Patency Evaluation of Lymphovenous Anastomosis

Lymphovenous anastomosis (LVA) diverts congested lymph into venous circulation, which addresses pathophysiology of obstructive lymphedema. In LVA, a lymph vessel is anastomosed to a recipient vein. As in any other vascular and microvascular surgeries, anastomosis patency is critical for efficacy of LVA. However, compared to other vascular and microvascular surgeries, patency evaluation is challenging in LVA because of its small vessel size; the collecting lymph vessel is around 0.5 mm in diameter. There are two ways of patency evaluation: indirect and direct evaluations. In indirect evaluation, anastomosis patency is assessed by comparing findings before and after the surgery in lymphoscintigraphy and other lymph flow imaging modalities; if postoperative lymph circulation is improved, LVA is considered patent. In direct evaluation, anastomosis site is directly visualized in various lymphography images such as near-infrared fluorescence, magnetic resonance, ultrasonography, and photoacoustic images. Direct patency evaluation is crucial for real long-term patency evaluation after LVA. However, it is difficult to evaluate all anastomosis sites where dermal backflow covers or fat tissue is very thick. Further advancements are required for thorough evaluation of long-term LVA patency.