What is Cell Count - Pleural fluid ?

The exterior surface of your lungs and thoracic cavity is lined with a continuous membrane known as the pleura. Pleural fluid is layered between the two surfaces so that the opposing surfaces “glide” across each other during breathing. This “gliding” movement helps with normal breathing. In healthy individuals, there are about 10 to 20 milliliters of pleural fluid that is evenly distributed across the pleura and it is continually replenished from the blood in the tiny blood vessels (capillaries) in your lungs. Certain diseases will increase the pleural volume, usually as a pocket or collection. In these cases, it should be tested and, if necessary, drained.

A variety of conditions and diseases can cause inflammation of these membranes (pleuritis) and/or excessive buildup of pleural fluid (pleural effusion). Pleural fluid testing evaluates this liquid to determine the cause of the increased fluid.

The two main reasons for fluid buildup in the pleural space are:

• An imbalance between the pressure of the liquid within your blood vessels, which drives fluid out of blood vessels, and the amount of protein in your blood, which keeps fluid in blood vessels. The fluid that accumulates, in this case, is called a transudate. This type of fluid more commonly involves both sides of your chest and is most frequently a result of either congestive heart failure or cirrhosis.
• An injury to or inflammation of the pleurae, in which case the fluid that accumulates is called an exudate. It more commonly involves one side of your chest. Exudates are associated with a variety of conditions and diseases, including:
• Infections—caused by viruses, bacteria, or fungi. Infections may start in the pleurae or spread there from other places in your body. For example, pleuritis and pleural effusion may occur along with or following pneumonia.
• Bleeding—bleeding disorders, trauma, or blockage in a lung artery (pulmonary embolism) can lead to blood in your pleural fluid.
• Inflammatory conditions—such as lung diseases, chronic lung inflammation for example due to prolonged exposure to large amounts of asbestos (asbestosis), sarcoidosis, or autoimmune disorders such as rheumatoid arthritis and lupus
• Malignancies—such as lymphoma, leukemia, lung cancer, metastatic cancers
• Other conditions—examples include unknown (idiopathic), heart bypass surgery, heart or lung transplantation, pancreatitis, or abscesses within the abdomen

Determining the type of fluid present is important because it helps to shorten the list of possible causes of your pleural effusion. Healthcare practitioners and laboratory professionals use an initial set of tests (cell count, protein, albumin, and lactate dehydrogenase (LD) level, and appearance of the fluid) to distinguish between transudates and exudates; part of this evaluation is the collection of a blood specimen to compare levels between blood and effusion. If the fluid is an exudate, additional tests may be performed to further pinpoint the disease or condition causing your pleuritis and/or pleural effusion.