Renal resistive index (mean±95% CI) for cardiac surgery patients in two studies. Values from (A) Bossard et al., [3] stratified by AKI status and determined postoperatively by transabdominal ultrasound and (B) the current study, stratified by aortic valve status, determined prior to CPB. Notably, pre-intervention values in the AI and AI/AS subgroups from the current study considerably overlap post-intervention values in the AKI subgroup. The horizontal hatched line reflects the RRI threshold (>0.74) for AKI prediction developed by Bossard et al. AI-aortic insufficiency, AI/AS-combined aortic insufficiency/stenosis, AKI-acute kidney injury.