57yo woman presents to her primary provider’s office with a three week history of increasing dyspnea. She has a history of hypertension, cardiovascular disease, and COPD. Chest xray is below.
What are the two broad classifications of this findings and how do you differentiate between the two?
The two main classifications of pleural effusions are transudative and exudative.
To differentiate between the two, the pleural fluid is sent to the lab for composition testing and compared to the serum. According to Light’s Criteria, the effusion is transudative if:
- Pleural/Serum protein ratio < 0.5
- Pleural/Serum LDH ratio < 0.6
- Pleural LDH < 2/3 the upper limit of normal serum LDH