Abstract
Summary: A postnatal contraction of extracellular fluid occurs in low birth weight infants. Patterns of postnatal renal maturation were assessed with the assumption that changes in body composition were mediated in part by the developing kidney. Twenty-two appropriate for gestational age, low birth weight infants (birth weight mean = 1380 g, gestational age mean 31 weeks) were studied between 12 hr and 61 days of age to evaluate simultaneously glomerular and tubular functional maturation. Since most low birth weight infants have respiratory morbidities (respiratory distress followed by chronic lung disease), the infants were grouped into: group I (13 infants), transient or absent respiratory morbidities; and group II (9 infants), persistent and severe respiratory morbidities. Sodium excretion decreased with postnatal age in both groups. Sodium intake did not vary with postnatal age. The percentage of fractional sodium excretion was inversely related to postnatal age. Creatinine clearance correlated directly with postnatal age in both groups. Increased sodium excretion and percentage of fractional sodium excretion in the first 10 days of life may reflect extracellular fluid solute losses through the kidney. The premature kidney matured in a balanced fashion and persistent respiratory morbidities did not alter this pattern.
Speculation: The kidney of low birth weight infants probably plays an important role in the regulation of body fluid during the first week of life. The adjustment in renal tubular handling of sodium with greater sodium loss in the first days reflects its compensation to fit the demand of greater sodium excretion from the contraction of the extracellular fluid compartment. In an infant with a stable circulatory status, the presence of respiratory complications did not influence this adjustment process.
Similar content being viewed by others
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ross, B., Cowett, R. & Oh, W. Renal Functions of Low Birth Weight Infants during the First Two Months of Life. Pediatr Res 11, 1162–1164 (1977). https://doi.org/10.1203/00006450-197711000-00010
Issue Date:
DOI: https://doi.org/10.1203/00006450-197711000-00010
Keywords
This article is cited by
-
Fluid status in the first 10 days of life and death/bronchopulmonary dysplasia among preterm infants
Pediatric Research (2021)
-
Postnatal renal function in preterm newborns: a role of diseases, drugs and therapeutic interventions
Pediatric Nephrology (2006)
-
Serum creatinine concentration, urinary creatinine excretion and creatinine clearance during the first 9 weeks in preterm infants with a birth weight below 1500 g
European Journal of Pediatrics (1996)
-
Serum creatinine and creatinine clearance in healthy neonates and prematures during the first 10 days of life
European Journal of Pediatrics (1988)
-
Beta 2-microglobulin clearance in neonates: Index of tubular maturation
Kidney International (1985)