PARADOXICAL SPHINCTER CONTRACTION IS RARELY INDICATIVE OF ANISMUS

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, pa radoxical sphincter contraction (PSC) also occurs in healthy controls, so anismus may be diagnosed too often because it may be based on a no n-specific finding related to untoward conditions during the anorectal examination. Aims-To investigate the pathophysiological importance of PSC found at anorectal manometry in constipated patients and in patie nts with stool incontinence. Methods-Digital rectal examination and an orectal manometry were performed in 102 chronically constipated patien ts, 102 patients with stool incontinence, and in 18 controls without a norectal disease. In 120 of the 222 subjects defaecography was also pe rformed. Paradoxical sphincter contraction was defined as a sustained increase in sphincter pressure during straining. Anismus uas assumed w hen PSC was present on anorectal manometry and digital rectal examinat ion and the anorectal angle did not widen on defaecography. Results-Ma nometric PSC occurred about twice as often in constipated patients as in incontinent patients (41.2% versus 25.5%, p<0.017) and its prevalen ce 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 f inding in healthy controls as well as in patients with chronic constip ation and stool incontinence. Hence, PSC is primarily a laboratory art efact and true anismus is rare.