Ultrasonography in detection of single and multiple abnormal parathyroid glands in primary hyperparathyroidism: comparison with radionuclide scintigraphy and surgery

Background Among the parathyroid imaging techniques, ultrasonography (USG) has the advantage of convenience, easy availability and low cost. Objective To study the role of USG in localization (side and/or site) of abnormal parathyroid glands in primary hyperparathyroidism (PHPT) and to compare with radionuclide scintigraphy and the 'gold standard', surgery. Methods Forty-six consecutive patients undergoing USG of the anterior neck for a diagnosis of PHPT in whom a nuclear scan (technetium-99m sestamibi and/or thallium-201/technetium-99m pertechnetate scintigraphy) was also performed, were studied. The results of imaging were independently interpreted and correlated with reference to surgical findings. Results Forty-six patients had 52 abnormal parathyroid glands on surgical exploration and surgery was successful in all but one. Forty-one patients had a single adenoma, four had multigland disease and one had a paraganglioma. USG correctly localized the abnormal gland in 30 (73%) and scintigraphy was positive in 40 (98%) out of 41 patients with a single adenoma as confirmed on surgical exploration. Scintigraphy showed a positive concordant test in all 30 patients with a single abnormal gland detected on USG and picked up 10 out of 11 abnormal glands where USG was negative. The sensitivity and positive predictive value of USG for detecting a single abnormal gland was 73% and 100%, respectively, whereas the sensitivity and positive predictive value for scintigraphy was 98%. In patients with multigland disease, USG missed 3 (30%) out of 10 and scintigraphy missed 6 (60%) out of 10 abnormal parathyroid glands as confirmed on surgical exploration (P < 0.05). However, in two patients who had ectopic parathyroid gland, both the modalities localized the lesion in one (paraganglioma), whereas in the other neither test was helpful (left retro-esophageal). Conclusion USG is a convenient, affordable and useful modality to localize abnormal enlarged parathyroid glands in the majority of patients with PHPT. However, when USG is negative, scintigraphy is complementary to it.