Definition of Pleural fluid analysis:

Pleural fluid analysis examines fluid that has collected in the pleural space -- the small area between the membranes that line the lungs.

See also: Pleural effusion

How the test is performed:

A procedure called thoracentesis is used to get a sample of pleural fluid. The health care provider examines the sample to look for:

• Cancerous (malignant) cells
• Cellular makeup
• Chemical content
• Tiny organisms that can cause disease (microorganisms)

How to prepare for the test:

The test is no more invasive than having blood drawn. There is no special preparation. Do not cough, breathe deeply, or move during the test to avoid injury to the lung. You may have a chest x-ray before or after the test.

How the test will feel:

You will sit on the edge of a chair or bed with your head and arms resting on a table. The health care provider will clean the skin around the insertion site and drape the area. A local pain-killing medicine (anesthetic) is injected into the skin, which stings a bit, but only for a few seconds.

The thoracentesis needle is inserted above the rib into the pocket of fluid. As fluid drains into a collection bottle, many people cough a bit as the lung reexpands to fill the space where fluid had been. This sensation normally lasts for a few hours after the test is completed. Tell your health care provider if you have sharp chest pain or shortness of breath.

Why the test is performed:

The test is performed to determine the cause of a pleural effusion, and to relieve the shortness of breath that a large pleural effusion can cause.