Magnetic Resonance Lymphangiography: Establishing Normal

BACKGROUND: Despite an increased interest in visualising the lymphatic vessels (lymphatics) with Magnetic Resonance Lymphangiography (MRL), there remains little literature describing their appearance in non-lymphoedematous individuals. To determine lymphatic abnormalities, an understanding of how healthy lymphatics appear and behave needs to be established. In this study, MRL of individuals without a history of lymphatic disease was therefore performed. METHODS: A total of 25 individuals (15 female) underwent MRL of their lower limbs using a 3.0T Philips MRI scanner. The first 9 cases were recruited to establish the concentration of Gadolinium-based contrast agent (GBCA) to administer, with the remainder imaged pre- and post-inter-digital forefoot GBCA injections at the optimised dose. Outcomes including lymphatic vessel diameter, tortuosity and the frequency of drainage via particular drainage routes were recorded. RESULTS: Healthy lymphatics following the anteromedial pathway were routinely observed in post-contrast T1 weighted images (average tortuosity = 1.09 ±0.03), with an average of 2.16 ± 0.93 lymphatic vessels, of diameter 2.47 ± 0.50 mm, crossing the anterior ankle. In six limbs, vessels following the anterolateral pathways were observed. No vessels traversing the posterior of the legs were seen. In a subset of ten vessels lymphatic signal, measured at the ankle, peaked 29:50 ± 09:29 mm:ss after GBCA administration. No lymphatic vessels were observed in T2 weighted images. CONCLUSIONS: Contrast-enhanced MRL reliably depicts the lymphatics in the legs of healthy controls. Following inter-digital contrast injection, anteromedial drainage appears dominant. Quantitative measures related to lymphatic vessel size, tortuosity and drainage rate are readily obtainable, and could be beneficial for detecting even subtle lymphatic impairment.