Changes in the Diameter of Lymphatic Vessels and Veins Due to Body Position, Evaluated by Ultrasound

<b><i>Background:</i></b> The purpose of this study was to clarify how lymphatic vessels and veins change when body position is changed in lower limbs affected by lymphedema. <b><i>Methods:</i></b> We performed a retrospective study of 18 consecutive patients (33 limbs) who underwent lymphaticovenous anastomosis (LVA) for lower limb lymphedema. We performed ultrasound to detect the suitable lymphatic vessels and veins preoperatively, applying the index of D-CUPS (Doppler, Crossing, Uncollapsible, Parallel, and Superficial fascia) to identify lymphatic vessels. We measured the vertical diameter of the lymphatic vessels and veins in each incision site for LVA using ultrasound with the patients lying, sitting, and standing, and a Student's <i>t test</i> was performed. <b><i>Results:</i></b> The mean age of the participants was 61.8 years old, and the mean body mass index was 21.7 (range: 18.3-28.1). Thirty-eight sites on the 30 thighs and 21 sites on the 18 calves were evaluated. The diameter of veins increased significantly when changing from a lying to a sitting or a standing position (thigh: <i>p</i> < 0.01, calf: <i>p</i> = 0.016 and 0.015, respectively), but lymphatic vessels did not (thigh: <i>p</i> = 0.65, calf: <i>p</i> = 0.60 and 0.36, respectively). A weak correlation was found between dilatation rates of veins and lymphatic vessels in the calf (r = 0.39, <i>p</i> = 0.030). <b><i>Conclusion:</i></b> The veins dilated significantly when the body changed from the supine to standing position, but the lymphatic vessels did not. Similar studies with a larger number of cases are desirable in the future.