Acute hepatitis

Acute hepatitis occurs when the liver suffers an injury with a resulting inflammatory reaction. The cause of the injury can occur in multiple different ways, and imaging findings are often nonspecific. Ultrasound and MRI may be useful imaging modalities to suggest the diagnosis, but often the diagnosis is made from a combination of clinical presentation and laboratory values.

Epidemiology

The incidence of acute hepatitis depends on the etiology.

Clinical presentation

Patients often present with fever, abdominal pain, and jaundice. Multiple serum lab values are often elevated, including AST, ALT, and GGT. Depending on the degree of liver injury, lab values may indicate depressed liver function (e.g. decreased albumin). If the hepatitis is a result of viral infection, specific serum immunologic markers may be present (e.g. anti-HAV IgM indicates active hepatitis A infection).

Pathology

Acute hepatitis is a general term encompassing diffuse hepatocyte injury with resulting inflammatory change. The entire liver may be involved or only portions of it. Etiologies may include

• viral hepatitides: (e.g. hepatitis A, B, C, etc.)
  • acute viral hepatitis is distinguished from chronic viral hepatitis, by the duration of hepatitis and by differing histopathologic injury patterns
• parasites
• drug-induced/toxin-induced hepatitis (e.g. acetominophenacetaminophen/paracetamol toxicity, alcohol)
• autoimmune hepatitis
• steatohepatitis
• metabolic disease

Radiographic features

Ultrasound

• hepatomegaly (most sensitive sign)
  • >15.5 cm at the midclavicular line ⁴
• "starry sky appearance" has been found to have poor sensitivity and specificity ²
• gallbladder wall thickening
  • variably present
  • may be more closely associated with hepatitis A
• periportal edema
• color/spectral Doppler: normal

CT

Not a first line imaging modality for evaluation. Findings include

• hepatomegaly
  • >15.5 cm at the midclavicular line ⁴
• possible decreased attenuation around the portal system and at the hepatic hilum (periportal oedema)
• possible diffusely decreased parenchymal attenuation on noncontrast CT
  • diffuse oedematous change
  • hepatic steatosis may be a cause (steatohepatitis) or result of acute hepatitis
• possible periportal/hepatoduodenal lymphadenopathy

MRI

Findings on MRI are nonspecific and MRI is often used to exclude other etiologies of a serum liver function test disorder:

• T2:
  • increased T2 signal around the portal system (periportal oedema)
  • possible mild generalized increase in parenchyma signal intensity
• T1 C+ (Gd):
  • ​delayed, gradual periportal enhancement
• IP/OP:
  • hepatic steatosis may be apparent

Autoimmune hepatitis does not usually present with lymphadenopathy.

Treatment and prognosis

Treatment depends on the etiology of the acute hepatitis.