Differentiating Perianal Fistulizing Disease in IBD and Hidradenitis Suppurativa

Conclusions

• Perianal fistulizing disease in Crohn’s disease and hidradenitis suppurativa is often difficult to distinguish clinically, and misclassification is common.
• A careful history and exam can help: HS is more associated with younger age, smoking, higher BMI, groin/axillary involvement, bilateral lesions, and subcutaneous tunnels, whereas IBD is more associated with older age, digestive symptoms, perineal disease, true fistulas, abscesses, tags, knife-cut ulcers, and genital edema.
• MRI adds important discriminatory value, with subcutaneous tunnels and inguinal lymphadenopathy favoring HS and transsphincteric/intersphincteric fistulas, rectal inflammation, and mesorectal lymphadenopathy favoring IBD.
• Blood inflammatory markers such as neutrophil-to-lymphocyte ratio and severe anemia tend to support IBD more than HS, although they are not definitive on their own.
• Colonoscopy and imaging can reveal luminal disease, but perianal IBD may still occur without obvious luminal involvement, so diagnosis can remain challenging.
• An interdisciplinary approach involving dermatology, gastroenterology, and colorectal surgery is essential when clinical features are ambiguous.
• The study’s MRI-based scoring system appears promising for separating perianal HS from perianal Crohn’s disease, but it still requires validation.
• Cutaneous Crohn’s disease should be divided into contiguous perianal fistulizing disease and noncontiguous metastatic disease, because they are biologically and diagnostically distinct.
• Diagnosis of metastatic cutaneous Crohn’s disease relies on clinical criteria plus exclusion of infection and other granulomatous disorders, with histology helpful but not always required.
• Overall, the speaker argues that perianal inflammatory fistulizing disease may deserve recognition as a separate diagnostic and management category because current tools are imperfect and treatment decisions can hinge on the distinction.