2Atelectasis: Collapse or loss of lung volume May involve entire lung, a lobe, a segment, or be subsegmentalThere are 5 mechanisms of atelectasis:1) (Post) obstructive2-5) Non-obstructive – typically due to loss of contact between parietal and visceral pleura.This presentation will cover the 5 mechanisms of atelectasis, as well as radiographic findings of collapse in all 5 lung lobes.
3Atelectasis Does Not Cause Fever In a 1995 study of 100 postoperative cardiac surgery patients receiving daily portable chest x-rays, “no association could be found between fever and amount of atelectasis. This contradicts common textbook dogma but agrees with previous human study and animal experiments.”Engoren, Milo. “Lack of Association Between Atelectasis and Fever.” Chest. Volume 107(1) January 1995 pp 81-84A 1988 study of 270 patients after elective intra-abdominal surgery found that “neither the presence nor the absence of fever can assure clinicians of the presence or absence of a postoperative pathologic pulmonary complication such as atelectasis.” Roberts J, Barnes W, Pennock M, Browne GD. “Diagnostic Accuracy of Fever as a Measure of Postoperative Pulmonary Complications.” Heart Lung Mar;17(2):166-70
4CXR Findings in Atelectasis Direct:Displacement of fissuresIncreased opacification of airless lobeCrowded air bronchograms (non-obstructive only) or vesselsIndirect:Displacement of hilar structuresIpsilateral cardiomediastinal shiftNarrowing of ipsilateral intercostal spacesObscured structures adjacent to atelectasisElevation of ipsilateral diaphragmatic leafletHyperexpansion/hyperlucency of remaining aerated lung
5Typical findings of atelectasis in this patient include: 1) Hazy opacity in left upper lung (direct sign)2) Left tracheal shift (indirect sign)3) Loss of left cardiac silhouette (indirect sign)
11Right Upper Lobe Atelectasis Findings include:Elevation of right hilum and minor fissureCollapsed lobe shifts cephalad and mediallyIf due to a central mass, the minor fissure retracts cranially with a lateral upward convexity and a medial caudal convexity (S-sign of Golden). This suggests neoplastic etiology.
12Right upper lobe atelectasis: The atelectatic RUL forms a triangular opacity (arrow). The elevated minor fissure is retracted cranially (see image below) and forms a reverse S shape (S-sign of Golden) as it curves around the hilar mass (M).
13Right Middle Lobe Atelectasis Right middle lobe is only 10% of total lung volume.Greater tendency to collapse than other lobes.Radiographic findings can be subtle:Small triangular opacity pointing laterallyObscured right heart borderLateral view: obliquely oriented triangular opacity with apex pointed toward hilum.
14Right middle lobe atelectasis: There is a small triangular opacity pointing laterally, right cardiac border is partially obscured, and slightly lower lung volume in right compared to left.
15Lateral view:The arrows point to the major and minor fissures which are parallel to each other. The atelectatic middle lobe is the opacity between the fissures. Notice that it projects over the cardiac silhouette.
16Right Lower Lobe Atelectasis When atelectatic, right lower lobe retracts posteromedially and inferiorly.Major fissure is shifted downward and becomes visibleAs RLL collapses, it forms a triangular opacity which obscures the left lobe pulmonary artery, and eventually forms a right paraspinal mass that projects behind the right atrium.On lateral view, posterior 1/3 of right diaphragm is obscured by collapsed RLL. Diaphragm may not be obscured on frontal view because hyperexpanded middle lobe abuts it.
17RLL Atelectasis:Triangular opacity in right lower hemithorax. The lateral border is the major fissure (not normally seen on frontal view). Right hilum is displaced caudally and partially obscured. The hyperexpanded RML outlines the cardiac border and right hemidiaphragm.
18Left Upper Lobe Atelectasis Faint, hazy opacity in left upper hemithorax50% of patients have complete major fissureMain pulmonary trunk and upper contour of left pulmonary artery are obliteratedLeft hilar structures and left lower lobe are retracted caudally (look for superior segment vessels from the lower lobe occupying the apex, mimicking an aerated upper lobe)50% have an incomplete major fissureTongue of aerated lower lobe is pulled forward by atelectatic lobe, between the atelectasis and the aortic arch, forming a crescent-shaped lucency (Luftsichel sign)Diaphragm typically elevated
19Left upper lobe atelectasis: Opacity contiguous to the aortic arch Left upper lobe atelectasis: Opacity contiguous to the aortic arch. The mediastinum is shifted toward the left hemithorax, which is small in comparison to the right. The main pulmonary trunk and the left pulmonary artery are obliterated.
20Left upper lobe atelectasis in patient with incomplete major fissure: There is an ill-defined opacity in the left half of the left upper thorax. The trachea is deviated left and the left hilum is retracted superiorly. Vascular branches to the left lower lobe superior segment form an array of linear and tubular opacities. The arrow shows a vertical lucency separating the aortic arch from the vertical margin of the collapsed lobe (Luftsichel).
21Left Lower Lobe Atelectasis Common after cardiac surgeryRadiographic findings include:Increased retrocardiac opacityObscuring of the left lower lobe vessels and left hemidiaphragmCaudal displacement of left hilumLevorotation of cardiac silhouette with flattening of cardiac waistMediastinal shift can cause partial obliteration of aortic arch
22LLL Atelectasis:Notice the wedge shaped opacity behind the cardiac silhouette. The border is formed by the major fissure (arrow). The left hilum is partially obscured and displaced caudally. The left upper lobe is hyperexpanded accounting for the increased lucency in the left hemithorax.
23Complete Atelectasis of Entire Lung Total collapse of a lungComplete opacification of an entire hemithoraxIpsilateral cardiomediastinal shift (in massive pleural effusion, would shift to contralateral side).Cardiac silhouette, one hemidiaphragm, and one hilum are obscured in lateral projection.
24Complete left lung atelectasis: There is mediastinal displacement, opacification, and loss of volume in the left hemithorax. The cardiac silhouette (which is shifted left) is obscured, as are the left hilum and left hemidiaphragm.
26Obstructive (Resorptive) Atelectasis Most common typeResults from blockage of airwaymucous plugging, foreign body, neoplasm, or inflammatory debrisAir distal to obstruction is resorbed from nonventilated alveoliFindings include loss of lung volume without presence of air bronchograms
27Post-obstructive atelectasis of RLL: The major fissure is visible as it has rotated into view. There are no air bronchograms seen within the atelectatic region of lung. The patient is intubated. The obstruction is likely due to mucous plugging.
28Non-obstructive Atelectasis 1) Passive2) Compressive3) Cicatrization4) AdhesiveIn these forms of atelectasis secretions are able drain up the bronchial tree. Because there is no obstruction, bronchoscopy is not therapeutic.
29Passive (Relaxation) Atelectasis 2nd most common form of atelectasisContact between parietal and visceral pleura is lost due to pleural effusion or pneumothorax.Leads to generalized collapse.
30Passive atelectasis: Notice the crowded air bronchograms (arrows) in the setting of a left pleural effusion. Air bronchograms are not present in post-obstructive atelectasis.
31Compressive Atelectasis Due to external compression of lungMay be caused by loculated collection of pleural fluid or by masses in chest wall, pleura, or parenchyma.Similar to relaxation atelectasis but collapse is local rather than generalized.
32Compressive atelectasis: Chest x-ray showing a giant bulla occupying more than two thirds of the right hemithorax and compressing the underlying lung upward and toward the mediastinum. Crowded air bronchograms can be seen (arrows).
33Adhesive AtelectasisCaused by adherence of the alveolar wall surfaces in the setting of surfactant deficiency (e.g., hyaline membrane disease)Surfactant has phospholipid dipalmitoyl phosphatidylcholine, which prevents lung collapse by reducing the surface tension of the alveoliLack of surfactant or inactive surfactant cause alveolar instability and collapse
34Adhesive atelectasis in infant with hyaline membrane disease: CXR reveals bilateral ground-glass appearance of the lungs (atelectasis) and air bronchograms standing (red arrow) out against the collapsed parenchyma.
35Cicatrization Atelectasis Secondary to fibrosis (scarring) of lung parenchyma with subseqent lack of expansionEtiologies include granulomatous disease (often occurs in sarcoid, fungal, and chronic TB), necrotizing pneumonia, and radiation.
36Cicatrization atelectasis: Lung destruction in patient with chronic pulmonary tuberculosis.
37References:1) Sharma, Sat. “Atelectasis.” e-medicine,2) Brad H. Thompson, M.D., William J. Lee, B.S., Jeffrey R. Galvin, M.D. and Jeffrey S. Wilson, M.D “Lobar Anatomy” ElectricLungAnatomy3) Daffner, RH. Clinical Radiology – The Essentials. Williams and Wilkins, 1993, pp4) Engoren, Milo. “Lack of Association Between Atelectasis and Fever.” Chest. Volume 107(1) January 1995 pp 81-845) Roberts J, Barnes W, Pennock M, Browne GD. “Diagnostic Accuracy of Fever as a Measure of Postoperative Pulmonary Complications.” Heart Lung Mar;17(2):166-706) Stark, Paul. “Atelectasis: Types and Pathogenesis.” UpToDate, 2004.7) Stark, Paul. “Radiologic Patterns of Lobar Atelectasis.” UpToDate, 2004.8) Weed HG, Baddour LM. “Postoperative Fever.” UpToDate, 2004.9) Federico Venuta and Tiziano de Giacomo. “Giant Bullous Emphysema.” CTSNET Experts' Techniques, General Thoracic Experts' Techniques.