The Abdomen

Abstract

Focal liver lesions are present in more than 5 % of the population and are often detected incidentally when an imaging study is performed for another reason. In 40 % of cases, it is not possible to categorize such incidental lesions adequately by imaging ( Strobel and Bernatik 2006 ). Liver lesions are especially challenging for the radiologist interpreting whole-body screening MRI studies, which typically only include non-contrast-enhanced pulse sequences. With unenhanced MR images, only a crude characterization of focal liver lesions is possible.In the screening situation, we can roughly distinguish three categories of focal liver lesions: benign cysts and cyst-like lesions, benign solid masses, and solid malignancies (Table 8.1 ). Lesions with a cystic appearance such as dysontogenetic cysts, echinococcal cysts, and cavernous hemangiomas can be diagnosed with confi dence on the basis of an unenhanced MRI examination (including conventional T1-and T2-weighted sequences), and treatment recommendations can be made accordingly. This is not the case for solid liver lesions such as focal nodular hyperplasia, hepatocellular adenoma, metastasis, hepatocellular carcinoma, or cholangiocellular carcinoma. In most instances, a contrast-enhanced study is necessary to characterize solid liver lesions and estimate their total extent.