Overview
A pleural effusion is a build-up of extra fluid in the pleural space, the thin gap between the two layers of tissue (the pleura) that cover the lung and line the chest wall. A little fluid is normal there, and it lets the layers glide as you breathe.
Too much fluid squeezes the lung so it cannot expand fully. People often call this water in the lung, but the fluid collects around the lung, not inside it. An effusion is usually a sign of another illness, so finding the cause is a key part of care.
Symptoms
Some people, especially with a small amount of fluid, have no symptoms. Others notice:
- Shortness of breath, or fast breathing
- Sharp chest pain that is worse on a deep breath or coughing
- A cough
- Fever and chills
- Hiccups
When to see a doctor
See a doctor promptly for new or worsening breathlessness, sharp chest pain on breathing or coughing, or a cough with fever that does not settle. If a chest X-ray has shown fluid, do not wait: the cause needs to be found.
Causes
Fluid collects when it enters the pleural space faster than the body can take it away. Doctors describe two main types:
- Transudative: raised pressure in the blood vessels pushes fluid out. Heart failure is the most common cause, and kidney or liver failure can do the same.
- Exudative: inflammation, infection, lung injury, a tumour, or blocked blood or lymph vessels leak fluid into the space. Pus (empyema) or blood can also collect.
A chest injury or a medical procedure on the chest can also let fluid, blood or air leak in.
Risk factors
- Heart failure, or kidney or liver disease
- Pneumonia and other chest infections
- Cancer
- Autoimmune diseases
- Sickle cell disease
- Smoking and heavy alcohol use, which can lead to heart, lung and liver disease
- Past exposure to asbestos
Complications
A large effusion can press on the lung and make breathing hard. Other problems depend on the cause and include:
- Infected fluid that turns to pus (empyema)
- Scarring or thickening of the lung lining
- A trapped lung that cannot fully expand again
- A collapsed lung (pneumothorax) after fluid is drained with a needle, a risk doctors lower by using
Prevention
Not every effusion can be prevented. These steps lower the risk:
- Having heart, kidney and liver disease treated and followed up as advised
- Not smoking
- Limiting alcohol
Diagnosis
The doctor listens to the lungs and taps the chest, where a large amount of fluid can make a dull sound. Tests may include:
- A chest X-ray, or to show the fluid
- Thoracentesis: a needle is passed between the ribs to take a sample of fluid, which is tested for infection, cancer cells and protein
- Blood tests, including tests of kidney and liver function
- An (heart ultrasound) if heart failure is suspected
- Sometimes a of the lung lining
Treatment
Treatment has three aims: remove the fluid when it is causing symptoms, stop it coming back, and treat the cause.
Thoracentesis draws off fluid with a needle and is used when a large amount causes breathlessness or low oxygen. A chest tube may be left in to drain fluid over several days, often needed for infection or cancer. When fluid keeps returning, a small tube can be left in for regular drainage, or a medicine can be placed in the chest so the two layers stick together (pleurodesis). Surgery is sometimes needed.
Treating the cause matters most. This may mean water tablets (diuretics) and other medicines for heart failure, for infection, or treatment aimed at cancer, kidney disease or liver disease.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Water in the lung always means tuberculosis.”What is true?
Fact
An infection is one possible cause, but it is not the only one. Fluid also collects because of heart failure, which is the most common cause, and because of kidney or liver disease, cancer, and inflammation. Testing the fluid helps to show which cause is behind it.
Myth“Once the fluid has been drained, the problem is cured.”What is true?
Fact
Draining the fluid relieves breathlessness and lets the lung expand, but the fluid can return if the cause is not treated. Care has three aims: remove the fluid, stop it coming back, and treat the illness behind it.
Myth“Taking fluid out with a needle is dangerous, so it is better to avoid it.”What is true?
Fact
When there is a lot of fluid causing breathlessness, draining it brings relief, and testing a sample is the main way to find the cause. There are risks, including a collapsed lung, bleeding, infection and pain, but doctors lower them by using ultrasound to guide the needle.
Myth“If I am not breathless, a little fluid on the X-ray does not matter.”What is true?
Fact
Some people with a small amount of fluid have no symptoms. The fluid is still a sign of another condition, so a doctor needs to find the cause and decide what to do.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
Is water in the lung the same as a pleural effusion?
The term is used loosely. In a pleural effusion the fluid sits in the gap around the lung, between the lung and the chest wall, not inside the lung tissue. A chest X-ray or ultrasound shows where the fluid is.
Is a pleural effusion serious?
It depends on the cause and on how much fluid there is. A small effusion may cause few problems, while a large one can make breathing hard. Because it points to another illness, it should always be looked into.
Does draining the fluid hurt, and is it safe?
The fluid is drawn off with a needle or a thin tube, usually guided by ultrasound, which lowers the risk of problems. Possible risks include a collapsed lung, bleeding, infection and pain. Tell the team straight away if your breathing gets worse afterwards.
Will the fluid come back?
It can, if the cause is not controlled, which is why treating the underlying illness matters. If it keeps returning, options include leaving a small drain in place or a procedure called pleurodesis that makes the two layers stick together.