Review article: the histological assessment of disease activity in ulcerative colitis

BACKGROUND: In patients with ulcerative colitis (UC), mucosal healing has emerged as a major therapeutic goal, and is usually assessed endoscopically. Histological healing does not correlate very well with endoscopic mucosal healing in UC and persistent histological inflammation might be a better predictor of future clinical relapse than the endoscopic appearance alone. AIM: To define how histological assessment of disease activity should be best done in UC. METHODS: Electronic (PubMed/Embase) and manual search. RESULTS: At least 18 histological indices to assess disease activity in UC have been described, though none are fully validated. However, histological assessment is increasingly used as a secondary endpoint in clinical trials in UC. After reviewing and discussing existing histological scoring systems for UC activity, we describe features of histological response and define three grades of activity: (i) histological healing - complete resolution of abnormalities; (ii) quiescent disease, - lack of mucosal neutrophils but chronic inflammation may remain; (iii) active disease - presence of neutrophils plus possible epithelial damage. It is recommended that two biopsies are taken from each colonic segment which should include always biopsy of the rectum and the most affected segments. There is to date no agreed preferable scoring system but the Geboes Index is the best validated (kappa for interobserver variation 0.59-0.70). CONCLUSION: Histological assessment of disease activity in UC is increasingly used, but needs to be carefully defined.