Acute hepatitis

Acute hepatitis (plural: acute hepatitides) occurs when the liver suffers an injury with a resulting inflammatory reaction. The cause of the injury can happen in multiple different ways, and imaging findings are often non-specific. Acute hepatitis is a clinical diagnosis and a normal imaging appearance of the liver does not exclude it ⁷.

Epidemiology

The incidence of acute hepatitis depends on the aetiology.

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. Aetiologies may include:

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

Radiographic features

Ultrasound

Described features include:

• 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 oedema
• accentuated brightness of portal vein radicle walls
• colour/spectral Doppler: normal
• the overall echotexture is often decreased ^5,6

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 a result of acute hepatitis
• possible periportal/hepatoduodenal lymphadenopathy

MRI

Findings on MRI are non-specific, and MRI is often used to exclude other etiologies of deranged serum liver function tests:

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

Autoimmune hepatitis does not usually present with lymphadenopathy.

Treatment and prognosis

Treatment depends on the aetiology of acute hepatitis.