A 42-year-old asymptomatic woman has a persistent pouch vaginal fistula, as noted on a pouchogram 3 months after an ileal pouch–anal anastomosis in preparation for a diverting loop ileostomy reversal. Examination under anesthesia reveals no undrained sepsis, normal pouch mucosa, and a fistula with a discrete area of erythema at the pouch anal anastomosis. A biopsy demonstrates Paneth cell reaction, granulation tissue, and active inflammation. What is the best next step?