Magnetic resonance lymphangiography (MRL) is an imaging technique used to visualize and map the lymphatic vessels. The technique is used for treatment planning in supermicrosurgical procedures, including lymphaticovenous anastomosis, lymphaticolymphatic bypass and vascularized lymph node transfers. When gadolinium-based contrast medium (GBCM) is injected directly into groin lymph nodes, intra-nodal dynamic contrast-enhanced (DCE) MRL can be used to study central conducting lymphatics and aid in the evaluation of pulmonary lymphatic perfusion syndromes (such as plastic bronchitis), chylothorax, neonatal lymphatic disorders, chylous ascites and protein-losing enteropathies 2.
The technique requires an MRI with a field strength of 1.5 T or greater and access to a multielement coil. Both phased-array peripheral vascular coils and body array coils are reported to provide good signal-to-noise ratios 1.
For limb lymphatic disorders, a 0.1 mmol/kg body weight dose mixture of gadobenate dimeglumine and 1% lidocaine is injected intradermally or subcutaneously in the region of interest. The patient is subsequently imaged using a 3D fast spoiled gradient-echo T1-weighted sequence with a fat-saturation technique to facilitate visualization of the lymphatics. Subtraction of a precontrast study from a post-contrast study has also been reported in the literature as a method to increase the apparent contrast in the examination 1.
For intra-nodal DCE MRL, small needles (e.g. 25-gauge) are usually inserted bilaterally into groin lymph nodes under ultrasound guidance with subsequent slow injection of GBCM and imaging roughly every minute with a high spatial and temporal resolution MRI sequence 2,3.
Practical points
lymphatic channels are vary in caliber, appears beaded and irregular, when compared to subdermal veins that are smooth with uniform caliber 4
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on dynamic series, lymphatic enhancement increases and progresses proximally with time; meanwhile, venous enhancement reduces over time 4