Measurement of urinary constituents and output using disposable napkins.

A procedure for estimating 24 hour urine output in infants using disposable nappies has been validated. In addition, it has been shown experimentally that the urinary concentrations, and hence 24 hour outputs of a range of constituents (sodium, potassium, nitrogen, creatinine, urea, amino acids, and deuterium oxide), may be measured accurately using samples of urine obtained from nappies. It is concluded that the urine collection procedure described has several major advantages over traditional urine bag methods, and has a wide application in clinical practice and research.