Clinical spectrum of antenatally detected urinary tract abnormalities with respect to hydronephrosis at postnatal ultrasound scan

The purpose of this study was to compare the outcome of infants having antenatally detected urinary tract abnormalities (AUTAs) with respect to the presence of hydronephrosis in postnatal ultrasonography (US) examination. Between January 1999 and October 2009, 256 infants diagnosed with AUTAs were prospectively followed. Infants were divided into two groups according to the presence of hydronephrosis in postnatal US examination: Group 1, infants with hydronephrosis; Group 2, infants without hydronephrosis (including renal cyst, agenesis, ectopic kidney). The events of interest were the presence and diagnoses of uropathy, AUTA resolution, urinary tract infection (UTI), development of renal parenchymal defects (RPDs)-focal or global scarring, dysplasia-, acute kidney injury (AKI) and chronic kidney disease (CKD), and the need for surgery and dialysis treatment. The most commonly detected underlying abnormalities were ureteropelvic junction obstruction (44.8 %), vesicoureteral reflux (VUR) (30.0 %) and megaureter (9.5 %) in patients with postnatal hydronephrosis. On the other hand, multicystic dysplastic kidney (43.5 %), renal agenesis (19.4 %) and VUR (19.4 %) were mostly encountered abnormalities in patients without postnatal hydronephrosis. RPDs were significantly more common among patients with postnatal hydronephrosis compared to those without hydronephrosis (37 vs. 21 %, P = 0.02). The incidence of UTI and VUR was higher in infants with postnatal hydronephrosis than in infants without hydronephrosis. There was no statistically significant difference in terms of the development of AKI and CKD and the need for surgery and dialysis treatment between patients with hydronephrosis and those without hydronephrosis. Infants with AUTAs should be investigated postnatally. The findings from this study will help to identify the natural history and outcome of infants with AUTAs according to the postnatal US parameters.