Reestablishment of Lymphatic Drainage after Vascularized Lymph Node Transfer in a Rat Model

Background: Vascularized lymph node transfer has recently received attention as a potential surgical treatment for lymphedema. Despite good results in some series, the mechanism and benefits of vascularized lymph node transfer have yet to be fully understood. This study aimed to investigate the reestablishment of drainage into transferred lymph nodes following vascularized lymph node transfer in a rat model. Methods: Seven rats underwent vascularized lymph node transfer. The operation performed on each rat consisted of two parts. First, the left groin lymph node basin with superficial epigastric vessels was harvested as a free flap. Second, the flap was reattached in the left groin of the rat by means of end-to-end microvascular anastomoses. Anastomosis patency was assessed immediately postoperatively and at the time of animal sacrifice. The rats were evaluated for reestablishment of lymphatic flow into the transplanted nodes at 1-month intervals for at least 6 months postoperatively. This was accomplished noninvasively by injecting the rats in their flanks with fluorescent indocyanine green, which was detected using a Photodynamic Eye infrared camera. Results: Anastomoses were patent in all seven rats immediately postoperatively. No indocyanine green uptake was seen in the transplanted lymph node basins in the first 2 months postoperatively in any of the rats. In five of seven rats, however, indocyanine green uptake was demonstrated in the transplanted lymph node basin by 6 months (average, 13 weeks). Conclusion: The authors report uptake of indocyanine green in five of seven rats at an average of 13 weeks after lymph node transplantation, consistent with the reestablishment of lymphatic drainage into the transplanted nodes.