Ureteropelvic Junction Obstruction in Early Childhood: Comparison of Surgical Therapy and Surveillance. A Prospective, Randomized, Controlled Multi-Center Study

Inclusion Criteria: * unilateral ureteropelvic junction obstruction * diameter of renal pelvis greater 12 mm * partial renal function of 35%-55% proofed by scintigraphy * urodynamically relevant decrease in renal drainage proofed by diuresis scintigraphy at the age of 4 weeks up to 6 months * Abscence of clinical symptoms * Healthy contralateral kidney Exclusion Criteria: * Global decrease in renal function * renal dystopia * megaureter * vesico-ureteral reflux * progressive hydronephrosis * oligohydrammnion * voiding dysfunction * bilateral hydronephrosis * severe chronical illness * decrease of partial renal function of more then 5% during allocation