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Management of postoperative chylothorax

Maxim Itkin and John C. Kucharczuk

INTRODUCTION

Traumatic chylothorax is a result of the direct or indirect trauma to the thoracic duct (TD) or its branches and the type most frequently encountered by surgeons. These injuries complicate thoracic, cardiac, and head/neck surgical procedures involving the anatomical areas where the TD or its branches reside. The incidence of chylothorax complicating pulmonary resections can be as high as 4%, and a recent report suggests the incidence may be rising given the increased frequency of extensive resections and lymph node dissection. ¹ Postesophagectomy TD leaks result in a statistically significant increase in 30-day major morbidity (85% vs. 46%; p < .001) and mortality (17.7% vs. 3.9%, p < .001) compared with no TD leak. ² The development of a postoperative TD leak has a significant impact on the patient’s course.s

Anatomically, the TD is a 2-5 mm vessel that originates at the cisterna chyli in the retrocrural area of the abdomen and then travels in the posterior mediastinum, finally draining into the left subclavian vein. It serves as a main drainage conduit of the lymphatic system. Unfortunately, the TD anatomy is highly variable; less than 40% of patients have “classic” anatomy, described as a solitary duct entering the chest on the right side between the esophagus and azygous vein (see Figure 25.1). The variable anatomy, in addition to the difficulty in visualizing the TD, increases the risk of intraoperative injury. ³

The TD collects lymphatic fluid from most of the parts of the body. “Chyle,” the lymph that originates in the intestine, contains a high concentration of chylomicrons absorbed from the gastrointestinal (GI) tract (see Figure 25.2) and constitutes approximately 40%-60% of the flow in the TD. The liver lymph, which is rich with proteins, contributes an additional 40% of the lymphatic fluid in the TD. Prolonged drainage of TD contents leads to depletion of circulating T-lymphocytes and significant nutritional depletion due to protein loss. It is the loss of the protein component from the TD fluid that decreases the intravascular oncotic pressure, resulting in fluid leakage and anasarca.

The traditional management of traumatic TD leaks includes pleural drainage, low fat diets to decrease the gut lymphatic flow, nutritional support, and time, hoping for spontaneous closure of the leak. ⁴ , ⁵ Electing to manage a TD leak conservatively depends greatly on the volume of the output. High volume leaks will rarely close with conservative management, since the volume is correlated with the size of the rent in the vessel. A low volume leak resulting from the avulsion of a small branch of the duct will often close with the management described. Assuming watchful waiting with pleural drainage, minimal fat intake, and nutritional support are attempted, the waiting time to declare conservative management a failure traditionally has been 2-3 weeks, which has often resulted in an immuneand nutritionally depleted patient. The advent of thoracic duct embolization (TDE) and improved lymphangiogram techniques have allowed us to reengineer our management pathway for traumatic TD leaks. At present, in our institution, patients with postoperative TD leak are started immediately on intravenous nutritional support. They are kept without oral intake for 72 hours and given an enteral fat challenge. If the TD leak has not resolved spontaneously, they are taken for lymphangiogram and TDE. If TDE fails, the lymphangiogram is used to accurately define the patient’s precise TD anatomy and, ideally, the site of leakage to aid in the plan for operative TD ligation. This early intervention approach allows us to minimize the nutritional and immunologic imbalances that accompany an ongoing TD leak, especially ones where the volume output is large.

DIAGNOSIS OF CHYLOTHORAX

In cases of the postsurgical chylothorax, the leakage of “milky” fluid from the chest tubes following the administration of enteral fat may or may not be diagnostic, and confirmation of the presence of chyle should be determined. An elevated triglyceride level relative to the serum triglyceride level, in addition to a high percentage of lymphocytes in the fluid, is used to biochemically confirm the diagnosis. Triglyceride levels are in 200-300 mg/mL and higher in patients on a regular diet but are significantly lower in patients on a fat-free diet, in which case TD is confirmed by a high lymphocyte count. In cases of uncertainty, we repeat an enteral fat challenge test by giving the patient cream.

TD VISUALIZATION AND TD EMBOLIZATION

The concept of TDE was initially described and tested by Dr. C. Cope at the University of Pennsylvania. ⁶ , ⁷ Cope found that visualization of the lymphatic system and TD following a lymphangiogram could increase the treatment success and use of a minimally invasive, percutaneous, transabdominal approach for TDE. The need for a traditional pedal lymphangiogram represented the main hindrance to the widespread use of TDE, as few interventional radiologists are experienced with this technique, since it is rarely used. Recently, a new technique of ultrasound-guided intranodal lymphangiogram has allowed most operators to easily acquire the experience to successfully perform a meaningful lymphangiogram. ⁸

Access to the inguinal lymph node is obtained using a 25-gauge spinal needle under ultrasound guidance. The needle tip is positioned in the hilum of the node. Using fluoroscopy, confirmation of the position of the needle tip is determined by injecting an oil-based contrast agent (Ethiodol; Savage Laboratories, Melville, New York, United States) by hand or using a balloon inflator filled with contrast. If the needle is in the optimal position, immediate opacification of the lymphatic vessels is observed. A volume of approximately 6 mL of oil-based iodinated contrast injected in each groin is usually enough to opacify the abdominal and pelvic lymphatics (see Figure 25.3). A “saline push,” an injection of saline following the infusion of contrast, is used to further advance the contrast toward the central lymphatic system.

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