Hidradenitis suppurativa (HS) is a chronic, immune-mediated inflammatory disease of the hair follicle that causes the formation of nodules, abscesses and fistulas, mainly in the axillary, inguinal and anogenital regions, with the formation of bridging scars and fibrosis.1, 2, 3, 4 It is a recurrent and debilitating disease, that presents after puberty, leading to significant quality of life impairment by causing pain, pruritus, odor, and local burning sensation. It is the dermatological disease with the greatest psychosocial impact and highest Dermatology Life Quality Index (DLQI).1, 5, 6
To guide decisions regarding the treatment of HS, the clinical classification of subtypes is relevant, in addition to determining severity.2, 4 The patient approach involves both the management of worsening factors and treatment with medications and surgical procedures to remove fistulas and scars that act as recurrent inflammation sites. Thus, greater staging accuracy potentially impacts the therapeutic decision regarding the implementation of appropriate treatment proportional to the severity.5
Doppler ultrasound with a high-frequency transducer (above 15 MHz) has been used to characterize the type of lesion and its depth with greater precision,2, 5, 7, 8, 9 since the clinical palpation of lesions may not be accurate when differentiating nodules, abscesses and fistulas, especially when there is intense edema. This is essential for the evaluation and management of patients with HS.8, 10, 11
Compared to isolated clinical assessment, the use of ultrasound classifies a significant percentage of patients into more advanced stages, changing the therapeutic planning.2, 8, 11, 12 Its use changed the treatment in 82% of the assessed patients; in particular, medical treatment was changed to surgical in 24% of the cases.11
The main ultrasound findings in hidradenitis suppurativa are dilation of hair follicles, dermal changes, pseudocysts, fluid collections and fistulas. It has been proposed that the presence of three or more of these findings establishes the diagnosis of HS ‒ SOS-HS three-point score ‒ Sonographic Scoring of Hidradenitis Suppurativa.11 More recently it was also defined that there are five lesions observed in HS in the US: pseudocysts, collections, fistulas, fistulas and hair fragments (called hair tracts).13 Doppler ultrasound can also be used to identify subclinical fistulas and characterize inflammatory activity; it was established that there is an important correlation between the symptoms described by patients and ultrasound findings.6, 12, 14 A study showed that 76% of the assessed patients had fluid collections, 71% had pseudocysts and 29% had fistulas, all of which were not diagnosed on clinical examination.11
It is also possible to monitor the response to treatment non-invasively through vascularization assessment using Doppler10 and carry out better pre-operative planning for lesions that require surgical treatment. Moreover, there was a high correlation between ultrasound and histopathological findings. There is a relationship between Doppler intensity and neutrophilic infiltration; and good correlation between fistula diameter in ultrasound and histopathological evaluations.15 Similarly to the Hurley score, the SOS-HS was created using subclinical lesions, and shows a better correspondence with patient severity.14 Thus, ultrasound has shown to be an essential tool for greater accuracy in assessing the severity and extent of HS lesions, potentially impacting therapeutic decisions, allowing early and effective treatment to prevent complications, and the need for more invasive treatment. Therefore, the implementation of a Doppler ultrasound evaluation protocol as part of patients physical examination is necessary.