The layer of tissues that form the area between the lungs and the chest cavity is known as the pleural space. Pleural fluid gets accumulated in this space, known as the pleural effusion. This process takes place due to two reasons: transudate and exudate. The former is an imbalance between blood vessels and blood protein, causing an imbalance in the fluid transportation and the latter results from pleurae inflammation. The Pleural Fluid Routine examination analyses the accumulation of this fluid in the pleural space due to any one of the two reasons. It helps in detecting various blood-related problems.