Severe Perineal Hidradenitis Suppurativa and Fistulas: An Underrated Association?

Background: Due to its multiple forms of presentation, hidradenitis suppurativa has classically imposed a diagnostic challenge. The prevalence of perianal fistula in patients with hidradenitis suppurativa ranges from 6.6% to 67%. The aim of the study was to assess both conditions. Methods: A retrospective chart review of the years 2000 to 2018 was conducted for patients with hidradenitis suppurativa using the ICD-9-CM code 705.83. Hurley’s three-stage classification was applied. Diagnosis and relevant patient characteristics were assessed, along with the presence of associated perianal fistula. Endoanal ultrasound (EAU) had been performed in 61% of the patients with perianal hidradenitis and perianal fistula, whereas magnetic resonance imaging (MRI) had been done for 19%. Results: Of 143 cases with hidradenitis, a perianal (perineal/buttocks) presentation occurred in 62 (43.4%) of patients, among whom 93.5% were men. Twenty-one percent were associated with perianal fistulas, six being complex ones associated with Hurley stage II and III. Treatment for the latter included: loose setons in four patients with Crohn’s disease and two non-Crohn’s disease with complex fistulas; four fistulotomies and two fistulectomies in low transsphincteric fistulas; and one incision and drainage. Conclusion: Perianal fistula should be treated according to associated diseases and the type of fistula. Association of hidradenitis and perianal fistulas may be higher than expected and the relation of severe hidradenitis with complex perianal fistulas should be studied further. Endoanal ultrasound and MRI may be useful tools to assess HS with complex perianal fistulas, but the iconographic patterns of hidradenitis and Crohn’s disease should be kept in mind as an association may prevail.