Preoperative evaluating of kidney function: Urea and Creatinine levels

Surgeons require determining urea and creatinine in patients undergoing surgery routinely as these parameters allow a judgment on the function of the kidneys. It is suggested that a normal urea level of blood is always associated with a normal value of creatinine in the same patient and, therefore, determination of urea alone suffices for this judgment. This spares collection of large volumes of blood sample for manual determination of creatinine, particularly in children and newborns. In this survey we analyzed the results of urea and creatinine estimation in blood samples of 1315 persons. In 95% of persons with a blood urea level of lower than 25 mg/dl and 99.8% havinglower than 20 mg/dl, the serum creatinine level was lower than 1 mg/dl. This confirms the suggestion that a person with a normal blood urea level will have a normal creatinine level too and an estimation of both of them is an unnecessary burden for the patient and the laboratory as well