The lungs are covered by a membrane or lining, called the pleura, which has an inner layer and an outer layer. The inner layer covers the lungs. The outer layer lines the rib cage and diaphragm, which is a sheet of muscle which separates the chest from the abdomen.

The pleura produces a fluid which acts as a lubricant that helps you to breathe easily, allowing the lungs to move in and out smoothly. Sometimes too much of this fluid can build up between the two layers of the pleura: this is called a pleural effusion.

Pleural effusions are quite common and are often due to infections such as pneumonia, or heart failure, when the heart is not pumping the blood efficiently around the body.

A pleural effusion can also be a symptom of several types of cancer. A pleural effusion usually develops if cancer cells have spread into the membrane lining the lungs, where they can lead to irritation and cause fluid to build up. The types of cancer that are more likely to cause a pleural effusion are lung cancer, breast cancer, ovarian cancer, lymphomas and mesothelioma (cancer of the pleura).

The build-up of fluid presses on the lung, making it difficult for the lung to expand fully. In some situations part or all of the lung will collapse. This can make you increasingly breathless, not only when you are active, but also when you are resting. You may also get some chest pain and a cough.

The treatment of a pleural effusion involves slowing the build-up of the fluid and draining it to relieve the symptoms.

The drain is usually inserted by a doctor. Sometimes the doctor uses images produced by sound waves (an ultrasound) to help guide the drain into the correct position. You will be asked to sit either on a chair or on the edge of the bed and then helped to lean forward over a table with a pillow to bend on so that your back is exposed. The doctor will decide where to insert the drain – usually in the side of the chest. The skin over the area where the drain is to be inserted is cleaned with an antiseptic solution to prevent the area from becoming infected. The doctor then gives you an injection of local anaesthetic to prevent the procedure from being painful.

When the area has been anaesthetised the doctor makes a very small cut in the chest and inserts a needle called a cannula. The cannula is attached to a tube and drainage bag or bottle. The fluid drains out of the chest and collects inside the bag or bottle. The fluid that drains may be bloodstained. You will usually need to stay in hospital for a couple of days if there is a large amount of fluid. If there is only a small amount of fluid, the cannula is removed immediately after the fluid has been drained off and the area is covered with a dressing. Otherwise, the cannula will be held in place with a small stitch.

When the local anaesthetic wears off, you may have some pain or discomfort. Let the doctor or nurse know if you have any pain, as painkillers can be prescribed to help.

Once the drainage has slowed down and the doctors think that most of the fluid has drained, you will have a chest x-ray to see how well your lung has re-expanded. If it has, the drain will be removed.

In some situations it may be possible to have your pleural effusion drained while you are at home using a catheter that is very similar to a chest drain. The catheter will be put in while you are in the hospital, where it will be attached to a suction bottle that will gently suck out some of the fluid. It is then clamped off and covered with a dressing. You can then go home. A district nurse will visit to re-attach the suction bottle to your catheter and drain off some more fluid. This is repeated over the next few days, as many times as necessary to drain off all the fluid. Draining the fluid from time to time in this way helps to encourage the lung to re-inflate and the layers of the pleura to seal together.

Your specialist nurse will teach you, or your carers, how to look after the catheter and suction bottle when you are at home. Once the fluid has stopped draining, you will go back to the hospital to have the catheter removed.

If the lung re-inflates after the fluid has been drained it may be possible to seal the two layers of the pleura together to prevent the fluid from building up again. This is known as pleurodesis. It can usually be done using drugs called bleomycin or tetracycline, or sometimes talc, which are injected through the drain.

The doctor injects the drug through the drain and then leaves the drain clamped for approximately one hour. You will be asked to lie in various positions in the bed (eg on your back, your front, your left side and your right side), to help the drug circulate around the lining of the lungs. The drain may then be attached to a suction machine to apply a small amount of pressure, which encourages the pleura to become sealed together.

When the drain is removed, if there is a stitch that has been holding the drain in, it can be pulled together, sealing the hole which is then covered with a dressing. The stitch is usually removed about a week later. Sometimes just a dressing is used to cover the area where the drain has been.

It is possible for the pleural effusion to collect again and drainage may need to be carried out more than once.

Your doctor may also prescribe chemotherapy or hormonal therapy to treat the cancer and help prevent the fluid from building up again.

Usually the fluid will be drained off fairly slowly, as a sudden release of pressure in the chest can cause a drop in blood pressure. A litre of fluid may be drained safely as soon as the drain has been inserted. After this, drainage should be done more slowly. Your blood pressure will be checked during the procedure. You should let your doctor or nurse know if you feel dizzy, sick or light-headed.

The chest drain can become blocked, although this is rare. It can sometimes be cleared by changing your position or sitting upright. Occasionally the drain may need to be replaced.

The drain can become infected. You will have your temperature checked for any sign that you are developing an infection.

If you find the drainage-tube causes discomfort, try changing its position slightly.

If a pleurodesis is necessary this can sometimes cause chest pain for a day or so after the treatment and you may need to take painkillers.

If your drainage tube is attached to a bottle, you will be able to walk about with it. It is important to be careful with the bottle, and it should not be raised above
the level of the chest, as the fluid could go back into your lungs.

This section is based upon our Pleural effusions factsheet which has been compiled using information from a number of reliable sources including:

• Oxford Textbook of Oncology (2nd edition). Souhami et al. Oxford University Press, 2002.
• Cancer and Its Management (5th edition). Souhami and Tobias. Oxford Blackwell Scientific Publications, 2005.
• Symptom Management in Advanced Cancer (3rd edition). Twycross and Wilcock. Radcliffe Medical Press, 2001.

For further references, please see the general bibliography.