Baseline variables and their relationship with renal survival time were evaluated in cats with chronic kidney disease, as defined by initial plasma creatinine concentration >_ 2.0 mg/dl and urine specific gravity (USG) 1.025. All cats were fed a diet that contained low amounts of protein and sodium for at least 14 days before selection and for the duration of the trial. Cats were followed for up to 3 years, and renal survival time was defined as the time from initiation of the study to the point at which parenteral fluid therapy was indicated, euthanasia was elected, or death related to renal failure occurred. Clinical signs were measured as present or absent by the veterinarian during clinical examination of the cat and after questioning the owner. Anorexia was the most common clinical sign; anemia and hypokalemia were also common findings. However, no significant effect on renal survival time was observed for any of the clinical signs. The frequency of hyperkalemia increased and that of hypokalemia decreased with progression of stage of chronic kidney disease, but no significant association was observed with renal survival time. The best variables for predicting survival time in individual cats identified in this study were, in order, plasma urea concentration, plasma phosphate concentration, blood hemoglobin concentration, blood erythrocyte count and blood hematocrit, plasma creatinine concentration, and urine protein-creatine concentration and USG. Urine protein-creatinine values as low as 0.2 appear to be clinically relevant in cats with chronic kidney disease.

COMMENTARY: This study emphasizes the importance of initial levels of serum creatinine, BUN, phosphate, hematocrit, and urine protein-creatinine ratio as prognostic factors in cats with CKD. Even mild proteinuria appeared to have a negative effect on survival. The study reinforces the value of the IRIS (International Renal Interest Society) staging system for classifying the severity of renal disease. However, because of extreme variability in the results, no single or combined group of values can accurately predict renal survival time in an individual cat. -- David F. Senior, BVSc, Diplomate ACVIM & ECVIM-CA

Prognostic factors in cats with chronic kidney disease. King JN, Tasker S, Gunn-Moore DA, et al. J VET INTERN MED 21:906-916, 2007.