Poorly concentrated urine is associated with an increased risk of developing chronic kidney disease in apparently healthy cats

Objective: To evaluate medical records from mature and senior cats stratified by urine specific gravity (USG; ≥ 1.035 or < 1.035) to examine the development of presumptive chronic kidney disease (CKD). Methods: 15,027 apparently healthy cats were evaluated for inclusion in a 2-year longitudinal retrospective study. Outcome during the study period was a presumptive CKD diagnosis or development of creatinine > 1.6 mg/dL and USG < 1.035 with consistent clinical signs. Cats were grouped by age (mature, 11 to 15 years; senior, > 15 years) and USG values for contingency and survival analyses. A CKD assignment was precluded in cases where historical information, physical examination findings, diagnoses for each visit, and available diagnostic results over the study period contradicted a CKD diagnosis. Results: 504 mature cats with a USG < 1.035, 1,872 mature cats with a USG ≥ 1.035, 89 senior cats with a USG < 1.035, and 149 senior cats with a USG ≥ 1.035 were included. In mature cats, contingency analysis using χ2 test found statistically significant differences in proportions of the population diagnosed presumptively with CKD during the study period, with an increased OR of 3.191 (CI, 1.611 to 6.231) as well as a shorter time to CKD diagnosis in the cats with USG < 1.035 at initial assessment. Conclusions: Identification of a USG < 1.035 appears to facilitate earlier renal disease detection and inform more individualized diagnostics in mature feline patients. Clinical Relevance: Identification of inadequate urine concentration in mature cats should raise concern for future renal disease detection and impact clinical assessment and monitoring.