Managing the Bowel Problems that Accompany MS
Denise I. Campagnolo MD, MS–Director Clinical Multiple Sclerosis Research, Barrow Neurological Institute,
Multiple sclerosis (MS) changes the way your body works and potentially affects how you care for yourself and carry on daily life. One important change has to do with bowel function. This change is often difficult for many of us to talk about and this silence further compounds the problem.
Before developing MS, people do not typically need to make special plans or schedules for bowel movements. They have the freedom to feel the need to use a toilet, hold their bowels until the time is right, and then relax and let stool pass at the right place. With MS, however, bowel movements may require more time, thought, and planning. For instance, people with MS are sometimes unable to feel when stool is ready to pass and need assistance expelling it.
Symptoms of MS change over time. Even if you have adhered to a regular bowel program for months or years, over time it may stop working for you as well as it once did because of the changes your MS has undergone. Under these circumstances, it would be necessary to make modifications to your regular program. A well-designed bowel program can help you lead a healthier and happier life with MS. The goals of a well-designed bowel program are to:
-Help prevent unplanned bowel movements (also called bowel accidents, incontinence, or involuntaries).
-Help avoid physical problems such as constipation.
-Put you back in control of a bodily function that, if neglected, can not only cause embarrassment, but potentially damage the bowel.
-Improve your confidence in work and social situations.
The Structure and Function of the Gastrointestinal Tract
The gastrointestinal tract (GI tract) is the tube that runs from the mouth to the anus and is responsible for transport, digestion, absorption, and eventual elimination of the food we eat. This tube is divided into several segments that are quite specialized in their structure and function. These segments are the esophagus, the stomach, the small and large intestine, and the rectum.
After passing through the mouth, the first section of the GI tract encountered is the esophagus. The esophagus has a muscular wall that allows for passage of food into the stomach. The actions of the esophagus are all controlled by involuntary muscle activity which means that they occur without you being conscious of them. The esophagus moves food to the next major area, the stomach. The stomach is responsible for holding ingested food, mixing it with gastric acids that reduce the solids to smaller particles, and regulating the passage of these small bits into the first part of the small intestine called the duodenum. The small intestine, pancreas, and liver work together to digest and absorb all of the nutrients from the food we eat. The involuntary muscle contractions in the small intestinal wall are called peristalsis and move the liquid contents of the small intestine along. Once the liquid stool reaches the large intestine (colon), the process of absorption of water and electrolytes (i.e., sodium chloride, etc.) from the stool begins. This absorption process is the primary function of the right side/ascending and transverse colon. Storage is the main purpose of the left side/descending colon.
Normally when having a bowel movement, colonic contractions (called haustrations or mass movements) cause the stool to move from the left/descending colon into the rectum. This movement of stool into the rectum stretches the rectum which provides the stimulus or signal that causes automatic and involuntary relaxation of the internal anal sphincter. This filling of the rectum also provides us the knowledge or urge to defecate. No stool will leave the body, however, until the external anal sphincter and pelvic muscle (called the puborectalis) have relaxed. (Steins, Bergman, and Goetz, 1997) These muscles are under our voluntary control and we command them to stay contracted until we are in the appropriate place and time. When these criteria have been met, we relax, thus relaxing the external anal sphincter and puborectalis muscle. This allows passage of stool out of the body.
Changes to the System Caused by MS
The bowel has two control mechanisms that are intrinsic to its wall. The first is called the enteric nervous system which is made up of nerves within the multi-layered bowel wall. The second are the neurotransmitters. Neurotransmitters are essentially chemical messengers that are released within the bowel and excite this enteric nervous system. Neither of these control systems is affected by neurological conditions such as MS. Damage to the spinal cord however, whether from MS or traumatic causes, does affect the motility of the gastrointestinal tract at certain key areas.
Gastric or stomach motility is generally slowed with severe damage to the upper segment of the spinal cord. Typically speaking, mild cord damage does not affect motility quite as much. The right side of the colon (descending colon) is also affected by damage to the spinal cord. The result is slowed colonic transport, which allows greater than usual amounts of water to be absorbed from stool, which â€œsets the stageâ€ for constipation. Further complicating matters, the external anal sphincter, which as we said before is a voluntary muscle, will often suffer from spasticity as does any other striated muscle in the body. The result is difficulty with relaxation of the external anal sphincter, which increases the likelihood of constipation and fecal impaction (stool that the body is unable to evacuate on its own). This pattern of slowed motility, constipation, and potential fecal impaction, is a pattern referred to as â€œupper motor neuron bowelâ€ and is the most common pattern clinicians see after MS has caused damage to the upperthoracic (back) or cervical (neck) areas of the spinal cord. Different patterns are seen if the lower part of the spinal cord or lumbosacral nerve roots are damaged, which are NOT common in MS, therefore we will not be addressing them here.
We must take into account other considerations that may contribute to these difficulties. The first is that medication that we take for other reasons sometimes affects the bowel. A good example is narcotic medications taken for pain. These will tend to worsen this constipation pattern by further slowing colonic transport and decreasing the urge to defecate. Also, physical conditions such as weak abdominal musculature will potentially worsen the slowed motility. This condition contributes to the difficulty in the loss of the â€œassistâ€ that we get by contracting our abdominals during defecation. Lastly, immobility, not exercising, sitting for many hours in the day, and poor diet all contribute to worsened constipation. So optimizing diet with high fiber content and plenty of daytime water drinking, keeping as physically active as possible, and medication choices that avoid narcotics when possible are ways to prevent or minimize this problem.
Bowel Management Strategies
Strategies to successfully manage this upper motor neuron bowel pattern described above include both pharmacologic agents (drugs) and physical or mechanical maneuvers. We will call these incorporated strategies a “bowel program”. Each bowel program needs to be tailored to the individual needs of the person using it. Bowel medications are usually an essential part of a good bowel program. There are different categories of bowel medications and each category functions in a specific manner (see Tables 1 and 2). Oftentimes, combinations of bowel medications from different categories can be taken together to achieve the desired goal.
The first category of bowel medications is stool softeners. As stated above, slowed motility allows for more than the ordinary amount of water to be absorbed from stool while it sits in the colon, which may leave the stool insufficiently soft. We want stool be formed, yet soft, to aid in easy evacuation. Therefore, it is often useful to add oral medications to the bowel program that will soften the stool. The most commonly used is that of preparations of docusate with sodium or calcium. Docusate acts on the surface of the interior of the bowel to decrease reabsorption of water and to mix fat globules into a milky, soluble fluid. Both of these functions serve to increase water content of stool, thus keeping it soft. Stool softeners only work if a person’s oral fluid intake is sufficient so it is important that you drink plenty of water while on this medication. Stool softeners are not stimulants or laxatives and therefore do not hasten colonic peristalsis or increase transit time. A laxative can be used together with a stool softener to achieve the desired results. For example, casanthranol can be added to docusate sodium for a stool softener-laxative combination product.
The next general category is bulk-forming agents. These work, as the name suggests, by adding bulk to stool. With increased bulk, the bowel diameter increases and results in producing a neural signal to increase peristalsis and motility. Typically, these are natural vegetable fiber medications. It is very important to drink extra fluids when you take these. Overuse of these agents will cause diarrhea.
Another category is the peristaltic stimulants and prokinetic agents. These directly increase peristalsis and motility by direct stimulation of the nerves in the multilayer bowel wall. The natural plant, senna, is a commonly used oral peristaltic stimulant. This medication, once taken and absorbed, stimulates the enteric nerves of the bowel wall in about 6 to 12 hours, so it is best taken in the morning if you desire a bowel movement (BM) that night. The same thought process applies in the reverse. If you want to have a BM in morning, take it at bedtime. Consequences of taking senna long-term are staining of the inside of the colon wall, called melanosis coli, and weakened dilated bowel wall. Melanosis coli can be seen on colonoscopy, but is quite inconsequential.
A specific subclass of peristaltic stimulants, called contact irritants, increases peristalsis by direct irritation (contact) with the lining of the colon. These work very differently from senna, which needs to be absorbed. The contact irritants are, instead, typically placed into the rectum by way of suppository or mini enema and directly contact the colon wall to stimulate peristaltic activity by stimulating the nerves in the lining of the rectum. The most common example of a contact irritant is bisacodyl. It is available in a vegetable oil based suppository, a watersoluble based suppository, or a mini enema. There is also an oral tablet form of bisacodyl, but it is less efficient than the rectal forms. Another option is in simple glycerin suppositories. These suppositories stimulate peristalsis in the colon and help to lubricate the rectum to help pass stool. Mineral oil mini enemas will also accomplish the same result. There are a few other peristaltic stimulants and prokinetic agents currently being used, but these are beyond the scope of this review.
The last general category is the osmotic laxatives, which work by pulling water into the colon thus increasing stool bulk. Examples include lactulose, magnesium sulfate, magnesium citrate, sodium biphosphate, polyethylene glycol, and sodium phosphate. As with the stool softeners and bulk-forming agents, these medications also require intake of extra fluids. When considering osmotic laxatives though, it is important to take them only under a clinician’s care since, with the exception of polyethylene glycol, these medications can cause electrolyte disturbances in the body.
Outside of the pharmaceutical remedies, there is a physical maneuver called digital rectal stimulation that can help stimulate peristalsis. This involves inserting a gloved, well-lubricated finger gently into the rectum. The finger is moved gently in a circular fashion, keeping the finger in contact with the rectal wall. This should continue for about 20 seconds, but no longer than a minute. This is repeated every ten minutes until a bowel movement occurs. This maneuver relaxes and opens the external anal sphincter, straightens the rectum, and itself triggers stool to enter the rectum. Orienting your body in a seated or left-side lying position will also help this process. Other products such as CO2 (carbon dioxide gas) suppositories work in the same manner by inflating the rectum, thus triggering peristalsis.
A good bowel program is performed in a routine that allows for complete, predictable evacuation and strives to prevent accidents or leakage. The schedule of the bowel program needs to be adjusted to one’s lifestyle, existing habits and patterns of elimination, and availability of attendants or caregivers if needed. The actual procedures or medications administered are dependent upon the degree of constipation, the amount of neurological impairment, and previous responsiveness to agents. It is also important to note that every bowel program should initially be established under a clinician’s guidance, but thereafter can be adjusted by the person him or herself with the appropriate level of understanding and education.
There are circumstances when an effective regular bowel program simply cannot be attained. More extreme solutions do exist and have been effective for some individuals. They include elective colostomy and antegrade continence enemas (Yang and Steins, 2000). These should be discussed with your physician and would involve referral to a specialized facility.
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