Abstract
PURPOSE: This study was performed to examine the ultrasonography (US) features of normal parathyroid glands (PTGs) that were identified on preoperative US and subsequently confirmed during thyroid surgery. METHODS: This retrospective study included a consecutive sample of 161 patients (mean±standard deviation age, 56±14 years; 128 women) with 294 normal PTGs identified on preoperative US PTG mapping and confirmed during thyroidectomy. A presumed normal PTG on US was defined as a small, round to oval, hyperechoic structure in the central neck. These presumed normal PTGs, as identified on preoperative US, were mapped onto thyroid computed tomography images and diagrams of the thyroid gland and neck. During the preoperative real-time US examinations, the location, size, shape, echogenicity, echotexture, and intraglandular vascular flow of the identified presumed PTGs were assessed. These characteristics were compared between superior and inferior PTGs using the generalized estimating equation method. RESULTS: The typical US features of homogeneous hyperechogenicity without intraglandular vascular flow were observed in 267 (90.8%) normal PTGs, while atypical features, including isoechogenicity (1.0%), heterogeneous echotexture with focal hypoechogenicity (5.8%), and intraglandular vascular flow (3.7%), were noted in 27 (9.2%). Inferior PTGs were more frequently identified in posterolateral (36.1% vs. 5.3%) and thyroid pole locations (29.9% vs. 5.3%), and less frequently in posteromedial locations (29.2% vs. 88.0%), compared to superior PTGs (P<0.001 for each comparison). CONCLUSION: Most normal PTGs displayed the typical US features of homogeneous hyperechogenicity without intraglandular vascular flow. However, in rare cases, normal PTGs exhibited atypical features, including isoechogenicity, heterogeneous echotexture with focal hypoechogenicity, and intraglandular vascular flow.