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

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.