A prospective randomized controlled trial to evaluate different intervene strategy for severe infant hydronephrosis

INTERVENTION: Severe Hydronephrosis B‐Delayed Pyeloplasty Group:nephrostomy‐pyeloplsty;Severe Hydronephrosis B ‐ Direct Pyeloplasty Group:Pyeloplasty;Severe Hydronephrosis A ‐ Active Surveillance Group:Active Surveillance Gr;Severe Hydronephrosis A ‐ Direct Pyeloplasty Group:Pyeloplasty; CONDITION: Hydronephrosis PRIMARY OUTCOME: Split Renal Function;renal cortical thickness;serum creatinine; SECONDARY OUTCOME: time of drainage;Double J tube indwelling days; INCLUSION CRITERIA: 1. Children with hydronephrosis aged <= 3 months who visited the relevant medical center from January 2022 to December 2024. At the same time meet the following conditions to enter the severe hydronephrosis group A: (1) Ultrasound assessment 25mm <= APD < 35mm; (2) SFU grade is II or III (renal pelvis dilation under ultrasound, renal calyces visible or dilated); (3) Renal dynamic imaging assessment of affected renal function >= 40%; 2. Those who meet one of the following conditions enter the severe hydronephrosis group: (1) Ultrasound assessment APD >= 35mm; (2) SFU grade is grade IV (thinning of renal parenchyma); (3) The renal function assessed by dynamic renal imaging is less than 40%.