AC of the ileal reservoir of pouches has been reported. These reports are relatively uncommon, but the risk is present. Risk factors for the development of dysplasia and cancer may include the age of the pouch, chronic pouchitis, and the codiagnosis of PSC. Studies performed in Sweden suggest that the primary risk factor of neoplastic progression in the pouch is associated with chronic pouchitis resulting in permanent subtotal or total villous atrophy (Veress et al, 1995). Such atrophic changes set the stage for metaplasia (change in epithelial type in the pouch) and neoplastic transformation; therefore, patients with chronic pouchitis and villous atrophy are likely the subset best suited for pouch surveillance. The second major risk factor involves patients who have PSC and UC and have undergone an ileoanal anastomosis with pouch construction of 8 or more years duration. These UC/PSC patients develop moderate or severe atrophy in the pouch significantly more often (p < .01) than UC patients without PSC who have similar characteristics (Stahlberg et al, 2003). Otherwise, the yield for dysplasia/cancer during pouch surveillance is likely to be very low (Herlin et al, 2003; Thompson-Fawcett et al, 2001; Hulten et al, 2002).
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