Reduced kidney function in very-low-birth-weight preterm infants at preschool age.

Background: Very-low-birth-weight (VLBW) infants have significant risk factors for adverse health outcomes. Previous studies have focused on neurological, pulmonary, and cardiovascular complications, but the long-term outcomes of other organ functions particularly kidney function warrant further investigation. This prospective study aimed to compare kidney function between VLBW preterm and term infants at 5-6 years of age.

Methods: Participants underwent comprehensive assessments of kidney function and blood pressure. Estimated glomerular filtration rates (eGFR) for serum creatinine (Cr) and cystatin C (CysC) were calculated using the CKiD-U25 equations, and comparative analyses conducted between preterm and term groups. In the preterm group, perinatal growth rates of weight and height at various stages were monitored to investigate their potential association with kidney function.

Results: A total of 61 VLBW preterm and 40 term children participated in the study. The preterm group exhibited significantly higher serum CysC levels (0.97 vs. 0.87 mg/L, p = 0.001), lower eGFR-CysC (82.3 vs. 93.0 mL/min/1.73 m², p < 0.001), and smaller kidney length compared to the term group. Notably, 72% of VLBW preterm children exhibited abnormal eGFR-CysC levels (< 90 mL/min/1.73 m²). Preterm children exhibited significantly higher systolic and diastolic blood pressures, but growth velocities and perinatal characteristics did not significantly affect kidney function at preschool age.

Conclusions: Kidney function may be diminished in VLBW preterm children at preschool age. However, no significant effects of perinatal risk factors or growth on kidney function were observed. These findings underscore the importance of ongoing long-term monitoring of kidney health in this vulnerable population.