What are the hepatic and extrahepatic imaging features of cirrhosis?
Cirrhosis is histologically defined by presence of disorganized liver parenchymal architecture with areas of fibrosis and regenerative nodules. It is a major cause of death in the United States, where it is most often related to viral hepatitis (secondary to Hepatitis C virus [HCV] more commonly than Hepatitis B virus [HBV]), alcohol abuse, and cryptogenic causes (commonly related to NAFLD).
On CT and MRI, the morphologic changes of cirrhosis include enlargement or diminution of hepatic size, hepatic surface nodularity, hypertrophy of the lateral segment and caudate lobe, atrophy of the medial segment and right hepatic lobe (sometimes leading to enlargement of the pericholecystic space, also called the “expanded gallbladder fossa” sign), prominence of the hepatic fissures, and the “right posterior hepatic notch” sign, which manifests as a sharp indentation or notch along the right posterior hepatic contour. Hepatic steatosis, regenerative nodules, and hepatic fibrosis can also be seen.
Regenerative nodules generally appear similar to normal hepatic parenchyma, and on MRI, they typically appear isointense to hyperintense relative to liver parenchyma on T1-weighted images, often contain intralesional lipid, and are isointense to hypointense relative to liver parenchyma on T2-weighted images. Regenerative nodules can sometimes contain iron, called siderotic regenerative nodules, and instead have low signal intensity on in-phase T1-weighted images. No arterial phase enhancement is seen, but mild venous and delayed enhancement is usually present.
Hepatic fibrosis generally occurs in a diffuse lacelike pattern in the liver between regenerative nodules, is hypointense on T1-weighted images and mildly hyperintense relative to liver parenchyma on T2-weighted images, and demonstrates delayed phase enhancement. Sometimes, more geographic conglomerate regions of confluent hepatic fibrosis may also be encountered with similar signal intensity and enhancement characteristics, sometimes adjacent to areas of capsular retraction.
Extrahepatic findings of cirrhosis pertain to the presence and severity of portal hypertension and include ascites, splenomegaly, portosystemic varices, gallbladder wall thickening with submucosal edema, bowel wall thickening with submucosal edema, and subcutaneous or visceral fat edema. Reactively enlarged periportal and portacaval lymph nodes may also be seen.