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 often 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).