Effusion

Effusion: Too much fluid, an outpouring of fluid. A hemorrhagic effusion is one that has blood within the fluid. A pericardial effusion is an outpouring of fluid within the fibrous sac (the pericardium) that surrounds the heart. The lungs are covered by two-layered membranes which are called the pleura. A pleural effusion involves the presence of an excessive amount of pleural fluid (between the two layers of the pleural membranes). The term "effusion" comes from the Latin "effusio" meaning a pouring out.