section name header

Introduction ⬇

A metaiodobenzylguanidine (MIBG) scan is performed to identify sites of certain tumors, such as adrenal gland tumors, that produce excessive amounts of catecholamines. The adrenal gland is divided into two different components: cortex and medulla. The scope of adrenal imaging is limited to the medulla. Pheochromocytomas develop in cells that make up the adrenergic portion of the autonomic nervous system. A large number of these well-differentiated cells are found in adrenal medullas. Adrenergic tumors have been called paragangliomas when they are found outside the adrenal medulla, but many practitioners refer to all neoplasms that secrete norepinephrine and epinephrine as pheochromocytomas. Because the only definite and effective therapy is surgery to remove the tumor, identification of the site using adrenal gland imaging, CT, and ultrasound is an essential component of the treatment plan.

Procedure ⬆ ⬇

  1. Inject intravenously the radionuclide 131I- or 123I-MIBG.

  2. Obtain images at the healthcare provider’s discretion, usually 4 and 24 hours after injection.

  3. Advise the patient that imaging may take 2 hours.

  4. See Chapter 1 guidelines for safe, effective, informed intratest care.

Clinical Implications ⬆ ⬇

  1. More than 90% of primary pheochromocytomas occur in the abdomen.

  2. Pheochromocytomas in children often represent a familial disorder.

  3. Bilateral adrenal tumors often indicate a familial disease.

  4. Multiple extrarenal pheochromocytomas are often malignant.

  5. The presence of two or more pheochromocytomas strongly indicates malignant disease.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain an MIBG scan’s purpose, procedure, benefits, and risks.

  2. Give potassium iodine tablets or solution 1 day prior to the injection, the day of the injection, and 4 days post injection to prevent uptake of radioactive iodine by the thyroid.

  3. Refer to standard NMI pretest precautions.

  4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel appropriately about the need for possible follow-up tests. Follow-up tests include:

    1. Kidney and bone imaging to give further orientation to abnormalities discovered by MIBG scan

    2. CT scan if MIBG scan failed to locate the tumor

    3. Ultrasound of the pelvis if the tumor produces urinary symptoms

  2. Refer to standard NMI posttest precautions.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

Barium interferes with the test.

Reference Values ⬆

Normal

No evidence of tumors or hypersecreting hormone sites

Normal salivary glands, urinary bladder, and vague shape of liver and spleen can be seen.