Prospectively evaluating anal sphincter function after ileal pouch-anal canal anastomosis

The decreased anal sphincter pressure that occurs after ileal pouch-anal canal anastomosis (IPAA) has usually been attributed to damage of the internal and sphincter. We hypothesized that the operation damages both the internal and the external anal sphincter. Resting pressure in the anal canal (a function of internal and external sphincters), anal squeeze pressure (a function of external sphincter only), and the rectal-anal inhibitory reflex (involving the internal sphincter) were measured manometrically in 10 patients with ulcerative colitis (4 women and 6 men; mean age, 33 years; range: 20 to 49 years). The patients were studied while awake before IPAA, under general anesthesia with striated muscle blockade just before incision, awake 2 months later before ileostomy takedown, and again under anesthesia with blockade just before takedown. The operation decreased maximum resting anal pressure while awake and during anesthesia with blockade. The decrease was detected in the proximal anal canal but not in the distal anal canal. In addition, the operation impaired anal squeeze pressure and abolished the rectal-anal inhibitory reflex. We conclude that IPAA damages both the internal and the external anal sphincter.