a) Define a chylothorax. (10% marks)
b) Outline how you would diagnose it and the principles of management. (90% marks)
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)
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:
b) Diagnosis and management of chylothorax:
Diagnostic methods (from Maladonado et al, 2009):
Management (Bender et al, 2015):
Conservative measures:
Low fat diet - or at least a diet rich in medium-chain triglycerides (hoping with reduced chyle flow the defect will close on its own)
Secretion inhibitors such as octreotide and somatostatin
Vasocosntrictrs, eg. etilefrine
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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