MRI can also be useful in the differential diagnosis of lymphedema [8–10]. In edema due to venous disease both the epifascial and subfascial compartments may be affected; the characteristic reticular pattern may or may not present. While in lipidemia, the fat accumulation occurs without signs of lymphatic congestion or reticular appearance [10]. The anatomic details provided by MRI may complement the functional assessment provided by lymphoscintigraphy and can be occasionally necessary to establish the diagnosis [11].

MRI may be helpful in differentiating the various causes of lymphatic obstruction in secondary lymphedema by demonstrating dilated lymphatic trunks and identification of abnormal lymph nodes. Malignant nodal involvement can be assessed further by lymphotropic nanoparticle-enhanced magnetic resonance imaging (LNMRI). These nanoparticles produce a significant susceptibility effect which can be detected as a drop in signal intensity on T2-weighted images [12]. Within a normal lymph node, nanoparticles accumulate within the reticuloendothelial system (phagocytized by macrophages) and show homogeneous uptake resulting in dark signal on T2-weighted images. In a node which is either partially or completely infiltrated by malignant cells, there is absence of functioning macrophages, leading to a lack of nanoparticle uptake resulting in focal or complete area of bright signal intensity on T2-weighted images. This technique is highly effective in identifying metastases in non-enlarged and partially replaced nodes; however, due to the negative-contrast nature of the detection, small lesions can be missed [13]. In one study, sensitivity and specificity of LNMRI was 76.5 % and 98.4 % in diagnosing nodal metastasis [14]. Lymphatic flow velocities can be assessed in lymphedema by visualization of lymphatic flow using principles of spin labeling MR imaging, and thus, lymphedema etiogenesis and therapies may be interrogated without exogenous contrast agents [15].