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

To determine whether Hidradenitis suppurativa (HS)-related anoperineal disease can be distinguished from Crohn's disease (CD) using MRI. Pelvic MRI of 23 HS and 46 CD patients with anoperineal disease between 2007 and 2014 were independently analysed by two radiologists. For diagnosis of HS, sensitivity, specificity and positive likelihood ratios (LRs) of inflammatory features and of their anatomical distribution were calculated and compared to those of CD. In HS, fistulae were less present (P = .033) and less frequently involved the sphincters (P = .001) than in CD. Granulomas were more frequent (P = .0005). For anterior/inguinal and posterior localizations, sensitivity, specificity and LR for diagnosis of HS were 70% (49.1, 84.4), 87% (74.3, 93.9), 5.3 (2.41, 11.79) and 57% (36.8, 74.4), 93% (82.5, 97.8), 8.67 (2.74, 27.41), respectively. Combination of signs including posterior involvement, absence of rectal wall thickening and bilaterality of features yielded specificity of 100% (95% CI: 92.3-100) for HS. Although MRI presentations of anoperineal disease may overlap between CD and HS, specific diagnosis of HS is possible with a combination of three features: absence of features' predominance in perianal area, absence of rectal wall thickening and bilaterality of features. aEuro cent Spectrum of MRI features of HS-related anoperineal disease is wide. aEuro cent Specific diagnosis of HS-related anoperineal disease is possible using MR imaging. aEuro cent A combination of three MR signs allows distinction between HS and CD.