Health Encyclopedia


What is thoracentesis?

Thoracentesis is a procedure to remove fluid or air from around the lungs. A needle is put through the chest wall into the pleural space. The pleural space is the thin gap between the pleura. The pleura are a double layer of membranes that surrounds the lungs. Inside the space is a small amount of fluid. The fluid prevents the pleura from rubbing together when you breathe. Excess fluid in the pleural space is called pleural effusion. When this happens, it’s harder to breathe because the lungs can’t inflate fully. This can cause shortness of breath and pain. These symptoms may be worse with physical activity.

Why might I need thoracentesis?

Thoracentesis may be done to find the cause of pleural effusion. It can also be done to treat symptoms of pleural effusion by removing fluid. The fluid is then examined in a lab.

Thoracentesis can help diagnose health problems such as:

  • Congestive heart failure (CHF) (most common cause of pleural effusion)
  • Viral, fungal, or bacterial infections
  • Cancer
  • Systemic lupus erythematosus (SLE), an autoimmune disease
  • Inflammation of the pancreas (pancreatitis)
  • A blood clot in the lung (pulmonary embolism)
  • An area of pus in the pleural space (empyema)
  • Liver failure
  • High blood pressure in lung blood vessels (pulmonary hypertension)
  • Tuberculosis (TB)
  • Pneumonia
  • Reactions to medicines

Your healthcare provider may have other reasons to advise thoracentesis.

What are the risks of thoracentesis?

All procedures have some risks. The risks of this procedure may include:

  • Air in the space between the lung covering (pleural space) that causes the lung to collapse (pneumothorax)
  • Fluid in the lungs (pulmonary edema )
  • Bleeding
  • Infection
  • Liver or spleen injury (rare)

Your risks may vary depending on your general health and other factors. Ask your healthcare provider which risks apply most to you. Talk with him or her about any concerns you have.

Thoracentesis should not be done in people with certain bleeding conditions.

How do I get ready for thoracentesis?

Your healthcare provider will explain the procedure to you. Ask him or her any questions you have. You may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully. Ask questions if anything is not clear.

Tell your healthcare provider if you:

  • Are pregnant or think you may be pregnant
  • Are sensitive to or allergic to any medicines, latex, tape, or anesthetic medicines (local and general)
  • Take any medicines, including prescriptions, over-the-counter medicines, vitamins, and herbal supplements
  • Have had a bleeding disorder
  • Take blood-thinning medicine (anticoagulant), aspirin, or other medicines that affect blood clotting

Make sure to:

  • Stop taking certain medicines before the procedure, if instructed by your healthcare provider
  • Plan to have someone drive you home from the hospital
  • Follow any other instructions your healthcare provider gives you

You may have imaging tests before the procedure. These are done to find the location of the fluid to be removed. You may have any of the below:

  • Chest X-ray
  • Chest fluoroscopy
  • Ultrasound
  • CT scan

What happens during thoracentesis?

You may have your procedure as an outpatient. This means you go home the same day. Or it may be done as part of a longer stay in the hospital. The way the procedure is done may vary. It depends on your condition and your healthcare provider's methods. In most cases, a thoracentesis will follow this process:

  1. You may be asked to remove your clothes. If so, you will be given a hospital gown to wear. You may be asked to remove jewelry or other objects.
  2. You may be given oxygen through a nasal tube or face mask. Your heart rate, blood pressure, and breathing will be watched during the procedure.
  3. You will be in a sitting position in a hospital bed. Your arms will be resting on an over-bed table. This position helps to spread out the spaces between the ribs, which is where the needle is inserted. If you are not able to sit, you may lie on your side on the edge of the bed.
  4. The skin where the needle will be put in will be cleaned with an antiseptic solution.
  5. A numbing medicine (local anesthetic) will be injected in the area.
  6. When the area is numb, the healthcare provider will put a needle between the ribs in your back. You may feel some pressure where the needle goes in. Fluid will slowly be withdrawn into the needle.
  7. You will be asked to hold still, exhale deeply, or hold your breath at certain times during the procedure.
  8. If there is a large amount of fluid, tubing may be attached to the needle. This will let the fluid drain more. The fluid will drain into a bottle or bag. In some cases, a flexible tube (catheter) will be put in place of the needle and the tubing will be attached for a day or two. You will stay in the hospital until the catheter is removed.
  9. When enough fluid has been removed, the needle will be taken out. A bandage or dressing will be put on the area.
  10. Fluid samples may be sent to a lab.
  11. You may have a chest X-ray taken right after the procedure. This is to make sure your lungs are okay.

What happens after thoracentesis?

After the procedure, your blood pressure, pulse, and breathing will be watched. The dressing over the puncture site will be checked for bleeding or other fluid. If you had an outpatient procedure, you will go home when your healthcare provider says it’s OK. Someone will need to drive you home.

At home, you can go back to your normal diet and activities if instructed by your healthcare provider. You may need to not do strenuous physical activity for a few days.

Call your healthcare provider if you have any of the below:

  • Fever of 100.4°F (38°C) or higher
  • Redness or swelling of the needle site
  • Blood or other fluid leaking from the needle site
  • Feeling short of breath
  • Trouble breathing
  • Chest pain

Your healthcare provider may give you other instructions after the procedure.

Next steps

Before you agree to the test or the procedure make sure you know:

  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure

Medical Reviewers:

  • Foster, Sara M., RN, MPH
  • Jones, Niya, MD