Abstract： Background Acute kidney injury (AKI) is associated with poor prognosis after cardiopulmonary bypass. The aim of this retrospective study was to investigate whether stent implantation before cardiopulmonary bypass has beneficial effect on development of AKI in renal artery stenosis (RAS) patients.Methods In this retrospective study, patients with abnormal baseline serum creatinine (SCr, ＞106 μmol/L) were not included. Included patients (n=69) were divided into two groups. Group 1 included 31 RAS patients receiving no stent implantation before cardiopulmonary bypass. Group 2 included 38 RAS patients having received stent implantation just before cardiopulmonary bypass. To assess AKI after cardiopulmonary bypass, serum urea nitrogen, SCr and creatinine clearance were recorded at baseline, at the end of operation, during the first and second postoperative 24 hours.Results Baseline characteristics were similar between groups. Serum urea nitrogen, SCr, creatinine clearance before and after cardiopulmonary bypass were also similar class groups. Incidence of AKI in group 1 was not significantly different from group 2. In group 1, AKI defined by RIFLE between occurred in 7 (22.6%) patients: 5 (16.1%) with RIFLE-R,2 (6.5%) with RIFLE-I, and no patients with RIFLE-F. In group 2, 10 patients (26.3%) had an episode of AKI during hospitalization: 6 (15.8%) had RIFLE-R, 4 (10.5%) had RIFLE-I, and no patients had RIFLE-F.Conclusions There are no data suggesting that it is necessary to stent RAS patients with normal SCr before cardiopulmonary bypass. However, it cannot be concluded that RAS is not associated with AKI after cardiopulmonary bypass.