CT and MR imaging of benign hepatic and biliary tumors

Benign hepatic and biliary tumors can present a difficult diagnostic challe nge, Spiral computed tomography (CT) and magnetic resonance (MR) imaging ar e useful in the detection and characterization of these tumors. Imaging cha racteristics of lesions such as hepatic cyst, hemangioma, focal nodular hyp erplasia (FNH), and hepatic adenoma are well known. Hepatic cysts demonstra te water attenuation at CT, are isointense relative to water at MR imaging, and do not enhance after intravenous administration Of contrast material. Hemangiomas demonstrate characteristic nodular peripheral enhancement on ea rly-phase images with subsequent fill-in centrally at both modalities. FNH classically demonstrates intense early enhancement with washout on delayed images. Although hepatic adenoma can also demonstrate intense early enhance ment, it has a tendency to bleed and thus often appears more heterogeneous than FNH due to hemorrhage, Benign hepatic tumors that are less well descri bed in the imaging literature include hepatic lipoma or angiomyolipoma, inf antile hemangioendothelioma, and mesenchymal hamartoma, Hepatic lipoma has fat attenuation at CT, is isointense relative to fat at MR imaging, and doe s not enhance after intravenous administration of contrast material. Hepati c angiomyolipomas contain a variable amount of soft tissue in addition to f at and may therefore demonstrate enhancement at both modalities. The CT and MR imaging appearances of infantile hemangioma are similar to those of adu lt hemangioma, Infantile hemangioendothelioma occurs in infants under 6 mon ths of age and is typically a larger lesion. Mesenchymal hamartoma also occ urs in children, and its imaging appearance depends on the presence of stro mal elements and the protein content of the cyst fluid. Familiarity with th ese imaging features can help distinguish particular disease entities.