Thoracentesis is a procedure to remove fluid from the space between the lining of the outside of the lungs (pleura) and the wall of the chest.
Pleural fluid aspiration; Pleural tap
Why the Test is Performed
Normally, very little fluid is in the pleural space. A buildup of too much fluid between the layers of the pleura is called a pleural effusion.
The test is performed to determine the cause of the extra fluid, or to relieve symptoms from the fluid buildup.
How the Test is Performed
A small area of skin on your chest or back is washed with a sterilizing liquid. Some numbing medicine (local anesthetic) is injected in this area.
A needle is placed through the skin of the chest wall into the space around the lungs, called the pleural space. Fluid is collected and may be sent to a laboratory for testing (pleural fluid analysis).
How to Prepare for the Test
No special preparation is needed before the test. A chest x-ray may be performed before and after the test.
Do not cough, breathe deeply, or move during the test to avoid injury to the lung.
How the Test Will Feel
You will sit on a bed or on the edge of a chair or bed. Your head and arms will rest on a table.
The skin around the procedure site is cleaned and the area is draped. A local numbing medicine (anesthetic) is injected into the skin. The thoracentesis needle is inserted above the rib into the pleural space.
You will feel a stinging sensation when the local anesthetic is injected. You may feel pressure when the needle is inserted into the pleural space.
A chest x-ray is often done after the procedure to detect possible complications.
Normally the pleural cavity contains only a very small amount of fluid.
What Abnormal Results Mean
Testing the fluid will help your health care provider determine the cause of pleural effusion. Possible causes include:
If your health care provider suspects that you have an infection, a culture of the fluid may be done to test for bacteria.
The test may be also performed for the following conditions:
Reviewed By: Benjamin Medoff, MD, Assistant Professor of Medicine, Harvard Medical School, Pulmonary and Critical Care Unit, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.