Objective: To determine the utility of ultrasonography for the preoperative localization of enlarged parathyroid glands in primary hyperparathyroidism, and to compare this method with (99m)technetium sestamibi scintigraphy.
Design: The results of ultrasonography for localization of enlarged parathyroid glands were determined in 120 consecutive patients with primary hyperparathyroidism and compared with findings at surgery (n = 86) and with the results of (99m)technetium sestamibi scintigraphy (n = 99).
Patients: All patients had biochemically documented primary hyperparathyroidism based on elevated serum calcium and 'intact' parathyroid hormone measured by immunoassay. Patients with prior parathyroid surgery or secondary hyperparathyroidism were excluded.
Measurements: High-resolution ultrasonography was performed by a single observer. (99m)Technetium sestamibi scintigraphy was performed using early and delayed (2-h) views, and correlated with simultaneous thyroidal 123I uptake in most patients.
Results: Ultrasonography detected putative enlarged parathyroid glands in 92 of 120 unselected patients (77%). It correctly predicted surgical findings in 64 of 86 patients undergoing surgery (74%), including 61 of 72 patients with solitary eutopic parathyroid adenomas (84%), but only two of eight patients with solitary ectopic adenomas, and only one of six patients with multigland parathyroid disease. Sestamibi scintigraphy was positive in 87 of 99 unselected patients (88%), a higher proportion than ultrasonography (P < 0.05), reflecting superior sensitivity for the detection of ectopic parathyroid adenomas. For 74 patients undergoing parathyroid surgery who underwent both imaging tests there was no statistically significant difference between ultrasonography and sestamibi scintigraphy in ability to correctly predict surgical findings (74%vs. 82%, respectively) or in positive predictive value (93%vs. 90%, respectively). However, sestamibi scintigraphy was clearly more sensitive for ectopic parathyroid adenomas, providing correct localization in 8/8 cases. When one test was negative, testing with the second method was usually positive, improving the likelihood of a positive result to 98% when both tests were employed.
Conclusions: Ultrasonography can be a sensitive and accurate method for preoperative localization of enlarged parathyroid glands in primary hyperparathyroidism, comparable in overall utility to sestamibi scintigraphy. These results suggest that a strategy of initial testing with one or the other method, followed by the alternate imaging test if the first test is negative, would provide correct parathyroid imaging in most patients without prior parathyroid surgery.