Normal bowel function
The emptying of the bowel (defecation) is a reflex-type process, but one which you can consciously influence. If the rectum1 is sufficiently full and therefore stretched, an impulse is sent through the nerves to the defecation centre in the spinal cord. This triggers the sensation “urge to defecate” in the cerebrum. The defecation centre controls the rectum muscles and triggers the relaxation of the anal sphincter and at the same time the contraction of the outer muscles of the rectum. This moves the bowel contents outside.
A continuing contraction of the diaphragm and abdominal muscles, the so-called abdominal press, supports this process. Delaying defecation over a certain period of time is possible because the external sphincter can be contracted deliberately and therefore defecation can be avoided.
Defecation in the case of flaccid bowel paralysis
Information on the level of fullness is registered by stretch receptors on the intestinal wall. Normally, this information is forwarded via the defecation centre to the brain. But due to the injury of the spinal cord, this information does not reach the spinal cord. Defecation can therefore no longer be controlled deliberately. The intestinal wall does not transport the stool any further; the sphincter muscle is flaccid and unable to hold back the stool. As a result, incontinence frequently occurs in the case of flaccid bowel paralysis. Daily defecation is necessary to prevent incontinence.
Defecation in the case of spastic bowel paralysis
In the case of spastic paralysis, the person is no longer able to tell how full the bowel is. As a result of the lesion in the spinal cord, the information cannot be transmitted to the brain; instead, it is returned directly from the defecation centre to the defecation centre with the command “bowel full”. Defecation can no longer be controlled consciously. Due to the reflex arc, the intestinal wall transports the stool but at the same time the sphincter stays closed.
In the case of spastic bowel paralysis, the bowel can be trained so that it only needs to be emptied every other day. However, this is dependent on the defecation habits of the individual, and it will become apparent over the course of the rehabilitation whether a two-day rhythm is possible.
There are various bowel movement techniques and aids available for both forms of paralysis. Defecation is also influenced considerably by eating habits and by fluid intake.
The most important objective is to find a good rhythm to defecation in order to prevent incontinence and so as not to restrict you in your everyday activities.
1 last part at the anal opening