Definition of Acute Liver Failure
Acute liver failure (ALF) is defined as the rapid development of hepatocellular dysfunction with coagulopathy (INR >1.5 or prothrombin time ratio <50%) and hepatic encephalopathy occurring within 26 weeks of symptom onset in a patient with no preexisting liver disease. 1, 2
Essential Diagnostic Components
ALF requires all of the following elements to be present for diagnosis:
- Absence of preexisting liver disease - this is the critical distinguishing feature that separates ALF from acute-on-chronic liver failure (ACLF) 1, 3
- Coagulopathy - defined as INR >1.5 or prothrombin time ratio <50% 4, 1
- Hepatic encephalopathy - any grade of altered mental status attributable to liver dysfunction 1, 5
- Rapid deterioration - symptom onset to liver failure occurring within 26 weeks 4, 1
Severity Stratification
ALF can be further classified based on severity 4, 1:
- Severe ALF: Prothrombin time ratio <50% without encephalopathy 4
- Serious ALF (Fulminant Hepatitis): Prothrombin time ratio <50% combined with encephalopathy 4, 1
The term "fulminant hepatitis" specifically refers to encephalopathy developing within 15 days of jaundice onset, though this terminology is often used interchangeably with serious ALF 4.
Critical Distinction: ALF vs ACLF
Do not diagnose ALF in any patient with known cirrhosis or chronic liver disease - these patients have ACLF by definition, even if previously compensated 1. ACLF represents acute decompensation in patients with underlying chronic liver disease and is associated with extrahepatic organ failures, requiring different management and carrying different prognosis 4, 6.
Epidemiology and Prognosis
- ALF is rare, occurring in fewer than 10 cases per million persons annually in developed countries 4, 1
- With modern intensive care and liver transplantation, approximately 90% two-year survival can be achieved in transplanted patients 4, 1
- Paracetamol-induced ALF without transplantation can achieve 90% survival with appropriate management 4
Common Pitfall to Avoid
The most critical error is misclassifying ACLF as ALF - always verify the complete absence of preexisting liver disease before diagnosing ALF, as management strategies and transplant prioritization differ substantially between these two entities 1, 6.