Harvey's Garden

Chylothorax

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  • Patho/Etiology: Accumulation of chyle (lymphatic fluid from the intestines) in the pleural space due to disruption or obstruction of the thoracic duct.

    • Traumatic: Most common overall cause. Often iatrogenic, secondary to thoracic surgery (e.g., esophagectomy, cardiac surgery) or chest trauma.
    • Non-traumatic: Malignancy is the most frequent non-traumatic cause, especially lymphoma. Other causes include infections (e.g., TB, filariasis), sarcoidosis, cirrhosis, and superior vena cava (SVC) thrombosis.

  • Clinical Presentation: Symptoms relate to the size and rate of fluid accumulation.

    • Progressive dyspnea is the most common symptom.
    • Cough, chest pressure.
    • Fever and sharp chest pain are typically absent.
    • Signs of pleural effusion on exam: decreased breath sounds, dullness to percussion.
    • Post-traumatic chylothorax may present up to 10 days after the initial injury.

  • Diagnosis:

    • Thoracentesis (Gold Std): Pleural fluid analysis is key.
      • Appearance: Milky, opalescent fluid is classic but only seen in about half of cases; can be serous or serosanguineous, especially in fasting patients.
      • Biochemistry: Definitive diagnosis relies on lipid analysis.
        • Triglycerides > 110 mg/dL (diagnostic).
        • Triglycerides 50-110 mg/dL is borderline; requires lipoprotein analysis to confirm chylomicrons.
        • Triglycerides < 50 mg/dL makes chylothorax unlikely.
        • Pleural fluid cholesterol to triglyceride ratio < 1.
    • Imaging: CXR shows pleural effusion. CT chest can help identify the underlying cause (e.g., mediastinal mass, trauma). Lymphangiography (conventional or MR) can localize the leak if needed for intervention.

  • DDx (of pleural effusion):

    • Pseudochylothorax: Milky appearance but due to high cholesterol (>200 mg/dL) and cholesterol crystals, not triglycerides. Seen in chronic inflammatory effusions like TB or rheumatoid arthritis.
    • Empyema: Purulent fluid, high neutrophils, positive culture. Supernatant is clear after centrifugation, unlike chylothorax.
    • Hemothorax: Bloody fluid, Hct of fluid is >50% of serum Hct.
    • Transudative vs. Exudative effusions: Chylothorax is typically an exudate by Light’s criteria.

  • Management/Treatment:

    • Conservative (First-line): Goal is to decrease chyle flow.
      • Drainage of pleural fluid (thoracentesis or chest tube) for symptom relief.
      • Dietary modification: Total parenteral nutrition (TPN) or a low-fat diet with medium-chain triglyceride (MCT) supplementation (MCTs are absorbed directly into the portal system, bypassing lymphatics).
    • Medical: Octreotide/Somatostatin can reduce chyle flow.
    • Invasive/Surgical: Indicated for failure of conservative management, high-output fistulas (>1-1.5 L/day), or rapid nutritional decline.
      • Thoracic duct ligation (standard surgical approach).
      • Thoracic duct embolization (interventional radiology).
      • Pleurodesis (chemical or surgical).

  • Key Associations/Complications:

    • Complications: Result from chronic loss of chyle.
      • Malnutrition and weight loss (loss of fats, proteins, fat-soluble vitamins).
      • Immunosuppression (loss of T-lymphocytes and immunoglobulins), leading to increased infection risk.
      • Dehydration and electrolyte abnormalities.
    • Associations: Lymphoma, Down syndrome, Noonan syndrome, Turner syndrome.

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