Type of test Nuclear scan
Normal findings
No signs of WBC localization outside the liver or spleen
Test explanation and related physiology
This test is based on the fact that WBCs are attracted to an area of infection or inflammation. When a patient is suspected of having had infection or inflammation yet the site cannot be localized, the injection of radiolabeled WBCs may identify and localize the area of inflammation or infection. This is especially helpful in patients who have a fever of unknown origin, suspected occult intraabdominal infection, or suspected (yet radiographically inapparent) osteomyelitis. The scan can differentiate infectious from noninfectious processes. For example, it is used to indicate whether an abnormal mass (e.g., a pancreatic pseudocyst) is infected. Areas of noninfectious inflammation (e.g., inflammatory bowel disease) also take up radiolabeled WBCs.
This scan requires drawing blood from the patient, separating out the WBCs, labeling the WBCs with technetium or indium, and reinjecting them back into the patient. Imaging of the whole body 4 to 24 hours later may show an area of increased radioactivity suggestive of accumulation of the radiolabeled WBCs in an area of infection or inflammation.
Procedure and patient care
Before
* Explain the procedure to the patient. See p. xviii for radiation exposure and risks.
* Assure the patient that he or she will not be exposed to large amounts of radioactivity because only tracer doses of the iso tope are used.
* Tell the patient that no preparation or sedation is required.
During
• Note the following procedural steps:
1. Approximately 40 to 50 mL of blood is withdrawn from the patient, and the WBCs are extracted from the rest of the blood cells. The WBCs are suspended in saline and tagged with 99mtechnetium (99mTc) or 111indium (111In) lipid-soluble product.
2. The tagged WBCs are reinjected into the patient.
3. At 4, 24, and 48 hours after injection, a gamma ray detector/camera is placed over the body.
4. The patient is placed in supine, lateral, and prone positions so that all surfaces of the body can be visualized.
5. The radionuclide image is recorded on film.
After
* Inform the patient that because only tracer doses of radioisotopes are used, no precautions need to be taken against radioactive exposure.
Abnormal findings
• Infection (e.g., abscess or osteomyelitis)
• Inflammation (e.g., inflammatory bowel disease, arthritis)
