title: 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.
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research Program, Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA. bharucha.adil@mayo.edu
authors.forename: Adil E
authors.initials: AE
authors.lastname: Bharucha
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Croak
authors.forename: John B
authors.initials: JB
authors.lastname: Gebhart
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Berglund
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Seide
authors.forename: Alan R
authors.initials: AR
authors.lastname: Zinsmeister
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000503:physiopathology*; D003248:Constipation / Q000503:physiopathology*; D003672:Defecation; D005242:Fecal Incontinence / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008365:Manometry; D011312:Pressure; D012007:Rectum / Q000503:physiopathology*; D013314:Stress, Mechanical