- Cancerous (malignant) cells
- Other types of cells (for example blood cells)
- Levels of glucose, protein and other chemicals
- Bacteria, fungi, viruses, and other germs that can cause infections
- Heart failure
- Severe malnutrition
- Abnormal connections between the pleural space and other organs (for example, the esophagus)
- Collapsed lung (pneumothorax)
- Excessive loss of blood
- Fluid re-accumulation
- Pulmonary edema
- Respiratory distress
Pleural fluid analysis is a test that examines a sample of fluid that has collected in the pleural space. This is the space between the lining of the outside of the lungs (pleura) and the wall of the chest. When fluid collects in the pleural space, the condition is called 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:
How to Prepare for the Test
No special preparation is needed before the test. A chest x-ray will be performed before and after the test.
DO NOT cough, breathe deeply, or move during the test to avoid injury to the lung.
Tell your provider if you take medicines to thin the blood.
How the Test will Feel
For thoracentesis, you sit on the edge of a chair or bed with your head and arms resting on a table. The provider cleans the skin around the insertion site. Numbing medicine (anesthetic) is injected into the skin.
A needle is placed through the skin and muscles of the chest wall into the pleural space. As fluid drains into a collection bottle, you may cough a bit. This is because your lung re-expands to fill the space where fluid had been. This sensation lasts for a few hours after the test.
During the test, tell your provider if you have sharp chest pain or shortness of breath.
The provider may use ultrasound to get a better view of the fluid in your chest.
Why the Test is Performed
The test is performed to determine the cause of a pleural effusion. It is also done to relieve the shortness of breath that a large pleural effusion can cause.
Normally the pleural cavity contains less than 20 milliliters (4 teaspoons) of clear, yellowish (serous) fluid.
What Abnormal Results Mean
Abnormal results may indicate possible causes of pleural effusion, such as:
If the provider suspects an infection, a culture of the fluid is done to check for bacteria.
The test may also be performed for hemothorax. This is a collection of blood in the pleura.
Risks of thoracentesis are:
Serious complications are uncommon.
Broaddus VC, Light RW. Pleural effusion. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 79.
Kosowsky JM, Kimberly HH. Pleural disease. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2014:chap 77.
- Review date:
- December 07, 2016
- Reviewed by:
- Denis Hadjiliadis, MD, MHS, Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2008 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.