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Fluid on the lung (pleural effusion)

Find out how cancer can cause fluid build up in the lungs and how it might affect you.

Fluid on the lungs is called a pleural effusion. Cancer can sometimes cause this build up of fluid. It makes you short of breath and make you uncomfortable. Treatment is usually to drain the fluid which makes you less breathless and more comfortable.

Where the fluid builds up

The outside of the lung is protected by 2 sheets of tissue. They are called pleural membranes (pleura). The space between the 2 layers of tissue (pleura) is called the pleual space. 

The pleura gets inflamed by cancer cells and this makes fluid. The fluid takes up space where your lungs should be. It stops your lungs from expanding fully. So you have to take shallower breaths and make more effort to breathe. 

Doctors call the fluid collection a pleural effusion.

Diagramshowing the pleura and pleural space
Diagram showing the pleura and pleural effusion

The fluid stops the lung from fully expanding when you breathe. So as it builds up, the collected fluid causes shortness of breath.


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. Lean forward with your arms resting on a pillow on a bed table to allow your lungs to expand as fully as possible.

Let your doctor or nurse know if you find it difficult to cope. They can prescribe medicines to help you.


Your doctor can put in a tube for a short time to drain the fluid and help you breathe more easily.

You can also have treatment to stop the fluid from building up and help relieve symptoms. This treatment is called pleurodesis.

Last reviewed: 
26 Oct 2014
  • Principles and practice of oncology (10th edition)
    VT De Vita, S Hellman and SA Rosenberg
    Lippincott, Williams and Wilkins, 2015

  • Pleural effusion
    British Medical Journal (BMJ) Best Practice Online. July 2016

  • Assessment and nursing care of the patient with dyspnoea
    Prigmore S
    Nursing Times (2005) Vol: 101, Issue: 14, Page no: 50

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