Plasma Exogenous Creatinine Clearance Test in Dogs: Comparison with Other Methods and Proposed Limited Sampling Strategy

Abstract

Plasma clearance of creatinine was evaluated for assessment of glomerular filtration rate (GFR) in dogs. In 6 healthy dogs (Experiment 1), we determined 24-hour urine clearance of endogenous creatinine, plasma, and urine clearances of exogenous creatinine administered at 40, 80, and 160 mg/kg in a crossover design (linearity study), plasma iothalamate clearance, and plasma and urine clearances of 14 C-inulin. In Experiment 2, plasma creatinine and iothalamate clearances were compared, and a linearity study was performed as for Experiment 1 in 6 dogs with surgically induced renal impairment. Experiment 3 compared plasma creatinine clearance with plasma iothalamate clearance before and 3 weeks after induction of moderate renal impairment in 6 dogs. Plasma creatinine clearances were calculated by both noncompartmental and compartmental analyses. In Experiment 1, plasma inulin clearance was higher (P Ͻ .001) than other clearance values. Plasma creatinine clearances at the 3 dose rates did not differ from urine inulin clearance and each other. In Experiment 2, plasma creatinine clearances were about 14% lower than plasma iothalamate clearance (P Ͻ .05). In Experiment 3, decreases in GFR assessed by plasma clearances of iothalamate and creatinine were similar. Renal failure decreased the daily endogenous input rate of creatinine by 25%. Limiting sampling strategies for optimizing GFR calculation were proposed, allowing an error lower than 6.5% with 4 blood samples. These results suggest that determination of plasma creatinine clearance by a noncompartmental approach offers a reliable, inexpensive, rapid, and convenient means of estimating GFR in routine practice.

Testes de avaliação de injúria renal precoce em cães e gatos

“…Estudos de depuração da creatinina também têm sido utilizados na avaliação da TFG, devido à sua produção ser estável e a sua excreção ocorrer via filtração glomerular (FINCO et al, 1991;WATSON et al, 2002). Em cães, uma pequena quantidade de creatinina é ativamente secretada nos túbulos proximais (BUSH, 2004).…”

“…Devido ao aumento da creatinina sérica, essa técnica não deve ser usada em animais com uremia ou azotemia moderada (FINCO et al, 1991;BRASELTON;COOPER, 2001;WATSON et al, 2002;WATSON, 2003). As desvantagens desse método incluem a falta de uma preparação comercial de creatinina para administração e a necessidade de colheita de urina em tempos precisos (ROSS; FINCO, 1981;FINCO et al, 1991;KRAWIEC, 1994;WATSON et al, 2002). Esse método ainda não foi relatado em gatos (KERL;COOK, 2005).…”

“…Portanto, na análise da bioquímica sérica, o paciente com insuficiência renal intrínseca que demonstra azotemia, geralmente tem a injúria renal presente, antes do início das alterações bioquímicas (WATSON et al, 2002).…”

Evaluation of a Single Sampling Method for Estimation of Plasma Iohexol Clearance in Dogs and Cats with Various Kidney Functions

“…This method is easier to perform than the urinary clearance method because it does not involve the collection of urine samples and continuous infusion of the marker. Recently, plasma clearance tests for inulin, creatinine, iohexol, Chromium-ethylene diaminic tetraacetic acid ( 51 Cr-EDTA) have been developed to estimate GFR in dogs and cats [1,2,6,8,14,15,18,20,21,34]. Iohexol, a nonradioactive iodinated contrast media, is easy to use in the clinic and laboratory.…”

“…Iohexol has been evaluated as a filtration marker in dogs, cats, pigs, foals, and sheep [6,10,12,14,16,21,23]. Limited sampling methods for plasma clearance procedures are used for clinical expediency to estimate GFR in dogs and cats [1,6,10,14,21,34]. In this method, AUC is generally determined by the modified 1-compartment model (CM) using the Brosner-Mortensen (BM) formula, which was derived from human data using a radiolabeled index [5].…”