The thoracic duct or its tributaries can sustain injury as a direct result of thoracic surgery or trauma. Chylothorax is an unusual but serious complication of thoracic surgery, particularly esophagectomy.¹ Management of patients with postoperative chylothorax can be difficult. Traditional conservative treatment includes chest tube drainage and low-fat total parenteral nutrition to decrease the physiologic production of chyle. Although this therapy is sometimes successful in patients with low-output leaks, it is less effective for large leaks (i.e., >500 mL/d). In high-output patients, repeat thoracotomy and direct thoracic duct ligation typically are performed to stop the leak (see Chap. 113). In this patient population, however, surgical thoracic duct ligation can be difficult owing to nutritional and immunologic depletion. As a result, some have called for earlier diagnosis and intervention to avoid metabolic deterioration and death.^2–5

Less invasive techniques have been suggested to lessen the morbidity associated with repeat thoracotomy. Some have advocated video-assisted thoracoscopic techniques to identify the thoracic duct for ligation.^6,7 More recently, percutaneous thoracic duct embolization has been introduced as a novel and noninvasive technique for controlling high-output chylothorax⁸ (Fig. 111-1). In this chapter we review the indications, preprocedural imaging, and technique of percutaneous thoracic duct embolization.

ANATOMIC PRINCIPLES

The method of thoracic duct embolization for the control of chylothorax requires a comprehensive understanding of the anatomic structures adjacent and anterior to the cisterna chyli. The approach requires puncture and cannulation of the lymphatic system with a 21-gauge needle. The course of the needle is through the anterior abdominal wall and peritoneum. Puncture of visceral structures and solid organs is unavoidable. The location of the cisterna is extremely variable and is the reason why we obtain preoperative MRIs. Careful attention must be paid to the renal arteries and aorta, which can be in very close proximity to the target. The preoperative MRI is the key to avoiding these structures.

IDEAL PATIENT CHARACTERISTICS

Patients who have a large-output chylothorax that has not responded to conservative care are appropriate candidates for thoracic duct embolization. It is easier to perform embolization on patients before attempts at operative repair, which distorts the lymphatic anatomy and makes cannulation more difficult.

PREOPERATIVE ASSESSMENT

A preoperative MRI is critical to the preoperative assessment of patients undergoing thoracic duct embolization. Because of the close proximity of the cisterna chyli to the right renal artery and aorta, preoperative imaging is critical to determining a safe approach. Thin-slice coronal T₂ images have proved the most useful series in making this determination (Fig. 111-2A). It is also important for the patient to have a normal coagulation profile because the needle will traverse many abdominal structures on its route to the aorta.

TECHNIQUE

Thoracic duct embolization is a 4- to 6-hour event and can be separated into two distinct procedures. A lymphangiogram is performed first to visualize the thoracic duct (see Fig. 111-2B). Once opacified, the lymphatic system is punctured, cannulated, and embolized. The transit time for oil-based contrast material to travel from the dorsal foot (i.e., lymphangiogram site) to the abdomen is extremely variable and is the rate-limiting step for the procedure.

Lymphangiogram

The patient is placed supine on a fluoroscopy table, and both feet are prepped. Anesthesia for thoracic duct embolization is typically light conscious sedation. The procedure is not a particularly painful one, but sedation is useful to make the patient more comfortable while lying supine for such a long period of time. It is important to make the patient as relaxed as possible during the procedure. Elevating the head with a pillow, low lighting, and a quiet environment help the patient to settle down while remaining still. Preoperative IV antibiotics are also given.

Standard pedal lymphangiography is performed by injecting 0.2–0.3 mL of methylene blue between the web spaces of the right toes. We prefer the right foot because the route from the right foot to the cisterna chyli is more direct. After waiting for 20 minutes, a small incision (1–2 cm) is made on the dorsum of the foot overlying a blue lymphatic channel. The lymph vessel is carefully dissected and cannulated using a 29-gauge lymphangiogram needle-catheter system. Once in the lymphatic tributary, the needle is secured with 4-0 suture and Steri-Strips. The end of the catheter is attached to a 3-mL syringe of saline, and a very gentle test injection is performed to look for leakage around the needle. Once the catheter-needle system is secured without leakage, it is attached to a specialized infusion pump. Iodinated oil (Ethiodol, Savage Laboratories, Inc., Melville, NY) then is injected at a rate of 8–10 mL/h. Spot-film radiographs are obtained to track the progress of the oil up the leg and through the lymphatic system (Fig. 111-3). Transit times from the foot to the cisterna chyli are typically 1–3 hours. To speed the process, patients may be given sips of a milkshake to stimulate chyle production.

Lymphatic Puncture

Once the abdominal lymphatic channels are visualized, the patient's abdomen is prepped from the inferior costal margin to just below the umbilicus. Planning a percutaneous approach to the abdominal lymphatic channels requires careful examination of the preoperative MRI. The position of the aorta and right renal artery are referenced to bony landmarks on the scan. An inferior right lateral approach is used most often to avoid these two vascular structures. The approximate starting position is 3–5 cm to the right of midline. After local anesthesia is given, a small dermatotomy is made using a no. 11 blade. We use an Acustick II Introducer Kit (Boston Scientific, Natick, MA) to puncture and then cannulate the lymphatic system. When making the puncture and approach to the cisterna chyli, it is often useful to angle the image intensifier "along the barrel" so that the needle on fluoroscopy overlies the cisterna (Fig. 111-4). This technique helps to minimize drifting of the needle as it travels through visceral structures. Just before the needle reaches the cisterna, the C-arm is placed into an anteroposterior position. The needle can be seen "tenting" the lymphatic channels. Entry is made with a brisk and deliberate motion. Contrast material is gently injected to confirm placement, and a 0.018-inch wire then is advanced through the channel and into the lymphatic system (Fig. 111-5). Sometimes the needle travels through both walls. With gentle retraction, the needle will "pop" into the lymphatic lumen, and the wire can be advanced.

Embolization

After the wire is safely within the lymphatic system, the needle is removed and exchanged for the inner 3F dilator and stiffener. The metal stiffener is needed to traverse the abdomen without buckling the system and losing access. Once the dilator and stiffener are close to the lymphatic puncture site, the stiffener is "pinned," and the dilator is advanced alone over the wire. The wire and stiffener then are removed, and contrast material is injected, opacifying the thoracic duct and in some cases the lymphatic leak.

Embolization then proceeds with the use of 0.018 embolization coils and cyanoacrylate glue (TrueFill Glue; Cordis Endovascular, Great Lakes, NJ). As the glue is injected, the catheter is removed to prevent it from becoming glued in place (Fig. 111-6).

An alternate technique also has proved effective, whereby the duct is not cannulated directly but is macerated with the 21-gauge needle instead.

POSTOPERATIVE CARE

No specific postoperative care is required for patients who have had thoracic duct embolization. Careful monitoring of the chest tube output is important in determining the success of the procedure. There is typically little response during the first 12–24 hours. After the first 24 hours, the output decreases by approximately 50% each day. The chest tubes are removed when output is less than 200 mL/d.

PROCEDURE-SPECIFIC COMPLICATIONS

Although solid organs and bowel are traversed with the 21-gauge needle on route to the lymphatic system, complications are rare. We have seen no major complications in over 50 patients. One of our patients had a foot infection on the dorsum of the foot at the lymphangiogram site.

SUMMARY

Lymphatic embolotherapy is well tolerated, has a low complication rate, and can provide a lifesaving alternative for patients with massive chylothorax.

CASE HISTORY

A 50-year-old man developed a large-output (2-L) chyle leak after esophagectomy. The patient did not respond to conservative treatment and was referred for thoracic duct embolization.

A preembolization MRI shows the cisterna chyli (Fig. 111-7). After a right pedal lymphangiogram, the cisterna was opacified with an oil-based contrast agent. The puncture site was located just to the right of midline, and the image intensifier was positioned so that the needle overlay the target lymphatic structure. The "along the barrel" technique is illustrated in Fig. 111-8. The lymphatic system was cannulated using a 0.018-inch wire (Fig. 111-9), and a contrast agent injection was performed and the leak identified (Fig. 111-10). The leak then was embolized and sealed using coils and glue (Fig. 111-11).

Postoperatively, the effusions decreased by 50% each day, and the chest tubes were removed 3 days later. The patient was discharged home soon thereafter.

EDITOR'S COMMENT

An important principle in management of lymph leaks is the notion of relative resistance. The lymph system is generally a "low pressure" system that responds to subtle pressure differences. If a lymph drain provides a low resistance option to lymph flow, the output is likely to continue. Alternatively, graded increases in resistance are likely to encourage lymph flow through alternative pathways. One of the functional consequences of thoracic duct "embolization" may be that it changes the dynamics of lymph flow.

–SJM

REFERENCES