Application value of Nancy index in evaluating mucosal healing of ulcerative colitis

Ulcerative colitis （UC） is a chronic recurrent inflammatory bowel disease, which is characterized by persistent mucosal inflammation in the colorectal system. Endoscopic mucosal healing is considered to be the main therapeutic goal of UC. However, mucosal healing does not necessarily represent histological healing. Compared with endoscopic remission, histological remission of UC yields better clinical prognosis. A validated universal histological grading system is urgently required. Nancy index, the latest validated histological index, consists of three histological items of ulcer, acute inflammatory cell infiltration and chronic inflammatory cell infiltration, defining five histological disease activity ranging from grade 0-4. Nancy index has prognostic value for histological disease activity in UC patients, which has the potential to become a universal histological tool for clinical practice and clinical trials. This article aims to review the application value of Nancy index in evaluating mucosal healing in UC patients.