Thoracentesis

Pleural Tap

Results

Thoracentesis is a procedure to remove fluid from the space between the lungs and the chest wall called the pleural space. Results from a lab are usually available in 1 to 2 working days. If the fluid is being tested for an infection, such as tuberculosis, results may not be available for several weeks.

Thoracentesis

Normal:	A small amount of clear, colorless, or pale yellow pleural fluid, usually less than 20 mL (0.7 fl oz), is normally present. No infection, inflammation, or cancer is found.
Abnormal:	A large amount of pleural fluid is present.
	Fluid may be labelled as either a transudate or an exudate. The difference between these two types of fluid has to do with the amount of protein and other substances found in the fluid. A transudate has a low white blood cell (WBC) count, a low lactate dehydrogenase (LDH) enzyme level, and a low protein level. A transudate may be caused by cirrhosis, heart failure, or nephrotic syndrome. An exudate may be caused by diseases, such as infection (pneumonia), chest injury, cancer, pancreatitis, autoimmune disease, or a pulmonary embolism (PE). If an infection is present, the exudate will have a high WBC count, a high LDH enzyme level, a high protein level, and bacteria or other infectious organisms. If cancer is present, the exudate will have a high WBC count (often lymphocytes), a high LDH enzyme level, and a high protein level. Abnormal cells may also be present. If a pulmonary embolism is present, the exudate will have a low WBC count and large numbers of red blood cells. The protein level for a PE may be high or low.

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Author:	Maria G. Essig, MS, ELS Jan Nissl, RN, BS	Last Updated: May 24, 2007
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology
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