A pleural fluid analysis shows: protein 4.5 g/dL, LDH 280 U/L (serum LDH 200 U/L), cholesterol 75 mg/dL, triglycerides 350 mg/dL, and the fluid appears milky. What is the most likely diagnosis and its typical etiology?
- A Pseudochylothorax (cholesterol effusion) due to chronic rheumatoid pleuritis
- B Empyema with fat droplets from long-standing infection
- C Chylothorax, most commonly due to thoracic duct disruption from malignancy or trauma ✓
- D Exudative effusion from pancreatitis with high amylase
Correct answer: C. Chylothorax, most commonly due to thoracic duct disruption from malignancy or trauma
Explanation
A milky pleural effusion with triglycerides >110 mg/dL (and/or chylomicrons on lipoprotein electrophoresis) is diagnostic of chylothorax, caused by disruption or obstruction of the thoracic duct. Common causes include malignancy (lymphoma most commonly), traumatic/surgical injury, or rarely congenital. Pseudochylothorax (cholesterol effusion) has high cholesterol >200 mg/dL with normal triglycerides and typically develops in chronic pleural disease (TB, RA). The triglyceride level >350 mg/dL here is diagnostic of true chylothorax.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.