Preterm Infants and Nephrocalcinosis

Nephrocalcinosis (NC), defined as calcification of renal tissue, has been reported to occur
in 7-41% of premature infants. Causes of NC are likely multi-factorial, and infants born
prematurely and with very low birth weight (<1500 gm) seem to be at the highest risk of
developing NC. Recent changes in recommendations for nutrition for the preterm infant such
as higher intakes of protein, calcium, and vitamin D may also play a factor in the
pathogenesis of NC.

Currently, diagnosis of NC often occurs incidentally during ultrasound evaluation for other
issues. Because there is no acute symptom or pattern of symptoms in the preterm population
associated specifically with NC, it is possible that many cases of NC may not be diagnosed.
Presently, it is impractical and costly to screen all infants for NC with renal ultrasound,
therefore there is no standard of care regarding screening for NC.

NC may have long-term effects. Studies have shown that preterm infants with NC had shorter
kidneys and a lower rate of tubule resorption of phosphorus (TRP) than preterm infants
without NC.

This study will analyze weekly urinalysis for all enrolled subjects prospectively and then
look at the incidence of NC at discharge of the enrolled subjects.