Comparison of serum iohexol clearance and plasma creatinine clearance in clinically normal horses.

The research conducted investigates the efficacy of measuring glomerular filtration rate (GFR) in healthy adult horses using serum iohexol clearance (Cl(iohexol)) compared to the traditional method of plasma creatinine clearance (Cl(creatinine)).

Methodology

• The study focused on a sample of 10 clinically normal adult horses, to ensure that the findings were generalizable to the broader population of healthy adult horses.
• An injection of iohexol was administered intravenously at a concentration of 150mg for each kg of horse’s weight, with subsequent serum samples collected at specific intervals post-injection. Specifically, these intervals were 5, 20, 40, 60, 120, 240, and 360 minutes after injection.
• Concurrently, urinary clearance of exogenous creatinine – typically used to assess GFR – was measured during three separate 20-minute periods to provide a comparison point for the Cl(iohexol) method.

Results

• The researchers found significant alignment between the traditional measure of GFR and the Cl(iohexol) estimate. The plasma Cl(creatinine) values ranged from 1.68 to 2.69 mL/min/kg with a mean of 2.11 mL/min/kg, while the serum Cl(iohexol) mean was slightly higher at 2.38 mL/min/kg, with a range of 1.95 to 3.33 mL/min/kg.
• The limits of agreement plots, a statistical technique that illustrates the level of concordance between two measurement methods, showed a good correlation between the serum Cl(iohexol) method and the plasma Cl(creatinine) method, indicating that the new method provides comparable estimates to the traditional approach.

Conclusions and Implications

• The research findings suggest that using serum Cl(iohexol) provides a valid method for estimating GFR in clinically normal adult horses, with results comparable to those from traditional plasma Cl(creatinine) measurement methods.
• This study serves as an important first step in evaluating the potential for broader implementation of the serum Cl(iohexol) method for estimating GFR in adult horses, which may have significant implications for veterinary nephrology.