Endoscopic assessment of the J pouch in ulcerative colitis: A narrative review

Patients with ulcerative colitis sometimes need a total colectomy with ileal pouch-anal anastomosis due to medically refractory disease or colitis-associated neoplasia. Up to 50% of patients with ulcerative colitis postoperatively develop pouchitis and the rate of chronic inflammatory pouch conditions requiring pouch excision or diverting ileostomy is reported to be 10%. In order to diagnose and monitor pouchitis, pouchoscopy is essential to assess endoscopic inflammatory findings of the J pouch and to survey neoplasia development, particularly in the remnant distal rectum. However, endoscopic protocols for the evaluation of the pouch may not be standardized worldwide and the reliability of existing disease activity indices for pouchitis has been questioned due to the lack of validation. Recently, reliable endoscopic scoring systems based on an observation of the anatomical location of the J pouch were reported and a significant association between the distribution pattern of endoscopic inflammation (i.e., endoscopic phenotype) and pouch outcomes was also uncovered. In this review, we discuss how to survey the J pouch using pouchoscopy, endoscopic indices for pouchitis disease activity, endoscopic phenotypes and classification, and the pathological mechanisms of pouchitis phenotype in patients with ulcerative colitis.