Timing of renal replacement therapy in acute kidney injury

Acute kidney injury (AKI) is a frequent finding in patients with critical illness. In many of these patients renal replacement therapy (RRT) is needed to support organ dysfunction. Although international guidelines on the management of AKI have been developed and are widely accepted, there is still considerable controversy on the optimal timing of RRT. The clinician is in a constant dilemma that level of evidence (on timing of acute RRT) is low and the issue is of high importance. Despite this paucity of high quality prospective data, this review will give the reader an idea on how to approach the difficult question of initiating RRT. Obviously, no general recommendation can be given covering every aspect of intensive care medicine. Therefore, general thoughts are displayed, followed by a focus on specific clinical situations. The role of "novel" biomarkers in the process of deciding when to start is also discussed.