CASE SERIES OF COMPLEX PERIANAL FISTULAS WITHOUT LUMINAL CROHN’S DISEASE AT TERTIARY CENTER

Abstract INTRODUCTION Complex perianal fistulas are difficult to manage and often require a multimodal approach involving colorectal surgeons and gastroenterologists. The initial presentation is atypical of classic gastrointestinal symptoms, making the diagnosis even more complicated. Based on population-based studies, up to 25% of patients with Crohn’s develop fistulas, although the development of isolated perianal Crohn’s is rare. We present our clinical approach for nine patients with isolated perianal Crohn’s, with a broad diagnostic timeline. METHODS Data were collected through a retrospective chart review of nine adult patients with complex isolated perianal fistulas. Patient age, initial symptoms, diagnostic evaluation including endoscopy and radiology imaging, medical therapy and surgical interventions, and Parks classification were compiled. RESULTS Data were collected from 9 patients (66% male, 33% female, with a mean age of 33 years). All patients had been previously treated with oral or intravenous antibiotics. All the patients underwent diagnostic imaging using MRI and CT. Colonoscopy with biopsies, including TI, was not congruent with Crohn’s. The initial gastrointestinal symptoms reported were constipation (33%), loose stools (22%), hematochezia, and abdominal pain (22%). Perirectal pain and abscess drainage were reported in all the patients (100%). Two patients (22%) underwent fistulotomy and I&D with seton placement, respectively. I&D with drain placements in three patients (33%), I&D with seton placement in two patients (22%), in two patients (22%). Eight patients were treated with inflammatory bowel therapy. Six patients (67%) are on infliximab, monotherapy. One patient received combination therapy with infliximab and azathioprine 150 mg daily and allopurinol 300 mg. One patient was on therapy with guselkumab and upadacitinib (45 mg daily), with promising fistula healing. CONCLUSIONS The cases described present the multimodal importance of perianal Crohn’s involving immunomodulators and surgical intervention in patients without luminal inflammation. This patient cohort includes patients who are currently receiving induction doses of infliximab to an established patient on infliximab 10 mg/kg. Anti-TNF therapy was used as the baseline therapy in our patients. Combination therapy with immune modulators and small molecules has proven effective in patients with failure of anti-TNF therapy. This case series highlights the importance of considering CD in the differential diagnosis of isolated perianal disease without luminal inflammation.