Doppler ultrasound-based noninvasive biomarkers in hidradenitis suppurativa: evaluation of analytical and clinical validity

Ultrasound monitoring of hidradenitis suppurativa fistulas in treatment with adalimumab

Recently, ultrasound has become a significant tool in studying hidradenitis suppurativa (HS), allowing differentiation between abscesses and fistulas, and assessing various disease features. However, there is still a lack of data on using ultrasound (US) to assess treatment response to medical treatment. The study aims to assess the clinical usefulness of ultrasound in monitoring disease activity in HS patients undergoing treatment with adalimumab over a 52-week period. This research employs a retrospective approach to analyze ultrasound scores related to fibrosis, edema, power-Doppler (PD) signal, and resistive index (RI) at baseline and after 52 weeks of adalimumab treatment. In total, 311 fistulas from 69 patients were included. Multivariate regression analysis showed that PD score and edema were related to IHS4-55 and variations of DLQI and pain-VAS. Furthermore, at baseline, healed and non-healed fistulas were characterized by significant differences in PD signal, fibrosis, edema, and RI. Limitations include the retrospective design of the study, a limited population size, and the absence of a control group. However, our data provide evidence that ultrasound can be a reliable tool for assessing patients' responses to medical therapies.

Hidradenitis suppurativa, from basic science to surgery and a new era of tailored targeted therapy: An expert opinion paper

Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterised by an aberrant activation of innate immunity and increased production of pro-inflammatory mediators such as interleukin 17 (IL-17). IL-17 has been shown to play a key role in the pathogenesis of HS and evidence highlights the potential of IL-17-targeted therapies. The fully human IgG/κ monoclonal antibody secukinumab, which specifically targets IL-17A and inhibits interaction with its receptor, has recently been approved for the treatment of moderate-to-severe HS. Secukinumab offers patients an efficacious and well-tolerated treatment option in terms of sustained response by rapidly improving signs and symptoms, and preventing disease progression in the absence of loss of response. Being a challenging disease, HS is associated with a delay to diagnosis of 3-10 years and, consequently, late implementation of appropriate treatment, leading to disease progression. Misdiagnosis due to flawed understanding and lack of awareness among medical providers and patients is considered an important factor contributing to the delayed diagnosis. Thus, serious efforts must be made on a large scale to urgently reduce the delay in HS diagnosis and reduce the disease burden in patients, including raising awareness, implementation of education programmes at medical and specialisation schools, as well as continuous education of healthcare providers at different levels for the early detection of HS and initiation of appropriate treatment. Here, we present the main critical unmet needs in the diagnosis and treatment of patients affected by HS, address how disease awareness and comprehensive multidisciplinary management (offering both medical and surgical care) can benefit patients, and suggest therapeutic options, based on clinical characterisation and early identification and intervention (window of opportunity), to be adopted for a timely and better management of disease progression and to fill current gaps.

Advanced Doppler Ultrasound Insights: A Multicenter Prospective Study on Healthy Skin

Background: There have been multiple studies on the use of Doppler ultrasound to define skin inflammation, but the visible vessels of healthy skin have yet to be described. Objective: This study aimed to evaluate the visible vessels of healthy skin using Doppler ultrasound. Methods: Prospective multicenter study using Doppler ultrasound to analyze healthy skin. The color percentage, flow velocity, and maximum vessel diameter were calculated. Results: 943 images from 152 patients were recorded. The most frequently used mode was color Doppler (40.6%), followed by power Doppler (30.4%). Visible vessels were detected in 18.23%; in positive Doppler images, color occupied less than 5%. The malar region exhibited the highest visible vessels. The 22 MHz probe detected smaller vessels with slower flows than the 18 MHz probe. Spectral Doppler showed peak systolic values of less than 10 cm/s and a vessel diameter of less than 1 mm. In most of the participating centers, the operators had less than 10 years of experience in performing skin ultrasound examinations. Sensitivity of the Doppler may vary according to the device. Conclusions: With the used ultrasound equipment, it was uncommon to visualize vessels in healthy skin. When seen, they covered less than 5% of the image with low flow and small size.

Update on the role of color Doppler ultrasound in hidradenitis suppurativa: a game-changer

Hidradenitis suppurativa has greatly benefited from the insights of color Doppler ultrasound. Thus, ultrasonography has helped prove the follicular link of this disease and has ruled out the primary involvement of the apocrine glands, which, in the old days, was supposedly the cause of the disease. Importantly, ultrasound can detect subclinical anatomical information in HS that cannot be deducted from the clinical examination. Moreover, high-frequency (≥15 MHz) and ultra-high-frequency (≥50 MHz) ultrasound present a much higher axial spatial resolution compared to magnetic resonance imaging. Ultrasound allows us to detect better subclinical cutaneous anatomical abnormalities and, therefore, arrive earlier and more accurately at diagnosis and staging. Ultrasonographic diagnostic criteria can discriminate HS from other clinical simulators, which is also critical in diagnosing mild and moderate stages and is relevant for the severe stages. This imaging technique supports the severity (mSOS-HS) and activity (US-HSA) scorings more accurately, which can help assess the actual stage of the disease. This is important to decide the type of treatment and to perform a more objective follow-up of the patients. Magnetic resonance imaging has been reported as helpful in diagnosing deep perianal tunnels; however, it presents a lower axial spatial resolution compared with high and ultra-high frequency ultrasound. Nowadays, there is solid evidence of the usefulness of ultrasound in HS, which implies that it is a game-changer and should be recommended as the first-choice imaging technique and a standard of care tool for HS patients.

Doppler ultrasound protocol for patients with hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory disease that leads to the formation of nodules, abscesses and fistulas, with the formation of scars and fibrosis, causing significant impairment in patient quality of life. The diagnosis is clinical, using scores to classify the severity of the condition; currently the most recommended classification is the International Hidradenitis Suppurativa Severity Scoring System (IHS4). Doppler ultrasound has been used to complement the clinical evaluation of patients with HS. It is possible to observe subclinical lesions that change the staging, the severity of the case, and its treatment, either clinical or surgical. Correct treatment is essential to minimize the consequences of this disease for the patient.

OBJECTIVE

To establish an outpatient protocol for the use of Doppler ultrasound in the care of patients with HS.

METHODS

A narrative review of the literature was carried out on the use of Doppler ultrasound in patients with hidradenitis suppurativa; a referring protocol and technique orientations for imaging assessment in HS were created.

RESULTS

Recommendation to perform ultrasound evaluation of symptomatic areas eight weeks after using antibiotics and four, 12, and 24 weeks after starting immunobiologicals; apply SOS-HS ultrasound severity classification.

STUDY LIMITATIONS

The review did not cover all literature on ultrasound and HS; no systematic review was carried out, but rather a narrative one.

CONCLUSIONS

The correct assessment of patients staging must be carried out using dermatological ultrasound to avoid progression to scars and fibrosis, which compromise patients quality of life.

Eosinophils in hidradenitis suppurativa patients exhibit pro-inflammatory traits, implicating a potential pathogenic role in the disease

Hidradenitis suppurativa (HS) is an inflammatory skin disease characterized by painful nodules, abscesses and purulent secretions in intertriginous regions. Intense pruritus frequently accompanies HS lesions, adding further discomfort for patients. While Th17 pathway activation is implicated in HS pathogenesis, disease mechanisms are still not fully understood, and therapeutics are lacking. Previous reports raise a potential role for eosinophils in HS, showing a strong association of eosinophil levels with disease severity. To investigate eosinophils in HS, we recruited patients and matched healthy controls and then performed flow-cytometry studies, eosinophil stimulation assays, and lesional skin staining for eosinophils. We found that HS patients reported similar levels of pain and itch. Compared to matched controls, HS blood exhibited decreased mature eosinophils and increased numbers of immature eosinophils, coupled with a significant increase in dermal eosinophilic infiltrates. Additionally, IL-17RA+ eosinophils were highly and significantly correlated with multiple HS-related clinical scores. In both stimulated and unstimulated conditions, HS eosinophils showed an inflammatory phenotype versus controls, including an increase in costimulatory T- and B-cell markers (e.g. CD5 and CD40) following all stimulations (TNFα/IL-17A/IL-17F). These findings highlight the significance of pruritus in HS and suggest a higher turnover of eosinophils in HS blood, potentially due to the consumption of eosinophils in skin lesions. Our data delineate the features and functions of eosinophils in HS and suggest that eosinophils participate in disease pathogenesis, advancing Th17-related inflammation. Further studies are needed to investigate eosinophils' response to current HS treatments and their potential as a therapeutic target in the disease.

Role of Color Doppler Ultrasound in Cutaneous Inflammatory Conditions

Inflammatory cutaneous diseases can be challenging to diagnose and manage. Nowadays, the anatomical information provided by ultrasound is critical for detecting subclinical alterations and assessing the severity and activity of these conditions. Many of these entities can be clinically observed in dermatology and other specialties, such as rheumatology, plastic surgery, ophthalmology, and otolaryngology, among others. We review the ultrasonographic patterns of the most common inflammatory cutaneous conditions. In several cases, such as hidradenitis suppurativa, acne, and morphea, there are ultrasonographic staging systems of severity or activity that are pivotal in the management of these diseases. The early ultrasonographic diagnosis of these entities implies a proper management of the patients and, therefore, improve their quality of life. Thus, knowledge of the current use of ultrasound in this field seems essential.

How to Start on Dermatologic Ultrasound: Basic Anatomical Concepts, Guidelines, Technical Considerations, and Best Tips

Dermatologic ultrasound has grown exponentially during the last decades and has passed from the experimental phase to the routine daily practice in multiple countries. The performance of this imaging technique requires color Doppler ultrasound devices working with high-frequency probes, a trained operator on imaging and dermatologic conditions, and the performance of standardized protocols for obtaining the anatomical data properly. In this review, we analyze the ultrasonographic anatomy of the skin, hair, and nails, the technical requirements and considerations, the guidelines, and the recommended protocols, and provide the best tips for practicing this type of examination confidently.

Update on Ultrasound Diagnostic Criteria and New Ultrasound Severity and Activity Scorings of Hidradenitis Suppurativa: Modified SOS-HS and US-HSA

Hidradenitis suppurativa (HS) is a devasting autoimmune cutaneous disease that affects the hair follicles and can clinically present palpable nodules, abscesses, and tunnels (fistulas), usually in the intertriginous regions. It has been widely reported that color Doppler ultrasound can detect subclinical abnormalities and stage the severity of the disease more accurately. Nevertheless, the ultrasound diagnostic criteria were reported with 15 MHz 10 years ago, and now it is possible to detect early anatomical abnormalities in HS using 70 MHz. Thus, an update of the ultrasonographic diagnostic criteria is needed. The most widely used sonographic staging of severity of HS (SOS-HS) includes the number of affected regions, besides counting the number of key lesions like pseudocysts, fluid collections, and tunnels; however, the total number of affected regions may fit better in an activity scoring. Furthermore, a high number of tunnels or communicated tunnels can complicate the management and may indicate an even more urgent treatment, which should be considered in the severity classification. To date, no hidradenitis scoring of activity has been reported in the literature, making it difficult to track the degree of inflammation under treatment objectively. Therefore, two new scorings are proposed. The first is an updated sonographic scoring of severity called modified SOS-HS (mSOS-HS), and the second is an activity ultrasound scoring of HS called US-HSA. Both staging systems can provide better anatomical information for discriminating the categories and, therefore, selecting more appropriate treatments and supporting research and clinical trials by giving more objective anatomical tools in real-world settings.

The role of imaging technologies in the diagnosis of hidradenitis suppurativa

Hidradenitis suppurativa is a chronic, inflammatory, recurrent, and debilitating disease of the hair follicle. It presents with painful, deep-seated, inflamed lesions, such as nodules, abscesses, sinus tracts, and fistulas, generally located in the main folds. Clinical severity assessment alone can be reductive; noninvasive skin imaging technologies, such as ultrasound, magnetic resonance imaging, medical infrared thermography, computed tomography, and positron emission tomography, provide subclinical anatomical and functional details. These instrumental techniques confirm the clinical suspect, thus allowing an earlier diagnosis and improving patients' clinical evaluation, staging, and management. Finally, they might be helpful for preoperative mapping. In this contribution, we provide an overview of the current knowledge about noninvasive skin imaging techniques with a particular focus on ultrasonography, which is widely used thanks to its precision, versatility, and availability.

Key Points to Select a Device for Dermatologic Ultrasound

What points to consider when selecting a device for practicing dermatologic ultrasound is an excellent question. After we met the requisites published in the guidelines for practicing dermatologic ultrasound, it is necessary to consider the main objective of the use because it is not the same to be focused mostly on the avoidance of the puncture of important facial vessels such as the case of injectors of cosmetic fillers in comparison to the use of operators that need to deal with the diagnosis and monitoring of a wide range of dermatologic pathologies. Currently, a broad variety of ultrasound devices meets the minimum requirements for practicing these examinations in the market. Thus, small, portable, and high-end devices may present advantages and limitations that must be balanced according to the primary purposes and the budget. Moreover, the shape and footprint of the probes can make difficult or facilitate a dermatologic procedure. Other points to consider are the type of storage and the need for technical service. In summary, there are key points that we need to consider when we select a dermatologic ultrasound device in dermatology or aesthetics.

Ultrasound imaging of the axilla

Axilla is a pyramidal-in-shape "virtual cavity" housing multiple anatomical structures and connecting the upper limb with the trunk. To the best of our knowledge, in the pertinent literature, a detailed sonographic protocol to comprehensively assess the axillary region in daily practice is lacking. In this sense, the authors have briefly described the anatomical architecture of the axilla-also using cadaveric specimens-to propose a layer-by-layer sonographic approach to this challenging district. The most common sonographic pathological findings-for each and every anatomical compartment of the axilla-have been accurately reported and compared with the corresponding histopathological features. This ultrasound approach could be considered a ready-to-use educational guidance for the assessment of the axillary region. CRITICAL RELEVANCE STATEMENT: Axilla is a pyramidal-in-shape "virtual cavity" housing multiple anatomical structures and connecting the upper limb with the trunk. The aim of this review article was to describe the anatomical architecture of the axilla, also using cadaveric specimens, in order to propose a layer-by-layer sonographic approach to this challenging district.

New Insight into the Molecular Pathomechanism and Immunomodulatory Treatments of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is an immune-mediated inflammatory disorder characterized by deep-seated nodules, abscesses, sinus tracts and scars localized in the intertriginous areas. It is accompanied by pain, malodourous secretion and a dramatically decreased quality of life. Although the pathogenesis has not been entirely elucidated, the primary event is follicular hyperkeratosis of the pilosebaceous apocrine unit. Since the registration of the tumor necrosis factor-alpha inhibitor Adalimumab in 2015, several cytokines have been implicated in the pathomechanism of HS and the research of novel therapeutic targets has been intensified. We provide an update on the inflammatory cytokines with a central role in HS pathogenesis and the most promising target molecules of future HS management.

How Adalimumab Impacts Antibiotic Prescriptions in Patients Affected by Hidradenitis Suppurativa: A 1-Year Prospective Study and Retrospective Analysis

We conducted a one-year prospective study involving the enrollment of 58 patients with Hidradenitis Suppurativa. Through a retrospective analysis of data on the same patients, with reference to the year prior to the initiation of the anti-TNFα drug adalimumab, we aimed to show how the advent of this biologic therapy changes the number of days of antibiotic therapy, the number of flare-ups per year, and their duration in days, as well as the quality of life and perceived pain of patients.

Ultra-high frequency ultrasound detection of the dermo-epidermal junction: Its potential role in dermatology

Traditional high-frequency ultrasound (HFUS; 20 MHz) is a non-invasive method used to study skin in vivo but is not able to measure skin thickness accurately and to identify the dermal-epidermal junction (DEJ). Ultra-high frequency ultrasound (UHFUS; 70-100 MHz) has sub-millimetre resolution comparable to histology. The aim of this study was to identify, by UHFUS, the DEJ and to describe skin differences in healthy individuals by providing a measure of skin thickness, based on age and gender. We also described the bullous pemphigoid lesion. We enrolled 42 patients divided into 2 groups: A and B. Group A included 32 healthy volunteers aged 22-74 years. Group B consisted of 10 patients with bullous pemphigoid. For each patient in group A, 8 ultrasound (US) clips by 70 MHz probe were performed at forehead, cheek, nose, forearm, abdomen, chest, back and leg. For each patient in group B, 5 US images were acquired at blisters roofs and edges. In each US image, we measured thickness of stratum corneum (α-β), epidermis (α-γ) and epidermis plus dermis (α-δ). In both groups, we found the presence of 4 lines delimiting: the stratum corneum (the layer between α-line and β-line), the epidermis (distance between α- and γ-line), and the boundary between dermis and subcutis (δ-line). The γ-line corresponds to the point of detachment of the bullae. The abdominal α-β layer was thicker in males (p = 0.019) and α-δ thickness at cheeks (p < 0.001), chest (p = 0.007), back (p = 0.025) and forearm (p < 0.001). In females, α-γ thickness of the back was greater (p = 0.005). In old people compared to young, we noticed an increase of α-β layer at forehead and chest (p = 0.014), an increase of α-γ layer at forearm (p = 0.001), back (p = 0.024) and leg (p = 0.010) and an increase of α-δ layer at forehead (p = 0.001) and nose (p = 0.049). UHFUS is an advanced imaging technique that can detect both the DEJ and the boundary between dermis and subcutaneous tissue so that epidermal and dermal thickness can be measured with good accuracy. Regarding gender and age, skin differences obtained with UHFUS were comparable to other non-invasive methods.

The inflammatory proteome of hidradenitis suppurativa skin is more expansive than that of psoriasis vulgaris

BACKGROUND

Although hidradenitis suppurativa (HS) shares some transcriptomic and cellular infiltrate features with psoriasis, their skin proteome remains unknown.

OBJECTIVE

To define and compare inflammatory protein biomarkers of HS and psoriasis skin.

METHODS

We assessed 92 inflammatory biomarkers in HS (n = 13), psoriasis (n = 11), and control skin (n = 11) using Olink high-throughput proteomics. We also correlated HS skin and blood biomarkers using proteomics and RNA sequencing.

RESULTS

We identified 57 differentially expressed proteins (DEPs) in lesional psoriasis and 64 DEPs in lesional HS skin, compared to healthy controls. Both HS and psoriasis lesional skin demonstrated a significant upregulation of T helper 1 and T helper 17 proteins. Healthy-appearing perilesional HS skin had 63 DEPs compared to healthy controls. Nonlesional HS and psoriasis skin had 24 and 7 DEPs, respectively, compared to healthy controls. Tumor necrosis factor and 8 other proteins were significantly correlated with clinical severity in perilesional HS skin (2 cm from a nodule).

LIMITATIONS

Inclusion of only moderate-to-severe patients and the cohort size.

CONCLUSION

HS has a greater inflammatory profile and is more diffusely distributed compared with psoriasis. Proteins correlated with disease severity are potential disease mediators. Perilesional skin is comparably inflamed to lesional skin, suggesting the need to treat beyond skin nodules.

Epithelialized tunnels are a source of inflammation in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic, painful, and burdensome inflammatory disease manifesting in nodules and abscesses, with progression to chronically draining tunnels in later-stage disease.

OBJECTIVE

We sought to determine whether HS tunnels are immunologically active participants in disease activity.

METHODS

Skin biopsy specimens were obtained by using ultrasound guidance in untreated patients with HS and those enrolled in an open-label study of brodalumab (ClinicalTrials.gov identifier NCT03960268) for patients with moderate-to-severe HS.

RESULTS

Immunohistochemistry of HS biopsy specimens demonstrated that the epithelialized HS tunnels recapitulate the psoriasiform epidermal hyperplasia morphology of the overlying epidermis, displaying molecular inflammation, including S100A7 (psoriasin) positivity, as well as features of epidermal skin, including loricrin, filaggrin, lipocalin-2, and Melan-A positive cells. Tunnels were associated with increased infiltration of T cells, dendritic cells, and neutrophils; formation of neutrophil extracellular traps, and increased expression of psoriasiform proinflammatory cytokines. Unsupervised hierarchical clustering demonstrated a separation of HS samples based on the presence or absence of tunnels. Tunnels isolated by microdissection had higher levels of epithelium-derived inflammatory cytokines compared with the overlying epidermis and healthy controls. Clinically, the size and draining of the tunnels were decreased with treatment with the IL-17RA antagonist brodalumab.

CONCLUSION

These data suggest that tunnels are a source of inflammation in HS.

Ultrasound-guided de-roofing of epithelialised tunnels of hidradenitis suppurativa

Hidradenitis Suppurativa is a chronic inflammatory disease manifesting in painful nodules, abscesses and malodorous draining tunnels with a pre-disposition to flexural regions of skin. Traditional surgical interventions include excision of clinically visible lesions and in severe cases - excision down to fascia of entire anatomical regions (axilla, groin) and repair with split-thickness grafting or skin substitutes. However, such techniques are plagued by long healing times (up to several months), extensive tissue loss and high recurrence rates given that a large proportion of disease is not clinically visible. Deroofing is a tissue-saving surgical technique, ideal for Hurley Stage 2 disease, which when combined with bedside pre-operative sonography can allow for the accurate identification and removal of occult dermal tunnels whilst minimising the risks of pain, infection, minimising healing times and can be safely conducted in the setting of immunomodulatory therapy.

High-frequency ultrasound as a scientific tool for skin imaging analysis

Ultrasonic imaging is one of the most important diagnostic tools in clinical medicine due to its cost, availability and good correlation with pathological results. High-frequency ultrasound (HFUS) is a technique used in skin science that has been little explored, especially in comparison with other sites and imaging techniques. HFUS shows real-time images of the skin layers, appendages and skin lesions in vivo and can significantly contribute to advances in skin science. This review summarizes the potential applications of HFUS in dermatology and cosmetology, with a focus on quantitative tools that can be used to assess various skin conditions. Our findings showed that HFUS imaging is a reproducible and powerful tool for the diagnosis, clinical management and therapy monitoring of skin conditions. It is also a helpful tool for assessing the performance of dermatological products. This technique may eventually become essential for evaluating the performance of dermatological and cosmetic products.

Real-Time Confocal Imaging for Hidradenitis Suppurativa: Description of Morphological Aspects and Focus on the Role of Follicular Ostia

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic, recurrent, inflammatory skin disease involving the follicular unit. Growing evidence suggests a crucial role of hyperkeratosis, infundibular plugging and perifolliculitis in its pathogenesis.

OBJECTIVES

To characterize the microscopic morphology of open comedos using in vivo reflectance confocal microscopy (RCM) and define alterations occurring in HS normal-appearing perilesional skin compared to healthy skin of a control group, discussing therefore microscopic differences.

MATERIALS AND METHODS

Twenty patients (11 males, 9 females; aged 19-51 years) affected by HS were recruited. RCM was performed on open comedos of axillary/inguinal regions and on normal-appearing skin areas distant at least 1.5 cm from HS lesions. Ten healthy individuals (6 males, 4 females) were included as control group.

RESULTS

RCM aspects of 78 open comedos were explored, observing circular/ovoidal structures disclosing a hyperrefractive amorphous material (72/78, 92.3%) within the infundibular cavity surrounded with a bright (51/78, 65.4%) and regular (52/78, 66.2%) border. Follicular ostia of HS perilesional skin (n = 541) compared to follicular ostia of a control group (n = 321) were characterized by a larger infundibular diameter (183.4 vs. 85.8 µm) and diverged in terms of material collected inside infundibula (44.5 vs. 21%) and keratinization of the border (47.6 vs. 25.5%).

CONCLUSION

In vivo characterization of open comedos and the recognition of microscopic subclinical alterations of HS normal-appearing skin, compared to healthy skin, could add further insights into the definition of biological events leading to HS manifestations, including the dysregulated process of keratinization.

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.