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.