Histopathology of Pouch and Para-Pouch Inflammatory and Neoplastic Disorders

BACKGROUND: Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) is used to treat patients with ulcerative colitis or familial adenomatous polyposis who need colectomy. While this procedure substantially improves patient’s quality of life and reduces cancer risk, it is associated with a variety of sequelae‚ including surgical complications, inflammatory disorders, and neoplasia. Pouchitis, cuffitis, and Crohn’s disease of the pouch are the most common inflammatory disorders of the pouch and para-pouch. OBJECTIVE: This study aimed to elaborate on the histopathology of common inflammatory and neoplastic disorders of the pouch and para-pouch. DATA SOURCES: A Medline search for English language studies published between 1981 and 2021 using the PubMed search engine. The terms “ileal pouch-anal anastomosis,” “pouchitis,” “pouchitis activity score,” “secondary pouchitis,” “Crohn’s disease of the pouch,” “Crohn’s-like conditions of the pouch,” “pre-pouch ileitis,” “cuffitis,” “pouch adenocarcinoma,” and “pouch neoplasia” were used. STUDY SELECTION: The published human studies that reported histopathology of common inflammatory and neoplastic disorders of the ileal pouch were selected and reviewed. CONCLUSIONS: Histologic examination plays an essential role in confirming inflammation in pouchitis, identifying etiology and clues for secondary pouchitis, and diagnosing neoplasia. A standardized, simple, and reproducible histologic grading system for pouchitis is needed. Pouch and para-pouch glandular dysplasia diagnosis is challenging and should always be reviewed by at least one gastrointestinal pathologist.