Paracoccidioidomycosis (PCM) is the most common systemic mycosis in Latin America. Although most cases occur in developing countries, recent immigration patterns and an increase in travel have led to a growing number of PCM cases in the United States and Europe. PCM is caused by the dimorphic fungus Paracoccidioides brasiliensis, and the chronic form may progress to severe pulmonary involvement. Several radiologic patterns have been described for pulmonary PCM, including linear and reticular opacities, variable-sized nodules, patchy ill-defined opacities, airspace consolidation, and cavitary lesions. Fibrosis and paracicatricial emphysema are common associated findings. Chest computed tomography (CT) is the method of choice for evaluating pulmonary PCM, with the most common CT findings being ground-glass attenuation, consolidation, small or large nodules, masses, cavitations, interlobular septal thickening, emphysema, and fibrotic lesions. PCM is also an important cause of the "reversed halo" sign at high-resolution CT and should be considered in the differential diagnosis. Awareness of the multiple radiologic manifestations of PCM as well as its epidemiologic and clinical characteristics may permit early diagnosis and initiation of specific treatment, thereby reducing associated morbidity and mortality.

Cirrhosis is characterized by a spectrum of hepatocellular nodules that mark the progression from regenerative nodules to low- and high-grade dysplastic nodules, followed by small and large hepatocellular carcinomas (HCCs). Characterization of small nodules on the basis of imaging and histopathologic findings is complicated by an overlap in findings associated with each type of nodule, a reflection of their multistep transitions. Vascularity patterns change gradually as the nodules evolve, with an increasing shift from predominantly venous to predominantly arterial perfusion. Regenerative and low-grade dysplastic nodules demonstrate predominantly portal perfusion and contrast enhancement similar to that of surrounding parenchyma. Differentiation of high-grade dysplastic nodules and well-differentiated HCCs on the basis of dynamic imaging and histologic findings is challenging, with a high rate of false-negative results. Some small nodules that lack hypervascularity may be early HCCs. Progressed small and large HCCs usually present no diagnostic difficulty because of their characteristic findings. Although characterization of hypervascular lesions in the cirrhotic liver is difficult, it is a key step in disease management and is the radiologist's responsibility.

OBJECTIVE: To describe aspects found on HRCT scans of the chest in patients infected with the influenza A (H1N1) virus. METHODS: We retrospectively analyzed the HRCT scans of 71 patients (38 females and 33 males) with H1N1 infection, confirmed through laboratory tests, between July and September of 2009. The HRCT scans were interpreted by two thoracic radiologists independently, and in case of disagreement, the decisions were made by consensus. RESULTS: The most common HRCT findings were ground-glass opacities (85%), consolidation (64%), or a combination of ground-glass opacities and consolidation (58%). Other findings were airspace nodules (25%), bronchial wall thickening (25%), interlobular septal thickening (21%), crazy-paving pattern (15%), perilobular pattern (3%), and air trapping (3%). The findings were frequently bilateral (89%), with a random distribution (68%). Pleural effusion, when observed, was typically minimal. No lymphadenopathy was identified. CONCLUSIONS: The most common findings were ground-glass opacities and consolidations, or a combination of both. Involvement was commonly bilateral with no axial or craniocaudal predominance in the distribution. Although the major tomographic findings in H1N1 infection are nonspecific, it is important to recognize such findings in order to include infection with the H1N1 virus in the differential diagnosis of respiratory symptoms.

The present study aimed to review high resolution computed tomography findings in patients with H1N1 influenza A infection. The most common tomographic findings include ground-glass opacities, areas of consolidation or a combination of both patterns. Some patients may also present bronchial wall thickening, airspace nodules, crazy-paving pattern, perilobular opacity, air trapping and findings related to organizing pneumonia. These abnormalities are frequently bilateral, with subpleural distribution. Despite their nonspecificity, it is important to recognize the main tomographic findings in patients affected by H1N1 virus in order to include this possibility in the differential diagnosis, characterize complications and contribute in the follow-up, particularly in cases of severe disease.

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