Discussion:
Chylomicrons arise from the combination of long chain triglycerides with
cholesterol esters and phospholipids. These molecules are resistant to
be broken down by intestinal lipase so they pass to the lymphatic system
of the small intestines then via thoracic duct to systemic
circulation.1
The thoracic duct length varies from 38-45 cm and ends typically at the
junction between internal jugular and left subclavian veins carrying
lymph from lower limbs and chyle from intestines.10
Chylothorax results from the leak of chyle from thoracic duct to the
pleural cavity. This can happen after rupture, disruption or obstruction
of the thoracic duct.1
The aetiology of chylothorax can be categorized into traumatic,
non-traumatic (spontaneous) and idiopathic. Chylothorax usually present
with acute symptoms including dyspnoea, fatigue and less commonly chest
pain and fever. Chyle is a non-irritating fluid to the pleura and this
can explain the infrequency of chest pain upon presentation.
The diagnosis of chylothorax is mainly based on aspirated fluid
analysis, the milky appearance is not exclusive to chylothorax, other
conditions like empyema and cholesterol effusion can cause milky pleural
effusion and the differentiation between these conditions is vital for
management.8.10
Chylothorax is defined by the presence of triglycerides more than 110
mg/dl in the fluid and cholesterol less than serum. Usually the fluid is
alkalotic, lymphocytic and exudative,8,10 but it was
reported to be transudative rarely15
Previously, non-traumatic chylothorax especially from neoplasms was the
most common in adults but recent reports indicated that traumatic mainly
post-operative cases are more common, this can be due to increased
number of chest procedures and surgery or only increased
recognition.1,4
Traumatic chylothorax was described in various types of surgery
including chest, neck, cardiac, gastric and oesophageal. It is
considered to be iatrogenic with favourable outcomes in most cases.
Oesophageal surgery was considered the highest risk surgery to develop
chylothorax. In addition to surgery, blunt trauma and penetrating
injuries were also associated with chylothorax due to direct or indirect
thoracic duct damage.1,4
Most cases of non-traumatic or spontaneous chylothorax comes from
malignancy with lymphoma to be most common followed by bronchogenic
carcinoma and other tumours, kaposi sarcoma was also
reported.4
Other than neoplasms, many causes were identified to result in
chylothorax including tuberculosis, filariasis, sarcoidosis, congestive
heart failure, yellow nail syndrome, lymphangioleiomyomatosis, lymphatic
malformation and radiation therapy.3,4,12
Congenital chylothorax was described in new-borns to be the most common
cause. Trisomy 21 or Turner syndrome appear to be associated risk
factor.
Spontaneous chylothorax with no apparent cause was reported in few
cases, minimal physical activity or sudden head movement especially neck
hyperextension was thought to be the precipitating factor along with
recurrent vomiting, hiccups and cough.9,11 It was
suggested that there should be a weak point from pre-existing disease to
cause thoracic duct rupture with minimal exercise, one of the cases had
previous TB infection and like our case9, the presence
of positive QuantiFERON raise the possibility of latent TB which could
have played a role in causing disruption of the thoracic duct. There was
no evidence of active TB in our patient and the spontaneous resolution
of pleural fluid can support that.
Management of Chylothorax can be either conservative or surgical.
Conservative treatment includes the use of a low-fat diet supplemented
with medium chain triglycerides (MCT), other interventions are available
based on the case including chest tube drainage, pleurodesis, thoracic
duct ligation or embolization.5,7
But it’s worthwhile to know that most of the cases of spontaneous
chylothorax are self-limiting and can be managed conservatively with
rest, good hydration and low-fat diet.
Conclusions: spontaneous chylothorax can be the result of
variety of conditions. It should be always in mind that some cases are
transient and no underlying disorder can be identified. We recommend
higher threshold for invasive investigations when no alarm signs are
detected.
Patient Perspective: ‘it was the first time having these
symptoms. I was relieved that the illness is benign and will not need
more procedures.’