Pooja SiKKa MD

Consolidation

• Radiologic Findings: Dense opacification in the lung tissue, loss of air-filled spaces, often appearing as a homogeneous, white area.
• CT Imaging Characteristics: Homogeneous or heterogeneous area of increased attenuation replacing normal air-filled alveoli.
• Causes: Pneumonia (bacterial, viral, fungal), aspiration, pulmonary hemorrhage, or edema.
• Differential Diagnoses: Pneumonia, lung contusion, atelectasis, or neoplasm.
• Complications: Respiratory failure, sepsis, abscess formation.

Infiltrate

• Radiologic Findings: Presence of any abnormal substance (fluid, cells, organisms) within the lung tissue causing an area of increased density.
• CT Imaging Characteristics: Non-specific, may appear as hazy or cloudy densities.
• Causes: Infections (bacterial, viral, fungal), inflammation, or malignancy.
• Differential Diagnoses: Pneumonia, pulmonary edema, atelectasis, or neoplasm.
• Complications: Abscess formation, respiratory distress, sepsis.

Silhouette Sign

• Radiologic Findings: Loss of border visibility between anatomical structures due to similar radiodensity, caused by adjacent abnormalities.
• CT Imaging Characteristics: Visual obscuring of the normal borders of structures.
• Causes: Typically seen in lung pathology where the lesion or abnormality affects the silhouette of adjacent structures.
• Differential Diagnoses: Pneumonia, mass lesions, or infiltrates adjacent to structures.
• Complications: Difficulty in precise localization of lesions or abnormalities.

Air Bronchogram

• Radiologic Findings: Visualization of air-filled bronchi surrounded by opacified lung tissue, indicating patent airways within a consolidated lung.
• CT Imaging Characteristics: Dark bronchi visible within a brighter consolidated lung.
• Causes: Consolidation in pneumonia or atelectasis.
• Differential Diagnoses: Pneumonia, atelectasis, or bronchiolitis obliterans organizing pneumonia (BOOP).
• Complications: Respiratory distress, abscess formation, or sepsis.

White Out

• Radiologic Findings: Complete opacification of the lung fields, obscuring pulmonary vessels and airway structures.
• CT Imaging Characteristics: Homogeneous, diffuse opacity in both lungs.
• Causes: Severe pneumonia, massive pulmonary edema, or alveolar hemorrhage.
• Differential Diagnoses: Acute respiratory distress syndrome (ARDS), massive pulmonary embolism, or diffuse alveolar damage.
• Complications: Severe hypoxemia, respiratory failure, and death if not managed promptly.

Bacterial Pneumonia

• Radiologic Findings: Lobar consolidation, segmental consolidation, or multifocal infiltrates with air bronchograms.
• CT Imaging Characteristics: Consolidation with air bronchograms, often lobar or segmental.
• Causes: Bacterial infection, commonly Streptococcus pneumoniae.
• Differential Diagnoses: Other forms of pneumonia, lung abscess, or neoplasm.
• Complications: Abscess formation, pleural effusion, respiratory failure, or sepsis.

Klebsiella Pneumonia

• Radiologic Findings: Often presents with dense lobar consolidation, cavitation, or abscess formation.
• CT Imaging Characteristics: Lobar consolidation, cavitation, or abscess.
• Causes: Infection by Klebsiella pneumoniae.
• Differential Diagnoses: Bacterial pneumonia, lung abscess, or tuberculosis.
• Complications: Abscess formation, septic shock, or pleural effusion.

Pneumococcal Pneumonia

• Radiologic Findings: Lobar or segmental consolidation, sometimes with pleural effusion.
• CT Imaging Characteristics: Consolidation, often lobar, and associated with pleural effusion.
• Causes: Bacterial infection by Streptococcus pneumoniae.
• Differential Diagnoses: Other forms of bacterial pneumonia, lung abscess, or tuberculosis.
• Complications: Pleural effusion, empyema, septicemia, or respiratory failure.

Viral Pneumonia

• Radiologic Findings: Diffuse, patchy, or interstitial infiltrates affecting multiple lobes.
• CT Imaging Characteristics: Patchy, ground glass opacities or consolidations.
• Causes: Infection by viruses such as influenza, respiratory syncytial virus (RSV), or adenovirus.
• Differential Diagnoses: Bacterial pneumonia, atelectasis, or interstitial lung disease.
• Complications: Respiratory failure, secondary bacterial infection, or acute respiratory distress syndrome (ARDS).

Fungal Pneumonia

• Radiologic Findings: Nodules, consolidations, or cavitations in miliary or patchy distribution.
• CT Imaging Characteristics: Nodules, consolidations, or cavities in various patterns.
• Causes: Fungal infections like Aspergillus, Cryptococcus, or Histoplasma.
• Differential Diagnoses: Bacterial or viral pneumonia, tuberculosis, or lung cancer.
• Complications: Chronic infection, dissemination, or progressive lung damage.

Atypical Pneumonia

• Radiologic Findings: Diffuse, patchy, or interstitial infiltrates affecting multiple lobes, often less well-defined.
• CT Imaging Characteristics: Patchy or diffuse opacities with less-defined margins.
• Causes: Infections by atypical pathogens like Mycoplasma pneumoniae, Chlamydophila pneumoniae, or Legionella pneumophila.
• Differential Diagnoses: Viral pneumonia, bacterial pneumonia, or interstitial lung disease.
• Complications: Respiratory failure, pleural effusion, or secondary bacterial infection.

Aspiration Pneumonia

• Radiologic Findings: Lung infiltrates in dependent areas, often affecting the right lower lobe.
• CT Imaging Characteristics: Ground glass opacities or consolidations in the posterior lung fields.
• Causes: Inhalation of foreign material, liquids, or gastric contents into the lungs.
• Differential Diagnoses: Bacterial pneumonia, chemical pneumonitis, or pulmonary edema.
• Complications: Lung abscess, empyema, acute respiratory distress syndrome (ARDS), or sepsis.

Chronic Eosinophilic Pneumonia

• Radiologic Findings: Peripheral opacities or consolidations involving multiple lobes.
• CT Imaging Characteristics: Peripheral opacities or consolidations with ground glass appearance.
• Causes: Unknown etiology, potentially related to immune response or allergic reactions.
• Differential Diagnoses: Other interstitial lung diseases, atypical pneumonia, or organizing pneumonia.
• Complications: Chronic respiratory insufficiency, progressive fibrosis, or recurrent episodes.

Organizing Pneumonia

Radiologic Findings: Peripheral consolidations with a surrounding “halo” of ground-glass opacity. CT Imaging Characteristics: Consolidations with a peri-lesional ground-glass halo. Causes: Inflammatory processes, infections, autoimmune diseases, or exposure to certain medications. Differential Diagnoses: Bacterial/viral pneumonia, malignancy, or organizing pneumonia secondary to collagen vascular disease. Complications: Chronic lung disease, relapses, or progression to fibrosis.

Round Pneumonia Radiologic Findings: Rounded and solitary consolidation, commonly seen in children. CT Imaging Characteristics: Well-circumscribed, rounded opacities. Causes: Typically bacterial infections, often Streptococcus pneumoniae. Differential Diagnoses: Abscess, neoplasm, or fungal infections. Complications: Resolution with treatment; complications are rare.

Compressive Atelectasis Radiologic Findings: Lung collapse due to external compression or mass effect. CT Imaging Characteristics: Collapsed lung with a shift of mediastinal structures toward the affected side. Causes: Tumors, lymphadenopathy, pleural effusion, or pneumothorax. Differential Diagnoses: Mass lesions, pleural diseases, or postoperative changes. Complications: Respiratory distress, hypoxia, or secondary infection.

Post Obstructive Atelectasis Radiologic Findings: Lung collapse due to obstruction of a bronchus by an intraluminal or extraluminal mass. CT Imaging Characteristics: Collapse of lung segments or lobes. Causes: Tumors, foreign bodies, mucus plugs, or lymphadenopathy. Differential Diagnoses: Bronchial obstruction, pneumonia, or lung fibrosis. Complications: Pneumonia, respiratory failure, or secondary infection.

Rounded Atelectasis Radiologic Findings: Round or oval-shaped areas of atelectasis with a curvilinear opacity (comet tail sign). CT Imaging Characteristics: Pleural-based atelectasis with a comet tail appearance. Causes: Chronic pleural inflammation, asbestos exposure, or scarring. Differential Diagnoses: Lung nodules, pleural masses, or subpleural fibrosis. Complications: Infrequent; usually asymptomatic.

Ground Glass Opacity (GGO) Radiologic Findings: Hazy increased opacity in the lung with preserved bronchial and vascular margins. CT Imaging Characteristics: Non-specific opacity with increased lung density but without obscuration of vessels. Causes: Infections, edema, hemorrhage, or early interstitial lung disease. Differential Diagnoses: Pulmonary edema, early pneumonia, or interstitial lung disease. Complications: Progression to fibrosis, respiratory failure, or secondary infection.

Secondary Lobule Radiologic Findings: Functional unit of the lung comprising multiple acini supplied by a single bronchiole. CT Imaging Characteristics: Hexagonal-shaped structures on CT due to the pattern of lung anatomy. Causes: Structural arrangement of the lung’s acinar units. Differential Diagnoses: No pathological conditions associated. Complications: No direct complications associated.

Interlobular Septal Thickening Radiologic Findings: Thickening of connective tissue between secondary pulmonary lobules. CT Imaging Characteristics: Linear opacifications surrounding the secondary pulmonary lobules. Causes: Infections, interstitial lung diseases, or lymphatic disorders. Differential Diagnoses: Lymphangitic carcinomatosis, pulmonary edema, or sarcoidosis. Complications: Respiratory insufficiency, fibrosis, or chronic lung disease.

Centrilobular Nodule Radiologic Findings: Small nodules with a central location within secondary pulmonary lobules. CT Imaging Characteristics: Nodules with a central ground-glass or low-density area surrounded by consolidation. Causes: Infections, granulomatous diseases, or hypersensitivity pneumonitis. Differential Diagnoses: Granulomas, fungal infections, or bronchiolitis obliterans organizing pneumonia (BOOP). Complications: Progression to fibrosis or chronic lung disease.

Centrilobular Emphysema Radiologic Findings: Destruction of the lung tissue, particularly in centrilobular regions. CT Imaging Characteristics: Centrilobular lucencies due to air trapping and dilatation of terminal bronchioles. Causes: Smoking, chronic lung diseases, or genetic predisposition. Differential Diagnoses: Panlobular emphysema, paraseptal emphysema, or bronchiectasis. Complications: Respiratory insufficiency, chronic obstructive pulmonary disease (COPD), or pneumothorax.

Paraseptal Emphysema Radiologic Findings: Distal acinar emphysema adjacent to the pleura and interlobular septa. CT Imaging Characteristics: Bullae or cysts adjacent to the pleura and subpleural regions. Causes: Smoking, chronic lung diseases, or genetic predisposition. Differential Diagnoses: Bullous lung diseases, pneumothorax, or congenital lung abnormalities. Complications: Spontaneous pneumothorax, infection of bullae, or respiratory distress.

Panlobular Emphysema Radiologic Findings: Uniform and diffuse destruction of the entire acinus. CT Imaging Characteristics: Homogeneous low-density lung fields without zonal variation. Causes: Alpha-1 antitrypsin deficiency, smoking, or congenital disorders. Differential Diagnoses: Centrilobular emphysema, paraseptal emphysema, or bullous lung disease. Complications: Chronic respiratory failure, hypoxemia, or recurrent infections.

Bleb and Bulla Radiologic Findings: Air-filled spaces within the lung parenchyma. CT Imaging Characteristics: Thin-walled, well-demarcated air-filled spaces. Causes: Congenital, smoking-related, or traumatic lung parenchymal changes. Differential Diagnoses: Pneumatocele, pneumothorax, or lung cysts. Complications: Spontaneous pneumothorax, infection, or rupture causing tension pneumothorax.

Left Atrial Enlargement Radiologic Findings: Increased size of the left atrium beyond normal limits. CT Imaging Characteristics: Dilation of the left atrium with a rounded contour. Causes: Mitral valve disease, left ventricular failure, or chronic hypertension. Differential Diagnoses: Dilated cardiomyopathy, pericardial effusion, or atrial fibrillation. Complications: Congestive heart failure, pulmonary edema, or thromboembolism.

Heart Failure Equalization Radiologic Findings: Radiographic findings showing equalization of cardiac chamber sizes. CT Imaging Characteristics: Cardiac chamber size equalization due to elevated left atrial pressure. Causes: Acute heart failure, myocardial infarction, or valvular heart disease. Differential Diagnoses: Cardiac tamponade, constrictive pericarditis, or restrictive cardiomyopathy. Complications: Pulmonary edema, cardiogenic shock, or systemic embolization.

Cephalization Radiologic Findings: Redistribution of pulmonary blood flow towards the upper lung fields. CT Imaging Characteristics: Increased vascularity in the upper lung zones. Causes: Congestive heart failure, pulmonary hypertension, or chronic lung diseases. Differential Diagnoses: Pulmonary embolism, pulmonary artery stenosis, or interstitial lung disease. Complications: Respiratory distress, pulmonary hypertension, or pulmonary edema.

Bronchial Artery to Airway Ratio Radiologic Findings: Ratio between the bronchial artery and the adjacent airway size. CT Imaging Characteristics: Measurement of the bronchial artery diameter compared to the adjacent bronchus. Causes: Pulmonary arterial hypertension, congenital abnormalities, or chronic lung diseases. Differential Diagnoses: Pulmonary artery enlargement, vascular malformations, or chronic thromboembolic disease. Complications: Pulmonary hypertension, right heart strain, or hemoptysis.

Interstitial Edema Radiologic Findings: Accumulation of fluid within the interstitial space of the lung. CT Imaging Characteristics: Linear or reticular opacities representing fluid accumulation in the interlobular septa. Causes: Cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), or interstitial lung diseases. Differential Diagnoses: Interstitial lung diseases, lymphangitic carcinomatosis, or infectious pneumonias. Complications: Respiratory distress, hypoxemia, or progression to fibrosis.

Kerley B Lines Radiologic Findings: Short, thin, linear opacities seen at the lung periphery. CT Imaging Characteristics: Short linear opacities perpendicular to the pleural surface. Causes: Interstitial edema, congestive heart failure, or lymphatic obstruction. Differential Diagnoses: Interstitial lung diseases, pulmonary fibrosis, or lymphangitic carcinomatosis. Complications: Progression to fibrosis, respiratory failure, or chronic lung disease.

Alveolar Edema Radiologic Findings: Filling of alveoli with fluid. CT Imaging Characteristics: Increased lung density due to alveolar filling with fluid. Causes: Cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), or severe pneumonia. Differential Diagnoses: ARDS, interstitial lung diseases, or pneumonia. Complications: Respiratory failure, hypoxemia, or sepsis.

Solid Nodule Radiologic Findings: Round or oval-shaped opacity in the lung parenchyma. CT Imaging Characteristics: Well-defined, homogenous opacity with a solid appearance. Causes: Neoplastic growths, granulomas, or infections. Differential Diagnoses: Lung cancers, metastases, granulomas, or benign tumors. Complications: Malignant transformation, metastasis, or bleeding.

Ground Glass Nodule Radiologic Findings: Nodule with a ground-glass appearance, indicative of partial lung opacification. CT Imaging Characteristics: Hazy opacity with preserved bronchial and vascular margins. Causes: Infections, inflammatory processes, or early neoplastic changes. Differential Diagnoses: Inflammatory nodules, early stage lung cancers, or organizing pneumonia. Complications: Progression to malignancy, metastasis, or bleeding.

Mixed Nodule Radiologic Findings: Nodule with areas of both solid and ground-glass opacity. CT Imaging Characteristics: Variable appearance with both solid and ground-glass components. Causes: Mixture of neoplastic, inflammatory, or infectious etiologies. Differential Diagnoses: Atypical infections, inflammatory processes, or mixed histology tumors. Complications: Variable based on underlying cause.

Miliary Tuberculosis Radiologic Findings: Numerous small pulmonary nodules diffusely scattered throughout the lungs. CT Imaging Characteristics: Multiple small nodules resembling millet seeds spread across the lungs. Causes: Infection by Mycobacterium tuberculosis. Differential Diagnoses: Other miliary infections, fungal infections, or metastatic diseases. Complications: Dissemination, severe systemic illness, or organ failure.

Bronchocentric Nodule Radiologic Findings: Nodule with a central bronchus or airway. CT Imaging Characteristics: Nodule centered around a bronchus or airway. Causes: Infections, granulomas, or neoplastic growths. Differential Diagnoses: Bronchiolitis, inflammatory nodules, or endobronchial tumors. Complications: Airway obstruction, secondary infection, or bronchiectasis.

Micronodules Radiologic Findings: Multiple tiny nodules < 3mm in diameter scattered throughout the lungs. CT Imaging Characteristics: Numerous small, well-defined nodules. Causes: Infections, metastases, or inflammatory diseases. Differential Diagnoses: Metastases, miliary tuberculosis, or sarcoidosis. Complications: Progression to larger lesions, hemorrhage, or fibrosis.

Cavitating Nodule Radiologic Findings: Nodule with a cavity or central lucency. CT Imaging Characteristics: Nodule with a central airspace or cavity. Causes: Infections, neoplasms, or abscess formation. Differential Diagnoses: Lung abscesses, necrotic tumors, or tuberculosis. Complications: Rupture, hemorrhage, or secondary infections.

Calcified Nodule Radiologic Findings: Nodule with calcifications visible on imaging. CT Imaging Characteristics: Nodule with dense, calcified areas. Causes: Granulomas, healed infections, or neoplasms. Differential Diagnoses: Tuberculoma, fungal infections, or benign tumors. Complications: Stability or regression over time; rare complications include calcification-induced inflammation.

Spiculated Nodule Radiologic Findings: Nodule with lines extending radially outward resembling spicules. CT Imaging Characteristics: Nodule with irregular, spiky borders. Causes: Neoplasms, metastases, or invasive tumors. Differential Diagnoses: Lung cancers, metastases, or inflammatory processes. Complications: Malignancy, metastasis, or growth over time.

Solid Lung Mass Radiologic Findings: Space-occupying lesion within lung tissue. CT Imaging Characteristics: Well-defined, homogeneous density with no internal lucency. Causes: Neoplasms, infections, or granulomas. Differential Diagnoses: Lung cancers, solitary pulmonary nodules, or inflammatory masses. Complications: Malignancy, metastasis, or compression of nearby structures.

Spiculated Lung Mass Radiologic Findings: Lung mass with spiky projections extending from its margins. CT Imaging Characteristics: Irregular margins with spicules extending into the lung. Causes: Malignant tumors, invasive neoplasms, or metastases. Differential Diagnoses: Lung adenocarcinoma, metastases, or inflammatory masses. Complications: Malignancy, metastasis, or growth over time.

Cavitating Lung Mass Radiologic Findings: Lung mass with a central cavity or lucency. CT Imaging Characteristics: Lesion with a central airspace or cavity. Causes: Infections, necrotic tumors, or abscesses. Differential Diagnoses: Lung abscesses, necrotic neoplasms, or tuberculosis. Complications: Rupture, hemorrhage, or secondary infections.

Bronchiectasis

• Radiologic Findings: Irreversible dilation and thickening of bronchial walls.
• CT Imaging Characteristics: Dilated bronchi with thickened walls, often appearing as tram lines or signet rings.
• Causes: Infections, cystic fibrosis, or autoimmune conditions.
• Differential Diagnoses: Chronic obstructive pulmonary disease (COPD), chronic bronchitis, or cystic fibrosis.
• Complications: Recurrent infections, respiratory failure, hemoptysis.

Bronchiolectasis

• Radiologic Findings: Abnormal dilation of bronchioles.
• CT Imaging Characteristics: Abnormal widening of small airways.
• Causes: Infections, chronic inflammation, or inhalation injuries.
• Differential Diagnoses: Bronchiectasis, bronchiolitis obliterans, or chronic bronchitis.
• Complications: Recurrent infections, respiratory distress, chronic cough.

Loculated Pleural Effusion

• Radiologic Findings: Pleural effusion confined within a localized space within the pleural cavity.
• CT Imaging Characteristics: Fluid accumulation in a confined area, often encapsulated by fibrinous or fibrous tissue.
• Causes: Infections, trauma, or post-surgical scarring.
• Differential Diagnoses: Empyema, pleural tumors, or pleural fibrosis.
• Complications: Chronic effusion, fibrosis, or need for drainage.

Empyema

• Radiologic Findings: Accumulation of pus within the pleural space.
• CT Imaging Characteristics: Pleural effusion with low attenuation areas suggestive of pus.
• Causes: Bacterial infections, pneumonia, or post-surgical complications.
• Differential Diagnoses: Complicated parapneumonic effusion, lung abscess, or hemothorax.
• Complications: Sepsis, lung loculations, respiratory failure.

Simple Pleural Effusion

• Radiologic Findings: Accumulation of fluid within the pleural space.
• CT Imaging Characteristics: Smooth, even fluid accumulation in the pleural cavity.
• Causes: Congestive heart failure, infections, or malignancies.
• Differential Diagnoses: Congestive heart failure, pneumonia, or pulmonary embolism.
• Complications: May resolve with treatment; if chronic, can lead to fibrosis or recurrence.

Loculated Pneumothorax

• Radiologic Findings: Collection of air trapped in specific areas of the pleural space.
• CT Imaging Characteristics: Air accumulation in pockets separated by visceral and parietal pleura.
• Causes: Trauma, underlying lung disease, or post-surgical complications.
• Differential Diagnoses: Tension pneumothorax, pleural effusion, or bullae.
• Complications: Respiratory distress, tension pneumothorax if unrelieved.

Tension Pneumothorax

• Radiologic Findings: Shift of mediastinal structures away from affected lung due to trapped air under pressure.
• CT Imaging Characteristics: Collapsed lung, mediastinal shift, compression of contralateral lung.
• Causes: Trauma, medical procedures, or underlying lung disease.
• Differential Diagnoses: Pneumothorax, massive pleural effusion.
• Complications: Cardiac arrest, severe respiratory distress.

Pseudopneumothorax

• Radiologic Findings: Appearance similar to pneumothorax but without actual lung collapse.
• CT Imaging Characteristics: Lack of visceral pleural line disruption.
• Causes: Pleural adhesions, misplaced chest tubes, or artifact.
• Differential Diagnoses: Pneumothorax, pleural thickening.
• Complications: Misinterpretation leading to unnecessary intervention.

Tree-in-Bud Appearance

• Radiologic Findings: Pattern resembling budding tree branches due to impacted small airways.
• CT Imaging Characteristics: Multiple centrilobular branching opacities.
• Causes: Infections (viral, bacterial), bronchiolitis, or aspiration.
• Differential Diagnoses: Bronchiolitis, small airway disease, or mucus plugging.
• Complications: Progression to bronchiectasis, recurrent infections.

Centrilobular Nodules

• Radiologic Findings: Small nodules located in the center of secondary pulmonary lobules.
• CT Imaging Characteristics: Nodules seen in the center of secondary lobules.
• Causes: Infections, granulomatous diseases, or occupational lung diseases.
• Differential Diagnoses: Inflammatory diseases, sarcoidosis, or hypersensitivity pneumonitis.
• Complications: Progression to diffuse lung disease, fibrosis.

Mosaic Attenuation

• Radiologic Findings: Patchy areas of lung with varying attenuation, appearing mosaic-like on imaging.
• CT Imaging Characteristics: Areas of high and low attenuation interspersed throughout the lung.
• Causes: Air trapping due to small airway diseases, bronchiolitis, or vascular disorders affecting lung perfusion.
• Differential Diagnoses: Asthma, bronchiolitis obliterans, or pulmonary embolism.
• Complications: Respiratory distress, chronic lung disease progression.

Air Trapping

• Radiologic Findings: Retention of air in the lungs during expiration, leading to persistent or increased lung density.
• CT Imaging Characteristics: Increased lung density on expiration compared to inspiration.
• Causes: Obstructive lung diseases like asthma, chronic bronchitis, or bronchiolitis.
• Differential Diagnoses: Emphysema, bronchiolitis obliterans, or cystic fibrosis.
• Complications: Chronic respiratory failure, recurrent infections.

Apical Pleural Cap

• Radiologic Findings: Linear opacity at the lung apex adjacent to the pleura.
• CT Imaging Characteristics: Thin linear opacity along the lung apex.
• Causes: Pleural fibrosis, scarring from previous infection or inflammation.
• Differential Diagnoses: Tuberculosis, old granulomatous diseases, or previous pleural effusion.
• Complications: Rarely symptomatic, may indicate previous lung pathology.

Reticular Pattern

• Radiologic Findings: Net-like appearance due to interlacing linear opacities.
• CT Imaging Characteristics: Mesh-like pattern of linear opacities distributed throughout the lung.
• Causes: Interstitial lung diseases, fibrosis, or scarring.
• Differential Diagnoses: Idiopathic pulmonary fibrosis, sarcoidosis, or collagen vascular diseases.
• Complications: Progressive fibrosis, respiratory failure.

Honeycomb Lung

• Radiologic Findings: Appearance of cystic airspaces with thick walls, resembling a honeycomb.
• CT Imaging Characteristics: Clustered cystic airspaces surrounded by thickened walls in a honeycomb pattern.
• Causes: End-stage lung diseases, idiopathic pulmonary fibrosis, or advanced interstitial lung diseases.
• Differential Diagnoses: End-stage fibrosis, chronic interstitial lung diseases.
• Complications: Severe respiratory distress, limited treatment options.

Ground Glass Opacity

• Radiologic Findings: Hazy, increased opacity in the lung with preservation of bronchial and vascular margins.
• CT Imaging Characteristics: Lung areas with increased density but still allowing visualization of vascular and bronchial structures.
• Causes: Inflammatory processes, infections, edema, or early interstitial lung disease.
• Differential Diagnoses: Pneumonia, viral infections, pulmonary edema, or early fibrosis.
• Complications: Progression to fibrosis, chronic respiratory insufficiency.

Traction Bronchiectasis

• Radiologic Findings: Irregular dilatation of bronchi due to adjacent fibrosis or scarring.
• CT Imaging Characteristics: Bronchiectatic changes caused by traction from fibrotic lung tissue.
• Causes: Fibrosis, scarring, or chronic lung diseases.
• Differential Diagnoses: Idiopathic pulmonary fibrosis, chronic interstitial lung diseases.
• Complications: Chronic respiratory failure, recurrent infections.

Subpleural Sparing

• Radiologic Findings: Preservation of normal lung density at the lung periphery.
• CT Imaging Characteristics: Areas of normal lung density adjacent to areas of disease or abnormality.
• Causes: Certain lung diseases affecting the peripheral lung preferentially, sparing the subpleural regions.
• Differential Diagnoses: Some interstitial lung diseases, organizing pneumonia.
• Complications: Dependent on the underlying condition causing the sparing.

Thin-Walled Cysts

• Radiologic Findings: Presence of small air-filled spaces within lung parenchyma with thin walls.
• CT Imaging Characteristics: Rounded lucencies in the lung tissue with delicate walls.
• Causes: Emphysema, Langerhans cell histiocytosis, or lymphangioleiomyomatosis.
• Differential Diagnoses: Bullae, cavities, or pneumatoceles.
• Complications: Potential for rupture, pneumothorax, or respiratory insufficiency.

Thick-Walled Cysts

• Radiologic Findings: Air-filled spaces with thicker walls than thin-walled cysts.
• CT Imaging Characteristics: Rounded lucencies in the lung tissue with thicker, more defined walls.
• Causes: Chronic infections, bronchiectasis, or inflammatory lung diseases.
• Differential Diagnoses: Lung abscesses, cavitating tumors, or complex pneumonias.
• Complications: Secondary infections, abscess formation.

Eggshell Calcification of Lymph Nodes

• Radiologic Findings: Calcification outlining the periphery of lymph nodes.
• CT Imaging Characteristics: Characterized by thin, calcified rims around lymph nodes.
• Causes: Chronic granulomatous diseases, histoplasmosis, or healed infections.
• Differential Diagnoses: Tuberculosis, sarcoidosis, or fungal infections.
• Complications: Generally benign, may occasionally cause local compression symptoms.

Hampton’s Hump

• Radiologic Findings: Wedge-shaped pleural-based opacities in the lung.
• CT Imaging Characteristics: Triangular or wedge-shaped peripheral lung opacities.
• Causes: Pulmonary infarction due to embolism or ischemia.
• Differential Diagnoses: Pulmonary embolism, pulmonary infarction, or pleural-based mass.
• Complications: Risk of recurrent embolism, chronic pulmonary hypertension.

Hiatal Hernia

• Radiologic Findings: Protrusion of the stomach through the diaphragmatic esophageal hiatus.
• CT Imaging Characteristics: Stomach herniating into the thoracic cavity through the esophageal hiatus.
• Causes: Weakness or disruption of the diaphragm, congenital predisposition, or trauma.
• Differential Diagnoses: Gastroesophageal reflux disease (GERD), paraesophageal hernia.
• Complications: Reflux symptoms, Barrett’s esophagus, volvulus, or incarceration.

Diaphragmatic Hernia

• Radiologic Findings: Organs herniating through a defect in the diaphragm.
• CT Imaging Characteristics: Abdominal organs entering the thoracic cavity through a diaphragmatic defect.
• Causes: Congenital defects, trauma, or surgery.
• Differential Diagnoses: Hiatal hernia, eventration of the diaphragm.
• Complications: Organ strangulation, respiratory compromise, gastrointestinal obstruction.

Traumatic Hernia

• Radiologic Findings: Herniation of abdominal organs due to trauma or injury.
• CT Imaging Characteristics: Abdominal organ protrusion through a traumatic defect in the abdominal wall.
• Causes: Blunt or penetrating trauma to the abdomen, resulting in muscle or fascial defects.
• Differential Diagnoses: Diaphragmatic hernia, muscle tears, or abdominal wall defects.
• Complications: Bowel obstruction, perforation, or sepsis.

Gynecomastia

• Radiologic Findings: Enlargement of the male breast tissue.
• CT Imaging Characteristics: Increased breast tissue density in males.
• Causes: Hormonal imbalances, medications, liver disease, or genetic conditions.
• Differential Diagnoses: Breast cancer in males, pseudogynecomastia.
• Complications: Psychological distress, potential underlying conditions.

Air Bronchogram

• Radiologic Findings: Visualization of air-filled bronchi amidst opacified lung tissue.
• CT Imaging Characteristics: Darkened bronchi visible against opacified lung parenchyma.
• Causes: Presence of air in patent bronchi surrounded by consolidated lung tissue.
• Differential Diagnoses: Pneumonia, atelectasis, or bronchiolitis obliterans organizing pneumonia (BOOP).
• Complications: Respiratory distress, abscess formation, or sepsis.

Air Crescent Sign

• Radiologic Findings: Crescent-shaped lucency adjacent to a lung mass or lesion.
• CT Imaging Characteristics: Curved, gas-filled space bordering a mass or cavity.
• Causes: Represents an air-filled cavity or space adjacent to a pulmonary mass, often post-trauma or post-surgical resection.
• Differential Diagnoses: Aspergilloma, pulmonary infarction, or cavitary lung lesions.
• Complications: Risk of rupture or hemorrhage.

Deep Sulcus Sign on a Supine Radiograph

• Radiologic Findings: Deep costophrenic sulcus seen on supine chest X-ray.
• X-ray Imaging Characteristics: Deeper-than-usual angle between the chest wall and diaphragm.
• Causes: Pneumothorax or air accumulation in the pleural space in a supine position.
• Differential Diagnoses: Tension pneumothorax, pneumomediastinum, or pleural effusion.
• Complications: Respiratory compromise, tension pneumothorax.

Continuous Diaphragm Sign

• Radiologic Findings: Continuous, smooth diaphragm margin with no visible interruption.
• CT Imaging Characteristics: Uninterrupted diaphragmatic contour.
• Causes: Indicates absence of intrathoracic pathology affecting the diaphragm or pleura.
• Differential Diagnoses: Normal diaphragmatic contour, absence of pathology.
• Complications: N/A, as this sign indicates a normal finding.

Ring Around the Artery Sign

• Radiologic Findings: Circular or ring-shaped opacity surrounding a pulmonary artery.
• CT Imaging Characteristics: Opacification encircling a pulmonary artery, often indicating an embolus or mass.
• Causes: Pulmonary embolism, tumor encircling vessels.
• Differential Diagnoses: Pulmonary artery enlargement, lymphadenopathy, or arteritis.
• Complications: Pulmonary infarction, increased risk of thromboembolism.

Fallen Lung Sign

• Radiologic Findings: Dependent lung lobe presenting lower than usual due to atelectasis or consolidation.
• CT Imaging Characteristics: Lower-positioned lung segment due to loss of volume.
• Causes: Volume loss in dependent lung segments due to atelectasis or pathology.
• Differential Diagnoses: Atelectasis, pleural effusion, or lung collapse.
• Complications: Respiratory distress, pneumonia.

Flat Waist Sign

• Radiologic Findings: The waist of the heart appears flat on a frontal chest X-ray.
• X-ray Imaging Characteristics: Absence of the typical waist indentation of the heart silhouette.
• Causes: Pericardial effusion or enlargement, restrictive pericarditis.
• Differential Diagnoses: Pericardial effusion, cardiomegaly, or pericardial thickening.
• Complications: Cardiac tamponade, heart failure.

Gloved Finger Sign

• Radiologic Findings: Opacity in the pleural space resembling the shape of a gloved finger.
• CT Imaging Characteristics: Pleural effusion with finger-like extensions into the lung field.
• Causes: Pleural effusion with loculated fluid collections.
• Differential Diagnoses: Empyema, complex effusions, or hemothorax.
• Complications: Infection, impaired lung expansion.

Golden S Sign

• Radiologic Findings: Curvilinear opacities resembling the shape of a “golden S” on a chest X-ray.
• X-ray Imaging Characteristics: Opacities forming an S-shaped curve in the lung fields.
• Causes: Collapse or mass effect on the left lower lobe bronchus.
• Differential Diagnoses: Left lower lobe collapse, mass, or hilar lymphadenopathy.
• Complications: Respiratory distress, pneumonia.

Luftsichel Sign

• Radiologic Findings: Crescentic lucency adjacent to the heart border on chest X-ray.
• X-ray Imaging Characteristics: Curved radiolucency adjacent to the left cardiac border.
• Causes: Pericardial effusion displacing the left lower lobe, emphysema.
• Differential Diagnoses: Pericardial effusion, emphysema, or pneumothorax.
• Complications: Cardiac tamponade, respiratory compromise.

Hampton Hump

• Radiologic Findings: Wedge-shaped pleural-based opacity.
• CT Imaging Characteristics: Peripheral lung opacity with a triangular appearance.
• Causes: Pulmonary infarction due to embolism.
• Differential Diagnoses: Pulmonary embolism, pulmonary infarction, or pleural-based mass.
• Complications: Risk of recurrent embolism, chronic pulmonary hypertension.

Cervicothoracic Sign (Tapered Margins Sign)

• Radiologic Findings: Tapering or narrowing of the margins of an abnormality.
• CT Imaging Characteristics: Convergence or narrowing of lesions at their edges.
• Causes: Pleural-based lesions or masses.
• Differential Diagnoses: Pulmonary masses, nodules, or infiltrates.
• Complications: Dependent on the underlying cause (e.g., malignancy, infection).

Figure 3 Sign

• Radiologic Findings: Triangular-shaped opacity with a right angle.
• CT Imaging Characteristics: Abnormality with a distinct angular appearance.
• Causes: Abnormalities associated with specific lung pathology.
• Differential Diagnoses: Pulmonary infarction, pulmonary embolism, or atypical lung lesions.
• Complications: Varies based on underlying condition.

Fat Pad Sign or Sandwich Sign

• Radiologic Findings: Linear fat opacity near the pleural surface.
• CT Imaging Characteristics: Visible linear fat density next to the pleura.
• Causes: Displacement or alteration of pleural fat by adjacent pathology.
• Differential Diagnoses: Pleural-based masses, nodules, or effusions.
• Complications: Indicative of underlying pathology, necessitates further evaluation.

Scimitar Sign

• Radiologic Findings: Curved opacity resembling a scimitar sword.
• CT Imaging Characteristics: Abnormal vascular appearance, resembling a scimitar’s shape.
• Causes: Anomalous pulmonary venous drainage.
• Differential Diagnoses: Scimitar syndrome, congenital heart anomalies.
• Complications: Risk of pulmonary hypertension, heart failure.

Hilum Overlay Sign and Hilum Convergence Sign

• Radiologic Findings: Appearance of hilar structures overlaid on lung lesions.
• CT Imaging Characteristics: Hilar structures appearing to overlay or converge with lesions.
• Causes: Lesions adjacent to the hila.
• Differential Diagnoses: Lung masses, nodules, or lesions adjacent to the hilar structures.
• Complications: Dependent on underlying pathology.

Beaded Septum Sign

• Radiologic Findings: Multiple nodular thickenings of the interlobular septa.
• CT Imaging Characteristics: Multiple, small, nodular thickenings along the interlobular septa.
• Causes: Lymphatic dilation, lymphangitis, or sarcoidosis.
• Differential Diagnoses: Sarcoidosis, lymphangitis, or lymphatic metastasis.
• Complications: Reflects underlying pathology, requires further evaluation.

Tree-in-Bud

• Radiologic Findings: Appearance of branching nodules along bronchi.
• CT Imaging Characteristics: Multiple small nodules along bronchial walls.
• Causes: Infection, bronchiolitis, or inflammatory bronchial changes.
• Differential Diagnoses: Bronchiolitis, small airway disease, or endobronchial spread.
• Complications: Reflects underlying bronchial pathology, requires investigation.

Centrilobular Nodules

• Radiologic Findings: Small nodules with central lobular distribution.
• CT Imaging Characteristics: Nodules present in the central portions of the secondary pulmonary lobules.
• Causes: Infection, granulomatous diseases, or hypersensitivity pneumonitis.
• Differential Diagnoses: Infectious or inflammatory lung diseases.
• Complications: Indicative of underlying pathology, necessitates further assessment.

Perilymphatic Nodules

• Radiologic Findings: Nodules distributed around lymphatic vessels.
• CT Imaging Characteristics: Nodules surrounding lymphatic structures.
• Causes: Granulomatous diseases, sarcoidosis, or lymphatic spread.
• Differential Diagnoses: Lymphatic metastases, sarcoidosis, or lymphangitic spread.
• Complications: Reflects underlying lymphatic pathology, necessitates further evaluation.

Random or Miliary Nodules

• Radiologic Findings: Numerous small nodules scattered randomly.
• CT Imaging Characteristics: Multiple small nodules distributed evenly throughout the lung.
• Causes: Infections like tuberculosis, miliary metastases, or hematogenous spread.
• Differential Diagnoses: Miliary tuberculosis, metastases, or fungal infections.
• Complications: Respiratory distress, disseminated infection.

Crazy Paving

• Radiologic Findings: Ground glass opacity with superimposed interlobular septal thickening.
• CT Imaging Characteristics: Geometric appearance resembling irregular paving stones.
• Causes: Alveolar proteinosis, Pneumocystis pneumonia, or interstitial lung disease.
• Differential Diagnoses: Alveolar proteinosis, Pneumocystis pneumonia, or viral pneumonia.
• Complications: Progressive respiratory failure, risk of infection.

Ground Glass Halo

• Radiologic Findings: Central ground glass opacity surrounded by a denser area.
• CT Imaging Characteristics: Central ground glass appearance surrounded by a denser rim.
• Causes: Pulmonary hemorrhage, organizing pneumonia, or infarction.
• Differential Diagnoses: Pulmonary infarction, organizing pneumonia, or metastases.
• Complications: Risk of hemorrhage, progression of underlying condition.

Mosaic Attenuation

• Radiologic Findings: Patchy areas of different attenuation in the lung.
• CT Imaging Characteristics: Variegated appearance of lung parenchyma due to different densities.
• Causes: Air trapping in asthma, chronic obstructive pulmonary disease (COPD), or bronchiolitis.
• Differential Diagnoses: Asthma, bronchiolitis, or COPD exacerbation.
• Complications: Progressive lung damage, chronic respiratory insufficiency.

Consolidation

• Radiologic Findings: Homogeneous, opaque lung tissue with airless alveoli.
• CT Imaging Characteristics: Alveolar opacification, loss of air-filled spaces.
• Causes: Pneumonia, pulmonary edema, or hemorrhage.
• Differential Diagnoses: Pneumonia, pulmonary edema, or atelectasis.
• Complications: Respiratory failure, sepsis.

Ground Glass Opacity

• Radiologic Findings: Hazy increased opacity with preserved bronchial and vascular margins.
• CT Imaging Characteristics: Partially obscuring lung parenchyma with a hazy, ground glass appearance.
• Causes: Pulmonary edema, atypical infections, or interstitial lung disease.
• Differential Diagnoses: Interstitial lung disease, organizing pneumonia, or infections.
• Complications: Chronic lung damage, progressive fibrosis.

Honeycombing

• Radiologic Findings: Lung parenchyma with clustered, cystic airspaces resembling honeycombs.
• CT Imaging Characteristics: Multiple small cystic spaces with thick walls in the lung.
• Causes: End-stage lung fibrosis, interstitial lung diseases.
• Differential Diagnoses: Idiopathic pulmonary fibrosis, chronic interstitial lung diseases.
• Complications: Chronic respiratory failure, increased risk of infections.

Interlobular and Intralobular Septal Thickening and Reticulation

• Radiologic Findings: Thickening of interlobular and intralobular septa, forming a net-like pattern.
• CT Imaging Characteristics: Interconnecting linear opacities resembling a net or mesh.
• Causes: Interstitial lung diseases, pulmonary edema, or lymphangitic spread.
• Differential Diagnoses: Interstitial lung diseases, lymphangitic carcinomatosis.
• Complications: Progressive lung damage, respiratory compromise.

Juxtaphrenic Peak

• Radiologic Findings: Acute angle between the diaphragm and lateral chest wall.
• X-ray Imaging Characteristics: Sharp angle formed at the diaphragmatic curvature.
• Causes: Partial lung collapse, pleural effusion.
• Differential Diagnoses: Pneumothorax, pleural effusion, or lung collapse.
• Complications: Respiratory distress, exacerbation of underlying condition.

Secondary Pulmonary Lobule

• Radiologic Findings: Smallest functional unit of the lung visible on CT.
• CT Imaging Characteristics: Hexagonal-shaped structures with a central bronchiole.
• Causes: Basic unit for studying lung anatomy and pathology.
• Differential Diagnoses: N/A, anatomical structure.
• Complications: N/A, anatomical structure for reference.

Mass and Nodule

• Radiologic Findings: Abnormal tissue growth in the lung.
• CT Imaging Characteristics: Defined lesion with distinct margins.
• Causes: Tumors, infections, or inflammatory lesions.
• Differential Diagnoses: Benign or malignant tumors, granulomas.
• Complications: Varies depending on the underlying cause (malignancy, infection).

Parenchymal and Subpleural Bands

• Radiologic Findings: Linear opacities extending from the pleura into the lung.
• CT Imaging Characteristics: Linear densities along the pleura or within lung tissue.
• Causes: Fibrosis, chronic lung disease, or inflammation.
• Differential Diagnoses: Chronic lung diseases, fibrosis, or scarring.
• Complications: Indicative of underlying chronic lung pathology.

Pleural Plaques or Pseudoplagues

• Radiologic Findings: Calcified or fibrotic lesions on the pleural surface.
• CT Imaging Characteristics: Dense, flat, pleural-based lesions.
• Causes: Asbestos exposure, chronic inflammation, or fibrosis.
• Differential Diagnoses: Asbestosis, pleural fibrosis, or chronic inflammation.
• Complications: Risk of mesothelioma, pleural effusion.

Reverse Halo Sign

• Radiologic Findings: Central ground-glass opacity surrounded by denser consolidation.
• CT Imaging Characteristics: Central ground-glass opacity within a ring of consolidation.
• Causes: Organizing pneumonia, cryptogenic organizing pneumonia (COP).
• Differential Diagnoses: Organizing pneumonia, infectious or inflammatory processes.
• Complications: Reflects underlying inflammatory lung pathology.

Signet Ring Sign (Pearl Ring Sign)

• Radiologic Findings: Rounded, lucent space outlined by a thin wall within lung tissue.
• CT Imaging Characteristics: Rounded, ring-shaped opacity within lung tissue.
• Causes: Bronchogenic carcinoma, lung metastasis, or abscess.
• Differential Diagnoses: Bronchogenic carcinoma, metastasis, or abscess.
• Complications: Varies based on the underlying condition.

Split Pleura Sign

• Radiologic Findings: Separation of the pleural layers due to pleural effusion.
• CT Imaging Characteristics: Visible split or separation between pleural layers.
• Causes: Pleural effusion, empyema, or chronic inflammation.
• Differential Diagnoses: Pleural effusion, empyema, or chronic pleural diseases.
• Complications: Reflects underlying pleural pathology.

Headcheese Sign

• Radiologic Findings: Appearance resembling headcheese or sliced ham.
• CT Imaging Characteristics: Mottled, mixed attenuation resembling food slices.
• Causes: Consolidation, hemorrhage, or infection.
• Differential Diagnoses: Consolidation, hemorrhage, or infected lung tissue.
• Complications: Reflects underlying lung pathology.

Thoracoabdominal Sign

• Radiologic Findings: Borders of thoracic and abdominal structures in the same image.
• CT Imaging Characteristics: Visualization of both thoracic and abdominal structures.
• Causes: Anatomical display in imaging sections.
• Differential Diagnoses: N/A, anatomical representation.
• Complications: N/A, anatomical representation in imaging.

Westermark Sign

• Radiologic Findings: Focal oligemia in the lung distal to a pulmonary embolism.
• CT Imaging Characteristics: Focal area of decreased vascularity beyond a pulmonary embolism.
• Causes: Pulmonary embolism, vascular obstruction.
• Differential Diagnoses: Pulmonary embolism, vascular insufficiency.
• Complications: Risk of further embolization, respiratory compromise.

CT Angiogram Sign

• Radiologic Findings: Visualization of contrast-filled pulmonary vasculature.
• CT Imaging Characteristics: Enhanced pulmonary vasculature from contrast administration.
• Causes: Intravenous contrast administration for CT angiogram.
• Differential Diagnoses: N/A, imaging feature post-contrast.
• Complications: N/A, post-contrast imaging characteristic.

Bulging Fissure Sign

• Radiologic Findings: Displacement of a fissure due to a lesion or pathology.
• CT Imaging Characteristics: Fissure deviation or bulging caused by adjacent abnormality.
• Causes: Tumors, consolidations, or effusions causing fissure displacement.
• Differential Diagnoses: Tumors, consolidation, or effusion-related fissure abnormalities.
• Complications: Depends on underlying pathology causing the displacement.

Fleischner Sign

• Radiologic Findings: Increased lucency of the lung caused by pneumothorax.
• CT Imaging Characteristics: Increased radiolucency within the lung parenchyma.
• Causes: Pneumothorax or air within the pleural space.
• Differential Diagnoses: Pneumothorax or other air-containing pleural pathologies.
• Complications: Respiratory compromise, risk of tension pneumothorax.

Comet Tail Sign

• Radiologic Findings: Linear opacity with a comet-tail appearance.
• CT Imaging Characteristics: Linear, tail-like opacities extending from lung nodules or masses.
• Causes: Linear scarring due to fibrosis or bronchovascular bundles.
• Differential Diagnoses: Fibrosis, bronchovascular bundle calcification, or linear scarring.
• Complications: Reflects underlying lung scarring or pathology.

Thymic Sail Sign

• Radiologic Findings: Appearance resembling a sail or triangular thymic shadow.
• CT Imaging Characteristics: Triangular thymic outline on a frontal chest radiograph.
• Causes: Normal thymic outline in pediatric chest X-rays.
• Differential Diagnoses: Normal pediatric thymic appearance.
• Complications: N/A, physiological thymic outline in pediatric imaging.

Positive Bronchus Sign

• Radiologic Findings: Dilated bronchus leading to a focal lesion.
• CT Imaging Characteristics: Enlarged bronchus leading to a lesion or mass.
• Causes: Bronchogenic carcinoma, bronchiectasis, or focal infection.
• Differential Diagnoses: Bronchogenic carcinoma, bronchiectasis, or focal infection.
• Complications: Varies based on the underlying pathology.

Double Density Sign

• Radiologic Findings: Focal area with two distinct densities on imaging.
• CT Imaging Characteristics: Presence of a region showing two different densities.
• Causes: Intraluminal content, pathology causing dual attenuation.
• Differential Diagnoses: Varied, depends on the underlying pathology.
• Complications: Reflects underlying pathologies.

Unilateral Hyperlucent Lung/Hemithorax

• Radiologic Findings: Increased lucency or transparency of one lung or hemithorax.
• CT Imaging Characteristics: One lung or hemithorax appears more radiolucent than the other.
• Causes: Congenital lung hypoplasia, obstructive lung diseases, or vascular compromise.
• Differential Diagnoses: Congenital abnormalities, pneumothorax, or lung collapse.
• Complications: Respiratory compromise, chronic lung diseases.

Opaque Hemithorax with Contralateral vs. Ipsilateral Mediastinal Shift

• Radiologic Findings: Increased opacity of one lung with mediastinal deviation.
• CT Imaging Characteristics: One lung is more opaque, causing mediastinal deviation.
• Causes: Lung collapse, consolidation, or effusion leading to mediastinal shift.
• Differential Diagnoses: Atelectasis, consolidation, or large pleural effusion.
• Complications: Varies based on the underlying pathology.

Cervicothoracic Sign

• Radiologic Findings: Abnormality extending from the neck to the thorax.
• CT Imaging Characteristics: Visual representation of pathology or lesion involving both regions.
• Causes: Varies based on the specific pathology identified.
• Differential Diagnoses: Structural abnormalities, lesions, or diseases involving cervical and thoracic regions.
• Complications: Relies on the underlying cause or condition.

Tapered Margins Sign

• Radiologic Findings: Lesion or abnormality showing gradually diminishing edges.
• CT Imaging Characteristics: The lesion presents with gradually narrowing margins.
• Causes: Chronic scarring, fibrosis, or resolving inflammation.
• Differential Diagnoses: Healing inflammatory processes, resolving infections, or resolving nodules.
• Complications: Reflects the resolution or healing of the underlying condition.

Hilum Overlay Sign

• Radiologic Findings: Overlapping structures involving the hilar region.
• CT Imaging Characteristics: Structures overlapping or obscuring the hilum.
• Causes: Positional or anatomical display in imaging sections.
• Differential Diagnoses: N/A, imaging representation.
• Complications: N/A, imaging representation.

Hilum Convergence Sign

• Radiologic Findings: Medial movement or convergence of bilateral hilar structures.
• CT Imaging Characteristics: Hilar structures appear closer or converged.
• Causes: Positional or anatomical display in imaging sections.
• Differential Diagnoses: N/A, imaging representation.
• Complications: N/A, imaging representation.

Random Nodules

• Radiologic Findings: Multiple nodular opacities scattered randomly within lung fields.
• CT Imaging Characteristics: Scattered, randomly distributed nodular opacities.
• Causes: Various causes like infections, granulomas, or inflammatory processes.
• Differential Diagnoses: Infections, granulomas, sarcoidosis, or inflammatory conditions.
• Complications: Indicative of underlying pathology that needs specific management.

Miliary Nodules

• Radiologic Findings: Numerous small, uniform-sized nodules spread throughout the lung.
• CT Imaging Characteristics: Multiple, uniformly sized nodules resembling millet seeds.
• Causes: Tuberculosis, fungal infections, or metastatic diseases.
• Differential Diagnoses: Tuberculosis, disseminated infections, or metastatic lesions.
• Complications: Respiratory failure, disseminated infections, or metastatic spread.

Interlobular Septal Thickening

• Radiologic Findings: Thickening of connective tissue between secondary pulmonary lobules.
• CT Imaging Characteristics: Thickened lines or septa dividing lobules.
• Causes: Inflammation, fibrosis, or edema involving interlobular septa.
• Differential Diagnoses: Interstitial lung diseases, infections, or edematous states.
• Complications: Progressive fibrosis, chronic respiratory insufficiency.

Intralobular Septal Thickening

• Radiologic Findings: Thickening of connective tissue within pulmonary lobules.
• CT Imaging Characteristics: Thickened lines or septa within lobules.
• Causes: Pulmonary edema, inflammation, or interstitial lung diseases.
• Differential Diagnoses: Interstitial lung diseases, infections, or congestive states.
• Complications: Reflects underlying lung pathology, potential chronicity.

Reticulation

• Radiologic Findings: Net-like or grid-like appearance in the lung parenchyma.
• CT Imaging Characteristics: Appearance of a network or grid pattern.
• Causes: Interstitial fibrosis, scarring, or inflammation.
• Differential Diagnoses: Interstitial lung diseases, fibrosis, or chronic inflammation.
• Complications: Progressive fibrosis, respiratory impairment.

Parenchymal Bands

• Radiologic Findings: Linear opacities running through lung parenchyma.
• CT Imaging Characteristics: Linear densities within the lung tissue.
• Causes: Fibrosis, chronic inflammation, or scarring.
• Differential Diagnoses: Chronic lung diseases, fibrosis, or scarring conditions.
• Complications: Progressive lung damage, respiratory compromise.

Subpleural Bands

• Radiologic Findings: Linear opacities at the lung periphery near the pleura.
• CT Imaging Characteristics: Linear densities along the subpleural area.
• Causes: Chronic inflammation, fibrosis, or scarring at the lung periphery.
• Differential Diagnoses: Chronic lung diseases, pleural-based scarring, or fibrosis.
• Complications: Risk of further fibrosis, respiratory impairment.

Pleural Plaque

• Radiologic Findings: Calcified or fibrotic lesion on the pleura.
• CT Imaging Characteristics: Dense, pleural-based lesions.
• Causes: Asbestos exposure, chronic inflammation, or fibrosis.
• Differential Diagnoses: Asbestosis, pleural fibrosis, or chronic inflammation.
• Complications: Risk of mesothelioma, pleural effusion.

Pleural Pseudoplaque

• Radiologic Findings: False appearance of a pleural plaque due to underlying pathology.
• CT Imaging Characteristics: Misleading, pleural-based appearance resembling a plaque.
• Causes: Chronic inflammation, scarring, or previous infections.
• Differential Diagnoses: Chronic infections, scarring, or inflammatory pleural conditions.
• Complications: Reflects underlying pathology, potential chronicity.

Opaque Hemithorax with Contralateral Mediastinal Shift

• Radiologic Findings: Increased opacity in one hemithorax leading to the shift of mediastinal structures toward the opposite side.
• CT Imaging Characteristics: Increased density in one hemithorax causing mediastinal deviation.
• Causes: Lung collapse, consolidation, or effusion resulting in mediastinal shift.
• Differential Diagnoses: Atelectasis, consolidation, or large pleural effusion.
• Complications: Varies based on the underlying pathology.

Opaque Hemithorax with Ipsilateral Mediastinal Shift

• Radiologic Findings: Increased opacity in one hemithorax leading to the shift of mediastinal structures toward the same side.
• CT Imaging Characteristics: Increased density in one hemithorax causing mediastinal deviation toward the same side.
• Causes: Lung collapse, consolidation, or effusion resulting in mediastinal shift.
• Differential Diagnoses: Atelectasis, consolidation, or large pleural effusion.
• Complications: Varies based on the underlying pathology.

Word First ProgramWord First Program

Title	definition 1
Air Bronchogram	Visualization of air-filled bronchi surrounded by opacified lung tissue, indicating patent airways within a consolidated lung.• CT Imaging Characteristics: Dark bronchi visible within a brighter consolidated lung.• Causes: Consolidation in pneumonia or atelectasis.• Differential Diagnoses: Pneumonia, atelectasis, or bronchiolitis obliterans organizing pneumonia (BOOP).• Complications: Respiratory distress, abscess formation, or sepsis.
Air Bronchogram	Visualization of air-filled bronchi amidst opacified lung tissue.• CT Imaging Characteristics: Darkened bronchi visible against opacified lung parenchyma.• Causes: Presence of air in patent bronchi surrounded by consolidated lung tissue.• Differential Diagnoses: Pneumonia, atelectasis, or bronchiolitis obliterans organizing pneumonia (BOOP).• Complications: Respiratory distress, abscess formation, or sepsis.
Air Crescent Sign	Crescent-shaped lucency adjacent to a lung mass or lesion.• CT Imaging Characteristics: Curved, gas-filled space bordering a mass or cavity.• Causes: Represents an air-filled cavity or space adjacent to a pulmonary mass, often post-trauma or post-surgical resection.• Differential Diagnoses: Aspergilloma, pulmonary infarction, or cavitary lung lesions.• Complications: Risk of rupture or hemorrhage.
Air Trapping	Retention of air in the lungs during expiration, leading to persistent or increased lung density.• CT Imaging Characteristics: Increased lung density on expiration compared to inspiration.• Causes: Obstructive lung diseases like asthma, chronic bronchitis, or bronchiolitis.• Differential Diagnoses: Emphysema, bronchiolitis obliterans, or cystic fibrosis.• Complications: Chronic respiratory failure, recurrent infections.
Alveolar Edema	Filling of alveoli with fluid. CT Imaging Characteristics: Increased lung density due to alveolar filling with fluid. Causes: Cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), or severe pneumonia. Differential Diagnoses: ARDS, interstitial lung diseases, or pneumonia. Complications: Respiratory failure, hypoxemia, or sepsis.
Apical Pleural Cap	Linear opacity at the lung apex adjacent to the pleura.• CT Imaging Characteristics: Thin linear opacity along the lung apex.• Causes: Pleural fibrosis, scarring from previous infection or inflammation.• Differential Diagnoses: Tuberculosis, old granulomatous diseases, or previous pleural effusion.• Complications: Rarely symptomatic, may indicate previous lung pathology.
Aspiration Pneumonia	Lung infiltrates in dependent areas, often affecting the right lower lobe.• CT Imaging Characteristics: Ground glass opacities or consolidations in the posterior lung fields.• Causes: Inhalation of foreign material, liquids, or gastric contents into the lungs.• Differential Diagnoses: Bacterial pneumonia, chemical pneumonitis, or pulmonary edema.• Complications: Lung abscess, empyema, acute respiratory distress syndrome (ARDS), or sepsis.
Atypical Pneumonia	Diffuse, patchy, or interstitial infiltrates affecting multiple lobes, often less well-defined.• CT Imaging Characteristics: Patchy or diffuse opacities with less-defined margins.• Causes: Infections by atypical pathogens like Mycoplasma pneumoniae, Chlamydophila pneumoniae, or Legionella pneumophila.• Differential Diagnoses: Viral pneumonia, bacterial pneumonia, or interstitial lung disease.• Complications: Respiratory failure, pleural effusion, or secondary bacterial infection.
Bacterial Pneumonia	Lobar consolidation, segmental consolidation, or multifocal infiltrates with air bronchograms.• CT Imaging Characteristics: Consolidation with air bronchograms, often lobar or segmental.• Causes: Bacterial infection, commonly Streptococcus pneumoniae.• Differential Diagnoses: Other forms of pneumonia, lung abscess, or neoplasm.• Complications: Abscess formation, pleural effusion, respiratory failure, or sepsis.
Beaded Septum Sign	Multiple nodular thickenings of the interlobular septa.• CT Imaging Characteristics: Multiple, small, nodular thickenings along the interlobular septa.• Causes: Lymphatic dilation, lymphangitis, or sarcoidosis.• Differential Diagnoses: Sarcoidosis, lymphangitis, or lymphatic metastasis.• Complications: Reflects underlying pathology, requires further evaluation.
Bleb and Bulla Radiologic Findings	Air-filled spaces within the lung parenchyma. CT Imaging Characteristics: Thin-walled, well-demarcated air-filled spaces. Causes: Congenital, smoking-related, or traumatic lung parenchymal changes. Differential Diagnoses: Pneumatocele, pneumothorax, or lung cysts. Complications: Spontaneous pneumothorax, infection, or rupture causing tension pneumothorax.
Bronchial Artery to Airway Ratio	Ratio between the bronchial artery and the adjacent airway size. CT Imaging Characteristics: Measurement of the bronchial artery diameter compared to the adjacent bronchus. Causes: Pulmonary arterial hypertension, congenital abnormalities, or chronic lung diseases. Differential Diagnoses: Pulmonary artery enlargement, vascular malformations, or chronic thromboembolic disease. Complications: Pulmonary hypertension, right heart strain, or hemoptysis.
Bronchiectasis	Irreversible dilation and thickening of bronchial walls.• CT Imaging Characteristics: Dilated bronchi with thickened walls, often appearing as tram lines or signet rings.• Causes: Infections, cystic fibrosis, or autoimmune conditions.• Differential Diagnoses: Chronic obstructive pulmonary disease (COPD), chronic bronchitis, or cystic fibrosis.• Complications: Recurrent infections, respiratory failure, hemoptysis.
Bronchiolectasis	Abnormal dilation of bronchioles.• CT Imaging Characteristics: Abnormal widening of small airways.• Causes: Infections, chronic inflammation, or inhalation injuries.• Differential Diagnoses: Bronchiectasis, bronchiolitis obliterans, or chronic bronchitis.• Complications: Recurrent infections, respiratory distress, chronic cough.
Bronchocentric Nodule	Nodule with a central bronchus or airway. CT Imaging Characteristics: Nodule centered around a bronchus or airway. Causes: Infections, granulomas, or neoplastic growths. Differential Diagnoses: Bronchiolitis, inflammatory nodules, or endobronchial tumors. Complications: Airway obstruction, secondary infection, or bronchiectasis.
Bulging Fissure Sign	Displacement of a fissure due to a lesion or pathology.• CT Imaging Characteristics: Fissure deviation or bulging caused by adjacent abnormality.• Causes: Tumors, consolidations, or effusions causing fissure displacement.• Differential Diagnoses: Tumors, consolidation, or effusion-related fissure abnormalities.• Complications: Depends on underlying pathology causing the displacement.
Calcified Nodule	Nodule with calcifications visible on imaging. CT Imaging Characteristics: Nodule with dense, calcified areas. Causes: Granulomas, healed infections, or neoplasms. Differential Diagnoses: Tuberculoma, fungal infections, or benign tumors. Complications: Stability or regression over time; rare complications include calcification-induced inflammation.
Cavitating Lung Mass	Lung mass with a central cavity or lucency. CT Imaging Characteristics: Lesion with a central airspace or cavity. Causes: Infections, necrotic tumors, or abscesses. Differential Diagnoses: Lung abscesses, necrotic neoplasms, or tuberculosis. Complications: Rupture, hemorrhage, or secondary infections.
Cavitating Nodule	Nodule with a cavity or central lucency. CT Imaging Characteristics: Nodule with a central airspace or cavity. Causes: Infections, neoplasms, or abscess formation. Differential Diagnoses: Lung abscesses, necrotic tumors, or tuberculosis. Complications: Rupture, hemorrhage, or secondary infections.
Centrilobular Emphysema	Destruction of the lung tissue, particularly in centrilobular regions. CT Imaging Characteristics: Centrilobular lucencies due to air trapping and dilatation of terminal bronchioles. Causes: Smoking, chronic lung diseases, or genetic predisposition. Differential Diagnoses: Panlobular emphysema, paraseptal emphysema, or bronchiectasis. Complications: Respiratory insufficiency, chronic obstructive pulmonary disease (COPD), or pneumothorax.
Centrilobular Nodule	Small nodules located in the center of secondary pulmonary lobules.• CT Imaging Characteristics: Nodules seen in the center of secondary lobules.• Causes: Infections, granulomatous diseases, or occupational lung diseases.• Differential Diagnoses: Inflammatory diseases, sarcoidosis, or hypersensitivity pneumonitis.• Complications: Progression to diffuse lung disease, fibrosis.
Cephalization	Redistribution of pulmonary blood flow towards the upper lung fields. CT Imaging Characteristics: Increased vascularity in the upper lung zones. Causes: Congestive heart failure, pulmonary hypertension, or chronic lung diseases. Differential Diagnoses: Pulmonary embolism, pulmonary artery stenosis, or interstitial lung disease. Complications: Respiratory distress, pulmonary hypertension, or pulmonary edema.
Cervicothoracic Sign	Abnormality extending from the neck to the thorax.• CT Imaging Characteristics: Visual representation of pathology or lesion involving both regions.• Causes: Varies based on the specific pathology identified.• Differential Diagnoses: Structural abnormalities, lesions, or diseases involving cervical and thoracic regions.• Complications: Relies on the underlying cause or condition.
Cervicothoracic Sign (Tapered Margins Sign)	Tapering or narrowing of the margins of an abnormality.• CT Imaging Characteristics: Convergence or narrowing of lesions at their edges.• Causes: Pleural-based lesions or masses.• Differential Diagnoses: Pulmonary masses, nodules, or infiltrates.• Complications: Dependent on the underlying cause (e.g., malignancy, infection).
Chronic Eosinophilic Pneumonia	Peripheral opacities or consolidations involving multiple lobes.• CT Imaging Characteristics: Peripheral opacities or consolidations with ground glass appearance.• Causes: Unknown etiology, potentially related to immune response or allergic reactions.• Differential Diagnoses: Other interstitial lung diseases, atypical pneumonia, or organizing pneumonia.• Complications: Chronic respiratory insufficiency, progressive fibrosis, or recurrent episodes.
Comet Tail Sign	Linear opacity with a comet-tail appearance.• CT Imaging Characteristics: Linear, tail-like opacities extending from lung nodules or masses.• Causes: Linear scarring due to fibrosis or bronchovascular bundles.• Differential Diagnoses: Fibrosis, bronchovascular bundle calcification, or linear scarring.• Complications: Reflects underlying lung scarring or pathology.
Compressive Atelectasis	Lung collapse due to external compression or mass effect. CT Imaging Characteristics: Collapsed lung with a shift of mediastinal structures toward the affected side. Causes: Tumors, lymphadenopathy, pleural effusion, or pneumothorax. Differential Diagnoses: Mass lesions, pleural diseases, or postoperative changes. Complications: Respiratory distress, hypoxia, or secondary infection.
Consolidation	Dense opacification in the lung tissue, loss of air-filled spaces, often appearing as a homogeneous, white area.• CT Imaging Characteristics: Homogeneous or heterogeneous area of increased attenuation replacing normal air-filled alveoli.• Causes: Pneumonia (bacterial, viral, fungal), aspiration, pulmonary hemorrhage, or edema.• Differential Diagnoses: Pneumonia, lung contusion, atelectasis, or neoplasm.• Complications: Respiratory failure, sepsis, abscess formation.
Continuous Diaphragm Sign	Continuous, smooth diaphragm margin with no visible interruption.• CT Imaging Characteristics: Uninterrupted diaphragmatic contour.• Causes: Indicates absence of intrathoracic pathology affecting the diaphragm or pleura.• Differential Diagnoses: Normal diaphragmatic contour, absence of pathology.• Complications: N/A, as this sign indicates a normal finding.
Crazy Paving	Ground glass opacity with superimposed interlobular septal thickening.• CT Imaging Characteristics: Geometric appearance resembling irregular paving stones.• Causes: Alveolar proteinosis, Pneumocystis pneumonia, or interstitial lung disease.• Differential Diagnoses: Alveolar proteinosis, Pneumocystis pneumonia, or viral pneumonia.• Complications: Progressive respiratory failure, risk of infection.
Deep Sulcus Sign on a Supine Radiograph	Deep costophrenic sulcus seen on supine chest X-ray.• X-ray Imaging Characteristics: Deeper-than-usual angle between the chest wall and diaphragm.• Causes: Pneumothorax or air accumulation in the pleural space in a supine position.• Differential Diagnoses: Tension pneumothorax, pneumomediastinum, or pleural effusion.• Complications: Respiratory compromise, tension pneumothorax.
Diaphragmatic Hernia	Organs herniating through a defect in the diaphragm.• CT Imaging Characteristics: Abdominal organs entering the thoracic cavity through a diaphragmatic defect.• Causes: Congenital defects, trauma, or surgery.• Differential Diagnoses: Hiatal hernia, eventration of the diaphragm.• Complications: Organ strangulation, respiratory compromise, gastrointestinal obstruction.
Double Density Sign	Focal area with two distinct densities on imaging.• CT Imaging Characteristics: Presence of a region showing two different densities.• Causes: Intraluminal content, pathology causing dual attenuation.• Differential Diagnoses: Varied, depends on the underlying pathology.• Complications: Reflects underlying pathologies.
Eggshell Calcification of Lymph Nodes	Calcification outlining the periphery of lymph nodes.• CT Imaging Characteristics: Characterized by thin, calcified rims around lymph nodes.• Causes: Chronic granulomatous diseases, histoplasmosis, or healed infections.• Differential Diagnoses: Tuberculosis, sarcoidosis, or fungal infections.• Complications: Generally benign, may occasionally cause local compression symptoms.
Empyema	Accumulation of pus within the pleural space.• CT Imaging Characteristics: Pleural effusion with low attenuation areas suggestive of pus.• Causes: Bacterial infections, pneumonia, or post-surgical complications.• Differential Diagnoses: Complicated parapneumonic effusion, lung abscess, or hemothorax.• Complications: Sepsis, lung loculations, respiratory failure.
Fallen Lung Sign	Dependent lung lobe presenting lower than usual due to atelectasis or consolidation.• CT Imaging Characteristics: Lower-positioned lung segment due to loss of volume.• Causes: Volume loss in dependent lung segments due to atelectasis or pathology.• Differential Diagnoses: Atelectasis, pleural effusion, or lung collapse.• Complications: Respiratory distress, pneumonia.
Fat Pad Sign or Sandwich Sign	Linear fat opacity near the pleural surface.• CT Imaging Characteristics: Visible linear fat density next to the pleura.• Causes: Displacement or alteration of pleural fat by adjacent pathology.• Differential Diagnoses: Pleural-based masses, nodules, or effusions.• Complications: Indicative of underlying pathology, necessitates further evaluation.
Figure 3 Sign	Triangular-shaped opacity with a right angle.• CT Imaging Characteristics: Abnormality with a distinct angular appearance.• Causes: Abnormalities associated with specific lung pathology.• Differential Diagnoses: Pulmonary infarction, pulmonary embolism, or atypical lung lesions.• Complications: Varies based on underlying condition.
Flat Waist Sign	The waist of the heart appears flat on a frontal chest X-ray.• X-ray Imaging Characteristics: Absence of the typical waist indentation of the heart silhouette.• Causes: Pericardial effusion or enlargement, restrictive pericarditis.• Differential Diagnoses: Pericardial effusion, cardiomegaly, or pericardial thickening.• Complications: Cardiac tamponade, heart failure.
Fleischner Sign	Increased lucency of the lung caused by pneumothorax.• CT Imaging Characteristics: Increased radiolucency within the lung parenchyma.• Causes: Pneumothorax or air within the pleural space.• Differential Diagnoses: Pneumothorax or other air-containing pleural pathologies.• Complications: Respiratory compromise, risk of tension pneumothorax.
Fungal Pneumonia	Nodules, consolidations, or cavitations in miliary or patchy distribution.• CT Imaging Characteristics: Nodules, consolidations, or cavities in various patterns.• Causes: Fungal infections like Aspergillus, Cryptococcus, or Histoplasma.• Differential Diagnoses: Bacterial or viral pneumonia, tuberculosis, or lung cancer.• Complications: Chronic infection, dissemination, or progressive lung damage.
Gloved Finger Sign	Opacity in the pleural space resembling the shape of a gloved finger.• CT Imaging Characteristics: Pleural effusion with finger-like extensions into the lung field.• Causes: Pleural effusion with loculated fluid collections.• Differential Diagnoses: Empyema, complex effusions, or hemothorax.• Complications: Infection, impaired lung expansion.
Golden S Sign	Curvilinear opacities resembling the shape of a “golden S” on a chest X-ray.• X-ray Imaging Characteristics: Opacities forming an S-shaped curve in the lung fields.• Causes: Collapse or mass effect on the left lower lobe bronchus.• Differential Diagnoses: Left lower lobe collapse, mass, or hilar lymphadenopathy.• Complications: Respiratory distress, pneumonia.
Ground Glass Nodule	Nodule with a ground-glass appearance, indicative of partial lung opacification. CT Imaging Characteristics: Hazy opacity with preserved bronchial and vascular margins. Causes: Infections, inflammatory processes, or early neoplastic changes. Differential Diagnoses: Inflammatory nodules, early stage lung cancers, or organizing pneumonia. Complications: Progression to malignancy, metastasis, or bleeding.
Ground Glass Opacity (GGO)	Hazy increased opacity in the lung with preserved bronchial and vascular margins. CT Imaging Characteristics: Non-specific opacity with increased lung density but without obscuration of vessels. Causes: Infections, edema, hemorrhage, or early interstitial lung disease. Differential Diagnoses: Pulmonary edema, early pneumonia, or interstitial lung disease. Complications: Progression to fibrosis, respiratory failure, or secondary infection.
Gynecomastia	Enlargement of the male breast tissue.• CT Imaging Characteristics: Increased breast tissue density in males.• Causes: Hormonal imbalances, medications, liver disease, or genetic conditions.• Differential Diagnoses: Breast cancer in males, pseudogynecomastia.• Complications: Psychological distress, potential underlying conditions.
Hampton’s Hump	Wedge-shaped pleural-based opacities in the lung.• CT Imaging Characteristics: Triangular or wedge-shaped peripheral lung opacities.• Causes: Pulmonary infarction due to embolism or ischemia.• Differential Diagnoses: Pulmonary embolism, pulmonary infarction, or pleural-based mass.• Complications: Risk of recurrent embolism, chronic pulmonary hypertension.
Headcheese Sign	Appearance resembling headcheese or sliced ham.• CT Imaging Characteristics: Mottled, mixed attenuation resembling food slices.• Causes: Consolidation, hemorrhage, or infection.• Differential Diagnoses: Consolidation, hemorrhage, or infected lung tissue.• Complications: Reflects underlying lung pathology.
Heart Failure Equalization	Radiographic findings showing equalization of cardiac chamber sizes. CT Imaging Characteristics: Cardiac chamber size equalization due to elevated left atrial pressure. Causes: Acute heart failure, myocardial infarction, or valvular heart disease. Differential Diagnoses: Cardiac tamponade, constrictive pericarditis, or restrictive cardiomyopathy. Complications: Pulmonary edema, cardiogenic shock, or systemic embolization.
Hiatal Hernia	Protrusion of the stomach through the diaphragmatic esophageal hiatus.• CT Imaging Characteristics: Stomach herniating into the thoracic cavity through the esophageal hiatus.• Causes: Weakness or disruption of the diaphragm, congenital predisposition, or trauma.• Differential Diagnoses: Gastroesophageal reflux disease (GERD), paraesophageal hernia.• Complications: Reflux symptoms, Barrett’s esophagus, volvulus, or incarceration.
Hilum Convergence Sign	Medial movement or convergence of bilateral hilar structures.• CT Imaging Characteristics: Hilar structures appear closer or converged.• Causes: Positional or anatomical display in imaging sections.• Differential Diagnoses: N/A, imaging representation.• Complications: N/A, imaging representation.
Hilum Overlay Sign	Overlapping structures involving the hilar region.• CT Imaging Characteristics: Structures overlapping or obscuring the hilum.• Causes: Positional or anatomical display in imaging sections.• Differential Diagnoses: N/A, imaging representation.• Complications: N/A, imaging representation.
Hilum Overlay Sign and Hilum Convergence Sign	Appearance of hilar structures overlaid on lung lesions.• CT Imaging Characteristics: Hilar structures appearing to overlay or converge with lesions.• Causes: Lesions adjacent to the hila.• Differential Diagnoses: Lung masses, nodules, or lesions adjacent to the hilar structures.• Complications: Dependent on underlying pathology.
Honeycomb Lung	Appearance of cystic airspaces with thick walls, resembling a honeycomb.• CT Imaging Characteristics: Clustered cystic airspaces surrounded by thickened walls in a honeycomb pattern.• Causes: End-stage lung diseases, idiopathic pulmonary fibrosis, or advanced interstitial lung diseases.• Differential Diagnoses: End-stage fibrosis, chronic interstitial lung diseases.• Complications: Severe respiratory distress, limited treatment options.
Honeycombing	Lung parenchyma with clustered, cystic airspaces resembling honeycombs.• CT Imaging Characteristics: Multiple small cystic spaces with thick walls in the lung.• Causes: End-stage lung fibrosis, interstitial lung diseases.• Differential Diagnoses: Idiopathic pulmonary fibrosis, chronic interstitial lung diseases.• Complications: Chronic respiratory failure, increased risk of infections.
Infiltrate	Presence of any abnormal substance (fluid, cells, organisms) within the lung tissue causing an area of increased density.• CT Imaging Characteristics: Non-specific, may appear as hazy or cloudy densities.• Causes: Infections (bacterial, viral, fungal), inflammation, or malignancy.• Differential Diagnoses: Pneumonia, pulmonary edema, atelectasis, or neoplasm.• Complications: Abscess formation, respiratory distress, sepsis.
Interlobular and Intralobular Septal Thickening and Reticulation	Thickening of interlobular and intralobular septa, forming a net-like pattern.• CT Imaging Characteristics: Interconnecting linear opacities resembling a net or mesh.• Causes: Interstitial lung diseases, pulmonary edema, or lymphangitic spread.• Differential Diagnoses: Interstitial lung diseases, lymphangitic carcinomatosis.• Complications: Progressive lung damage, respiratory compromise.
Interlobular Septal Thickening	Thickening of connective tissue between secondary pulmonary lobules. CT Imaging Characteristics: Linear opacifications surrounding the secondary pulmonary lobules. Causes: Infections, interstitial lung diseases, or lymphatic disorders. Differential Diagnoses: Lymphangitic carcinomatosis, pulmonary edema, or sarcoidosis. Complications: Respiratory insufficiency, fibrosis, or chronic lung disease.
Interstitial Edema	Accumulation of fluid within the interstitial space of the lung. CT Imaging Characteristics: Linear or reticular opacities representing fluid accumulation in the interlobular septa. Causes: Cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), or interstitial lung diseases. Differential Diagnoses: Interstitial lung diseases, lymphangitic carcinomatosis, or infectious pneumonias. Complications: Respiratory distress, hypoxemia, or progression to fibrosis.
Juxtaphrenic Peak	Acute angle between the diaphragm and lateral chest wall.• X-ray Imaging Characteristics: Sharp angle formed at the diaphragmatic curvature.• Causes: Partial lung collapse, pleural effusion.• Differential Diagnoses: Pneumothorax, pleural effusion, or lung collapse.• Complications: Respiratory distress, exacerbation of underlying condition.
Kerley B Lines	Short, thin, linear opacities seen at the lung periphery. CT Imaging Characteristics: Short linear opacities perpendicular to the pleural surface. Causes: Interstitial edema, congestive heart failure, or lymphatic obstruction. Differential Diagnoses: Interstitial lung diseases, pulmonary fibrosis, or lymphangitic carcinomatosis. Complications: Progression to fibrosis, respiratory failure, or chronic lung disease.
Klebsiella Pneumonia	Often presents with dense lobar consolidation, cavitation, or abscess formation.• CT Imaging Characteristics: Lobar consolidation, cavitation, or abscess.• Causes: Infection by Klebsiella pneumoniae.• Differential Diagnoses: Bacterial pneumonia, lung abscess, or tuberculosis.• Complications: Abscess formation, septic shock, or pleural effusion.
Loculated Pleural Effusion	Pleural effusion confined within a localized space within the pleural cavity.• CT Imaging Characteristics: Fluid accumulation in a confined area, often encapsulated by fibrinous or fibrous tissue.• Causes: Infections, trauma, or post-surgical scarring.• Differential Diagnoses: Empyema, pleural tumors, or pleural fibrosis.• Complications: Chronic effusion, fibrosis, or need for drainage.
Loculated Pneumothorax	Collection of air trapped in specific areas of the pleural space.• CT Imaging Characteristics: Air accumulation in pockets separated by visceral and parietal pleura.• Causes: Trauma, underlying lung disease, or post-surgical complications.• Differential Diagnoses: Tension pneumothorax, pleural effusion, or bullae.• Complications: Respiratory distress, tension pneumothorax if unrelieved.
Luftsichel Sign	Crescentic lucency adjacent to the heart border on chest X-ray.• X-ray Imaging Characteristics: Curved radiolucency adjacent to the left cardiac border.• Causes: Pericardial effusion displacing the left lower lobe, emphysema.• Differential Diagnoses: Pericardial effusion, emphysema, or pneumothorax.• Complications: Cardiac tamponade, respiratory compromise.
Micronodules	Multiple tiny nodules < 3mm in diameter scattered throughout the lungs. CT Imaging Characteristics: Numerous small, well-defined nodules. Causes: Infections, metastases, or inflammatory diseases. Differential Diagnoses: Metastases, miliary tuberculosis, or sarcoidosis. Complications: Progression to larger lesions, hemorrhage, or fibrosis.
Miliary Tuberculosis	Numerous small pulmonary nodules diffusely scattered throughout the lungs. CT Imaging Characteristics: Multiple small nodules resembling millet seeds spread across the lungs. Causes: Infection by Mycobacterium tuberculosis. Differential Diagnoses: Other miliary infections, fungal infections, or metastatic diseases. Complications: Dissemination, severe systemic illness, or organ failure.
Mixed Nodule	Nodule with areas of both solid and ground-glass opacity. CT Imaging Characteristics: Variable appearance with both solid and ground-glass components. Causes: Mixture of neoplastic, inflammatory, or infectious etiologies. Differential Diagnoses: Atypical infections, inflammatory processes, or mixed histology tumors. Complications: Variable based on underlying cause.
Mosaic Attenuation	Patchy areas of lung with varying attenuation, appearing mosaic-like on imaging.• CT Imaging Characteristics: Areas of high and low attenuation interspersed throughout the lung.• Causes: Air trapping due to small airway diseases, bronchiolitis, or vascular disorders affecting lung perfusion.• Differential Diagnoses: Asthma, bronchiolitis obliterans, or pulmonary embolism.• Complications: Respiratory distress, chronic lung disease progression.
Opaque Hemithorax with Contralateral Mediastinal Shift	Increased opacity in one hemithorax leading to the shift of mediastinal structures toward the opposite side.• CT Imaging Characteristics: Increased density in one hemithorax causing mediastinal deviation.• Causes: Lung collapse, consolidation, or effusion resulting in mediastinal shift.• Differential Diagnoses: Atelectasis, consolidation, or large pleural effusion.• Complications: Varies based on the underlying pathology.
Opaque Hemithorax with Ipsilateral Mediastinal Shift	Increased opacity in one hemithorax leading to the shift of mediastinal structures toward the same side.• CT Imaging Characteristics: Increased density in one hemithorax causing mediastinal deviation toward the same side.• Causes: Lung collapse, consolidation, or effusion resulting in mediastinal shift.• Differential Diagnoses: Atelectasis, consolidation, or large pleural effusion.• Complications: Varies based on the underlying pathology.
Organizing Pneumonia	Peripheral consolidations with a surrounding “halo” of ground-glass opacity. CT Imaging Characteristics: Consolidations with a peri-lesional ground-glass halo. Causes: Inflammatory processes, infections, autoimmune diseases, or exposure to certain medications. Differential Diagnoses: Bacterial/viral pneumonia, malignancy, or organizing pneumonia secondary to collagen vascular disease. Complications: Chronic lung disease, relapses, or progression to fibrosis.
Panlobular Emphysema	Uniform and diffuse destruction of the entire acinus. CT Imaging Characteristics: Homogeneous low-density lung fields without zonal variation. Causes: Alpha-1 antitrypsin deficiency, smoking, or congenital disorders. Differential Diagnoses: Centrilobular emphysema, paraseptal emphysema, or bullous lung disease. Complications: Chronic respiratory failure, hypoxemia, or recurrent infections.
Paraseptal Emphysema	Distal acinar emphysema adjacent to the pleura and interlobular septa. CT Imaging Characteristics: Bullae or cysts adjacent to the pleura and subpleural regions. Causes: Smoking, chronic lung diseases, or genetic predisposition. Differential Diagnoses: Bullous lung diseases, pneumothorax, or congenital lung abnormalities. Complications: Spontaneous pneumothorax, infection of bullae, or respiratory distress.
Parenchymal and Subpleural Bands	Linear opacities extending from the pleura into the lung.• CT Imaging Characteristics: Linear densities along the pleura or within lung tissue.• Causes: Fibrosis, chronic lung disease, or inflammation.• Differential Diagnoses: Chronic lung diseases, fibrosis, or scarring.• Complications: Indicative of underlying chronic lung pathology.
Perilymphatic Nodules	Nodules distributed around lymphatic vessels.• CT Imaging Characteristics: Nodules surrounding lymphatic structures.• Causes: Granulomatous diseases, sarcoidosis, or lymphatic spread.• Differential Diagnoses: Lymphatic metastases, sarcoidosis, or lymphangitic spread.• Complications: Reflects underlying lymphatic pathology, necessitates further evaluation.
Pleural Plaque	Calcified or fibrotic lesion on the pleura.• CT Imaging Characteristics: Dense, pleural-based lesions.• Causes: Asbestos exposure, chronic inflammation, or fibrosis.• Differential Diagnoses: Asbestosis, pleural fibrosis, or chronic inflammation.• Complications: Risk of mesothelioma, pleural effusion.
Pleural Pseudoplaque	False appearance of a pleural plaque due to underlying pathology.• CT Imaging Characteristics: Misleading, pleural-based appearance resembling a plaque.• Causes: Chronic inflammation, scarring, or previous infections.• Differential Diagnoses: Chronic infections, scarring, or inflammatory pleural conditions.• Complications: Reflects underlying pathology, potential chronicity.
Pneumococcal Pneumonia	Lobar or segmental consolidation, sometimes with pleural effusion.• CT Imaging Characteristics: Consolidation, often lobar, and associated with pleural effusion.• Causes: Bacterial infection by Streptococcus pneumoniae.• Differential Diagnoses: Other forms of bacterial pneumonia, lung abscess, or tuberculosis.• Complications: Pleural effusion, empyema, septicemia, or respiratory failure.
Positive Bronchus Sign	Dilated bronchus leading to a focal lesion.• CT Imaging Characteristics: Enlarged bronchus leading to a lesion or mass.• Causes: Bronchogenic carcinoma, bronchiectasis, or focal infection.• Differential Diagnoses: Bronchogenic carcinoma, bronchiectasis, or focal infection.• Complications: Varies based on the underlying pathology.
Post Obstructive Atelectasis	Lung collapse due to obstruction of a bronchus by an intraluminal or extraluminal mass. CT Imaging Characteristics: Collapse of lung segments or lobes. Causes: Tumors, foreign bodies, mucus plugs, or lymphadenopathy. Differential Diagnoses: Bronchial obstruction, pneumonia, or lung fibrosis. Complications: Pneumonia, respiratory failure, or secondary infection.
Pseudopneumothorax	Appearance similar to pneumothorax but without actual lung collapse.• CT Imaging Characteristics: Lack of visceral pleural line disruption.• Causes: Pleural adhesions, misplaced chest tubes, or artifact.• Differential Diagnoses: Pneumothorax, pleural thickening.• Complications: Misinterpretation leading to unnecessary intervention.
Random or Miliary Nodules	Numerous small nodules scattered randomly.• CT Imaging Characteristics: Multiple small nodules distributed evenly throughout the lung.• Causes: Infections like tuberculosis, miliary metastases, or hematogenous spread.• Differential Diagnoses: Miliary tuberculosis, metastases, or fungal infections.• Complications: Respiratory distress, disseminated infection.
Reticular Pattern	Net-like appearance due to interlacing linear opacities.• CT Imaging Characteristics: Mesh-like pattern of linear opacities distributed throughout the lung.• Causes: Interstitial lung diseases, fibrosis, or scarring.• Differential Diagnoses: Idiopathic pulmonary fibrosis, sarcoidosis, or collagen vascular diseases.• Complications: Progressive fibrosis, respiratory failure.
Reverse Halo Sign	Central ground-glass opacity surrounded by denser consolidation.• CT Imaging Characteristics: Central ground-glass opacity within a ring of consolidation.• Causes: Organizing pneumonia, cryptogenic organizing pneumonia (COP).• Differential Diagnoses: Organizing pneumonia, infectious or inflammatory processes.• Complications: Reflects underlying inflammatory lung pathology.
Ring Around the Artery Sign	Circular or ring-shaped opacity surrounding a pulmonary artery.• CT Imaging Characteristics: Opacification encircling a pulmonary artery, often indicating an embolus or mass.• Causes: Pulmonary embolism, tumor encircling vessels.• Differential Diagnoses: Pulmonary artery enlargement, lymphadenopathy, or arteritis.• Complications: Pulmonary infarction, increased risk of thromboembolism.
Round Pneumonia	Rounded and solitary consolidation, commonly seen in children. CT Imaging Characteristics: Well-circumscribed, rounded opacities. Causes: Typically bacterial infections, often Streptococcus pneumoniae. Differential Diagnoses: Abscess, neoplasm, or fungal infections. Complications: Resolution with treatment; complications are rare.
Rounded Atelectasis	Round or oval-shaped areas of atelectasis with a curvilinear opacity (comet tail sign). CT Imaging Characteristics: Pleural-based atelectasis with a comet tail appearance. Causes: Chronic pleural inflammation, asbestos exposure, or scarring. Differential Diagnoses: Lung nodules, pleural masses, or subpleural fibrosis. Complications: Infrequent; usually asymptomatic.
Scimitar Sign	Curved opacity resembling a scimitar sword.• CT Imaging Characteristics: Abnormal vascular appearance, resembling a scimitar’s shape.• Causes: Anomalous pulmonary venous drainage.• Differential Diagnoses: Scimitar syndrome, congenital heart anomalies.• Complications: Risk of pulmonary hypertension, heart failure.
Secondary Lobule	Functional unit of the lung comprising multiple acini supplied by a single bronchiole. CT Imaging Characteristics: Hexagonal-shaped structures with a central bronciole on CT due to the pattern of lung anatomy. Causes: Structural arrangement of the lung’s acinar units. Differential Diagnoses: No pathological conditions associated. Complications: No direct complications associated.
Signet Ring Sign (Pearl Ring Sign)	Rounded, lucent space outlined by a thin wall within lung tissue.• CT Imaging Characteristics: Rounded, ring-shaped opacity within lung tissue.• Causes: Bronchogenic carcinoma, lung metastasis, or abscess.• Differential Diagnoses: Bronchogenic carcinoma, metastasis, or abscess.• Complications: Varies based on the underlying condition.
Silhouette Sign	Loss of border visibility between anatomical structures due to similar radiodensity, caused by adjacent abnormalities.• CT Imaging Characteristics: Visual obscuring of the normal borders of structures.• Causes: Typically seen in lung pathology where the lesion or abnormality affects the silhouette of adjacent structures.• Differential Diagnoses: Pneumonia, mass lesions, or infiltrates adjacent to structures.• Complications: Difficulty in precise localization of lesions or abnormalities.
Simple Pleural Effusion	Accumulation of fluid within the pleural space.• CT Imaging Characteristics: Smooth, even fluid accumulation in the pleural cavity.• Causes: Congestive heart failure, infections, or malignancies.• Differential Diagnoses: Congestive heart failure, pneumonia, or pulmonary embolism.• Complications: May resolve with treatment; if chronic, can lead to fibrosis or recurrence.
Solid Lung Mass	Space-occupying lesion within lung tissue. CT Imaging Characteristics: Well-defined, homogeneous density with no internal lucency. Causes: Neoplasms, infections, or granulomas. Differential Diagnoses: Lung cancers, solitary pulmonary nodules, or inflammatory masses. Complications: Malignancy, metastasis, or compression of nearby structures.
Solid Nodule	Round or oval-shaped opacity in the lung parenchyma. CT Imaging Characteristics: Well-defined, homogenous opacity with a solid appearance. Causes: Neoplastic growths, granulomas, or infections. Differential Diagnoses: Lung cancers, metastases, granulomas, or benign tumors. Complications: Malignant transformation, metastasis, or bleeding.
Spiculated Lung Mass	Lung mass with spiky projections extending from its margins. CT Imaging Characteristics: Irregular margins with spicules extending into the lung. Causes: Malignant tumors, invasive neoplasms, or metastases. Differential Diagnoses: Lung adenocarcinoma, metastases, or inflammatory masses. Complications: Malignancy, metastasis, or growth over time.
Spiculated Nodule	Nodule with lines extending radially outward resembling spicules. CT Imaging Characteristics: Nodule with irregular, spiky borders. Causes: Neoplasms, metastases, or invasive tumors. Differential Diagnoses: Lung cancers, metastases, or inflammatory processes. Complications: Malignancy, metastasis, or growth over time.
Split Pleura Sign	Separation of the pleural layers due to pleural effusion.• CT Imaging Characteristics: Visible split or separation between pleural layers.• Causes: Pleural effusion, empyema, or chronic inflammation.• Differential Diagnoses: Pleural effusion, empyema, or chronic pleural diseases.• Complications: Reflects underlying pleural pathology.
Subpleural Sparing	Preservation of normal lung density at the lung periphery.• CT Imaging Characteristics: Areas of normal lung density adjacent to areas of disease or abnormality.• Causes: Certain lung diseases affecting the peripheral lung preferentially, sparing the subpleural regions.• Differential Diagnoses: Some interstitial lung diseases, organizing pneumonia.• Complications: Dependent on the underlying condition causing the sparing.
Tapered Margins Sign	Lesion or abnormality showing gradually diminishing edges.• CT Imaging Characteristics: The lesion presents with gradually narrowing margins.• Causes: Chronic scarring, fibrosis, or resolving inflammation.• Differential Diagnoses: Healing inflammatory processes, resolving infections, or resolving nodules.• Complications: Reflects the resolution or healing of the underlying condition.
Tension Pneumothorax	Shift of mediastinal structures away from affected lung due to trapped air under pressure.• CT Imaging Characteristics: Collapsed lung, mediastinal shift, compression of contralateral lung.• Causes: Trauma, medical procedures, or underlying lung disease.• Differential Diagnoses: Pneumothorax, massive pleural effusion.• Complications: Cardiac arrest, severe respiratory distress.
Thick-Walled Cysts	Air-filled spaces with thicker walls than thin-walled cysts.• CT Imaging Characteristics: Rounded lucencies in the lung tissue with thicker, more defined walls.• Causes: Chronic infections, bronchiectasis, or inflammatory lung diseases.• Differential Diagnoses: Lung abscesses, cavitating tumors, or complex pneumonias.• Complications: Secondary infections, abscess formation.
Thin-Walled Cysts	Presence of small air-filled spaces within lung parenchyma with thin walls.• CT Imaging Characteristics: Rounded lucencies in the lung tissue with delicate walls.• Causes: Emphysema, Langerhans cell histiocytosis, or lymphangioleiomyomatosis.• Differential Diagnoses: Bullae, cavities, or pneumatoceles.• Complications: Potential for rupture, pneumothorax, or respiratory insufficiency.
Thoracoabdominal Sign	Borders of thoracic and abdominal structures in the same image.• CT Imaging Characteristics: Visualization of both thoracic and abdominal structures.• Causes: Anatomical display in imaging sections.• Differential Diagnoses: N/A, anatomical representation.• Complications: N/A, anatomical representation in imaging.
Thymic Sail Sign	Appearance resembling a sail or triangular thymic shadow.• CT Imaging Characteristics: Triangular thymic outline on a frontal chest radiograph.• Causes: Normal thymic outline in pediatric chest X-rays.• Differential Diagnoses: Normal pediatric thymic appearance.• Complications: N/A, physiological thymic outline in pediatric imaging.
Traction Bronchiectasis	Irregular dilatation of bronchi due to adjacent fibrosis or scarring.• CT Imaging Characteristics: Bronchiectatic changes caused by traction from fibrotic lung tissue.• Causes: Fibrosis, scarring, or chronic lung diseases.• Differential Diagnoses: Idiopathic pulmonary fibrosis, chronic interstitial lung diseases.• Complications: Chronic respiratory failure, recurrent infections.
Traumatic Hernia	Herniation of abdominal organs due to trauma or injury.• CT Imaging Characteristics: Abdominal organ protrusion through a traumatic defect in the abdominal wall.• Causes: Blunt or penetrating trauma to the abdomen, resulting in muscle or fascial defects.• Differential Diagnoses: Diaphragmatic hernia, muscle tears, or abdominal wall defects.• Complications: Bowel obstruction, perforation, or sepsis.
Tree-in-Bud Appearance	Pattern resembling budding tree branches due to impacted small airways.• CT Imaging Characteristics: Multiple centrilobular branching opacities.• Causes: Infections (viral, bacterial), bronchiolitis, or aspiration.• Differential Diagnoses: Bronchiolitis, small airway disease, or mucus plugging.• Complications: Progression to bronchiectasis, recurrent infections.
Viral Pneumonia	Diffuse, patchy, or interstitial infiltrates affecting multiple lobes.• CT Imaging Characteristics: Patchy, ground glass opacities or consolidations.• Causes: Infection by viruses such as influenza, respiratory syncytial virus (RSV), or adenovirus.• Differential Diagnoses: Bacterial pneumonia, atelectasis, or interstitial lung disease.• Complications: Respiratory failure, secondary bacterial infection, or acute respiratory distress syndrome (ARDS).
Westermark Sign	Focal oligemia in the lung distal to a pulmonary embolism.• CT Imaging Characteristics: Focal area of decreased vascularity beyond a pulmonary embolism.• Causes: Pulmonary embolism, vascular obstruction.• Differential Diagnoses: Pulmonary embolism, vascular insufficiency.• Complications: Risk of further embolization, respiratory compromise.
White Out	Complete opacification of the lung fields, obscuring pulmonary vessels and airway structures.• CT Imaging Characteristics: Homogeneous, diffuse opacity in both lungs.• Causes: Severe pneumonia, massive pulmonary edema, or alveolar hemorrhage.• Differential Diagnoses: Acute respiratory distress syndrome (ARDS), massive pulmonary embolism, or diffuse alveolar damage.• Complications: Severe hypoxemia, respiratory failure, and death if not managed promptly.