A pleural effusion is a buildup of fluid in the space between the lungs and the chest wall. This space is called the pleural space. Thoracentesis is a procedure to remove fluid from this area.
There are 2 types of thoracentesis:
There is always a small amount of fluid in the pleural space. The fluid helps to lubricate the area. When too much fluid builds up in this space, it can make it difficult to breathe.
Some of the fluid may be tested after it is removed. The buildup of fluid can be a symptom of diseases or disorders, such as:
Problems from the procedure are rare, but all procedures have some risk. Your doctor will review potential problems, like:
Factors that may increase the risk of complications include:
A local anesthetic will be used. It will numb the area where the needle will be inserted.
You may be asked to sit upright on the edge of a bed or chair. Your arms will be resting on a nearby table. If your procedure involves a CT scan, you may be asked to lie on a table. Try to avoid coughing, breathing deeply, or moving during the procedure.
A small patch of skin on your back, chest, or under your armpit will be sterilized. Anesthesia will be applied to this patch. It will help numb the area.
Ultrasound or CT scan images may be used to guide the needle and monitor the fluid. A needle or thin plastic catheter will be inserted between your ribs. The needle or catheter is then passed into the pleural space. Some or most of the fluid will be drawn into the syringe.
Placement of Thoracentesis Needle
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About 15 minutes
You may feel slight pain or a stinging when the needle is first inserted. As the fluid is being extracted, you may feel a sense of pulling. Tell your healthcare team if you feel extreme pain, any shortness of breath, or lightheadedness.
If the thoracentesis is being done for diagnostic reasons, the fluid will be sent to a lab for testing. Often, another chest x-ray will be done to ensure that the fluid has been removed and that there is no sign of a collapsed lung.
Treatment may be started for the cause of the fluid buildup.
You may have your activity restricted during your recovery.
If a diagnostic thoracentesis was done, ask your doctor when to expect the results.
Follow your doctor's instructions.
After arriving home, contact your doctor if any of the following occurs:
If you think you have an emergency, call for medical help right away.
American Lung Association
American Thoracic Society
The Canadian Institutes of Health Information
The Lung Association
How to Do Thoracentesis. The Merck Manual Professional Edition website. Available at:
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Updated October 2016. Accessed February 12, 2018.
Thoracentesis. American Thoracic Society. Available at: https://www.thoracic.org/patients/patient-resources/resources/thoracentesis.pdf. Updated February 2016. Accessed February 12, 2018.
Thoracentesis. Johns Hopkins Medicine website. Available at:
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Accessed February 12, 2018.
Thoracentesis. National Heart Lung and Blood Institute website. Available at: https://www.nhlbi.nih.gov/health/health-topics/topics/thor. Accessed February 12, 2018.
6/3/2011 DynaMed Plus Systematic Literature Surveillance http://www.dynamed.com/topics/dmp~AN~T905141/Treatment-for-tobacco-use : Mills E, Eyawo O, et al. Smoking cessation reduces postoperative complications: A systematic review and meta-analysis. Am J Med. 2011;124(2):144-154.
Last reviewed March 2018 by
EBSCO Medical Review Board
David A. Ostrovsky, MD
Last Updated: 3/15/2013