ADAM Health Encyclopedia

RBC nuclear scan

Definition

An RBC nuclear scan is a group of tests using small amounts of radioactive material to mark (tag) red blood cells (RBCs). The body is then scanned to detect the location and flow of the tagged RBCs.

See: Nuclear ventriculography

Why the Test is Performed

This test is most often done to locate the site of bleeding in patients who have blood loss from the colon or small bowel.

A variation on this test may be performed to check the function of the heart (ventriculogram).

How the Test is Performed

The exact procedure may vary slightly depending on the reason for the scan.

The RBCs are tagged with radioisotope in 1 of 2 ways.

The first method involves removing blood from a vein. The red blood cells are separated from the rest of the blood sample and then mixed with the radioactive material. The cells with the radioactive material are considered "tagged." A short time later the tagged RBCs are injected into one of your veins.

The second method involves an injection of medicine that will allow the radioactive material to attach to your red blood cells. The radioactive material is injected into a vein 15 or 20 minutes after you receive this medicine.

Scanning may be done immediately or after a delay. You will lie on a table underneath a special camera that detects the location and amount of radiation given off by the tagged cells.

A series of scans may be performed. The specific areas scanned depend on the reason for the test.

How to Prepare for the Test

You must sign a consent form. You will wear a hospital gown. Remove jewelry or metallic objects before the scan.

How the Test Will Feel

When the needle is inserted to draw blood or to give the injection, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

The x-rays and radioactive material are painless. Some people may have discomfort from lying on the hard table.

Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Extremely rarely, a person may experience an allergic reaction to the radioisotope. This may include anaphylaxis if the person is extremely sensitive to the substance.

There is a very slight exposure to radiation from the radioisotope. The radiation is minimal, and the materials "decompose" (are no longer radioactive) in a very short time. Virtually all radioactivity is gone within about 12 hours. There are no documented cases of injury from exposure to radioisotopes. The scanner only detects radiation -- it does not give off radiation.

Most nuclear scans (including an RBC scan) are not recommended for women who are pregnant or breastfeeding.

Considerations

Scans may need to be repeated over 1 or 2 days to detect gastrointestinal bleeding.

Normal Results

A normal exam shows the patient is not bleeding rapidly from the intestines.

What Abnormal Results Mean

The radiologist and the attending physician will determine abnormalities based on the scan findings. This scan is most commonly used to determine the site of bleeding, particularly bleeding within the gastrointestinal tract.