Chest Imaging

Atelectasis

(also called collapse), a loss of volume of lung parenchyma caused by a reduced inflation. Several mechanisms may be responsible for atelectasis. They include the following:

  • resorption or obstructive atelectasis resulting from bronchial obstruction;

  • compression or passive atelectasis which is collapsed caused by extrinsic compression such as pleural fluid or air, or the presence of any space-occupying intrathoracic lesion resulting in extrinsic compression of adjacent parenchyma;

  • cicatrization atelectasis resulting from lung parenchymal fibrosis; and

  • adhesive atelectasis which is collapse resulting from loss of surfactant.

    Atelectasis may involve one or more lobes or segments (see lobar atelectasis). In other circumstances, atelectasis can have a nonanatomical distribution. Air within the collapsed or atelectatic lung parenchyma can be entirely resorbed and partially replaced by fluid or fibrosis (nonaerated lung collapse). It appears radiologically as an opacification. When air within the collapsed lung parenchyma is only partially resorbed and not replaced by any fluid or tissue, no radiological opacification is depicted (aerated lung collapse).

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