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Neurogenic Bowel

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Longstanding spinal conditions can cause neurogenic bowel problems, the type depending on the site of the damage.

Arachnoiditis tends to affect the nerve roots primarily rather than the spinal cord, although that can be affected secondarily in some cases.

A complete injury at the cauda equina level (lower motor neurone) would cause areflexic bowel in which no reflex peristalsis (the propulsion of the contents of the gut) occurs.

Nerves within the colon wall co-ordinate slow stool propulsion and the denervated anal sphincter has low tone. This results in a sluggish stool movement, a dryer, rounder stool, and a greater risk of faecal incontinence through the flaccid anal sphincter.

A reflexic bowel by contrast, resulting from an injury above the sacral spinal segments (Upper motor neurone) involves a sphincter, which is spastic (increased tone).

Defaecation cannot be initiated by voluntary relaxation of the sphincter. However, nerve connections between the spine and the gut are intact and there remains a reflexic co-ordination of stool propulsion.

Associated problems include:

  • Haemorrhoids
  • Abdominal distension
  • Autonomic dysreflexia
  • Difficulty with bowel evacuation
  • Poorly localised abdominal pain
  • Faecal impaction
  • Rectal bleeding
  • Constipation

Those with a lesser degree of damage may find they have some loss of rectal sensation, perhaps coupled with a visceral Hyperpathia (heightened pain, e.g. abdominal cramps with constipation).

This means that there is a delayed perception of the full rectum and that once the threshold for perception of rectal distension is reached; there is sudden, painful (often burning) urge to defaecate, which may result in incontinence.

Faecal incontinence is highly distressing. It may involve loss of control of both flatus (gas) and faeces, and there may be leakage of either. Neuropathic incontinence can arise in arachnoiditis affecting the cauda equina.

Pelvic floor denervation secondary to childbirth or as a result of spinal cord or cauda equina damage will contribute to the problem.