I maging of the lymphatic vessels is an essential tool for diagnostic assessment of lymphedema. Lymphoscintigraphy is the current reference standard for lymphatic imaging (1-3). SPECT (4), indocyanine green (ICG) fluorescent lymphography (5-7), and MR lymphography (8) are emerging techniques. Lymphatic imaging of the lower limb requires intradermal or subcutaneous injection of tracer or contrast material in the foot to demonstrate the lymphatic vessels. No standard protocol exists, and single or multiple injections are applied at different sites.Each lymphatic vessel has an independent origin in the foot. The lymphatic vessel often branches and converges throughout its course, but it is uncommon to have interconnections with adjacent lymphatic vessels to produce a network. These characteristics allow us to categorize the lymphatic pathways in the lower limb into groups. Conventionally, the lymphatic pathways are divided into two groups: an anteromedial group connecting to the superficial inguinal lymph nodes and a posterolateral group connecting to the popliteal lymph nodes (9,10).Few anatomic studies have addressed the lymphatic vessels because of technical difficulties with their identification. Kinmonth and Eustace (11) developed lymphangiography and found that leg lymphedema is caused by deterioration of lymphatic vessels, lymph nodes, or both and that the pathologic process arose first in the lymph node. However, current lymphatic imaging protocols may miss information because of the lack of anatomic knowledge regarding the relationship between lymphatic vessels and their regional lymph nodes (12). Investigators of a previous study of ICG fluorescent lymphography in cadavers ( 13) classified lymphatic pathways into four distinct groups in the lower limb: anteromedial, anterolateral, posteromedial, and posterolateral. Origins of the lymphatic vessels in the foot may be defined in relationship to these four lymphatic groups, which could be selectively visualized with ICG lymphography.A limitation of previous studies was that the relationship between a lymphatic group and its regional lymph nodes could not be determined with ICG lymphography

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Background The purpose of this study was to evaluate the lymph function of the lower extremities and to identify early symptoms of lymph dysfunction in secondary lymphedema by observing lymph flow with indocyanine green (ICG) fluorescence lymphography (LG). Methods We retrospectively evaluated the lymph flow of 108 limbs in 54 female patients with leg lymphedema secondary to pelvic lymphadenectomy for gynecological carcinoma and 14 limbs in 7 female controls without a history of pelvic lymphadenectomy or radiotherapy. ICG was injected into four points at the distal part of the lower extremity. Lymph flow was evaluated by measuring the proximal point where the ICG could be observed 5 minutes after rest and 15 minutes after a walking exercise. Results In the controls, lymph flow was stable at rest and was well enhanced by exercise. In patients with early-stage lymphedema, lymph flow was already enhanced at rest (p = 0.005) and was further enhanced by exercise. In advanced-stage lymphedema, lymph flow was not enhanced, even by exercise (p = 0.001). Conclusion ICG-LG could evaluate lymph flow and functions of lymph systems and detect accelerated lymph flow in early-stage secondary lymphedema. Detecting accelerated lymph flow may facilitate early detection and treatment of secondary lymphedema.