Ultrasonographic measurement of adrenal gland-to-aorta ratio as a method of estimating adrenal size in dogs.

Background Adrenal size has been used as the principal criterion for differentiating a normal gland from adrenal hyperplasia. The objectives of this study were to establish an ultrasonographic measurement of adrenal gland-to-aorta (adrenal/Ao) ratio to estimate the adrenal size and to assess the effects of bodyweight, age and sex on the adrenal/Ao ratio in non-adrenal gland disease dogs. Methods Two hundred and thirty-four dogs (120 entire females and 114 entire males) considered non-adrenal gland disease were included in this study. Dogs were allocated into three bodyweight categories (<10 kg, 10-20 kg and >20 kg), and four age groups (<1 year, 1-5 years, 5-10 years and >10 years old). Measurements of the maximal thickness of caudal pole of both adrenal glands and the aortic luminal diameter in sagittal plane were performed on the ultrasonographic images. Three different ratios were calculated for each dog. Results Sex and age did not influence on the adrenal/Ao ratio. There were differences (P<0.05) between the three dog sizes for adrenal/Ao ratio, being the highest value for small size and the lowest value for large size. Conclusions In this study, only bodyweight influences the ultrasound measurement of the adrenal/Ao ratio in non-adrenal gland disease dogs.