LYMPHATIC REGENERATION FOLLOWING MICROVASCULAR LIMB REPLANTATION - A QUALITATIVE AND QUANTITATIVE ANIMAL STUDY

Lymphatic regeneration following unilateral hindlimb autotransplantati on was studied in 14 Lewis rats using Technetium-99 radiolabeled sulfu r colloid (TC-99) lymphoscintigraphy and compared to the lymphatic pat tern exhibited in four unoperated control rats. Control animals demons trate a reproducible flow of lymph along the deep lymphatic system fro m the foot, draining into the ipsilateral inguinal nodes, and then up to the para-aortic nodes. Following replantation, lymphatic outflow fr om the replanted limb begins to occur within 3 to 6 days, reaching nor mal lymphatic clearance within 12 days However, the pattern of lymphat ic flow is ill-defined, relying on multiple small channels of the supe rficial lymphatic system. In contrast to controls, at 3 hr post TC-99 injection, lymphatic drainage in replanted rats is via the inguinal an d 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 associa ted with a rapid return to normal levels of lymphatic clearance via co llateral channels within the subcutaneous tissue. The rapidity with wh ich lymphatic drainage is restored, and its localization within the su bcutaneous tissue, can explain why replanted tissues and microvascular free flaps seldom develop lymphedema. In addition, the rat hindlimb r eplantation model may prove useful for studies of the general mechanis ms and specific factors responsible for lymphangiogenesis.