<unk>  is defined as the presence of excessive fluid in the<unk>  cavity resulting from transudation or exudation from the<unk>  surfaces. In normal conditions, the<unk>  space contains a limited amount of fluid (≈0.3 mL·kg-1) maintained by a complex interplay of hydrostatic pressures and lymphatic drainage, which allows for steady liquid and protein turnover. Pathological processes may lead to the development of<unk> s by causing disequilibrium between the rates of<unk>  fluid formation,<unk> <unk> rmeability and<unk>  fluid absorption.<unk>  may be secondary to<unk>  processes, pulmonary disorders, systemic conditions, and medications. A systematic approach with a comprehensive clinical history and physical examination is required for establishing the etiology.
Pleural effusion
Pleurisy
Parapneumonic effusion
Hydrothorax
Trapped lung
Pneumothorax
Hemothorax
Round pneumonia