# Histopathological Findings of Appendix Specimens in Quiescent Ulcerative Colitis: Correlations With Clinical Outcomes in the ACCURE Trial

## TL;DR

This study found active inflammation in the appendix of many ulcerative colitis patients in remission, which may be linked to higher relapse risk after surgery.

## Contribution

The study identifies histopathological features in the appendix that correlate with clinical outcomes in quiescent ulcerative colitis.

## Key findings

- Active appendiceal inflammation was present in 55.4% of patients in clinical remission.
- Peri-appendiceal red patch and larger appendiceal diameter were linked to more severe inflammation.
- Epithelial neutrophil involvement above 5% of crypts was associated with higher relapse rates.

## Abstract

The ACCURE trial demonstrated that appendicectomy reduces relapse rates within 1 year in patients with ulcerative colitis (UC) in remission. We aimed to explore appendiceal histopathology in quiescent UC and assess its association with postoperative relapse.

Appendix specimens from Dutch participants in the ACCURE trial were reassessed by a blinded gastrointestinal pathologist using the Robarts Histopathology Index (RHI; range 0–33). Active appendiceal inflammation was defined as RHI > 3. Clinical data, preoperative endoscopic findings including peri‐appendiceal red patch (PARP), and outcomes were correlated with histopathological findings. Inter‐observer agreement between local and central scoring was assessed, along with relapse‐free survival in relation to RHI severity.

Of 65 patients, 49 (75.4%) maintained remission and 16 (24.6%) relapsed within one year. Active inflammation was present in 55.4% (36/65). Inter‐observer agreement was moderate (κ = 0.47, 95% CI 0.29–0.64, p < 0.001). Inflammation was more frequent in patients diagnosed at a younger age (median 28 vs. 34 years, p = 0.09), and greater in those with PARP (RHI 15.5 vs. 5.0, p = 0.005). Extensive epithelial neutrophil involvement (> 5% of crypts) was associated with higher relapse rates (44.4% vs. 18.0%, p = 0.05). Relapsing patients also had larger appendiceal diameters (median 9 vs. 7 mm, p = 0.03).

Active appendiceal inflammation is prevalent in quiescent UC and showed a trend toward association with relapse risk. Although the benefit of appendicectomy in this group cannot be confirmed on these data alone, the finding might be clinically relevant as relapse rates are significantly reduced in the appendicectomy group.

Summarise the established knowledge on this subject◦The appendix is hypothesized to play a role in ulcerative colitis (UC) pathogenesis, with previous studies showing improved disease outcomes following appendicectomy.◦Active appendiceal inflammation has been found in UC patients regardless of endoscopic disease extent or activity.◦The ACCURE trial demonstrated reduced relapse rates after appendicectomy in patients with quiescent UC.What are the significant and/or new findings of this study?◦Active appendiceal inflammation (RHI > 3) was found in over half of the UC patients in clinical remission.◦Peri‐appendiceal red patch (PARP) and larger appendiceal diameter correlated with more severe histological inflammation.◦Presence of epithelial neutrophils (> 5% of crypts) was associated with a higher relapse risk post‐appendicectomy.◦Increasing RHI scores showed a non‐significant trend toward shorter time to relapse, suggesting a prognostic value of appendix histopathology in quiescent UC that requires confirmation in larger studies.

Summarise the established knowledge on this subject

The appendix is hypothesized to play a role in ulcerative colitis (UC) pathogenesis, with previous studies showing improved disease outcomes following appendicectomy.

Active appendiceal inflammation has been found in UC patients regardless of endoscopic disease extent or activity.

The ACCURE trial demonstrated reduced relapse rates after appendicectomy in patients with quiescent UC.

What are the significant and/or new findings of this study?

Active appendiceal inflammation (RHI > 3) was found in over half of the UC patients in clinical remission.

Peri‐appendiceal red patch (PARP) and larger appendiceal diameter correlated with more severe histological inflammation.

Presence of epithelial neutrophils (> 5% of crypts) was associated with a higher relapse risk post‐appendicectomy.

Increasing RHI scores showed a non‐significant trend toward shorter time to relapse, suggesting a prognostic value of appendix histopathology in quiescent UC that requires confirmation in larger studies.