Definition and classification of acute-on-chronic liver diseases.

Patients with chronic liver diseases (CLDs) develop acute liver injury and/or acute decompensation under the attack of various precipitants and present with significantly elevated alanine aminotransferase and/or total bilirubin levels, liver failure, or acute decompensation of liver cirrhosis, which is called acute-on-CLD (AoCLD). AoCLD accounts for the majority of patients hospitalized in the Department of Hepatology or Infectious Diseases. AoCLD is complicated by various clinical types, the severity of the disease, and may pose a high risk of death. To date, the definition of AoCLD is still vague, and a consensus concept of the clinical classification is lacking. This review aimed to define the concept and clinical types of AoCLD based on related studies and the literature.