Question

Differentiating transudative from exudative pleural effusions.

Hint:

For pleural effusion differentiation, always use Light's criteria to accurately classify the fluid as either transudative or exudative.

Answer 1

Step 1: Understanding Pleural Effusions.
Pleural effusion refers to the accumulation of fluid in the pleural space, which can be classified as either transudative or exudative based on the fluid's characteristics.

Step 2: Differentiating Transudative and Exudative Effusions.
- Transudative effusion occurs due to systemic factors like heart failure or liver cirrhosis, which cause changes in hydrostatic or oncotic pressure. The fluid is typically clear, with a low protein content (pleural fluid protein to serum protein ratio <0.5).
- Exudative effusion is caused by localized conditions such as infections, malignancies, or inflammatory diseases, leading to increased capillary permeability. The fluid is usually cloudy, with a high protein content (pleural fluid protein to serum protein ratio >0.5).

Step 3: Diagnostic Tests.
To differentiate, the Light's criteria are commonly used, comparing the ratios of pleural fluid protein, lactate dehydrogenase (LDH), and serum protein levels. If the pleural fluid protein to serum protein ratio is greater than 0.5, or if the pleural fluid LDH to serum LDH ratio is greater than 0.6, the effusion is exudative.