Anoperineal disease in Hidradenitis Suppurativa : MR imaging distinction from perianal Crohn’s disease

Abstract

• Spectrum of MRI features of HS-related anoperineal disease is wide. • Specific diagnosis of HS-related anoperineal disease is possible using MR imaging. • A combination of three MR signs allows distinction between HS and CD.

MRI anatomy and pathology of the anal canal

“…The perineum is the most common area affected in males, and the axillae in females . Anogenital HS occurs in a third of patients and is associated with a worse outcome . If untreated, HS can progress to sepsis, and longstanding cases may lead to malignant transformation to squamous cell carcinoma .…”

“…The etiology appears to be multifactorial, which includes altered immune response, environmental factors, genetic predisposition, and a strong association with smoking, obesity, and androgen excess . Some studies have shown an association with Crohn's disease . The pathogenesis involves occlusion of abnormal hair follicular ducts, which result in obstruction, stasis, and dilatation of the apocrine glands .…”

“…The main differential diagnosis for HS is perianal fistulas associated with Crohn's disease: the two conditions may have overlapping imaging features, and at times may coexist . Monnier et al showed that the fistulas in Crohn's disease are more complex and predominantly in the perianal region, with a slight increase in frequency of intersphincteric fistulas compared with HS . In HS, the fistulas were more often bilateral and without associated rectal wall thickening .…”

“…Monnier et al showed that the fistulas in Crohn's disease are more complex and predominantly in the perianal region, with a slight increase in frequency of intersphincteric fistulas compared with HS . In HS, the fistulas were more often bilateral and without associated rectal wall thickening . A combination of three imaging features (bilaterality, absence of rectal wall thickening, and absence of perianal predominance) was shown to differentiate HS from Crohn's disease with a specificity of 100% (Fig.…”

“…A combination of three imaging features (bilaterality, absence of rectal wall thickening, and absence of perianal predominance) was shown to differentiate HS from Crohn's disease with a specificity of 100% (Fig. ) …”