Research Communications of the 24th ECVIM-CA Congress

This study recieved support from the Institute for the Promotion of Innovation by Science and technology in Flanders (IWT) through a bursary to L. Ghys. Assessment of renal function is often needed, however existing methods including urine and plasma clearances are invasive, cumbersome and time consuming. In this pilot study the feasibility of a transcutaneous glomerular filtration rate measurement was investigated. The transcutaneous disappearance rate (expressed as half-life) of fluorescein-isothiocyanatelabelled sinistrin (FITC-S) was measured in three healthy research dogs and three healthy research cats. Plasma clearance of sinistrin (7 data points) was performed in both species as previously described (Res Vet Sci 1998; 64:151-6 and J Fel Med Surg 2003; 5:175-81) and half-life was calculated using a 2-compartment model with a freely available pharmacokinetic calculator (Comput Meth Prog Bio 2010; 99:306-14) . Renal elimination of FITC-S was measured transcutaneously for 4 hours (7000-8000 data points) using a miniaturized device as described previously for the same purpose in rats (Kidney Int 2011 79:1254-8). The procedures were performed in awake, freely moving animals using escalating doses of FITC-S (10 mg/kg, 30 mg/kg, 50 mg/kg) with a wash-out period of at least 24 h in each animal. To find the best position for the device, multiple devices were placed on each animal. The resulting FITC-S disappearance curves were visually assessed to determine the most suitable location and the appropriate dose to reach an adequate transcutaneous peak signal for kinetic analysis. In both species 30 mg/kg were adequate for kinetic calculation. The most suitable place for the device was the lateral thoracic wall in dogs and the ventral abdominal wall in cats, respectively. Transcutaneous FITC-S clearance was then repeated using the optimal dose and location and in parallel with the plasma sinistrin clearance. Plasma sinistrin clearances [ml/kg/min] were 5.5, 5.0 and 3.8 in the three dogs, respectively. Corresponding plasma elimination half-lives [min] were 26, 31 and 35, and corresponding transcutaneous elimination half-lives [min] were 26, 34 and 55, respectively. Plasma sinistrin clearances [ml/kg/min] were 2.8, 2.2 and 1.9 in the three cats, respectively. Corresponding plasma elimination half-lives [min] were 51, 60 and 61, and corresponding transcutaneous elimination half-lives [min] were 75, 96 and 83, respectively. In conclusion, transcutaneous FITC-S clearance is a feasible method for assessment of GFR in awake dogs and cats. It is noninvasive, well tolerated and easy to perform even in a clinical setting with results being readily available. A dose of 30 mg/kg of FITC-S seems adequate for kinetic assessment. Further studies are now needed to establish reference values and evaluate transcutaneous renal clearance in various conditions.