What is a thoracentesis?

A thoracentesis is a procedure that removes fluid from the space between your lungs and your chest wall (pleural space).

Why is it done?

There are many reasons, such as:

  • Recent fluid build-up with no clear cause.

  • To help diagnose an infection.

  • To help diagnose cancer.

  • To remove fluid and help the patient breathe easier.

How is it done?

You will most likely be in a sitting position with your arms and head resting on your bedside table. If you cannot sit upright, we will place you on your side, with the side that needs to be drained facing up towards the ceiling. Your top arm will be placed over your head to make it easier to place the needle.

The skin around the site will be cleaned and sterile drapes will be placed around the site. We will inject numbing medicine into your skin to lessen the pain.

We will place a needle or thin, plastic tube between the ribs and into the chest. We will remove a small sample of fluid for testing.

This test helps the doctor figure out what may be causing the fluid build-up in the spaces around the lungs.

If you have excess fluid in your chest, the doctor may remove some of it to ease pain and improve breathing.

At the end of the procedure, you may cough as your lungs start to fully inflate again. This can last for an hour or so. You should keep a dressing or Band-Aid® on the site for the next 24 hours.

You may have a chest x-ray after the procedure. The chest x-ray is taken to see if you have a buildup of air outside the lung. This is rare but may need further attention.


The procedure should not cause serious problems, but some risks are involved. These include:

  • Pain – You may feel a poke as the doctor inserts the needle into the chest. We use numbing drugs to lessen the pain. Once the needle is in, the pain is often mild and goes away.

  • Bleeding – When the doctor inserts the needle, there is a risk of nicking a blood vessel. If this happens, the bleeding is often minor and stops on its own. You may notice a bruise. Rarely, bleeding can occur in or around the lungs and require surgery.

  • Collapsed lung – Rarely, the needle punctures the lung. Most often, the small hole seals over quickly by itself. If not, air can build-up around the lung and cause it to collapse. If this occurs, the doctor may need to insert a chest tube to drain air from around the lung.

After the Procedure

You can go back to your normal routine as you are able. Call your local doctor if you start to have early symptoms of fluid buildup again. Sometimes, the fluid will build up again, and you may need to have another thoracentesis.

When to Call

  • If you feel dizzy, faint or light-headed.

  • If your pain around the site gets worse rather than better 2-3 days later.

  • If you feel sick and have a fever over 100.4° F (38° C).

  • If you start to have redness and swelling around the site.

If you have shortness of breath, or cannot catch your breath, or have a persistent cough with or without the presence of blood, you need to go the nearest emergency room.

Who to Call

Any questions or concerns you may have about your procedure please call 1-800-323-8942.

This will give you the paging operator. Ask for the Ultrasound Department. The operator will then connect you to someone in our department who can help.