TDE 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. 131-2B). Once opacified, the thoracic duct is cannulated and embolized. The transit time for oil-based contrast material to travel from the dorsal foot (i.e., lymphangiogram site) to the upper abdomen is extremely variable and is the rate-limiting step for the procedure.
The patient is positioned supine on a fluoroscopy table, and both feet are sterilely prepped. Moderate procedural sedation is employed for patient comfort. Prophylactic intravenous antibiotics are administered.
Because the cisterna chyli is more commonly located in the right upper abdomen, right pedal lymphangiography generally provides for more efficient and definitive opacification of this structure, but either or both feet may be used. Standard pedal lymphangiography is performed by injecting 0.25 to 0.5 mL of methylene blue dye between the web spaces of the toes. The dye is taken up by the lymphatics, which can be visualized as blue streaks under the skin. After 1% lidocaine local anesthesia, a small incision is made on the dorsum of the foot, and a lymphatic vessel is isolated and cannulated with a 30-gauge needle lymphography catheter. The lymphatic is secured to the needle with silk ties, and a gentle test injection is performed with a 3-mL saline syringe to assess for leaks. The lymphography catheter is then connected to an injector, and iodized oil (Lipiodol, Laboratoire André Guerbet, Aulnay-sous-Bois, France) is infused at a rate of 8 to 12 mL per hour to a maximal administered volume of 20 mL. During infusion, serial spot radiographs are obtained of the lower extremity, pelvis, and abdomen to track the cephalad opacification of the lymphatic system (Fig. 131-3). Transit times from the foot to the cisterna chyli are typically 1 to 3 hours. A saline bolus can be administered behind the column of iodized oil, if necessary, to speed its transit through the lymphatics. Once the thoracic duct is visualized, the infusion can be stopped and attention turned to the cisterna chyli and/or dominant lumbar lymphatics for needle cannulation or disruption. The foot incision is closed with 3-0 Prolene vertical mattress sutures and covered with a sterile dressing.
An anteroposterior radiograph of the right thigh in a patient undergoing pedal lymphangiography shows multiple lymphatic channels. The transit time from the foot to the abdomen is variable and can be augmented with a saline bolus behind the iodized oil contrast column.
Thoracic Duct Cannulation
Once the cisterna chyli is visualized, the patient's abdomen is prepped from the inferior costal margin to just below the umbilicus. Planning a percutaneous approach requires careful examination of the preoperative MRI. The position of the aorta and right renal artery are referenced to bony landmarks on the scan. A slightly inferior right anterior oblique approach is used most often to avoid these two vascular structures. The approximate starting position is 3 to 5 cm to the right of midline just below the costal margin. After local anesthesia, a small dermatotomy is made, and a 21- or 22-gauge, 15- to 20-cm Chiba needle (Cook Medical, Inc., Bloomington, IN) is directed toward the cisterna chyli using a “gun-site” technique (Fig. 131-4). This technique helps to minimize drifting of the needle as it travels through visceral structures. Just before the needle reaches the cisterna chyli, 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. A 0.018-in, 150-cm stiff guidewire (V-18 Control wire, Boston Scientific, Natick, MA) is advanced into the duct (Fig. 131-5). The needle is exchanged for a microcatheter. Predilation with a 4-French inner dilator and stiffening cannula from a nonvascular access kit (MAK-NV Introducer System, Merit Medical Systems, Inc., South Jordan, UT) is employed if the microcatheter fails to track appropriately. Given the likelihood of transintestinal passage, it is recommended that the access system be kept as small as possible, ideally 3 to 4 French. Direct hand injection of iodinated contrast medium is then performed to locate the site of thoracic duct injury. The point of extravasation should be carefully documented with imaging; in the event TDE is unsuccessful, precise localization of the injury will help guide subsequent surgical en bloc ligation.
An anteroposterior radiograph of the upper abdomen shows the opacified cisterna chyli. A hemostat is placed just right of the midline (at the intended puncture site), and the image intensifier is angled so that it overlies the cisterna. This “gun-site” technique minimizes drifting of the needle as it travels through the abdomen.
A 0.018-in guidewire is advanced through the access needle into the cisterna chyli and the lower thoracic duct. The needle is removed and exchanged for a microcatheter.
Embolization Procedure (a.k.a. Type 1 TDE)
The microcatheter is positioned up to, or ideally across, the site of thoracic duct injury. Embolization is performed by depositing 4- to 6-mm diameter platinum-fibered microcoils (Cook Medical, Inc., Bloomington, IN) along the entire length of the thoracic duct to within a few centimeters of the entry site. As the final step, a 2:1 mixture of ethiodized oil and N-butyl cyanoacrylate with 0.5- to 1-g of tantalum powder (components included in Trufill n-BCA Liquid Embolic System, Codman & Shurtleff, Inc., Raynham, MA) is injected to seal off the lower thoracic duct and lymphatic entry site (Fig. 131-6).
An abdominal radiograph after TDE shows coils in the lower portion of the thoracic duct and radiopaque glue throughout the upper abdominal lymphatics.
Needle Disruption of Lymphatics (a.k.a. Type 2 TDE)
If cannulation of the thoracic duct is not possible, serial needle passes are made to intentionally disrupt the cisterna chyli and adjacent lymphatics. Completion is indicated by the extravasation of contrast in the retroperitoneal space. The needle disruption technique results in the diversion of chyle into the retroperitoneum and decompression of the thoracic duct, allowing the intrathoracic injury to heal.