Idiopathic constipation associated with impaired urethrovesical and sacral reflex function

Sixteen chronically constipated women (age range 20-66 years) and 29 healthy control subjects (age range 22-53 years) underwent neurophysiological assessment of the integrity of pelvic spinal reflexes. The results were compared with videourodynamic studies and multiport anorectal manometry combined with external anal sphincter electromyography. The neurophysiological assessment consisted of electrical stimulation of the dorsogenital nerve, while recording any evoked reflex activity in the external anal and urethral sphincters with concentric needle and surface electrodes. Of these constipated women, 75 per cent had absence of one or more evoked sacral reflexes (compared with 20 per cent of healthy controls, P less than 0.05). Sensory thresholds and motor unit potentials in the external anal sphincter were similar in healthy and constipated women. Nine (56 per cent) constipated women displayed urodynamic abnormalities (increased bladder capacity, acontractile bladder and genuine stress incontinence). Only 38 per cent of constipated women perceived a desire to defaecate during rectal distension with up to 100 ml, compared with 95 per cent of normal subjects (P less than 0.0005). Moreover, 73 per cent of constipated women did not relax the external anal sphincter during defaecation, compared with 12 per cent of controls (P = 0.001). Taking into account the possible significance of our data in relation to previous findings it is suggested that the integration of sensory information within the sacral cord may be impaired in chronic idiopathic constipation.