Effect of rectal distension on vesical motor activity in humans: the identification of the recto-vesicourethral reflex.

OBJECTIVE

Rectal lesions have an effect on the urinary bladder and its sphincters. Patients with constipation sometimes complain of difficult micturition or of retention. Urinary retention may also occur after anorectal operations. We investigated the hypothesis that rectal distension affects vesical dilatation through a reflex action.

METHODS

The study comprised 22 healthy volunteers (14 men, 8 women, age 42.3 +/- 10.3 SD years). The rectum was distended by rectal balloon inflated with air in increments of 50 mL. The vesical and posterior urethral pressures were recorded before and after individual anesthetization of the rectum, bladder, and posterior urethra.

RESULTS

Fifty-milliliter rectal distension effected no vesicourethral pressure response (P > 0.05). At 100 and up to 300-mL distension, the vesical pressure decreased (P < 0.05), while the urethral pressure increased (P < 0.05). The response showed no significant difference upon increase of the distending volume. The mean latency was 16.8 +/- 2.4 milliseconds. Vesicourethral pressure did not respond to rectal distension when the bladder, urethra, or rectum was individually anesthetized.

CONCLUSIONS

Rectal distension seems to induce diminished vesical, but increased urethral sphincter tone, an effect that is presumably mediated through a reflex that we call the "recto-vesicourethral reflex." This reflex is apparently evoked at defecation to abort simultaneous micturition. The clinical significance of the reflex needs to be established.