Retrograde lymph flow in the lymphatic vessels in limb lymphedema

Objective: Retrograde movement of lymph owing to damaged and/or incompetent valves in the lymphatic vessels has been considered a pathological feature of lymphedema. This study aimed to determine the prevalence of retrograde lymph flow and the characteristics of patients with this condition using indocyanine green (ICG) lymphography. Methods: An audit of 679 patients with upper or lower limb swelling who underwent ICG lymphography was undertaken over a 4-year period. Harvey's technique was applied to identify retrograde flow in the lymph collecting vessel during ICG lymphography. The characteristics of patients with retrograde lymph flow were recorded. Results: Twenty-one patients (3.7%; lower limb, n = 19; upper limb, n = 2) were identified as having retrograde flow in lymph collecting vessels out of 566 confirmed lymphedema patients (lower limb, n = 275; upper limb, n = 291). Of the two patients with upper limb lymphedema (ULLE), one had a short segment of retrograde lymph flow in the forearm. The other patient with ULLE and one patient with lower limb lymphedema (LLLE) were previously diagnosed with lymphedema-distichiasis syndrome. Of the remaining 18 patients with LLLE and retrograde lymph flow, nine had initiating insect bites with lymphangitis and three had palpable benign enlarged inguinal lymph nodes evident before lower limb swelling onset. None had cancer-related LLLE. Conclusions: Retrograde lymph flow with valve incompetence in the lymph-collecting vessels was a rare finding in ULLE and a relatively uncommon finding in LLLE, contradicting the conventional understanding of pathological changes in lymphedema. ICG lymphography identified anticipated retrograde lymph flow in two patients with lymphedema distichiasis. In the remaining patients, retrograde lymph flow may have resulted from toxic or asymptomatic lymphangitis but there was no association with secondary cancer-related lymphedema. These findings have implication for conservative management as well as lymphovenous anastomosis surgery where both ends of a transected lymph collecting vessel would be potential targets for anastomoses.