aetiology

Last reviewed 01/2021

A variety of diseases and medications may be responsible for accumulation of fluid in the pleural cavity (1)

The causes of a pleural effusion can be divided into exudative and tansudative - classically exudates having a protein level >30 g/l and transudates <30 g/l. A more accurate differentiation can be made using Light’s criteria (2)

If the protein content of the effusion is not known then the most common causes of a pleural effusion are:

  • infection, e.g. underlying pneumonia
  • tuberculous pleurisy
  • infarction of underlying lung
  • malignancy
  • organ failure, e.g. cardiac, liver, kidney

Although there are various conditions which lead to effusions, majority are idiopathic and tend to follow a benign course (1)  

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