This is a case report of bilateral hydronephrosis detected at 30 gestational week. The patient assisted with a diagnosis of abnormal dilation of both ureters, asymptomatic, with normal fetal movements and without vasospasm symptoms. She brought her detail ultrasound (13/01/2016) reporting bilateral hydronephrosis (right kidney III/IV; left kidney II/IV); and a second ultrasound with abnormal implantation of both ureters with bilateral hydroneprosis. Fetal hydronephrosis is the most common congenital anomaly detected by ultrasound. It is the abnormal dilation of urinary canals, and its most frequent cause is physiologic (48%), that resolves spontaneously. Almost, there are some pathologic causes: pelvi-ureteric junction obstruction (11%), extrarenal pelvis (15%), vesicoureteral reflux and megaureter (9%), ureterocele and double kidney (2%), and posterior urethral valves (1%). The most frequent complication is the renal failure. During prenatal and postnatal period, ultrasound is the election diagnostic method. The urinary tract anomalies are 20% of all congenital anomalies. In fact, hydroneprosis have an incidence of 2–5,5%, and a newborn prevalence of 0,5 – 4,5%. Only 17 – 30% are bilateral with a poor prenatal prognosis. In the second and third trimester oligohydramnios is the first cause; and in the postnatal period this is the first cause of permanent renal impairment. The objective of this report is to present a case of bilateral hydronephrosis, with its diagnosis and treatment, and to stand out the importance of prenatal ultrasound diagnosis, the election of a surgical vs expectant treatment, and the short and medium term follow-up. Because of the detection of fetal hydronephrosis is an indicator of renal disease in newborns, it is important to make a prenatal opportune diagnosis to prevent pyelonephritis, urinary tract obstruction and renal failure.