SLR - June 2020 - Kentston C. Cripe
Reference: Shinaoka A, Koshimune S, Suami H, Yamada K, Kumagishi K, Boyages J, Kimata Y, Ohtsuka A.Lower-Limb Lymphatic Drainage Pathways and Lymph Nodes: A CT Lymphangiography Cadaver Study. Radiology. 2020 Jan;294(1):223-229.Scientific Literature Review
Reviewed By: Kentston C. Cripe, DPM
Residency Program: Creighton University – Phoenix, AZ
Podiatric Relevance: Knowledge of the lymphatic drainage of the lower extremity is crucial for diagnostic assessment of lymphedema as well as the spread of infection or malignancy. It also has implications in plastic surgery and can be used in conjunction with known angiosomes to influence perforator flap selection. This study demonstrates suitable tracer injection sites for comprehensive imaging of the lymphatics of the lower extremity. Lymphatic pathways consist of relationships between lymphatic groups and corresponding regional lymph nodes. To date no standard protocol exists for the comprehensive imaging of lower extremity lymphatics. This study set out to determine the three-dimensional relationships between these groups and lymph nodes.
Methods: One hundred thirty lower limbs from 83 cadavers were studied using indocyanine green (ICG) lymphography to identify the lymphatic vessels and computed tomography (CT) imaging was used to determine the three-dimensional relationship between the lymphatic vessels and their regional lymph nodes. The ICG lymphography was performed along 19 predetermined injection sites and lymphatic vessels were identified with a near-infrared camera system. Hand massage was continued until ICG was visualized above the knee. The CT lymphangiography utilized iodized oil with diethyl ether injected following cannulation of lymphatic vessels under direct microscopic visualization. The superficial inguinal nodes were subdivided into five regional groups divided by the great saphenous vein and horizontally at the saphenofemoral junction. Popliteal nodes were divided into deep and superficial based on their relationship with the deep fascia. Locations of nodes were documented and categorized based on initial drainage “first-tier” or subsequent “second-tier” nodes.
Results: Four lower extremity lymphatic pathways were identified consisting of the anteromedial, anterolateral, posteromedial, and posterolateral which primarily drain to two nodes in the superficial inguinal region and one node in the popliteal region. Seventy-three percent of lower extremity lymphatic drainage is received by three lymph nodes in two inguinal regions and one lymph node in the popliteal region. Only the posterolateral lymphatics were demonstrated to connect to the popliteal lymph node. Conventional lymphangiography protocols with webspace injections only demonstrated the anteromedial pathway.
Conclusions: This study demonstrates the need for additional injection sites around the foot for comprehensive analysis of lower extremity lymphatic pathways and regional lymph nodes. These results are highly relevant to lower extremity surgery and have implications in traumatic injuries as well as surgical management from incisional approach selection, subsequent dissection, debridement, and closure as violation of lymphatic pathways can lead to postoperative lymphedema and increase predisposition to skin breakdown and infection. These pathways can also be utilized to predict spread of metastatic disease from neoplastic disorders to infection. Similar to known dermatomes and angiosomes, the lymphatic pathways of the lower extremity visualized in this study are of high clinical relevance and the ability to effectively map them is a useful tool for any physician involved in the treatment of lower extremity pathology.