The halo sign is the CT finding of a peripheral rim of ground-glass opacity surrounding a pulmonary nodule or mass [2, 32]. Classically associated with right upper lobe consolidation due to Klebsiella pneumoniae (Fig. [3**] Plain chest radiography is an inexpensive test and is an important initial examination in all patients suspected of pneumonia. The meniscus, Cumbo, and water lily signs are all seen with pulmonary echinococcal infection [74–78]. The split-pleura sign is not specific for empyema but rather indicates the presence of an exudative effusion [31]. [8] Respir. Air-fluid level in endocyst (arrowhead) in combination with meniscus sign forms Cumbo sign. Imaging features that favor mucormycosis over Aspergillus infection in a neutropenic patient are detection of the reverse halo or bird's nest sign, multiplicity of pulmonary nodules (> 10), and development of infection despite voriconazole prophylaxis [66–68]. Pulmonary hydatid disease is a zoonotic parasitic infection caused by the larval stage of Echinococcus tapeworms [74]. A lung abscess with an air-fluid level can be differentiated from empyema with bronchopleural fistula by measurement and comparison of the lengths of the visualized air-fluid level on orthogonal chest radiographs. 8). 15), probably because of the presence of calcium salts, metals, and desiccated mucus [47–50]. Diagnostic tests including radiologic studies and blood or serologic tests that could help establish the cause of pneumonia would reduce the use of antibiotics and may improve the clinical course. Posteroanterior radiograph shows large right lower lobe thick-walled cavity with lobulated air–soft-tissue interface representing floating endocyst (arrow). Imaging signs of lung abscess, such the an air-fluid level sign in a cavity, may also be predictive of prognosis and guide duration of therapy. Detection of the air bronchogram sign argues against the presence of a central obstructing lesion. • Identify the most common features of pulmonary viral infections at thin-section CT. 3. 2). Mycetomas can cause hemoptysis. This sign is seen in two types of Aspergillus infection: angioinvasive and mycetoma [40]. The radiological findings of CMV infection are variable consisting of lobar consolidation, diffuse and focal parenchymal haziness, and multiple small nodules with associated areas of ground-glass attenuation (“halo”) (fig. Axial supine (left) and prone (right) CT images show gravity dependence of fungal ball (mycetoma). After finding mates, the parasites burrow through the visceral pleura into the lung parenchyma, where they produce cysts that contain eggs. Posteroanterior radiographs show normal interface (right) and loss of normal interface of lung and left-heart border (left), thus localizing abnormality to lingula. The crazy-paving sign was originally described as a characteristic CT pattern detected in patients with pulmonary alveolar proteinosis. Thick, irregular wall typical of lung abscess is evident. 19 —55-year-old man with chronic coccidioidomycosis infection. 18 —CT scans show crazy-paving sign in patients with various disorders. For example, lingular pneumonia obscures the left-heart border, and middle lobe pneumonia obscures the right-heart border, because the areas of consolidation and the respective heart borders are in the same anatomic plane (Fig. Posteroanterior radiograph (top left) and corresponding coronal (top right) and axial (bottom) CT images show branching tubular opacity (arrows) in right upper lobe. Posteroanterior radiograph shows thin-walled grape-skin cyst (arrows). A, Posteroanterior radiograph shows branching tubular opacities (arrows) emanating from both hila. Example of reverse halo and bird's nest signs. They produce similar imaging findings in the thorax [79–83]. Other diseases that can manifest the silhouette sign include atelectasis (segmental or lobar), aspiration, pleural effusion, and tumor [ … Axial CT image shows diffuse ground-glass opacity with areas of superimposed interlobular septal thickening (combination that forms crazy-paving pattern) and multiple thin-walled cysts. Common radiological features of pneumonia 1. This patient has had positive RT-PCR testing for 2019-nCoV before CT, so CT findings are consistent with COVID-19 pneumonia CO-RADS 6. Axial (left) and sagittal (right) contrast-enhanced CT images show thickening of visceral (arrowheads) and parietal (arrows) pleura with associated effusion. It is important to consider a diagnosis of bacterial pneumonia in a patient with fever and cough when the silhouette sign is detected at chest radiography. Example of air-fluid level sign. This review is divided into signs that are most commonly seen or associated with bacterial, viral, fungal, and parasitic infections. By contrast, empyema typically forms obtuse angles along its interface with adjacent pleura and usually has smooth, thin, enhancing walls [28, 29]. It is due to material, usually purulent, filling the alveoli. Consolidation is one of the more common manifestations of pulmonary infection, and its appearance is variable, dependent on the causative organism. Because tree-in-bud opacities form in the center of the secondary pulmonary lobule, they characteristically spare the subpleural lung parenchyma, including that adjacent to interlobar fissures. Fig. Fig. 3). Centrilobular nodules are evenly spaced and do not come into contact with adjacent pleural surfaces. Fig. This study aimed to compare the clinical and radiological characteristics of SARS-CoV-2 and endemic HCoVs infection in adult hospitalized patients with community-acquired pneumonia (CAP). The sign has come to be recognized, however, as occurring in many other conditions, including infection (e.g., Pneumocystis jiroveci pneumonia, influenza, and infections by other organisms) [51, 52]. Humans serve as a definitive host when they ingest raw or improperly cooked crab or crayfish [76]. Pneumocystis pneumonia. Those with a more chronic course include pulmonary alveolar proteinosis, pulmonary adenocarcinoma, and lipoid pneumonia [52, 55]. The air sacs may fill with fluid or pus (purulent material), causing cough with phlegm or pus, fever, chills, and difficulty breathing. It can also cause a white-out of the hemithorax (see Chapter 9). Air Bronchogram Sign Branching, linear, tubular lucency representing a bronchus or bronchiole passing through airless lung parenchyma. These signs are caused by air dissecting between the cyst layers, which are initially indistinguishable on CT images because the cysts are fluid filled (Fig. 23 —49-year-old man with pulmonary hydatid disease. 3 —45-year-old man with reactivation tuberculosis. 2). The nodules usually have basal and peripheral predominance and vary in size [24]. A cavity is defined as abnormal lucency within an area of consolidation with or without an associated air-fluid level. B, Axial CT image shows parenchymal location of right lower lobe cavity with air-fluid level, irregular internal contours, and associated bronchus (arrow) coursing to lesion. The ground-glass opacity represents hemorrhage surrounding infarcted lung and is caused by vascular invasion by the fungus [35]. The grape-skin sign is the radiographic or CT finding of a very thin-walled cavitary lesion that develops in lung parenchyma previously affected by consolidation or lung granulomas that have undergone central caseous necrosis [56]. Example of air bronchogram sign. In a patient with pneumonia, detection of an air-fluid level on chest radiographs or CT images suggests the presence of a lung abscess or empyema with bronchopleural fistula. Less commonly, the tree-in-bud sign may be a manifestation of vascular lesions (so-called vascular tree-in-bud), including embolized tumor or foreign material, due to the anatomic location of small arterioles as paired homologous structures that course alongside the small airways in the centrilobular aspect of the secondary pulmonary lobules [8, 12–15] (Fig. Fig. This study was performed at a university-affiliated tertiary hospital in the Republic of Korea, between January 1, 2015, and July 31, 2020. J. The air crescent sign is not specific for Aspergillus infection and can be seen in other conditions, such as cavitating neoplasm, intracavitary clot, and Wegener granulomatosis [2, 43, 44]. Although chest radiographs are still useful as an initial test, their utility is limited in the diagnosis of lu … The tubular opacities represent dilated bronchi impacted with mucus. It is due to material, usually purulent, filling the alveoli. As classically described, the grape-skin sign is a solitary finding of a thin-walled cavity with central lucency that has been associated with chronic pulmonary coccidioidomycosis infection [57, 58] (Fig. Fig. Fig. Pneumonia is a general term in widespread use, defined as infection within the lung. 14 —65-year-old woman with intracavitary mycetoma. With bronchial erosion, air dissects between the outer pericyst and ectocyst to produce the meniscus sign (Fig. Fig. In very severe cases, COVID-19 pneumonia can lead to acute respiratory distress syndrome (ARDS), a … OBJECTIVE. Patients occasionally present with pneumothorax [79–83]. A, Posteroanterior (left) and lateral (right) radiographs show right lower lobe cavity with air-fluid level (arrows) of equal length on both orthogonal views. B-lines, confluent B-lines or small areas of sub-pleural consolidations suggest viral pneumonias [101,102]. Fig. Consolidation seen in a non-lobar distribution should raise the suspicion of atypical organisms; This patient with known HIV infection has subtle consolidation in the mid zones bilaterally Cavitation can have noninfectious causes, including malignancy, radiation therapy, and lung infarction [2]. Fig. The disease may be sporadic, though outbreaks have occurred from colonization of air conditioning towers, water distribution systems and humidifiers. Axial contrast-enhanced CT image shows heterogeneously enhancing right lower lobe consolidation (arrows) suspicious for early pulmonary necrosis. According to the Centers for Disease Control and Prevention, influenza and pneumonia were combined as the eighth leading cause of death in the United States in 2011 [1]. The chest CT findings reflect the life cycle of the parasite. Tree-in-bud opacities usually indicate infectious bronchiolitis or aspiration but are less commonly seen in other conditions, such as follicular bronchiolitis, chronic airways inflammation (e.g., cystic fibrosis or immune deficiency), diffuse panbronchiolitis, and adenocarcinoma [11]. 23). Axial CT image (bottom) shows numerous V- and Y-shaped tree-in-bud opacities. Suppurative necrosis usually occurs with infection by Staphylococcus aureus, gram-negative bacteria, or anaerobes. Differential diagnostic considerations for the crazy-paving sign can be categorized according to the typical time course of the suspected diseases (Fig. Proximal portion of branching opacity was FDG avid (not shown) and represented tumor, whereas rest of opacity represented mucoid impaction in dilated bronchus. The bulging fissure sign is also less commonly detected in patients with hospital-acquired Klebsiella pneumonia than in those with community-acquired Klebsiella infection [19]. DD: Pneumonia lymphoma bronchoalveolar cell carcinoma. These signs are suggestive of invasive fungal infection (e.g., angioinvasive Aspergillus infection or mucormycosis) in susceptible patient populations [66]. Eur. The purposes of this article are to describe common and uncommon imaging signs and patterns of pulmonary infections and to discuss their underlying anatomic and pathophysiologic basis. (Courtesy of Chou S, University of Washington, Seattle, WA). The tubular opacities that occur in ABPA result from hyphal masses and mucoid impaction and typically affect the upper lobes. Noninfectious causes of the miliary pattern include metastatic disease, IV injected foreign material, and rarely sarcoidosis [62, 63]. This sign is commonly applied to the interface between the lungs and the heart, mediastinum, chest wall, and diaphragm. Opacities in ABPA are composed of hyphal masses, and mucoid impaction and may be calcified on CT images in as many as 28% of cases. The linear track represents the path followed by the worms within the lung, and the cavitary or cystic pulmonary nodule contains both the adult worms and their eggs (Fig. The advent of high-resolution CT scanning of the chest has led to its increasing use. 2 —4-year-old girl with lingular pneumonia. Air-filled bronchi may become visible when surrounded by dense, consolidated lung parenchyma and may produce the air bronchogram sign (Fig. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513321/. The eggs are extruded into bronchioles and expectorated by the infected mammal to complete the life cycle [79]. Uterine Leiomyosarcoma: Can MRI Differentiate Leiomyosarcoma From Benign Leiomyoma Before Treatment? Normal visceral and parietal pleura are indistinguishable on CT images. Major predisposing factors for fungal infection include stem cell or solid organ transplant, hematologic malignancy, diabetic ketoacidosis, and a depressed immune system. Bilateral subpleural ground-glass opacity, linear subpleural consolidation in left upper lobe (LUL). The term consolidation is often erroneously used as a synonym for pneumonia. In 19–28% of cases, the endobronchial opacities in ABPA may be calcified or hyperattenuating on unenhanced CT images (Fig. Ancillary clinical or radiographic features suggestive of Pneumocystis pneumonia include a history of immunosuppression, imaging findings of pulmonary cysts, and the occurrence of secondary spontaneous pneumothorax [54] (Fig. Detected early, these signs can often be used to predict the causative agent and pathophysiologic mechanism and possibly to optimize patient care. This finding is often seen before frank abscess formation and is a predictor of a prolonged hospital course [26]. Radiologic signs associated with pneumonia include air bronchograms, alveolar infiltrates, the silhouette sign, and abutment of an infiltrate against a fissure.4 The lung is the second most common organ involved, after the liver, and is infected by either hematogenous or direct transdiaphragmatic spread from the liver [74–76]. • Describe the most common viral infections in immunocompetent and in immunocompromised patients. The air crescent sign is suggestive of a favorable patient prognosis [41]. [Updated 2020 Mar 6]. 16), bronchial atresia, cystic fibrosis, and postinflammatory bronchiectasis [45–47]. Over time the lesion may deflate, or it may rupture into the pleural space, the result being pneumothorax [56, 59]. The silhouette sign is produced on chest radiographs when the loss of interface occurs between structures in the same anatomic plane within an image. Axial CT image (inset) shows that over time cavity may deflate and acquire slightly thicker wall. Fig. The halo sign is typically seen early in the course of the infection. A variety of organisms, including bacteria, viruses and fungi, can cause pneumonia.Pneumonia can range in seriousness from mild to life-threatening. Example of finger-in-glove sign. Aspiration generally results in dependent tree-in-bud opacities predominating in the lower lung zones. However, a more insidious or diffuse presentation that is more difficult to differentiate from viral or fungal infection is not uncommon. 10), hemothorax, and sequelae of previous talc pleurodesis, lobectomy, or pneumonectomy. Incidence is higher at the extremes of age. Diffuse panbronchiolitis should be considered when diffuse and uniform tree-in-bud opacities are seen in a patient of East Asian descent. The objectives of this article are to discuss common and uncommon signs and findings of pulmonary infection at radiography and CT, discuss the mechanisms and pathophysiologic factors that produce those findings, and highlight several noninfectious diseases that may present with similar findings. The prevalence of this sign is decreasing, likely because of prompt administration of antibiotic therapy to patients with suspected pneumonia [18]. Example of split-pleura sign. In angioinvasive Aspergillus infection, the sign is caused by parenchymal cavitation, typically occurs 2 weeks after detection of the initial radiographic abnormality, and coincides with the return of neutrophil function (Fig. This appearance has been likened to bird's nest and reverse halo. a The rst CT scan obtained on illness day 4 revealed patchy GGOs in both the lungs. 19). Fig. bacterial pneumonia than in COVID-19 pneumonia [18, 23] (Fig. This pattern implies hematogenous dissemination of disease and is classically associated with tuberculosis but can also be seen with other infections, such as histoplasmosis and coccidioidomycosis, particularly in immunocompromised individuals [60] (Fig. Fig. 24). The intracavitary nodule represents necrotic, retracted lung tissue that is separated from peripheral viable but hemorrhagic lung parenchyma seen as outer consolidation or ground-glass opacity [42]. Recognizing the linear burrow track is the key to differentiating this entity from others, such as malignancy, fungal infection, and tuberculosis [80–83]. 21). b On day 8, the number and size of GGOs increased. Axial (left) and coronal (right) CT images show peripheral rim of consolidation (arrows) surrounding central ground-glass opacity, reticulation, and nodularity. The finger-in-glove sign is the chest radiographic finding of tubular and branching tubular opacities that appear to emanate from the hila, said to resemble gloved fingers [45, 46]. Differential diagnostic considerations include nonobstructive atelectasis, aspiration, and neoplasms, such as adenocarcinoma and lymphoma. 20). Clinical signs of radiologic pneumonia in . Axial (left) and coronal (right) CT images show air crescent sign (arrows), which occurs in immunocompromised patients with recovering neutrophil levels. The crazy-paving sign is the CT finding of a combination of ground-glass opacity and smooth interlobular septal thickening that resembles a masonry pattern used in walkways [2]. After reading the article and taking the test, the reader will be able to 1. Imaging studies are critical for the diagnosis and management of pulmonary infections. (Courtesy of Rossi S, Centro de Diagnostico Dr Enrique Rossi, Buenos Aires, Argentina). Intracavitary nodule (asterisks) represents necrotic lung tissue. 25). L. pneumophila is the organism responsible for Legionnaires disease or legionella pneumonia. A loculated effusion may have an atypical chest radiographic appearance when located within a fissure. Fig. Pneumonia can have several radiographic patterns. Radiological features. In a large group of immunocompromised patients with Aspergillus infection, Greene and colleagues [37] found that patients in whom the halo sign was visualized at CT had improved survival and response to antifungal treatment compared with those without the halo sign at CT. 5), any form of pneumonia can manifest the bulging fissure sign. 17). Example of tree-in-bud sign. In log-linear binomial regression analysis, after adjusting for potential confounders, danger signs of severe pneumonia, dehydration, hypocalcaemia, and bacteraemia were independently associated both with treatment failure and deaths in SAM children presenting with cough or respiratory difficulty and radiological pneumonia (p<0.01). Silhouette signs: Loss of clarity of the diaphragm and heart borders 4. Also present are foci of air (arrowheads) representing early abscess formation and small loculated right pleural effusion (asterisks). One can differentiate atelectasis from pneumonia by looking for direct and indirect signs of volume loss, including bronchovascular crowding, fissural displacement, mediastinal shift, and diaphragmatic elevation. 8B —35-year-old man with Staphylococcus aureus pneumonia forming lung abscess. 11 —35-year-old man with fever, neutropenia, and angioinvasive Aspergillus infection. Accreditation and Designation Statement The RSNA is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical educati… Fig. The treatment options include surgical resection, bronchial artery embolization, and instillation of antifungal agents into the cavity [40]. 1. Example of bulging fissure sign. The differential diagnosis of this finding includes other solitary cavitary or cystic lesions, such as reactivation tuberculosis infection, pneumatocele, neoplasm (e.g., primary lung cancer or metastasis), and other fungal infections. 5 —75-year-old man with alcoholism and Klebsiella pneumonia. Fig. 14). In normal lung, air-filled bronchi are not apparent on chest radiographs because they are surrounded by aerated lung parenchyma. Fig. (Courtesy of Henry T, Emory University, Atlanta, GA). The former typically requires medical treatment with antibiotics, and the latter usually requires insertion of a chest tube for drainage. Unable to process the form. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. Example of water lily sign. It is important to consider a diagnosis of bacterial pneumonia in a patient with fever and cough when the silhouette sign is detected at chest radiography. Fig. Empyema should be considered when a patient presents with fever, cough, and chest pain and CT shows the split-pleura sign. Split-pleura sign only indicates presence of exudative effusion and must be correlated with clinical findings and thoracentesis to establish accurate diagnosis. {"url":"/signup-modal-props.json?lang=us\u0026email="}. Because of the characteristic spherical shape of a lung abscess, an associated air-fluid level typically has equal lengths on posteroanterior and lateral chest radiographs (Fig. Caseous necrosis is a characteristic histologic feature of mycobacterial infection, but cavitation is a common pathologic and imaging feature of angioinvasive fungal infections, such as aspergillosis and mucormycosis. Split-pleura sign is not specific for empyema but rather indicates presence of exudative effusion. Fig. Radiation pneumonitis is a fairly common complication of radiation treatment to the chest, usually for lung cancer or breast cancer. urban hospital in bangladesh. Lung abscess is associated with increased morbidity and mortality. Example of burrow sign. An abnormal chest roentgenogram is essential for the diagnosis of ventilator-associated pneumonia. 6) but has come to be recognized as a potential manifestation of other conditions, including metastasis, arteriovenous fistula, and pulmonary vasculitis [23]. The bulging fissure sign represents expansive lobar consolidation causing fissural bulging or displacement by copious amounts of inflammatory exudate within the affected parenchyma. As it accumulates further, air penetrates the endocyst layer and causes the Cumbo sign, which comprises an air-fluid level in the endocyst and a meniscus sign (Fig. The feeding vessel sign was initially considered diagnostic of septic emboli (Fig. Example of halo sign. Septic emboli should be considered when the feeding vessel sign is seen with cavitating and noncavitating nodules and subpleural wedge-shaped consolidation. Although initially thought to be diagnostic of mycobacterial infection, the tree-in-bud sign may be an imaging manifestation of various infections caused by bacteria, fungi, parasites, and viruses [6, 8, 10]. Attenuation, and appropriate microbiological tests America, the number and size of GGOs increased or both lungs meniscus! Crab or crayfish are most commonly seen with bacterial, viral, fungal, and.. 5 ), bronchial artery embolization, and metastatic disease, IV injected material. Patient care be considered when the loss of interface occurs between structures in the same anatomic plane an! After ingestion of raw crayfish 15b —25-year-old woman with allergic bronchopulmonary aspergillosis ( ABPA.. Chest is one of the infection lobar consolidation causing fissural bulging or by... A lung infection or mucormycosis ) in combination with the air-fluid level sign when a patient of East Asian.... 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