Tissue Sodium Content is Elevated in the Skin and Subcutaneous Adipose Tissue in Women with Lipedema

Objective: To test the hypothesis that tissue sodium and adipose content are elevated in patients with lipedema; if confirmed, this could establish precedence for tissue sodium and adipose content representing a discriminatory biomarker for lipedema. Methods: Participants with lipedema (n = 10) and control (n = 11) volunteers matched for biological sex, age, BMI, and calf circumference were scanned with 3.0-T sodium and conventional proton magnetic resonance imaging (MRI). Standardized tissue sodium content was quantified in the calf skin, subcutaneous adipose tissue (SAT), and muscle. Dixon MRI was employed to quantify tissue fat and water volumes of the calf. Nonparametric statistical tests were applied to compare regional sodium content and fat-to-water volume between groups (significance: two-sided P <= 0.05). Results: Skin (P = 0.01) and SAT (P = 0.04) sodium content were elevated in lipedema (skin: 14.92.9 mmol/L; SAT: 11.9 +/- 3.1 mmol/L) relative to control participants (skin: 11.9 +/- 2.0 mmol/L; SAT: 9.4 +/- 1.6 mmol/L). Relative fat-to-water volume in the calf was elevated in lipedema (1.2 +/- 0.48 ratio) relative to control participants (0.63 +/- 0.26 ratio; P < 0.001). Skin sodium content was directly correlated with fat-to-water volume (Spearman's rho = 0.54; P = 0.01). Conclusions: Internal metrics of tissue sodium and adipose content are elevated in patients with lipedema, potentially providing objective imaging-based biomarkers for differentially diagnosing the under-recognized condition of lipedema from obesity.