Tuberculosis is a disease whose incidence has increased principally as a consequence of HIV infection and use of immunosuppressive drugs. The abdomen is the most common site of extrapulmonary tuberculosis. It may be confused with several different conditions such as inflammatory bowel disease, cancer and other infectious diseases. Delay in the diagnosis may result in significantly increased morbidity, and therefore an early recognition of the condition is essential for proper treatment. In the present essay, cases with confirmed diagnosis of abdominal tuberculosis were assessed by means of computed tomography and magnetic resonance imaging, demonstrating the involvement of different organs and systems, and presentations which frequently lead radiologists to a diagnostic dilemma. A brief literature review was focused on imaging findings and their respective prevalence.

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Most malignant liver tumors are represented by hepatocellular carcinoma and cholangiocarcinoma; however a variety of other uncommon hepatic lesions might also be found. Common lesions such as hemangioma, focal nodular hyperplasia and metastases are well known and have already been extensively documented in the literature. The diagnosis of typical hepatic lesions may be done with some reliability by means of several imaging methods; on the other hand, uncommon lesions normally represent a diagnostic challenge for the radiologist. In this first part of the study, the authors will approach five uncommon liver tumors - angiosarcoma, angiomyolipoma, cystadenoma/biliary carcinoma, epithelioid hemangioendothelioma, and fibrolamellar hepatocellular carcinoma -, describing their main characteristics and image findings with focus on computed tomography and magnetic resonance imaging.

Recent studies have demonstrated that the use of paramagnetic hepatobiliary contrast agents in the acquisition of magnetic resonance images remarkably improves the detection and differentiation of focal liver lesions, as compared with extracellular contrast agents. Paramagnetic hepatobiliary contrast agents initially show the perfusion of the lesions, as do extracellular agents, but delayed contrast-enhanced images can demonstrate contrast uptake by functional hepatocytes, providing further information for a better characterization of the lesions. Additionally, this intrinsic characteristic increases the accuracy in the detection of hepatocellular carcinomas and metastases, particularly the small-sized ones. Recently, a hepatobiliary contrast agent called gadolinium ethoxybenzyl dimeglumine, that is simply known as gadoxetic acid, was approved by the National Health Surveillance Agency for use in humans. The authors present a literature review and a practical approach of magnetic resonance imaging utilizing gadoxetic acid as contrast agent, based on patients' images acquired during their initial experiment.

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