Radiologic patterns of lobar atelectasis
- Paul Stark, MD
Paul Stark, MD
- Professor of Radiology
- University of California San Diego
- Section Editor
- Nestor L Muller, MD, PhD
Nestor L Muller, MD, PhD
- Section Editor — Pulmonary Imaging
- Professor of Radiology
- University of British Columbia
- Deputy Editors
- Geraldine Finlay, MD
Geraldine Finlay, MD
- Deputy Editor — Pulmonary, Critical Care, and Sleep Medicine
- Associate Professor
- Tufts University School of Medicine
- Susanna I Lee, MD, PhD
Susanna I Lee, MD, PhD
- Deputy Editor — Radiology
- Associate Professor of Radiology
- Harvard Medical School
- Massachusetts General Hospital
Atelectasis describes the loss of lung volume due to the collapse of lung tissue. Radiologic findings characteristic of atelectasis are reviewed here. The appearance of atelectasis on a chest radiograph is emphasized, but its appearance on computed tomography (CT) is also described. The types and pathogenesis of atelectasis are discussed separately. (See "Atelectasis: Types and pathogenesis in adults".)
Radiologic signs of lobar atelectasis can be categorized as direct or indirect [1-5]. Direct signs include increased opacification of the airless lobe and displacement of fissures. Indirect signs include displacement of hilar and cardiomediastinal structures toward the side of collapse, narrowing of the ipsilateral intercostal spaces, elevation of the ipsilateral hemidiaphragm, compensatory hyperinflation and hyperlucency of the remaining aerated lung, and obscuration or desilhouetting of the structures adjacent to the collapsed lung (eg, diaphragm and heart borders). Additional radiologic features vary according to the site of atelectasis.
Right upper lobe — In right upper lobe atelectasis, the collapsed lobe tends to shift cephalad and medially, producing a triangular apical opacity on the frontal view of a chest radiograph (image 1). The opacity may be subtle when the right upper lobe is completely collapsed (especially if chronic), forming only a thin right apical cap. These findings are accompanied by elevation of the right hilum and the minor fissure, with the latter displaying a convex contour cranially . A juxtaphrenic peak (ie, a steeple-shaped shadow adjacent to the diaphragm) may also be present (image 2) . This finding is due to tenting of the ipsilateral diaphragmatic pleura at either the base of the inferior accessory fissure or, less likely, at the insertion site of the inferior pulmonary ligament.
These radiologic findings are different depending upon the orientation and shift of the upper lobe collapse. Medial collapse of the right upper lobe may mimic a right paratracheal mass on the frontal view of a chest radiograph. In contrast, lateral collapse, also called peripheral atelectasis, may generate a peripheral mass-like opacity that mimics a loculated pleural effusion (image 3) [7,8]. This is generally accompanied by superior and medial hyperexpansion of the right middle and right lower lobe.
When right upper lobe atelectasis is due to a central mass with or without an enlarged interlobar lymph node, the minor fissure may have a lateral upward convexity and a medial caudal convexity (similar to the inverted letter S) on the frontal view of a chest radiograph (image 1). This configuration of the minor fissure is called the inverted S-sign of Golden and is suggestive of a neoplastic etiology causing atelectasis of the right upper lobe.
- LUBERT M, KRAUSE GR. Patterns of lobar collapse as observed radiographically. Radiology 1951; 56:165.
- Proto AV, Tocino I. Radiographic manifestations of lobar collapse. Semin Roentgenol 1980; 15:117.
- Proto AV. Lobar collapse: basic concepts. Eur J Radiol 1996; 23:9.
- Woodring JH, Reed JC. Radiographic manifestations of lobar atelectasis. J Thorac Imaging 1996; 11:109.
- Ashizawa K, Hayashi K, Aso N, Minami K. Lobar atelectasis: diagnostic pitfalls on chest radiography. Br J Radiol 2001; 74:89.
- Kattan KR, Eyler WR, Felson B. The juxtaphrenic peak in upper lobe collapse. Semin Roentgenol 1980; 15:187.
- Franken EA Jr, Klatte EC. Atypical (peripheral) upper lobe collapse. Ann Radiol (Paris) 1977; 20:87.
- Don C, Desmarais R. Peripheral upper lobe collapse in adults. Radiology 1989; 170:657.
- Raasch, BN, Heitzman, ER, Carsky, EW, et al. Computed tomographic study of bronchopulmonary collapse. Radiographics 1984; 4:195.
- Kattan KR, Felson B, Holder LE, Eyler WR. Superior mediastinal shift in right-lower-lobe collapse: the "upper triangle sign". Radiology 1975; 116:305.
- Lee, P, Stark, P. Right middle lobe atelectasis following right upper lobe resection in the immediate postoperative period. Clin Intensive Care 2001; 12:173.
- Gudbjartsson T, Gudmundsson G. Middle lobe syndrome: a review of clinicopathological features, diagnosis and treatment. Respiration 2012; 84:80.
- Stark P, Leung A. Effects of lobar atelectasis on the distribution of pleural effusion and pneumothorax. J Thorac Imaging 1996; 11:145.
- Webber M, Davies P. The Luftsichel: an old sign in upper lobe collapse. Clin Radiol 1981; 32:271.
- Blankenbaker DG. The luftsichel sign. Radiology 1998; 208:319.
- Kattan KR, Wlot JF. Cardiac rotation in left lower lobe collapse. "The flat waist sign". Radiology 1976; 118:275.
- Nordenstrom, B, Novek, J. The atelectatic complex of the left lung. Acta Radiol 1960; 53:177.
- Price J. Linear atelectasis in the lingula as a diagnostic feature of left lower lobe collapse: Nordenström's sign. Australas Radiol 1991; 35:56.
- Kottler, NE, Stark P, Levin DL. The challenge of combined lobar atelectasis. Contemp Diagnostic Radiol 2004; 27:1.
- Lee KS, Logan PM, Primack SL, Müller NL. Combined lobar atelectasis of the right lung: imaging findings. AJR Am J Roentgenol 1994; 163:43.
- Gurney JW. Atypical manifestations of pulmonary atelectasis. J Thorac Imaging 1996; 11:165.
- Westcott JL, Cole S. Plate atelectasis. Radiology 1985; 155:1.
- Stark P. Round atelectasis: another pulmonary pseudotumor. Am Rev Respir Dis 1982; 125:248.
- Partap VA. The comet tail sign. Radiology 1999; 213:553.
- Hanke R, Kretzschmar R. Round atelectasis. Semin Roentgenol 1980; 15:174.
- Stathopoulos GT, Karamessini MT, Sotiriadi AE, Pastromas VG. Rounded atelectasis of the lung. Respir Med 2005; 99:615.
- LOBAR ATELECTASIS
- Right upper lobe
- Right middle lobe
- Right lower lobe
- Left upper lobe
- Left lower lobe
- MULTILOBAR ATELECTASIS
- Right middle and lower lobes
- Right upper and middle lobes
- Right upper and lower lobes
- ATELECTASIS OF AN ENTIRE LUNG
- SEGMENTAL ATELECTASIS
- Plate-like atelectasis
- Rounded atelectasis
- SUMMARY AND RECOMMENDATIONS