慢加急性肝衰竭（acute-on-chronic liver failure， ACLF）是在慢性肝病基础上，短期内出现肝功能急性失代偿的临床综合征，其特征是常伴发多器官功能衰竭，短期病死率高。由于病因和诱因等的差异，东西方对于ACLF的定义、诊断标准仍存在分歧。2014年世界胃肠病学组织（World Gastroenterology Organization， WGO）在各大定义的基础上综合考虑，根据基础肝病类型将ACLF分为在非肝硬化基础上发生的A型ACLF，在代偿期肝硬化基础上发生的B型ACLF和在既往失代偿肝硬化基础上发生的C型ACLF。然而不同分型的ACLF具有不同的病理生理，从而导致在易感性、诱发因素、损伤反应、器官功能衰竭和死亡率上存在明显差异，而使用国际上用于评估脓毒症预后的PIRO（predisposition， injury， response， and organ failure） 概念有助于全面认识不同分型乙肝相关慢加急性肝衰竭（hepatitis B-related acute-on-chronic liver failure， HBV-ACLF），从而改善管理，提高ACLF生存率。

Acute-on-chronic liver failure （ACLF） is generally accepted as a clinical syndrome characterized by an acute hepatic insult and rapid deterioration of liver function in patients with pre-existing chronic liver disease in combination with multi-organ failure with high short-term mortality. Because of the differences in etiology and inducement， there are different definitions and diagnostic criteria of ACLF in the East and West. Attempting to cover all ACLF diagnosed， WGO defined ACLF into three categories in 2014： patients with CLD but no cirrhosis （type A）， compensated cirrhosis （type B）， and decompensated cirrhosis （type C）. However， different types of ACLF have different pathophysiology， which leads to obvious differences in predisposition， injury， response， organ failure and mortality among different types of ACLF. The concept of PIRO， which is similar to that used in determining outcomes of sepsis， is contribute to comprehensively understand different types of HBV-ACLF， improve management. Therefore， it is of great significance to improve the survival rate of ACLF.