Estimation of nitrogen balance based on a six-hour urine collection in infants.

The accuracy of a 6-hr vs a 24-hr urine collection for the determination of urinary urea nitrogen was studied in 15 infants. Patient's age ranged from 2 weeks to 3 yr, encompassing a wide variety of diagnoses. All patients had normal renal function at the time of the study. Participants had indwelling foley catheters throughout the study. Urine specimens were collected over a continuous 24-hr period. Aliquots obtained from urine collected over 0 to 6 hr and the total urine collection were analyzed utilizing the urease enzymatic method in the Astra. Statistical analysis was performed comparing the actual 24-hr determination to the estimation based on the 6-hr collection, utilizing linear regression. The analysis of data produced a highly significant correlation (r = 0.904, p less than 0.0001). When a 24-hr urine collection is not possible, a 6-hr collection is a useful alternative for the calculation of nitrogen balance in infants.