Chylothorax

Question 1

Anatomy of thoracic duct

Answer 1

• originates from cisterna chyli (T10-L3)
• enters thorax through aortic hiatus (T12)
• Course
  
  • anterior to vertebral bodies (between Ao and azygous vein)
  • posterior to esophagus
• Crosses midline to left: T4-5 (coursing to left of esophagus)
• Arches laterally at C7 (anteiror to SC artery, superficial to phrenic/anterior scalene)
• Passes behind carotid sheath and terminates into jugular-SC vein junction
  
  • Single branch (80%)
  • Multiple branches (20%)

Question 2

Lymphatic drainage of right head, neck, chest wall, right lung, right heart, dome of liver, right diaphragm

Answer 2

Right lymphatic duct that drains into posterior junction of RIGHT jugular-SC junction

Question 3

Primary physiologic role of the thoracic duct

Answer 3

Deliver digestive fat (60% of ingested fat) to the venous system

Question 4

Main cellular component of thoracic duct lymph

Answer 4

T-lymphocytes

Question 5

Properties of chyle

Answer 5

• Bacteriostatic
• alkaline pH

Question 6

Normal rate of lymph flow

Answer 6

30-190 ml/hr

Question 7

Mechanics of normal lymph flow

Answer 7

• Negative transdiaphragmatic pressure gradient
• Thoracic duct valves
• Normal intraductal pressure: 10-25 cmH2O

Question 8

MCC of pleural effusion in neonatal period

Answer 8

Congenital Chylothorax

• Respiratory distress at birh or 1st weeks of life
• MOA:
  
  • atretic thoracic duct
  • multiple dilated lymphatic channels of fistulas
• Tx: conservative (self limited)
  
  • Breastfeeding ok
  • Thoracocentesis for inital relief
• Pleuroperitoneal shunting for persistent chylothorax (in absence of ascites)

Question 9

MC non-penetrating traumatic MOA of thoracic duct injury

Answer 9

Hyperextension of the spine with rupture of thoracic duct just above the diaphragm

Question 10

MC operations associated with surgical injuries to the thoracic duct

Answer 10

• Esophagectomy
• Aortic operations
• PDA ligation
• Left pneumonectomy
• Resection of posterior mediastinal tumors
• Sympathectomy

Question 11

Laterality of duct injuries above (and below) T6

Answer 11

• Right side: below T6
• Left side above T6

Question 12

Incidence of chylothorax after esophagectomy

Answer 12

0.5-3.5%

*no assocation with approach

Question 13

MOA of neoplastic chylothorax

MC neoplasm associated with chylothorax

Answer 13

Invasion, compression or tumor embolism of thoracic duct

Lymphoma (50% of cases)

Question 14

Most postoperative chylothoracies drain how much

Answer 14

Excess of 1L/day

*If persists for > 1 week, mortality and morbidity increased

Question 15

Spontaneous healing of non-surgical thoracic duct fistula occurs __ %

Answer 15

< 50%

Question 16

Laboratory (diagnostic) characteristics of chylothorax

Answer 16

Pleural fluid with:

• Triglyceride level > 110 mg/dL (99% diagnostic)
  
  • <50 ml/dL excludes chylothorax with 95% probability
  • 50-110 ml/dL: check chylomicrons
• Chylomicrons: very specific finding for chylothorax
• Fat staining with Sudan-3
• Cholesterol : Triglyceride ratio < 1

Question 17

Pseudochylothorax

Answer 17

Accumulation of cholesterol in long-standing pleural effusion.

Cholesterol > 200 mg/dL with cholesterol crystals (no chylomicrons)

Question 18

Medical managment of chylothorax

Answer 18

• Drainage of pleural space
• Reduction of chyle flow (somatostatin)
• Hydration
• Nutrition (medium-chain triglycerides)
  
  • Reduction in dietary intake and long-chain f.a.
  • TPN may be preferred
• ~ 25-50% spontaneous closure rate
• Infection rare as chyle is bacteriostatic

Question 19

Surgical treatment options for chylothorax

Answer 19

• Pleurodesis (chemical)
  
  • fistula healing likely due to obliteration of pleural space rather than vessel closure
• Pleuroperitoneal shunting (no ascites)
  
  • malignant chylothorax
  • thoracotomy contraindicated
• Percutaneous transabdominal duct catheterization and embolization
  
  • frail pateints not able to tolerate duct ligation
• Thoracic duct ligation

Question 20

Indications for thoracic duct ligation

Answer 20

• Thoracic duct drainage > 1500 ml/day (adults) or > 100 ml/day (children) over 5 day period despite medical managment
• Persistent leak > 2 weeks
• Nutritional or metabolic complicaitons
• Entrapped lung with inability to drain collection with thoracostomy
• Post-esophagectomy chylothorax
  
  • high morbidity and mortality due to immunologic and metaboic imbalances

Question 21

Surgical techniques to address thoracic duct

Answer 21

• Direct ligation of thorcic duct
• Mass ligation
  
  • all tissue between Ao, spine, esophagus and azygous vein
  • performed above diaphragmatic hiatus (right pleural space)
• VATS ligation
• Pleurectomy
• Fibrin glue
• Pleuroperitonal shunt

Question 22

Visualization of thoracic duct can be enhanced by what measures

Answer 22

Ingestion of 6-8 oz of cream or olive oil 2-3 hours prior to surgery

Question 23

Effect of thoracic duct ligation on mortality

Answer 23

Reduction in mortality from >50% to ~ 10%

Prophylactic thoracic duct ligation advocated during esophagectomy

Question 24

Describe how to ligate the thoracic duct?

Answer 24

Right thoracotomy.

Elevation of the soft tissue intervening between the esophagus on the right, the azygos vein on the left and the descending thoracic aorta and vertebral column deep to the operative field is performed with a Debakey forceps. It is this intervening tissue which contains the thoracic duct, including a plexus of lacteals. This soft tissue is then ligated in 3 positions at 2 cm increments starting approximately 2 cm above the esophageal hiatus of the diaphragm.