Pleural effusion is the accumulation of fluid between the lungs and chest wall.
Based on protein content, it is classified into transudative or exudative types.
Transudative pleural effusions typically result from systemic factors that disrupt the hydrostatic or oncotic pressures in blood vessels, causing fluid to accumulate in the pleural space.
The most common cause is heart failure, where ineffective blood pumping increases venous pressure and causes fluid to leak into the pleural space.
Additionally, conditions like liver cirrhosis and nephrotic syndrome can both lower oncotic pressure. In cirrhosis, reduced albumin leads to fluid shifts, while in nephrotic syndrome, proteinuria lowers oncotic pressure, causing fluid buildup.
Exudative pleural effusions involve fluid accumulation with a higher protein content in the pleural space, often due to inflammation of the pleural membranes and increased vascular permeability.
Common causes like tuberculosis or pneumonia can inflame the pleura and accumulate exudative fluid.
Other causes include chest trauma, pulmonary embolism, malignancy, and autoimmune diseases, such as rheumatoid arthritis.