A study of the effect of renal pelvic and ureteric distention on the anorectal function with identification of the "reno-anal reflex".

Renal or ureteral diseases are often associated with gastrointestinal symptoms. In this communication, we studied the effect of renal pelvic or ureteric distension on the anorectal function in 12 healthy volunteers. A 3F balloon-tipped catheter was introduced into the renal pelvis. The balloon was filled with saline in increments of 2 ml up to 12 ml and the pressure response of the rectum and anal canal was recorded. Balloon filling was performed twice: rapidly (1 ml/sec) and slowly (1 ml/min). The test was repeated in the ureter with balloon fillings in increments of 0.25 ml up to 1 ml. The electromyographic (EMG) response of the external anal sphincter to distension of the renal pelvis or ureter was evaluated. The pressure response of the rectum, anal canal and external anal sphincter to distension of the anesthetised renal pelvis or ureter was then determined. The test was repeated after external anal sphincter anaesthetisation. Rapid renal pelvic or ureteric distension increased the anal canal pressure (p < 0.05) but did not change the rectal pressure (p > 0.05). With 10 and 12 ml rapid renal pelvis distension and with 0.75 and 1 ml rapid ureteric distension, the EMG activity of the external anal sphincter increased and was accompanied with loin and anal pain. Slow renal pelvic or ureteric distension caused no significant change in the anal or rectal pressures (p > 0.05) or in the EMG activity of the external anal sphincter and no anal pain was perceived. Distension of the anesthetised renal pelvis or ureter effected no changes in anal or rectal pressures (p > 0.05). The anesthetised external anal sphincter as well as the anal or rectal pressure did not respond to renal pelvis or ureteric distension. In conclusion, rapid renal pelvic or ureteric distension stimulates the mechanoreceptors in the renal pelvis or ureteric wall leading to reflex external anal sphincter contraction. This leads to elevation of the anal canal pressure. The findings suggest the possible involvement of a "reno-anal reflex" which is evoked on rapid renal pelvis or ureteric distension. Slow distension does not seem to trigger such a reflex.