Transudate and exudate are both fluids extruded from various parts of the body, but transudate is usually clear and relatively free of cells and proteins while exudate has a high content of cells, cellular debris and proteins. The terms "transudate" and "exudate" refer to the fluid itself and not to a specific ailment or injury. However, the terms are often associated with transudate pleural effusion and exudate pleural effusion.
Pleural effusion is an ailment caused by fluid collecting in the pleural space of the lungs and results in shortness of breath, chest pain and coughing. This ailment is often referred to as "water on the lungs."
Transudate pleural effusion is a result of an imbalance in the production and removal of pleural fluid in the lungs. Diseases of the liver, kidneys or heart can all result in an imbalance filling pleural spaces with transudate. For instance, heart failure increases pressure in the small blood vessels responsible for removing pleural fluid, causing transudate to leak into the pleural space.
Exudate pleural effusion is a result of disease or damage to the pleura itself. In these cases, fluid is secreted and extruded from the pleura itself, and the pleural space fills with a cloudy fluid containing proteins, cells and cell debris.