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A thoracentesis is a medical procedure that involves the insertion of a needle or catheter into the chest to remove excess fluid or air from the pleural space, the area between the lungs and the chest wall.

The length of time a thoracentesis takes varies depending on the amount of fluid or air that needs to be removed, but it typically takes an hour.

Most people experience some discomfort during a thoracentesis, but the procedure is typically well-tolerated. Local anesthesia is used to numb the area where the needle or catheter is inserted, so there may be a small amount of discomfort from the needle used to inject the anesthetic.

Common diagnoses made by a thoracentesis include:

  • Pleural effusion, which is a buildup of fluid in the pleural space that can be caused by a variety of conditions, including heart failure, pneumonia, and cancer.

  • Pneumothorax, which is the presence of air in the pleural space that can cause the lung to collapse. This can be caused by injury or underlying lung disease.

  • Empyema, which is a collection of pus in the pleural space that can be caused by bacterial infection.

  • Lung cancer, which can cause pleural effusion or other abnormalities in the pleural space.


Possible complications:

● Pain – Where the needle is inserted. Using a local anesthetic helps to reduce the pain. Pain generally resolves once the needle is removed.


● Feeling faint – Some people may feel faint or dizzy during or after the procedure. 


● Bleeding – A blood vessel may be punctured when the needle is inserted through the skin and chest wall, causing bleeding. The bleeding is usually minor and stops on its own, although it may cause bruising around the puncture site. In rare cases, there may be bleeding into or around the lung, requiring drainage of blood collected in the chest by insertion of a catheter or surgery.


● Infection – Infection can develop if bacteria are introduced by the needle puncture. It is done in a sterile field to minimize chance of infection. 


● Pneumothorax or collapsed lung – Occasionally, the needle used to obtain a fluid sample can puncture the lung. The hole created by the puncture usually seals quickly on its own. If it does not, air can build up around the lung, causing the lung to collapse. This is called a pneumothorax. When a pneumothorax occurs, a chest tube may be used to drain the air from the pleural space and allow the lung to re-expand.


Pneumothoraces that do occur are usually small and resolve on their own. About a third of pneumothoraces become large, continue to expand, or cause shortness of breath. In these patients, a  chest tube is placed through the skin into the pleural space to withdraw the air.


● Liver or spleen puncture – In very rare cases, the liver or spleen may be punctured during thoracentesis. 


● Pulmonary edema – Rarely after thoracentesis, a person can experience pulmonary edema, which is the sudden collection of fluid within the lung on the side of the chest where the thoracentesis was performed. Some people may experience shortness of breath or cough, but usually recover quickly.

See the Handout on Thoracentesis for more information.

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