Bowel Problems: The Basic Facts
The bowel: what it
is, what it does
Normal bowel functioning can range from three bowel movements a day to three a week. Despite the widely recommended “one movement a day,” physicians agree that such frequency is not necessary. The medical definition of “infrequent” bowel movements is “less often than once every three days.” Most physicians agree that a movement less often than once a week is not adequate.
The rectum, the last 4–6 inches of the digestive tract, signals when a bowel movement is needed. It remains empty until just before a bowel movement. The filling of the rectum sends messages to the brain via nerves in the rectal wall that a bowel movement is needed.
From the rectum, the stool passes into the anal canal, guarded by ring-shaped internal and external sphincter muscles. Just prior to being eliminated, the stool is admitted to the anal canal by the internal sphincter muscle, which opens automatically when the rectal wall is stretched by a mass of stool. The external sphincter, on the other hand, is opened by a conscious decision of the brain, so that bowel movements can be performed only at appropriate times.
Common causes. Diarrhea and constipation are frequent companions of travelers, resulting from encounters with unfamiliar or contaminated food or water, or simply because of a change in an accustomed level of activity. Diarrhea can also be triggered by a viral, bacterial, or parasitic infection.
Continued diarrhea may also stem from food allergies or sensitivity to particular kinds of foods, such as highly spiced dishes or dairy products. (Intolerance to dairy products can often be accommodated by drinking lactose-reduced milk or by eating dairy products together with tablets containing lactose-digesting enzymes.)
Non-MS-related constipation may also be caused by common medications such as calcium supplements or antacids containing aluminum or calcium. Other drugs that may lead to constipation include antidepressants, diuretics, opiates, and antipsychotic drugs.
Ironically, one of the most common causes of non-MS-related constipation is a voluntary habit: delaying bowel movements to save time on busy days or to avoid the exertion of a trip to the bathroom. Eventually the rectum adapts to the increased bulk of stool and the urge to eliminate subsides. The constipating effects, however, continue, and elimination becomes increasingly difficult.
For some women, constipation is a premenstrual symptom, and during pregnancy it may be one way that the colon reacts to a change in the level of sex hormones.
Irritable bowel syndrome, also known as spastic colon, is an umbrella term for a number of conditions in which constipation and diarrhea alternate, accompanied by abdominal cramps and gas pains. Your doctor can determine if you have a disease or simply a syndrome associated with stress.
Constipation and MS
Common MS symptoms such as difficulty in walking and fatigue can lead to slow movement of waste material through the colon. Weakened abdominal muscles can also make the actual process of having a bowel movement more difficult.
People with MS often have problems with spasticity. If the pelvic floor muscles are spastic and unable to relax, normal bowel functioning will be affected.
Some people with MS also tend not to have the usual increase in activity in the colon following meals that propels waste toward the rectum.
And finally, some people with MS try to solve common bladder problems by reducing their fluid intake. Restricting fluids makes constipation worse. This is so common in MS that the first step to take may be to get medical help for your bladder problems so that adequate fluid intake, which is critical to bowel functions, will be possible.
A long-term delay in dealing with bowel problems is not an option. Besides the obvious discomfort of constipation, complications can develop. Stool that builds up in the rectum can put pressure on parts of the urinary system, increasing some bladder problems. A stretched rectum can send messages to the spinal cord that further interrupt bladder function. Constipation aggravates spasticity. And constipation can be the root cause of the most distressing bowel symptom, incontinence. See Incontinence section.
Copyright © National Multiple Sclerosis Society, 2004