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

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.