Introduction

Since the advent of fetal ultrasonography in the late 1970s, and the introduction of the systematic antenatal screening of hydronephrosis, the clinician is faced with an important population of infants with hydronephrosis. Dilatation of the fetal collecting system is observed in about 0.25% of pregnancies.1 Beside entities such as urethral valves, vesicoureteral reflux, hydro-ureteronephrosis or complicated duplex kidney, isolated pelvic dilatation will conceivably be the result of pelviureteric junction stenosis (PUJ). These neonates with PUJ are in good health and present no symptoms. The natural history of this condition, as well as its optimal management, are still a matter of debate. In contrast, obstruction in adults is often discovered on the basis of symptoms related to a heavy underlying pathology, and the controversy around the therapeutic attitude is less controversial.