What causes chylothorax?

Causes of Chylothorax

Chylothorax is primarily caused by disruption or dysfunction of the thoracic duct or its tributaries, resulting in leakage of chyle into the pleural space. 1

Major Etiological Categories

1. Traumatic Causes (54% of cases)

• Iatrogenic trauma - accounts for the majority of traumatic chylothorax cases:
  • Esophageal resections (complicates up to 4% of cases) 1
  • Lung cancer resections 1
  • Cardiovascular surgeries 1
  • Spinal surgeries 1
• Non-iatrogenic trauma:
  • Penetrating trauma 1
  • Fracture dislocation of the spine 1, 2
  • Hyperflexion injuries of the spine 1
  • Blunt thoracic trauma (rare) - can cause delayed chylothorax due to thoracic duct disruption 2

2. Non-traumatic Causes (46% of cases) 1

• Malignancy (18% of all chylothoraces): 1

  • Lymphoma (accounts for 75% of all malignant chylothoraces) 1, 3
  • Metastatic carcinoma 1

• Non-malignant etiologies (28% of all chylothoraces): 1

  • Lymphangioleiomyomatosis 1
  • Sarcoidosis 1
  • Cirrhosis 1
  • Heart failure 1
  • Nephrotic syndrome 1
  • Venous thrombosis 1
  • Filariasis 1
  • Venolymphatic malformations 1
  • Tuberculosis 1
  • Amyloidosis 1
  • Obstruction of central veins 1

• Idiopathic - approximately 9% of all chylous effusions have no identifiable cause 1

Pathophysiology

• Chyle is formed when long-chain triglycerides in the diet are transformed into chylomicrons and very-low-density lipoproteins, which are secreted into intestinal lacteals 4
• These lymphatic channels coalesce to form the thoracic duct, which transports chyle and drains into the left subclavian vein 4
• Any injury or obstruction to the thoracic duct or its major tributaries as it courses through the thoracic cavity can lead to chyle leakage into the pleural space 4

Diagnostic Confirmation

• Pleural fluid analysis is essential for diagnosis:
  • Triglyceride level >110 mg/dL is diagnostic 1, 2
  • Presence of chylomicrons confirms the diagnosis 1
  • Fluid appears milky white and opalescent 4

Clinical Implications

• Untreated chylothorax can lead to serious complications:
  • Dehydration 3
  • Malnutrition due to loss of proteins and lipids 3, 5
  • Immunosuppression 3
  • Electrolyte disturbances 3
  • Infection 3
  • Mortality rates up to 50% if left untreated 2

Diagnostic Approach

• Chest radiography can confirm the presence of pleural fluid but cannot characterize the type of effusion 1
• CT imaging can help narrow the differential diagnosis, especially in non-traumatic or unknown etiologies 1
• Conventional lymphangiography is the gold standard for visualizing lymph nodes, lymphatic vessels, cisterna chyli, and the thoracic duct 1
• A combination of CT and unilateral pedal lymphangiography can identify the cause and locate the leak in 75% of idiopathic chylothoraces 1

Understanding the specific cause of chylothorax is crucial for determining appropriate management strategies and preventing potentially life-threatening complications 5, 6.