Pleural effusion:Excess fluid between the two membranes that cover thelungs(thevisceralandparietalpleurae) separating the lungs from thechestwall. A small quantity of fluid is normally spread thinly over the visceral and parietal pleurae and acts as alubricantbetween the two membranes. Any significant increaseinthe quantity ofpleuralfluid is apleural effusion. The most common symptoms of pleuraleffusionare chest pain and painful breathing (pleurisy). Many pleural effusions cause no symptoms but are discovered during physical examination or detected on chest X-rays;X-rayis the most convenient way to confirm thediagnosis. Pleural effusion can be caused by heart and kidney failure,hypoalbuminemia(low levels ofalbuminin theblood)、感染、肺栓塞和马lignancies.
