What characterizes transudative pleural effusion?

Transudative pleural effusion is primarily characterized by the accumulation of fluid in the pleural space due to changes in hydrostatic and oncotic pressures rather than by inflammatory processes. This type of effusion is generally associated with systemic conditions that affect fluid balance, such as congestive heart failure, cirrhosis, or nephrotic syndrome.

The mechanism of transudative effusion involves an imbalance between the pressure exerted by fluid within the blood vessels and the osmotic pressure that draws fluid back into the vessels. When hydrostatic pressure increases or oncotic pressure decreases, fluid is pushed out of the capillaries into the pleural space, leading to a transudate.

The characterization of transudative fluid typically includes a low protein content, specifically a protein concentration of less than 30 g/L is a common threshold used to differentiate between transudates and exudates. The reference to specific causes, such as malignancy, aligns more with exudative pleural effusions, which arise from local factors leading to inflammation or injury. Fixed protein counts would not apply to transudates, as their protein content can vary based on underlying conditions affecting fluid status.

Thus, the distinguishing feature of transudative pleural eff