Echoes of Fascia: Ultrasound Mapping of Superficial Fascia and Lymphatic Vessels in Lymphedematous Limbs.

Objectives: Although collecting lymphatic vessels are known to run beneath the superficial fascia, its ultrasonographic features, particularly in lymphedematous limbs, remain poorly understood. This study aimed to evaluate the structure of the superficial fascia and its relationship with lymphatic vessels. Methods: We analyzed the patients with secondary lower extremity lymphedema who underwent lymphaticovenous anastomosis under local anesthesia. Ultrasound images were obtained at four anatomical sites: 5 cm and 10 cm distal to the saphenofemoral junction and the popliteal fossa. Sites where lymphatic vessels could not be visualized by ultrasound were excluded. The superficial fascia was scored for clarity (0-4), and the number of fascia was counted. Measurements included the superficial fascia depth (shallowest and deepest), amplitude of undulation, and the depth and relative position of lymphatic vessels. Results: Of the 42 limbs (168 sites) in 21 patients, 158 sites were included. The superficial fascia was more clearly visualized in the thigh than in the calf, with visibility decreasing as lymphedema severity advanced. Lymphatic vessels were located at a mean depth of 7.0 mm, also increasing with severity, while the vessel-fascia distance (mean, 1.1 mm) showed no association. The number of fascial layers averaged 2.6, more in the thigh than in the calf, and 96.2% of lymphatic vessels lay beneath the first or second fascial layer. Conclusions: Lymphatic vessels are typically located just beneath the first or second superficial fascial layer, and ultrasound evaluation of fascia provides practical landmarks for preoperative mapping in lymphedema.