Purpose: Blunted rectal sensation, or rectal hyposensitivity, has been reported anecdotally in patients with functional disorders of evacuation and continence. The purpose of this study was to determine the prevalence of rectal hyposensitivity and whether the finding of such an abnormality was associated with any clinical impact.
Methods: One thousand three hundred fifty-one patients, referred for anorectal physiologic investigation, were divided according to presenting symptoms into the following categories: constipation (subdivided into infrequency of and/or obstructed defecation), fecal incontinence (subdivided into passive, postdefecation, and urge incontinence), fecal incontinence and constipation, or "other." Rectal hyposensitivity was judged to be present when at least one of the sensory threshold volumes was elevated beyond the normal range (mean plus 2 standard deviations). The prevalence of rectal hyposensitivity was then calculated in each group and in relation to other investigations.
Results: Rectal hyposensitivity was present in 16 percent of patients, with males and females equally affected. Twenty-three percent of patients with constipation, 10 percent of patients with fecal incontinence, 27 percent of patients with incontinence associated with constipation, and only 5 percent of patients with other symptoms were found to have rectal hyposensitivity. In patients with obstructed defecation, rectal hyposensitivity was present in 33 percent with rectocele, 40 percent with intussusception, and 53 percent with no mechanical obstruction evident on evacuation proctography.
Conclusion: Rectal hyposensitivity is common in patients with constipation and/or fecal incontinence and may thus be important in the etiology of such conditions. Although the clinical relevance of this physiologic abnormality is unknown, its presence may have implications regarding the management of hindgut dysfunction and particularly the selection of patients for surgery.