Parapneumonic effusion

A parapneumonic effusion refers to an exudative pleural effusion associated with pneumonia.

Approximately 40-45% of patients who are hospitalized for pneumonia develop a parapneumonic effusion 3.

Fluid leaks into the pleural space due to increased permeability of the visceral pleura adjacent to the infected lung. Bacterial pneumonia is a more common cause of parapneumonic effusions than viral pneumonia 3

Similar findings to a simple pleural effusion 1:

  • usually small volume
  • normal meniscus sign
  • dependent
  • no loculation (very rarely can be loculated)
  • "split pleura sign" is not typical and more specific for empyema
  • empyema: , ~7.5-10 % of patients with parapneumonic pneumonia progress to a fibrinopurulent stage such as empyema 3-4

Parapneumonic effusions often resolve with the treatment of underlying pneumonia. Some authors suggest effusions with depth measurements of <2.5 cm able to be conservatively managed without thoracentesis 4

Article information

rID: 30524
System: Chest
Synonyms or Alternate Spellings:
  • Parapneumonic effusions
  • Parapneumonic effusion (PPE)

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Cases and figures

  • Case 1
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  • Case 2: pneumococclal pneumonia
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  • Case 3: loculated
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