Round atelectasis

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.

Pathology

Two theories have been put forward. The second theory is more favored while the multi-factorial 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

Associations

It can be associated with:

• asbestos lung exposure ³: most commonly
• therapeutic pneumothorax in the treatment of tuberculosis ¹
• congestive heart failure ²
• pulmonary infarction ²
• parapneumonic effusion

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

History and etymology

It was first described by Loeschke in 1928 ⁶.

See also

• pulmonary pseudotumor
• pulmonary inflammatory pseudotumor