What Is Chyle?
It is a form of lymph that has been absorbed from the small intestine into the bloodstream through the lymphatic vessels (cisterna chyli and thoracic duct). The small intestine absorbs most of the digested food (except fat) and transports them to the liver for further use and storage. The fat, however, cannot be transported because it is insoluble in plasma (the liquid portion of the blood).The lymphatic system (a network of lymph vessels) normally transports lymph and absorbs the fat from the small intestine. Once the fat mixes with the lymph in the lymphatic vessels, it changes the colorless lymph into a milky liquid known as chyle. The lymphatic vessels from the small intestine drain the chyle into the cisterna chyli- a dilated sac that receives lymph from the entire lower body along with the chyle. The thoracic duct (the largest lymphatic vessel in the body) originates from this cisterna chyli and transports the collected chyle and the lymph into the internal jugular vein (major vein in the neck), which then empties it into the heart.
What Is Chylous Reflux?
It is a term used to describe the abnormal backflow of chyle from its normal route due to anomalies in the lymphatic vessels. This condition can be divided into two types based on the underlying cause-
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Primary Chylous Disorders (PCD) - Primary chylous disorders are caused by congenital lymphangiectasia (abnormally dilated lymphatic vessels), lymphatic obstruction, agenesis (complete absence) of lymphatic vessels, hypoplasia, and disruption of the thoracic duct, and cisterna chyli.
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Secondary Chylous Disorders (SCD) - These are usually the result of malignancy, trauma, or infection.
Both PCD and SCD lead to the accumulation of chyle and disruption of lymphatics, causing chylous lymphangiectasia in the genitalia, perineum, or legs. These dilated lymphatics often cause cutaneous vesicles which are visible on the skin, or they may rupture into the body cavities such as the pleura, peritoneum, kidney, bladder, uterus, etc. Rupturing leads to the accumulation of chyle in the relevant cavity (chylothorax, chylous ascites, chyluria, etc.), causing symptoms like dyspnea (difficulty in breathing), abdominal distension, chest pain, malnutrition, etc.
What Is Chylous Lymphagiectasia?
Chylous lymphangiectasia is the characteristic presence of abnormally large and plentiful lymphatics, also called mega lymphatics. The valves in these mega lymphatics are incompetent, and as a result, the chyle (now mixed with lymph) refluxes back into the lower part of the body, like the legs and the genitalia leading to swelling. The skin over the swollen parts will start developing blisters known as chylous vesicles, and if left untreated, they will rupture and discharge the chyle.
What Are the Complications Caused by Chylous Reflux?
The complications depend on the location of the chyle accumulation; they are-
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Chylous Vesicles - These are small blisters that appear on the skin (as cutaneous vesicles) of the legs and the genitals (scrotum in males and labia in females) as a result of chylous reflux. Eventually, the vesicles will rupture and leak chyle; discharge of chyle from the vesicles greatly interferes with the quality of life; they also serve as an entry point of bacteria causing cellulitis and lymphangitis.
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Chylous Metrorrhagia - The primary chylous lymphangiectasia in the vagina will present as edema in the genitalia; over time, this will cause persistent vaginal discharge from the vagina, a condition known as chylous metrorrhea.
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Chylothorax - This is the accumulation of chyle in the pleural space. Pleural space is the potential space between the visceral pleura and parietal pleura of the lung. Most commonly seen in patients with SCD due to traumatic disruption of the thoracic duct.
Non-traumatic chylothorax is seen in patients with congenital lymphangiectasis, lymphangiomatosis, Turner syndrome, lung cancer, filariasis, histoplasmosis, yellow nail syndrome, etc.
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Chylous Ascites (CA) - It is defined as the milky-appearing, triglyceride-rich peritoneal fluid in the abdominal cavity. The chyle in CA is rich in nutrients and immunoglobulins that become unavailable for absorption leading to dehydration, electrolyte imbalance, malnutrition, and suppression of the immune system.
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Chyloptysis - It is the excitation of chyle in the sputum due to chylous reflux into the lungs. It is a rare condition caused due to obstruction of the thoracic duct leading to the patient's intrathoracic lymphatic reflux disorder. Because of this, the patients will not have the usual symptoms of systemic lymphatic disorder.
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Chylopericardium - It is the accumulation of chylous fluid in the pericardial space. The pericardial space is the space between the parietal and visceral of the serous pericardium (membrane enclosing the heart).
It is a rare entity and is caused due to congenital mediastinal lymphangiectasia, iatrogenic development following cardiac surgery, malignant tumors, blunt or penetrating trauma, infection, etc.
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Chyluria - The presence of chyle in the urine is known as chyluria. Often caused by the parasite called Wuchereria bancrofti, symptoms include milky-white urine, loin pain, hematuria (blood in the urine), hypoproteinemia, weight loss, and cachexia.
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Chylocele - It is the collection of chylous fluid in the tunica vaginalis of the scrotum. It is the result of inflammation and obstruction of lymphatic vessels caused by chronic filariasis.
How Is Chylous Reflux Diagnosed?
The diagnosis of chylous reflux is a two-stage process, the initial investigations are done to establish chylous reflux, and the secondary investigations are done to diagnose the underlying cause of the chylous reflux.
Primary diagnosis can be made with any of the following methods-
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Lymphangiography - It helps to identify the anatomy and site of the lymphatic leak.
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Contrast Lymphangiography - It demonstrates lymphadenopathy (swelling of lymph nodes), filling defects, and the presence of mega lymphatics.
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Magnetic Resonance Imaging (MRI) - Offers extensive information about the anatomy of the lymphatic vasculature and the effects of lymphatic dysfunction on local structures and tissue composition.
Apart from the above investigation, lymphoscintigraphy- a non-invasive technique, has historically been the go-to choice of imaging modality by clinicians to identify any chyle or lymph-related disorders. It allows for road mapping of lymphatic transport and drainage systems. It also provides an assessment of the degree of reflux and is useful for detecting any possible recurrence.
Further investigations depend on the complication caused by the chylous reflux, for example- fine needle aspiration (FNAC) is done to confirm chylothorax and chylous ascites, and high-resolution computed tomography (HRCT) helps to identify lymphangioleiomyomatosis (that causes chyloptysis).
How Is Chylous Reflux Treated?
The edema caused due to mega lymphatics rarely requires surgical intervention, but other complications like cutaneous vesicles, chylous ascites, and chylothorax demand treatment.
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In cases of lymphatic vessel rupture, ligation or under-running of the dilated lymphatic vessels stops and prevents chyle leakage. Many patients benefit from this approach; however, in a few, it may cause lymphatic obstruction, which will worsen the underlying edema.
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Laparotomy is preferred in patients with chylous ascites or chylothorax and no obvious leak in the lymphangiogram. During the procedure, the posterior abdominal wall over the main lymphatic pathways must be carefully inspected for the presence of lymphatic leakage, and the whole intestine should be examined.
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If the surface of the small bowel is abnormal and leaking lymph, the involved or the most abnormal segment should be resected; if this fails to shunt the ascites back into the venous system, using a LeVeen or Denver shunt should be done.
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Aspiration will help with chylothorax to some extent but often recurs, and it can be prevented by obtaining pleurodesis with talc, Tetracycline, Bleomycin, or pleural stripping.
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Cutaneous vesicles can be simply excised or touched with diathermy or cautery, but they tend to recur unless the underlying cause is addressed.
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Recurrent infections that cause chylous reflux should be treated with broad-spectrum antibiotics.
Conclusion:
Chylous reflux is a rare condition; it occurs when the lymphatic back pressure is high, causing micro-vessels to burst into adjacent cavities. Most of the complications get resolved with surgery; however, when done in combination with medical therapy, including diuretics and a low-fat diet, the chances of recurrence are minimized.
