Pleural Effusion

What is a pleural effusion?

A pleural effusion means that there is a build up of fluid between a lung and the chest wall.

The pleura is a thin membrane that lines the inside of the chest wall and covers the lungs. There is normally a tiny amount of fluid between the two layers of pleura. This acts like lubricating oil between the lungs and the chest wall as they move when you breathe. A pleural effusion develops when this fluid builds up and separates the lung from the chest wall.

What are the symptoms?

You may feel some chest pain but a pleural effusion is often painless. The amount of fluid varies. As the effusion becomes larger, it presses on the lung which cannot expand fully when you breathe. You may then become breathless.

You may also have symptoms of the condition that is causing the effusion. For example, cough, and fever if the cause is pneumonia.

A pleural effusion is a complication of various conditions. The following are some of the more common causes of a pleural effusion (but there are other rarer causes too).

• Pneumonia (lung infection), tuberculosis, and tumours (cancers) may cause inflammation of the lung and pleura. This may cause fluid to build up into a pleural effusion.
• Some arthritic conditions may cause inflammation of the pleura in addition to joint inflammation. For example, pleural effusion is an uncommon complication of rheumatoid arthritis and systemic lupus erythematosis (SLE).
• Heart failure causes 'back pressure' in the blood vessels (veins) that take blood back to the heart. Some fluid may seep out of the blood vessels. Swelling of the legs with fluid is typical with heart failure, but a pleural effusion may also develop.
• A low level of protein in the blood also tends to allow fluid to seep out of the blood vessels. For example, cirrhosis of the liver and some kidney diseases may cause a low level of blood protein which allows a pleural effusion to develop.

A chest x-ray confirms a pleural effusion. If the cause of the effusion is known then no further tests may be needed. However, sometimes a pleural effusion is the first sign of an underlying condition. Further tests may then be advised to find the cause of the effusion. These may include lung tests, blood tests, and taking a sample of the fluid and pleura to examine in the laboratory.

A large pleural effusion that makes you breathless can be drained. This is usually done by inserting a needle or tube through the chest wall. A local anaesthetic is injected into the skin and chest wall first to make the procedure painless.

A major part of treatment is usually directed to the underlying cause of the effusion. For example, antibiotics for pneumonia, chemotherapy or radiotherapy for cancers, etc. Therefore, treatment can vary greatly, depending on the cause of the effusion.

© EMIS and PIP 2006   Updated: June 2006