Discussion of Round atelectasis
- Pathogenesis of round atelectasis is not certain, but it is thought to be due to an inflammatory reaction and fibrosis in the superficial layer of the pleura.
- As the fibrous tissue matures, it contracts, causing pleura to fold into the lung, which in turn causes atelectasis.
- Round atelectasis is almost always asymptomatic and is detected on chest radiographs obtained for other reasons.
- A history of asbestos exposure is frequently (in 70% of cases) present. Asbestos-related round atelectasis is also known as asbestos pseudotumor or Blesovsky syndrome.
- Conditions such as congestive heart failure, pulmonary infarction, Dressler syndrome, parapneumonic effusion, tuberculous effusion, and nonspecific pleurisy can precede round atelectsis formation.
- Lung cancer is the main differential diagnosis.
- After diagnosis, a follow-up CT should be obtained to exclude lung cancer.
 Imaging Findings for Round atelectasis
 Plain film
- The typical chest radiographic appearance is of a rounded peripheral "mass" with or without lung distortion.
- Pleural thickening is usually seen.
- The CT features are:
- A round or oval mass that abuts the pleura
- Has sharp lung borders
- Has a fuzzy border which projects to the hila (Origin of Comet tail sign)
- a "comet tail" of bronchovascular structures going into the mass (Comet tail sign).
- Thickening of the adjacent pleura.
- Volume loss is often, but not invariably, apparent.
 See Also
 External Links
 References for Round atelectasis
- Vince A. Partap. The Comet Tail Sign. Radiology 1999 213: 553-554.
- Huw D. Roach, Gareth J. Davies, Richard Attanoos, Michael Crane, Haydn Adams, and Siân Phillips. Asbestos: When the Dust Settles—An Imaging Review of Asbestos-related Disease. RadioGraphics 2002 22: 167S-184S.