Practice Essentials
A chylous fistula is a leakage of lymphatic fluid from the lymphatic vessels. The fluid typically accumulates in the thoracic or abdominal cavities, but the fistula occasionally manifests externally. It is a rare but potentially devastating and morbid condition.
Chylous fistulas are an infrequent complication of head and neck surgery. However, damaging or cutting the thoracic duct while operating low on the left side of the neck does not occur infrequently, even in experienced hands. In fact, transecting the duct when carrying out radical surgery low down in the neck or the mediastinum may often be necessary. What should be avoided, however, is the failure to recognize this complication at the time of surgery, which could lead to serious consequences. [1]
Chylous fistulas are known to lead to prolonged hospitalization. Clinically, chylous fistulas may be difficult to manage because of significant electrolyte, fluid, and protein abnormalities that are associated.
The first description of a cervical chylous fistula was in 1875 by Cheever, followed by Stuart in 1907 with the first review on the condition. At the time, this condition was managed merely with pressure dressings and wound packing, and mortality rates of up to 12.5% for cervical chylous fistulas were reported. [2, 3, 4]
See the image below.
Signs of a chylous fistula
Patients with a chylous fistula present with drainage of a "milky white" fluid; however, in patients who are nil by mouth or on a fat-free diet, it may present as a leakage of clear fluid. Persistent chyle loss leads to the following:
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Electrolyte disturbance
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Hypovolemia
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Coagulopathy
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Immunosuppression
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Chylothorax
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Peripheral edema
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Wound infection
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Local skin breakdown
Prolonged chyle leak can therefore lead to mortality. [5]
Workup of a chylous fistula
Imaging studies in the workup of a chylous fistula include the following:
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Chest radiographs - In patients with a chylous fistula, chest radiography can demonstrate a soft-density opacity at the root of the neck
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Computed tomography (CT) scanning - CT scanning is used to confirm the presence, site, and extent of a neck collection; however, it is not useful for accurate localization of the thoracic duct injury
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Lymphangiography - Lymphangiography is an invasive procedure used to visualize the lymphatic vessels and thoracic duct, as well as to identify the site of chyle leakage
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Lymphoscintigraphy - This can also be used to identify the site of chyle leakage following thoracic duct injury
Management of a chylous fistula
Medical therapy
Prevention is widely believed to be the optimum management for a chylous fistula. Once a chylous fistula has occurred, medical management focuses on measures to reduce chyle flow, with closure of the fistula as a result. This should be done while paying close attention to the patient's nutritional status.
Two different conservative postoperative management techniques have been proposed: (1) drain removal and aspiration and (2) negative pressure wound therapy (NPWT). The use of adjunctive somatostatin therapy has also been suggested. Data does not delineate the exact parameters for the use of these techniques.
Surgical therapy
In the event of an intraoperative chyle leak during dissection of the left lower neck, the leak should be repaired with nonabsorbable 3-0 or 4-0 sutures and an overlying material. Fibrin sealant, collagen felt, polyglactin 910 mesh, and muscle flaps have been suggested.
Despite intraoperative measures, a chyle leak may persist postoperatively, mandating secondary repair, embolization, or ligation.
Epidemiology
Frequency
Chylous fistula is an infrequent complication of head and neck surgery, with an incidence reported in 1-3% of patients undergoing major neck surgery. [4] This condition has a predilection for the left side of the neck, but up to 25% of cases involve the right side of the neck.
Etiology
Radical neck dissection is the most frequent operation associated with chylous fistulas, but chylous fistulas may be found after selective neck dissection, penetrating neck trauma, cervical node biopsy, cervical rib resection, anterior neck surgery, and central venous cannulation. [6, 7]
Pathophysiology
The thoracic duct is the conduit for lymph and dietary fat to reach the venous bloodstream. The flow of chyle is around 2-4 L per day and consists of fat, protein, electrolytes, and lymphocytes. [4, 6, 8, 9] Its daily production is dependent on the diet and daily dietary intake.
Chemical composition of chyle is similar to that of tissue lymph, with higher concentration of cholesterol, phospholipids, and fat particles, particularly triglyceride rich chylomicrons and long-chain (>10 carbon atoms) esterified fats. [10]
The flow of chyle against gravity is supported by the interplay of thoracic and abdominal pressures, the transmission of peristaltic bowel contractions, the contraction of the lymphatic vessels walls, and the Venturi effect at the junction of the thoracic duct and the subclavian vein. [11]
Presentation
Patients with a chylous fistula present with drainage of a "milky white" fluid; however, in patients who are nil by mouth or on a fat-free diet, it may present as a leakage of clear fluid. The volume of drainage ranges from low output (< 500 mL/day) to more than 3 L per day in high-output fistulas. Persistent chyle loss leads to electrolyte disturbance, hypovolemia, hypoalbuminemia, coagulopathy, immunosuppression, chylothorax, peripheral edema, wound infection, and local skin breakdown. Prolonged chyle leak can therefore lead to mortality. [5]
Indications
Indications for surgical intervention in patients with cervical chylous fistula remain unclear. A chyle leak identified intraoperatively warrants immediate repair. Success of surgery declines in the postoperative period because of fibrosis and the effect chyle has on the soft tissue of the neck. However, failure of medical therapy and radiological intervention advocates neck exploration or ligation of the thoracic duct, particularly in patients with high-output fistulas.
Relevant Anatomy
The thoracic duct is the largest lymphatic vessel in the body, transporting lymph and chyle from lower limbs, the abdomen, the left hemi thorax, and the left side of the head and neck to venous circulation. It originates anterior to the body of second lumbar vertebra, the cisterna chyli, and ascends, along the right side of vertebral column, through the aortic hiatus of the diagram into the posterior mediastinum, traveling between the aorta and azygous vein towards the fifth thoracic vertebra, where it crosses to the left and continues to ascend up into the neck.
In the neck, the thoracic duct raises 3-5 cm above the clavicle before arching back toward the junction of the left subclavian vein with the left internal jugular vein. Intraoperatively, the thoracic duct can be identified as it courses anterior to the vertebral and thoracocervical vessels between the internal jugular vein and the anterior scalene muscle.
The anatomical variability of its course in the neck makes it susceptible to iatrogenic injury. Cadaveric studies have shown variation of both the site of termination and the number of terminal branches. (See the images below.) [10, 12, 13]
Thoracic duct inserting at the junction of internal jugular and subclavian vein in a cadaveric specimen.
Contraindications
No absolute contraindications to surgical repair of cervical chylous fistula exist.
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Intraoperative photo of the thoracic duct low in the neck on the left.
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Thoracic duct inserting at the junction of internal jugular and subclavian vein in a cadaveric specimen.
