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Lung Disease & Respiratory Health Center

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Pleural Effusion

A pleural effusion is an abnormal amount of fluid around the lung. Pleural effusions can result from many medical conditions. Most pleural effusions are not serious by themselves, but some require treatment to avoid problems.

Causes of Pleural Effusions

The pleura is a thin membrane that lines the surface of the lungs and the inside of the chest wall outside the lungs. In pleural effusions, fluid accumulates in the space between the layers of pleura. Normally, only teaspoons of watery fluid are present in the pleural space, allowing the lungs to move smoothly within the chest cavity during breathing.

Numerous medical conditions can cause pleural effusions. Some of the more common causes are:

Excessive fluid may accumulate because the body does not handle fluid properly (such as in congestive heart failure, or kidney and liver disease). The fluid in pleural effusions also may result from inflammation, such as in pneumonia, autoimmune disease, and many other conditions.

Symptoms of Pleural Effusions

Pleural effusions often cause no symptoms. Symptoms are more likely when a pleural effusion is moderate or large-sized, or if inflammation is present. Symptoms of pleural effusions may include:

Because pleural effusions are usually caused by underlying medical conditions, symptoms of these conditions are also often present.

Diagnosis of Pleural Effusions

A doctor may suspect a pleural effusion based on a person's symptoms and physical examination. Doctors may use auscultation (listening with a stethoscope), percussion (tapping on the chest), and other maneuvers when a pleural effusion is suspected.

Most often, pleural effusions are discovered on imaging tests. Common tests used to identify pleural effusions include:

Chest X-ray film: Plain X-ray films of the chest are often the first step in identifying a pleural effusion. Pleural effusions appear on chest X-rays as white space at the base of the lung. If a pleural effusion is likely, additional X-ray films may be taken while a person lies on her side. Called decubitus X-ray films, these can show if the fluid flows freely within the chest.

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