Clinical value of MRI in central lymphatic vessel evaluation and grading in primary lower-extremity lymphedema

<b>Introduction:</b> The manifestations of the central lymphatic vessels in primary lower-extremity lymphedema (LEL) remain incompletely understood. Advanced magnetic resonance imaging (MRI) techniques offer the potential to noninvasively evaluate central lymphatic vessels and their relationship with disease severity. Our objective was to investigate the differences in imaging performance of central lymphatics and inguinal lymph nodes in primary LEL of different clinical stages, and to assess the ability of MRI to grade primary LEL. <b>Methods:</b> Patients were staged according to the International Society of Lymphology (ISL), with 92 cases in stage I, 134 in stage II, and 53 in stage III. All patients underwent lower-extremity MRI, pelvic MRI, and magnetic resonance thoracic ductography (MRTD). Chi-squared tests and Fisher's exact tests were used to compare the relationship between the central lymphatic vessels and inguinal lymph nodes with clinical staging. LEL was graded based on MRI images, and a partial correlation coefficient was employed to assess the correlation between MRI grading and clinical staging. <b>Results:</b> A significant correlation was observed between clinical staging and MRI grading (<i>R</i> = 0.728, <i>p</i> < 0.001). The incidence of abnormalities in the terminal thoracic duct and the lumbar and iliac lymphatic vessels differed significantly across clinical stages (<i>p</i> ⩽ 0.001). Additionally, the frequency of enlarged inguinal lymph nodes on both the affected and the unaffected sides showed statistically significant differences (<i>p</i> = 0.001). <b>Conclusion:</b> MRI grading demonstrates a high correlation with clinical staging. Changes in central lymphatic vessels and inguinal lymph nodes, as identified through MRTD, provide valuable insights for the clinical staging of primary LEL.