Rapid Evaluation of Creatinine Clearance

Abstract. Endogenous creatinine clearance, serum creatinine and urinary creatinine excretion have been determined in 368 patients hospitalized with various medical diseases, and without known renal disease. The patients were divided into 10‐year age groups and the results were analysed for age and sex differences. The average creatinine clearance in males showed a steady decline from 110 to 34 ml/min/1.73 m 2 from the age group 20–29 to the age group 90–99 years. The mean serum creatinine values did not show any significant variations with age, but urinary creatinine (mg/kg b.wt./24 h) decreased from 23.8 in the age group 20–29 to 9.4 in the age group 90–99 years. In females creatinine clearance declined from 95 to 39 ml/min/ 1.73 m 2 , serum creatinine was without significant change and urinary creatinine (mg/kg b.wt./24 h) decreased from 19.7 in the age group 20–29 to 8.4 in the age group 90–99 years. The finding of considerably decreased creatinine clearance values without elevation of serum creatinine values in the elderly is probably explained by a great reduction with age in lean body mass and thereby in creatinine production. In a group of 106 patients with serum creatinine values between 1.4 and 5.0 mg/100 ml the urinary creatinine (mg/kg b.wt./24 h) was not significantly different from that of patients without renal disease. A risk of overestima‐tion of glomerular filtration rate seems to exist if serum creatinine is used as the only parameter of renal function in these patients and might lead to intoxication with drugs which are mainly excreted by the kidney. The authors suggest a nomogram for rapid evaluation of creatinine clearance in ml/min.