Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Round atelectasis
- Radiologic Findings
- Chest PA shows ill-defined opacity in right mid and lower lung zone, with small amount of right pleural effusion.
Lung setting image of the chest CT shows small ovoid shaped mass in the subpleural portion of right lower lobe of the lung. Bronchovascular bundles converge into the mass in a curvilinear way, forming whirling appearance or comet tail sign. Mediastinal setting image of chest CT Fig 3) shows homogeneous enhancement of the subpleural mass. Irregular pleural thickening of right lower thorax is present with volume loss of right lower lung, including adjacent area of the mass. Follow up CT showed no difference from the initial CT.
- Brief Review
- Round atelectasis is an unusual form of lung collapse that is adjacent to the pleura. This may simulate pulmonary neoplasm and often associated with asbestosis. The mechanism of round atelectasis is controversial and two main theories are suggested; pleural thickening and pleural effusion. Pleural effusion associated with asbestosis, tuberculosis, other infection, pulmonary infarction or uremic pleuritis may cause infolding of visceral pleura and curling of the adjacent lung in concentric fashion. Fibrous adhesions suspend and lead to additional distortion of the lung parenchyma. Another theory explains that pleural thickening and contraction may lead to shrinkage of the adjacent lung and develops into a round configuration.
The radiographic features of round atelectasis are characteristic; round or oval subpleural opacity, forming acute angle with pleura and commonly found in the posterior lower lungs. Adjacent pleural thickening is essential. Usually it presents as a single lesion, however multiple lesions may occur.
CT findings of round atelectasis is similar as radiography findings; peripherally located round or oval mass with thickening of adjacent pleura. The characteristic CT feature is crowded and distorted bronchovascular bundles which converge and enter the mass, called as comet tail sign. Homogeneous enhancement is seen in contrast enhanced scans, and air-bronchogram may be seen within the mass. Overlying pleural thickening is well demonstrated.
The main differential diagnosis is bronchogenic carcinoma. The round atelectasis is usually stable, but may show very slow growing or spontaneous resolution. Confident diagnosis could be made by CT and no specific treatment is needed.
- References
- 1. Vince A. Partap. The Comet Tail Sign. Radiology 1999; 213:553-554.
2. Terence C. Doyle, Gary A. Lawler. CT Features of Rounded Atelectasis of the Lung. AJR 1984; 143:225-228.
- Please refer to
- Case 38
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- Keywords
- Lung, Non-infectious inflammation,