Definition, diagnosis and epidemiology of acute-on-chronic liver failure.

This narrative review addresses the definition of acute-on-chronic liver failure, a condition associated with high short-term mortality in patients with chronic liver disease and/or cirrhosis. We provide two major points of view: the East and the West perspective. Both definitions vary regarding the underlying patient population and organ failure(s) definition. Nevertheless, all the definitions have their clinical utility: from the core concept of having the "liver" as a conditio sine qua non, the syndrome cannot exist (Asian Pacific Association for the Study of the Liver); a data-driven, robust definition (European Association for the Study of the Liver); a bedside tool that can quickly identify patients at high risk of dying (North American Consortium for the Study of End-stage Liver Disease [NACSELD]). In each section, we provide the overall definitions, the criteria of organ failure(s), and some epidemiological data illustrating how these apply in each area of the world.