Incontinence and Anal Sphincter Pressure Predicts Rectal Sensitivity During High Resolution Anorectal Manometry

Abstract

Purpose: The etiology behind fecal incontinence has classically been interpreted as being secondary to a variation in the mechanical or neurological functionality of the anal sphincter. This has consequently been observed as decreased anal sphincter pressure utilizing anorectal manometry. While the clinical manifestation of reduced anal sphincter pressure is soiling, several patients with fecal incontinence complain of urgency as well. Whether this urgency is attributable to true rectal hypersensitivity or the perception of soiled material is not clear. The purpose of this study was to evaluate rectal sensitivity in patients with fecal incontinence. Methods: Consecutive FI patients referred to a tertiary care medical center presenting for high resolution anorectal manometry were eligible for analysis. Subjects were excluded if they reported a diagnosis of IBS meeting Rome I criteria, or contained possible inflammatory pathology of the rectum-including ulcerative colitis, HIV, and infection. After exclusion criteria were met, subjects were then divided into two groups: those presenting with clinical fecal incontinence and those who were not presenting for clinical fecal incontinence. Anorectal information and reason for the test was captured. The data were then compared between groups for maximum anorectal squeeze pressure, maximum resting anorectal pressure, balloon threshold for sensation of urge, and balloon threshold for first sensation. Results: 188 subjects were referred for high resolution anorectal manometry and entered into the database. Of the 188 subjects evaluated, 14 were excluded. Among the remaining 174 subjects, 83 (48%) were evaluated for clinical fecal incontinence or soiling, while 91 (52%) failed to present with this history. Incontinent subjects had significantly lower resting (49.6±3.2 vs. 69.3±3.1) and squeeze pressures (117.9±6.9 vs. 179.0±8.6) compared to control subjects in the anal sphincter (see Table 1). However, incontinent patients also manifested significant rectal hypersensitivity (see Table 1). Furthermore, only 8.7% of incontinent patients showed greater than normal volume for urge.Table 1Conclusion: Patients who reported clinical fecal incontinence manifested rectal hypersensitivity. This points to a possible adaptive rectal hypervigilance process and argues against sensorimotor neuropathy as a key cause of incontinence.