Fluid on the lungs in people with cancer (pleural effusion)

Cancer can cause fluid to collect around the lungs. This is called a pleural effusion.

How does fluid build up around the lungs?

There are two sheets of tissue that protect the lungs. They are called pleural membranes (or pleura). In between the pleura is the pleural space. It's normal to have a thin layer of fluid in this space. This helps the lungs to move easily when you breathe in and out.

Cancer cells can spread to the pleura. This causes inflammation of the pleura and makes more fluid. The fluid builds up in the pleural space. This is called a pleural effusion. The increased amount of fluid stops your lungs from expanding fully, you have to take shallower breaths and make more of an effort to breathe.

Diagram showing the pleura and pleural space
Diagram showing a build up of fluid in the lining of the lungs (pleural effusion)

Pulmonary oedema 

If your doctor or nurse talks about fluid on the lung they might mean pleural effusion. Or they might mean you have fluid collecting inside the lung. This is called pulmonary oedema. It is not usually possible to have this fluid drained. Pulmonary oedema is usually caused by heart problems. You might need treatment to stop the fluid collecting.

The information on this page is about pleura effusion. 

Causes of pleural effusion

Cancer is the third most common cause of pleural effusion. The other two main causes are heart failure and pneumonia (a severe chest infection). When cancer is the cause, you might hear doctors call this a malignant pleural effusion.

A malignant pleural effusion is more likely to happen if you have:

  • lung cancer
  • mesothelioma (a type of cancer of the pleura)
  • breast cancer
  • ovarian cancer

Symptoms of a pleural effusion

Feeling breathless may be the first and only symptom you have if you have a pleural effusion. But you may also have a cough and chest pain.

If you suddenly become breathless or your breathing gets worse contact your hospital advice line or GP straight away. If you can't speak to someone quickly go to your local accident and emergency (A&E). You may need urgent treatment.

How is a pleural effusion diagnosed?

Your doctor needs to work out the cause of your symptoms. They will ask about your general health, your medical history and any medication you are taking. They will also want to examine you.

You usually have a chest x-ray or a chest (thoracic) ultrasound scan Open a glossary item (TUS) to diagnose a pleural effusion. Some people may also have a CT scan if doctors need more information about the collection of fluid. These tests show where the fluid is and how much there is.

Coping with shortness of breath when you have a pleural effusion

Shortness of breath from a pleural effusion can be very uncomfortable. You might also feel anxious if you have difficulty breathing.

You might find it more comfortable to sit on the edge of the bed or in an armchair. It might help to lean forward with your arms resting on a pillow on a bed table. This will allow your lungs to expand as fully as possible.

Let your doctor or nurse know if you find it difficult to cope. They will do all they can to help relieve your symptoms and support you. Let family and friends know how you are feeling and accept any offers of help and support.

Treatment for fluid on the lung (pleural effusion)

Doctors treat a pleural effusion by removing the fluid. This should improve your breathing.

Doctors drain the fluid by:

  • pleural aspiration (thoracocentesis)
  • pleural drainage
  • pleurodesis - treatment to seal the space between the tissues covering the lung to stop fluid building up

How long will I be in hospital?

Depending on what procedure you have and how fit you are, you may need to stay in hospital. This might be overnight or longer. Your nurse or doctor will tell you how long you might need to stay in hospital and what you should bring with you.

Pleural aspiration to treat a pleural effusion

Doctors can do a pleural aspiration if there is a small collection of fluid around the lungs. This means using a needle and syringe to remove the fluid. It’s not often used to treat fluid build up caused by cancer. This is because it’s likely the fluid will build up again quite quickly afterwards.

If your doctor thinks this is suitable for you, they usually arrange for you to have this as a day patient. To have this, you sit upright or sit while leaning over the side of a bed. Either way, they make sure you are comfortable before they start.

First, you have an ultrasound scan to locate the fluid. You then have a local anaesthetic Open a glossary item close to the area where the fluid is. This numbs the area. Your doctor makes a small cut into the skin. Using the ultrasound scan they guide a needle attached to a syringe through the cut and into the pleural space to aspirate the fluid.

They then take out the needle and put a plaster over the cut on your skin.

Your doctor sends the fluid or a sample of the fluid to the laboratory. The specialist looks for cancer cells or an infection in the fluid. 

Pleural drainage to treat a pleural effusion

If you have a large collection of fluid you might have a chest drain. 

First, you have an ultrasound scan of the chest. This helps your doctor find the best place to put the chest drain. Then your doctor gives you a small injection of local anaesthetic to numb the area. When the anaesthetic has worked, the doctor makes a small cut into your chest usually through your side. They place a wide needle (cannula) into this cut in your chest.

The tip of the needle goes into the pleural space, where the fluid is collecting. Once it’s in the right place, the doctor attaches the needle to a drainage tube called a chest drain, which in turn is attached to a collecting bottle or bag. Your doctor puts a stitch around the tube to hold it in place. This is a purse string suture.

The anaesthetic can sting at first and the needle can feel uncomfortable for some people. You might also feel some pressure, but it shouldn’t be painful. Let your doctor know if you have any pain. You may need more local anaesthetic.

Diagram showing fluid drainage treatment

As long as the drainage bottle or bag is kept lower than your chest, the fluid drains out automatically. If there is a lot of fluid, this can take several hours. The fluid needs to drain slowly. This is because draining a large amount of fluid too quickly can make your blood pressure drop suddenly making you feel faint. Also, the lung expanding too quickly can make you more breathless. Your nurse will check you regularly while the fluid is draining.

Once the fluid has stopped draining, your doctor or nurse will take the tube out and pull the stitch tight to close the small opening in your chest wall. The stitch stays in for about a week. 

Unfortunately, it is possible for the fluid to build up again. If the fluid keeps coming back, some people might go home with a thin chest tube (indwelling pleural catheter) that stays in place in the chest. It has a valve on the end to stop fluid leaking from it. When the fluid builds up you go to the hospital, the tube is attached to a drainage bottle, and the fluid is drained off. You might be shown how to do this at home with help from your nurse. Your specialist nurse will explain more about this if it is suitable for you. 

Your doctor may suggest you have treatment to stop the fluid coming back. This is called a pleurodesis.

Treatment to stop fluid building up (pleurodesis)

You might have a pleurodesis. This aims to stop fluid from building up and helps to relieve your symptoms.

This treatment seals the space between the tissues covering the lung (pleura). There are a few different substances your doctor can use. One example is sterile talcum powder. These substances inflame the area around the lungs, so they stick together. Then there is no space for fluid to collect. 

You usually stay in hospital for a couple of nights or longer, especially if there is a lot of fluid to drain off first. Draining the fluid can take time and your nurses will want to keep an eye on you. 

This treatment doesn’t treat the cancer. But stopping the fluid building up should make it easier for you to breathe afterwards. You can have this treatment again if it doesn't work completely the first time.

How you have pleurodesis 

There are different ways of having this treatment, depending on whether you need to have fluid drained beforehand. 

Removing fluid and pleurodesis

If you need to have fluid drained from between the pleura beforehand, you have a chest drain put in to remove the fluid as described above.  

Once the fluid has stopped draining, the doctor injects the powder into the pleural space through the drainage tube. They then clamp the tube.

To help spread the powder around the pleural space, you need to lie in different positions. Your doctor will ask you to turn from one side to another. After that, the tube might be attached to some suction. This helps to stick the pleura together.

Having pleurodesis can be uncomfortable. You have painkillers to take beforehand and afterwards. For most people, the soreness is mild and doesn't last long. But do tell your doctor or nurse if it is a problem for you.

Having a pleurodesis using a chest scope (thoracoscopy)

You might have a pleurodesis using a special chest scope if there is no fluid being drained. You usually have this under a general anaesthetic. So, you are asleep during the procedure. 

Your doctor makes one or more small cuts (incisions) in the chest wall. The scope goes into your chest through the cut until it is in the space between the lining of the lung. The doctor can see through the scope, so they know exactly where to put the sterile powder. They put the powder in through a tube in the thorascope. This way of doing pleurodesis is called video assisted thoracoscopy surgery.

Afterwards you may have a chest drain that’s attached to a drainage bottle. This allows any excess fluid that may have accumulated to drain away. It remains in place until there is no more fluid left to drain.  

You usually stay in hospital for about 2 to 3 nights afterwards. Your nurse will show you how to look after the small wounds before you go home. They will also give you a contact number to call if you have any problems or feel unwell when you are at home. 

Diagram showing video assisted thoracoscopy

Possible problems of drainage and pleurodesis

There is a risk of problems or complications after these procedures. Your doctor will make sure the benefits of having fluid drained or pleurodesis outweigh the possible problems. These include:

  • pain
  • bleeding
  • infection
  • injury to the lungs, for example, a collection of air in the pleural space (pneumothorax)
  • blocked drainage tube

After pleurodesis, it's normal to have a raised temperature, and some breathlessness for a couple of days.

Contact your 24 hour advice line or healthcare team straight away if this doesn’t get better or you feel unwell.

Your nurse will explain in more detail how you may feel and what to expect.

Research into draining fluid from the lung

There is ongoing research into ways of draining fluid from the lungs.

The REPEAT trial

In this study, researchers want to find out how long it takes for fluid around the lungs to come back after treatment. To do this, the study team asks people who are having treatment some questions. They will also ask permission from those taking part to use a sample of:

  • their blood from a blood test
  • the fluid that is drained from the pleural effusion

The aim of this study is to look for biomarkers Open a glossary item in the samples. They will try to work out if biomarkers can help them predict when the fluid is starting to build up again.

  • Malignant Pleural Effusion: Diagnosis and Management

    L Ferreiro and others

    Canadian Respiratory Journal. 2020. 

  • Pleural effusion, and Assessment of ascites
    BMJ Best Practice. Accessed June 2023

  • Modern day management of a unilateral pleural effusion

    D Li and others

    Clinical Medicine Journal, 2021

  • Pleural Disease
    D Feller-Kopman and R Light
    New England Journal of Medicine 2018. Volume 378, Issue 740-751

Last reviewed: 
07 Sep 2023
Next review due: 
07 Sep 2026

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