Introduction/Background It is said that lymphedema develops in 20–40% of patients after pelvic lymphadenectomy in gynecological surgery. While several risk factors have been shown, many patients develop lymphedema without them. We therefore hypothesized that innate lymphatic function and morphology contribute to the development of lymphedema. In this study, to elucidate the mechanism of lymphedema from the aspect of lymphatic function, we evaluate the changes in the lymph duct before and after surgery using indocyanine green (ICG) fluorescence lymphangiography.

Methodology From November 2019, we started the study as a specified clinical trial. We planed to perform ICG fluorescence lymphangiography four times, preoperatively and 1.3.9 months after operation, to the patient who were scheduled pelvic lymphadenectomy due to the gynecological malignant cancer. In addition to the ICG fluorescence lymphangiography, we also analyzed physical findings.

Results By the present, we have performed the test on 14 patients including 6 cervical cancer, 7 corpus cancer and 1 fallopian tube cancer. So far, we have obtained the following three new findings. (1) If a patient already has lymphedema preoperatively, there is no improvement after lymphadenectomy; (2) Lymphedema that was present at 1 month after surgery may improve over time; and (3) Though the lymphangiography pointed out the lymphedema without subjective symptoms, lymphedema may become apparent later.

Conclusion The results of the intermediate analysis to the present show significant findings that innate lymph duct function and morphology may be involved in the development of lymphedema. The final evaluation will be made at the time of 30 cases registered for this study.