Comparison between the colonic J pouch-anal anastomosis and healthy rectum: clinical and physiological function

Colonic pouch anastomosis after restorative rectal excision obviates much of the early dysfunction which is commonly experienced with the traditional straight coloanal anastomosis. A disadvantage with colonic pouch reconstruction, however, appears to be impaired evacuation.

Distal bowel function was investigated in 30 patients with a colonic J pouch anastomosis at 1 year after surgery and in 39 control subjects.

While the degree of urgency and incontinence were similar, the patients with a pouch experienced more difficult evacuation. The maximum volume of the pouch (median 235 ml) and rectum (221 ml) was similar, but the rectum was more compliant (3.5 versus 2.6 ml per cmH2O, P < 0.01). The sensory function in terms of initial sensation of filling, urge to defaecate and maximum distension pressure was impaired in those with pouches. The amplitude of the neorectal and anal canal motility pattern was threefold that of controls. Maximum volume of the pouch was significantly associated with degree of impaired evacuation; the larger the volume the more difficult the evacuation.

To reduce evacuation difficulty the pouch should not be fashioned too large. No conclusion about optimal pouch size could be drawn. In spite of fundamental physiological differences between a pouch and healthy anorectum, patients with a colonic pouch will usually experience satisfactory clinical bowel function.