Pleura is a thin membrane that covers the surface of the lungs and the inside of the chest wall, encompassing the pleural space. It is normal for this space to have some fluid (about 10 to 20 ml), as this allows the lungs to move smoothly within the chest cavity while breathing. However, if excess fluid builds up in the pleural space, a person may be diagnosed with pleural effusion.

Pleural effusion results from one of two mechanisms. The first is transudative and produced by fluid pushed through small vessels, mainly due to abnormal circulation within these vessels. The second is exudative and produced by the alteration of the neighboring tissue, or the membrane itself, and caused by inflammation or infiltration by tumor cells.


1. Transudative Pleural Effusion

This type of pleural effusion occurs when liquid leaks across a normal pleura. The condition creates only slightly more fluid than normal, so it rarely needs to be drained. Congestive heart failure is the most common cause of transudative pleural effusion. However, liver or kidney disease can also cause fluids to build up in the body and leak into the pleural space.



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