Pleural fluid analysis examines fluid that has collected in the pleural space. The pleura is a thin membrane that lines the outside of the lung and the inside of the chest cavity.

A build up of fluid between the layers of the pleura is called a pleural effusion.

A sample of pleural fluid is obtained by a procedure called thoracentesis. The specimen is examined for chemical content, cellular composition, the presence of malignant cells, and the presence of microorganisms.

There is no special preparation. Do not cough, breathe deeply, or move during the test to avoid injury to the lung. A chest x-ray may be performed before or after the test. Your doctor will probably want to observe you for 30-60 minutes after the procedure to see if a complication occurs.

You will be positioned sitting on the edge of a chair or bed with your head and arms resting on a table. The skin around the insertion site is disinfected, and the area is draped. A local anesthetic is injected into the skin.

The thoracentesis needle is inserted above the rib into the pocket of fluid. There will be a stinging sensation when the local anesthetic is injected, and a sensation of pressure when the needle is inserted into the pleural space. Inform your health care provider if you develop sharp chest pain or shortness of breath.