RBC (nuclear) scan

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 also nuclear ventriculography).

How the test is performed 
The exact procedure may vary slightly depending on the reason for the scan (the suspected problem).

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

First, a sample of blood may be withdrawn from the person in the standard venipuncture method (similar to getting a sample for a blood test). In the laboratory, the RBCs are separated from the rest of the blood components and mixed with the radioisotope. A short time later these “tagged” RBCs are reinjected into a vein.

The second method involves injection of a medication that “sensitizes” the RBCs in the body, which is a complex chemical reaction that permits the RBCs to “accept” the radioisotope (attach the isotope to the cell membrane). The isotope is injected into a vein 15 or 20 minutes later.

Scanning may be performed immediately, after a delay, or a series of scans may be performed. The whole body or only particular locations may be scanned depending on the indications for the test. The person is asked to lie on a table while the scanner detects the location and amount of radiation emitted by the tagged RBCs.

How to prepare for the test 
You must sign a consent form. You will wear a hospital gown, and be asked to remove jewelry or metallic objects before the scan.

For infants and children:
The preparation you can provide for this test depends on your child’s age and experience. For specific information regarding how you can prepare your child, see the following topics:

How the test will feel 
There will be a sharp prick from the needles used for blood withdrawal and/or injection(s). You will not feel the radioisotope and the imaging, but the table may be cold or hard. You must lie still during the scan.

Why the test is performed 
Most often it is used to evaluate blood-flow patterns (nuclear ventriculography), or to locate the site of gastrointestinal bleeding. It may also be used to look for hemangioma within the liver. Occasionally, it is used to evaluate the rate of blood loss in some anemias, or to evaluate blood vessel obstructions.

Normal Values
A normal value indicates no RBCs in unusual areas (no sites of bleeding), and normal blood-flow patterns.

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. An RBC scanning is also used as part of nuclear ventriculography and other scans.

What the risks are
Risks are essentially the same as for X-rays (radiation) and intravenous injection or blood sampling.

There is a very slight exposure to radiation from the radioisotope. The radiation is minimal, and the materials “decompose” (become 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 emit any radiation.

However, because of the slight radiation exposure, most nuclear scans (including an RBC scan) are not recommended for women who are pregnant or breast feeding (the radioisotope may be excreted in breast milk).

There is a minor risk that occurs whenever the body is penetrated (such as during blood sampling or injection of materials). This risk mainly involves the chance for infection or bleeding from the site. The risk for an RBC scan is no greater than when blood is sampled or material is injected into a vein for other reasons.

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.

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

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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