Objective: Hydronephrosis, which is characterized with the dilatation of renal pelvis and/or calix is the most frequent antenatal renal anomaly. It was evaluated causes of perinatal hydronephrosis and effect to the renal functions in our study.

Materials and Methods: The study enrolled 65 patients with perinatal hydronephrosis diagnosed and followed in the department of pediatric nephrology. All patients were followed with ultrasonography (USG) after evaluated for the clinic and physic findings. Patients were assessed with voidingsistouretrography (VCUG) in terms of vesicoureteral reflux (VUR).

Results: 46 of cases were males (%70,8) and 19 (%29,2) were females. 44 of patients had (%67,7) unilateral hydronephrosis and 21 of patients (%32,3) had bilateral hydronephrosis. It was assessed as physiological hydronephrosis the cases which hydronephrosis regressed in terms of USG in the monitoring and VUR was not detected in the VCUG. There were 27 (%41) patients in physiological hydronephrosis group. The rest of 38 patients (%59) were assessed as pathological hydronephrosis. In terms of renal functions, the rate of urine protein / urine creatine was higher in cases with pathological hydronephrosis according to the cases with physiological hydronephrosis.

Conclusion: In the study, we come to conclusion that it is needed to define cases that are not constituted the problem in terms of diagnosis, monitoring and treatment for antenatal hydronephrosis and it is needed to abstain from unnecessary invasive procedure but on the other hand, it is should not be late for diagnosis of obstructive uropathy which could be caused the renal scar and it is needed dynamic approach to these cases.