Nephrocalcinosis in preterm infants

Abstract

To determine the incidence of nephrocalcinosis a cohort of 124 preterm infants (32 weeks of gestation or less) was divided into 2 groups based on the presence of 1 or more of the following risk factors; prolonged use of furosemide, prolonged parenteral nutrition and oxygen requirement for at least 7 days. Urinary samples were taken to measure calcium and creatinine at 15, 21 and 30 days. Calcium/creatinine urinary ratio was analysed and hypercalciuria was defined as a calcium/creatinine urinary ratio of > 0.5. Renal ultrasounds were performed in both groups at 8 to 12 weeks. The control group included 71 patients, the study group of 53 all had risk factors. Nephrocalcinosis was found in 15.3% of the 124 patients. In the study group 35.8% had nephrocalcinosis and the calcium/creatinine ratio was higher (p < 0.01) in comparison to the control group (study group: 0.87, 0.96, 1.04 vs control group 0.37, 0.30, 0.29). In the control group no cases of nephrocalcinosis were found. Positive predictive value was 38% considering the presence of hypercalciuria for the diagnosis of nephrocalcinosis. The negative predictive value was 100%. We found an incidence of nephrocalcinosis similar to other international reports. It seems to be useful in patients with risk factors to study the calcium/ creatinine urinary ratio. Ecographic follow up is needed in those patients who present with hypercalciuria.