Question 5

a)    Define a chylothorax.    (10% marks)

b)    Outline how you would diagnose it and the principles of management.    (90% marks)

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College answer

Definition – A chylothorax is an accumulation of chyle (lymphatic fluid of intestinal origin) in the pleural space. It is caused by a disruption or obstruction of the thoracic duct or its tributaries - resulting in leakage of chyle into the pleural space. (1 mark-any reasonable definition)

Diagnosis (4 marks-this degree of detail not required)

The diagnosis of chylothorax is considered when a pleural effusion occurs in an appropriate clinical context. (1 mark) The aetiology of a chylothorax includes malignancy, iatrogenic injury

– thoracic or neck surgery especially oesophagectomy, trauma – blunt/penetrating or forceful emesis, associated with infection – tuberculosis – or with disease states – sarcoidosis or amyloidosis.

The gold standard for the diagnosis of a chylothorax is detection of the chylomicron content of pleural fluid. (2 marks) Chylomicrons are large lipid globules that belong in chyle – to find them in pleural fluid is always abnormal. This can be done by electrophoresis or by the less reliable method of fat staining.

Other features of a pleural effusion that suggest the diagnosis of chylothorax are a milky colour, high protein and LDH content and high triglyceride content. These signs are not as reliable as the gold standard and may miss the diagnosis especially in fasting patients. (1 mark)

A ‘fat challenge’ - looking for the presence of milky pleural exudate after consuming fat, and CT with lymphangiography are fewer practical ways of diagnosing chylothorax in the ICU.

Management (5 marks-reasonable outline, this degree of detail not required)

  1. Conservative management – the aim of all conservative management is to decrease chyle formation and allow the lymphatic defect to close (1 mark)
  • A ‘low fat’ diet, or at least one with predominantly medium chain triglycerides (0.5 mark)
  • Rare - a somatostatin or octreotide infusion or thoracic duct embolization (0.5 mark)
  • Use of TPN
  1. Treatment of the underlying condition – for example, sarcoidosis or lymphoma (1 mark)
  2. Surgical management – should be considered for all large chylothoraces, especially those associated with malnutrition or immunosuppression (1 mark)
  • ligation of the thoracic duct (0.5 mark)
  • pleurodesis (0.5 mark)
  • pleurovenous/pleuroperitoneal shunting - less frequently


Of all historic CICM college answers, none have come closer to achieving a standard of transparency which would be expected from serious adult education.  The inclusion of a prescriptive marking rubric is to be applauded.

a) The definition of chylothorax:

  • Chylothorax is a pleural collection of fluid, where the fluid is positively identified as chyle by the presence of chylomicrons

b) Diagnosis and management of chylothorax:

Diagnostic methods (from Maladonado et al, 2009):

  • Gold standard: differential electrophoresis of pleural fluid to confirm chylomicrons
  • Sudan Red stain of chylomicrons in pleural fluid
  • Clinical identification of milky pleural fluid
  • Protein and LDH  in the pleural fluid is usually high
  • Pleural fluid triglyceride level is usually high
  • Fasting test and fat challenge (chylomicrons are only found in the circulation within 3 hours of eating and they disappear in the fasted state)
  • CT and lymphangiography 

Management (Bender et al, 2015):

  • Conservative measures:

  • Surgical options:

    • Thoracic duct ligation (just proximal to the aortic hiatus)

    • Talc pleurodesis

    • Percutaneous lymphography and embolisation

    • Pleuroperitoneal shunt - where, for whatever reason, thoracic duct ligation is impossible


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