Scans may need to be repeated over 1 or 2 days to detect gastrointestinal bleeding.
An RBC nuclear scan uses small amounts of radioactive material to mark (tag) red blood cells (RBCs). Your body is then scanned to see the cells and track how they move through the body.
How the Test is Performed
The procedure for this test may vary a little. This depends 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. The cells are 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. The medicine allows 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 right away or after a delay. For the scan, you will lie on a table under a special camera. The camera detects the location and amount of radiation given off by the tagged cells.
A series of scans may be done. The specific areas scanned depend on the reason for the test.
How the Test will Feel
You may feel a little pain when the needle is inserted to draw blood or to give the injection. 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.
How to Prepare for the Test
You will need to sign a consent form. You put on a hospital gown and take off jewelry or metallic objects before the scan.
A normal exam shows no rapid bleeding from the gastrointestinal tract.
Slight risks from having blood drawn include:
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
You will be exposed to a small amount of radiation from the radioisotope. The materials break down very quickly. Almost all radioactivity will be gone within 1 or 2 days. The scanner does not give off any radiation.
Most nuclear scans (including an RBC scan) are not recommended for women who are pregnant or breastfeeding.
What Abnormal Results Mean
There is active bleeding from the gastrointestinal tract.
Why the Test is Performed
This test is most often done to find the site of bleeding. It is done in people who have blood loss from the colon or other parts of the gastrointestinal tract.
A similar test called a ventriculogram may be done to check heart function.
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Kovacs TO, Jensen DM. Gastrointestinal hemorrhage. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 135.
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