The authors examined in 22 subjects with a transplanted kidney after 2- to 3-month intervals for a period of 8-22 months the renal creatinine clearance (Ccr) and glomerular filtration rate (GFR) based on polyfructosan clearance (CPF). The mean value of the Ccr was 72.9 (+/- 23.3) ml/min/1.73 m/ and CPF 52.0 (+/- 19.5) ml/min/1.73 m2. The mean value of the Ccr/CPF ratio was 1.45 (+/- 0.33) and the tubular creatinine secretion (Tcr) 4.8 (+/- 5.5) mumol/min/100 ml CPF. Between values of Ccr and CPF a significant correlation was found (r = 0.752, p < 0.001). The value of the Ccr/CPF ratio in the same individual varied markedly in the course of the follow up period. The differences between the maximal and minimal values of the ratio in the same subject were in 36% of the patients greater than could be explained by errors of the applied analytical methods. From comparison of values of creatinine clearance and polyfructosan clearance at the onset and at the end of the investigation period ensues than in one half of the investigated cases a discrepancy was found between changes of the investigated clearance values. The assembled findings are consistent with the ideal that tubular creatinine secretion in the transplanted kidney may vary considerably in the course of time. Due to significant changes of tubular creatinine secretion in the same subject discrepancies develop between changes of creatinine clearance and the GFR. When evaluating the long-term stabilization or small changes of GFR of the transplanted kidney only on the basis of creatinine clearance erroneous conclusions may be reached.

Keywords: Adult; Creatinine /metabolism/; Female; Fructans /metabolism/; Glomerular Filtration Rate; Humans; Kidney Transplantation /physiology/; Male; Middle Aged