Objective To analyze the recovery of the renal function in the severe hydronephrosis children after percutaneous nephrostomy.Methods 50 cases of uretero-pelvic junction obstruction (UPJO) children were retrospectively studied from January 2013 to January 2016.There were 25 boys and 25 girls,and the mean age was 3.0 years (ranged from 2 months to 9 years and 7 months).The children were taken the percutaneous nephrostomy in the first stage and pyeloplasty or nephrectomy in the second stage according to the recovery of renal function.Split renal function,urine osmotic pressure,urine pH and urine β2-microglobulin (β32-MG) were compared between pre-operation and post-operation.The recovery of the renal function after the operation were evaluated by the single photon emission computed tomography (SPECT) and superb micro-vascular imaging (SMI) to analysis the feasibility of the pyeloplasty surgery in the severe hydronephrosis children.Result The postoperative renal function of 49 patients in the group recovered after percutaneous nephrostomy,only one child showed unrecoverable.After the first stage management,the renal cortical thickness [(5.9 ± 1.0)mm vs.(2.9 ± 0.9) mm,P =0.03],the separate renal function mmo]/L vs.(126.5 ± 100.5) mmol/L,P ＜ 0.001] were significantly improved compared with preoperation,andRI [(0.72 ±0.03) vs.(0.79 ±0.04),P=0.021],urine pH [(6.18±0.21) vs.(7.38 ± 0.32),P =0.039] and urine β2-MG [(562.16 ± 49.78) mg/L vs.(954.28 ± 69.45) mg/L,P ＜0.001] significantly reduced.Conclusions The renal function of the severe hydronephrosis children could be recoverable after the surgery of the percutaneous nephrostomy and pyeloplasty.Most children's kidneys suffered the severe hydronephrosis could be spared by surgery.SMI technology could provide reliable quantitative basis to evaluate renal function.