[Management of hydronephrosis prenatally diagnosed]

Hydronephrosis, defined as dilatation of the renal pelvis and/or calyces is most frequently detected by prenatal ultrasound. The initial postnatal ultrasound performed in the first 48 hours of life underestimated the degree of hydronephrosis in most newborns. We recommend initial postnatal sonogram at 7 days of life. Hydronephrosis is most commonly assessed by the Society for Fetal Urology [SFU] grading system or anterior-posterior diameter [APD] of the renal pelvis in the transverse plane. This classification is valid by postnatal ultrasound. Even degree of postnatal hydronephrosis was predictive factor for the need for surgery; hydronephrosis does not mean ureteropelvic junction obstruction [PUJO]. The natural history of hydronephrosis has shown that most resolve spontaneously. Investigations are not recommended if APD<10 mm. Antibiotic prophylaxis is not required if vesicoureteral reflux is excluded. Diuretic renography is useful in many cases to evaluate the degree of obstruction and determine differential renal function. With the excellent results of pyeloplasty, it is proposed for babies with congenital PUJO and <40% split differential function. A management algorithm is proposed