Ileal pouch-anal anastomosis (IPAA) after total proctocolectomy is the surgical treatment of choice for ulcerative colitis (UC) patients with medically refractory disease or dysplasia. IPAA significantly improves quality of life in UC patients who require surgery. However, certain inflammatory and noninflammatory diseases can develop after the surgery, including pouchitis, Crohn's disease (CD) of the pouch, cuffitis, and irritable pouch syndrome. The cause and pathogenesis of these disease conditions of IPAA are largely unknown. Accurate diagnosis and classification are important for appropriate management.