Underreporting of Acute Kidney Injury in Randomized Trials of ARDS with Mortality Endpoints: A Systematic Review

Background Acute Kidney Injury (AKI) is a frequent complication among patients with Acute Respiratory Distress Syndrome (ARDS), and its definition has evolved significantly over the past two decades. We conducted a systematic review to evaluate how AKI was defined in randomized controlled trials (RCTs) involving ARDS patients and whether changes in AKI definitions impacted mortality outcomes. Methods This systematic review was registered on PROSPERO (CRD420251043094). We searched PubMed/MEDLINE, Embase, and Cochrane databases up to December 2023 for RCTs that reported AKI in ARDS patients. Studies were grouped according to the AKI definitions used: RIFLE, AKIN, KDIGO, or undefined. Descriptive statistics and mortality trends were assessed across groups. Results A total of 39 RCTs were included. Only 15 studies (38.4%) adopted standardized definitions for AKI—5 used RIFLE, 4 used AKIN, and 6 used KDIGO. The remaining 24 studies (61.5%) did not clearly define AKI. Among studies using KDIGO, mortality rates for AKI patients ranged from 32–56%, whereas those without defined criteria reported broader and less consistent mortality outcomes. There was no consistent trend indicating improved mortality outcomes with more recent definitions. Conclusions Despite the evolution of AKI diagnostic criteria, most RCTs on ARDS still lack standardized definitions for AKI. This heterogeneity limits comparison across trials and impairs the accuracy of clinical interpretations. The implementation of KDIGO criteria should be encouraged in future ARDS-related research to improve standardization and comparability.