Renal replacement therapy (RRT) has become an increasingly used form of organ support for hospitalized patients with acute kidney injury (AKI), particularly those in critical care units.1,2 Clinical trials published during the past decade have investigated several aspects of the RRT prescription, including the optimal dose,3,4 ideal modality,5 and most effective method of anticoagulation.6 The more fundamental question of when to commence RRT in AKI has remained unanswered. Meta-analyses of mostly observational studies examining this controversy have suggested a survival benefit with earlier RRT initiation.