Comparison of Ultrasonographic and Computed Tomographic Features of Parathyroid Glands in Canine Primary Hyperparathyroidism

A multicenter retrospective study compared ultrasonographic (US) and computed tomographic (CT) characteristics of parathyroid glands in 20 dogs with histopathological confirmation of primary hyperparathyroidism. Twenty-four glands were diseased (17 adenomas and 7 hyperplastic glands). Two blinded radiologists assessed US and CT studies in two readings. A similar total number of glands was visualized (US 59 and CT 63). Intermodality agreement for identification of the same individual glands was slight for presumed normal glands but perfect for diseased glands, with 23 of 24 diseased glands visualized on both modalities. Glands were more often poorly marginated on CT compared to US, whereas other descriptive features were similar across modalities. The only shared feature of diseased glands on both modalities was significantly greater size. Intermodality agreement for size measurements was poor for presumed normal glands, with CT measuring larger, but moderate to good for diseased glands. Intermodality agreement for classifying glands as enlarged (largest dimension ≥4 mm) was substantial. Enlargement-based localization sensitivity for diseased glands was similar between modalities (US 18/24, 75.0%; CT 19/24, 79.2%). Additional enlarged glands without histopathological confirmation of disease were identified in three instances on US and seven on CT. Interobserver and intraobserver agreement for quantitative parameters was similar between modalities; however, agreement for most descriptive parameters was superior on US. Overall, US likely remains the first-line imaging modality for localizing parathyroid disease; however, these findings support selective incorporation of CT to aid therapeutic decision-making in canine primary hyperparathyroidism.