The influence of bladder filling on anorectal function

The aim of this study was to develop a technique to simultaneously evaluate bladder and anorectal function. In particular, this study was designed to determine if anal sphincter resting pressure, anal sphincter squeeze pressure and rectal sensation change with bladder filling.

A pilot study of ten female patients who presented to the pelvic physiology unit for assessment of urinary symptoms was performed. All patients completed a symptom questionnaire and quality of life assessment form. Following informed consent a baseline urodynamic test was performed with the bladder empty and subsequently followed by an anorectal manometric test. Changes in anal sphincter resting pressure, squeeze pressure and rectal pressure were recorded over a ten-minute period. With the patient lying in the left lateral position, the bladder was then filled with isotonic saline at room temperature at a constant rate of 30 ml/min. A continuous assessment of changes in anal sphincter resting pressure during bladder filling was made. Anal sphincter squeeze pressure and rectal sensation were measured at fixed intervals during bladder filling (50, 100, 150 ml etc.) and at fixed intervals relative to bladder capacity (25, 50, 75 and 100% capacity) by stopping bladder filling at the appropriate level.

There was no significant change in anal sphincter resting pressure (Mean difference(s.d.) between bladder full and empty = 2.7(5.6) P = 0.92*), squeeze pressure (Mean(s.d.) difference = 9.5(26.3) P = 0.86*) and rectal sensation (Mean difference(s.d.) first sensation 10(15.2) P = 0.958; Mean difference(s.d.) urgency = 10(17.8) P = 0.07*) on bladder filling.

Under normal physiological circumstances, bladder filling does not influence anorectal function. *

Wilcoxon signed rank sum test. P < 0.05 considered significant. Units = mmHg