title: Relationship Among Anal Sphincter Injury, Patulous Anal Canal, and Anal Pressures in Patients With Anorectal Disorders.
abstract: OBJECTIVE
  The anal sphincters and puborectalis are imaged routinely with an endoanal magnetic resonance imaging (MRI) coil, which does not assess co-aptation of the anal canal at rest. By using a MRI torso coil, we identified a patulous anal canal in some patients with anorectal disorders. We aimed to evaluate the relationship between anal sphincter and puborectalis injury, a patulous anal canal, and anal pressures.
  
  
  METHODS
  We performed a retrospective analysis of data from 119 patients who underwent MRI and manometry analysis of anal anatomy and pressures, respectively, from February 2011 through March 2013 at the Mayo Clinic. Anal pressures were determined by high-resolution manometry, anal sphincter and puborectalis injury was determined by endoanal MRI, and anal canal integrity was determined by torso MRI. Associations between manometric and anatomic parameters were evaluated with univariate and multivariate analyses.
  
  
  RESULTS
  Fecal incontinence (55 patients; 46%) and constipation (36 patients; 30%) were the main indications for testing; 49 patients (41%) had a patulous anal canal, which was associated with injury to more than 1 muscle (all P ≤ .001), and internal sphincter (P < .01), but not puborectalis (P = .09) or external sphincter (P = .06), injury. Internal (P < .01) and external sphincter injury (P = .02) and a patulous canal (P < .001), but not puborectalis injury, predicted anal resting pressure. A patulous anal canal was the only significant predictor (P < .01) of the anal squeeze pressure increment.
  
  
  CONCLUSIONS
  Patients with anorectal disorders commonly have a patulous anal canal, which is associated with more severe anal injury and independently predicted anal resting pressure and squeeze pressure increment. It therefore is important to identify a patulous anal canal because it appears to be a marker of not only anal sphincter injury but disturbances beyond sphincter injury, such as damage to the anal cushions or anal denervation.
authors: Clinical Enteric Neuroscience Translational and Epidemiological Research Program, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors: David
authors: D
authors: Prichard
authors: Clinical Enteric Neuroscience Translational and Epidemiological Research Program, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors: Doris M
authors: DM
authors: Harvey
authors: Department of Radiology, Mayo Clinic, Rochester, Minnesota.
authors: Joel G
authors: JG
authors: Fletcher
authors: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota.
authors: Alan R
authors: AR
authors: Zinsmeister
authors: Clinical Enteric Neuroscience Translational and Epidemiological Research Program, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors: Adil E
authors: AE
authors: Bharucha
mesh_terms: D000328:Adult; D000368:Aged; D001003:Anal Canal / Q000293:injuries* / Q000473:pathology*; D001004:Anus Diseases / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006874:Hydrostatic Pressure; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008365:Manometry / Q000379:methods; D008875:Middle Aged; D010502:Perineum / Q000293:injuries*; D012189:Retrospective Studies
keywords: Anal Sphincter Defects; Anorectal Imaging; Diagnosis; Risk Factor