THE SELECTION CRITERIA OF EARLY INTERVENTION IN CONGENITAL HYDRONEPHROSISMostafa K. Ammar, Abdalla A. Ali and Abd El-Rahman M. El-FayoumiDepartment of Urology, Faculty of medicine, Zagazig UniversityPurpose: Unilateral hydronephrosis does not necessarily represent obstruction and may spontaneously improve or resolve postnatally.Materials and Methods: A total 30 newborns with antenatally diagnosed, primary asymptomatic hydronephrosis were followed nonoperatively unless evidence of renal deterioration occurred for which pyeloplasty was performed.Results: Of the 30 patients, 15 patients (50%) were managed conservatively, 4 patients (13%) underwent early pyeloplasty and 11 patients underwent delayed pyeloplasty. Grade 4 hydronephrosis was in 13% of the conservative group and 100% &27% in the surgical groups (early and delayed). The conservative group had an APD < 20mm in 87% and surgical groups (early and delayed) had an APD 20mm in 100% and 82%. In the conservative group all patients had initial DRF 40. Regarding to the initial drainage pattern, the conservative group showed non-obstructed pattern. 100% and 36% obstructed pattern were in the surgical groups (early and delayed). The initial t1/2, in the surgical groups (early and delayed) had 75% and 73% of greater than 20 min. Patients with an initial t1/2 of less than 10 min had tendency for conservative management.Conclusions: Unilateral newborn hydronephrosis appears to be relatively benign and nonoperative treatment with close follow up during the first 2 years is safe and recommended.