Data on the use of renal replacement therapy (RRT) for AKI and for CKD in ICU patients are either on specific patient groups, such as cardiac surgery patients, based on surveys, or dates back for at least a decade. Furthermore, these studies suffered from exclusion bias, as patients who fulfilled criteria for initiation of RTT, but who were denied RRT, were not considered. That this may be an important consideration is illustrated by findings from a recent small single centre study that demonstrated similar mortality rate between RIFLE-F patients who were and who were not treated with RRT. Therefore, the Acute Kidney Injury Network (AKIN) recommended measuring the epidemiology of AKI.