The diagnosis and treatment of pouchitis in inflammatory bowel disease.

The ileal pouch anal anastomosis (IPAA) procedure has become the preferred surgical option for most patients with ulcerative colitis who require surgical removal of the colorectum. The vast majority of patients with this new anatomy will either not develop pouchitis or develop a few discrete episodes of acute pouchitis. However approximately one fourth of patients will develop recurrent pouchitis, with 5% being categorized as chronic pouchitis requiring maintenance therapy or, on rare occasion, pouch excision. Factors that are associated with an increased risk of pouchitis include primary sclerosing cholangitis, extraintestinal manifestations, and nonsmokers. Controversy surrounds other risk factors such as extent of colitis, backwash ileitis, preoperative pANCA levels, and carrying a specific allele for IL-1 receptor antagonist. The etiology of pouchitis is unknown, but theories range from genetic susceptibility, bacterial overgrowth, ischemia, and fecal stasis, to a recurrence of ulcerative colitis in the pouch, a missed diagnosis of Crohn's disease, or possibly a novel third form of inflammatory bowel disease. Some patients with symptoms of pouchitis will not have inflammation of the pouch, but rather, irritable pouch syndrome. Thus, endoscopic investigation with biopsy is important for declaring whether a patient has pouchitis. Indeed, the more commonly used scores, such as the pouch disease activity index, incorporate both endoscopic and histologic criteria. Not surprisingly, treatment options for patients with pouchitis resemble that of regular inflammatory bowel disease, although there have only been a few controlled trials. Antibiotics are the mainstay of therapy, with metronidazole and ciprofloxacin demonstrating benefit in controlled trials. Probiotics are effective for maintaining remission of pouchitis. Mesalamine, corticosteroids, and immunomodulators have been used with some success. Occasionally, patients with well-documented ulcerative colitis as the indication for IPAA will develop what appears to be Crohn's disease of the pouch, on the basis of granulomatous inflammation, pre-pouch ileitis, or fistulae. The treatment is similar to Crohn's disease, including the use of infliximab. Dysplasia within the pouch mucosa itself is quite rare. Reports of dysplasia occurring in patients with IPAA are usually due to neoplastic change within the residual cuff of rectal or transition zone mucosa just below the pouch, rather than in the ileal mucosa of the pouch. With further elucidation of the genetic basis for inflammatory bowel disease, we should be able to more accurately classify patients with ulcerative colitis and Crohn's disease genotypically. Hopefully, this will also bring more clarity to the heterogeneous population of patients with pouchitis and allow for more focused therapeutic strategies.