A pleural effusion is the accumulation of extra fluid in the pleural cavity.
A pleural effusion can develop if the normal physiological flow of pleural fluid is disturbed by pleural inflammation (including tumor infiltration) or obstruction of the pulmonary lymphatic or venous channels.
- Inflammation of pleural surface
Infiltration by tumor: exudate
Infection, infarction, irradiation: exudate
- Lymphatic obstruction
Peripheral obstruction by tumor: transudate
Central (mediastinal) obstruction: exudate
- Raised pulmonary venous pressure
Local venous obstruction by tumor: transudate
Cardiac failure, pericardial tamponade: transudate
- Other edematous conditions
Hypoproteinemia, renal or liver failure: transudate
Pleural effusions cause dyspnea, a nonproductive cough and chest pain that may be dull and aching or pleuritic. Dyspnea varies from mild to severe and depends on both the size and speed of accumulation of the effusion.
Small effusions and those occurring in patients who are relatively immobile are unlikely to cause significant symptoms.
Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. Fourth edition. Oxford University Press, 2004. (p. 199)