Abstract

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

Joseph H. Dayan, M.D. Itay Wiser, M.D., Ph.D. Richa Verma, M.D. Jody Shen, M.D. Nishi Talati, M.D. Debra Goldman, M.S. Babak J. Mehrara, M.D. Mark L. Smith, M.D. Erez Dayan, M.D. Michelle Coriddi, M.D. Alexander Kagan, M.D. Plast. Reconstr. Surg. 145: 555, 2020

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; κ = 0.9), fluid accumulation grade (95.7 percent; κ = 0.95), and fat accumulation grade (87.2 percent; κ = 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.

Main findings

• The most common location of fluid accumulation was the lower leg [59 of 76 (77.6 percent)]—in particular, the lateral lower leg [34 of 59 (57.6 percent)]. Twelve patients (15.8 percent) had fluid accumulation in the thigh, most commonly the lateral thigh [five of 12 (41.7 percent)]. Only five patients (6.6 percent) had fluid accumulation distributed equally in the lower leg and thigh.
• The findings in this study demonstrate that fat accumulation is a prominent feature of lymphedema and may be an important factor in patient assessment. Nearly 90 percent of patients had some degree of fat accumulation, and fat was the dominant component of excess limb volume in more than one-third of patients.
• the duration of lymphedema was not associated with either fluid or fat grade or International Society of Lymphology stage. The ability to draw conclusions from this may be limited by the distribution of lymphedema stages among the patients in this study. However, patients with a short duration of lymphedema and early disease stage had profound fat accumulation. For example, 25 percent of patients with a severe fat grade of 2 had lymphedema for less than 2 years.
• This counters the generalized notion that fluid is serially replaced by fat in a linear relationship over time. The lack of a time-dependent association with fat or fluid accumulation suggests that these patients do not all fall along the same spectrum of disease.
• These variable manifestations of fibrofatty accumulation likely reflect fundamental differences in immune pathophysiology among patients, with some forms of lymphedema that are more aggressive and proliferative than others.
• A limb with advanced fibrofatty proliferation may not respond well to decongestive therapy or physiologic procedures, such as vascularized lymph node transplantation and lymphaticovenous anastomosis. In these cases, liposuction, as advocated by Brorson, has been beneficial, provided that there is no significant pitting and the patient is 100 percent compliant with compression.