What is a kidney scan?

A kidney scan is an imaging test that looks at your kidneys. Your healthcare provider can also see how well blood is flowing in your kidneys. A kidney scan is also called a renal scan or renal scintigraphy.

A kidney scan is a type of nuclear imaging test. This means that a tiny amount of a radioactive matter is used during the scan. The radioactive matter (radioactive tracer) is absorbed by normal kidney tissue. The radioactive tracer sends out gamma rays. These are picked up by the scanner to make a picture of your kidneys.

The areas of the kidneys where the radioactive tracer collects in greater amounts are called "hot spots." The areas that don't absorb the tracer and appear less bright on the scan image are referred to as "cold spots."

Why might I need a kidney scan?

A kidney scan can be done in several different ways to help look at kidney problems. All of these scans use a radioactive tracer.

You may need a kidney scan if your healthcare provider thinks you may have abnormal kidney function or may need surgery for a kidney problem.

Your healthcare provider may use the scan to see how well blood is flowing in your kidneys. You may need this if your provider thinks you have a blockage or narrowing in the blood vessels. This scan can also be used to diagnose:

• The amount of functioning kidney disease

• Blood flow to the kidneys

• Possible narrowing of the renal arteries

• Rejection of a transplanted kidney

Your healthcare provider may have other reasons to recommend a kidney scan. Talk with your healthcare provider about the reason for your scan.

What are the risks of a kidney scan?

The risk from the radioactive tracer is very low. The amount used in the test is very small. You may feel some slight discomfort when the tracer is injected. Allergic reactions to the tracer are rare, but they may happen.

Lying on the scanning table during the procedure may cause some discomfort or pain for certain people.

Tell your healthcare provider if you:

• Are allergic to or sensitive to medicines, contrast dyes, or latex.

• Are pregnant or think that you might be pregnant. The scan may not be safe for the fetus.

• Are breastfeeding. The tracer may contaminate your breastmilk.

You may have other risks. Discuss any concerns with your healthcare provider before the procedure.

Certain things may make a kidney scan less accurate. These include:

• Having radioactive tracer in your body from another recent nuclear medicine test

• Having barium in your digestive tract from a recent barium test

• Taking water pills (diuretics), or heart or blood pressure medicines. Talk with your healthcare provider about these.

How do I get ready for a kidney scan?

• Your healthcare provider will explain the procedure to you. Ask them any questions you have about the procedure.

• You may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if anything is not clear.

• You usually don't need to fast before the test. You also usually will not need medicine to help you relax (sedation).

• You may be asked to drink several glasses of water before the scan or take medicine.

• Tell your provider if you are:

  • Allergic to or sensitive to latex, medicines, contrast dyes, or iodine.

  • Pregnant or think you may be pregnant.

  • Taking medicine for high blood pressure. You may need to stop this medicine before the scan.

• Your provider may give you other instructions to get ready.

What happens during a kidney scan?

You may have a kidney scan as an outpatient or as part of your stay in a hospital. The way the test is done may vary depending on your condition and your healthcare provider's practices.

Generally, a kidney scan follows this process:

1. You will be asked to remove any jewelry, or other objects that may get in the way of the scan.

2. You will be asked to remove clothing. You will be given a gown to wear.

3. An IV (intravenous) line will be started in your hand or arm so that you can be given the radioactive tracer.

4. The tracer will be injected into your vein. The tracer will be allowed to collect in your kidneys for a short time. You might notice a slight metallic taste in your mouth but this should last only a few moments.

5. You may be asked to either lie down or sit upright on a scanning table. You will need to stay still during the scan. If you move, it may affect the quality of the scan. For a structural kidney scan, you will need to lie still during the entire test.

6. The scanner will be placed over the kidney area. The technologist will take a series of images until they can see the kidneys.

7. Depending on the type of scan done, the healthcare provider may give you a diuretic medicine or a different blood pressure medicine to take.

8. When the scan is done, the IV line will be removed and you will be helped up from the scanning table

The kidney scan is not painful. But you may have some discomfort or pain from lying still during the test, or the insertion of the IV. The technologist will use all possible comfort measures and do the scan as quickly as possible to minimize any discomfort or pain.

What happens after a kidney scan?

You should move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness.

You may be told to drink plenty of fluids and empty your bladder often for about 24 hours after the scan. This will help flush the radioactive tracer from your body.

The medical staff will check the IV site for any signs of redness or swelling. Tell your healthcare provider if you see any pain, redness, or swelling at the IV site after you go home. These may be signs of infection or another type of reaction.

You may go back to your usual diet and activities, unless your healthcare provider tell you otherwise.

Your healthcare provider may give you other instructions, depending on your situation.

Next steps

Before you agree to the test or the procedure make sure you know:

• The name of the test or procedure

• The reason you are having the test or procedure

• What results to expect and what they mean

• The risks and benefits of the test or procedure

• What the possible side effects or complications are

• When and where you are to have the test or procedure

• Who will do the test or procedure and what that person’s qualifications are

• What would  happen if you did not have the test or procedure

• Any alternative tests or procedures to think about

• When and how you will get the results

• Who to call after the test or procedure if you have questions or problems

• How much you will have to pay for the test or procedure