Utility of a combined test of anorectal manometry, electromyography, and sensation in determining the mechanism of 'idiopathic' faecal incontinence

Abstract

Combined tests of anorectal manometry, sphincter electromyography and rectal sensation were carried out in 302 patients with faecal incontinence (235 women, 67 men). The results obtained were compared with 65 normal subjects (35 women, 30 men). A mechanism for incontinence was identified in all and the majority of patients had more than one abnormality. Two hundred and seventy eight patients (92%) had a weak external anal sphincter, 185 of these (67%, mostly women) also showed abnormal perineal descent, and 14 women showed clinical evidence of sphincter damage as a result of obstetric trauma. Ten per cent of patients with impaired external anal sphincter contraction showed associated evidence of spinal disease (impaired rectal sensation plus attenuated or enhanced reflex external anal sphincter activity). Unlike the other groups, the 'spinal' group contained equal numbers of men and women. Ninety seven patients (32%) had evidence of a weak internal anal sphincter. The external sphincter was also very weak and 92% of these patients also had perineal descent. Eighty two patients (27%) showed an unstable internal sphincter, characterised by prolonged 'spontaneous' anal relaxation under resting conditions and an abnormal reduction in anal pressure after conscious contraction of the sphincter or an increase in intraabdominal pressure. One hundred and forty two patients (47%) had a hypersensitive rectum associated with enhanced anorectal responses to rectal distension. All these patients had an abnormally weak external sphincter, suggesting that the hypersensitive or 'irritable' rectum should not be regarded as a cause of faecal incontinence unless accompanied by external sphincter weakness. Twenty four patients (8%) showed a normal basal and squeeze pressures and impaired rectal sensation; six showed giant rectal contractions during rectal distension. The results show that idiopathic faecal incontinence is not caused by a single abnormality, and it is suggested that combined anorectal manometry, electromyography, and sensory testing is a useful technique to identify the causes of faecal incontinence and provide a basis for appropriate treatment.