British Journal of Radiology 74 (2001),89-97 © 2001 The British Institute of Radiology
Lobar atelectasis: diagnostic pitfalls on chest radiography
K Ashizawa, MD
1
K Hayashi, MD
1
N Aso, MD
1 and
K Minami, MD
2
1 Department of Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki, 852-8501
2 Department of Radiology, Nagasaki Municipal Hospital, 6-39 Shinchi-machi, Nagasaki, 850-8555, Japan
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Abstract
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This pictorial review looks at the pitfalls in the diagnosis of lobar atelectasis on chest radiographs. Lobar atelectasis with marked volume loss is hard to recognize and may be easily missed. Lobar atelectasis presenting as a mass-like opacity may be misdiagnosed as mediastinal or lung tumour. Lobar atelectasis in an unusual location may also be misdiagnosed as other entities. Familiarity with such manifestations and consideration of anatomical alterations as the signs of lobar atelectasis are important in making the correct diagnosis.
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Introduction
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Diagnosis of lobar atelectasis showing typical radiographic appearances is clear [1–4]. However, when the features of lobar atelectasis are unusual, it may easily be missed or misdiagnosed as other diseases, resulting in a delay in diagnosis and management [1–4]. In this pictorial review, we looked at unusual manifestations of lobar atelectasis on chest radiographs.
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Classification of unusual manifestations of lobar atelectasis
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We classified unusual manifestations of lobar atelectasis into three groups: Group 1: atelectasis with marked volume loss; Group 2: atelectasis presenting as a mass-like opacity; and Group 3: atelectasis in an unusual location.
Group 1: atelectasis with marked volume loss
Most cases of atelectasis in this group are caused by peripheral airway obstruction. This chronic atelectasis without central airway obstruction is referred to as non-obstructive atelectasis. An atelectatic lobe with marked volume loss is small and may be overlooked on plain chest radiographs. When volume loss is marked, however, many anatomical alterations as indirect signs of lobar atelectasis can be identified. It is important to seek these changes to diagnose lobar atelectasis.
Cases of marked lobar atelectasis for each lobe are shown in Figures 1–6
. In marked upper lobe atelectasis, the small and elevated hilum and the disappearance of the upper lobe pulmonary artery are clues for the correct diagnosis (Figures 1 and 2 ). The crescentric lucency between the mediastinum and the atelectatic upper lobe on frontal chest radiographs is called the Luftsichel sign [5]. This sign is more commonly seen in left upper lobe atelectasis than in right upper lobe atelectasis (Figure 2). A peak-like shadow located along the medial half of the hemidiaphragm, called the juxtaphrenic peak, is also seen in some cases of upper lobe atelectasis.
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Figure 1. 68-year-old woman with marked right upper lobe atelectasis due to bronchial tuberculosis. (a) Posteroanterior radiograph showing markedly atelectatic right upper lobe as a band opacity at the right superior mediastinum (arrows). Note the small and elevated right hilum and the decreased vascular markings in the right lung. (b) CT clearly demonstrates the atelectatic right upper lobe as a band opacity (arrows).
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Figure 2. 61-year-old man with marked left upper lobe atelectasis due to a carcinoid tumour in left upper lobe bronchus. (a) Posteroanterior radiograph shows a small left perihilar opacity. The left hilum is elevated and the left upper lobe pulmonary artery is invisible. (b) Anteroposterior scout radiograph on CT shows a radiolucent stripe (arrowheads) between the atelectatic left upper lobe and the aortic arch (Luftsichel sign). (c) CT shows the atelectatic left upper lobe as a triangular opacity with its apex directed posteriorly. The hyperinflated superior segment of the left lower lobe extends medially to the atelectatic lobe (arrow), producing the Luftsichel sign.
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Figure 3. 20-year-old man with marked right lower lobe atelectasis due to bronchiectasis as a result of childhood pulmonary infection. (a) Posteroanterior radiograph. The atelectatic right lower lobe is so small that it can hardly be seen. The right hilum is small, and compensatory overinflation and decreased vascular markings in the right lung are present. Note that the anterior mediastinal triangle has shifted to the right (black and white arrowheads), forming the upper triangle sign. (b) Lateral radiograph. The atelectatic lobe cannot be identified. Note that the right hemidiaphragm is seen throughout. (c) CT shows a small opacity with air bronchogram at the right paravertebral region (arrow).
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Figure 4. 74-year-old man with marked left lower lobe atelectasis due to bronchiectasis. (a) Posteroanterior radiograph shows a small hilum on the left and decreased vascular markings in the left lung. Lateral margin of the atelectatic left lower lobe can easily be mistaken for the descending aortic interface (arrowheads). (b) CT demonstrates a markedly atelectatic left lower lobe as a small opacity with air bronchogram in the left paravertebral region.
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Figure 5. 52-year-old woman with marked left lower lobe and right middle lobe atelectasis with bronchiectasis. (a) Posteroanterior radiograph shows obliteration of the right cardiac border (the silhouette sign). Although the left hilum is small and the vascular markings in the left lung are decreased, it is difficult to detect the atelectatic left lower lobe. (b) Lateral radiograph shows the atelectatic right middle lobe as an oblique linear opacity. The atelectatic left lower lobe is not identified. The left hemidiaphragm is seen throughout. (c) CT demonstrates the right middle lobe atelectasis as a triangular opacity with air bronchogram. Marked left lower lobe atelectasis is seen at the left paravertebral region.
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Figure 6. 22-year-old man with marked right middle lobe atelectasis due to bronchiectasis. (a) Posteroanterior (PA) radiograph shows obliteration of the right cardiac border, but the finding is rather subtle. (b) Lateral radiograph shows a thin linear opacity (arrowheads). The diagnosis of right middle lobe atelectasis cannot be clearly made from PA and lateral views. (c) Apical lordotic radiograph demonstrates the atelectatic right middle lobe as a triangular opacity. Note the air bronchogram within the atelectatic lobe, indicating non-obstructive atelectasis.
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In lower lobe atelectasis, inferior displacement of the small hilum and the disappearance of the descending branch of the pulmonary artery are characteristic features (Figures 3–5
). Shift of the anterior mediastinal structures to the right, referred to as "the upper triangle sign" [6], is occasionally seen in right lower lobe atelectasis (Figure 3). In marked atelectasis of the lower lobe, the hemidiaphragm is seen throughout its length (no silhouette sign) on the lateral chest radiograph because of compensatory overinflation of the upper and middle lobe (Figures 3 and 4).
Anatomical alterations are infrequently present in right middle lobe atelectasis because of the smaller volume of the right middle lobe compared with the other lobes (Figures 5 and 6). In severe atelectasis, the frontal chest radiograph may be normal and the apical lordotic view characteristically demonstrates a wedge with its apex directed away from the hilum (Figure 6).
Group 2: atelectasis presenting as a mass-like opacity
Lobar atelectasis sometimes presents as a mass-like opacity with a sharp lateral margin on the chest radiograph (Figures 7–10), and may be misdiagnosed as a mediastinal or lung tumour. To avoid this, it is important to appreciate anatomical alterations as the key radiographic findings. CT is useful in differentiating atelectasis from mediastinal or lung tumours. In some cases, bronchiectasis containing mucus within the atelectatic lobe is clearly demonstrated on contrast enhanced CT (Figures 8 and 9). Combined right middle lobe and right lower lobe atelectasis can be confused with cardiac enlargement and with simple elevation of the right hemidiaphragm.
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Figure 7. 46-year-old man with right upper lobe atelectasis due to adenocarcinoma arising from the right upper lobe bronchus. (a) Posteroanterior radiograph shows a large opacity with a sharp lateral margin. Since the trachea is slightly displaced to the left, a mediastinal mass may be considered. Note elevation of the right hemidiaphragm. (b) CT demonstrates the atelectatic right upper lobe adjacent to the mediastinum. The right main bronchus is stenotic due to tumour invasion.
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Figure 8. 40-year-old woman with combined right middle and lower lobe atelectasis due to bronchial tuberculosis. (a) Posteroanterior radiograph shows a mass-like opacity with a convex lateral margin. A thymoma was suspected as the patient had been suffering from myasthenia gravis. (b) CT clearly demonstrates atelectatic right middle lobe (arrow) and right lower lobe (arrowhead) with dilated bronchi containing mucus. Bronchial tuberculosis was confirmed at right middle and lower lobe.
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Figure 9. 61-year-old woman with combined right middle and lower lobe atelectasis due to bronchial tuberculosis. (a) Posteroanterior radiograph shows a mass-like opacity with a sharp margin lateral to the right cardiac border (arrow). The right hilum is small and inferiorly displaced. (b) CT clearly demonstrates marked atelectasis of the right middle lobe (arrow) and right lower lobe (arrowhead) with dilated bronchi containing mucus.
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Figure 10. 70-year-old man with right upper lobe atelectasis associated with lung torsion due to squamous cell carcinoma. (a) Posteroanterior radiograph shows a mass-like opacity with sharp lateral margin overlying the right hilum. (b) Anterior location and sharp outer margin of the atelectatic lobe are demonstrated on the lateral radiograph. (c) Note that the atelectatic lobe migrates with change in the patient's position, as seen on CT scout view. (d) The atelectatic right upper lobe is located posteriorly on axial CT in the supine position. (Courtesy of Yasuyuki Kurihara, MD, St Marianna University, School of Medicine, Kawasaki-shi, Japan.)
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Group 3: atelectasis in an unusual location
The lower lobe is generally tethered to the mediastinum and the hemidiaphragm by the inferior pulmonary ligament. In contrast, the upper lobe and right middle lobe are incompletely fixed. The atelectatic upper lobe and right middle lobe are therefore often mobile, resulting in an unusual location. This appearance may be misdiagnosed as other diseases. Representative cases of this group include atelectasis with lung torsion (Figure 10), right middle lobe atelectasis in the tipped up (Figure 11) or tipped down position, and atypical peripheral upper lobe atelectasis (Figure 12).
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Figure 11. 78-year-old man with right middle lobe atelectasis. Anteroposterior radiograph shows right middle lobe atelectasis in the tipped up position. The atelectatic lobe swings forward and lies horizontally. This appearance is similar to the configuration of right middle lobe atelectasis on the apical lordotic view (Figure 6c).
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Figure 12. 73-year-old man with peripheral left upper lobe atelectasis due to squamous cell carcinoma. Posteroanterior radiograph shows the pleural-based opacity over the left apex mimicking a pleural/extrapleural mass or pleural effusion (arrowheads).
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Heavy atelectatic lobes, whether filled with fluid, chronic pneumonia or tumour, may migrate with a change in the patient's position [2]. Unless radiographic signs of atelectasis are recognized, the atelectatic lobe may be mistaken for a mediastinal tumour (Figure 10). This condition has been termed "lobar torsion" [7], and should be considered when an atelectatic lobe has shifted from its usual to an atypical location (Figure 10).
The atelectatic middle lobe is very mobile and easily displaced because the right middle lobe bronchus is the narrowest and longest of the lobar bronchi. This atelectatic lobe may swing forward to a tipped up position or may be displaced posteriorly into a tipped down position. In the tipped up position, the atelectatic lobe lies horizontally and the frontal chest radiograph shows it to have a configuration usually seen on apical lordotic views (Figure 11).
Atypical (peripheral) upper lobe atelectasis occurs most frequently in children and most commonly involves the right lung. The radiographic findings of this type of atelectasis may easily be mistaken for a pleural mass or effusion (Figure 12). Recognition of this unusual pattern of upper lobe atelectasis is important to avoid unnecessary diagnostic biopsy or thoracentesis.
Lobar atelectasis may cause pneumothorax. Localized pneumothorax adjacent to an atelectatic lobe is described as a sign of bronchial obstruction (Figure 13) [8] and has been termed "pneumothorax ex vacuo". Treatment should be directed to the underlying bronchus and not the pleural space. For appropriate treatment, it is important to differentiate this condition from pneumothorax-induced atelectasis.
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Figure 13. 7-year-old girl with right upper lobe atelectasis associated with localized pneumothorax. The patient had congenital hypertrophic cardiomyopathy. Anteroposterior radiograph shows a localized pneumothorax adjacent to the atelectatic right upper lobe, "pneumothorax ex vacuo". Note that the pneumothorax is bounded by the outline of the atelectatic upper lobe (arrowheads).
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Acknowledgments
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We are grateful to Michiko Takao, MD, Nagasaki Red Cross Hospital, Nagasaki, Japan, and to Masakazu Mori, MD, National Nagasaki Chuo Hospital, Omura-shi, Japan, for supplying valuable clinical cases.
Received for publication January 4, 2000.
Accepted for publication May 4, 2000.
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References
|
|---|
-
Fraser RG, Pare JAP. Diagnosis of diseases of the chest (3rd edn). Philadelphia, PA: WB Saunders, 1988:494–537.
-
Heitzman ER, The lung: radiologic–pathologic correlation (2nd edn). St Louis: Mosby, 1984:457–501.
-
Felson B, Chest roentgenology. Philadelphia, PA: WB Saunders, 1973:92–124.
-
Proto AV, Tocino I. Radiographic manifestations of lobar collapse. Semin Roentgenol 1980;15:117–73.[Medline]
-
Webber M, Davies P. The Luftsichel: an old sign in upper lobe collapse. Clin Radiol 1981;32:271–5.[Medline]
-
Kattan KR, Felson B, Holder LE, Eyler WR. Superior mediastinal shift in right-lower-lobe collapse. The "upper triangle sign". Radiology 1975;116:305–9.[Abstract]
-
Meisell R. Case of the spring season. Semin Roentgenol 1980;15:115–6.[Medline]
-
Berdon WE, Dee GJ, Abramson SJ, Altman RP, Wung JT. Localized pneumothorax adjacent to a collapsed lobe: a sign of bronchial obstruction. Radiology 1984;150:691–4.[Abstract/Free Full Text]
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Authors' reply
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Abstract
Introduction
