Anatomic and functional evaluation of the lymphatics and lymph nodes in diagnosis of lymphatic circulation disorders with contrast magnetic resonance lymphangiography.

Objectives: Owing to its structural and anatomic characteristics, imaging of the lymphatic system has been difficult. The conventional diagnostic method of radionuclide-based imaging has the disadvantage of poor resolution. Recent work has shown that magnetic resonance imaging (MRI) can depict lymphatic channels in patients with lymphedema. This study evaluated the anatomic and functional images of contrast MR lymphangiography in the diagnosis of limb lymphatic circulation disorders.

Methods: The study enrolled 27 patients with primary lymphedema. Four patients had bilateral disease, and 23 had unilateral disease. Contrast-enhanced lymphangiography was performed with a 3.0-T MR unit after the intracutaneous injection of gadobenate dimeglumine into the interdigital webs of the dorsal foot. The kinetics of enhanced lymph flow within the lymphatic system were calculated using the formula [speed in cm = total length of visualized lymph vessel in cm/inspection time in minutes] and by comparing dynamic nodal enhancement and time-signal intensity curves between edematous and contralateral limbs. Morphologic abnormalities of the lymphatic system were also evaluated.

Results: Examination of the MRIs after injection of the contrast agent showed enhanced lymphatic channels consistently visualized in all clinical lymphedematous limbs and in five contralateral limbs of unilateral lymphedema patients. The speed of flow within the lymphatics of lymphedematous limbs was 0.3 to 1.48 cm/min. Contrast enhancement in inguinal nodes of edematous limbs was significantly less than that of contralateral limbs (P < .01). Dynamic measurement of contrast enhancement showed a remarkable lowering of peak time (P < .01) and peak enhancement (P < .01), and a delay in outflow in inguinal nodes of affected limbs compared with that of control limbs. Postcontrast MRI also depicted varied distribution patterns of lymphatics and abnormal lymph flow pathways within lymph nodes in the limbs with lymphatic circulation disorders.

Conclusion: Contrast MR lymphangiography with gadobenate dimeglumine is capable of visualizing the precise anatomy of lymphatic vessels and lymph nodes in lymphedematous limbs. It also provides information concerning the functional status of lymph flow transport in the lymphatic vessels and lymph nodes of these limbs.