The aim of the present study was to investigate the impact of non-ICG(+) LVs on the outcomes after LVA compared to ICG(+) LVs with propensity-score-match analysis.

It is a common belief among lymphatic supermicrosurgeons that LVA should only be performed with indocyanine green-enhanced (ICG(+)) LVs since such LVs are considered functional and are suitable for achieving better outcomes. However, in moderate to advance lymphedema patients, the use of non-ICG(+) LVs are inevitable despite efforts to identified ICG(+) LVs with ICG lymphography10, magnetic resonance (MR) lymphangiography11, or ultrasound12. In a previous study, it was suggested that a non-ICG(+) but flow-positive LV should also be considered functional because the functionality of an LV should be determined by its capability to transport lymph instead of ICG(+) lymph. Therefore, non- ICG(+) but flow-positive LVs should also be used for LVA to maximize the outcome13. This hypothesis was further supported by a recent article emphasizing the concept of a lymphatic-based lymphosome14, where it has been demonstrated that a functional LV will not become ICG(+) when ICG is not injected in the region being drained by this particular LV. It offers an explanation as to why a supposedly functional LV is not enhanced by ICG.

Inclusion Criteria:

• Patients diagnosed with lymphatic-related diseases at Kaohsiung Chang Gung Memorial Hospital from September 2015 to March 2023.
• Patients who underwent LVA for unilateral lower-limb lymphedema.

Exclusion Criteria:

• Primary lymphedema
• Bilateral lower limb lymphedema
• History of previous treatment for lymphedema (LVA, vascularized lymph node transfer (VLNT), liposuction, or excisional therapy such as the Charles procedure) - Those that were lost to follow-up.