title: Evaluation of the paradoxical sphincter contraction by a strain/squeeze index in constipated patients.
abstract: OBJECTIVE
  One finding in patients with constipation is the paradoxical puborectalis contraction, i.e. , activation of the sphincter muscles during straining instead of relaxation. The aims of this study were to evaluate the importance of needle placement in sphincter-electromyography and to evaluate a strain/squeeze index in constipated patients and control subjects.
  
  
  METHODS
  We investigated consecutively 194 constipated patients and 16 control subjects with integrated electromyography during straining and squeezing and calculated a strain/squeeze index. The examination was performed in the puborectalis and in the external anal sphincter muscle through hook-electrodes.
  
  
  RESULTS
  There was a strong correlation between indices in the puborectalis muscle and in the external anal sphincter muscle (r = 0.70-0.80, P < 0.001). Forty-seven patients (24 percent) had a mean index of greater than 50 compared with none in the control group (P = 0.01). Mean overall index in patients was 24 (range, 0-306) vs. 18 (range, 0-45) in controls (P = 0.12). Patients with an index greater than 50 had impaired rectal evacuation (P < 0.001), increased threshold for urge (P < 0.05), and tended to have fewer stools (P = 0.06).
  
  
  CONCLUSIONS
  Quantification of paradoxical contraction in the puborectalis and external anal sphincter with a strain/squeeze index differentiates patients in whom paradoxical activity may be a cause of constipation. An index above 50 may be of pathologic significance. Correlations between activity in the puborectalis and external anal sphincter muscle were strong which suggests that investigation in one of them is sufficient.
authors.affiliation: Department of Surgical Sciences, Section for Surgery, University Hospital, Uppsala, Sweden. urban.karlbom@akademiska.se
authors.forename: Urban
authors.initials: U
authors.lastname: Karlbom
authors.forename: Karin Edebol
authors.initials: KE
authors.lastname: Eeg-Olofsson
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Graf
authors.forename: Lars
authors.initials: L
authors.lastname: Påhlman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000503:physiopathology*; D003248:Constipation / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology*