Incidence, risk factors, and outcomes of nephrocalcinosis in preterm infants: a prospective cohort study.

Background: Kidneys in preterm infants are exposed to various exogenous factors that may affect their maturation and development. Hence, they are at a higher risk of developing nephrocalcinosis (NC). We aimed to evaluate the incidence, risk factors, and short-term outcomes of NC in preterm neonates admitted to a tertiary-care neonatal unit.

Methods: This prospective observational study included preterm infants born at < 33 weeks gestation. Infants with congenital anomalies of the kidney and urinary tract (CAKUT) or major malformations were excluded. Ultrasound scans were performed at 3-6 weeks of postnatal age to screen for NC using a modified grading system. Clinical data, including demographics, respiratory support, medication exposure, nutrition, and biochemical markers, were collected. Infants with NC were followed up at 3 and 6 months of corrected age to assess the resolution of NC and kidney function.

Results: Among the 152 enrolled neonates, 23 (15.1%) had NC. Respiratory distress syndrome (RDS) (adjusted odds ratio [aOR] 3.6; 95% CI: 1.1-12.3; p = 0.04) and total parenteral nutrition (TPN) (aOR-4.5; 95% CI: 1.2-16.8; p = 0.03) were independently associated with NC. At 3 months, 17 of the 23 infants were re-evaluated, and NC resolved in 13 (76.5%). By 6-8 months, all but one infant showed resolution. All the infants had normal kidney function at the last follow-up.

Conclusion: Nephrocalcinosis occurred in 15% of preterm neonates and was significantly associated with RDS and TPN use. Most cases resolved spontaneously without adverse outcomes. These findings support targeted NC screening in high-risk neonates.