Definition of Pleural effusion:

A pleural effusion is an accumulation of fluid between the layers of tissue that line the lungs and chest cavity.

Causes, incidence, and risk factors:

Your body produces pleural fluid in small amounts to lubricate the surfaces of the pleura, the thin tissue that lines the chest cavity and surrounds the lungs. A pleural effusion is an abnormal, excessive collection of this fluid.

Two different types of effusions can develop:

• Transudative pleural effusions are caused by fluid leaking into the pleural space. This is caused by elevated pressure in, or low protein content in, the blood vessels. Congestive heart failure is the most common cause.
• Exudative effusions usually result from leaky blood vessels caused by inflammation (irritation and swelling) of the pleura. This is often caused by lung disease. Examples include lung cancer, lung infections such as tuberculosis and pneumonia, drug reactions, and asbestosis.