RESUMO
This paper was designed to investigate the correlation between the renal clearance and the plasma concentration of creatinine. Of the curve obtained, three segments were studied: 1 - When the glomerular filtration rate (GFR) was greater than 60 ml per min. the plasma concentration fluctuated between 0.44 and 1.59 mg/dl. 2 - When GFR was between 30 and 60 ml per min. the plasma concentration reached 2.4 mg/dl, and 3 - When GFR was less than 30 ml per min. the plasma level increased to values as high as 28 ml/min. The urinary concentration of creatinine can be divided into two broad groups depending on the GFR. The boundary of this division is around 60 ml per min. This suggests that when GFR is depressed there would exist a limitation of the tubular secretion of creatinine or urinary dilution problems. It is demonstrated that there is a poor correlation between creatinine clearance and its plasma concentration, and hence the repeated measurement of creatinine clearance becomes imperative in the follow-up of patients.