The value of the dermal rim sign on nonenhanced MRI for predicting dermal backflow in patients with primary lower extremity lymphedema

Purpose The dermal rim sign (DRS) on nonenhanced MRI has been shown to predict dermal backflow (DBF) in patients with secondary upper limb lymphedema. However, whether DRS has the same effects on primary lower extremity lymphedema (PLEL) has not been clearly reported. Therefore, this study aimed to explore whether the DRS can be used to diagnose the DBF on lymphoscintigraphy in patients with PLEL. Methods Ninety-four patients who were diagnosed with PLEL were recruited for this retrospective study from January 2022 to December 2023. According to the findings of the lymphoscintigraphy, all patients were divided into two groups: non-DBF and DBF. The MRI data of the two groups were recorded and statistically compared for the following indicators: range of lymphedema involvement (left, right, whole lower limbs, only thigh, only calf+ankle), signs of lymphedema (notable thickening of skin, parallel line sign, grid sign, honeycomb sign, band sign, lymph lake sign, crescent sign, dermal rim sign), and lymphedema (skin thickness, band width). The dermal rim sign is characterized by notable thickening of the skin+grid sign/honeycomb sign (one or both of which appear)+band sign. Results The following statistically significant differences in the following indicators were found between the two groups (P<0.05): notable skin thickening, parallel line sign, grid sign, honeycomb sign, band sign, dermal rim sign, skin thickness and band width. The sensitivity of predicting DBF with the DRS was 82%, the specificity was 64%, and the accuracy was 77%. Conclusion This study confirmed good consistency between the DRS and DBF from the perspective of imaging; this tool is suitable for children, adolescents, and patients with contraindications to lymphoscintigraphy. The DRS has important value in assessing the severity of PLEL. DRS is suggested for the clinical use of combined surgical treatment for PLEL.