Comparison of rectoanal axial forces in health and functional defecatory disorders

Abstract

Anal manometry measures circumferential pressures but not axial forces that are responsible for defecation and contribute to fecal continence. Our aims were to investigate these mechanisms by measuring axial rectoanal forces with an intrarectal sphere or a latex balloon fixed at 8, 6, or 4 cm from the anal verge and connected to axial force and displacement transducers. Rectoanal forces and rectal pressures within a latex balloon were measured at baseline (i.e., at rest) and during maneuvers (i.e., squeeze, simulated evacuation, and a Valsalva maneuver) in 12 asymptomatic women and 12 women with symptoms of difficult defecation. Anal resting and squeeze pressures were also assessed by manometry and were similar in control patients and experimental patients. At rest, axial rectoanal forces were directed inward and increased as the device approached the anal verge. Control patients augmented this inward force when they squeezed and exerted an outward force during simulated expulsion and a Valsalva maneuver. The force change during maneuvers was also affected by device location and was highest at 4 cm from the verge. In experimental patients, the force at rest and the change in force during all maneuvers was lower than in control patients. The rectal pressure during a Valsalva maneuver was also lower in experimental patients than in control patients, suggestive of impaired propulsion. In conclusion, a subset of women with defecatory symptoms had weaker axial forces not only during expulsion but also during a Valsalva maneuver and when they squeezed (i.e., contracted) their pelvic floor muscles, suggestive of generalized pelvic floor weakness.

Age effects on anorectal pressure in anal continent women with lower urinary tract dysfunction

“…In our study, we chose to place the pressure catheter 10 cm into the anorectum, above the anal verge. Recent studies [20] show the puborectalis to be consistently at 6 cm proximal to the anal verge. Although there might be an ethnic difference in this anatomical correlation, we could not exclude the possibility that increased length might confound the data by falsely elevating pressure due to a volume effect.…”

Diagnostic accuracy study of anorectal manometry for diagnosis of dyssynergic defecation

“…[2–4] The Rome criteria for functional defaecation disorder (FDD) implicate disordered evacuation due to an inadequate rectoanal pressure gradient resulting from paradoxical contraction or inadequate relaxation of the pelvic floor muscles and/or to inadequate rectal propulsive forces during defaecation. [5–7] Thus to fulfil current (Rome III) diagnostic criteria for FDD, patients with FC must have evidence of two of the following criteria: (a) impaired evacuation; (b) inappropriate contraction of the pelvic floor muscles or <20% relaxation of basal resting pressure; (c) inadequate propulsive forces. [5] While impaired evacuation is usually assessed by balloon expulsion [8] or imaging [9, 10], criteria (b) and (c) are assessed by measuring rectal and anal pressures during simulated evacuation (“push” manoeuvre) with anorectal manometry (AM).…”

Long-Term Efficacy of Biofeedback Therapy for Dyssynergic Defecation: Randomized Controlled Trial

“…Also known as anismus (5) or pelvic floor dyssynergia (6), dyssynergia is characterized by a failure of the abdominal, rectal, pelvic floor and anal sphincter muscles to effectively coordinate and complete the process of defecation (6–10). Consequently, these patients complain of excessive straining, incomplete evacuation and hard stools together with infrequent stooling (3,4,11), and about 40% use digital maneuvers to assist defecation (11).…”

“…Most of them are refractory to traditional approaches of management of constipation. The impaired propulsion of stool from the rectum, paradoxical anal contraction or inadequate anal relaxation together with impaired rectal sensation or a combination of these mechanisms leads to dyssynergic defecation (7,9,10). …”