A parathyroid scan is obtained to localize parathyroid adenomas in clinically proven cases of primary hyperparathyroidism. It is helpful in demonstrating intrinsic or extrinsic parathyroid adenoma. 99mTc sestamibi, 123I capsules, or 201Tl, or a combination of these three (called dual-isotope subtraction imaging), can be administered prior to the scan. In children, the scan is performed to verify presence of the parathyroid gland after thyroidectomy.
Pregnancy is a relative contraindication. However, if primary hyperparathyroidism is suspected and surgical exploration is essential before delivery, the study may be performed.
For dual-isotope subtraction imaging:
Administer 123I. Four hours later, obtain images of the neck.
Inject 99mTc sestamibi without moving the patient; after 10 minutes, acquire additional images. Computer processing involves subtracting the technetium-visualized thyroid structures from the 123I accumulation with a parathyroid adenoma.
Alert patient that total examination time is 1 hour.
See Chapter 1 guidelines for safe, effective, informed intratest care.
Abnormal concentrations of the radiopharmaceuticals reveal parathyroid adenoma, both intrinsic and extrinsic, but cannot differentiate between benign and malignant adenomas.
Pretest Patient Care
Explain the purpose, procedure, benefits, and risks of a parathyroid scan.
Assess for the recent intake of iodine. However, this finding is not a specific contraindication to performing the study.
Palpate the thyroid carefully.
Refer to standard nuclear scan pretest precautions.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Refer to standard NMI posttest precautions.
Review test results; report and record findings. Modify the nursing care plan as needed.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
Recent ingestion of iodine in food or medication and recent tests with iodine contrast are contraindications and reduce the effectiveness of the study.