Objectives: To determine: (1) the incidence in newborns of both significant urinary anomalies and mild hydronephrosis; (2) the degree of inaccuracy of prenatal sonography in our area, and (3) the evolution of neonatal hydronephrosis.
Methods: Using ultrasound, we examined 4,130 consecutive newborns, of which only 12 had a positive prenatal sonography. We distinguished 2 grades of hydronephrosis: mild (pelvic diameter between 5 and 15 mm), and significant (pelvic diameter > 15 mm).
Results: In the 'normal' newborns (with negative prenatal sonography), we found 0.9% significant urinary anomalies and 5.2% mild hydronephroses. Mild hydronephroses improved or disappeared spontaneously in 82% of the cases. 50% with significant dilatation required surgical correction.
Conclusions: Neonatal ultrasound screening is essential for the early detection of uropathies missed on prenatal examination. The majority of mild hydronephroses detected in the newborn improve or disappear spontaneously. We hypothesize a relationship between the degree of dilatation, obstruction and evolution.