CXR illustrating right-sided chylothorax in an infant.
CT illustrating right side dominant bilateral chylothorax in an infant.
If no identifiable cause of chylothorax is found, investigations into the anatomy of the lymphatic system may be pursued. There are two methods used to visualize the lymphatic system; however, they are rarely performed in the diagnosis of chylothorax. Lymphoscintigraphy confirms the diagnosis of chylothorax by using radiolabeled albumin; however, poor resolution makes visualizing the site of perforation difficult . Although more challenging, lymphangiography is still the gold standard due to its accuracy in localizing the site of lymphatic disruption (Figs. 16.3 and 16.4) . Lymphangiography also has the added benefit of causing sclerosant and occlusive effects to the thoracic duct due to the oil-based contrast lipiodol [14, 15]. While doses >20 mL can cause pulmonary arterial embolization, smaller quantities have shown success rates of 50–75 % in resolving chylothorax . Recently, the use of unenhanced MRI with T2-weighted imaging (T2WI) has proven advantageous in the visualization of and preoperative planning for chylothorax .
Lymphangiography outlining the thoracic duct.
Lymphangiography via injection of inguinal lymph nodes demonstrating no obvious leak.
Initial management involves relieving symptoms via drainage and replacing necessary nutrients. Due to the content of chyle, careful monitoring is necessary to avoid hypovolemia, immunosuppression, and significant protein and electrolyte loss . Initial drainage may be performed via thoracentesis, and serial intermittent drainage may be considered. However, early chest tube placement should be considered to allow for complete evacuation of chyle and to facilitate the quantification of the amount and rate of drainage, which may help guide the treatment plan . It is generally accepted that a period of nonoperative management should be pursued in the stable patient with a relatively low-output chylothorax. Some centers would continue with conservative measures if outputs remained <10 mL/kg/day. Most series describing chylothorax in children suggest a window of 2–4 weeks before operative intervention, due to an 80 % success rate with nonoperative methods [5, 18, 19].
Steps may be taken to reduce chyle production in an effort to reduce pressure in the lymphatic system and allow for natural closure of the leak . Chyle volume can be reduced through the administration of a fat-free diet with or without the addition of medium-chained triglycerides (MCT) . Unlike long-chained triglycerides, MCT are absorbed directly into the portal system, bypassing the lymphatics . This therapy has been shown to resolve up to 50 % of congenital and traumatic chylothorax cases . For infants, initial studies evaluating fat-modified breast milk as an alternative to MCT therapy have demonstrated effectiveness in treating chylothorax. Unfortunately, fat-modified breast milk may slow the growth of the child . In cases of fetal chylous effusion, a low-fat, MCT diet given to the mother has proven effective . If chyle flow does not adequately decrease with MCT, the use of parenteral nutrition with complete bowel rest has proven to further inhibit chyle secretion [23, 24]. If the leak rate exceeds 100 mL/kg body weight per day however, aggressive surgical therapy should be discussed . There is some evidence for the use of somatostatin and its synthetic analogue octreotide in adults, although there is minimal evidence of efficacy in children [18, 26].
There are several treatment options available if a chylothorax ceases to resolve with nonoperative management . These involve the use of targeted therapeutic agents, minimally invasive procedures, and open surgery. Although several treatment plans have been proposed, currently there is no consensus outlining when intervention should be employed. Several studies maintain that the timing of treatment escalation should be case dependent, particularly regarding patients with iatrogenic etiologies and neoplasms . In congenital chylothorax, surgical management is sometimes initiated in as early as 7–10 days after presentation . Successful intervention may decrease the length of hospitalization and reduce the risks of malnutrition and immunosuppression. Surgical success is enhanced when the location of leak is identified preoperatively.
Percutaneous Thoracic Duct Embolization
Percutaneous thoracic duct embolization (TDE) is a rare yet established approach to the treatment of chyle leaks . This procedure uses lymphangiography to guide cisterna chyli or thoracic duct catheterization and embolization . TDE has reported a 70 % success rate, with morbidity less than 2 % and no associated mortality [29, 30]. Rare sequelae include embolization of pulmonary arteries and chylous ascites [31, 32]. Due to the small size of lymphatic vessels, TDE is used much more commonly in adults; however, infants and children have been successfully treated using this method . Embolic materials include dehydrated alcohol, fibrin glue, platinum coils, or a combination, which are delivered via microcatheter to seal the leak site .
Thoracoscopy can be used for both thoracic duct ligation and pleurodesis in chylothorax cases [34–39]. This approach offers several advantages over open thoracotomy including enhanced magnified visualization of anatomy. The origin of the thoracic duct at the diaphragm can be difficult to visualize via an open approach due to its location deep in the surgical field. Further, thoracoscopy increases the likelihood of identifying a discreet leak, thus potentially decreasing the need for extensive dissection. It has proven safer and more cost effective in treating chylothorax in comparison to open thoracotomy . With high efficacy and low morbidity, some have argued that thoracoscopy should be considered earlier on in the treatment of disease . This is highlighted in cases of iatrogenic chylothorax post-esophagectomy, where mortality rates reportedly decrease by up to 40 % when surgical intervention is implemented at diagnosis.
Medical optimization of volume and nutritional status is key to the success of operative management. Visualization of the thoracic duct during thoracoscopy or an open thoracotomy can be enhanced by the preoperative enteric ingestion of cream, milk, or olive oil. Some have described enhanced visualization of the leak through injection of 1 % Evans blue dye in the thigh .
Positioning and Induction of Anesthesia
The procedure is ideally performed under single-lung ventilation. Traditionally, the operation involves three ports with port placement and patient positioning varying depending on the location of the leak [36, 37]. Most commonly, the duct is approached at the level of the diaphragm on the right side. In these cases, the patient is placed in the left lateral decubitus position and rolled forward (modified prone position) in order to enhance exposure of the posterior mediastinum. The right arm is extended in front of or over the head, and an axillary roll is placed. Neither central venous access nor arterial access is generally required for the operation although central venous access is often in place prior to surgery for parenteral nutrition.
The camera port is placed at the sixth or seventh intercostal space in the posterior axillary line. An instrument port is then inserted under direct vision in the midaxillary line 2–3 interspaces below the camera port, and the final working port is positioned at or above the level of the camera at the mid- to anterior axillary line. Alternatively, the site of chest tube insertion may be used for one of the port sites. Further, if the location of a lymph leak is identified preoperatively or at the time of initial thoracoscopic exploration, port site placement may vary. The surgeon and assistant face the patient and work from anterior to posterior. Low-pressure CO2 insufflation is generally required to collapse the lung with single- or dual-lung ventilation.
The operation begins with a limited exploration of the hemithorax with adhesiolysis as needed and residual fluid evacuation. Then, a thorough evaluation of the vertebra down to the level of the diaphragm is performed. If a distinct source of leakage is identified, then this leak is directly addressed for attempted ligation. A number of means including clipping, suture ligation, or sealing using an energy device can accomplish this. Some surgeons will choose to place fibrin glue at the ligation site . If no distinct area of leakage is identified or the duct cannot be adequately sealed at the source of leakage, then the duct is approached at the level of the diaphragm. The duct should lie posterior and lateral to the esophagus and does require some dissection to visualize. Division of the inferior pulmonary ligament will assist in efforts to identify the duct. If the thoracic duct is not visualized after pleural dissection, mass ligation of the duct and its tributaries has proven useful in management . This involves multiple ligations within the posterior mediastinum once the aorta, azygos vein, and esophagus have been identified and kept out of harm’s way. Due to the vast network of tributaries, overall lymphatic flow will not be affected, but the chylothorax should resolve [2, 38]. Ligation at the level of the diaphragm offers the benefit of blocking unrecognized tributaries. Although uncommon in the pediatric population, ligation during esophageal and cardiac surgery surgeries can be used as a prophylactic measure .
Pleurodesis is often employed as an adjunct to thoracoscopic duct ligation and has been shown to be both safe and effective in children . During the thoracoscopic approach, mechanical pleurodesis is recommended with particular attention to the inferior thoracic space. This can be accomplished by a number of means including abrasion using a laparoscopic peanut or piece of a scratch pad introduced with a grasper. Partial pleurectomy may also be employed. We do not recommend chemical pleurodesis using talc. Pleurodesis is also a prominent choice when the leak site cannot be identified .