Description

Acute hepatitis is a clinical diagnosis characterized by acute inflammation or injury to hepatocytes, resulting in fever, abdominal pain, jaundice, and elevation of liver function tests. The cause of the injury may be viral (e.g. acute viral hepatitis A) or non-viral (e.g. drug-induced, alcoholic, or autoimmune acute hepatitis). Whilst normal imaging appearance of the liver does not exclude the diagnosis, CT and MRI features of acute hepatitis may include hepatomegaly, periportal edema (e.g. decreased attenuation on CT and increased T2 signal on MRI around the portal system and at the hepatic hilum), diffusely decreased parenchymal attenuation on noncontrast CT corresponding to areas of mild generalized increase in parenchymal signal intensity on T2-weighted images and decreased signal intensity on T1-weighted images, and occasionally areas of steatosis on chemical shift sequence. On post-contrast CT and MRI, the presence of heterogeneous enhancement and ill-defined regions of reduced enhancement along with reduced uptake of hepatobiliary contrast agents may simulate infiltrative HCC. The acute clinical onset, the presence of periportal edema, gallbladder wall thickening, and the reversibility of the heterogenous enhancement with improvement of liver function are useful tips for differential diagnosis. Imaging findings of acute hepatitis are nonspecific and final diagnosis is clinically made.