Normal Values:

Normally the pleural cavity contains less than 20 milliliters (4 teaspoons) of clear, yellowish (serous) fluid.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean:

Abnormal results may indicate possible causes of pleural effusion, such as:

• Cancer (neoplasm)
• Cirrhosis
• Heart failure
• Infection

If the health care provider suspects an infection, a culture of the fluid is done to check for microorganisms.

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