Incidence, ultrasonic patterns and resolution of nephrocalcinosis in very low birthweight infants

This longitudinal study was undertaken in order to elucidate the incidence and natural course of nephrocalcinosis in preterm infants and to evaluate w hether the ultrasonic classification for nephrocalcinosis used here is suit able for predicting subsequent resolution of the condition. A total of 129 very low birthweight infants were screened for nephrocalcinosis by renal ul trasonography at 2 wk, 6 wk and 3 mo. The pyramidal changes were classified as peripheral, scattered or extensive. Follow-up renal ultrasonography was performed on the infants with nephrocalcinosis at 6, 12, 18 and 24 mo, and thereafter annually up to 6 y of age, or until ultrasonic resolution. The overall incidence of nephrocalcinosis was 20% (26/129). Nephrocalcinotic ch anges were peripheral in 14 out of the 26 infants (54%), scattered in 7 (27 %) and extensive in 5 (19%). Ultrasonic resolution had taken place in all t he cases with peripheral nephrocalcinosis by 12 mo, but 3 of the 7 infants with the scattered pattern and 3 of the 3 with the extensive pattern (1 die d) were still affected at 24 mo. In two cases with extensive nephrocalcinos is the condition still persisted at 5-6 y of age. We conclude that about 20 % of very low birthweight infants develop nephrocalcinosis during the first 3 mo of life. In about half of the affected infants renal changes are rest ricted and transient, but more extensive forms may last several pears. The classification of nephrocalcinosis used here is appropriate for predicting later ultrasonic resolution.