Creatinine excretion rates for renal clearance studies

A total of 637 timed-urine collections for creatinine excretion rates obtai ned from 295 children over 14 years have been analyzed. The children ranged in age from 2.8 to 21.7 years at the time of the clearance study. The data analyzed included only one study from a child during any 6-month period. T he objective is to provide data defining the expected range of creatinine e xcretion for renal clearance studies. One hundred forty-two studies were co nducted on children not pretreated with cimetidine and 495 on those pretrea ted with cimetidine. Analysis showed that pretreatment with cimetidine for creatinine clearance studies does not alter creatinine excretion rates (P=0 .080; 95% CI -0.03 to 1.61). Creatinine excretion rates in urine collection s obtained at home (roughly 24-h collections) were compared with 2-h superv ised collections in the Children's Kidney Center. The supervised urine coll ections resulted in creatinine excretion rates 1.38 mg/kg/24 h greater than home collections (P=0.001; 95% CI 0.76-2.00). Using regression equations f or creatinine excretion rate with age, tables have been prepared showing th e expected rate of creatinine excretion for renal clearance studies in chil dren 3-21 years of age.