Novel Ultrasound Technique for Assessing Fibrosis in Subcutaneous Fat in Lymphedematous Limbs

There is no standardized method for identifying fibrosis in the subcutaneous tissue of lymphedematous limbs. This study evaluated the relationship between ultrasonographic findings and fibrosis severity in patients with lower limb lymphedema.

A retrospective analysis included 92 sites in 40 limbs of 26 female patients undergoing lymphaticovenous anastomosis. Skin thickness and subcutaneous echogenicity were assessed preoperatively using an 18-MHz linear ultrasound probe and classified into four grades (U0-U3). Fibrosis severity was evaluated intraoperatively and classified into five grades (F0-F4). Receiver operating characteristic (ROC) curve analysis determined the diagnostic accuracy of skin thickness for predicting severe fibrosis (F3/F4), and a regression model was developed to predict fibrosis severity.

Skin thickness was significantly greater in the calves (2.7 mm) than in the thighs (2.1 mm, p < 0.01) and increased with lymphedema stage. Fibrosis severity was higher above the superficial fascia and more prevalent in calves (p < 0.01). ROC analysis showed an area under the curve of 0.80 for calf (above the superficial fascia), with a cutoff of 2.65 mm. The regression model (R² = 0.51, p < 0.001) demonstrated that skin thickness and fat echogenicity significantly predicted fibrosis severity: Fibrosis severity = 0.21 + 0.32 × skin thickness (mm) + 0.45 × fat echogenicity grade.

Ultrasound-based measurements of skin thickness and fat echogenicity are reliable and noninvasive predictors of fibrosis severity in patients with lymphedema. These findings support the use of ultrasound imaging to guide treatment planning and improve surgical outcomes. However, further validation is needed in diverse populations.