Normal appearance of the parathyroid gland on CT.

Abstract

To characterize the CT imaging features of normal parathyroid glands validated by ultrasonography (US) and intraoperative findings. This retrospective analysis used prospectively collected data from patients who underwent total thyroidectomy for benign or malignant thyroid nodules between February 1, 2023, and January 1, 2024. Patients were excluded if they had lateral neck node metastasis, renal disease, Graves' disease, biochemical parathyroid dysfunction, age < 19 or > 80 years, or insufficient imaging data. Normal parathyroid glands were defined as glands visualized on preoperative US and intraoperatively identified as non-enlarged glands without gross pathological abnormalities. Patients who underwent preoperative thyroid CT were included. CT images were independently reviewed by two radiologists to evaluate gland size, location, attenuation, and dynamic enhancement patterns. Interobserver agreement for attenuation measurements was assessed using intraclass correlation coefficients (ICC). Thirty-eight patients with 117 normal parathyroid glands confirmed by US-intraoperative correlation were included. Inferior glands showed a higher CT identification rate than superior glands (94.4% vs. 87%), although the difference was not statistically significant. Superior glands were consistently located at the tracheoesophageal groove, whereas inferior glands demonstrated greater positional variability (p < 0.001). Most glands (96.6%) showed arterial enhancement followed by washout on venous-phase imaging and exhibited lower attenuation than the thyroid gland. Interobserver agreement was excellent (ICC, 0.95-0.96). Normal parathyroid glands demonstrated characteristic anatomical distribution and dynamic enhancement patterns on CT in this highly selected surgical cohort. Further validation in broader and independent populations is warranted. Question The CT appearance of normal parathyroid glands has not been well established. Findings Normal parathyroid glands demonstrated characteristic arterial enhancement with washout on venous-phase and lower attenuation than the thyroid gland on CT. Superior parathyroid glands demonstrate a relatively constant location at the tracheoesophageal groove, whereas inferior glands show greater positional variability. Clinical relevance Familiarity with the normal CT appearance of parathyroid glands may help avoid confusion with other enhancing cervical lesions.