The effect of stool consistency on rectal and neorectal emptying

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Abstract
Although stool consistency is considered to be an important component of anorectal continence, its effect on rectal emptying has never been quantitated. In 12 healthy volunteers and 12 patients after ileal pouch-anal anastomosis (IPAA) (46±5 months after the operation; mean ± SEM), perfused anal manometry was performed; movements of the anorectal angle were quantitated scintigraphically; and rectal capacity and compliance were measured by air insufflation of an intrarectal balloon at three infusion rates. The efficiency of rectal evacuation of three consistencies (5 percent, liquid; 7.5 percent semisolid gel; 11.25 percent solid gel; w/w) of Tc99m labeled artificial stool (aluminum magnesium silicate gel) was quantitated by gamma camera imaging. No abnormalities of pelvic floor function were demonstrated in either controls or patients. The mean neorectal capacity and compliance of patients with IPAA did not differ from control, (capacity; IPAA: 215±22 ml vs. control; 245±29 ml; compliance; IPAA: 5.5±0.7 ml/cm H2O vs. control; 6.6±0.7 ml/cm H2O; P>0.05). In controls, the percentage of the 7.5 percent consistency evacuated (81±5 percent, mean ± SEM) was significantly more than the percentage evacuation of either the 5 percent consistency (67±7 percent) or the 11.25 percent consistency (77±2 percent) (P0.1). We concluded that in healthy subjects but not in patients after IPAA, stool consistency affected the efficiency of evacuation of enteric content.