title: Paradoxical sphincter contraction is rarely indicative of anismus.
abstract: BACKGROUND
  Anismus is thought to be a cause of chronic constipation by producing outlet obstruction. The underlying mechanism is paradoxical contraction of the anal sphincter or puborectalis muscle. However, paradoxical sphincter contraction (PSC) also occurs in healthy controls, so anismus may be diagnosed too often because it may be based on a non-specific finding related to untoward conditions during the anorectal examination.
  
  
  OBJECTIVE
  To investigate the pathophysiological importance of PSC found at anorectal manometry in constipated patients and in patients with stool incontinence.
  
  
  METHODS
  Digital rectal examination and anorectal manometry were performed in 102 chronically constipated patients, 102 patients with stool incontinence, and in 18 controls without anorectal disease. In 120 of the 222 subjects defaecography was also performed. Paradoxical sphincter contraction was defined as a sustained increase in sphincter pressure during straining. Anismus was assumed when PSC was present on anorectal manometry and digital rectal examination and the anorectal angle did not widen on defaecography.
  
  
  RESULTS
  Manometric PSC occurred about twice as often in constipated patients as in incontinent patients (41.2% versus 25.5%, p < 0.017) and its prevalence was similar in incontinent patients and controls (25.5% versus 22.2%). Oroanal or rectosigmoid transit times in constipated patients with and without PSC did not differ significantly (total 64.6 (8.9) hours versus 54.2 (8.1) hours; rectosigmoid 14.9 (2.4) hours versus 13.8 (2.5) hours).
  
  
  CONCLUSIONS
  Paradoxical sphincter contraction is a common finding in healthy controls as well as in patients with chronic constipation and stool incontinence. Hence, PSC is primarily a laboratory artefact and true anismus is rare.
authors.affiliation: Medizinische Klinik, Klinikum Innenstadt, University of Munich, Germany.
authors.forename: W A
authors.initials: WA
authors.lastname: Voderholzer
authors.forename: D A
authors.initials: DA
authors.lastname: Neuhaus
authors.forename: A G
authors.initials: AG
authors.lastname: Klauser
authors.forename: K
authors.initials: K
authors.lastname: Tzavella
authors.forename: S A
authors.initials: SA
authors.lastname: Müller-Lissner
authors.forename: N E
authors.initials: NE
authors.lastname: Schindlbeck
mesh_terms: D001003:Anal Canal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001004:Anus Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003248:Constipation / Q000000981:diagnostic imaging / Q000503:physiopathology; D003672:Defecation; D005242:Fecal Incontinence / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D005772:Gastrointestinal Transit; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D010808:Physical Examination; D011859:Radiography