Estimation of glomerular filtration rate by plasma clearance of iohexol in healthy horses of various ages.

Glomerular filtration rate was significantly reduced in aged horses with serum creatinine ≥1.5 mg/dL compared to young horses with creatinine <1.5 mg/dL; no differences were obtained between young and aged horses with creatinine <1.5 mg/dL. Glomerular filtration rate evaluation should be considered in aged horses even if the plasma creatinine values are normal.