When to start and discontinue kidney replacement therapy in acute kidney injury patients? A narrative review.

Acute kidney injury (AKI) affects up to 50% of critically ill patients, with mortality rates exceeding 40% in severe cases. Kidney replacement therapy (KRT) is a cornerstone in the management of severe AKI, yet the optimal timing for initiation and discontinuation remains uncertain. The debate between "early" initiation-guided by kidney injury biomarkers, trends in creatinine or urine output, and positive fluid balance-and "delayed" initiation-triggered by life-threatening complications-has been shaped by recent randomized controlled trials and meta-analyses, yet still lacks clearly defined parameters to guide clinical decision-making. Current evidence favors an individualized strategy that integrates AKI etiology and trajectory, comorbidities, clinical status, and response to conservative measures, aiming to prevent complications while maximizing renal recovery. Criteria for stopping KRT are less standardized and mostly derived from observational studies. Predictors of successful discontinuation include urine output >400 mL/day without diuretics or >2000mL/day with diuretics, creatinine clearance ≥15 mL/min and low biomarker levels. Combining at least two of these parameters, alongside clinical stability, increases the likelihood of sustained renal recovery. Determining the optimal timing for KRT initiation and discontinuation in AKI is a dynamic process requiring integration of clinical, biochemical, and functional data, and close multidisciplinary collaboration. This review synthesizes the best available evidence and proposes a practical, evidence-informed algorithm combining functional tests, biomarkers, and clinical criteria to guide nephrologists in optimizing KRT timing, with potential to improve outcomes and resource utilization.