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What is thoracentesis?

Thoracentesis is a procedure to remove extra fluid from around the lungs. Normally the lungs fill up a person's chest. But fluid can build up between the outside of the lungs and the inside of the chest. This space (called the pleural space) often has only a very small amount of fluid that lubricates these surfaces. But if extra fluid builds up in this space, the lung can't inflate fully. Excess fluid in the pleural space is called pleural effusion. This reduces lung function and makes it harder to breathe.

During a thoracentesis, a needle is put through the skin of the chest into the pleural space. This drains the extra fluid.

Why might I need thoracentesis?

Thoracentesis is done to remove the extra fluid when it's causing symptoms, such as trouble breathing. Or it's done to find the cause of a pleural effusion.

Many conditions can cause a pleural effusion. A thoracentesis may be needed to find the cause. When the fluid is drained from around the lung it's then examined in a lab.

Thoracentesis can help diagnose health problems, such as:

  • Congestive heart failure, the most common cause of pleural effusion

  • Viral, fungal, or bacterial infections. One example of an infection causing pleural effusion is empyema. Tuberculosis is another infection that can cause a pleural effusion.

  • Cancer

  • Systemic lupus erythematosus and other autoimmune disease

  • Inflammation of the pancreas (pancreatitis)

  • A blood clot in the lung (pulmonary embolism)

  • Liver failure

  • 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)

  • 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 about any concerns you have.

Thoracentesis shouldn't 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 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 isn't clear.

Tell your 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, herbs, and other 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 advised by your provider

  • Plan to have someone drive you home from the hospital

  • Follow any other directions your 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 these tests:

  • 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 may 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, 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, breathe out 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 -1 to 2 days. 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 OK.

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 advised by your provider. You may need to not do strenuous physical activity for a few days.

Call your provider if any of these occur:

  • Fever of 100.4°F (38°C) or higher, or as advised by your provider

  • 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 provider may give you other directions after the procedure.

Next steps

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

  • The name of the test or procedure

  • The reason you are having the test or procedure

  • What results to expect and what they mean

  • The risks and benefits of the test or procedure

  • What the possible side effects or complications are

  • When and where you are to have the test or procedure

  • Who will do the test or procedure and what that person’s qualifications are

  • What would happen if you did not have the test or procedure

  • Any alternative tests or procedures to think about

  • When and how will you get the results

  • Who to call after the test or procedure if you have questions or problems

  • How much will you have to pay for the test or procedure

Online Medical Reviewer: Andrew D Schriber MD
Online Medical Reviewer: Jessica Gotwals BSN MPH
Online Medical Reviewer: Marianne Fraser MSN RN
Date Last Reviewed: 5/1/2022
© 2000-2024 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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