Watershed of Collecting Lymphatic Vessels of The Hip; Between Back and Thigh

Background: Gluteal lymphedema is often developed by proximal edematous type of lower extremity lymphedema (LEL) and severe LEL. This study aimed to clarify the watershed of collecting lymph vessels in the gluteal region using indocyanine green (ICG) lymphography. Methods: Medical records of cancer survivors who underwent ICG lymphography for secondary lower lymphedema screening from November 2020 to September 2023 were reviewed. Non-lymphedematous limbs without a dermal backflow pattern on ICG lymphography (ICG stage 0) were included. 0.1 mL of ICG was injected intradermally at five points; the tip of the coccygeal bone, the gluteal fold, the crosspoint connecting those points and the mid-lateral thigh, and the midpoints of them in a prone position and named H 1 –H 5 from medial to lateral. Based on ICG lymphography findings, the posteromedial and posterolateral pathway directions of collecting lymph vessels, shown as linear patterns, from each point were investigated. Results: A total of 20 limbs of 15 cancer survivors were included. The posterolateral pattern lymphatic pathway from H 1 /H 2 /H 3 /H 4 was observed in 16/15/3/4 limbs. The posteromedial pattern lymphatic pathway from H 2 /H 3 /H 4 /H 5 was observed in 13/15/18/10 limbs. Anteromedial pattern lymphatic pathway from H 5 was observed in 6 limbs. Conclusions: Multiple ICG injections enhanced the watershed line of collecting lymphatic vessels in the gluteal region, which would be affected for gluteal lymphedema diagnosis and treatment.