An exudate is any thick fluid that is actively secreted by cells as a result of disease. It is generally composed of proteins, inflammatory cells, cell breakdown products, and sometimes bacteria. An example is pus. This is in contradistinction to transudate, which is a thin fluid formed by passive leakage of fluid from cells. It has a composition similar to extracellular fluid or plasma. An example is the pleural fluid found between the visceral and parietal layers of pleura.