The cutaneo-urethral reflex. Description of the reflex and its role in stress urinary incontinence

Abstract

The present communication describes the “cutaneo-urethral reflex” and its clinical significance. The study comprised 39 healthy volunteers and 14 patients with urinary stress incontinence. The periurethral skin was stimulated by pencil electrode and the EMG activity of the external urethral sphincter was recorded by concentric needle electrode inserted into the sphincter. The external urethral sphincter basal activity was increased with periurethral skin stimulation. The reflex response was absent when the external urethral sphincter or the periurethral skin were anesthetized. The recording of the cutaneo-urethral reflex in 14 urinary stress incontinent patients showed absence of reflex in 4 patients and weak activity in 10. These results suggest a weak external urethral sphincter in stress incontinence. Together with the absent or weak straining urethral reflex, it is believed that urinary stress incontinence is due to weak external urethral sphincter contraction on coughing; intra-urethral pressure, on coughing, is not elevated enough to be above the intravesical pressure, with a resulting urinary leak. EMG recording of the urethral reflex may thus prove valuable in the diagnosis of control urinary disorders and can be included as an investigative tool in such disorders.