Sonography of intrathyroid parathyroid adenomas: Are there distinctive features that allow for preoperative identification?

ObjectiveThe purpose of our study was to determine if intra-thyroid parathyroid adenomas can be accurately identified by applying proposed criteria to preoperative ultrasound examinations in patients with primary hyperparathyroidism.Materials/methodsFifty-three patients with pathology proven intra-thyroid parathyroid adenomas and pre-operative ultrasounds were identified from a surgical database for a blinded, retrospective review. A contemporary, age-matched cohort of 54 patients with extra-thyroid parathyroid adenomas was identified as a control. A total of 64 patients within these cohorts had co-existing thyroid nodules. Proposed ultrasound criteria for identifying a parathyroid adenoma included solid composition, profound hypoechogenicity, and presence of a feeding polar vessel. Parathyroid adenomas were classified as extra-thyroid or intra-thyroid (partial or complete) based on their relationship with the thyroid gland during ultrasound evaluation and results were compared to surgical and histopathology reports as the gold standard. The results from the blinded, retrospective review during which the proposed, specific ultrasound criteria were applied were compared to the initial, pre-operative reports during which the proposed criteria were not applied. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the blinded, retrospective review and initial, pre-operative reports were calculated. Additionally, in patients with co-existing thyroid nodules, an attempt was made to differentiate parathyroid adenomas from the thyroid nodules.ResultsApplication of the proposed ultrasound criteria during blinded retrospective review yielded a sensitivity and specificity for detecting intra-thyroid parathyroid adenomas of 76% and 92%, respectively. The sensitivity and specificity of ultrasound for detecting intra-thyroid parathyroid adenomas on the initial reports was 29% and 95%, respectively. The sensitivity and specificity for differentiating an intra-thyroid parathyroid adenoma from a thyroid nodule was 78% and 86%, respectively.ConclusionApplication of specific ultrasound criteria facilitates pre-operative diagnosis of intra-thyroid parathyroid adenomas and facilitates surgical planning. This large series confirms previous, largely anecdotal reports of ultrasound's utility in detecting intra-thyroid parathyroid adenomas.