Acute hepatitis

Acute hepatitis occurs when the liver suffers an injury resulting in an inflammatory reaction. There are a variety of causal etiologies and imaging findings are often non-specific. Acute hepatitis is primarily a clinical diagnosis and a normal imaging appearance of the liver does not exclude it's diagnosis ⁷.

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.

Histologically, acute hepatitis manifests as a lobular hepatocellular injury with features of hepatocellular swelling, apoptosis, or loss.

Six morphologic subpatterns of acute hepatitis are described:

• inflammation predominant pattern

• cholestatic pattern

• toxic pattern

• resolving pattern

• giant cell pattern

• mild nonspecific pattern

Etiology

• viral hepatitides ⁹

  • hepatotropic viruses (e.g. HAV, HCV, HBV, etc.)

  • non-hepatotropic viruses (e.g. EBV, CMV, HSV, etc.)

• other infections (e.g. parasites) ⁹

• drug/toxin-induced hepatitis (e.g. acetaminophen toxicity, alcohol) ⁹

• autoimmune hepatitis ⁹

• metabolic disease (e.g. nonalcoholic fatty liver disease, Wilson disease, hemochromatosis) ⁹

• ischemic (e.g. systemic shock, Budd-Chiari syndrome) ⁹

• pregnancy-related (e.g. HELLP syndrome, acute fatty liver of pregnancy) ⁹

• primary graft dysfunction after liver transplantation ⁹

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 edema

• accentuated brightness of portal vein radicle walls

• color/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

• decreased attenuation around the portal system and at the hepatic hilum (periportal edema) may be seen

• diffusely decreased parenchymal attenuation on noncontrast CT

  • diffuse edematous 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 edema)

  • mild generalized 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 etiology of acute hepatitis.