Exudative pleural effusions are typically due to disease involving which structure?

• A. The pleura
• B. The heart
• C. The kidneys
• D. The mediastinum

Answer: (A)

Exudative pleural effusions arise when disease affects the pleural membranes themselves. Inflammation or malignant involvement of the pleura makes the tiny vessels in that lining leak more fluid, and this fluid is rich in protein and cells—characteristic of an exudate. This reflects local pleural pathology, such as infection (pneumonia with pleuritis), tuberculosis, or cancer, rather than a systemic imbalance.

Transudates, by contrast, come from conditions that alter pressures or proteins in the blood—like heart failure or kidney disease—without injuring the pleural membranes, so the fluid is more dilute. The mediastinum isn’t the primary site driving exudative pleural fluid. So the structure involved is the pleura, the lining of the lungs and chest cavity.