A renal scan is a nuclear medicine exam in which a small amount of radioactive material (radioisotope) is used to measure the function of the kidneys.

The specific type of scan may vary, depending on the patient's specific needs. This article provides a general overview.

A renal scan is similar to a renal perfusion scintiscan. It may be done along with that test.

You will be asked to lie on the scanner table. The health care provider will place a tourniquet or blood pressure cuff to the upper arm, which creates pressure and enlarges your arm veins. The inner elbow is scrubbed with numbing medicine (antiseptic) and a small amount of radioisotope is injected into a vein. The specific radioisotope used may vary, depending on the kidney function that is being studied.

The pressure on the upper arm is released, which allows the radioactive material to travel through the bloodstream. The kidneys are scanned a short time later. Several images are taken, each lasting 1 or 2 seconds. The total scan time takes about 30 minutes to 1 hour.

A computer analyzes the images and provides detailed information about particular kidney functions (such as how much blood the kidney filters over time).

After the scan, no recovery time is required. You may be asked to drink plenty of fluids and urinate frequently to help remove the radioactive material from the body.

Tell your health care provider if you take any nonsteroidal anti-inflammatory drugs (NSAIDs) or blood pressure medications, as some could interfere with the exam.

You may be asked to drink additional fluids before the scan.

You must sign a consent form.

You will be asked to wear a hospital gown. Remove jewelry, dentures, and metallic objects before the scan.

There is a sharp prick when the isotope is injected into the vein. You do not feel the isotope. You do not feel the scan, although the table may be hard or cold. You will need to lie still during the scan.

A renal scan reveals the size, position, shape, and function of the kidneys. It is particularly useful when a person is sensitive or allergic to the contrast (dye) material used in an IVP or other x-rays, or when they have reduced kidney function.

A renal scan is commonly performed after a kidney transplant to check kidney function and to look for signs of transplant rejection.

It may also be done on those with high blood pressure to check kidney function.

Abnormal results are a sign of reduced kidney function. This may be due to:

• Acute or chronic kidney failure
• Complications of a kidney transplant
• Glomerulonephritis

Additional conditions under which the test may be performed:

• Acute arterial occlusion of the kidney
• Acute bilateral obstructive uropathy
• Bilateral hydronephrosis
• Carcinoma of the renal pelvis or ureter
• Chronic bilateral obstructive uropathy
• Complicated UTI (pyelonephritis)
• Injury of the kidney and ureter
• Pyelonephritis; acute
• Renovascular hypertension

There is a slight amount of radiation from the radioisotope. Most of this radiation exposure occurs to the kidneys and bladder as the isotope is removed from the body. Virtually all radiation is gone from the body in 24 hours. However, because of the slight exposure to radiation, caution is advised if you are pregnant or breastfeeding.

Extremely rarely, a person will exhibit an allergic reaction to the radioisotope, which may include severe anaphylaxis.

Risks related to a needle stick include:

• Bleeding
• Infection

Problems with the kidney structure may lead to an inaccurate reading of the scans, since results are calculated based on normal kidney size and shape.