[Clinical study of tubular creatinine secretion in renal dysfunction]

Endogenous creatinine clearance (Ccr) has been much more commonly used to estimate renal function in clinical medicine, in comparison with inulin clearance (Cin) which is more accurate measure of glomerular filtration rate (GFR). There is, however, increasing difference between Ccr and Cin as renal function deteriorates. Since this difference is considered to be resulting from the tubular secretion of creatinine, Cin and Ccr were simultaneously measured in 81 patients with chronic renal disease, as well as 12 control subjects in this study. As Cin decreased, the Ccr/Cin ratio increased and the ratio varied widely even in patients with similar degree of renal impairment. The subjects were classified into 3 groups, group I (Cin greater than 80 ml/min), group II (80 ml/min greater than or equal to Cin greater than or equal to 40 ml/min) and group III (Cin less than 40 ml/min). The mean values of tubular creatinine secretion (Tcr) were 0.07 +/- 0.173 mg/min (+/- SD) in group I, 0.205 +/- 0.136 mg/min in group II and 0.333 +/- 0.139 mg/min in group III, respectively. Therefore, Tcr in the group of the severe impairment was the highest. In addition, Ccr and Cin were measured in 15 patients with chronic nephritis before and after an intravenous bolus injection of cimetidine (5 mg/kg BW). Following the injection Ccr/Cin ratio was reduced from an initial value of 1.51 +/- 0.23 to 1.18 +/- 0.13 in group II and from 2.00 +/- 0.44 to 1.55 +/- 0.25 in group III, respectively. Tubular secretion of creatinine appeared to be inhibited by cimetidine even in the patients with severe renal dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)