Indocyanine green lymphography imaging of normal lymphatic drainage in the lower limbs

Objectives: Indocyanine green lymphography (ICGL) has emerged as a potentially powerful tool for the study of the superficial lymphatic system and to support the diagnosis of lymphoedema. However, detailed descriptions of ICGL findings in healthy individuals are limited. In this study, we imaged a series of healthy participants using ICGL, attempting to establish quantitative and qualitative ICGL parameters of the lower limb. Methods: Sixteen healthy individuals aged 20-55 years were recruited to undergo lower limb ICGL after 0.1 mL injections of 1 g/L ICG were administered intradermally to 5 locations around the foot. Outcome measures included: (1) the drainage routes of contractile lymphatic collectors observed, (2) the number of lymphatic vessels crossing the anterior ankle, and (3) the pumping frequency of lymphatic vessels. Abnormal features, such as highly tortuous or vessels with retrograde lymph flow, were noted. Results: Propulsion of ICG containing lymph could be seen in all individuals, with drainage via the anteromedial and anterolateral drainage pathways predominating (observed in 31/32 and 25/32 limbs, respectively). The number of lymphatic vessels crossing the anterior ankle was 3.4 ± 1.1 with an average rate of 1 propulsion every 66 seconds in the vessels investigated. Isolated cases of highly tortuous and refluxing vessels were observed. Conclusions: Although limited by absorption and scatter of infrared light, ICGL facilitated the characterization of normal lower limb lymphatic vessels through a rigorous set of objective measures. This in turn will allow better identification of pathological changes. Advances in knowledge: Establishment of normal lower limb lymphatic anatomy and function.