CT characteristics of primary hepatic mass lesions in dogs.

Little information is available on the relationship between computed tomography (CT) imaging findings and the pathologic diagnosis of canine hepatic tumors. Our purpose was to clarify the characteristic features of CT findings in liver tumors in dogs. Data from 33 dogs with either a hepatocellular carcinoma, n = 14, hepatocellular adenoma, n = 14, or nodular hyperplasia, n = 5 were summarized from medical records. CT features for each histologic diagnosis were characterized and analyzed statistically. Common findings in hepatocellular carcinoma included central (79%, P = 0.0030) and marginal enhancement (93%, P = 0.00043) in the arterial phase, cyst-like lesions (93%), capsule formation (93%), and hypoattenuation in the portal (86%), and equilibrium phases (93%). Hepatic adenoma was characterized by a characteristic diffuse enhancement pattern during the arterial phase (57%, P = 0.013), which was also found in nodular hyperplasia (60%), but never in hepatocellular carcinoma. Nodular hyperplasia was less likely to have a capsule structure (20%, P = 0.0087). Mass size was significantly smaller in nodular hyperplasia than in hepatocellular carcinoma and hepatic adenoma (P = 0.0033 and 0.038, respectively). Hyperattenuation in the arterial and the portal phase i.e. contrast retention, was more frequent in hepatic adenoma than in the other groups (P = 0.037 and 0.037, respectively). Nodular hyperplasia was more frequently isoattenuating in the equilibrium phase (P = 0.043).