Hidradenitis Suppurativa: MRI Features in Anogenital Disease

BACKGROUND: Hidradenitis suppurativa is a rare chronic inflammatory disorder of apocrine gland-bearing skin, which commonly affects the anogenital region. There has been very little literature to date on the MRI appearances of anogenital hidradenitis suppurativa. OBJECTIVE: The aim of this study was to assess the MRI features of anogenital hidradenitis suppurativa in the largest cohort of patients to be published to date. DESIGN: After an institutional review board waiver, patients with hidradenitis suppurativa who were undergoing MRI for anogenital disease between 2005 and 2012 were identified from our institutional database. The MRI appearances were recorded by 2 radiologists in consensus, blinded to clinical details. Location of disease, number of tracts, presence of anal fistula, and supralevator involvement were recorded. Patient demographics were also noted. SETTINGS: This study was conducted at the Department of Radiology, Guy's and St Thomas' National Health Service Foundation Trust. PATIENTS: Patients included were those undergoing MRI for anogenital disease in hidradenitis suppurativa between 2005 and 2012. MAIN OUTCOME MEASURES: The distribution of sinus tracts in anogenital hidradenitis suppurativa on MRI was measured. RESULTS: Thirty-one MRIs were performed in 18 patients (15 men; mean age, 46 years). On the baseline MRI, multiple tracts were seen in the natal cleft (16/18; 83%), the perianal (12/18; 61%), the perineal (13/18; 56%), and the gluteal (8/18; 44%) regions. A communication with the anal canal was present in only 4 patients. Three patients had supralevator extension. Seven patients had follow-up MRIs with variable response to interval treatment: 3 of 7 showed responding disease, 3 of 7 showed stable disease, and 1 of 7 showed progressive disease. LIMITATIONS: This study was limited by its relatively small cohort of patients. CONCLUSIONS: In hidradenitis suppurativa, anogenital disease is usually subcutaneous but extensive, with only a minority of patients demonstrating deeper involvement. MRI may help define the extent of anogenital disease and assess response to treatment.