Measuring Lymph Flow Velocity in Lymphatic Collecting Vessels Using a Transit Time Ultrasound Flowprobe

Background: Lymph flow measurements can assist in attaining a better understanding of the lymphatic system's function and its diseases. However, in vivo assessment of lymph flow has been challenging. Transit-time ultrasound technique (TTUT) provides direct quantitative lymph flow values and has been used to successfully measure lymph flow in patients with secondary lymphedema. Currently, no measurements using TTUT in healthy subjects have been reported. The aim of this study is to measure lymph flow in healthy subjects using the TTUT. Methods and Results: Twenty consecutive patients who had an indication for a free radial forearm flap (FRFF) reconstruction were included in the study. Patients with scars on their arms, a history of extremity lymphedema, metastatic disease, or axillary node dissection were excluded. The Transonic® Microvascular Flow Probe was used to measure lymph flow during FRFF reconstruction in accordance with the Transonic® protocol for Quantitative Patency Assessment. The subdermal superficial lymphatic collecting vessels had a mean diameter of 0.40 ± 0.10 mm (range: 0.3-0.5 mm) and a mean lymph flow velocity of 0.45 ± 0.48 mL/min (range: 0.08-1.68 mL/min). Neighboring subdermal veins measured had a mean diameter of 0.48 ± 0.11 mm (range: 0.03-0.7 mm) and a mean blood flow velocity of 0.96 ± 1.73 mL/min (range: 0.07-7.40 mL/min). Conclusion: The TTUT is a viable method to measure real-time lymph flow velocities in healthy subjects. Future studies with a larger sample size are required to validate the TTUT measurement accuracy and establish clinical correlations.