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The aim of this study was to assess percentage respiratory changes (δ) in the size of pulmonary cysts of different smoking-related etiologies. Retrospectively, we measured the cystic lesions due to histopathological-confirmed honeycombing from interstitial pulmonary fibrosis, pulmonary Langerhans cell histiocytosis (PLCH), and paraseptal emphysema, using paired inspiratory and expiratory CT scans. In a sample of 72 patients and 216 lesions, the mean diameter of PLCH and honeycombing decreased during expiration (PLCH, δ = 60.9%; p = 0.001; honeycombing, δ = 47.5%; p = 0.014). Conversely, paraseptal emphysema did not show any changes (δ = 5.2%; p = 0.34). In summary, our results demonstrated that cysts in smokers with PLCH and honeycombing fibrosis get smaller during expiratory CT scans, whereas the size of cystic-like lesions due to paraseptal emphysema and bullae tend to remain constant during respiratory cycles. These results support the hypothesis of cyst-airway communication in some cystic diseases, which could assist in the differential diagnosis in smoking-related lung diseases., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Quantitative computed tomography (QCT) has recently gained an important role in the functional assessment of chronic lung disease. Its capacity in diagnostic, staging, and prognostic evaluation in this setting is similar to that of traditional pulmonary function testing. Furthermore, it can demonstrate lung injury before the alteration of pulmonary function test parameters, and it enables the classification of disease phenotypes, contributing to the customization of therapy and performance of comparative studies without the intra- and inter-observer variation that occurs with qualitative analysis. In this review, we address technical issues with QCT analysis and demonstrate the ability of this modality to answer clinical questions encountered in daily practice in the management of patients with chronic lung disease., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objective: To evaluate quantitative chest computed tomography (CT) methods for the detection of air trapping (AT) and to assess its diagnostic performance for the diagnosis of bronchiolitis obliterans syndrome (BOS) in single lung transplant (SLT) patients., Methods: Adult patients who had a SLT at a single transplant center and underwent CT scan after transplantation were retrospectively included. CT findings of air trapping were measured by three different methods: expiratory air-trapping index (ATIexp), mean lung density on expiratory acquisition (MLDexp) and expiratory to inspiratory ratio of mean lung density (E/I-ratio(MLD). Sensitivity, specificity and diagnostic accuracy of the three methods for the detection of BOS status evaluated by serial routine measures of pulmonary function tests (gold standard) were assessed., Results: Forty-six SLT patients (52.2% females, mean age 58 ± 6 years) were included in the analysis, 12 (26%) patients with a diagnosis of BOS. Quantitative CT diagnosis of AT ranged from 26 to 35%. Sensitivity, specificity and accuracy of each method for the detection of BOS were 85.7%, 84.7% and 85.0% for ATIexp, 78.5%, 93.4% and 90.0% for MLD and 64.2%, 89.1% and 83.3% E/I-ratio(MLD), respectively., Conclusion: Quantitative measures of AT obtained from standard CT are feasible and show high specificity and accuracy for the detection of BOS in SLT patients.

The lung acinus is the most distal portion of the airway responsible for the gas exchange. The normal acini are not visible on conventional computed tomography (CT), but the advent of micro-CT improved the understanding of the microarchitecture of healthy acini. The comprehension of the acinar architecture is pivotal for the understanding of CT findings of diseases that involve the acini. Centriacinar emphysema, for example, presents as round areas of low attenuation due to the destruction of the most central acini with compensatory enlargement of proximal acini due to alveolar wall destruction. In pulmonary fibrosis, intralobular septal fibrosis manifests as acinar wall thickening with an overlap of acinar collapse and compensatory dilation of surrounding acini constituting the cystic disease typical of the usual interstitial pneumonia pattern. This is a state-of-the-art review to describe the acinar structure from the micro-CT perspective and display how the comprehension of the acinar structure can aid in the interpretation of its microarchitecture disruption on conventional CT.

Quantitative imaging in lung cancer is a rapidly evolving modality in radiology that is changing clinical practice from a qualitative analysis of imaging features to a more dynamic, spatial, and phenotypical characterization of suspected lesions. Some quantitative parameters, such as the use of 18F-FDG PET/CT-derived standard uptake values (SUV), have already been incorporated into current practice as it provides important information for diagnosis, staging, and treatment response of patients with lung cancer. A growing body of evidence is emerging to support the use of quantitative parameters from other modalities. CT-derived volumetric assessment, CT and MRI lung perfusion scans, and diffusion-weighted MRI are some of the examples. Software-assisted technologies are the future of quantitative analyses in order to decrease intra- and inter-observer variability. In the era of "big data", widespread incorporation of radiomics (extracting quantitative information from medical images by converting them into minable high-dimensional data) will allow medical imaging to surpass its current status quo and provide more accurate histological correlations and prognostic value in lung cancer. This is a comprehensive review of some of the quantitative image methods and computer-aided systems to the diagnosis and follow-up of patients with lung cancer.

The original version of this article unfortunately contained a mistake. There is a typo in the coauthor name, it should be Stephan Altmayer.

Introduction: Our goal was to assess the diagnostic performance of magnetic resonance imaging (MRI) as a single method to diagnose pulmonary hypertension (PH) compared to right heart catheterization (RHC), computed tomography (CT), and ventilation/perfusion (V/Q) scintigraphy., Methods: We identified 35 patients diagnosed with PH by RHC in our institution who have also undergone a CT, a scintigraphy, and an MRI within a month. All cases were discussed in multidisciplinary meetings. We performed correlations between the MRI-derived hemodynamic parameters and those from RHC. The sensitivity and specificity of MRI were determined to identify its diagnostic performance to identify chronic thromboembolic pulmonary hypertension (CTEPH) and interstitial lung disease PH. The gold standard reference for the diagnosis of CTEPH and ILD was based on a review of multimodality imaging (V/Q scintigraphy and CT scan) and clinical findings., Results: Our results showed a good correlation between the hemodynamic parameters of cardiac MRI and RHC. Pulmonary vascular resistance had the best correlation between both methods (r = 0.923). The sensitivity and specificity of MRI to diagnose CTEPH was 100 and 96.8%, respectively. For the ILD-related PH, the MRI yielded a sensitivity of 60.0% and a specificity of 100%. Additionally, cardiac MRI was able to confirm all cases of PAH due to congenital heart disease initially detected by echocardiography., Conclusions: MRI represents a promising imaging modality as an initial, single-shot study, for patients with suspected PH with the advantages of being non-invasive and having no radiation exposure.

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.

Purposes: Considering that pulmonary arterial obstruction decreases venous flow, we hypothesized that filling defects in pulmonary veins can be identified in areas adjacent to pulmonary embolism (PE). This sign was named the "pulmonary vein sign" (PVS), and we evaluated its prevalence and performance for PE diagnosis in computed tomography pulmonary angiography (CTPA)., Methods: This retrospective study enrolled consecutive patients with clinical suspicion of PE who underwent CTPA scan. The PVS was defined by the following criteria: (a) presence of a homogeneous filling defect of at least 2 cm in a pulmonary vein; (b) attenuation of the left atrium > 160 Hounsfield units. Using the cases that presented PE on CTPA as reference, sensitivity, specificity, and positive and negative predictive values were calculated for PVS., Results: In total, 119 patients (73 female; mean age, 62 years) were included in this study. PE was diagnosed in 44 (35.8%) patients. The PVS was present in 16 out of 44 patients with PE. Sensitivity was 36.36% (95% confidence interval (CI) 22.83-52.26%); specificity, 98.67% (95% CI 91.79-99.93%); positive predictive value, 94.12% (95% CI 69.24-99.69%); negative predictive value, 72.55% (95% CI 62.67-80.70%). The Kappa index for the PVS was good (0.801; 95% CI 0.645-0.957). PVS was correlated with lobar and segmental pulmonary embolism (p < 0.01)., Conclusion: Despite a low sensitivity, presence of the pulmonary vein sign was highly specific for PE, with a good agreement between readers. This sign could contribute for PE diagnosis on CTPA studies.

Objective: To investigate bronchiectasis variations in different computed tomography (CT) respiratory phases, and their correlation with pulmonary function test (PFT) data, in adults., Methods: Retrospective data analysis from 63 patients with bronchiectasis according to CT criteria selected from the institution database and for whom PFT data were also available. Bronchiectasis diameter was measured on inspiratory and expiratory phases. Its area and matched airway-vessel ratios in both phases were also calculated. Finally, PFT results were compared with radiological measurements., Results: Bronchiectatic airways were larger on inspiration than on expiration (mean cross-sectional area, 69.44 vs. 40.84 mm 2 ; p < 0.05) as were airway-vessel ratios (2.1 vs. 1.4; p < 0.05). Cystic bronchiectasis cases showed the least variation in cross-sectional area (48%). Mean predicted values of forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were 81.5 and 77.2%, respectively, in the group in which bronchiectasis could not be identified on expiratory images, and 58.3 and 56.0%, respectively, in the other group (p < 0.05). Variation in bronchiectasis area was associated with poorer lung function (r = 0.32)., Conclusion: Bronchiectasis detection, diameter, and area varied significantly according to CT respiratory phase, with non-reducible bronchiectasis showing greater lung function impairment.

Objectives: We evaluated the diagnostic value for pulmonary embolism (PE) of the True fast imaging with steady-state precession (TrueFISP) MRI, a method that allows the visualization of pulmonary vasculature without breath holding or intravenous contrast., Methods: This is a prospective investigation including 93 patients with suspected PE. All patients underwent TrueFISP MRI after undergoing CT pulmonary angiography (CTPA). Two independent readers evaluated each MR study, and consensus was obtained. CTPA results were analysed by a third independent reviewer and these results served as the reference standard. A fourth radiologist was responsible for evaluating if lesions found on MRI for both analysis were the same and if these were the correspondent lesions on the CTPA. Sensitivity, specificity, predictive values and accuracy were calculated. Evidence for death from PE within the 1-year follow-up was also assessed., Results: Two patients could not undergo the real-time MRI and were excluded from the study. PE prevalence was 22%. During the 1-year follow-up period, eight patients died, whereas PE was responsible for 12.5% of cases. Between patients who developed PE, only 5% died due to this condition. There were no differences between MR and CT embolism detection in these subjects. MR sequences had a sensitivity of 85%, specificity was 98.6% and accuracy was 95.6%. Agreement between readers was high (κ= 0.87)., Conclusions: Compared with contrast-enhanced CT, unenhanced MR sequences demonstrate good accuracy and no differences in the mortality rates in 1 year were detected.

Histological examination has always been the gold standard for the detection and quantification of lung remodeling. However, this method has some limitations regarding the invasiveness of tissue acquisition. Quantitative imaging methods enable the acquisition of valuable information on lung structure and function without the removal of tissue from the body; thus, they are useful for disease identification and follow-up. This article reviews the various quantitative imaging modalities used currently for the non-invasive study of chronic obstructive pulmonary disease, asthma, and interstitial lung diseases. Some promising computer-aided diagnosis methods are also described.

Niemann-Pick disease is a rare autosomal recessive lysosomal storage disease with three subtypes. Types A and B result from a deficiency of acid sphingomyelinase activity, associated with the accumulation of lipid-laden macrophages (so-called Niemann-Pick cells) in various tissues, especially the liver and spleen. Type A is a fatal neurodegenerative disorder of infancy. Type B Niemann-Pick disease is a less severe form with milder neurological involvement, characterized by hepatosplenomegaly, hyperlipidemia, and pulmonary involvement; most patients live into adulthood. Type C Niemann-Pick disease is a complex lipid storage disorder caused by defects in cholesterol trafficking, resulting in a clinical presentation dominated by neurological involvement. Pulmonary involvement occurs in all three types of Niemann-Pick disease, but most frequently in type B. Respiratory manifestations range from a lack of symptoms to respiratory failure. Progression of respiratory disease is slow, but inexorable, due to the accumulation of Niemann-Pick cells in the alveolar septa, bronchial walls, and pleura, potentially leading to a progressively worsening restrictive pattern on pulmonary function testing. Bronchoalveolar lavage has important diagnostic value because it shows the presence of characteristic Niemann-Pick cells. Radiographic findings consist of a reticular or reticulonodular pattern and, eventually, honeycombing, involving mainly the lower lung zones. The most common changes identified by high-resolution computed tomography are ground-glass opacities, mild smooth interlobular septal thickening, and intralobular lines. The aim of this review is to describe the main clinical, imaging, and pathological aspects of Niemann-Pick disease, with a focus on pulmonary involvement.

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.

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.

A 58-year-old asymptomatic male smoker, underwent computed tomography of the chest for lung cancer screening. Unenhanced CT showed a hypodense elongated lesion with fat density within the superior vena cava (SVC). Magnetic resonance imaging was performed and confirmed the fatty nature of the lesion. Surgical resection of the lesion was performed and histopathological evaluation confirmed the diagnosis of SVC lipoma.

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.

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.

Patients with preexisting lung cavities are at risk of developing intracavitary fungal colonization. Because Aspergillus spp. are the most commonly implicated fungi, these fungal masses are called aspergillomas. Their characteristic "ball-in-hole" appearance, however, may be found in a variety of other conditions that can produce radiologic findings mimicking aspergilloma. In this paper, we review the main diseases that may mimic the radiographic findings of aspergilloma, with brief descriptions of clinical, radiologic, and histopathologic findings.

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.

Objective: The purpose of this study was to evaluate the clinical and radiological features of patients with fungal infection mimicking thoracic malignancy and to establish a diagnostic approach for both clinicians and radiologists to avoid misdiagnosis., Methods: In this retrospective study, we reviewed clinical and computed tomography (CT) findings from 27 patients who presented with suspicion of thoracic malignancy who were ultimately diagnosed with fungal disease., Results: Patients' median age was 55.7 (range 31-78) years. The most common clinical findings were cough (48.1 %), expectoration (33.3 %), chest pain (25.9 %), weakness (25.9 %), weight loss (18.5 %), and hemoptysis, dyspnea, and fever (7.4 % each). The median lesion size was 35.5 (range 10-85) mm. CT findings included a solid nodule (51.9 %), solid mass (37 %), or both (11.1 %). Nodule and mass margins were lobulated in 9 (33.3 %) patients, ill-defined in 5 (18.5 %), spiculated in 4 (14.8 %), and smooth in 4 (14.8 %) patients. Additional findings included consolidation in 4 (14.8 %) patients, cavitation in 3 (11.1 %), pleural effusion in 2 (7.4 %), and lymphadenopathy in 11 (40.7 %) patients. In all patients, specific diagnoses were made and confirmed by histopathology; final diagnoses were histoplasmosis (25.9 %), coccidiomycosis (22.2 %), cryptococcosis (22.2 %), aspergillosis (14.8 %), North American blastomycosis (7.4 %), mucormycosis (3.75 %), and paracoccidioidomycosis (3.75 %)., Conclusions: Fungal infection can present with clinical and radiological features that are indistinguishable from thoracic malignancy, such as lung nodules or masses. Because the management and outcomes of fungal infection and malignancy are entirely distinct, the establishment of a specific diagnosis is critical to provide appropriate therapy.

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.

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.

Leptospirosis, a spirochetal zoonosis, is frequently unrecognized due to its manifestation as an undifferentiated fever. It is an emerging infectious disease that has changed from an occupational disease of veterinarians, farmers, butchers, and other animal handlers to a cause of epidemics in poor and decayed urban communities in developing countries. Humans are infected when mucous membranes or abraded skin come into direct contact with the urine of infected animals, especially rats and dogs. Mortality from severe leptospirosis is high, even when optimal treatment is provided. The diagnosis of leptospirosis is based on clinical findings, history of direct or indirect exposure to infected animals in endemic areas, and positive serological tests. It should be considered in the differential diagnosis of patients with febrile illnesses associated with pneumonitis and respiratory failure, especially when hemoptysis is present. Severe pulmonary involvement in leptospirosis consists primarily of hemorrhagic pneumonitis. In advanced cases, adult respiratory distress syndrome and massive pulmonary hemorrhage may occur. Chest radiographs show bilateral alveolar infiltrates and/or resemble viral pneumonia, bronchopneumonia, tuberculosis, adult respiratory distress syndrome, and other causes of pulmonary hemorrhage such as Goodpasture syndrome. High-resolution computed tomography scans may show nodular infiltrates, areas of consolidation, ground-glass attenuation, and crazy-paving patterns. Bronchoalveolar lavage and autopsy studies have suggested that ground-glass opacities and air-space consolidations are secondary to pulmonary hemorrhage. Although not specific, the presence of these computed tomography findings in a febrile patient with an appropriate history should suggest a diagnosis of leptospirosis.