Abstract Background Ultrasound examination of the resistance index (RI) of both kidneys can provide evidence of renal artery stenosis. The extent to which the RI is changed after bridging stent-graft implantation due to altered flow characteristics is not known. Aims The aim of the study was to investigate the influence of renal bridging stent-grafts on the RI of the kidneys after fenestrated endovascular aortic repair (FEVAR). Methods Ultrasound examinations of the kidneys were conducted using a GE LOGIQ S7 XDclear ultrasound system (GE Medical Systems AG, Glattburg, Switzerland). The evaluation was performed according to SGUM 2D standard criteria. The RI was determined in all consecutive patients on the day before and after renal bridging stent-graft implantation. For this purpose, the kidneys were divided into 3 areas according to the standard protocol and 2 RI values were recorded per area by evaluating intrarenal arterial Doppler signals. Mean values were calculated and compared for each kidney. Results For 64 kidneys in 32 consecutive patients (73.9±7.8 years, 4 female, 28 male) treated with FEVAR and renal bridging stent–graft implantation pre- and postinterventional examinations were carried out. Sono-morphologically, the kidneys examined were inconspicuous (pre: size at least 107.1x52.4 mm, parenchymal margin 18.3 mm versus post: size at least 107.9x52.9 mm, parenchymal margin 18.6 mm, p>0.4). The arborization of the renal perfusion was preserved pre and post implantation. The RI did not differ before and after implantation (0.66±0.06 versus 0.67±0.07; p=0.10). None of the patients experienced severe impairment of renal function. Conclusion After successful implantation of a bridging stent-graft in a non-stenosed renal artery, there is no relevant change in the RI of the kidney. The RI seems therefore to be suitable for assessing renal perfusion after complex endovascular aortic therapy.