Re-establishment of Lymphatic Drainage after Vascularized Lymph Node Transfer in a Rat Model

Background: Vascularized lymph node transfer (VLNT) has recently received attention as a potential surgical treatment for lymphedema. Despite good results in some series, the mechanism and benefits of VLNT have yet to be fully understood. This study aimed to investigate the re-establishment of drainage into transferred lymph nodes following VLNT in a rat model. Methods: Seven rats underwent VLNT. 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 re-attached in the left groin of the rat via end-to-end microvascular anastomoses. Anastomosis patency was assessed immediately post-op and at the time of animal sacrifice. The rats were evaluated for re-establishment of lymphatic flow into the transplanted nodes at 1 month intervals for at least 6 months post-op. This was accomplished non-invasively by injecting the rats in their flanks with fluorescent indocyanine green (ICG) which was detected using a PDE infrared camera. Results: Anastomoses were patent in all 7 rats immediately postop. No ICG uptake was seen in the transplanted lymph node basins in the first 2 months post-op in any of the rats. In 5 of 7 rats, however, ICG uptake was demonstrated in the transplanted lymph node basin by 6 months (average 13 weeks). Conclusions: We report uptake of ICG in 5 of 7 rats at an average of 13 weeks following lymph node transplantation, consistent with the re-establishment of lymphatic drainage into the transplanted nodes. Financial Disclosure Statement: None of the authors have any conflicts of interest nor disclosures. No funding was received for this article. Portions presented at: American Society for Reconstructive Microsurgery (ASRM) 2017 in Waikoloa, Hawaii Northeastern Society of Plastic Surgeons (NESPS) 2016 in Baltimore, MD Acknowledgments: We would like to thank Yanping Sun, PhD and Christopher Damoci from the Small Animal Imaging Shared Resource (SAISR) division of the Herbert Irving Comprehensive Cancer Center at Columbia University for their assistance in obtaining our MRI studies. Corresponding author: Jeffrey A. Ascherman, MD, Herbert Irving Pavilion, 161 Fort Washington Avenue Suite: 511, New York, NY 10032, jaa7@cumc.columbia.edu ©2018American Society of Plastic Surgeons

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