Constipation. Pathogenesis and management.

Abstract

Constipation is a collective term for different manifestations of different aetiology, pathology and treatment. It can be a symptom of organic disease or may disclose a colonic or anorectal functional disorder of unknown aetiology--this is called chronic idiopathic constipation (CIC). CIC could be due to colonic or anorectal dysmotility. The latter presents as rectal inertia or outlet obstruction. Outlet obstruction manifests with excessive straining (strainodynia), although stools are soft and bulky. Four types of strainodynia can be identified: band, sphincter, levator and detrusor. Idiopathic infrequent defecation (oligofaecorrhoea) is revealed by hypertrophy and degenerated nerve plexus of the internal anal sphincter. It presents clinically with 'cone anus'. The 'mass squeeze contraction' theory describes rectal motility; the wave starts at the rectosigmoid junction (RSJ) and spreads distally. A 'pacemaker' was suggested to exist at the RSJ, organising rectal motility. Indeed, studies on electromechanical rectal activity revealed pacesetter and action potentials originating at the RSJ. Faecoflowmetry and water enema tests are new methods for investigating anorectal dysmotility, and reflexometry is important in assessment. The treatment of CIC is problematic and controversial. However, the patient should be given the chance to try pharmacological treatment at the start before embarking on surgery. Biofeedback may be helpful, especially in outlet obstruction constipation. Sphincter myotomy and myectomy, partial rectal resection and colectomy have been used, with variable results. Medical treatment with a fibre-rich diet or orally or rectally administered laxative agents may be indicated in the treatment of constipation, especially when a cause can not be identified. However, it is important to stress that the untoward effects which may result from laxative abuse could be greater than those of constipation.