**5. Evolution and treatment**

Renal pelvic dilatation is commonly seen during antenatal ultrasound examinations, and its management remains a clinical dilemma. Although it is proven that severe antenatal hydronephrosis requires postnatal clinical and ultrasound evaluation, there is no consensus on the follow-up and management of mild or moderate hydronephrosis observed during antenatal ultrasound examinations [15]. The prenatal diagnosis may improve the prognosis and the outcome of the fetus. An early diagnosis and treatment of urinary obstruction may prevent the renal damage or loss of renal function [5, 21].

Most of the cases will spontaneously resolve after delivery. Thus, some assurance should be given. Many studies suggest follow-up when the AP diameter is 4–7 mm and antibiotic therapy when the AP diameter is greater than 7 mm [14, 18].

The postnatal assessment of fetal hydronephrosis may be invasive and lengthy [6–8]. Thus, the risks and the inconvenience of a protracted evaluation need to be weighed against the probability that milder degrees of renal pelvic dilatation will decrease without resulting in any renal damage [17].
