Exogenous creatinine clearence indexed to body surface area allows estimation of GFR and across species comparison.

Abstract The assessment of renal function in birds is difficult because sensitive biomarkers are lacking. Previous studies have demonstrated the feasibility of measuring the exogenous creatinine clearance in pigeons, indicating the potential use of this technique for the assessment of renal function in birds. The aim of the study was to index the exogenous creatinine elimination rate by body surface area, enabling comparison between different species. Exploratory data on common buzzards (Buteo buteo), Eurasian eagle-owls (Bubo bubo), domestic goose (Anser anser domesticus) and racing pigeons (Columba livia) were collected and indexed by body surface area. A sterile creatinine solution was administered at a dose DM = 50 mg kg−1 i.m. into the deep pectoral muscle of 52 clinically healthy birds of the four species with different body masses. The time course of the plasma creatinine concentration was measured and analyzed by a parametric pharmacokinetic Bateman model, followed by indexing the exogenous creatinine clearance (ECC) by body surface area. The exploratory ECC values for birds with a mean body mass ranging from 0.42 kg (pigeon) to 8.2 kg (goose) were between 0.4261 mL min−1 dm−2 (CI 0.3882–0.4672) and 0.8717 mL min−1 dm−2 (CI 0.8091–0.9362). ECC indexed by body surface area turned out to be independent from body mass. Resulting exploratory data covering species with different body masses are comparable with published data from very complex studies of avian renal function.