Lower limb lymphedema is difficult to prevent and diagnose early because its natural history is unclear. Therefore, the aim of this study was to clarify its pathogenesis and to identify risk factors that may lead to early diagnosis. In 29 patients, aged 25 to 74 years with cervical, uterine, or ovarian cancer who underwent pelvic lymphadenectomy, indocyanine green fluorescence lymphangiography was performed with an infrared camera system, and lymph pumping pressure was measured indirectly preoperatively, and one, two, three, and six months postoperatively. Of these 29 patients, 22 (75.9%) completed the examinations. In the non-lymphedema group, the average lymph pumping pressure did not change significantly at postoperative follow-up compared with preoperative values. On the other hand, lymph pumping pressure increased at various time points in five patients who developed early lymphatic changes with dermal diffusion at the level of the proximal femur. An increase in lymph flow path resistance due to pelvic lymphadenectomy resulted in an initial increase in lymph pumping pressure, followed by a subsequent decrease, in the early lymphatic changes group. This trend in the pressure change signifies that the lymph vessels became dysfunctional as they were overwhelmed by the overload condition and this feature may be a clinically useful signal for the early diagnosis of developing lymphedema.