The liver is an important organ responsible for multiple functions to help support immunity, metabolism, digestion, vitamin storage, detoxification, and other essential functions. Hepatitis is an inflammation of the liver parenchyma that affects these vital liver functions. It can result from various causes, both infectious such as viruses, fungus, or bacteria and non-infectious agents such as alcohol, drugs, or toxins.The most common cause of hepatitis is infection with the virus. When the virus enters the bloodstream and reaches the liver, it infects the hepatocytes and multiplies. The body’s immune response becomes activated and tries to damage normal liver cells by mistake, causing inflammation and liver injury. In the United States, viral hepatitis is most frequently caused byhepatitis A virus,hepatitis B virus, and hepatitis C virus. Based on the duration of the inflammation, hepatitis is classified as acute or chronic. If the inflammation lasts less than six months, it is called acute hepatitis. In contrast, if the inflammation persists beyond six months, it is referred to as chronic hepatitis. All three mentioned viruses, hepatitis A, B, and C, can result in acute hepatitis; however, the hepatitis A virus is the most frequent cause. Hepatitis A is generally spread when people ingest the virus after consuming food or drinks contaminated by the stool of an infected person. 56
Spread typically occurs because of poor hygiene—for example, when an infected person prepares food with unwashed hands. Hepatitis A does not become chronic, which means that the infection does not last longer than six months. In contrast to the hepatitis A virus, acute infection with hepatitis B and C viruses typically results from contact with infected blood and can lead to chronic infection, potentially resulting in liver cirrhosis and liver cancer. Acute hepatitis’ clinical presentation depends on the underlying cause of the disease and may range from asymptomatic elevated liver function tests to fulminant liver failure. Individuals with acute viral hepatitis (most common) typically present with abdominal pain, nausea, vomiting, poor appetite, fever, jaundice, dark-colored urine, and pale stools. Associated physical findings may include hepatomegaly, splenomegaly, and ascites. Multiple serum laboratory values are often elevated, including AST, ALT, GGT, lactate dehydrogenase, bilirubin, PT/INR, and albumin.Acute hepatitis is typically a self-resolving condition that does not cause long-term complications. In rare cases, however, it can result in acute liver failure. Approximately 50% of patients with acute liver failure recover spontaneously, about 25% need a liver transplant, and the rest 25%, succumb.
Starry sky appearance of hepatic parenchyma in a patient with acute hepatitis. 57
ypical sonographic findings of acute hepatitis include hepatomegaly, overall decreased hepatic echogenicity, starry sky appearance, gallbladder wall thickening, periportal edema, and accentuated brightness of portal vein walls. Hepatomegaly is considered the most sensitive sign and represents a pathologic increase in the size of the liver. The liver is deemed to be enlarged if it measures over 15.5 cm at the midclavicular line.A starry sky liver appearanceis commonly associated with acute hepatitis. It refers to a sonographic appearance of the hepatic parenchyma in which there are bright echogenic dots throughout a background of decreased liver parenchymal echogenicity. This typical appearance is due to edema of liver cells that decreases the echogenicity of the liver. The edema further causes an alteration in sound properties and accentuates the walls of portal venous channels creating the appearance of bright dots on a hypoechoic background.Gallbladder wall thickening is defined as an increase in the thickness of the gallbladder wall greater than 3mm and is considered a highly sensitive sonographic feature of acute hepatitis. The gallbladder wall thickening in individuals with acute hepatitis may be explained by hepatocyte injury that leads to decreased bile production, resulting in reduced overall gallbladder volume and a relative increase in gallbladder wall thickness.
Additionally, hepatocyte necrosis can cause inflammation to be spread directly to the gallbladder, resulting in wall thickening. Typical CT findings of acute hepatitis include hepatomegaly, decreased attenuation at the hepatic hilum and around the portal system, diffusely decreased hepatic parenchymal attenuation, and possible periportal lymphadenopathy.It is important to mention that acute hepatitis is a clinical diagnosis, and normal imaging appearance of liver parenchyma does not exclude the diagnosis. Liver biopsy may be indicated if the diagnosis is unclear or the cause of inflammation is inconclusive. The management and prognosis of acute hepatitis depend on timely identification and elimination of the etiological agent causing the direct injury to the hepatocytes. As mentioned earlier, the most common cause of acute hepatitis is infection with the hepatitis A virus. Such cases typically resolve in 2 to 4 weeks with supportive treatment that involves IV fluids and rest.60-7
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