# Prevalence and predictability of the Chicago Classification of Pouchitis in ulcerative colitis: a multicenter study in Japan

## TL;DR

This study examines how endoscopic features of pouchitis in ulcerative colitis patients predict long-term outcomes, finding that certain classifications are linked to higher risks of complications.

## Contribution

The study provides new insights into the predictive value of the Chicago Classification for pouchitis outcomes in a Japanese multicenter cohort.

## Key findings

- Focal inflammation and inlet involvement are significantly associated with chronic pouchitis and pouch failure.
- Pouch-related fistula is a significant risk factor for pouch failure but less prevalent in this cohort compared to a US cohort.
- Diffuse inflammation and cuffitis are strongly linked to chronic pouchitis in multivariate analysis.

## Abstract

Endoscopic phenotypes of pouchitis according to the Chicago Classification have been reported to be associated with poor pouch outcomes in ulcerative colitis (UC). Here, we aimed to assess the prevalence of endoscopic phenotypes and their predictability for pouch outcomes.

This retrospective multicenter study included UC patients aged 18 years or older who underwent total colectomy between January 2000 and March 2020. The primary endpoints were frequencies of endoscopic phenotypes of the Chicago Classification and their predictability for chronic pouchitis and pouch failure. Endoscopic findings were evaluated at the initial pouchoscopy and at 3 and 10 years after ileostomy takedown.

A total of 392 eligible patients were identified. The frequencies of chronic pouchitis and pouch failure were 32% and 4.9%, respectively. Focal inflammation and inlet involvement at the initial postoperative pouchoscopy were significantly associated with subsequent risk of chronic pouchitis and pouch failure, respectively. Thirty percent of the patients with focal inflammation progressed to diffuse inflammation when chronic pouchitis developed. Multivariate analysis showed chronic pouchitis was significantly associated with diffuse inflammation and cuffitis observed throughout the clinical course. The proportion of pouch-related fistula was significantly lower in our cohort than in the US cohort (4.8% vs 19%, P < 0.001), and pouch-related fistula was an independent risk factor for pouch failure.

We demonstrated the predictability of the Chicago Classification for pouch outcomes, and a lower prevalence of pouch-related fistula, resulting in a lower pouch failure risk in our multicenter cohort.

The online version contains supplementary material available at 10.1007/s00535-025-02231-1.