Evaluation of urinary kidney injury molecule-1 in cats with chronic kidney disease

ObjectivesKidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein on proximal renal tubular epithelial cells that is increased in the urine of cats with acute kidney injury. The utility of measuring urine KIM-1 in cats with chronic kidney disease (CKD) and the relationship with International Renal Interest Society (IRIS) stage are unknown. The objectives of this study were to determine the distribution of KIM-1 concentrations in cats with different stages of CKD and investigate the relationship between urine KIM-1 and urine specific gravity (USG), urine protein and serum urea, creatinine, phosphorus, potassium and symmetric dimethylarginine concentrations.MethodsA total of 74 cats with CKD were recruited prospectively from a first-opinion feline-only practice. Blood and urine samples were collected from all cats. The stage of CKD was determined as per IRIS guidelines. Urine KIM-1 concentration was determined with a previously validated lateral flow assay. KIM-1 was reported as a test:control ratio. The distribution of KIM-1 values in cats with CKD was determined, and the correlation between KIM-1 and other determinants of renal function was calculated. Urine KIM-1 was normalized to a USG of 1.035 and the analysis was repeated.ResultsCats with CKD had a median urine KIM-1 value of 0.1544 (range 0.038-0.540). The median KIM-1 values in cats with IRIS stage 1, 2, 3 and 4 CKD were 0.152 (range 0.113-0.512), 0.165 (range 0.038-0.540), 0.150 (range 0.037-0.448) and 0.140 (range 0.067-0.448), respectively. There were no differences in urine KIM-1 values relative to IRIS stage. Urine KIM-1 values were correlated with USG (<i>r</i>² = 0.482; <i>P</i> = 0.005). An analysis of KIM-1 values normalized to USG resulted in similar findings.Conclusions and relevanceUrine KIM-1 values in cats with CKD were similar to those previously described in healthy cats. There was a moderately strong correlation between urine KIM-1 concentration and USG. Sequential measurement of KIM-1 in cats with progressive CKD may be informative.