Intrahepatic gas: differential diagnosis.

Twelve patients with intrahepatic gas were examined with diagnostic sonography. In nine of the patients, gas was distributed within the intrahepatic biliary ducts, and, in four, distal acoustic shadowing was identified. Three patients, including one who also had biliary tract gas, had gas within the liver parenchyma but outside the biliary tract. One of these patients had a gas-forming abscess, another a recent biopsy, and a third had a necrotic metastasis following intraarterial chemotherapy. A final patient showed an evanescent pattern of gas within the portal venous system. Sonography can identify the presence and distribution of gas within the liver. When biliary tract air is identified, the possibility of biliary tract dilatation, masked by sonographic shadowing, must also be considered. In addition, in the presence of intrahepatic gas, prominent shadowing may cause disruption of the normal hepatic parenchymal pattern and lead to misdiagnosis of parenchymal abnormalities. By coordinating sonographic findings with the clinical history, however, a useful differential diagnosis may be obtained.