Magnetic resonance imaging in human lymphedema: comparison with lymphangioscintigraphy.

Magnetic resonance (MR) imaging and isotope lymphography (lymphangioscintigraphy, LAS) was done in 32 patients with peripheral lymphedema (19 primary and 13 secondary). MRI characteristically showed diffuse dermal and subcutaneous edema, a nonedematous, occasionally hypertrophied skeletal muscle compartment, variability in regional lymph node size and appearance depending on the underlying clinical disorder, serpiginous "channels" or "lakes" consistent with dermal collateral lymphangiectasis and sequestered lymph, and increased subcutaneous fat. In contrast, LAS showed dermal diffusion ("backflow"), cross-over with retrograde tracer backflow (reflux), delayed tracer transport, and depending on the cause of lymphedema (i.e., primary or secondary), discrete or poorly defined lymph trunks (tracer "bands") and delayed or nonvisualization of regional lymph nodes. Although not a first-line clinical test, MR particularly in conjunction with LAS noninvasively provides accurate anatomical definition of the peripheral lymphatic system. In contradistinction to LAS, MR can visualize lymph trunks, nodes, and soft tissues proximal to sites of lymphatic obstruction. Together these imaging modalities may substitute for conventional oil contrast lymphography in the evaluation of the pathogenesis and evolution of most lymphologic disorders.