Background: Preterm very-low-birth-weight (PT-VLBW) infants are at risk of an elevated systolic blood pressure (SBP) in infancy and adulthood; however, the pathogenesis remains unclear. Altered renal development or function may be associated with increased SBP, but their contribution in PT-VLBW is unknown.
Methods: We determined renal function and its relationship to SBP in three groups of PT-VLBW at 1, 2, and 3 years of age, using serum cystatin-C to calculate the estimated glomerular filtration rate (eGFR).
Results: Cystatin-C levels decreased from 0.84 ± 0.2 (SD) within the 1-year group to 0.70 ± 0.1 mg/l (±SD; P < 0.001) at 3 years and were unrelated to gender, fetal growth, and neonatal indomethacin exposure. eGFR rose from 121 ± 59 in the 1-year group to 138 ± 21 ml/min · 1.73 m(2) (P < 0.001) at 3 years. At 1 year, cystatin-C levels decreased with increasing SBP (P < 0.007), and infants with SBP ≥ 90 th% had lower cystatin-C and higher eGFR (P < 0.05). At 3 years, infants with lower birth weight (P < 0.03) and gestational age (P = 0.06) had reduced eGFR.
Conclusions: Preterm very-low-birth-weight infants demonstrate increasing renal function with advancing age. An elevated SBP and eGFR at 1 year suggests dysfunctional renal autoregulation and hyperfiltration, which may alter subsequent renal function and contribute to the lower eGFR seen at 3 years in infants with the lowest birth weight and gestational age.