Anatomical Location of Lymphatic Pathways in the Posterior Thigh

Background It is necessary for treating lower extremity lymphedema to understand the lymphatic pathways in the extremities. This study aimed to clarify the anatomical locations of lymph vessels in the posterior thigh using indocyanine green (ICG) lymphography. Methods Medical records of cancer survivors who underwent ICG lymphography for secondary lymphedema screening from February 2019 to November 2020 were reviewed. Nonlymphedematous limbs without dermal backflow pattern on ICG lymphography (ICG stage 0) were included. Indocyanine green (0.1 mL) was injected intradermally at 2 points in the midlateral thigh, at the levels of one third and two thirds from the popliteal fossa to the gluteal fold in a prone position. Locations of the posterior thigh collecting lymph vessels visualized by ICG lymphography were marked on the skin surface with a pen, and distances from the popliteal fossa to the collecting lymph vessels were measured at the posterior midline in percentage, with the popliteal fossa set as 0% and the gluteal fold as 100%. Based on ICG lymphography findings, the number of the collecting lymph vessels shown as linear pattern and anatomical locations at the posterior thigh midline were investigated. Results Twenty limbs of 20 cancer survivors were included. Linear pattern was identified in all lower extremities; average number was 2.3 +/- 0.7 (range, 1-3). Most collecting lymph vessels shown on ICG lymphography, 26.7% (12 of 45) lymph vessels, were located within 40% to 50% of the region, and 24.4% (11 of 45) lymph vessels within 30% to 40% of the region. Conclusions There are 1 or more collecting lymph vessels in the posterior thigh by midlateral thigh ICG injection, which can be addressed for posterior thigh lymphedema.