2023 Mar 18. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
Pleural effusion is the accumulation of fluid in between the parietal and visceral pleura, called the pleural cavity. It can occur by itself or can be the result of surrounding parenchymal disease like infection, malignancy, or inflammatory conditions. Pleural effusion is one of the major causes of pulmonary mortality and morbidity.
All healthy humans have a small amount of pleural fluid that lubricates the space and facilitates normal lung movements during respiration. This delicate balance of fluid is maintained by the oncotic and hydrostatic pressure and lymphatic drainage; disturbances in any one of these systems can lead to a build-up of pleural fluid.