Ultrasonographic measurement of kidney-to-aorta parameters in Whippets

In a previous study, an ultrasonographic method to assess kidney size in dogs as a ratio of kidney length to aortic luminal diameter (KL/AoD ratio) was proposed. The main limitation of this method was the wide range of normal values (5.5-9.1), which resulted in poor sensitivity and specificity. The aim of this prospective, observational, reference interval study was to determine whether the KL/AoD normal cut-off values in a single breed (Whippets) would have a narrower range than the previously reported normal reference ranges. The influence of sex, age, weight, and side on kidney length (KL) and of sex, age, weight, and scanning plane (longitudinal vs transversal) on aortic luminal diameter (AoD) were also investigated. Thirty-six clinically healthy Whippets (16 males, 20 females) without ultrasonographic renal lesions were included in this study. The 95% confidence interval of mean KL/AoD was found to be narrower than the previously reported range (ie, 6.3-6.9 versus 5.5-9.1). This was considered to be especially notable in that the KL in this breed exhibits marked sexual dimorphism. The KL/AoD ratio did not differ between right versus left sides or male versus female sexes in Whippets (P >.05). Findings from the current study provided KL/AoD ratio normal reference range cut-off values for future use in Whippets and supported the use of breed-specific KL/AoD ratio values for characterizing abnormal renal size in other canine breeds.