Pleural Effusion

Pleural effusion is the accumulation of excessive fluid in the pleural space, the potential space surrounding each lung. Under normal conditions pleural fluid is secreted by the parietal pleural capillaries and cleared by lymphatic absorption, leaving behind only a small amount of fluid that helps maintain a functional vacuum between the two layers of the pleura. Excess fluid in the space can impair inspiration by upsetting that vacuum and increasing resistance against lung expansion, resulting in a fully or partially collapsed lung.