In the last decades, a lot of research has been done to improve our understanding of acute kidney injury (AKI) as well to standardize its diagnostic criteria. As a result of many years of work of intensivists and nephrologists, consensus definitions were established, finally unified in 2012 by the Kidney Disease: Improving Global Outcomes (KDIGO) group. These criteria refer to the time of AKI development and are based on serum creatinine level increase and / or urine output decrease. Acute kidney injury is defined as an increase in serum creatinine levels by at least 0.3 mg/dl within 48 hours or 1.5‑fold the baseline, which is known or presumed to have occurred within the preceding 7 days, or-according to the urine output criterion-urine volume less than 0.5 ml/kg/hour for at least 6 hours. The present review covers issues discussed during the KDIGO controversy conference, devoted to AKI. Here, we attempted to answer 3 main questions: Is the KDIGO definition of AKI valuable in clinical research and global epidemiology? Is it helpful in everyday clinical practice? Is it useful in the treatment of critically ill patients with AKI?