Assessment of tubular function in neonates using urinary beta 2-microglobulin.

Renal proximal tubular function was assessed in neonates by measuring urinary beta 2-microglobulin (beta 2M) concentrations on days 1, 4, 7, 14 and 28. Values were elevated in stable preterm low-birthweight (LBW) neonates but not in stable term LBW neonates, suggesting that proximal tubular maturation is related to gestational age rather than birthweight. The urinary beta 2M was significantly increased on day 1 in neonates with the meconium aspiration syndrome but was not significantly different from normal subsequently. This indicated that although the proximal tubular cells may be susceptible to perinatal hypoxia, they maintain a remarkable capacity to recover in a relatively short period. Neonates with transient tachypnoea of the newborn had normal urinary levels of beta 2M indicating their renal tubular function was not impaired.