Fluid in the Chest (Pleural Effusion)

What Is Pleural Effusion?

Pleural effusion, also called “water on the lung,” is an excessive buildup of fluid between your lungs and chest cavity. There’s always a small amount of liquid inside your lungs. This fluid works to coat the membranes (pleura) that line the outside of your lungs and lubricate the chest cavity to aid in breathing. 

Certain medical conditions can cause this fluid to build up between the chest cavity and your lungs.

How Does Pleural Effusion Develop?

Causes Icon

The pleura creates too much fluid when it’s irritated or infected. This fluid accumulates in the chest cavity outside the lung, causing what’s known as pleural effusion. 

Certain types of cancer, such as lung, breast, and ovarian cancers, can cause pleural effusions. Lymphoma and mesothelioma can cause them too. Fluid also may build up as a result of certain cancer treatments, such as radiation therapy or chemotherapy.

Did You Know?
According to the Cleveland Clinic, pleural effusion is a common condition, with more than 100,000 cases diagnosed in the United States each year.
  • Other causes of pleural effusions include:
  • congestive heart failure
  • cirrhosis (poor liver function)
  • pulmonary embolism (blockage in the lung arteries caused by a blood clot)
  • post-open-heart surgery
  • pneumonia
  • severe kidney disease

Find out if you're at risk for pulmonary arterial hypertension »

Symptoms and Signs of Pleural Effusion

Symptoms Icon

Some people show no symptoms of pleural effusion. These people usually find out they have the condition through chest X-rays or physical examinations ordered for another reason. 

  • Common symptoms of pleural effusion include:
  • dry cough
  • fever
  • difficulty breathing when lying down
  • chest pain
  • shortness of breath

See your doctor immediately if you have symptoms of pleural effusion.

Diagnosing Pleural Effusion

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Your doctor will perform a physical examination and listen to your lungs with a stethoscope. They may also order a chest X-ray to help diagnosis pleural effusion, or one of the following tests:

  • CT scan
  • chest ultrasound
  • pleural fluid analysis (or thoracentesis)

In a pleural fluid analysis, your doctor will remove fluid from the pleural membrane area by inserting a needle into the chest cavity and suctioning the fluid into a syringe. They’ll then test the fluid for the presence of protein or cancer cells. Another name for this test is thoracentesis.

Your doctor may schedule a thoracoscopy if they suspect you have pleural effusion, but they’re unable to diagnose it with these tests. A thoracoscopy is a surgical procedure that lets the doctor see inside the chest cavity using a fiber-optic camera. 

Your doctor will make a few small incisions in the chest area while you’re under general anesthesia. Then they’ll insert the camera through one incision and the surgical tool through the other to extract a small amount of fluid or tissue for analysis.

Treating Pleural Effusion

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The underlying cause of the condition and the severity of the effusion will determine treatment.

Draining Fluid

Generally, treatment involves draining the fluid from the chest cavity, either with a needle or a small tube inserted into the chest. You’ll receive a local anesthetic before this procedure, which will make the treatment painless. However, you may feel some pain or discomfort at the incision site after the anesthetic wears off. Most doctors will prescribe medication to help relieve pain. You may need this treatment more than once if fluid re-collects.

Other treatments may be necessary to manage fluid buildup if cancer causes pleural effusion.


Pleurodesis is a treatment that occurs after drawing excess fluid out of the chest cavity. When the fluid is removed, a doctor injects a drug (typically talc) into the area. This causes the two layers of the pleura to stick together and prevents the buildup of fluid between the two layers. 


In more serious cases, a doctor surgically inserts a shunt (small tube) into the chest cavity. This helps redirect the fluid from the chest to the abdomen, where it can be easily removed. Pleurectomy, in which part of the pleural lining is surgically removed, is also an option in very severe cases.


Treatment for minor cases of pleural effusion is minimally invasive. Most people recover within a few days. Minor complications from treatment include slight pain and discomfort, which often go away with time. Some cases of pleural effusion can have more serious complications, depending on the severity of the condition and treatment used. 

Serious complications include:

  • pulmonary edema or fluid in the lungs, which can result from draining too much fluid through thoracentisis
  • partial collapsed lung
  • infection or bleeding
  • low blood pressure, which can result from draining fluid too rapidly
  • shock

These complications, while serious, are very rare. Your doctor will help determine the most effective treatment option, and will discuss the benefits and risks of each procedure.

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