Severe sepsis is the leading cause of acute kidney injury, although there is little mechanism of the pathogenesis of this subset of AKI in humans. Animal models have since directed attention to other lesions, such as apoptosis, leukocytic infiltration and thrombus formation. Kidney biopsy from post-mortem patients who died of septic shock showed the involvement of intense capillary leukocytic infiltration, apoptosis, and rare thrombi. Apoptosis and leukocytic infiltration, predominantly mononuclear, seem likely to be of major importance. Furthermore, the acute tubular lesions were correlated with the arterial lactate concentration. Thus, this indicated that the kidney lesions are integral to the severity of multiple organ failure.