Fractional excretion of uric acid in infancy and childhood: Index of tubular maturation

Abstract

Passwell, J. H., Modan, M., Brish, M., Orda, S., and Boichis, H. (1974). Archives of Disease in Childhood, 49, 878. Fractional excretion of uric acid in infancy and childhood: index of tubular maturation. Normal newborns had a low glomerular filtration rate measured by creatinine clearance which progressively increased to reach adult levels by one year of age when corrected for surface area.There was also an increased fractional excretion of uric acid (34*6%±11 2 SD).Progressive maturation of this tubular function was observed within the first year of life. Thereafter, stable levels approaching adult levels of excretion were maintained. Linear regression functions of log-transformed values of fractional excretion of uric acid by weight were fitted separately to the newborns, infants < 1 year, and children aged 1 to 7 years. The 3 groups were found to constitute three distinct populations with regard to both the slope of the regression lines and the scatter of values about the line, which decreased significantly from the youngest to the oldest group. In low birthweight infants both glomerular and tubular maturation, as evidenced by these parameters, were related to age rather than to weight.It is suggested that the large urinary uric acid load excreted in the first days of life is facilitated by the concomitant deficiency of acidification and concentration of urine.Pink stained diapers due to urate deposition is a common occurrence in the newborn nursery. The presence of large amounts of urates in the renal tissue of neonates as 'urate infarcts' is also a well known incidental finding at necropsy. These two facts were impressed upon us by a routine survey in newborns, where large amounts of uric acid crystals were found in the urinary sediment. Accordingly, we undertook this study to investigate the excretion of uric acid by the kidney of the normal newborn and the progressive maturation of this function during the first year of life. Male infants predominated because of the difficulty of collecting urinary specimens in the females. No sex differences were found in the various tests of renal function. All the newborn infants were products of normal pregnancies and were born with Apgar scores of 10. Informed consent was obtained for all the studies.Renal studies. Disposable urine collectors were used. The infants were under constant supervision throughout by a special nurse in order to assure complete urine collections. Collections were started 72 hours after birth and the first urine was discarded. Collection thereafter proceeded for 24 hours in newborns. The end point was taken as the last time urine was passed as noted by the special nurse. This last fresh specimen was used for pH examination (pH meter 29 Radiometer) and routine urine analysis. In older infants and in children, at least 3 complete timed specimens were collected for clearance calculations. Venous blood for blood chemistry was withdrawn at the end of the collections. 878 on 12 May 2018 by guest. Protected by copyright.

Serum Uric Acid as an Obesity-Related Indicator in Early Adolescence

“…Data in the literature indicate that serum uric acid levels increase with age during childhood and show a clear-cut developmental difference between boys and girls during puberty (Passwell et al 1974;Stapleton et al 1978). While serum uric acid is described as stabilizing at lower levels in girls around the age of 11 years, uric acid levels in boys show an upward trend throughout adolescence (Costa et al 2002).…”

Hypouricemia in Neonates with Syndrome of Inappropriate Secretion of Antidiuretic Hormone

“…This relative hyperuricemia is thought to be the result of increase urate production; uric acid excretion does not appear to be limited by the immaturity of the neonatal kidney (26,28,29). In neonates, the mean FEU, is nearly three time the upper normal adult limit (28). Values as high as 70% are observed at 29 to 3 1 wk gestation; the mean value at term is 38% (29).…”

“…Prolonged labor and respiratory distress tend to be associated with even higher SUr concentrations in the neonate (26). This relative hyperuricemia is thought to be the result of increase urate production; uric acid excretion does not appear to be limited by the immaturity of the neonatal kidney (26,28,29). In neonates, the mean FEU, is nearly three time the upper normal adult limit (28).…”

“…Values as high as 70% are observed at 29 to 3 1 wk gestation; the mean value at term is 38% (29). The high FEU, during the neonatal period reflects increased tubular secretion, decreased tubular reabsorption, or both (28,29).…”

Uric Acid Metabolism in Therapy of Glycogen Storage Disease Type I

“…Isolated uric acid was solubilized in Hyamine, added to Scintisol, and radioactivity determined in a Packard liquid scintillation counter. Renal uric acid excretion was determined in the morning during a 3-hr fast (17). The experimental period consisted of the same diet, except that onethkd of the tdtal calories were administered over 1 0 hr at night by nasogastric feeding of Vivonex (7).…”