Secondary Condition: Bowel Management

Spinal Cord Injury Secondary Condition: Bowel Management

Anatomy
The gastrointestinal tract, also called the GI tract, is a continuous tube which includes the mouth, esophagus, stomach, small intestine, large intestine (bowel), rectum and anus. Its function is to store food and absorbed nutrients from the food we eat.

The gastrointestinal tract is controlled by two nervous systems, the enteric nervous system and the autonomic nervous system. The enteric nervous system is unique to the gastrointestinal tract and is further divided into the myenteric plexus and the Meissner plexus.

The myenteric plexus is located between two layers of the muscles that exist in the gastrointestinal tract, a layer that travels parallel to the intestine and a circular layer that is positioned perpendicularly. It functions involuntarily without input from the brain. The myenteric plexus is responsible for sustained (tonic) contractions that give tone to the gastrointestinal tract and rhythmic (intermittent) contractions.

The Meissner plexus is located in the submucosa (an inner layer of the bowel) and is responsible for absorption of nutrients.

Normal bowel function before a spinal cord injury
Food enters the mouth and travels down the esophagus to the stomach. The stomach then produces enzymes and hydrochloric acid to help break down the food content. The food then travels into the small intestine and eventually the large intestine. During this time the nutrients of the food are continuously being absorbed while waste products are being continuously moved through the gastrointestinal tract towards the rectum and anal canal. The muscular layers of the gastrointestinal tract move the food material by a process called peristalsis. In the anal canal there is an internal and an external sphincter. The internal anal sphincter is under involuntary control and is continuously contracted (tight) at all times. The external anal sphincter is under voluntary control and receives its nerve supply from the pudendal nerve, which comes from the spinal cord levels S2-S4. When stool enters the rectum it causes a reflex relaxation of the internal anal sphincter. Individuals then have the urge to defecate or have a bowel movement. It is at this time that the external anal sphincter is required to prevent stool from exiting the body until in an appropriate location.

Bowel function after a spinal cord injury
The enteric nervous system continues to function normally after a spinal cord injury. Therefore, food material is normally moved along the gastrointestinal tract from the mouth to the rectum. The voluntary control of the external anal sphincter is lost, however. The amount of tone in the external anal sphincter is dependent on the specific level of spinal cord injury. Individuals who have a spinal cord injury at T12 or above have a bowel that is described as an upper motor neuron bowel and the anal sphincter is spastic (continuously contracted and tight). Individuals who have a spinal cord injury at L1 or below have a bowel that is described as a lower motor neuron bowel and the anal sphincter is flaccid (loose without tone).

Management of bowel function after spinal cord injury
After a spinal cord injury, bowel function is referred to as a neurogenic bowel by healthcare professionals. This term infers that an injury to the nervous system has occurred and the bowel does not function as it normally should. The overall management of bowel function is referred to as a bowel program and takes into consideration all aspects such as diet, timing, medications and physical interventions. The goal of a successful bowel program is to prevent incontinence (accidents) of bowel movements.

Bowel continence is an appropriate and possible goal. The bowel is a remarkable organ that can be trained to empty (have a bowel movement) only when stimulated and to maintain continence at all other times outside of the bowel program time. Initially when starting a bowel program training schedule, the frequency should be every day at the same time if possible. Once a bowel program has been established without any occurrence of bowel accidents, then the individual may choose to perform a bowel program every other day. In fact, bowel function and defecation timing can be so well-trained that individuals can change the timing and days to fit their convenience. For example, an individual may be on an every-other-day bowel program but for reasons of convenience may need to have it not involve a bowel program on a certain day. In this case the individual may perform the bowel program two days in a row so that the third day can be a day that does not include a bowel program. In addition, it may be convenient for someone to change from a morning to an evening bowel program one day of the week. This type of variation in timing of the bowel program can occur once the bowel has been adequately trained with continual demonstration of continence.
 
Establishing a bowel program for the upper motor neuron bowel (Reflexive):
Initially after a spinal cord injury the bowel is experiencing spinal shock and no reflex activity is present. Therefore, the responsiveness of the bowel program will be limited during this time with the upper motor neuron bowel because it depends on reflex activity. Once spinal shock has resolved, the training process can begin during rehabilitation.

Below, several interventions of a bowel program are mentioned and described. All of the interventions are not usually used by one person and will vary depending on the response of the bowel program and consistency of the stool.

Digital stimulation
The main stimulus used in individuals with an upper motor neuron bowel program is digital stimulation. Digital stimulation involves the insertion of a well lubricated gloved finger into the rectum followed by circular motions which relaxes the external anal sphincter and stimulates the bowel to contract. Digital stimulation is usually performed for 15 to 20 seconds every 5 to 10 minutes for the duration of the bowel program. A bowel program should take no longer than 30 minutes to one hour from start to finish. Individuals who cannot physically perform their own digital stimulation will either depend on a caregiver or a plastic digital device (Royal Grip) for individuals with limited finger extension and strength.

Stool Softeners
These agents act in the GI tract to emulsify fat and to keep water in the bowel and
maintain a soft consistency of stool which helps to prevent constipation and obstruction. Examples of stool softeners used are docusate sodium (Colace) and docusate calcium (Surfak). These agents do depend on adequate fluid intake for them to be effective.
  
Bulk-Formers
Bulk-formers are usually some type of fiber agents and act to  increase the water content within the stool and increase the volume within the bowel. This increased volume of stool causes distention of the bowel which stimulates peristalsis. Examples of bulk formers include Metamucil, Fibercon, Fiberall and Citrucel. It is important to remember that when using these fiber bulk-formers, an adequate amount of fluid must be consumed or significant constipation or obstruction may occur. This can become a serious problem if individuals are being fluid restricted while attempting to perform self-intermittent catheterization. In this situation, it is probably beneficial to avoid fiber bulk-formers with an upper motor neuron bowel to prevent constipation.

Bowel Stimulants
These agents function to increase the degree of peristalsis (gut movement) and decrease the time of food movement through the gastrointestinal tract.

Senna (Senokot) is a commonly used medication for upper motor neuron bowel. It stimulates the myenteric plexus which increases the peristalsis of the colon. It takes approximately 6 to 12 hours to stimulate peristalsis after it is taken orally. Therefore, it is usually taken six to 12 hours before a planned bowel program to maximize results. Metoclopramide (Reglan) acts to stimulate the bowel to contract and improves emptying. It is sometimes used for individuals who are suffering from nausea.

Bowel Contact Irritants
Contact irritants are suppositories that caused irritation of the bowel wall when placed in the rectum. This irritation of the rectum then leads to an increase in peristalsis of the colon. When these suppositories are placed in the rectum it is crucial to make sure that they are placed up against the wall of the bowel and not in stool that may be in the rectal vault. The most commonly used suppositories are the bisacodyl suppositories, which include Dulcolax and the Magic Bullet. In both of these suppositories, bisacodyl is the active ingredient (the chemical that does the work), although the other supporting chemicals that act as the vehicle are very different and determine the time to action or contraction of the bowel. The Dulcolax suppository is bisacodyl dissolved in a vegetable oil-base which requires body heat to dissolve. Therefore, this can take up to 20 minutes to even begin to dissolve before the bisacodyl medicine can begin to contact the wall of the bowel. It is also possible that because this is an oil base, it is more difficult to flush out during the bowel program and bowel incontinence may occur later because of continued presence of this bisacodyl medication. The Magic Bullet suppository is bisacodyl dissolved in polyethylene glycol, which is water-soluble. Given the environment of the bowel, the water soluble suppository begins to dissolve within three minutes. This has been shown in a study to decrease the bowel program time by 50%. Although not proven, it has been suggested that less “late” accidents may occur because the water soluble compound is more easily flushed out of the bowel during the bowel program which prevents bisacodyl from stimulating the bowel at a later time.

Laxatives
Laxatives are taken orally and act to drawl fluid into the small intestine which stimulates the contraction of the intestine. Examples of laxatives are milk of magnesium, magnesium citrate, Fleets phosphosoda, Miralax, Golytely and Lactulose.

Enemas
Enemas can be used as a last attempt to treat constipation and prevent bowel impaction. Various enemas are available, and a common choice is the Fleets enema. Other larger volume enemas are sometimes used. Enemas should be avoided if possible and used as a last effort.
 
Establishing a bowel program for the lower motor neuron bowel (Areflexive) :

Areflexive bowels usually occur with individuals who have a spinal cord injury at or below L1. Individuals with a lower motor neuron bowel do not have the reflex activity that responds to the above measures listed for the upper motor neuron bowel. Therefore the method of management usually requires self-disimpaction, in which an individual with a gloved finger reaches into the rectal vault and manually removes stool. It is often recommended that the bowel program takes place daily to prevent incontinence since it does not respond reflexively and the rectal sphincter is without tone.

It is also more important to maintain an appropriate consistency of stool texture with various stool softeners and bulk-forming agents as described above. Contact irritants and digital stimulation are ineffective because of the lack of reflex. Bowel continence is more difficult but can be accomplished with the appropriate management.