Chyle Fistula 

Chyle fistula is defined as a leakage of lymphatic fluid from the lymphatic vessels, typically accumulating in the thoracic or abdominal cavities but occasionally manifesting as an external fistula.^[1] Chyle fistula is a rare but potentially devastating and morbid condition. First described in the 17th century as complications of trauma, chyle fistulas most commonly occur secondary to lymphatic disease or malignancy or following abdominal, neck, or thoracic operations.^[2] Chyle fistulas also can form as a result of venous hypertension, and they have been described in patients with superior vena cava syndrome or thrombosis of the vena cava.^[1] Patients with chyle fistulas usually give histories of some comorbid conditions such as malignancy or prior operations of the chest, neck, or abdomen. In postoperative patients, symptoms become evident after the start of oral feeding and depend on the site of obstruction.^[3] Chyle fistulas can cause extreme morbidity because of loss of fluids, electrolytes, and other nutrients. In addition, chyle fistulas can result in loss of lymphocytes and immune dysfunction. Finally, chyle fistulas are space-filling and exert pressure on surrounding tissues, creating symptoms that can range from minimal discomfort to life-threatening situations.

The cisterna chyli and thoracic duct drain lymph from the entire body except the head, neck, arms, and right thorax (which instead use the right bronchomediastinal, jugular, and subclavian lymph trunks to form the right lymph duct). The anatomy is highly variable, with 50% of people not having an identifiable cisterna chyli. In addition, half of the 4 L of lymph draining through the cisterna chyli and thoracic duct originates from the intestinal and hepatic lymphatics.

The cisterna chyli is found on the posterolateral edge to the right of the aorta at the level of vertebral bodies T12, L1, L2, and L3 as lymphatics from the mesentery, intercostal, and lumbar regions coalesce in the retroperitoneal space.

At approximately L1, the cisterna chyle ascends, becoming the thoracic duct. The duct then enters the posterior mediastinum, crosses at T4 into the left retropleural space, and continues in a cephalad direction. The thoracic duct then enters the venous system at the junction of the left subclavian and internal jugular veins (see the image below).

Chyle fistulas are rare events. Typical causes include subclavian vein thrombosis, lymphatic disease, malignant invasion of the lymphatics, trauma, inflammatory reactions (ie, tuberculosis, pancreatitis, cirrhosis, adhesions, pulmonary fibrosis), and postoperative trauma following abdominal, neck, or thoracic operations.^{[2, 3]} Postoperatively, approximately 75% of chyloperitoneum cases occur after abdominal aortic aneurysm repair, 19% after aortofemoral bypass, and 7% after resection of infected aortic grafts.^{[2, 3]} Leakage of lymph from damaged lymph vessels is common after surgery or trauma.^[2] However, damaged lymphatics most often heal spontaneously or direct lymph centrally via rich interconnected lymphatic collaterals, without any significant morbidity. For chyle fistulas to form, either a scarcity of lymphatic collaterals must be present or the injury to the lymphatic channels must overwhelm the remaining lymphatic vessels. In addition, abnormal lymphatic vessels may be incapable of adequate lymph flow, leading to the accumulation of chyle.

Chyle flow varies dramatically depending on the quantity and quality of oral intake. During times of starvation, chyle flow is minimal. After meals, especially those with high contents of long-chain fatty acids, chyle flow increases dramatically. This basic knowledge provides the rationale for controlling dietary intake as part of the treatment of this disease.

Because of the relatively low incidence of chyle fistulas, a high index of suspicion is required to make a timely diagnosis. Diagnosis usually is made after the patient has recovered from the injury and has started eating.^[4]

Symptoms of chyloperitoneum (see the image below) include the following:

• Nausea
• Vomiting
• Early satiety or anorexia
• Abdominal discomfort or pain
• Dyspnea due to chylous fluid causing abdominal distention and pressure on the visceral structures and diaphragmChyle fistula. Management of chyloperitoneum.

Symptoms of chylothorax (see the image below) include the following:

• Shortness of breath
• Pleural effusion
• Decreased cardiac preload due to a mediastinal shift from a large chylothoraxChyle fistula. Management of chylothorax.

The characteristics of thoracentesis or paracentesis aspirate are as follows:

• Odorless
• Milky appearance that separates into a creamy layer when left to stand
• Specific gravity greater than 1.012
• Total fat composition of 0.4-4 g/L
• Total protein greater than 30 g/L
• pH greater than 7.0
• Sterile fluid
• Lipophilic globules when stained with Sudan III
• WBC differential of predominately lymphocytes

Treatment of chyle fistulas is determined by the following:

• Etiology of the fistulas: chyle fistulas secondary to malignancy are difficult to treat, while a definitive treatment is more successful after trauma or surgery^{[4, 5, 6, 7, 8]}
• Amount of output: fistulas with higher output that cause more physiologic derangements may require earlier aggressive therapies
• Site of the fistulas: fistulas arising in the neck are easier to access and identify than those occurring in the abdomen or thorax

Nutritional intervention

Nutritional intervention remains the mainstay of nonoperative treatment.^{[4, 5, 6, 7, 8]} Nutritional therapy includes the following:

• Use of enteral diets with fat restriction or the use of medium-chain triglycerides; medium-chain triglycerides are absorbed directly from the gut into the portal venous circulation^[9]
• Total parenteral nutrition (TPN) affords full caloric and nitrogenous support while allowing bowel rest; bowel rest achieves a decrease in chyle flow, allowing healing to occur

Other treatments

Several case reports and case series have reported the successful treatment of chylous leaks using octreotide in infants.^{[10, 11, 12, 13]} One series reported 100% closure of chylous leaks from malignancy using 50 mcg of subcutaneous octreotide 3 times per day.

Although development of a chylous fistula is unusual after axillary dissection, one study of radical breast cancer surgeries shows that they are manageable through conservative methods of treatment.^[14]

Transjugular intrahepatic portosystemic shunts (TIPS) have been reported to successfully treat chylous ascites due to cirrhosis.^[15]

A period of observation from one to several weeks should be allowed before determining whether these therapies are successful.

Repeated paracentesis/thoracentesis should be avoided because of the following reasons:

• Results from this treatment modality are poor
• The chance of infecting chylous fluid is increased
• Anasarca and cachexia may occur due to rapid loss of body protein, fat, and fluid
• Loss of lymphocytes may result in immune dysfunction

In patients in whom accumulation of chyle leads to significant problems, such as shortness of breath and lung collapse, the use of drainage through a thoracostomy tube or paracentesis may be necessary despite the obvious adverse effects that this form of therapy may produce.^[16]

The duration of medical therapies undertaken and the decision to proceed operatively are physician dependent. Because of the relative rarity of chyle fistulas, no definitive data are available to unequivocally direct the duration of therapy.

Surgery is undertaken when conservative therapies fail (approximately 40% of cases).^{[17, 18]} Surgical approaches vary significantly depending on the site and etiology of the leak. Surgical approach to the thorax using thoracoscopy may be tried, as long as adequate expertise is available.^[16]

If at all possible, ensure nutritional assessment and repletion before a surgical intervention because malnutrition increases morbidity significantly.^[4] Administer gram-positive antibiotic coverage with a beta-lactamase inhibitor in the 24 hours prior to insertion of the shunt.

Because of the possible complication of disseminated intravascular coagulopathy, which is especially prevalent in patients with malignancy, include coagulation parameters in the preoperative evaluation.

Contraindications to surgical correction of chyle fistulas are based on the patient's comorbidities and his or her ability to tolerate surgery.

Surgical ligation

Surgical ligation can be achieved successfully provided the site of the leak is identified and the primary pathology causing the leak has not caused disruption or blockage of other lymphatic vessels. Finding the leak may be aided by the use of scintigraphy. In some cases, the exact location of the disrupted lymphatic vessel is not identified and surgeons may use flaps (eg, muscle flaps) to cover the area where the leak is occurring. Laparoscopic ligation of chyle leaks has been described.

Other forms of therapy to plug the leak have included fibrin glue or the use of chemical irritants such as tetracycline.

Peritoneovenous shunts

The use of peritoneovenous shunts (Denver or LeVeen) is a modality of treatment available when other treatments fail. Peritoneovenous shunts are especially useful for the management of chyle fistulas resulting from causes other than prior operations. The main objective of peritoneovenous shunts is to drain the chyle accumulated in the abdomen back to the venous circulation.

Denver valves use a slit system that reduces flow by impedance. Insertion of these shunts can be achieved as a minimally invasive procedure, and they can be inserted under local anesthetic, sparing the severely ill patient the trauma of a major operation.

The LeVeen valve is a closed-pressure system that opens at pressures of 3 cm of water or less. This prevents leakage of blood into the tubing, thereby decreasing the chances of the system clotting (with subsequent failure).

Postoperative care

Antibiotic coverage is continued empirically for 4 days after surgery. Any coagulopathy should be treated aggressively without delay.^{[3, 19]} Patients should be monitored routinely until the resolution of the fistula. Postoperative visits should commence approximately 1 week after the patient is discharged from the hospital.^[3]

Treatment of chyle fistula is very successful. However, unless the underlying etiology is reversed, the problem can be chronic and unrelenting.

If left untreated, chyle fistulas can be fatal, with patients dying from severe fluid and electrolyte abnormalities, malnutrition, and overwhelming infections, including peritonitis and empyema. Iatrogenic complications also can occur,^[20] as well as complications from shunt placement, including disseminated intravascular coagulopathy, shunt failure, and fluid overload.

Occasionally, when chyle leak is not apparent during surgery, ligation of the bed of the thoracic duct does not stop the leak. In 3 patients with chylothorax, pleurodesis was achieved using continuous pleural irrigation with minocycline, versus intermittent pleurodesis.^[21]