radiological signs in chest medicine

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  • Gamal Rabie Agmy, MD, FCCP Professor of Chest Diseases, Assiut University
  • Air Bronchogram In a normal chest x-ray, the tracheobronchial tree is not visible beyond the 4th order. As the bronchial tree branches, the cartilaginous rings become thinner, and eventually disappear in respiratory bronchioles. The lumen of the bronchus contains air and the surrounding alveoli contain air. Thus, there is no contrast to visualize the bronchi. The air column in the bronchi beyond the 4th order becomes recognizable if the surrounding alveoli is filled, providing a contrast or if the bronchi get thickened The term air bronchogram is used for the former state and signifies alveolar disease.
  • The sign implies: patency of proximal airways evacuation of alveolar air by absorption (atelectasis), replacement (pneumonia) or combination of both Consolidation, Bronchoalveolar carcinoma, lymphoma
  • Silhouette Sign Adjacent Lobe/SegmentSilhouette RLL/Basal segmentsRight diaphragm RML/Medial segmentRight heart margin RUL/Anterior segmentAscending aorta LUL/Posterior segmentAortic knob Lingula/Inferior segmentLeft heart margin LLL/Superior and basal segmentsDescending aorta LLL/Basal segmentsLeft diaphragm Cardiac margins are clearly seen because there is contrast between the fluid density of the heart and the adjacent air filled alveoli. Both being of fluid density, you cannot visualize the partition of the right and left ventricle because there is no contrast between them. If the adjacent lung is devoid of air, the clarity of the silhouette will be lost. The silhouette sign is extremely useful in localizing lung lesions.
  • Atelectasis Right Lung Homogenous density right hemithorax Mediastinal shift to right Right hemithorax smaller Right heart and diaphragmatic silhouette are not identifiable
  • Atelectasis Left Lung Homogenous density left hemithorax Mediastinal shift to left Left hemithorax smaller Diaphragm and heart silhouette are not identifiable
  • Lateral Movement of oblique and transverse fissures Atelectasis Right Upper Lobe Homogenous density right upper lung field Mediastinal shift to right Loss of silhouette of ascending aorta
  • Atelectasis Left Upper Lobe Hazy density over left upper lung field Loss of left heart silhouette Tracheal shift to left Lateral A: Forward movement of oblique fissure B: Herniated right lung C: Atelectatic LUL
  • Consolidation Right Upper Lobe / Density in right upper lung field Lobar density Loss of ascending aorta silhouette No shift of mediastinum Transverse fissure not significantly shifted Air bronchogram
  • S Curve of Golden When there is a mass adjacent to a fissure, the fissure takes the shape of an "S". The proximal convexity is due to a mass, and the distal concavity is due to atelectasis. Note the shape of the transverse fissure. This example represents a RUL mass with atelectasis
  • Cut Off Sign When you see an abrupt ending of visualized bronchus, it is called a "cut off sign". It indicates an intrabronchial lesion. This is useful to identify the etiology of atelectasis . Be careful as the tracheobronchial tree is three dimensional and the finding need to be confirmed with tomogram. In the modern era, a CT scan will take care of this.
  • Pulmonary Artery Overlay Sign This is the same concept as a silhouette sign. If you can recognize the interlobar pulmonary artery, it means that the mass seen is either in front of or behind it. This is an example of a dissecting aneurysm.
  • AV Fistula Osler-Weber-Rendu Syndrome "Pulmonary nodule" Multiple lesions Feeding vessel Cardiomegaly Patient presented with severe congestive heart failure and severe iron deficiency anemia. Had multiple telangiectasia of tongue, lips and conjunctivae.
  • AV Fistula Osler-Weber-Rendu Syndrome "Pulmonary nodule" Multiple lesions Feeding vessel Cardiomegaly Patient presented with severe congestive heart failure and severe iron deficiency anemia. Had multiple telangiectasia of tongue, lips and conjunctivae.
  • Radiographic Signs of Pneumomediastinum Subcutaneous emphysema Thymic sail sign Pneumoprecardium Ring around the artery sign Tubular artery sign Double bronchial wall sign Continuous diaphragm sign Extrapleural sign Air in the pulmonary ligament
  • Potential Sources of Mediastinal Air Intrathoracic Trachea and major bronchi Esophagus Lung Pleural space Extrathoracic Head and neck Intraperitoneum and retroperitoneum
  • Air Crescent Sign Can be visualized in X-rays and CT Crescentic collection of air within consolidation or nodular opacity Seen in pulmonary cavitary process Usually announces recovery It is a result of increased granulocyte activity
  • Characteristic of invasive pulmonary aspergillosis Tumor, hematoma, Wegener granulomatosis, hydatid cyst, TB, nocardiosis, bacterial abscess Not confused with Monods sign air surrounding fungus ball or mycetoma in preexisting cavity Air Crescent Sign
  • Continuous Diaphragm Sign Described by Levin in 1973 Normally central part of diaphragm is lost due to apposition of heart Air interposed between the heart and diaphragm results in gas-tissue interface Seen on chest radiographs Characteristic of pneumomediastinum
  • Bulging Fissure Sign Consolidation spreading rapidly, causing lobar expansion and bulging of the adjacent fissure inferiorly . Historically Klebsiella pneumoniae involving the right upper lobe . Friedlander pneumonia.
  • Deep Sulcus Sign Seen on radiographs in supine position Characteristic of pneumothorax 30% pneumothoraces are undetected Lucency in lateral costophrenic angle Air collects anteriorly and basally Useful in neonates and ill patients Include lateral costophrenic angles
  • CT angiogram Sign Identification of vessels within an airless portion of lung on contrast- enhanced CT . The vessels are prominently seen against a background of low- attenuation material . Associatedwith: bronchoalveolar cell carcinoma lymphoma infectious pneumonias.
  • Fallen Lung Sign This sign refers to the appearance of the collapsed lung occurring with a fractured bronchus . The bronchial fracture results in the lung to fall away from the hilum, either inferiorly and laterally in an upright patient or posteriorly, as seen on CT in a supine patient. DD: Pneumothorax causes a lung to collapse inward toward the hilum.
  • Ring Around Artery Sign Visualized on lateral chest radiographs Lucency along or surrounding RPA Characteristic of pneumomediastinum Usually is accompanied by other ancillary signs: continuous diaphragm sign Naclerios V sign thymic sail sign
  • Thymic Sail Sign Naclerios V Sign
  • Flat waist Sign This sign refers to flattening of the contours of the aortic knob and adjacent main pulmonary artery . It is seen in severe collapse of the left lower lobe and is caused by leftward displacement and rotation of the heart
  • Finger in Glove Sign Visible on chest radiographs or CT Indicates mucoid impaction within an obstructed bronchus Characterized by branching tubular or fingerlike opacities
  • Finger in Glove Sign Originate from the hilum and are directed peripherally Also seen in cases of dilated bronchi with secretions Distal lung remains aerated by collateral drift through interalveolar pores (pores of Kohn) and Lambert canal
  • Hampton Hump Sign Pulmonary infarction secondary to pulmonary embolism produces an abnormal area of opacification on the chest radiograph, which is always in contact with the pleural surface.
  • Luftsichel Sign German for sickle of air (luft: air sichel: crescent) Paramediastinal lucency due to interposition of lower lobe apex between mediastinum and shrunken upper lobe Occurs more commonly on the left than in the right
  • Halo Sign CT shows nodular consolidation associated with a halo of ground-glass opacity (GGO) in both apices resulting from invasive pulmonary aspergillosis. This halo represents hemorrhage. When seen in leukemic patients, is highly suggestive of the diagnosis of invasive pulmonary aspergillosis.
  • Double Density Sign Indicates left atrial enlargement Occurs when right side of the left atrium pushes into adjacent lung Splaying of the carina Superior displacement of left main stem bronchus on frontal view
  • Double Density Sign Posterior displacement of left main stem bronchus on lateral view Posterior displacement of esophagus on barium study
  • Walking Man Sign
  • Juxtaphrenic Peak Sign This sign refers to a small triangular shadow that obscures the dome of the diaphragm secondaryto upper lobe atelectasis . The shadow is caused by traction on the lower end of the major fissure, the inferior accessory fissure, or the inferior pulmonaryligament.
  • Luftsischel Sign In left upper lobe collapse, the superior segment of the left lower lobe, which is positioned between the aortic arch and the collapsed left upper lobe, is hyperinflated. This aerated segment of left lower lobe is hyperlucent and shaped like a sickle, where it outlines the aortic arch on the frontal chest radiograph. This peri-aortic lucency has been termed the luftsichel sign, derived from the German words luft (air) and sichel (sickle).
  • Doughnut Sign Detect mediastinal adenomegaly Lateral chest radiograph Subcarinal lymphadenopathy Mass posterior to bronchus intermedius and inferior hilar window CT primary modality for detecting mediastinal lymphadenopathy
  • Pulmonary hypertension Normal Lymphadenopathy
  • Cervicothoracic Sign Used to determine location of mediastinal lesion in the upper chest Based on principle that an intrathoracic lesion in direct contact with soft tissues of the neck will not outlined by air Uppermost border of the anterior mediastinum ends at level of clavicles
  • Cervicothoracic Sign Middle and posterior mediastinum extends above the clavicles Mediastinal mass projected superior the level of clavicles must be located either within middle or posterior mediastinum More cephalad the mass extends the most posterior the location
  • Thoracoabdominal Sign Posterior costophrenic sulcus extends more caudally than anterior basilar lung Lesion extends below the dome of diaphragm must be in posterior chest whereas lesion terminates at dome must be anterior Cervicothoracic and thoracoabdominal signs were described by Felson
  • Tapered Margins Sign A lesion in the chest wall, pleura or mediastinum have smooth tapered borders and obtuse angles While parenchymal lesions usually form acute angles
  • Water Bottle Sign
  • Westermark Sign Described by Neils Westermark in 1938 Chest radiograph and CT show increased lucency or hypoattenuation Typically signifies either occlusion of a larger lobar/segmental artery or widespread small vessel occlusion
  • Fleischner Sign Described by Felix Fleischner Enlargement proximal pulmonary arteries on plain film or angiography PA enlargement due to embolus Commonly in the setting of massive PE It has relatively low sensitivity Abrupt tapering of an occluded vessel distally (knuckle sign)
  • Hilum Overlay Sign Described by B. Felson If hilar vessels are sharply delineated it can be assumed that the overlying mass is anterior or posterior If mass inseparable pulmonary arteries structures are adjacent to one another
  • Hilum Convergence Sign Described by B. Felson Used to distinguish between a prominent hilum and an enlarged pulmonary artery If branches of PA converge toward central mass is an enlarged PA If branches of PA converge toward heart rather than mass is a mediastinal tumor
  • CT Halo Sign
  • CT Halo Sign Ground glass attenuation surrounding a pulmonary nodule/mass on CT images Described by Kuhlman in 1985 in patients with invasive aspergillosis Associated w hemorrhagic nodules and may be caused neo or inflammatory Disease pathologically active with tumor spread, hemorrhage or inflammation
  • Reverse Halo Sign Central ground-glass opacity surrounded by denser consolidation of crescentic or ring shape, at least 2 mm thick First described by Voloudaki in 1996 Kim in 2003 used the term reverse halo Found to be relatively specific for crypto- genic organizing pneumonia (COP)
  • Reverse Halo Sign Seen in other conditions: Wegeners granulomatosis lymphomatoid granulomatosis paracoccidiodomycosis neoplastic (metastasis) invasive aspergillosis lipoid pneumonia
  • Split Pleura Sign Seen on contrast enhanced CT of chest Thickened visceral and parietal pleura with separation by a collection Empyema or exudative effusion Exudative: bacterial pneumonia, cancer, viral infection, PE
  • Tree-in-Bud Sign Commonly seen at thin-section CT Initially described in endobronchial spread of Tuberculosis Recognized in diverse entities Small centrilobular nodules soft-tissue attenuation connected to multiple branching structures
  • Tree-in-Bud Sign
  • Crazy Paving Sign Scattered or diffuse GG attenuation w superimposed intralobular and interlobular septa thickening Commonly seen at thin-section CT Initially described in PAP Recognized in diverse entities
  • Crazy Paving Sign
  • Comet Tail Sign Seen on CT of the chest Consists of curvilinear opacity extending from subpleural mass toward hilum Produced by the distortion vessels and bronchi that lead to adjacent rounded atelectasis
  • Signet Ring Sign Seen on CT/HRCT scans of chest CT finding in patient with bronchiectasis Ring shadow representing dilated thick- walled bronchus associated a nodular opacity representing pulmonary artery Distinguish from cystic lung lesions
  • Pearl ring sign