Classification of the lymphatic pathways in each lymphosome based on multi-lymphosome indocyanine green lymphography: Saphenous, calf, and thigh (SCaT) classification.

BACKGROUND

The anatomy of the lymphatic vessels in the extremities is not completely understood. The aim of this study was to elucidate the patterns of the lymphatic pathways of each lymphosome in lymphedematous legs.

METHODS

We performed a retrospective study on 630 lymphosomes from 105 patients with leg lymphedema. The mean age of the subjects was 58.9 (range: 20-91) years, and the mean duration of lymphedema was 8.8 (range: 1-91) years. In indocyanine green (ICG) lymphography, we injected ICG into the multi-lymphosome: the first web space of the foot (saphenous lymphosome), lateral ankle (lateral calf lymphosome), and lateral knee (lateral thigh lymphosome). We established the saphenous, calf, and thigh (SCaT) classification based on the lymphatic location: lymphatic vessels on the medial side (type 1) and lymphatic vessels in other locations (type 2).

RESULTS

In the saphenous lymphosome, 157 lymphatics (95.5%) were type 1. In the lateral calf lymphosome, 164 lymphatics (29.9%) were type 1. In the lateral thigh lymphosome, 148 lymphatics (16.9%) were type 1. The percentage of type 2 lymphatic vessels increased as the lymphoscintigraphic staging progressed.

CONCLUSIONS

The lymphatic vessels in the lymphedematous legs shifted from the medial to the lateral side and finally disappeared in all lymphosomes as lymphedema worsened. We propose the SCaT classification to describe the condition of the lymphatic vessels in each lymphosome with the hope that it becomes a common staging system for sharing information on lymphedema severity among interdisciplinary medical professionals.