What is the primary composition of the fluid in chylothorax?

Composition of Chylothorax Fluid

The fluid of chylothorax is composed of fat and lymphocytes (option c). 1

Detailed Composition of Chylothorax Fluid

• Chyle is primarily formed in the intestines and is composed of proteins, lipids, electrolytes, and lymphocytes 1
• The hallmark of chylous effusion is the presence of chylomicrons in the fluid 1
• Chyle is odorless, alkaline, sterile, and typically has a milky appearance, although this can vary based on the patient's nutritional status 1

Diagnostic Criteria for Chylothorax

• Objective diagnostic criteria include:
  • Pleural fluid triglyceride level >110 mg/dL 1
  • Ratio of pleural fluid to serum triglyceride level >1.0 1
  • Ratio of pleural fluid to serum cholesterol level <1.0 (to distinguish from cholesterol pleural effusions) 1
  • Presence of chylomicrons in the fluid 1, 2

Cellular Composition

• The fluid typically contains a high number of cells with lymphocyte predominance 3, 2
• In one reported case, the pleural fluid contained 6600 cells/mL with 96% lymphocytes 3
• While lymphocytes are the predominant cell type, it's important to note that postsurgical chylothoraces can sometimes be neutrophilic 2

Atypical Presentations

• Although typically an exudate with high triglyceride content, chylothorax can present with:
  • Triglyceride levels <110 mg/dL in fasting or malnourished patients 2
  • Transudative characteristics when associated with cirrhosis, nephrosis, or heart failure 2, 4
  • Non-milky appearance in some cases 2

Clinical Significance of Composition

• The lymphocyte-rich composition contributes to the risk of immunosuppression in chronic chyle leak 1
• The high protein content (up to 30g of protein per 1000mL of chyle) explains the risk of malnutrition with ongoing losses 5
• Understanding the composition is crucial for accurate diagnosis and distinguishing chylothorax from other pleural effusions 2