Interaction of filling related sensation between anorectum and lower urinary tract and its impact on the sequence of their evacuation. A study in healthy volunteers

Aims: The anorectum and lower urinary tract (LUT) are closely related organs: anorectal and LUT dysfunction often occur concomitant, and therapeutic actions in one organ may influence function of the other. The aim of this study was to explore the physiologic relationship between anorectal and LUT function in healthy volunteers. Methods: Two groups of healthy volunteers were studied. Anorectal and LUT sensory function was evaluated in ten volunteers during rectal balloon and bladder filling. The second group of 100 volunteers reported on defecation and micturition during five toilet visits. They graded perception on rectal and bladder fullness on a visual analogue scale and marked which organ evacuation started first. Results: The volumes at which the different sensations of rectal filling during balloon distension were perceived was significantly higher with full bladder than with empty bladder (P < 0.04). Five hundred toilet visits were described. Although mean perception grade of rectal fullness was significantly higher than for bladder fullness (P < 0.0001), defecation started only in 36% of the reported visits before micturition. Only when the rectum was considered completely full, or the bladder completely empty, defecation occurred more frequently before micturition. In all other cases, micturition more frequently occurred before defecation. Conclusions: When the bladder is full, sensation of rectal filling is decreased. When healthy people visit the toilet to defecate, the initiation of micturition often precedes that of defecation, even if both organs are considered equally full.