Assessment of renal functional maturation and injury in preterm neonates during the first month of life

Abstract

WE, Black MJ. Assessment of renal functional maturation and injury in preterm neonates during the first month of life.

Assessment of glomerular filtration rate in the neonate

“…This is followed by the mesonephros, a functioning kidney with relatively large glomeruli without loops of Henle, which develops from 4-16 weeks of gestation [15] and involutes completely by week 16 [16]. The permanent kidney, which begins to form in humans at approximately 30 days of gestation with the outgrowth of the ureteric bud from the (pronephric) Wolffian duct [17], is called the metanephros, and its development overlaps with that of the mesonephros. The ureteric bud invades the mass of metanephric mesenchyme, which induces multiple generations of dichotomous branching of the bud and the formation of nephrons at the ureteric bud tips [18].…”

Urinary Nephrin as a Biomarker of Glomerular Maturation and Injury Is Associated with Acute Kidney Injury and Mortality in Critically Ill Neonates

“…Neonatal renal function is predominantly influenced by renal structural maturity, and urinary protein excretion is decreased with increasing renal maturation [18-22]. uAlb and uCysC concentrations have been reported to gradually decline with increasing gestational age at birth, which reflects renal maturation [18, 20].…”

“…However, sCr was not measured daily. In addition, sCr reflects maternal levels during the first few days of life and declines progressively with increasing postnatal age to reach a stable neonatal level by 2 weeks of life, and is therefore not a reliable index of renal function [21, 22]. The neonates also have a limited ability to concentrate urine; urine output ≤0.5 mL/kg/h is a nonsensitive marker of neonatal AKI [26].…”

Preterm Birth and/or Factors that Lead to Preterm Delivery: Effects on the Neonatal Kidney

“…During the first week after birth, glomerular filtration rate (GFR) is significantly lower in preterm infants compared to term infants [26][27][28] and it is positively correlated with gestational age at birth and postnatal age [29][30][31]. Likewise, creatinine clearance, one of the most commonly used markers of renal function, is positively correlated with both gestational age and postnatal age [20,21,[29][30][31][32][33][34][35][36][37][38][39]. In addition, preterm neonates excrete high amounts of sodium in the early neonatal period compared to term neonates, with the fractional excretion of sodium inversely correlated with gestational age and postnatal age [29,[39][40][41][42][43].…”

“…Alternatively, high levels of low molecular weight proteins (such as β2-microglobulin) are indicative of reduced reuptake by the proximal tubule cells [45,46]. The occurrence of proteinuria in neonates is strongly linked to gestational age at birth with studies in preterm infants reporting significantly greater albumin and β2-microglobulin concentrations over the first month of life in infants born <32 weeks gestation, compared to neonates born >32 weeks gestation [39,47]. To date, it remains unclear whether the observed proteinuria in preterm infants is a result of their renal immaturity or due to postnatal renal injury.…”