Use of plasma clearance of iohexol for estimating glomerular filtration rate in cats

Abstract

Objective - To determine whether plasma clearance of iohexol (PCio) can be used to estimate glomerular filtration rate (GFR) in cats. Animals - 4 renal-intact and 6 partially nephrectomized adult cats. Procedure - Plasma clearance of iohexol was determined after IV administration of iohexol; plasma concentrations of iodine were measured by use of a colorimetric assay. Results for PCio were compared with simultaneously obtained values for urinary clearance of creatinine (CCr). Results - The colorimetric assay used to measure plasma iodine concentrations was extremely precise. Results of PCio for all cats, renal-intact cats, and partially nephrectomized cats were closely associated with results of CCr. Mean difference between CCr and PCio determined for all cats was 0.95 ml/min/kg, which was < 30% of mean CCr for renal-intact cats. Coefficients of variance for PCio (5%) and CCr (8%) in renal-intact cats were similar. Conclusions and Clinical Relevance - Plasma clearance of iohexol determined by use of a simple colorimetric assay provided an estimation of GFR in cats that was not significantly different from that provided by CCr. Moreover, PCio more reliably estimates renal function than BUN and plasma creatinine concentrations. Because determination of PCio is less labor intensive and invasive, compared with CCr, it may be easier to perform in a clinical setting.