Ex vivo MRI and histological comparison of the canine adrenal glands

Cross-sectional imaging is widely used to characterize adrenal gland tumors in humans. In small animal veterinary medicine, while some studies have attempted to distinguish between types of adrenal gland neoplasia using CT, peer-reviewed studies investigating canine adrenal glands on MRI are scant. This prospective, pilot, single-center, method comparison, cadaveric study aimed to assess the agreement between ex vivo MRI findings and analogous histopathological findings of the adrenal glands in dogs. The adrenal glands of randomly selected dogs presented for necropsy were examined by MRI (n = 31). Additionally, five adrenal masses in dogs who underwent invasive adrenalectomy (including three adrenocortical carcinomas, one pheochromocytoma, and one adenoma) were imaged. Subsequently, gross pathology and histopathology of all the specimens were performed and correlated with the imaging findings. Adrenal gland lesions were identified on MRI with a sensitivity of 24%, a specificity of 100%, a positive predictive value of 100%, a negative predictive value of 31%, and an accuracy of 45%. The present study provides MRI features of multiple adrenal gland lesions that had never been described in dogs, including cortical hyperplasia, nodular fibrosis, hemorrhage, or multiple tumors, such as adenoma, carcinoma, and hemangiosarcoma. While MRI identified numerous adrenal gland lesions, a significant portion of those went undetected. Therefore, the absence of adrenal gland lesions on MRI does not exclude the possibility of histological lesions being present.