Clinical Outcomes of Renal Pelvis Dilatation in Very Low Birth Weight Infants

Abstract

Purpose : The aim of this study was to evaluate this clinical outcome of neonatal pelvis dilatation in very low birth weight (VLBW) infants.

Methods : The medical records of 127 VLBW infants admitted to two neonatal intensive care units from January 2012 to December 2014 were retrospectively analyzed. Renal pelvis dilatation was diagnosed via ultrasound examination with cases divided into 3 groups: mild (dilatation of 5-10 mm), moderate (11-15 mm) and severe (≥15 mm). The correlation between the 3 dilatation groups and progression into hydronephrosis was evaluated.

Results : Among the 127 premature infants, renal pelvis dilatation was identified in 29 (22.8%) on ultrasound examination performed, on average 13.3 days after birth, combined with calyceal ectasia in 5 (3.9%) infants. At a postmenstrual age of 40 weeks, 18 infants (14.2%) had renal pelvis dilatation, 6 (5%) infants accompanied by a dilatation of the calyx. On the last follow-up performed when children were not older than 2 years old, renal pelvis dilatation had resolved to within normal limits in 23 (79%) infants while persisting in 6 (21%) infants; 1 mild, 3 moderate, and 2 severe pelvis dilatation. The median time-to-recovery of dilatation was 10.5 months (Kaplan-Meier curve), regardless of the severity of dilatation at birth. Based on receiver operating curve analysis, a cutoff diameter of renal dilatation at birth of 11.35 mm predicted persisting severe dilatation at the final follow-up (sensitivity 83.3%, specificity 82.6%).

Conclusion : Although premature infants with dilatation of mild severity were all recovered, some of those with moderate-to-severe dilatation progressed to hydronephrosis. Therefore careful follow-up of premature infants with renal pelvis dilatation is recommended.