Abstract: Background - Adrenal incidentalomas (AIs) are defined as the unexpectedly found mass in the adrenal gland. Thanks to the development of imaging modalities such as ultrasonography and computed tomography, the chance to detect AIs is increasing. However, information about the characteristics of AIs and approaches to AIs is lacking. Objectives - This study aims to describe; endocrinological characteristics and the final diagnosis of AIs. Animals - Dogs that were found AIs and diagnosed via histopathology or endocrinological examinations were included. Methods - Electronical records from 2019-2022 in the Hokkaido university veterinary teaching hospital were retrospectively reviewed. Results - A total of 46 dogs were included in this study. 28 dogs were surgically treated and diagnosed via histopathology (Sx group); pheochromocytoma (n=14), adenocarcinoma (n=6), adenoma (n=6), sarcoma (n=1), no abnormality (n=1). 18 dogs were diagnosed via clinicopathological examination such as dexamethasone suppression test, urinary cortisol creatinine ratio, and urinary normetanephrine/metanephrine-to-creatinine ratio (non-Sx group); pheochromocytoma suspected (n=7); non-functional AIs suspected (n=7), Hyperadrenocorticism suspected (n=2). The remaining two dogs had bilateral AIs. In the Sx group, 14 dogs had a vascular invasion and 12 of these dogs were diagnosed as having pheochromocytoma. In the non-Sx group, the vascular invasion was only detected in the pheochromocytoma suspected group. Conclusion - Most AIs were diagnosed as pheochromocytoma and these dogs tend to have a vascular invasion, although they were incidental findings. Therefore, even if they are incidental findings, AIs should be carefully investigated. In addition, the urinary normetanephrine/metanephrine-to-creatinine ratio should be measured.
