Skip Navigation

  • PRINT  | 

What Is Thoracentesis?

Thoracentesis (THOR-ah-sen-TE-sis) is a procedure to remove excess fluid in the space between the lungs and the chest wall. This space is called the pleural space.

Normally, the pleural space is filled with a small amount of fluid—about 4 teaspoons full. Some conditions—such as heart failure, lung infections, and tumors—can cause more fluid to build up. When this happens, it's called a pleural effusion (PLUR-al e-FU-shun). A lot of extra fluid can press on the lungs, making it hard to breathe.


Doctors use thoracentesis to find the cause of a pleural effusion. The procedure also might be done to help you breathe easier.

During the procedure, your doctor inserts a thin needle or plastic tube into the pleural space. He or she draws out excess fluid.

Your doctor may take only the amount of fluid needed to find the cause of the pleural effusion. However, if you have a lot of fluid in your pleural space, he or she may take more. This helps the lungs expand and take in more air, which allows you to breathe easier.

After the fluid is removed from your chest, it's sent for testing. Once the cause of the pleural effusion is known, your doctor will plan treatment. For example, if an infection is causing the excess fluid, your doctor may prescribe antibiotics. If the cause is heart failure, you'll be treated for that condition.

Thoracentesis usually takes 10–15 minutes. It may take longer if you have a lot of fluid in your pleural space. You'll be watched for up to a few hours after the procedure for complications.


Thoracentesis usually doesn't cause serious problems, but some risks are involved. Risks include:

  • Pneumothorax (noo-mo-THOR-aks), or a collapsed lung
  • Pain, bleeding, bruising, or infection at the spot where the needle or tube was inserted
  • Liver or spleen injury (very rare)

Sometimes these problems get better on their own. If not, your doctor will likely prescribe treatment.

Rate This Content:
Last Updated: February 24, 2012