Kidney and urinary tract anomalies are among the most frequently identified congenital malformations accounting for 20–30% of all ultrasound-detected anomalies¹. Antenatal US is an excellent technique for their detection, with an overall sensitivity of approximately 90%^1,2.

Antenatal hydronephrosis (ANH) is the dilation of the fetal renal collecting system and corresponds to the most common urinary tract anomaly detected on prenatal ultrasonography (US), being reported in approximately 1-5% of all pregnancies³. Usually ANH is physiologic or transient, having no pathological meaning⁴. However it can represent important conditions such as posterior urethral valves or vesicoureteral reflux. Most frequently its etiology cannot be determined before birth, requiring postnatal US follow-up and eventual voiding cystourethrogram.

Our objectives are to determine the frequency of each urinary tract anomalies diagnosed with prenatal ultrasound, to correlate prenatal and postnatal diagnoses and to establish prognostic factors.