The effect of vesical filling and voiding on the anorectal function with evidence of a 'vesico-anorectal reflex'

The aim was to evaluate the effect of vesical filling and voiding on anal c ontinence and rectal pressure. Fourteen healthy volunteers (age 37.2 +/- 9. 6 years; 10 men, four women) were studied. The response of the rectal press ure and EMG of the external (EAS) and internal (IAS) anal sphincters to slo w vesical filling and voiding was recorded before and after individual anae sthetization by xylocaine of the EAS, rectum and urinary bladder. Saline in stead of xylocaine was used as control testing. The rectal pressure and EAS EMG activity showed no response to vesical filling (P > 0.05, P > 0.05, re spectively) while a momentary increase in both parameters occurred upon voi ding (P < 0.05, P < 0.01, respectively). The IAS EMG exhibited no response to either filling or voiding. Separate anaesthetization of either of the EA S, rectum or bladder produced no response of the rectal pressure or EAS EMG activity upon vesical voiding, whereas a response was registered after sal ine administration. The increase of the rectal pressure and EAS EMG activit y upon voiding suggests the presence of a reflex relationship between the t wo actions. This relationship is evidenced by reproducibility and by abolit ion of the response on anaesthetizing either of the proposed two arms of th e reflex: the anorectum and the bladder. We call this reflex 'vesico-anorec tal reflex'. The clinical significance of this vesico-anorectal reflex rema ins to be established.