Elsevier

Surgery

Volume 126, Issue 6, December 1999, Pages 1023-1029
Surgery

American Association of Endocrine Surgeons
The 20% rule: A simple, instantaneous radioactivity measurement defines cure and allows elimination of frozen sections and hormone assays during parathyroidectomy

Presented at the 20th Annual Meeting of the American Association of Endocrine Surgeons, New Haven, Conn, May 2-4, 1999.
https://doi.org/10.1067/msy.2099.101578Get rights and content

Abstract

Background: Although primary hyperparathyroidism is a physiologic disease, surgeons rely on anatomical characteristics (gross and histologic) to determine appropriate operative decisions. After the development of radioguided parathyroidectomy, we hypothesized that the amount of radioactivity contained within resected tissue would be the only information needed to establish the nature of the tissue and to determine a cure for the disease. Methods: A total of 1290 tissue specimens were obtained from 345 patients who had sporadic primary hyperparathyroidism. Ex-vivo radioactivity, in counts per second, was measured in parathyroid and other tissues within 3.5 hours of sestamibi injection. Background radioactivity was measured after tissue excision, and ratios were calculated. Results: Lymph nodes, normal parathyroids, and fat never contained more than 2.2% of background radioactivity, whereas thyroid and hyperplastic parathyroids contained 5.5% and 7.5%, respectively, and never more than 16%. In contrast, adenomas contained 59% ±9% of background radioactivity (P < .000001 vs all other tissues), with a range of 18% to 136%. Conclusions: Radioactive ratios are an instantaneous measure of metabolic activity, thereby determining parathyroid function. Any excised tissue containing more than 20% of background radioactivity in a patient with a positive sestamibi scan result is a solitary parathyroid adenoma. This alleviates the need to identify other glands, obtain frozen sections, or measure serum parathyroid hormone levels intraoperatively. (Surgery 1999;126:1023-9.)

Section snippets

Patients

Between February 1997 and March 1999, 345 consecutive patients referred to the University of South Florida with primary sporadic HPT were entered into a prospective protocol. All underwent a parathyroidectomy while they were radioactive, after a systemic injection of 99Tc-labeled sestamibi. Patients with secondary hyperparathyroidism and those with familial forms of this disease were not included.

Sestamibi scanning

All patients were injected with 20- to 25-mCu 99Tc sestamibi between 1.5 and 3.5 hours prior to

Outcome and follow-up

With 100% follow-up (mean, 10.8 months; range 2-24 months), 342 (99.5%) patients had normal serum calcium and parathyroid hormone levels, including all 300 undergoing a MIRP.

Comparisons of radioactive ratios with permanent histology

Comparisons of radioactive ratios with tissue histology and follow-up postoperative laboratory values showed that fat, lymph nodes, and normal parathyroids never contained more than 2.2% of background radioactivity (Table). Normal thyroid tissue and hyperplastic parathyroid glands contained slightly more radioactivity

Discussion

HPT is a physiologic disease based on cellular hyperfunction with its attendant parathyroid hormone overproduction within 1 or more parathyroid glands. Until very recently, surgeons have treated this disease and concluded the operation by surgically removing enlarged or even normal-sized glands based purely on how they look to the naked or magnified eye. This has led to the common practice of performing multiple frozen sections during the course of a parathyroid operation, even when the surgeon

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  • Cited by (0)

    James Norman, MD, University of South Florida, Department of Surgery, P.O. Box 1289, Tampa General Hospital, Tampa, FL 33601.

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