Background Lipoedema is an accumulation of fat abnormally distributed in the lower limbs, and lymphoedema is oedema caused by a deficiency of the lymphatic system. High-resolution ultrasound operating at 20 MHz makes it possible to characterize dermal oedema.
Objectives The purpose of our study was to demonstrate that high-resolution ultrasound imaging of the skin can differentiate lipoedema from lymphoedema.
Methods Sixteen patients with lymphoedema (22 legs), eight patients with lipoedema (16 legs) and eight controls (16 legs) were included. Patients with lipolymphoedema were excluded. Ultrasound examinations were carried out with a real-time high-resolution ultrasound device on three different sites for each lower limb. The images were then anonymized and examined by an independent dermatologist who was blind to the clinical diagnosis. A new series of images was examined by three dermatologists to check interobserver agreement.
Results A significant difference in dermal thickness was observed between patients with lymphoedema and those with lipoedema and between patients with lymphoedema and controls. No significant difference in dermal thickness was shown between patients with lipoedema and controls at the thigh or ankle. Dermal hypo-echogenicity was found in at least one of the three sites in 100% of patients with lymphoedema, 12·5% of cases with lipoedema and 6·25% of the controls. Hypoechogenicity affected the entire dermis in all cases of lymphoedema except one. In cases of lipoedema and controls, hypoechogenicity was localized at the ankle and prevailed in the upper dermis. The expert correctly diagnosed all lower limbs with lymphoedema. No cases of lipoedema were diagnosed as lymphoedema. Exact interobserver agreement was excellent (0·98).
Conclusions High-resolution cutaneous ultrasonography makes it possible to differentiate lymphoedema from lipoedema. Obtaining a reliable diagnosis through high-resolution cutaneous ultrasonography might be valuable for improving the treatment of lipoedema and lymphoedema.