Pleural effusion (fluid on the lung): symptoms, causes and treatment

Cancer Research UK says that feeling breathless may be the first and only symptom of a pleural effusion, although you may also have a cough and chest pain. Macmillan Cancer Support adds that the build-up of fluid presses on the lung, making it harder for the lung to expand fully, so you may feel more breathless even when resting.

A Frimley Health NHS Foundation Trust leaflet says that the amount of fluid varies, that you may feel some chest discomfort but an effusion is often painless, and that you may also have symptoms of the condition causing the effusion. In some situations, Macmillan says, part or all of the lung can collapse.

Cancer Research UK says that if you suddenly become breathless or your breathing gets worse, you should call 999 or go to your local A&E straight away, as you may need urgent treatment.

For chest pain, the NHS pleurisy page says to call 999 or go to A&E for sudden chest pain that lasts 15 minutes or more or spreads to your arms, back, neck or jaw, difficulty breathing, or coughing up more than a few spots or streaks of blood. It says to ask for an urgent GP appointment or call NHS 111 for sharp chest pain that comes and goes or has not got better after a few days, small streaks of blood in phlegm, or regular breathlessness.

The lungs are covered by a thin lining called the pleura, which has two layers. Macmillan explains that the inner layer covers the lungs and the outer layer lines the ribcage and the diaphragm, and that between the layers is a small amount of fluid that acts as a lubricant, helping the lungs move smoothly as you breathe.

Sometimes too much of this fluid builds up between the layers. This is a pleural effusion. Cancer Research UK points out that it is not the same as pulmonary oedema, which is fluid inside the lung and usually caused by heart problems.

Macmillan says a pleural effusion is common and is often caused by lung infections such as pneumonia, or by heart failure, where the heart does not pump blood around the body as well as it should. Cancer Research UK gives cancer, heart failure and a severe chest infection as the most common causes.

The Frimley leaflet lists cancer, infection, blood clots, inflammatory diseases and heart failure as underlying causes. When cancer is the cause it may be called a malignant pleural effusion, and Cancer Research UK says this is more likely with lung cancer, mesothelioma, breast cancer and ovarian cancer. Macmillan adds lymphomas to this list.

Cancer Research UK says your doctor needs to work out the cause. They will ask about your general health, medical history and medication, and examine you. You usually have a chest X-ray or a chest ultrasound scan to diagnose a pleural effusion, and some people have a CT scan if more information is needed. These show where the fluid is and how much there is.

The Frimley leaflet describes a pleural clinic visit where you usually have an ultrasound scan of the chest, a small sample of fluid may be taken with local anaesthetic, and if there is a lot of fluid a small tube may be inserted to drain it. It notes that if you take blood thinners such as warfarin, apixaban or clopidogrel the team needs to know before the visit, and you should not stop them without discussion.

The Frimley leaflet says treatment varies greatly depending on the cause. If the underlying cause can be treated successfully there is a good chance the effusion will go away for good, but if it cannot be treated or can only be partly treated, the effusion may return if it is drained. Small effusions that cause no symptoms or only mild symptoms may just be observed, and treatment is usually only needed if the effusion causes symptoms.

Cancer Research UK and Macmillan describe the main ways of removing the fluid. Macmillan says that draining the fluid can relieve symptoms, and that a small effusion may be drained with a needle or thin tube and syringe, while a chest drain is usually used for larger collections.

Macmillan says fluid is usually drained slowly, because a sudden release of pressure in the chest can cause blood pressure to drop; about 1 litre may be drained safely at first and then more slowly. You may feel dizzy, sick or light-headed, and should tell your doctor or nurse if so.

It lists possible side effects including pain when the local anaesthetic wears off and, sometimes, a lung that cannot re-expand fully, leaving an air-filled space (a pneumothorax). A small pneumothorax may need no treatment, whereas a larger one may need another drain. Tell your doctor or nurse straight away about signs of infection such as a high temperature or feeling unwell.

Cancer Research UK says shortness of breath from a pleural effusion can be very uncomfortable and may make you anxious. It suggests sitting supported upright in bed or an armchair, or sitting on the edge of a bed or chair and leaning forward with your arms resting on pillows on a bed table, which lets your lungs expand as fully as possible.

Let your doctor or nurse know if you find it difficult to cope, and let family and friends know how you are feeling so they can help.

The sources used here describe pleural effusion mainly in adults. A child with breathing difficulty, chest pain or a persistent cough should be seen by a GP or paediatric team, and the NHS emergency advice above applies to children too.

If you are pregnant and become more breathless, develop chest pain or have a cough that is getting worse, contact your midwife or GP or call NHS 111 so the cause can be assessed.

On the NHS, a pleural effusion is usually found on a chest X-ray ordered by a GP or in hospital, and you may be seen in a pleural clinic for ultrasound, fluid sampling and drainage. Cancer teams, heart teams and respiratory teams treat the underlying cause.

Private respiratory clinics can offer chest imaging, ultrasound and specialist review. Ask who will arrange drainage and send fluid for analysis, how results will be shared with your GP, and what happens if fluid builds up again.