Functional obstructive defaecation

Abstract

Objective: To study patients with obstructive defaecation to determine quantitatively its pathophysiology and homogeneity. Design: Twenty-two patients with obstructive defaecation were studied by isotope proctography and by conventional methods for quantitative analysis of the pathophysiological factors involved. Methods: Examination of the patients included ano-rectal manometry, the rectal balloon expulsion test, pelvic floor electromyography and isotope proctography. Eleven asymptomatic subjects were studied for comparison. Results: Pelvic floor electromyography revealed increased 'straining electromyographic activity' in all patients (P< 0.001). Patients with obstructive defaecation had impaired rectal sensation and were unable to perform a complete rectal evacuation (54% rectal evacuation) on isotope proctography. The defaecation time was prolonged and was associated with a reduced defaecation rate. Simultaneous recording of intrarectal pressures and external anal sphincter (EAS) electromyography during proctography revealed increased intrarectal pressure (P<0.0001) and EAS electromyographic voltage (P<0.01) during evacuation. The anorectal angles correlated with the pelvic floor movement and the anismus index. The anismus index in these patients correlated with the intrarectal pressure (P<0.02). No increase in the electromyographic voltage of the EAS was observed in any of the control subjects who successfully performed rectal balloon expulsion. Conclusion: Obstructive defaecation is a multifactórial condition involving derangements of rectal sensation and abnormal activity of the pelvic floor and anal sphincter musculature; its homogeneity is affected by the duration of the process.