Indocyanine green fluorescent lymphography Lymphaticovenular shunt

Background: Visualisation of the lymphatic system is a challenging task. Recently, an indocyanine green (ICG) fluorescent lymphography system was developed for visualising the lymphatic vessels. ICG emits energy in the near-infrared region between 840 and 850 nm when it is bound to protein in the tissue. Aim: To use ICG fluorescent lymphography to identify locations of the lymphatic vessel for lymphovenous shunt. Methods: The lymphatic anatomy in the upper extremity was investigated using ICG fluorescent lymphography in 3 healthy volunteers and 15 patients with breast cancer-related lymphoedema prior to them undergoing lymphaticovenular bypass. Results: In healthy volunteers, fluorescent images of lymphatic vessels emerged at the dorsal hand as a shiny linear pattern and ran longitudinally towards the proximal arm after a few minutes. In lymphoedema patients, the lymphatic vessels could be identified at the dorsal hand, but the appearance of the lymphatic structure varied between patients. Conclusions: ICG fluorescent lymphography allows for the prompt identification of the lymphatic vessels and has the potential to improve the outcomes of lymphovenous shunt operations and for use as a diagnostic tool. Declaration of interest: None. Hiroo Suami, David Chang, Roman Skoracki, Kiyoshi Yamada, Yoshihiro Kimata Using indocyanine green fluorescent lymphography to demonstrate lymphatic architecture 25 Visualisation of the lymphatic system is a challenging task. The collecting lymphatic vessels are small in size, with diameters of between 0.2 and 1.0 mm, lymphatic fluid is colourless, and our knowledge of lymphatic system anatomy is uncertain. Lymphatic vessels contain numerous valves at short intervals. They regulate lymphatic flow from distal to proximal, and, therefore, lymphatic tracers have to be injected in the distal sites. The current mainstay of lymphatic imaging is lymphoscintigraphy using radionuclide tracers, which has become a standard preoperative imaging study for breast and skin cancer patients to help detect the sentinel lymph node/s to which the lymphatic vessels from the primary cancer site drain (Morton et al, 1992; Giuliano et al, 1997; Uren et al, 1999). However, this procedure needs to be performed in a radiology room and the low-resolution 2-dimensional images are not suitable for demonstrating fine lymphatic capillaries. Recently, an indocyanine green (ICG) fluorescent lymphography system was developed for visualising the lymphatic vessels (Giuliano et al, 1997; Kitai et al, 2005; Murawa et al, 2007; Ogata et al, 2007; Unno et al, 2007; Tsujino et al, 2009). Indocyanine green (ICG) is a water-soluble compound that has been widely used for assessing cardiac output, hepatic function, and ophthalmic angiography for more than half a century. ICG contains sodium iodide and should be used with caution in patients with a history of iodide allergy. Although previous diagnostic examinations used its absorption spectra, ICG also emits energy in the near-infrared region between 750– 810 nm when bound to protein in the tissue (Benson and Kues, 1978). This feature is advantageous for investigating deep-tissue structures because nearinfrared radiation can penetrate tissue without the interference suffered by visible-wavelength radiation, which can be absorbed by haemoglobin and water.