Fluid in airspaces produces a diffuse ‘fluffy’ shadowing. Oedema most commonly occurs due to heart failure but it can also be caused by:

  • Fluid overload – iatrogenic or renal failure
  • Hypoproteinaemia
  • Drug reactions/poisoning
  • Cerebrovascular disease
  • Drowning
  • Acute respiratory distress syndrome (ARDS)

An early sign of heart failure is upper lobe blood diversion (Fig 1). Later interstitial oedema manifests as Kerley A and B lines. There may also be fluid in the horizontal fissure and small effusions. At a later stage frank pulmonary oedema is seen (Fig 2).

Click on the x-rays to enlarge.

Fig 1: Early heart failure Fig 2: Frank pulmonary oedema