Correlation of Prenatal and Postnatal Ultrasound Findings With the Incidence of Vesicoureteral Reflux in Children With Fetal Renal Pelvic Dilatation

Purpose: Up to 1% of prenatal ultrasounds detect renal pelvic dilatation. This dilatation is associated with vesicoureteral reflux but its clinical significance and the necessity for vesicoureteral reflux detection have been questioned. We report an evaluation of fetal renal pelvic dilatation and postnatal sonographic features with the incidence of vesicoureteral reflux. Materials and Methods: Maximum fetal renal pelvic dilatation was prospectively measured at a single center between 1990 and 2003. Dilatation 4 mm or greater at less than 33 weeks of gestation, or 7 mm or greater at more than 33 weeks was the threshold for inclusion in the study. Postnatal evaluation included ultrasound and voiding cystourethrogram. Postnatal data included vesicoureteral reflux incidence and grade, and caliceal and ureteral dilatation on ultrasound. Results: Of 215 neonates 46 (21%) had vesicoureteral reflux. Mean renal pelvic dilatation was 14.4 mm in those with reflux, which was not statistically different than the mean of 11.8 mm in 169 with a normal voiding cystourethrogram. ROC analysis revealed that fetal renal pelvic dilatation was a poor discriminator of reflux. Reflux was identified in a significantly greater number of neonates with vs without postnatal calicectasis (20% vs 9%, p <0.05). When fetal renal pelvic dilatation was combined with postnatal calicectasis, only 5% of infants with dilatation less than 10 mm and isolated renal pelvic dilatation had reflux, whereas reflux was identified in 25% with fetal renal pelvic dilatation 10 mm or greater and calicectasis (p <0.02). Conclusions: The magnitude of fetal renal pelvic dilatation is not reliably predictive of reflux and this measure alone cannot be used to direct postnatal cystography. However, postnatal calicectasis appears to be an important predictor of vesicoureteral reflux in children with fetal renal pelvic dilatation. Expectant management can be considered in the subset of newborns with minimal dilatation (less than 10 mm) and absent calicectasis.