Chylothorax

Accumulation of chyle in the pleural space

(chylous ascites, chylous pericardial effusion)

Aetiology

• Traumatic
  • Blunt
  • Penetrating
• Iatrogenic
  • Catheterisation, particularly subclavian vein
  • Post-surgical (damage to thoracic duct)
  • Excision of cervical/supraclavicular lymph nodes
  • Radical lymph node dissections of the neck or chest
  • Lung, oesophageal or mediastinal resection
  • Thoracic aneurysm repair
  • Sympathectomy
  • Congenital cardiovascular surgery
• Neoplasms
  • Lymphoma, lung, oesophageal or mediastinal neoplasms
  • Metastatic carcinoma
• Infectious
  • Tuberculous lymphadenosis
  • Mediastinitis
  • Ascending lymphangitis
• Other
  • Lymphangioleiomyomatosis
  • Venous thrombosis
  • Congenital

Pathophysiology

• Extravasation from the thoracic duct
• Chyle
  • A milky white fluid with a high concentration of triglycerides and chylomicrons and white blood cells
  • Majority from dietary fat absorption, most of which is in the form of long chain fatty triglycerides
  • Short and medium chain triglycerides are mostly absorbed through portal venous system and hence don't affect thoracic duct flow as much
  • Chylomicrons travel through the lymphatic system over the course of several hours after a meal, and are then deposited into the venous system
  • Nutritionally rich, depending on the nutritional and dietary status of the patient
  • Can be clear
• Causes loss of fat and protein which often causes nutritional problems
  • Malnutrition - loss of energy, fat, and fat-soluble vitamins, and immunoglobulin and immune cells
  • Immune compromise (increased risk of bacterial infection)
  • Impaired wound healing
• Volume of leak typically 0.5-3L per day
  • Increased by peristalsis and even water intake
  • However chyle output mainly comes from long chain triglycerides
• Chyle does not contain fibrinogen, so even small injuries to the duct will not heal

Presentation

• Dyspnoea/cough
• Milky white chest tube output - usually becomes evident after diet/feeds introduced
• Neutropaenia, lymphocytopaenia, antibody loss, infection/sepsis, albumin loss, malnutrition

Diagnosis

• Triglyceride level of drain output - a level >1.2mmol/L is diagnostic of a chyle leak
• Chylomicrons is gold standard but takes longer to come back

Management

• Approach
  • Treat underlying condition
  • Manage nutrition
  • Low-output chylothorax (<1L/day) - often medical chylothorax or minor trauma to thoracic duct/tributaries - step-up approach with initial medical management, unless you suspect that won't work
  • High-output chylothorax (>1L/day) - often surgical injuries to main thoracic duct or cirrhosis - early intervention, within a few days of diagnosis, is often favoured, as these injuries are less likely to heal spontaneously
• Nutritional management (from Austin chyle leak guidelines 2023)
  • All patients need dietician involvement and nutritional assessment - identify pre-existing malnutrition, and prescribe an appropriate nutritional regimen to minimise chyle flow and maintain residual nutritional requirements
  • Consider energy losses from chyle output (840kJ/L) and protein losses (20-30g/L)
  • There are no RCTs which demonstrate an acceptable dietary fat intake to promote healing of the injury. Austin guideline says to give <20g long chain triglycerides per day for 3 weeks (or 2 weeks after resolution of the leak). UTD says aim <10g fat/day.
  • Monitor for signs of essential fatty acid deficiency if on fat-free diet for >2 weeks (skin lesions, eczema, impaired wound healing, thrombocytopenia)
  • Well-nourished patients with chyle leak <1000mL/day
    • Trial fat-free oral diet
    • Fat-free nutritional supplements to meet energy and protein requirements
    • Use some MCT oil/supplements to help meet requirements, but can't rely on them too much, as they cause GIT upset
      • Oral: MCT oil (on PBS) - 4tbs/24 hours
      • Oral or enteric: MCT procal - 5 sachets per day or Betaquik - 5x50mL doses/day
    • If patients don't respond to a modified oral diet, TPN may be warranted, but in that case keep going with some enteral feeds
  • Malnourished patients with chyle leak <1000mL/day
    • Enteral feeding with fat-free formula up to two weeks
    • After two weeks, need to change to low-fat elemental formula which contains a small amount of LCT to meet essential fatty acid and fat-soluble vitamin requirements (e.g. Vivonex)
    • If patients not responding, TPN may be warranted
  • Chyle leak >1000mL/day
    • NBM with TPN to meet full nutritional requirements - enteral nutrition is unlikely to make much difference
    • Can give TPN with impunity, as the phospholipid constituents pass directly into the venous circulation
• Other components of conservative management
  • Drainage of pleural space
    • Unnecessary with asymptomatic non-surgical patients with small effusions, unless symptomatic; patients with chylous ascites; and early post-op pneumonectomy patients without mediastinal shift
    • Intermittent thoracentesis is appropriate for patients with medical chylothorax and slow reaccumulation
  • Octreotide/somatostatin
    • Inhibits gastric, pancreatic and biliary secretions, and inhibit absorption of chyle from the intestine
    • Increases the probability of avoiding surgical repair in patients with low-volume leaks on TPN, as shown in systematic reviews
    • Some suggest giving from the start with low-volume leaks, while others advise giving as a second-line therapy
    • Limit to a trial of a few weeks
    • Can be given subcutaneously (50-200mcg TDS for 2-14 days) or intravenous infusion (6mg/day for two weeks)
  • Ensure lung is fully expanded
  • When drainage is <250mL/day, challenge with a fatty meal
• Surgery
  • Indications (all relative)
    • Failed conservative management
    • High-output chylothorax (>1L/day)
    • Some say, aim to operate between day 7 and 14
    • Suspected or known injury to main thoracic duct, as opposed to tributaries (less likely to settle with conservative management)
    • Older, frail or malnourished patients who may tolerate a trial of conservative management worse
  • Technique
    • Right thoracotomy or thoracoscopy and ligation of thoracic duct at level of diaphragm
      • Place olive oil or ice cream via NGT intra-operatively to increase chyle leak and aid identification of leak point
      • Can try suture ligation, clipping, gluing, flap coverage, or pleurodesis
    • Emerging percutaneous techniques involving radiological needle cannulation and duct occlusion

Prognosis

• 50-80% of post-op chylothorax resolves with conservative measures, with a high success rate in patients with <500mL/day