The recent article by Barba-Navarro et al1 assessed the effect of spironolactone on the incidence of acute kidney injury (AKI) following cardiac surgery, validating that spironolactone was not protective against cardiac surgery–associated AKI and demonstrating a trend toward risk. A strength of the study is the robust attempt to control for known risk factors that affect AKI; however, several important limitations were not addressed by the authors.