Thallium-technetium isotope subtraction scanning in primary hyperparathyroidism.

Between January 1983 and March 1986, 75 consecutive patients underwent cervical exploration for primary hyperparathyroidism. Each patient had a thallium-technetium subtraction isotope scan of the neck performed preoperatively. Of 71 patients with technically satisfactory scans, 68 came to 'first-time' neck exploration while three underwent reoperation for persistent hypercalcaemia. At primary cervical operation 53 of the 68 patients each had a solitary adenoma as the cause of their hyperparathyroidism. In 28 (53%) of these individuals the scintigram accurately predicted the site of the parathyroid tumour ('helpful' scans). The technique was 'unhelpful' in 17 patients (32%) with false-positive scans and in eight patients (15%) with false-negative scans. There was a highly significant difference between the median weight of adenomas removed from patients with helpful scans (1.05 g) and that of adenomas retrieved from individuals with unhelpful scans (0.47 g), (P less than 0.001). Since 1 January 1985 we have adopted a policy of 'scan-directed' unilateral neck exploration for patients with hyperparathyroidism on the basis of solitary adenoma and in whom the isotope scan was positive. The mean operating time for these patients (n = 18, mean operating time 1.24 h) was significantly shorter than that for patients with unhelpful scans (n = 14, mean operating time 1.55 h, P less than 0.01) who were submitted to standard bilateral cervical operation. Subtraction scanning was helpful, in terms of localization of enlarged parathyroid glands, in only three of eight patients with multigland hyperplasia. The investigation was of positive help in locating the adenoma in two of three individuals submitted to cervical re-exploration for persistent hyperparathyroidism.