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.’