Regional Patterns of Fluid and Fat Accumulation in Patients with Lower Extremity Lymphedema Using Magnetic Resonance Angiography

Background: Fat accumulation is frequently observed in patients with lymphedema but is not accounted for in existing staging systems. In addition, the specific regional patterns of fat and fluid accumulation remain unknown and might affect outcomes following medical or surgical intervention. The purpose of this study was to evaluate fluid and fat distribution in patients with lower extremity lymphedema using magnetic resonance angiography. Methods: Magnetic resonance angiographic examinations of patients with lower extremity lymphedema were reviewed. Fluid-fat grade and location were assessed by three observers. Three-point scales were developed to grade fluid (0 = no fluid, 1 = reticular pattern of fluid, and 2 = continuous stripe of subcutaneous fluid) and fat (0 = normal, 1 = subcutaneous thickness less than twice that of the unaffected side, and 2 = subcutaneous thickness greater than twice that of the unaffected side) accumulation. Results: In total, 76 magnetic resonance angiographic examinations were evaluated. Using the proposed grading system, there was good interobserver agreement for fat and fluid accumulation location (91.5 percent; kappa = 0.9), fluid accumulation grade (95.7 percent; kappa = 0.95), and fat accumulation grade (87.2 percent; kappa = 0.86). Patients with International Society of Lymphology stage 2 lymphedema had a wide range of fluid and fat grades (normal to severe). The most common location of fluid accumulation was the lateral lower leg, whereas the most common location of fat accumulation was the medial and lateral lower leg. Conclusion: The proposed magnetic resonance angiographic grading system may help stratify patients with International Society of Lymphology stage 2 lymphedema on the basis of tissue composition.