Plasma exogenous creatinine excretion for the assessment of renal function in avian medicine--pharmacokinetic modeling in racing pigeons (Columba livia).

The diagnostic evaluation of the glomerular filtration rate by urinary clearance has significant practical limitations in birds because urine is excreted together with feces. Thus, pharmacokinetic modeling of an exogenous plasma creatinine clearance could be useful for assessing renal creatinine excretion in birds. For this study, creatinine (50 mg/kg) was administered to 2 groups of 15 pigeons (Columba livia) each; in one group by the intravenous (IV) route and in the second by the intramuscular (IM) route. The time series of the plasma creatinine concentrations were analyzed by pharmacokinetic models. Body mass-specific creatinine excretion was determined for IV and IM administration to be between 6.30 and 6.44 mL/min per kg, respectively. Body surface area-specific creatinine clearance, which is related to the metabolic rate, was calculated between 0.506 and 0.523 mL/min per dm2, respectively. The results showed that IV as well as IM administration can be used for assessing renal creatinine excretion in pigeons. For practical reasons, IM administration is recommended, with the use of the Bateman function to calculate creatinine elimination.