Rectourethral reflex: description of a reflex and its clinical significance. A preliminary report

The present communication studies the technique and clinical significance of a new reflex which I called 'rectourethral reflex'. The study comprised 29 subjects with normal anorectal and urinary functions. The procedure consisted of inflating the rectum with a balloon connected to the distal part of a catheter. The electromyographic activity of the external urethral sphincter was recorded using a concentric needle electrode inserted into the muscle. The procedure was repeated in 10 patients after muscle infiltration with Xylocaine or saline. Rectal distension evoked external urethral sphincter contraction in all the subjects. The amplitude of motor action potentials increased with increasing rectal distension. Anesthetized muscles did not respond, while saline-infiltrated muscles responded. The latency of the reflex decreased with increasing volume of rectal inflation. The reflex harmonizes the relation between defecation and micturition. It guards against involuntary micturition when the rectal detrusor is distended. Changes in amplitude and latency of the reflex may be significant in assessing rectourinary disorders. The reflex could thus be used as an investigative tool in the diagnosis of such disorders.