MedlinePlus Medical Encyclopedia: Pleural fluid analysis

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Pleural fluid analysis

Contents of this page:
Definition How the test is performed How to prepare for the test How the test will feel Why the test is performed	Normal Values What abnormal results mean What the risks are Special considerations

Definition

Pleural fluid analysis examines fluid that has accumulated in the pleural space. The pleura is a thin membrane that lines the outside of the lung and the chest cavity. An accumulation of fluid between the layers of the pleura is called a pleural effusion.

How the test is performed

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.

How to prepare for the test

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.

Infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:

Infant test or procedure preparation (birth to 1 year)
Toddler test or procedure preparation (1 to 3 years)
Preschooler test or procedure preparation (3 to 6 years)
Schoolage test or procedure preparation (6 to 12 years)
Adolescent test or procedure preparation (12 to 18 years)

How the test will feel

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.

Why the test is performed

The test is performed to determine the cause of a pleural effusion.

Normal Values

With normal values, the pleural cavity contains less than 20 milliliters (four teaspoons) of serous (clear, yellowish) fluid.

What abnormal results mean

With abnormal results, the analysis of the fluid will indicate possible causes of pleural effusion, such as infection, neoplasms, heart failure, and cirrhosis. If infection is suspected, a culture of the fluid is done to determine the presence of microorganisms.

Another condition under which the test may be performed is hemothorax, a collection of blood in the pleura.

What the risks are

The risks of thoracentesis are pneumothorax (collapse of the lung), fluid re-accumulation, pulmonary edema, excessive loss of blood, infection, and respiratory distress. Serious complications are uncommon.

Special considerations

The fluid analysis cost and the cost of the procedure to obtain the specimen are charged separately.

Update Date: 1/27/2004

Updated by: Allen J. Blaivas, D.O., Division of Pulmonary, Critical Care, and Sleep Medicine, University Hospital, Newark, NJ. Review provided by VeriMed Healthcare Network.

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