Round atelectasis, also known as rounded atelectasis, folded lung or Blesovsky syndrome, is an unusual type of lung atelectasis where there is infolding of a redundant pleura. The way the lung collapses can at times give a false mass-like appearance.

Epidemiology

Associations

Round atelectasis may be associated with:

• asbestos lung exposure ³: most commonly

• therapeutic pneumothorax in the treatment of tuberculosis ¹

• congestive heart failure ²

• hepatic hydrothorax ¹⁷

• end stage renal disease ¹⁷

• pulmonary infarction ²

• post-infectious pleural inflammation / parapneumonic effusion

Pathology

Two theories have been put forward. The second theory is more favored while the multifactorial etiology suggests both mechanisms probably operate in different patients:

• Hanke and Kretzschmar

  • underlying pleural effusion causes local atelectasis in the adjacent lung

  • a cleft or infolding of the visceral pleura will then form if the rate of pleural fluid formation exceeds alveolar air absorption

  • this then causes the lung to tilt on the cleft

  • the lung then curls on itself in a concentric fashion

  • fibrous adhesions suspending the atelectatic segment (and usually tilt the lung cranially) develop

  • as the effusion resorbs, the aerated lung fills in the space between the area of round atelectasis

  • organization of the fibrinous exudate and fibrous contraction lead to additional lung parenchymal distortion

• Schneider et al. (expanded on by Dernevik and colleagues)

  • a local pleuritis caused by irritants such as asbestos

  • in the event of a benign asbestos-related pleural effusion, the pleura contracts and thickens with shrinkage of the underlying lung, and atelectasis develops in a round configuration

Etiology

• exposure to mineral dust: asbestosis, pneumoconiosis ¹³ 

• exudative pleuritis: tuberculosis, hemothorax ¹³ 

• less commonly seen in histoplasmosis, legionella, end-stage renal disease ¹³

• sarcoidosis ¹³

Location

There may be a predilection towards the lower lobes ⁴.

Radiographic features

CT

• round or oval in shape 

• almost always seen adjacent to a pleural surface

• there is associated adjacent pleural abnormality, e.g. pleural thickening or pleural effusion

• comet tail sign ²: produced by the pulling of bronchovascular bundles giving the shape of a comet tail

• crow feet sign

• as it represents collapsed lung, it commonly demonstrates a typical parenchymal enhancement 

• posterior lower lobes are most commonly involved and, sometimes, bilateral or symmetrical ¹⁴

Rounded atelectasis can occasionally increase in size on serial scans ^6,7.

Nuclear medicine

FDG-PET

• not metabolically active

• may play a role in differentiating from malignancy when there are few or atypical features on chest radiographs and CT ⁹

Diagnosis

All five of the following findings must be present to diagnose round atelectasis:

1) Adjacent pleura must be abnormal.

2) Opacity must be peripheral and in contact with the pleura.

3) Opacity must be round or elliptical.

4) Volume loss must be present in the affected lobe.

5) Pulmonary vessels and bronchi leading into the opacity must be curved — this is the comet tail sign¹⁵.

History and etymology

It was first described by Loeschke in 1928 ⁶.

See also

• pulmonary pseudotumor

• pulmonary inflammatory pseudotumor