Impact of rectal distention on the results of evaluations of lower urinary tract sensation

Purpose: To our knowledge no systematic studies have been performed in humans to test the interaction of normal bladder and rectal sensory function. However, symptoms affecting the different pelvic viscera often coexist. Materials and Methods: In 15 healthy female volunteers sensations of bladder filling were evaluated during 2 consecutive cystometric studies, including 1 with an empty rectum and 1 with a full rectum. Similarly the electrical perception threshold was determined in the bladder when the rectum was empty and again when the rectum was full. Results: Rectal distention did not change bladder compliance during filling. When the rectum was distended, sensations of bladder filling were reported at smaller volumes. On the other hand, electrical perception thresholds in the bladder were higher when the rectum was full. Conclusions: The state of the rectum significantly influences the sensations of bladder filling and electrical bladder stimulation. These results show that before sensory testing of the bladder rectal fullness should be examined and if necessary the rectum should be emptied. The different effect of rectal distention on filling and electrical sensations represents an additional argument for different innervation of the 2 sensations in the lower urinary tract.