Pleural Effusion
(Fluid In the Chest or On the Lung)

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Pleural effusion definition

A pleural effusion is a buildup of fluid in the pleural space, an area between the layers of tissue that line the lungs and the chest cavity. It may also be referred to as effusion or pulmonary effusion. The type of fluid that forms a pleural effusion may be categorized as either transudate or exudate. Transudate is usually composed of ultrafiltrates of plasma due to an imbalance in vascular hydrostatic and oncotic forces in the chest (heart failure, cirrhosis), while exudate is typically produced by inflammatory conditions (lung infection, malignancy). Exudative pleural effusions are usually more serious and difficult to treat.

What are the causes of pleural effusion?

There are many causes of pleural effusions. The following is a list of some of the major causes:

The development of a pleural effusion occurs from fluid seeping into the pleural space, a thin area between the visceral and pleural membranes in the chest cavity, which normally contains a small amount of fluid to facilitate smooth lung movement. Fluid under pressure, malignant cells, and infectious agents can occasionally enter this space and cause it to expand with abnormal amounts of fluid and other compounds (see diagnosis section).

Picture of pleural effusion
Picture of pleural effusion

X-ray of pulmonary effusion
X-ray of pulmonary effusion courtesy of the CDC

Medically Reviewed by a Doctor on 2/6/2015

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