Alveolar oedema - Bat's wing pattern

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Alveolar oedema - Bat's wing pattern

  • Alveolar oedema is caused by fluid leaking from the interstitial tissues into the alveoli and small airways, and manifests as airspace shadowing (consolidation)
  • In the context of acute pulmonary oedema, alveolar oedema radiates symmetrically from the hilar regions in a ‘bat's wing’ distribution of airspace shadowing
  • Note the enlarged heart (CTR 60%) and the cardiac surgery artifact – sternal wires and metallic heart valve
  • Blunting of the costophrenic angles is due to pleural effusions – interstitial fluid has leaked into the pleural cavity

Asymmetric bat's wing shadowing

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Asymmetric bat's wing shadowing

  • Bat's wing pulmonary oedema may not be symmetrical
  • Note the septal lines on the right (interstitial oedema) and blunting of the costophrenic angles bilaterally (pleural effusions)
  • The oxygen tubing and ECG buttons have not been removed – indicating the patient is acutely unwell

Pulmonary oedema

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Pulmonary oedema

  • Images which show pulmonary oedema are frequently of poor quality because the patient is too unwell to stand or hold their breath
  • This is a common appearance of acute pulmonary oedema
  • Remember that bilateral air space shadowing may also be caused by other disease processes such as infection – it is usually the clinical features that indicate the diagnosis

Non-cardiogenic pulmonary oedema

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Non-cardiogenic pulmonary oedema

  • Pulmonary oedema may be non-cardiogenic (not caused by heart disease)
  • This patient had pulmonary oedema secondary to nephrotic syndrome – albumin was very low
  • Note that the heart size is normal (CTR <50%)
  • If the heart size is normal, then heart disease may still be the cause of pulmonary oedema, but non-cardiogenic causes should also be considered
  • The converse is also true – if the heart is enlarged, then the cause of pulmonary oedema is not always cardiac