Bowel function varies markedly among patients with colectomy and ileal pouch-anal anastomosis. Little is known of the mechanisms controlling fecal continence and frequency of defecation after operation. The aim of this study was to determine which features of the anal sphincter and neorectum accounted for the variation in clinical outcome. Twenty patients were studied 4 to 35 months after operation and compared to 12 healthy volunteers. Despite several patients exhibiting impaired fecal continence, anal sphincteric length and pressures and ileal pouch capacity and distensibility were similar in patients and controls. Patients with poor results, however, had rapid filling of their ileal pouch, which resulted in early onset of high amplitude propulsive pressure waves in the pouch. As these waves became more frequent, defecation resulted. Patients with poor results also were not able to empty adequately their pouch. The poorer the completeness of evacuation, the more frequent the defecation (r = 0.62, p less than 0.01). The authors conclude that rapid pouch filling and impaired pouch evacuation can lead to increased stool frequency in patients after ileal pouch-anal anastomosis.
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