MEASUREMENT OF THE GLOMERULAR-FILTRATION RATE (GFR) AFTER ADMINISTRATION OF IODINE CONTRAST-MEDIUM WITH THE RENALYZER PRX90 IN HEALTHY CATSAND CATS WITH RENAL DISEASES

In the present study, the measurement of the glomerular filtration rat e (GFR) in the cat with the aid of an iodine contrast medium clearance with the renalyzer PRX90 is introduced. Investigations on the accurac y of measurement showed that even repeated measurement of plasma sampl es after two days of storage at room temperature yielded reproducible clearance results. Also, partial dilution of the plasma sample (2 ml w ith 1 ml Aqua bidest.) to reduce the volume of blood withdrawn still p roduced reliable results. Further dilution of the plasma volume (1 ml with 2 ml Aqua bidest.) however did not allow for accurate measurement s. A total of 59 cats of different age and sex were included in the st udy. 31 cats had healthy kidneys with urea and creatinine values withi n the reference range, unchanged urine findings and physiologic urine protein patterns (SDS-PAGE). These cats served as reference group. The GFR reference value ascertained for these animals was 2.1 ml/min/kg B W ((x) over bar = 3.45 ml/min/kg with s = +/- 1.0 ml/min/kg). 28 cats had elevated values of urea and creatinine in the blood, as well as pa rtially changed urine findings. For further diagnosis of renal disease , separation of urine proteins was done with the SDS-PAGE in the Phast System, which in all cases yielded a pathologic urine protein pattern. In 11 cases the renal disease could be further confirmed by histologi cal investigation. GFR in these patients was clearly lowered compared with healthy cats, with measured values between 0 and 1.8ml/min/kg. It can be concluded that the renalyzer allows reliable determination of the GFR also in the cat. To what extent measurement of the GFR is also helpful-to diagnose nephropathies in the stage of compensation needs to be further investigated. In cats with high grade uremia and a GFR b elow 1 ml/min however, an exact calculation is not possible, since the accuracy of measurement within this range is inadequate. Thus, in sev ere disease no correct assessment is possible, and no statement concer ning prognosis can be made.