Renal dimensions at ultrasonography in healthy Ragdoll cats with normal kidney morphology: correlation with age, gender and bodyweight

Fifty-six healthy Ragdoll cats underwent an ultrasonographical examination of the urinary tract to evaluate if gender, age, bodyweight and presence of a medullary rim sign had a significant influence on renal length and corticomedullary ratio (CM). Individual variation percentage was much more pronounced for renal length in comparison with CM ratio. Mean renal length measured 3.83 ± 0.45 cm (range 2.98-5.09 cm), mean cortical thickness 0.73 ± 0.15 cm (range 0.36-1.18 cm), mean medullary thickness 0.87 ± 0.19 cm (range 0.46-1.39 cm) and mean CM ratio 0.88 ± 0.29 (range 0.29-1.78). Renal length showed a significant positive correlation with bodyweight (P <0.0001), age (P = 0.0073) and male gender (P <0.0001). Therefore, these parameters have to be kept in mind when evaluating renal length on ultrasound. The CM ratio was solely influenced by the presence of a medullary rim sign (P <0.0001). Further research, however, is needed to investigate the usefulness of the CM ratio for the detection of kidney disease by ultrasonography.