Clinical Characteristics and Implications of Indocyanine Green Lymphography-Identified Contralateral Inguinal Pathway of Lower-Limb Lymphedema

Background and Objectives: The contralateral inguinal pathway (CIP) to the inguinal nodal region of the contralateral limb has been described in lower-limb lymphedema (LLLE). This audit aimed to use indocyanine green (ICG) lymphography to determine characteristics of patients with CIP to inform conservative therapy. Methods: Patients with confirmed LLLE (n = 278) were categorized into secondary cancer-related (n = 82), secondary non–cancer-related (n = 86), or primary (n = 110). Patient characteristics, limb volume and bioimpedance spectroscopy (BIS) extracellular fluid ratio, and ICG lymphography of lymphatic pathways and dermal backflow areas were recorded. Results: Forty-seven patients (16.9%) had movement of ICG dye via CIP. Of these, 30 (63.8%) had secondary cancer-related, 8 (17.0%) had secondary non–cancer-related, and 9 (19.1%) had primary LLLE. Cancer-related LLE (P < .001) and unilateral LLLE (P = .017) were significant indicators of CIP, with 36.6% of patients with cancer-related LLLE demonstrating this pathway. CIP was significantly associated with dermal backflow in shin (P = .016), calf (P = .006), thigh (P < .001), inguinal (P < .001), pubic (P < .001), and abdominal regions (P = .001). Patients with CIP had significantly higher volume differences between limbs (P < .001), severity of lymphedema (P < .001), and BIS measurements (P < .001) than patients without CIP. Conclusion: A compensatory lymphatic drainage pathway from the affected limb to the contralateral inguinal lymph node region was evident in 16.9% of patients with LLLE. This pathway was most observed in unilateral cancer-related lymphedema, particularly where edema was present in proximal thigh, inguinal, pubic, and lower abdominal regions. Directing manual lymphatic drainage to the contralateral inguinal drainage region should be considered especially for patients with cancer-related LLLE.