Characterizing Lower Extremity Lymphedema and Lipedema with Cutaneous Ultrasonography and an Objective Computer-Assisted Measurement of Dermal Echogenicity

Emily Iker, MD,1 Cory K Mayfield, BS,2 Daniel J Gould, MD,3 and Ketan M Patel, MD3. Lymphatic Research Biology 2019

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Characterizing Lower Extremity Lymphedema and Lipedema with Cutaneous Ultrasonography and an Objective Computer-Assisted Measurement of Dermal Echogenicity

Emily Iker, MD,1 Cory K Mayfield, BS,2 Daniel J Gould, MD,3 and Ketan M Patel, MD3. Lymphatic Research Biology 2019

Background: Sonographic findings differ in patients with primary lipedema from those with lymphedema. This project was designed to quantify those differences and objectively characterize findings of lipedema and lymphedema in the lower extremity.

Methods and Results: Patients with a clinical diagnosis of ISL stage I-II lipedema or lower extremity lymphedema that received ultrasound evaluation were included in this study. Thickness and echogenicity of the skin and subcutaneous fat layer were measured at the level of the ankle, calf, and thigh in each patient. The cohort analyzed included 12 patients with lipedema (12 lower extremities) and 10 patients with unilateral lymphedema (10 lower extremities with lymphedema and 8 lower extremities used as controls). Mean skin thickness of the ankle and calf was greatest in the lymphedema group compared to those with lipedema or controls (p<0.01 and p<0.01, respectively). The mean thickness of the subcutaneous fat layer of the thigh was greatest in those with lipedema (p<0.01). Mean dermal to subcutaneous fat echogenicity ratio was decreased in those with lymphedema (ankle, 0.91; calf, 1.05; thigh, 1.19) compared to lipedema (ankle, 1.36; calf, 1.58; thigh, 1.54) and control (ankle, 1.26; calf, 1.54; thigh, 1.56) (p<0.01, p<0.01, and p=0.02, respectively).

Conclusions: Lymphedema appears to be associated with increased skin thickness and dermal hypoechogenicity, particularly in the distal lower extremity, compared to lipedema or controls. Conversely, lipedema may be associated with increased thickness and hypoechogenicity of the subcutaneous fat. Overall, these findings suggest that ultrasound may be an effective tool to differentiate these diseases and potentially guide treatment.

Main findings

  • Echogenicity of the dermis and subcutaneous fat layers was determined by measuring the mean brightness of manually selected regions of interest designed to encompass the entire dermis or subcutaneous fat layer in each ultrasound image using image analysis software ImageJ
  • The mean skin thickness at both the ankle and calf was highest in the lymphedema group.
  • In the lymphedema group, the ankle thickness was measured at 0.249cm (range 0.18–0.4). Conversely, the lipedema and control groups measure 0.152cm (range 0.1–0.2) and 0.165cm (range 0.1– 0.2), respectively, at the ankle (p=0.001). At the level of the calf the mean skin thickness in the lymphedema group was 0.268cm (range 0.18–0.35), 0.145cm (range 0.1–0.2) in the lipedema group, and 0.155cm (range 0.1–0.2) in the control group (Fig. 3) (p=0.001). No significant difference was noted between the groups in skin thickness of the thigh.
  • Subcutaneous tissue thickness was higher in both the lymphedema and lipedema groups compared to controls at all levels.
  • In this study, lymphedema appeared to be associated with increased skin thickness and dermal hypoechogenicity, particularly in the distal lower extremity. Conversely, lipedema may be associated with increased thickness and hypoechogenicity of the subcutaneous fat throughout the lower limb. Importantly, these findings are consistent with the clinical nature of the diseases, and this represents a successful application of ultrasound technology for clinical differentiation of the disease.
  • cutaneous ultrasound can be used on patients who would otherwise be unable to undergo a CT or MRI due to obesity.
  • The authors believe this provides a valuable diagnostic tool for clinical analysis of lipedema and lymphedema and may be valuable in improving treatment.