Renal Scan are to evaluate how well your kidneys are working, to determine whether you have an obstructed kidney, and to investigate whether your high blood pressure is being caused by your kidneys. We use a different test to evaluate each problem--a Renal Scan with GFR, a Diuretic Renal Scan, and a Captopril Renal Scan respectively. Each test is essentially the same as the other except for the preparation before the test. If you have any questions specific to your history don't hesitate to ask the technologist or your physician.
You will be injected with a small amount of radioactivity into a vein in your arm. This injection is no more traumatic than a routine blood test. You will not feel dizzy or nauseous from the radioactivity. The amount of radioactive exposure you will receive is similar to a routine chest X-ray. Please let us know if you are pregnant.
The radioactive tracer accumulates in your kidneys and then is excreted into your bladder within 20 minutes. If your kidneys are functioning normally, the rate of excretion, or GFR (Glomerular Filtration Rate), is about 125 ml/minute. We take pictures of your kidneys with a Gamma Camera.
Renal Scan with GFR - This test is the basic test and takes about 30-40 minutes to complete.
Diuretic Renal Scan - With this test we are looking to see if your kidneys are obstructed. Our physician will give you a diuretic (Lasix) 15 minutes prior to starting the test. The full test is about an hour long.
Captopril Renal Scan - With this test we are looking to see if your kidneys are causing your high blood pressure so we will give you Captopril orally one hour prior to the test. A diuretic will be administered 15 minutes prior to the test. Thus this test takes from 1½ to 2 hours.
For all three tests you may need an IV set up in your arm and you will be required to sit upright for twenty minutes without moving. The Renal Scan with GFR and Diuretic Renal Scan involve no preparation.
For the Captopril Renal Scan, you should be off all ACE Inhibitors, and fasting 4 hours prior to the test. Your physician should decide which medication to stop and for how long.