Infectious and Non-Infectious Diseases Causing the Air Crescent Sign: A State-of-the-Art Review.

Aspergilloma, also known as mycetoma or fungus ball, is characterized by a round or oval mass with soft-tissue attenuation within a preexisting lung cavity. The typical computed tomography (CT) aspect of an aspergilloma is a mass separated from the wall of the cavity by an airspace of variable size and shape, resulting in the air crescent sign, also known as the meniscus sign. This CT feature is non-specific and can be simulated by several other entities that result in intracavitary masses. This review describes the main clinical and imaging aspects of the infectious and non-infectious diseases that may present with fungus-ball appearance, including pulmonary hydatid cyst, Rasmussen aneurysm, pulmonary gangrene, intracavitary clot, textiloma, lung cancer, metastasis, and teratoma, focusing on the differential diagnosis.

Dengue Hemorrhagic Fever: A State-of-the-Art Review Focused in Pulmonary Involvement.

Dengue fever is an arboviral disease transmitted to humans through the bites of infected female Aedes mosquitoes. Dengue virus is a member of the Flaviviridae family, and human infection can be caused by any of the four antigenically distinct serotypes (DENV 1-4). The infection has become recognized as the most important and prevalent arboviral disease in humans, endemic in almost 100 countries worldwide. Nearly 3 billion people live in areas with transmission risk. Autochthonous transmission of the virus in previously disease-free areas, increased incidence in endemic areas, and epidemic resurgence in controlled regions could increase the risk of contracting more severe forms of the disease, such as dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS). Symptomatic dengue virus infection can present with a wide range of clinical manifestations, from mild fever to life-threatening DSS. Thoracic complications may manifest as pleural effusion, pneumonitis, non-cardiogenic pulmonary edema, and hemorrhage/hemoptysis. No vaccine is currently available and no specific treatment for dengue fever exists, but prevention and prompt management of complications in patients with DHF can help reduce mortality. This review describes the main clinical, pathological, and imaging findings of thoracic involvement in DHF.

Pulmonary Leptospirosis With Diffuse Alveolar Hemorrhage: High-Resolution Computed Tomographic Findings in 16 Patients.

OBJECTIVE: The aim of this study was to evaluate the high-resolution computed tomographic (HRCT) findings from patients with leptospirosis and diffuse alveolar hemorrhage (DAH). MATERIALS AND METHODS: We retrospectively reviewed HRCT findings from 16 patients diagnosed as having leptospirosis causing DAH. The patient sample was composed of 13 men and 3 women aged 22 to 53 years (mean age, 34.5 years). Diagnosis was established with confirmation of leptospirosis infection by serologic microagglutination test. Histopathological study was performed in 8 patients. Two chest radiologists analyzed the HRCT images and reached decisions by consensus. RESULTS: The predominant HRCT findings were ground-glass opacities and airspace nodules (both n = 12, 75%), ground-glass nodules (n = 9, 56.25%), consolidations (n = 7, 43.75%), "crazy-paving" pattern (n = 3, 18.75%), and interlobular septal thickening without ground-glass opacity (n = 3, 18.75%). Bilateral pleural effusion was an associated finding in 2 (12.5%) patients. Analysis of the axial distribution of the lesions revealed diffuse distribution in 11 (68.75%) patients and peripheral lung zone predominance in 5 (31.25%) patients. Abnormalities were bilateral in all 16 (100%) patients. Analysis of the craniocaudal distribution of the lesions revealed lower zone predominance in 9 (56.25%) patients, diffuse distribution in 5 (31.25%) patients, middle zone predominance in 1 (6.25%) patient, and upper zone predominance in 1 (6.25%) patient. CONCLUSIONS: The most frequent HRCT findings in patients with leptospirosis causing DAH were ground-glass opacities, airspace nodules, ground-glass nodules, and consolidations. The lesions showed symmetrical distribution with lower zone predominance in most cases.

Applications of Magnetic Resonance Imaging of the Thorax in Pleural Diseases: A State-of-the-Art Review.

The aim of this review was to present the main aspects of pleural diseases seen with conventional and advanced magnetic resonance imaging (MRI) techniques. This modality is considered to be the gold standard for the evaluation of the pleural interface, characterization of complex pleural effusion, and identification of exudate and hemorrhage, as well as in the analysis of superior sulcus tumors, as it enables more accurate staging. The indication for MRI of the thorax in the identification of these conditions is increasing in comparison to computerized tomography, and it can also be used to support the diagnosis of pulmonary illnesses. This literature review describes the morphological and functional aspects of the main benign and malignant pleural diseases assessed with MRI, including mesothelioma, metastasis, lymphoma, fibroma, lipoma, endometriosis, asbestos-related pleural disease, empyema, textiloma, and splenosis.

An unusual cause of tree-in-bud pattern: pulmonary intravascular tumor embolism caused by chondrosarcoma.

We report the case of a 45-year-old man who initially presented with chondrosarcoma of the left femur that was treated surgically. Follow-up chest computed tomography (CT) performed 3 years later showed multiple small nodules with a tree-in-bud branching pattern and larger elongated opacities with beaded contours. These findings raised the suspicion of intravascular tumor embolism. Pulmonary CT angiography demonstrated intravascular thrombosis and dilated and beaded peripheral pulmonary arteries. The tumoral origin of the thrombus was confirmed by lung biopsy.

Respiratory Tract Amyloidosis. State-of-the-Art Review with a Focus on Pulmonary Involvement.

Amyloidosis is a constellation of disease entities characterized by abnormal extracellular deposition and accumulation of protein and protein derivatives, which show apple-green birefringence when stained with Congo red and viewed under polarized light. Amyloid can infiltrate virtually all organ systems and can display multiple and diverse imaging findings. Pathologically, respiratory involvement occurs in 50 % of patients with amyloidosis, and its clinical signs and symptoms vary depending on whether the disease is systemic or localized. The four main patterns of respiratory tract involvement are tracheobronchial, nodular parenchymal, diffuse alveolar septal, and lymphatic. Imaging findings of amyloidosis are nonspecific and vary in each pattern; knowledge about the disease impairment type is thus very important, and amyloidosis should be considered in the differential diagnosis of other very common diseases, such as infectious diseases, neoplasms, and vasculitis. This literature review describes the main clinical and imaging manifestations of amyloidosis, focusing on respiratory tract involvement and differential diagnosis.

Tuberous Sclerosis Complex: State-of-the-Art Review with a Focus on Pulmonary Involvement.

Tuberous sclerosis complex (TSC) is an autosomal-dominant neurocutaneous disease with high phenotypic variability. The incidence is approximately one in 5000-10,000 births. TSC is characterized by widespread hamartomas and benign or rarely malignant neoplasms affecting various organs, most commonly the brain, skin, retinas, kidneys, heart, and lungs. The wide range of organs affected reflects the roles of TSC1 and TSC2 genes in the regulation of cell proliferation and differentiation. Clinical diagnostic criteria are important because genetic testing does not identify the mutation in up to 25% of patients. Imaging is pivotal, as it allows a presumptive diagnosis of TSC and definition of the extent of the disease. Common manifestations of TSC include cortical tubers, subependymal nodules, white matter abnormalities, retinal abnormalities, cardiac rhabdomyoma, lymphangioleiomyomatosis (LAM), renal angiomyolipoma, and skin lesions. Pulmonary involvement consists of LAM and, less commonly, multifocal micronodular pneumocyte hyperplasia (MMPH), which causes cystic and nodular diseases, respectively. Recent reports indicate that pulmonary LAM is found by computed tomography in up to 35% of the female patients with TSC. MMPH is rare and may be associated with LAM or, less frequently, occurs as an isolated pulmonary manifestation in women with TSC. Dyspnea and pneumothorax are common clinical presentations of LAM, whereas MMPH is usually asymptomatic. The aim of this review is to describe the main clinical, imaging, and pathological aspects of TSC, with a focus on pulmonary involvement.

CT quantification of large opacities and emphysema in silicosis: correlations among clinical, functional, and radiological parameters.

BACKGROUND: The assessment of the extent of silicosis on chest radiographs is subjective and could be more standardized by using computed tomography (CT) quantification methods. We propose a semiautomatic method of quantifying the anatomical lung damage (LD) (the sum of the emphysema and large opacities volumes) measured by CT densitovolumetry in complicated silicosis. METHODS: Twenty-three nonsmokers with complicated silicosis were included. Large opacities were recorded as size A, B, or C according to the size of the opacities on chest radiographs. Pulmonary function tests (PFT) were assessed by spirometry and the carbon monoxide diffusion capacity. Total lung capacity (TLC) was measured by helium dilution, and total lung volume (TLV) was measured by CT quantification (TLVct). CT images were postprocessed using CT densitovolumetry to measure the TLVct, large opacities volume, emphysema volume (EV), and emphysema index (EI). RESULTS: Significant correlations were observed between the EV and the forced vital capacity (r = 0.41, p = 0.04), TLC (r = 0.44, p = 0.03), and residual volume (RV) (r = 0.49, p = 0.01). A correlation also was observed between the LD% and RV (r = 0.43, p = 0.03) and between the LD and RV (r = 0.47, p = 0.02). CONCLUSIONS: The PFT findings were correlated with the EV, EI, LD, and LD%, but they were not correlated with the large opacities volume. These results suggest that the emphysema volume, more than the large opacities volume, is responsible for functional impairment in patients with complicated silicosis.

High-resolution computed tomographic findings of cocaine-induced pulmonary disease: a state of the art review.

Cocaine is the most commonly used illicit drug among patients presenting at hospital emergency departments and the most frequent cause of drug-related deaths reported by medical examiners. Various respiratory problems temporally associated with cocaine use have been reported. Acute and chronic uses also are responsible for lung complications, such as pulmonary edema, alveolar hemorrhage, pulmonary hypertension, organizing pneumonia, emphysema, barotrauma, infection, cancer, eosinophilic disease, and aspiration pneumonia. Although most imaging findings are nonspecific, they may raise suspicion of a cocaine-related etiology when considered together with patients' profiles and medical histories. This literature review describes cocaine-induced diseases with pulmonary involvement, with an emphasis on high-resolution chest computed tomographic findings and patterns.

Infectious diseases causing diffuse alveolar hemorrhage in immunocompetent patients: a state-of-the-art review.

Diffuse alveolar hemorrhage (DAH) represents a syndrome that can complicate many clinical conditions and may be life-threatening, requiring prompt treatment. It is recognized by the signs of acute- or subacute-onset cough, hemoptysis, diffuse radiographic pulmonary infiltrates, anemia, and hypoxemic respiratory distress. DAH is characterized by the accumulation of intra-alveolar red blood cells originating most frequently from the alveolar capillaries. It must be distinguished from localized pulmonary hemorrhage, which is most commonly due to chronic bronchitis, bronchiectasis, tumor, or localized infection. Hemoptysis, the major sign of DAH, may develop suddenly or over a period of days to weeks; this sign may also be initially absent, in which case diagnostic suspicion is established after sequential bronchoalveolar lavage reveals worsening red blood cell counts. The causes of DAH can be divided into infectious and noninfectious, the latter of which may affect immunocompetent or immunodeficient patients. Pulmonary infections are rarely reported in association with DAH, but they should be considered in the diagnostic workup because of the obvious therapeutic implications. In immunocompromised patients, the main infectious diseases that cause DAH are cytomegalovirus, adenovirus, invasive aspergillosis, Mycoplasma, Legionella, and Strongyloides. In immunocompetent patients, the infectious diseases that most frequently cause DAH are influenza A (H1N1), dengue, leptospirosis, malaria, and Staphylococcus aureus infection. Based on a search of the PubMed and Scopus databases, we review the infectious diseases that may cause DAH in immunocompetent patients.

Computed tomography findings of pulmonary histoplasmosis: pictorial essay.

Endemic systemic mycoses are prevalent in specific geographic areas of the world and are responsible for high rates of morbidity and mortality in the populations of such areas, as well as in immigrants and travelers returning from endemic regions. Pulmonary histoplasmosis is an infection caused by Histoplasma capsulatum, a dimorphic fungus. This infection has a worldwide distribution, being endemic in Brazil. Histoplasmosis can affect the lungs, and its diagnosis and management remain challenging, especially in non-endemic areas. Therefore, recognition of the various radiological manifestations of pulmonary histoplasmosis, together with the clinical and epidemiological history of the patient, is essential to narrowing the differential diagnosis. This essay discusses the main computed tomography findings of pulmonary histoplasmosis.

As micoses sistêmicas endêmicas são prevalentes em áreas geográficas específicas do mundo e são responsáveis por altas taxas de morbidade e mortalidade nessas populações e em imigrantes e viajantes que retornam de regiões endêmicas. A histoplasmose pulmonar é uma infecção causada pelo Histoplasma capsulatum, um fungo dimórfico. Essa infecção tem distribuição mundial, apresentando-se de forma endêmica no Brasil. A histoplasmose pode afetar os pulmões de pacientes, e seu diagnóstico e manejo permanecem desafiadores, especialmente em áreas não endêmicas. Portanto, o reconhecimento das várias manifestações radiológicas da histoplasmose pulmonar associadas a história clínica e epidemiológica dos pacientes é fundamental para estreitar o diagnóstico diferencial. Este ensaio discute os principais achados tomográficos da histoplasmose pulmonar.

Computed tomography aspects of thoracic metastases from osteosarcoma: pictorial essay.

Osteosarcoma is the most common primary bone tumor, with a higher incidence in the second decade of life, and it often leads to pulmonary metastases. The most common pattern seen on computed tomography is one of multiple well-defined nodules in the lung parenchyma, often with calcifications. Because of the variety of presentations of pulmonary metastases in osteosarcoma, including atypical forms, knowledge of the computed tomography aspects of these lesions is important for characterizing and evaluating the extent of the disease, as well as for distinguishing metastatic disease from other benign or malignant lung diseases. This essay discusses the main tomographic findings of pulmonary metastases from osteosarcoma.

O osteossarcoma é o tumor ósseo primário mais comum, com maior incidência na segunda década de vida, sendo as metástases pulmonares achado frequente. O padrão tomográfico mais comum das metástases pulmonares de osteossarcoma é o de múltiplos nódulos bem definidos no parênquima pulmonar, frequentemente com calcificações. Em razão da multiplicidade de apresentações das metástases pulmonares do osteossarcoma, inclusive com formas atípicas, o conhecimento dos aspectos dessas lesões na tomografia computadorizada do tórax é importante para a caracterização e avaliação da extensão da doença, além de permitir a diferenciação entre doença metastática e outras doenças pulmonares benignas ou malignas. Este ensaio discute os principais achados tomográficos das metástases pulmonares de osteossarcoma.

Thoracic paracoccidioidomycosis: radiographic and CT findings.

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.

Reversed halo sign on computed tomography: state-of-the-art review.

The reversed halo sign (RHS) is a chest computed tomography (CT) pattern defined as a focal round area of ground-glass attenuation surrounded by a crescent or ring of consolidation. The RHS was first described as being relatively specific for cryptogenic organizing pneumonia but was later observed in several other infectious and noninfectious diseases. Although the presence of the RHS on CT may help narrow the range of diseases considered in differential diagnoses, final diagnoses should be based on correlation with the clinical scenario and the presence of additional disease-specific CT findings. However, frequently a biopsy may be needed to establish the diagnosis. Organizing pneumonia is the most frequent cause of the RHS. This is a distinct clinical and pathologic entity that can be cryptogenic or secondary to other known causes. Morphologic aspects of the halo, particularly the presence of small nodules in the wall or inside the lesion, usually indicate an active granulomatous disease (tuberculosis or sarcoidosis) rather than organizing pneumonia. Immunocompromised patients presenting with the RHS on CT examination should be considered to have an infection until further analyses prove otherwise. Pulmonary zygomycosis and invasive pulmonary aspergillosis are typically seen in patients with severe immunosuppression, most commonly secondary to hematological malignancies. Other causes of the RHS include noninvasive fungal infections such as paracoccidioidomycosis, histoplasmosis, and Pneumocystis jiroveci pneumonia. Furthermore, Wegener's granulomatosis, radiofrequency ablation, and lymphomatoid granulomatosis may also lead to this finding. Based on a search of the PubMed and Scopus databases, we review the different diseases that can manifest with the RHS on CT.

Concomitant COVID-19 and pulmonary tuberculosis: computed tomography aspects.

OBJECTIVE: To describe the relationship between coronavirus disease 2019 (COVID-19) and pulmonary tuberculosis during the current pandemic, as well as to describe the main computed tomography (CT) findings in patients suffering from both diseases simultaneously. MATERIALS AND METHODS: This was a retrospective, cross-sectional observational study of the chest CT scans of 360 patients with COVID-19, as confirmed by RT-PCR. RESULTS: In four (1.1%) of the patients, changes suggestive of COVID-19 and tuberculosis were observed on the initial CT scan of the chest. On chest CT scans performed for the follow-up of COVID-19, cavitary lesions with bronchogenic spread were observed in two of the four patients, whereas alterations consistent with the progression of fibrous scarring related to previous tuberculosis were observed in the two other patients. The diagnosis of tuberculosis was confirmed by the isolation of Mycobacterium tuberculosis. CONCLUSION: Albeit rare, concomitant COVID-19 and tuberculosis can be suggested on the basis of the CT aspects. Radiologists should be aware of this possibility, because initial studies indicate that mortality rates are higher in patients suffering from both diseases simultaneously.

OBJETIVO: Descrever a associação entre COVID-19 e tuberculose pulmonar durante a pandemia atual e descrever os principais achados tomográficos. MATERIAIS E MÉTODOS: Estudo retrospectivo transversal e observacional de tomografias computadorizadas de tórax realizadas em 360 pacientes com COVID-19 confirmada por RT-PCR. RESULTADOS: Em quatro pacientes (1,1%) foram encontradas alterações tomográficas sugestivas de associação entre COVID-19 e tuberculose. Em dois pacientes observaram-se escavações com disseminação broncogênica e em outros dois, alterações compatíveis com progressão de lesões fibrocicatriciais relacionadas a tuberculose prévia, em exames de controle para COVID-19. O diagnóstico foi confirmado pelo isolamento do Mycobacterium tuberculosis. CONCLUSÃO: Apesar de incomum, a associação entre COVID-19 e tuberculose pode ser sugerida com base em aspectos tomográficos, devendo os radiologistas estar atentos a esta possibilidade, pois estudos iniciais indicam aumento da mortalidade nesses pacientes.

Reversed halo sign in active pulmonary tuberculosis: criteria for differentiation from cryptogenic organizing pneumonia.

OBJECTIVE: The purpose of this study was to compare the morphologic characteristics of the "reversed halo" sign caused by tuberculosis with those caused by cryptogenic organizing pneumonia (COP) and to determine whether high-resolution CT (HRCT) can differentiate between these two conditions. MATERIALS AND METHODS: We retrospectively reviewed the HRCT scans of patients with the reversed halo sign caused by active tuberculosis and HRCT scans of patients with the reversed halo sign caused by COP. The study included 12 patients with active pulmonary tuberculosis (10 women and two men) and 10 patients with biopsy-proven COP (five women and five men). Tuberculosis was diagnosed by culture of sputum, bronchoalveolar lavage, or biopsy specimen. All patients underwent HRCT, and the images were reviewed by two chest radiologists who reached decisions by consensus. RESULTS: HRCT scans of all patients with active tuberculosis showed reversed halos with nodular walls; in most cases (10/12), we also observed nodules inside the halos. None of the HRCT scans of the COP cases reviewed had halos with nodular walls or nodules inside them. We also observed parenchymal abnormalities, such as consolidation, ground-glass, and linear opacities, associated with the reversed halo sign. Neither the number of reversed halo sign lesions nor the associated parenchymal lesions discriminated between tuberculosis and COP. Nevertheless, the association of the reversed halo sign with nodular walls or nodules inside the halo was seen only in tuberculosis patients. CONCLUSION: Although COP is considered the most frequent cause of the reversed halo sign, the presence of nodular walls or nodules inside the reversed halo strongly favors a diagnosis of active pulmonary tuberculosis rather than COP.

The reversed halo sign on high-resolution CT in infectious and noninfectious pulmonary diseases.

OBJECTIVE: The purpose of this article is to describe diseases that may present with the reversed halo sign on high-resolution CT. We emphasize the tomographic features most frequently associated with this sign and correlate them with histologic findings. CONCLUSION: A wide spectrum of infectious and noninfectious diseases may present with the reversed halo sign on chest CT. The nonspecific nature of this sign should not cloud an otherwise fairly straightforward diagnosis, especially when associated background findings are typical. Although a rigorous analysis of associated CT findings may help with the differential diagnosis, histologic assessment is often needed for a definitive determination of the cause.

Swine-origin influenza A (H1N1) viral infection: thoracic findings on CT.

OBJECTIVE: The purpose of this article is to illustrate and describe various CT manifestations of swine-origin influenza A (H1N1) viral infection. CONCLUSION: The imaging findings seen in patients with H1N1 infection include consolidations, ground-glass opacities, interlobular septal thickening, small nodules, and findings suggestive of small airways disease, among others. Definitive diagnosis is based on correlation of the CT findings with the clinical symptoms and laboratory test results.