Clinical and Power-Doppler ultrasound features related with persistence of fistulous tracts under treatment with adalimumab in hidradenitis suppurativa: 4 years of follow-up

Fistulous tracts are the hallmark lesions of hidradenitis suppurativa (HS) and respond poorly to the currently available medical treatments. To evaluate the clinical and ultrasound features related with both healing and persistence of fistulous tracts in patients under treatment with adalimumab, a retrospective analysis of power-Doppler ultrasound (PD-US) images with fistulas in HS patients was performed. The clinical and sonographic staging of HS, body areas involved, and anatomic characteristics of the fistulous tracts were registered and graded. Chi-square test, univariate/multivariate Cox-regression analysis with clustered error, and Kaplan-Meier analysis were computed to analyze data. In total, 151 fistulous tracts from 33 HS patients were included. Age, BMI, length, thickness, subcutaneous pattern, high intensity of PD-US signal, and a high grade of fibrosis/edema were all related to a lower possibility of healing and a high risk of longer persistence at binomial Cox-regressions. Whereas, multivariate regressions showed that high fibrosis, was the variable with the highest risk of poor response and longer survival. Survival-analysis showed that fistulas with high fibrosis or PD-US signal have longer survival time than those with absent/low fibrosis or signal. Limitations include the impossibility to detect with ultrasound lesions less than 0.1 mm and smaller sample size. In conclusion, an accurate assessment of fibrosis may be crucial to define better when a surgical approach-besides the medical treatment-could be required. PD-US may assess the decrease of vascularization in HS lesions and consequently the reduction of inflammation due to immunomodulatory therapies.