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Your bowel and spinal cord injury Tools

Your bowel after a spinal cord injury

Bowel function after a spinal cord injury

Bowel processes change after a spinal cord injury. Bowel emptying will no longer be under your voluntary control. When the function of the bowel has been disrupted due to changes in the nervous system, it will be known as a neurogenic bowel.

There are two types of bowel function depending on what sort of spinal cord injury you have:

  • reflex or upper motor neuron bowel
  • flaccid or lower motor neuron bowel

What causes a neurogenic bowel?

Nervous system changes can occur as the result of:

  • spinal cord injury
  • spinal cord disease
  • damage to nerves leading to and from the bowel
  • brain trauma

What is the reflex, or upper motor neuron (UMN) bowel?

If you have a spinal cord injury that leaves the conus medullaris intact, or unaffected, your spinal and autonomic nerves at S2, S3 and S4 levels of the spinal cord remain intact. Reflex activity will continue to occur between the smooth muscle of the rectum, the internal and external anal sphincters and the spinal cord.

If you have a reflex bowel

If you have a reflex bowel you will find that:

  • smooth muscle activity in your rectum is increased, which means it will contract more frequently
  • your sacral nerve reflexes are intact and are activated in response to the rectum filling, and stretch receptors also continue to work
  • muscle tone in your external anal sphincter is increased, sometimes to very high levels.

These reflexes can be useful in helping you to manage your bowel, and can help you establish reliable bowel emptying habits. Good bowel habits mean you have greater control over when and where your bowel is emptied, minimising the risk of complications and accidents.

What is the flaccid, or lower motor neuron (LMN) bowel?

If you have a spinal cord injury at or below your conus medullaris, nerves involved with bowel function are damaged. Sometimes when there is a lack of blood supply to any levels of your spinal cord it can cause the entire length of your spinal cord, including your conus medullaris, to be damaged.

This type of injury causes damage to either your spinal and autonomic nerves in the S2, S3 and S4 levels of your spinal cord, or nerves in your cauda equina. This means that you no longer have any reflex activity between your rectum, anal canal, internal and external anal sphincters, and your spinal cord.

If you have a flaccid bowel

If you have a flaccid bowel, you will find that:

  • smooth muscle activity in the rectum and anal canal is absent, and your bowel is in a flaccid or toneless state
  • no nerve reflexes are activated as the rectum fills
  • there is no muscle tone in the external anal sphincter