What is the most common cause of a transudative pleural effusion?

The most common cause of a transudative pleural effusion is heart failure. This condition occurs when there is an imbalance between the production and absorption of pleural fluid, often due to increased hydrostatic pressure in the pulmonary circulation resulting from heart failure. When the heart is unable to pump effectively, fluid backs up into the pulmonary circulation, leading to increased pressure that pushes fluid into the pleural space.

Transudative effusions are characterized by a low protein content and low specific gravity, typically resulting from systemic conditions like heart failure rather than local inflammatory processes. Commonly seen in patients with congestive heart failure, this type of effusion is generally managed by addressing the underlying cardiac issue, which can significantly improve symptoms and reduce the fluid accumulation.

Other causes, such as malignancy, pneumonia, and infection, typically lead to exudative pleural effusions, which have higher protein content and are often associated with localized inflammatory processes. Understanding the nature of pleural effusions helps in diagnosing the underlying conditions effectively.