Revision 20 for 'Air-space opacification (summary)'

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Air-space opacification (summary)

Air-space opacification is a descriptive term that refers to filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is equivalent to the pathological diagnosis of pulmonary consolidation.

Reference article

This is a summary article; read more in our article on air space opacification.


  • pathophysiology
    • material fills the pulmonary tree
      • fluid: pulmonary edema 
      • pus: pneumonia
      • blood: pulmonary hemorrhage
      • cells: cancer
      • protein: alveolar proteinosis (rare)
  • investigation
    • chest x-ray
      • confirmation of consolidation and additional findings
      • assessment of:
        • severity, e.g. number of lobes involved
        • accompanying pathology, e.g. effusion
        • complications, e.g. abscess formation
    • CT chest
      • air space opacification looks very similar to the chest x-ray
      • distribution can be assessed more accurately
      • assessment of associated features is more accurate

Radiographic features

Plain radiograph

Consolidated areas are radio-opaque on chest radiograph and chest CT compared to normally air-filled lung tissue. The distribution pattern of consolidation can aid in narrowing the potential differential diagnosis.


The air-space filling is only partial and there is, therefore, residual gas within the alveoli. 


Where increased density/opacity is seen in individual lung lobes. Sharp delineation can be seen when consolidation reaches a fissure. Air bronchograms can also be seen where air-filled bronchi are visible against the dense diseased tissue. Volume loss is not usually seen.


Most commonly due to heart failure, resulting in other signs such increased cardiac size, Kerley B-lines, redistribution on pulmonary blood flow and pleural fluid.


Multiple areas of opacity seen throughout the lung most often are due to bronchopneumonia, starting from bronchi and spreading outwards. Usually ill-defined with peripheral distribution. Neoplasms such as a primary malignancy or metastasis can also cause this picture.

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