Fact-sheet: Atelectasis


Updated on 07/01/2020 at 8:53 AM

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Definition

Atelectasis corresponds to the collapse of pulmonary alveoli due to lack of ventilation, while blood flow remains normal.

It manifests as retractile consolidation of a lung region with bronchial topography, resulting from complete obstruction of the bronchus supplying it.

Atelectasis may involve an entire lung, a lobe, or segments.

The most common factors underlying atelectasis include the following:
Intrinsic airway obstruction (e.g., foreign body, tumor, mucous plug)
  • Extrinsic airway compression (e.g., tumor, lymphadenopathy)
  • Suppression of breathing or coughing (e.g., general anesthesia)
  • Supine positioning, particularly in obese patients and in cases of cardiomegaly
  • Compression or involvement of the lung parenchyma (e.g., large pleural effusion or pneumothorax)

Clinical features

Atelectasis is usually asymptomatic, but hypoxemia and pleuritic chest pain may be present in some cases.

In cases of significant atelectasis, asymmetric ventilation is observed, with immobility of one hemithorax and absence of breath sounds

Radiography

The specific radiologic signs of atelectasis are:

Direct signs:

  • homogeneous opacity,
  • with lobar/segmental distribution,
  • retractile,
  • unilateral, without air bronchogram.

Indirect signs (related to the retractile phenomenon):

  • shift of the mediastinum and trachea toward the side of the atelectasis,
  • ipsilateral elevation of the hemidiaphragm,
  • rib crowding.

CT

The specific radiologic signs of atelectasis are:

Direct signs:

  • homogeneous opacity,
  • segmental,
  • retractile,
  • unilateral without air bronchogram.

Indirect signs (related to the retractile phenomenon):

  • mediastinal and tracheal shift toward the side of the atelectasis,
  • ipsilateral elevation of the hemidiaphragm,
  • rib crowding.