Patients with inflammatory bowel disease (IBD) occasionally need a restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) because of medically refractory colitis or dysplasia/cancer. However, pouchitis may develop in up to 70% of patients after this procedure and significantly impair quality of life, more so if the inflammation becomes a chronic condition. About 10% of patients with IBD who develop pouchitis require pouch excision, and several risk factors of the failure have been reported. A phenotype that has features similar to Crohn’s disease may develop in a subset of ulcerative colitis patients following proctocolectomy with IPAA and is the most frequent reason for pouch failure. In this review, we discuss the diagnosis and prognosis of pouchitis, risk factors for pouchitis development, and treatment options for pouchitis, including the newer biological agents.

Background/Aims: Mucosal adaptation of the ileum toward colonic epithelium has been reported in pouchitis in ulcerative colitis (UC); however, the clinical characteristics, endoscopic findings, and outcomes in patients with pouchitis with ileal mucosal adaptation are poorly understood. Methods: This was a single-center retrospective study comprising UC patients treated by proctocolectomy with ileal pouch-anal anastomosis who had undergone pouchoscopy at the University of Tsukuba Hospital between 2005 and 2022. Endoscopic phenotypes were evaluated according to the Chicago classification. High-iron diamine staining (HID) was performed to identify sulfomucin (colon-type mucin)-producing goblet cells (GCs) in pouch biopsies. We compared clinical data between patients with (high HID group) and without > 10% sulfomucin-producing GCs in at least one biopsy (low HID group). Results: We reviewed 390 endoscopic examination reports from 50 patients. Focal inflammation was the most common phenotype (78%). Five patients (10%) required diverting ileostomy. Diffuse inflammation and fistula were significant risk factors for diverting ileostomy. The median proportion of sulfomucin-producing GCs on histological analysis of 82 pouch biopsies from 23 patients was 9.9% (range, 0%–93%). The duration of disease was significantly greater in the high HID group compared to the low HID group. The median percentage of sulfomucin-producing GCs was significantly higher in patients with diffuse inflammation or fistula compared to other endoscopic phenotypes (14% vs. 6.0%, P= 0.011). Conclusions Greater proportions of sulfomucin-producing GCs were observed in endoscopic phenotypes associated with poor outcomes in UC, indicating patients with pouchitis showing colonic metaplasia of GCs may benefit from early interventions.