Clinical and physiological findings, and possible aetiological factors of rectal hyposensitivity

Background: Rectal hyposensitivity (RH) relates to insensitivity of the rectum on anorectal physiological investigation and appears common in functional bowel disorders. The clinical significance of this physiological abnormality is unclear. Method: RH was defined as one or more sensory threshold volumes raised beyond the normal range (mean plus two standard deviations) on rectal balloon distension. Clinical information and results of other anorectal physiological investigations were evaluated in 261 patients with RH. Results: Patients with RH most commonly presented with constipation (48 per cent), constipation and incontinence in combination (27 per cent), or faecal incontinence (20 per cent). Thirty-eight per cent of patients had a history of previous pelvic surgery, 22 per cent a history of anal surgery and 13 per cent a history of spinal trauma. In patients with RH presenting with symptoms of constipation or incontinence, impaired rectal sensation was the only abnormality on physiological investigation in 48 per cent and 31 per cent respectively. Conclusion: Patients with RH display marked heterogeneity in terms of presenting symptoms. The exact causes of RH are unknown, but there is evidence to suggest that pelvic nerve injury and spinal trauma are possible aetiological factors. RH appears important in the aetiology of both constipation and faecal incontinence, and may be useful as a predictor of surgical outcome.