Differentiating Viral from Ischemic Hepatitis

Key Biochemical Patterns

Ischemic hepatitis typically produces extremely high transaminase peaks with AST often higher than ALT, and serum bilirubin usually <3 mg/dL despite massive transaminase elevation 1
Viral hepatitis shows elevated aminotransferases but with proportionally lower lactate dehydrogenase (LD) elevation relative to ALT, and serum bilirubin typically >3 mg/dL (>50 μmol/L) with AST/ALT >400 IU/mL 1

Ischemic hepatitis produces deep, marked coagulopathy (INR significantly elevated) that improves rapidly with restoration of perfusion 1
The coagulopathy in ischemic hepatitis is disproportionately severe relative to bilirubin elevation 1

All patients with hepatitic LFT patterns require viral serology testing, including anti-HAV IgM, HBsAg, anti-HBc IgM, anti-HCV, HCV RNA, anti-HEV IgM, and HEV RNA 1, 2, 4, 5
Test for HEV as part of first-line investigation regardless of travel history, as it is now the commonest cause of acute viral hepatitis in many countries 4

Calculate ALT/LD ratio immediately, with a ratio >1.5 suggesting viral hepatitis and a ratio <1.5 suggesting ischemic hepatitis or drug toxicity 2
Assess temporal pattern, with rapid peak and return to normal in 3-11 days suggesting ischemic hepatitis, and gradual rise with prolonged elevation suggesting viral hepatitis 1, 2
Evaluate bilirubin-transaminase relationship, with massive transaminases and bilirubin <3 mg/dL suggesting ischemic hepatitis, and transaminases >400 IU/mL with bilirubin >3 mg/dL suggesting viral hepatitis 1, 2
Review cardiovascular status, with evidence of low cardiac output, heart failure, or shock supporting ischemic hepatitis, and absence of cardiovascular compromise favoring viral or drug-induced hepatitis 2, 5
Obtain viral serology and imaging, with negative viral serology and vascular patency confirmed suggesting ischemic hepatitis, and positive viral serology confirming viral hepatitis 1, 2, 4