Prospective evaluation of healthy Ragdoll cats for chronic kidney disease by routine laboratory parameters and ultrasonography.

Ragdoll breeder organisations often forewarn Ragdoll cat owners that renal problems may develop as a result of polycystic kidney disease (PKD), chronic interstitial nephritis, familial renal dysplasia or nephrocalcinosis. Healthy Ragdoll and non-Ragdoll cats were prospectively evaluated by measuring serum creatinine and urea concentrations, routine urinalysis and abdominal ultrasonography. All Ragdoll cats also underwent genetic PKD testing. One hundred and thirty-three Ragdoll and 62 control cats were included. Ragdoll cats had significantly lower serum urea concentrations and higher urinary specific gravity. However, median creatinine concentration, median urinary protein-to-creatinine ratio, and the proportion of cats with serum creatinine or urea concentration exceeding the reference interval did not differ. One or more renal ultrasonographical changes were detected in 66/133 (49.6%) Ragdoll and in 25/62 (40%) control cats. Ragdoll cats showed significantly more frequent segmental cortical lesions (7.5% versus 0%), abnormal renal capsule (19.5% versus 8%) and echogenic urine (51.9% versus 25.8%). Chronic kidney disease (CKD) was ultrasonographically suspected in 7/133 (5.3%) Ragdoll and in none of the control cats, which approached significance. Laboratory parameters confirmed kidney dysfunction only in 1/7 of these Ragdoll cats. All Ragdoll cats were PKD negative. In conclusion, first, breed-specific serum creatinine reference intervals are not likely required for Ragdoll cats. Second, renal ultrasonographical abnormalities are common, both in Ragdoll and non-Ragdoll cats. Third, healthy young Ragdoll cats are uncommonly affected by PKD and CKD, but an increased susceptibility of Ragdoll cats to develop CKD cannot be excluded. Finally, Ragdoll cats are predisposed to segmental cortical lesions, which may indicate renal infarction or cortical scarring.