Correlations Between Tracer Injection Sites and Lymphatic Pathways in the Leg: A Near-Infrared Fluorescence Lymphography Study

Background: The primary aim of this study was to determine the detailed anatomy of the lymphatics in the lower extremity using fresh human cadavers with indocyanine green fluorescence lymphography. The secondary aim was to apply the anatomical results to establish a new protocol for lymphography based on feasible allocations for tracer injection sites. Methods: One hundred lower extremities from 53 fresh human cadavers were used for this study. The authors injected indocyanine green solution subcutaneously at 19 points around the foot along the borderline between the dorsum and planta according to anatomical landmarks. Immediately after the indocyanine green injections, gentle hand massage was applied at each injection site to facilitate indocyanine green uptake into the lymphatic vessels. Fluorescent images of the lymphatics were obtained using a near-infrared camera system. Imaging data of the lymphatics were analyzed to find correlations between the injection sites and the identified lymphatic vessels. Results: The lymphatic system in the lower extremity was divided into four distinct lymphatic groups: anteromedial, anterolateral, posterolateral, and posteromedial. The lymphatic vessels in all except the posterolateral group connected to the inguinal nodes, and those in the posterolateral group connected to the popliteal nodes. The authors successfully elucidated correlations between the injection sites in the foot and each lymphatic group. Conclusion: The new classification of the four lymphatic groups in the lower extremity and identification of their origins in the foot enabled the authors to propose a new protocol for lymphography that includes four injection sites in specific circumflex locations.