Definition of WBC scan:

A white blood cell (WBC) scan is an imaging test that uses a radioactive substance (called a tracer) to look for areas of infection or inflammation in the body.

See also: Nuclear scan

How the test is performed:

Blood will be taken from one of your veins. White blood cells are separated from the rest of the blood sample and then mixed with a small amount of a radioactive material (radioisotope) called indium-111. The cells with the radioactive material are considered "tagged."

About 2 or 3 hours later, the tagged white blood cells are returned to your body through injection into a vein. The tagged cells gather in areas of inflammation or infection.

Approximately 6 to 24 hours later, your body is scanned. You lie on a table. The scanner looks like an x-ray machine. It detects the radiation given off by the radioactive white blood cells. A computer converts the detected radiation into an image that can be viewed on a screen or recorded on film.

The scan takes about 1 or 2 hours. The scanner is usually located in a hospital, but often the test can be performed on an outpatient basis.

After the test is completed, no recovery time or special precautions are necessary. You typically may resume a normal diet, activity, and medications.

How to prepare for the test:

There is usually no need for fasting, special diets, or preliminary medications. You must sign a consent form. You will wear a hospital gown or be allowed to wear loose fitting clothing without metal fasteners. Remove jewelry, dentures, or metal before the scan.

The health care provider will occasionally request that antibiotics be stopped before this test.

How the test will feel:

There is a sharp prick from the needle during blood sampling and again when the blood is returned to you. The scan itself is painless, although the table that you are asked to lie on may be hard or cold. You do not feel the radioactive material.

Why the test is performed:

WBC scan is most often done when your doctor suspects a hidden infection. It is particularly useful for suspected infection or inflammation within the abdomen.

This test may be recommended if you have suspected pyelonephritis, abscess, osteomyelitis , or unexplained fever, particularly after surgery.