Acute kidney injury (AKI) in the intensive care unit is common, devastating and costly. However, minimal evidence exists to guide the prescription of optimal renal replacement therapy (RRT). An important area of uncertainty surrounds the relative effects of convective versus diffusive modes of clearance. Although both clearance modes provide similar degrees of small molecule clearance, convective modes permit the enhanced clearance of larger-sized molecules which may mediate kidney and systemic toxicity in the setting of AKI.