Risk factors associated with nephrocalcinosis in preterm infants

The objective was to identify the risk factors associated with nephrocalcinosis (NC) in preterm infants.

NC was diagnosed by renal sonography at 4 or 8 weeks of life, and 10 infants who had findings of type 3 or 4 NC were classified as the NC group. Various clinical and laboratory factors were compared between NC and control groups.

Serum sodium (Na) on day 1, serum creatinine and fractional excretion of calcium (FeCa) at 1 and 2 weeks, and serum calcium (Ca), fractional excretion of sodium (FeNa), and urine Na on 2 weeks of life were significantly different between the two groups: the NC group showed significantly higher serum creatinine, FeNa, and FeCa than the control group, suggesting a greater decrease in renal function in the NC group. Differences of the laboratory findings disappeared after 4 weeks of life. The strongest risk factor was birth weight.

A transient decrease in renal function during the first 2 weeks of life was associated with development of NC in preterm very low-birth-weight infants, and the risk of NC increased as birth weight decreased.