Please note: This information was current at the time of publication. But medical information is always changing, and some information given here may be out of date. For regularly updated information on a variety of health topics, please visit, the AAFP patient education website.

Information from Your Family Doctor

Pleural Effusion


Am Fam Physician. 2014 Jul 15;90(2):1a.

  See related article on pleural effusion.

What is a pleural effusion?

Pleural effusion (PLUR-al ef-YOO-shun) is when fluid collects in the tissue between your lungs and the wall of your chest.

What causes it?

Pleural effusion can be caused by many different diseases. The most common causes are congestive heart failure, pneumonia, pulmonary embolism (a blood clot in the lung), or cancer.

What are the symptoms?

You might not have any symptoms, or you might feel short of breath, have a cough, or feel pain when you take a deep breath.

How can my doctor tell if I have it?

You may need a chest x-ray or CT scan. Based on your symptoms and the size of the effusion, your doctor may be able to tell what's causing it. If not, you might need a procedure called a thoracentesis (THOR-ah-sen-TEE-sis). Your doctor will put a needle into your chest to drain some of the fluid out. Then the fluid is tested to find out what's causing the pleural effusion.

How is it treated?

If you don't have any symptoms, your doctor might decide to wait and see if it goes away. But if you have symptoms, or if the cause isn't known, it may need to be drained. Your doctor will treat the cause of the effusion to try to prevent it from returning.

This handout is provided to you by your family doctor and the American Academy of Family Physicians. Other health-related information is available from the AAFP online at

This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.


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