Renal Scan

Overview

A renal scan is a nuclear scanning test that is done to evaluate kidney function.

During a kidney scan, a radioactive tracer substance is injected into a vein in the arm and then travels through the bloodstream to the kidneys. The tracer flows through the blood vessels in the kidneys. Areas of the kidneys where the tracer shows up in higher-than-normal amounts, such as in some types of cancer, result in bright or “hot” spots in the pictures. Areas where the tracer does not show up appear as dark or “cold” spots. Cold spots can indicate narrowing or blockage of the blood vessels, pockets of fluid, some cancers, or pockets of infection.

Two types of kidney scans can be done:

• A perfusion study can be done to evaluate the blood flow through the kidneys.
• A function study can be done to measure the amount of time it takes for the tracer to move through the kidney, collect in the urine, and drain into the bladder

These two types of kidney scans are often done at the same time.

A kidney scan may be done for people who are allergic to the contrast material used for the kidney x-ray test called an intravenous pyelogram (IVP).

Patient Prep

There is no preparation for this test.

Test Procedure

A renal scan is usually done by a nuclear medicine technologist. The scan pictures are usually interpreted by a radiologist or nuclear medicine specialist.

You will need to remove any jewelry that might interfere with the scan. You may need to take off all or most of your clothes; depending on which area is being examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.

The technologist cleans the site on your arm where the radioactive tracer will be injected. A small amount of the radioactive tracer is then injected. Medication to increase your urine output (a diuretic) may also be injected.

You may lie on your back on a table, stand, or sit upright. A large scanning camera will be positioned closely above your abdomen. After the radioactive tracer is injected, the camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your kidneys. You need to lie very still during each scan to avoid blurring the pictures. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.

For the kidney function study, a different tracer may be injected and a series of pictures will be taken every few minutes for 30 minutes. These images monitor flow of the tracer through the kidneys, into the ureters and, finally, into the bladder . As each picture is being taken, you must lie completely still. Occasionally, scans may be done while you are sitting upright or standing. In some studies, other medications such as captopril or a diuretic, may be given to help assess specific functions of the kidneys.

A chart called a renogram may be made using the information from the perfusion study scans by plotting the movement of the tracer through the kidneys and recording it on a graph. A series of chart recordings is then made based on the amount of tracer uptake in the kidneys over a period of time. These recordings provide information about different phases of blood flow and kidney function.

Another type of scan, called a static scan, also may be done several hours after a tracer is injected.

The renal scan usually takes about 1 to 2 hours but can last up to 4 to 5 hours depending on what function studies are done.

Test Results

It can take time for the test results and how long will depend on the reasons for the scan. Usually, a specialist in radiology examines the scan and sends a report to your physician, who reviews the results to you.