Assessment of tubular function in neonates using urinary β₂-microglobulin

Renal proximal tubular function was assessed in neonates by measuring urinary β₂-microglobulin (β₂M) 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 β₂M 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 β₂M indicating their renal tubular function was not impaired.