Megan Boszko 1, Richard Burgess 1, Matthew Paek 2
Background
Primary hyperparathyroidism in dogs, although uncommon, results in hypercalcemia due to excessive parathyroid hormone secretion, typically from neoplastic or hyperplastic glands. Preoperative imaging helps identify affected glands and minimize surgical complications. Ultrasound is commonly used but has limitations and a notable rate of discordance with surgical findings. Computed tomography (CT), due to its high tissue resolution, is proposed as a potentially more accurate modality. This study aimed to evaluate the agreement between CT findings and surgical outcomes in identifying parathyroid pathology in dogs.
Methods
This prospective study enrolled 20 dogs with suspected primary hyperparathyroidism from 2022 to 2024. All dogs underwent cervical CT interpreted by a board-certified radiologist, followed by bilateral cervical exploratory surgery by board-certified or residency-trained surgeons. The laterality, position, and size of the glands identified on CT and during surgery were compared. Histopathological analysis was performed on excised tissues. Agreement between CT and surgery was assessed using Cohen’s kappa for laterality and position, and Lin’s concordance correlation coefficient (CCC) for gland length.
Results
CT showed near-perfect agreement with surgery for laterality (κ = 0.81) and position (κ = 0.92) of the abnormal glands, but only fair agreement for size (CCC = 0.38). CT identified abnormal glands in 95% of cases, but 25% of dogs had additional abnormal glands detected during surgery that were not visible on CT. Most pathologic glands were right-sided, particularly in the right external parathyroid position. Histopathology confirmed adenomas (48%), hyperplasia (24%), and carcinomas (6.9%). Postoperative hypocalcemia occurred in 45% of dogs, and persistent hypercalcemia occurred in 10%.
Limitations
Limitations include small sample size, the involvement of multiple surgeons, and single-radiologist CT interpretation, limiting assessment of interobserver variability. Surgeons were not blinded to CT results, introducing potential bias. CT may miss small or ectopic glands, and no direct comparison with ultrasound was made in this cohort.
Conclusions
CT demonstrates high agreement with surgical findings for identifying the side and location of abnormal parathyroid glands in dogs, though it may miss some lesions. Continued bilateral surgical exploration remains essential to ensure complete identification of pathologic tissue. Future studies should compare CT with ultrasound and explore advanced imaging modalities such as 4D CT for improved diagnostic accuracy.
Transverse (A–D) and dorsal multiplanar reconstructed (E–H) images from case 6 (A, B, E, F) and case 3 (C, D, G, H). In case 6, Thearrows highlight the hypoattenuating, minimally contrast-enhancing parathyroid nodule within the cranial pole of the left lobe of the thyroid gland (A,B, E, F). In case 3, the arrows highlight the hypoattenuating, minimally contrast-enhancing parathyroid nodule immediately right lateral to the thyroidgland, showing a paraglandular location (C, D, G, H). C—carotid arteries. T—trachea
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