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.
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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.
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
Aetiology
other infections (e.g. parasites) 9
drug/toxin-induced hepatitis (e.g. paracetamol toxicity, alcohol) 9
metabolic disease (e.g. nonalcoholic fatty liver disease, Wilson disease, haemochromatosis) 9
ischaemic (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:
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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
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variably present
may be more closely associated with hepatitis A
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:
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hepatomegaly
>15.5 cm at the midclavicular line 4
decreased attenuation around the portal system and at the hepatic hilum (periportal oedema) may be seen
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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 aetiologies of deranged serum liver function tests:
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T2:
increased T2 signal around the portal system (periportal oedema)
mild generalised increase in parenchymal signal intensity
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T1 C+ (Gd):
delayed, gradual periportal enhancement
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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.