Chylothorax

Reviewed and revised 8 September 2014

OVERVIEW

• Chylothorax occurs when chyle from the thoracic duct empties into the pleural space
• Chyle is a milky white fluid with a high concentration of triglycerides, chylomicrons, and white blood cells
• Pseudochylothorax is pleural fluid that mimics true chylous pleural effusion in appearance but lacks the biochemical criteria for chylothorax; usually due to a longstanding pleural effusion

ANATOMY

The primary function of the thoracic duct is to transport digestive fat (~70% of total) to the venous system but also serves as a major route of lymphatic drainage in the human body

• Thoracic duct transports the chyle from the cisterna chyli into the circulatory system, usually into the junction of the left jugular and subclavian veins
• one thoracic duct arises from the cisterna chyli and ascends through the aortic hiatus on the anterior surface of the vertebral bodies between the aorta and azygos vein (~50% of people, there is considerable anatomic variation)
• the thoracic duct has extensive lymphatic and venous communications
• Between the cisterna chyli and the central venous system, the thoracic duct runs in close proximity to various anatomical structures including the oesophagus, lungs, aorta, vertebrae and lymph nodes

CAUSES

• Iatrogenic — most common; e.g. post-esophagectomy, lymphatic fistula formation
• Trauma — 20%; e.g. penetrating trauma, fracture-dislocation of the spine
• Subclavian venous thrombosis
• Neoplasia (e.g. lymphoma)
• Idiopathic
• Infection — Filariasis, Tuberculosis
• Congenital and acquired lymphatic disorders ( e.g. Intestinal lymphangiectasia, Lymphangiomyomatosis)
• Mediastinal lymphadenopathy
• Chylous ascites (e.g. cirrhosis, pancreatitis, other causes of chylothorax affecting abdominal lymphatics)

CLINICAL FEATURES

• milky white opalescent pleural aspirate (can be clear, depending on nutritional state)
• 80% unilateral
• if traumatic/ iatrogenic there is often a latency period of 2–7 days between the time of injury and clinical evidence of chylothorax (unless there is a major injury)
• respiratory embarrassment (dyspnea, cough, chest discomfort)
• complications such as poor nutritional state, immunocompromise and hypovolaemia
• features of the underlying cause

Fever and pleuritic pain are rare as chyle is non-irritating to the pleura

INVESTIGATION

Pleural aspirate analysis

• appearance
• presence of chylomicrons is diagnostic
• pleural fluid triglyceride level >110 mg/dL (though 15% have less)
• protein-discordant (high protein and low LDH levels) exudate unless additional cause of transudate is present (e.g. CHF, cirrhosis)

Imaging

• CXR
• CT chest
• conventional lymphangiography or lymphoscintigraphy (role is poorly defined, often little impact on management)

Investigations to diagnose underlying cause

MANAGEMENT

Overview

• tailor management to cause, clinical context (size of the effusion, the rate of accumulation, clinical effects, comorbidities) and available expertise
• non-surgical management is effective in about 50% of traumatic chlylothoax cases, but only a minority of non-traumatic cases
• surgical treatment is generally indicated if non-operative treatment is unsuccessful at 2 weeks
• surgical intervention offers better results than conservative management when the daily chyle leak exceeds 1.5 l in an adult or >100 ml/kg body weight per day in a child
• malignant causes are generally managed conservatively

Maintaining Nutrition and Reducing the Volume of Chyle Circulation

• Dietary: medium-chain fatty acid diet (absorbed directly into portal vein) or total parenteral nutrition (resolves 50% of congenital and traumatic chylothoraces)
• Octreotide

Relieving Dyspnea by Removing Chyle from the Pleural Cavity

• Thoracentesis (short term only)
• Tube thoracostomy (short term only)
• Pleuroperitoneal or pleurovenous shunting
• Pleurodesis

Treatment of the Underlying Defect

• Thoracic duct embolization
• Ligation of the thoracic duct (thoracoscopy or thoracotomy)
• Clipping or fibrin glue to the thoracic duct leak
• Radiotherapy for mediastinal lymphoma
• Flap coverage

Other suggested therapies

• alpha agonists to cause lymphatic constriction, e.g. etilifrine, midodrine

Supportive care and monitoring

OTHER INFORMATION

• chylothorax is the most common type of pleural effusion in neonates, due to: persistent fetal chylothorax, rupture of the thoracic duct from trauma during delivery, or to developmental abnormalities of the thoracic duct.

References and Links

Journal articles

• Nair SK, Petko M, Hayward MP. Aetiology and management of chylothorax in adults. Eur J Cardiothorac Surg. 2007 Aug;32(2):362-9. PMID: 17580118. [Free Full Text]

FOAM and web resources

• Maryland CCP — Chyle- coming to a paracentesis near you! (2014)