Editing 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

[[Category:Thoracics]]