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Chest x-ray evaluation of the lung fields overview

Published: November 02, 2017. Updated: November 02, 2017

Evaluation of the lung fields in a chest x-ray requires a systematic approach. In general, the opacity of the normal lung fields increases from top to bottom, especially in women where the breast tissue is superimposed on the lower lung fields. Moreover, both the blood vessels and the bronchi are seen in the central third of the chest and tend to fade out towards the periphery.

Diffuse white area (opacity)

A diffuse lesion is a lesion that is not limited to a specific area of the lung, and can be found anywhere as opposed to focal lesions which are limited to a specific area in the lung.

  • Nodular ? discrete opacities
  • Reticular ? mesh like appearance
  • Alveolar ? ?fluffy? appearance

The diffuse patterns are not always easy to interpret and the descriptive categories above are not very specific. Generally, the following pathologies need to be considered.

Pulmonary edema

?Upper lobe diversion
Kerly B lines ? horizontal, non-branching white lines best seen at the periphery of the lung above the costophrenic angle.
The confluent shadowing of severe heart failure gives an alveolar pattern spreading out from the hilum - ?bat?s wing?

Pulmonary fibrosis

Tends to be reticular or fine reticulo-nodular shadowing
Review old CXRs May be confused with oedema.
More likely to be fibrosis if the middle / upper lobes are involved
Small lung fields / reduced expansion
Mediastinal shift toward the shadowing

Metastatic disease

  • Tends to be nodular (coarse)
  • Tend towards the bases and the peripheries

Bilaoteral pneumonia

Can be difficult to separate from pulmonary oedema, sarcoidosis or metastatic disease.

Miliary TB

Apical shadowing


Looks much like pulmonary oedema, but exists in the settings of extreme sepsis, trauma, poisoning.

Not sure if there is an abnormality or not?

  • Look for air bronchogram
  • Silhouette sign (heart and diaphragm)
  • Site of suspected lesion:
    • Nodularity in the outer 1/3 is abnormal.
    • Nodularity in the middle 1/3 is tapering laterally and nodules there are no bigger than size of expected vessels.
    • Nodularity in the inner 1/3 takes the pattern of branching vessels and nodules there are no bigger than size of expected vessels.

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