Background The delayed diagnosis of pelvi-ureteric junction (PUJ) disruption in children following blunt abdominal trauma can result in loss of function of the involved kidney. We examined the potential for kidney preservation and the limits of diagnostic delays. Methods A retrospective review of 17 cases of PUJ disruption at Beijing Children's Hospital from 1993 to 2009 was done with respect to diagnosis, treatment and follow-up. Results The interval from trauma to diagnosis of PUJ disruption was (52 +/- 52) days. If one case with nephrectomy was excluded, the interval from trauma to diagnosis was (40 +/- 20) days. The average time between injury and first treatment was (49 +/- 25) days. Pelvi-ureteric reanastomosis and caliceal ureterostomy were performed separately in 11 and 4 patients, respectively. Ileal replacement for ureter injuries was finally performed in one patient. Hydronephrosis of the injured kidney was reduced and the function improved in 15 out of 17 patients (88%). Only one patient received nephrectomy and the nephrectomy rate was 5.9%. Conclusion Differential renal function at the PUJ disruption side can be saved and the rate of nephrectomy reduced by appropriate surgery if the time to diagnosis and first treatment is limited to within two months. Chin Med J 2011;124(15):2290-2296