Magnetic resonance lymphangiography: How to prove it?

Abstract

We found interest in the article by Mitsumori et al that reported their experience of magnetic resonance lymphangiography (MRL).1 We congratulate Mitsumori et al on their article on the four consecutive patients studied; however, some critical aspects in the text should be pointed out. For example, Mitsumori et al report a literature review of lymphaticovenular anastomosis (LVA) treatments, but do not report if the four patients affected by lymphedema referred to in that article were operated on with LVA, and the data regarding the postoperative outcomes are not present. MRL has been previously studied for lymphedema diagnosis and staging: Recently at the Lymphoedema Mondial Congress in Rome, 2013, and the International Lymphoedema Congress in Genova, 2014, many criticisms were raised against the use of MRL and the possible discrimination between lymphatic and venous vessels. Lohrmann et al reported the visualization of venous vessels, as contrast may be captured by both lymphatic and venous capillaries: venous vessels resulted in contrast enhancement faster than lymphatic vessels, which were slower.2 In a lymphedematous limb the diffusion of the contrast in the venous system may be modified due to the previous surgery. Further resonance imaging of lymphatic vessels may be even more doubtful on nonedematous limbs.3 Another aspect that evoked our attention in the Mitsumori et al article is their criticism of indocyanine green (ICG) lymphography: this minimally invasive imaging technique is more accepted by patients than a 2-hour MRL, it is easy to repeat, and the costs are reduced compared to MRL: further, no pain is usually referred by the patients, while Mitsumori et al report mild to moderate pain in the four patients who received the gadobenate (Gd) contrast injections. Mitsumori et al refer only to the Chang et al3 and Ogata et al4 studies regarding ICG lymphography, while recent articles reported even more advantages from the use of this technique.4-6 The main doubtful aspect of this article is their difficulty in proving that the identified vessels are really lymphatic vessels: the absence of an MRL performed on healthy limbs reduces the proof of the results of this article. In comparing ICG lymphography to MRL in a limb of healthy patients, we may observe numerous lymphatic vessels in the ICG lymphography that are not reported in the MRL (Fig. 1). To prove this theory, our multidisciplinary study group is performing a study of MRL performed on lymphedema patients enrolled for LVA and histological examination of biopsy specimens of the vessels identified at the MRL. We will soon submit this article. In conclusion, we appreciate the literature review of Mitsumori et al in their article and we hope to prove the usefulness of MRL in imaging and staging lymphedema patients. The authors declare no conflicts of interest.