Renal uric acid clearance in human neonates

doi:10.1016/S0022-3476(83)80369-2

The Journal of Pediatrics

Volume 103, Issue 2, August 1983, Pages 290-294

https://doi.org/10.1016/S0022-3476(83)80369-2 Get rights and content

Renal clearance of uric acid was examined in 40 premature and term infants during the first 24 hours of life. Creatinine clearance and uric acid clearance increased with increasing gestational age. Serum uric acid concentration (r=−0.31, P<0.05) and fractional excretion of uric acid (r=−0.50, P<0.01) were inversely related to gestational age; FEUA was nearly 70% at 29 to 31 weeks gestational age, and decreased to a mean value of 39±14% (±SD) at 38 to 40 weeks gestational age. The decline in FEUA with advancing gestational age appears to represent alterations in net renal tubular transport of uric acid, because the filtered load of uric acid increased with gestational age. Postnatal clearance studies were performed in 18 premature infants of 29 to 35 weeks gestational age; FEUA also declined during early postnatal development (r=−0.44, P<0.01). In all studies, a relationshop between FEUA and fractional excretion of sodium was observed. The high basal excretion of uric acid in infants may increase the risk of acute uric acid nephropathy when excretion demands are increased.

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Renal stone formation is a multifactorial process in which all the information obtained from the patient (medical history, imaging tests, stone analysis, metabolic study and physicochemical urine analysis) shows a different facet of the same process. Consequently, all these investigations should be evaluated together. In half of all patients, stone formation is secondary to the presence of metabolic alterations in urine, of which the most frequent is idiopathic hypercalciuria. The second most frequent cause is infection and/or urinary malformations, while hereditary enzyme defects are highly unusual. Reference values for urinary excretion of lithogenic metabolites (calciuria, uricosuria, oxaluria, citraturia, etc.) are essential for an adequate metabolic study, since urinary excretion depends on multiple factors, which have been described in the various publications in the literature. Physicochemical study evaluating saturation of the various salts dissolved in urine should be performed. These saturations are currently considered to be a highly useful index for determining the risk of crystallization and stone formation in patients with lithiasis and for evaluating the effectiveness of treatment. Lastly, the metabolic profile of renal lithiasis in children resembles that in adults, suggesting that predisposition to renal lithiasis begins in childhood. The early detection of the metabolic alterations observed in these patients will reduce the incidence of this disease in both children and adults

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^*: Supported in part by the University of Tennessee New Faculty Grant H-00047 and by Clinical Associate Physican Award USPHS RR-00211 by the General Clinical Research Center, United States Public Health Service.

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Renal uric acid clearance in human neonates*

J Pediatr

J Pediatr

J Pediatr

Am J Med

J Pediatr

Am J Med

J Pediatr

J Pediatr

Am J Obstet Gynecol

Am J Med

The metabolism of nitrogen, phosphorus and the purine substances in the newborn, with special reference to the causation of the uric acid infarcts of the kidney

Am J Dis Child

Neonatal hyperuricemia

J Pediatr

Quantitative measurements of the urinary excretion of creatinine, uric acid, hypoxanthine and xanthine, uracil cyclic AMP, cyclic GMP in healthy newborn infants

Eur J Pediatr

Uric acid in blood and urine in infants

Acta Physiol Scand

Purine metabolism as reflected in uric acid excretion

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

Arch Dis Child