Identifying Functional Lymph Nodes in Lower Extremity Lymphedema Patients: The Role of High-frequency Ultrasound

Background Lymph nodes may play a potential role in lymphedema surgery. Radiologic evaluation of nodes may reveal the status of pathologic conditions but with limited accuracy. This study is the first to evaluate the efficacy of ultrasound in detecting functioning nodes in lymphedema patients and presents a criterion for determining the functionality of the lymph nodes. Methods This retrospective study reviews 30 lower extremity lymphedema cases which were candidates for lymph node to vein anastomosis. Lymphoscintigraphy and magnetic resonant lymphangiography (MRL) imaging were compared with ultrasound features which were correlated to intraoperative indocyanine green (ICG) nodal uptake as an indication of functionality. Results Majority were International Society of Lymphology stage 2 late (50.0%) and stage 3 (26.7%). ICG positive uptake (functioning nodes) was noted in 22 (73.3%), while 8 patients (26.6%) had negative uptake (nonfunctioning). Ultrasound had significantly the highest specificity (100%) for identifying functional nodes followed by lymphoscintigraphy (55%) and MRL (36%; p = 0.002 , p < 0.001 , respectively). This was associated with 100% positive predictive value compared against lymphoscintigraphy (44%) and MRL (36%; p < 0.001 for both ). The identified ultrasound imaging criteria for functioning lymph node were oval lymph node shape (Solbiati Index), morphology, vascularity pattern, and vascularity quantification. Conclusion The use of ultrasound in nodal evaluation was proven effective in different pathologic conditions and demonstrated the best prediction for functionality of the lymph node based on the new evaluation criteria.