Lymphatic regeneration following microvascular limb replantation: a qualitative and quantitative animal study

Lymphatic regeneration following unilateral hindlimb autotransplantation was studied in 14 Lewis rats using Technetium-99 radiolabeled sulfur colloid (TC-99) lymphoscintigraphy and compared to the lymphatic pattern exhibited in four unoperated control rats. Control animals demonstrate a reproducible flow of lymph along the deep lymphatic system from the foot, draining into the ipsilateral inguinal nodes, and then up to the para-aortic nodes. Following replantation, lymphatic outflow from the replanted limb begins to occur within 3 to 6 days, reaching normal lymphatic clearance within 12 days. However, the pattern of lymphatic flow is ill-defined, relying on multiple small channels of the superficial lymphatic system. In contrast to controls, at 3 hr post TC-99 injection, lymphatic drainage in replanted rats is via the inguinal and axillary nodal regions bilaterally. This abnormal pattern persisted in the replanted animals for the duration of this study, 160 days. It is evident that lymphatic regeneration in this animal model is associated with a rapid return to normal levels of lymphatic clearance via collateral channels within the subcutaneous tissue. The rapidity with which lymphatic drainage is restored, and its localization within the subcutaneous tissue, can explain why replanted tissues and microvascular free flaps seldom develop lymphedema. In addition, the rat hindlimb replantation model may prove useful for studies of the general mechanisms and specific factors responsible for lymphangiogenesis.