Determinants of Fecal Continence in Healthy, Continent Subjects: A Comprehensive Analysis by Anal Manometry, Rectal Barostat and a Stool Substitute Retention Test

Abstract

Background/Aims: This study aimed to identify anal sphincter and rectal factors that determine anorectal filling sensations and continence during rectal filling in health. Methods: Measurements of anorectal physiology were collected from 42 continent healthy subjects participating in a prospective trial. Rectal function and capacity were assessed by barostat. Anal sphincter functions were assessed by manometry. A validated stool substitute retention test was performed in which a viscous suspension was infused into the rectum at 60 ml/min to 1,500 ml. Multivariate regression was applied to identify physiologic factors that determine anorectal sensation and continence during rectal filling. Results: The volume at which first awareness of rectal filling occurred associated with age (p < 0.03), rectal capacity (p < 0.06) and anal resting pressure (p < 0.003); urgency associated with rectal capacity (p < 0.0007), anal resting (p < 0.04) and squeeze pressure (p < 0.02); volume at first incontinence with rectal capacity (p < 0.0001) and squeeze pressure (p < 0.04) and the maximum volume retained were closely correlated with rectal capacity only (p < 0.0001). Conclusion: Anorectal filling sensations and continence in health require a rectal reservoir of adequate capacity and effective voluntary anal sphincter function. Complementary associations between continence, motor and sensory function indicate the presence of an adaptive mechanism that enables timely, appropriate responses to events that threaten fecal continence.

Rectal hyposensitivity for non-noxious stimuli, postprandial hypersensitivity and its correlation with symptoms in complete spinal cord injury with neurogenic bowel dysfunction

“…This could be related to a lesser or difficult contact with the receptors at the rectal wall, which strengthen the participation of the rectum in the mechanism of defecation and agree with the concept that anorectal filling sensations and continence require a rectal reservoir of adequate capacity. 21 After food, increased episodes of solid fecal incontinence were related to lower rectal tone. The clinical implications of these findings are that SCI patients may present more episodes of fecal incontinence after food.…”

Toward more accurate measurements of anorectal motor and sensory function in routine clinical practice: Validation of High‐Resolution Anorectal Manometry and Rapid Barostat Bag measurements of rectal function

“…There is a need for accurate and clinically meaningful measurements of rectal function that can be acquired without specialist equipment in a short time frame. Previously, we performed a biophysical analysis of manometry and barostat data to identify determinants of continence function . The results demonstrated that, in addition to anal sphincter pressure, the most important determinant of rectal sensation and continence during rectal filling was rectal capacity defined by intra‐bag volume at 40 mmHg .…”

“…Advantages of measuring rectal capacity in clinical studies include: (i) direct assessment of rectal reservoir capacity (i.e., the maximum volume that can be retained before continence is lost); (ii) measurement of rectal filling sensations as a proportion of rectal capacity (normalized rectal volume) . The latter is helpful because, as with standard barostat measurements of pressure thresholds, this correction allows volume thresholds of rectal sensations to be compared between subjects in terms of ‘percentage filling’ of rectal capacity …”

Anal Manometry in the Investigation of Fecal Incontinence: totum pro parte, not pars pro toto

“…However, in others, it is likely because changes in rectal sensitivity and adaptation of patient behaviors compensate for potential weaknesses in the system. This is illustrated by our work that reveals a dynamic interaction between continence function, anal sphincter pressure and rectal sensation during rectal filling [9]. In healthy subjects there are highly significant associations between (i) low resting tone and a low threshold volume for first sensation and (ii) low squeeze pressure and a low threshold volume for urge to defecate [9].…”

“…This is illustrated by our work that reveals a dynamic interaction between continence function, anal sphincter pressure and rectal sensation during rectal filling [9]. In healthy subjects there are highly significant associations between (i) low resting tone and a low threshold volume for first sensation and (ii) low squeeze pressure and a low threshold volume for urge to defecate [9]. These findings indicate the presence of an adaptive mechanism in health that enables timely, appropriate responses to events that threaten fecal continence.…”