A renal scan is a nuclear medicine examination that uses small amounts of radioactive materials (radioisotopes) to measure the function of the kidneys.

The process outlined below is a description of how a typical renal scan may go -- but the details my vary from place to place and according to a person's specific needs. A renal scan is similar to (and in fact, may be a continuation of) a renal perfusion scintiscan.

You will be asked to lie on the scanner table. Pressure (from a tourniquet or blood pressure cuff) is applied to the upper arm, which distends the veins of the arm. The inner elbow is scrubbed with antiseptic, and a small amount of radioisotope is injected into a vein (the radioisotope used may vary depending on the portion of kidney function that is of particular interest in the study).

The pressure on the upper arm is then released, which allows the isotope to travel through the bloodstream as a small, concentrated "package." A short time later, the kidneys are scanned. Several images are taken, each lasting 1 or 2 seconds, with the total scan time about 30 minutes to 1 hour. The images are analyzed by a computer after the scan is completed and can give detailed information about particular kidney functions (such as glomerular filtration rate, which reflects 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 excrete the radioactive material from the body.

There is usually no need for fasting, special diets, or preliminary medications. Discuss with your health care professional any nonsteroidal anti-inflammatory drugs (NSAIDs) or blood pressure medications you are currently taking to see if they will interfere with the exam. You may be asked to drink additional fluids before the scan.

You must sign a consent form. You will 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.

The test evaluates the size, position, shape, and function of the kidneys. A renal scan is particularly useful when there is a known sensitivity to the contrast media used in an IVP or other X-rays, or when there is underlying kidney insufficiency (reduced kidney function). Renal scan is commonly used after a kidney transplant to evaluate kidney function and to look for signs of transplant rejection.

A renal scan may be used to evaluate kidney function in people with hypertension.