Renal calcification in very low birth weight infants

Renal calcification in preterm infants has been described frequently. The etiologic factors have not yet been fully clarified. The objective of this study was to evaluate the incidence of and risk factors for renal calcification in our population.

We retrospectively reviewed the charts of very low birth weight preterm infants during a 1-year period. Renal ultrasound scans were performed at term or before discharge and at a corrected age of 1 year.

Six infants (6%) had renal calcification at term or before discharge compared with 96 who did not. Factors significantly associated with renal calcification included gestational age (26 weeks vs. 29 weeks, p=0.006), birth weight (851 g vs. 1141 g, p=0.004), duration of mechanical ventilation (69 days vs. 29 days, p=0.002), length of intensive care (72 days vs. 41 days, p=0.013), furosemide therapy (33% vs. 3%, p=0.027), and dexamethasone therapy (50% vs. 2% p=0.001). Birth weight and dexamethasone therapy had significant independent association after stepwise logistic regression analysis. Sex, oliguria, acidosis, duration of oxygen therapy, length of hospital stay, nutrition status, and nephrotoxic drugs did not differ between the two groups. Three of the six infants had spontaneous remission of renal calcification, whereas two patients without the finding in neonatal stage had renal calcification at a corrected age of 1 year.

The incidence of renal calcification in very low birth weight infants in this study was relatively low, and the calcification was transient in one-half of the infants. Extremely premature, sick infants requiring long-term ventilation, and those receiving furosemide or dexamethasone were more likely to have renal calcification. Clinicians should be aware that renal calcification may develop beyond the neonatal stage.