__NOTOC__An exudate is any
fluidthat filters from the circulatory systeminto lesions or areas of inflammation. Its composition varies but generally includes water and the dissolved solutes of the blood, some or all plasma proteins, white blood cells, platelets and (in the case of local vascular damage) red blood cells.
Exudate is derived from "exude", "to ooze," [cite web |url=http://www.merriam-webster.com/dictionary/exuded |title="Exuded" Merriam-Webster Online Dictionary |accessdate=2008-07-04 |date=2008 |publisher=
Meriam Webster] from the Latin "exsūdāre", "to (ooze) out like sweat" ("ex-" "out" and "sūdāre" "to sweat"). [cite book |title=Chambers Dictionary of Etymology |editor=Robert K. Barnhart |year=1988 |publisher=Chambers Harrap Publishers |location=New York |isbn=0-550-14230-4 |pages=363]
Pusis an example of exudate found in infected wounds that also includes bacteriaand high concentrations of white blood cells. Clear blister fluid is an example of an exudate that contains water (and solutes) together with some plasma proteins, but not many blood cells.
*Serous exudate is usually seen in mild inflammation, with little protein content. Its consistency resembles that of serum, and can usually be seen in certain disease states like
*Purulent or suppurative exudate consists of plasma with both active and dead
neutrophils, fibrinogen, and necroticparenchymal cells. This kind of exudate is consistent with more severe infections, and is commonly referred to as pus.
*Fibrinous exudate is composed mainly of
fibrinogenand fibrin. It is characteristic of rheumatic carditis, but is seen in all severe injuries such as strep throatand bacterial pneumonia. Fibrinous inflammation is often difficult to resolve due to the fact that blood vessels grow into the exudate and fill the space that was occupied by fibrin. Often, large amounts of antibiotics are necessary for resolution.
*Hemorrhagic exudate is seen in injury that causes rupture of blood vessels.
*Pleural exudate has a
specific gravitygreater than 1.020. Certain conditions produce exudative pleural effusions such as infections, pulmonary infarctions, rheumatoid arthritis, lupus erythematosus, and certain malignancies.
*Catarrhal exudate is seen in the nose and throat and is characterized by a high content of mucus.
Exudates vs. transudates
There is an important distinction between
transudatesand exudates. Transudates are caused by disturbances of hydrostatic or colloid osmotic pressure, not by inflammation. Medical distinction between transudates and exudates is through the measurement of the specific gravityof extracted fluid. Specific gravity is used to measure the protein content of the fluid. The higher the specific gravity, the greater the likelihood of capillarypermeability changes in relation to body cavities. For example, the specific gravity of the transudate is usually less than 1.012 and a protein content of less than 2 gm/100mL (2 gm%).
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