High-frequency ultrasound combined with microbubbles for preoperative lymphatic mapping for lymphedema with a non-linear pattern in indocyanine green lymphography

OBJECTIVES: Lymphatic-venous anastomosis (LVA) is an effective surgical treatment for lymphedema, which requires accurate identification of lymphatic vessels. Indocyanine Green (ICG) lymphography, the most common method for lymphatic mapping, cannot always successfully identify lymphatic vessels. We aimed to explore high-frequency ultrasound (HFUS) and contrast-enhanced ultrasound (CEUS) as a reliable alternative for lymphatic mapping when ICG lymphography is not feasible. MATERIALS AND METHODS: We performed combined HFUS and CEUS for lymphatic mapping on the patients who exhibited no obvious linear pattern on ICG lymphography. The inner and outer diameters and depths of the lymphatic vessels were measured. We subsequently evaluated the accuracy of US lymphatic mapping by comparing it with the operative results. And the postoperative volume and circumference of the affected limbs were compared with the preoperative measurements. RESULTS: We recruited 111 patients with lymphedema, including 96 limbs and 24 perineal areas affected. Three hundred forty-five lymphatics in the limbs and 52 in the perineum underwent anastomosis and were analyzed. Comparable lymphatic vessel diameter (inner: 0.5-0.9 mm; outer: 0.8-0.9 mm) and depth (9-10 mm) measurements across HFUS, CEUS, and combined HFUS + CEUS. However, HFUS + CEUS significantly improved detection sensitivity, identifying 313 vessels (91.1% accuracy) vs 114 (88.6%) for HFUS and 22 (90.9%) for CEUS. Significant postoperative reductions in limb circumference (39.3 ± 7.4 cm to 37.8 ± 7.1 cm) and volume (8.23 ± 3.63 L to 7.52 ± 3.39 L, p < 0.001). All ultrasound methods consistently showed volume reduction (HFUS: 9.37 ± 2.93 L to 8.46 ± 2.01 L; CEUS: 9.46 ± 2.57 L to 9.09 ± 2.45 L; HFUS + CEUS: 9.30 ± 3.21 L to 8.07 ± 3.12 L, p < 0.001-0.002). CONCLUSIONS: High-frequency US combined with CEUS serves as a reliable pre-op lymphatic mapping alternative when ICG lymphography fails. KEY POINTS: Question In over 40% of lymphedema patients, preoperative ICG lymphangiography fails to show a linear pattern; can HFUS and CEUS provide complementary information? Findings ICG failed to visualize in 42.53% of patients; HFUS and CEUS identified lymphatics in all and achieved 94.5% accuracy. Clinical relevance This study confirmed that HFUS combined with CEUS improves the detection of lymphatic vessels and the success of LVA in ICG-negative cases.