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

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

Two different types of effusions can develop:

• Transudative pleural effusions are usually caused by abnormal lung pressure. Congestive heart failure is the most common cause.
• Exudative effusions form as a result of inflammation (irritation and swelling) of the pleura. This is often caused by lung disease. Examples include lung cancer, pneumonia, tuberculosis and other lung infections, drug reactions, asbestosis, and sarcoidosis.

• Shortness of breath
• Chest pain, usually a sharp pain that is worse with cough or deep breaths
• Cough
• Hiccups
• Rapid breathing

There may be no symptoms.

During a physical examination, the doctor will listen to the sound of your breathing with a stethoscope and may tap on your chest to listen for dullness.

The following tests may help to confirm a diagnosis:

• Chest x-ray
• Thoracic CT
• Ultrasound of the chest
• Thoracentesis
• Pleural fluid analysis

The cause and type of pleural effusion is usually determined by thoracentesis (a sample of fluid is removed with a needle inserted between the ribs).

Treatment may be directed at removing the fluid, preventing its re-accumulation, or addressing the underlying cause of the fluid buildup.

Therapeutic thoracentesis may be done if the fluid collection is large and causing pressure or shortness of breath. Treatment of the underlying cause of the effusion then becomes the goal.

For example, pleural effusions caused by congestive heart failure are treated with diuretics and other medications that treat heart failure. Pleural effusions caused by infection are treated with antibiotics specific to the causative organism. In patients with cancer or infections, the effusion is often treated by using a chest tube to drain the fluid. Chemotherapy, radiation therapy, or instilling medication within the chest that prevents re-accumulation of fluid after drainage may be used in some cases.

The expected outcome depends upon the underlying disease.

• A lung surrounded by a fluid collection for a long time may collapse.
• Pleural fluid that becomes infected may turn into an abcess, called an empyema, which requires prolonged drainage with a chest tube placed into the fluid collection.
• Pneumothorax (air within the chest cavity) can be a complication of the thoracentesis procedure.

Call your health care provider if symptoms suggestive of pleural effusion develop.

Call your provider or go to the emergency room if shortness of breath or difficulty breathing occurs immediately after thoracentesis.