Multiple sclerosis results from the body's immune system mistakenly attacking nerves in its own brain and spinal cord. This damage to the central nervous system results in a progressively debilitating disease. Multiple sclerosis may cause many different types of symptoms, depending on the exact location of the nerves that are damaged. When nerves controlling the bowels are damaged, normal functioning may be disrupted.
Constipation
Roughly 70 percent of patients with multiple sclerosis experience constipation as a result of their disease, reports the Bladder and Bowel Foundation. This constipation may be caused by several different factors. In some cases, the nerves that control the bowels are damaged by multiple sclerosis, preventing the brain from coordinating all the muscle movements needed to pass stool through the bowels. In addition, when the bowels are full, they normally send a signal to the brain indicating that they need to be emptied. However, in patients with multiple sclerosis, this signal may not reach the brain, because of the damaged nerves. As a result, the patient may not realize the bowels need to be emptied, and the longer stool sits in the bowels without moving, the more difficult it becomes to move the stool, explains the National Multiple Sclerosis Society.
Additional Causes of Constipation
Multiple sclerosis patients often are exposed to other factors, which further increase the risk of constipation. For example, multiple sclerosis often causes muscle weakness and coordination problems, which limits physical exercise and further reduces bowel mobility. Additionally, patients with multiple sclerosis often tend to reduce their fluid intake, in order to reduce the chance of bladder incontinence. However, reducing fluid intake slows down gastric motility and raises the risk of constipation, the Bladder and Bowel Foundation explains. Constipation, in turn, can increase the risk of bladder control problems. Finally, some of the medications used to treat the symptoms of multiple sclerosis increase the risk of constipation.
Diarrhea
Diarrhea usually occurs less frequently in patients with multiple sclerosis compared to constipation, but it can present a problem on some occasions. If a patient has damage to the sensory nerves of the rectum, and cannot feel when the bowels need to be emptied, sometimes the rectum becomes so full that an involuntary relaxation of the anal sphincter is triggered, resulting in an unexpected release of stool, the National Multiple Sclerosis Society reports. In other cases, the damaged nerves controlling the function of the bowels cause the bowels to become overactive, passing stool through too quickly and resulting in diarrhea.
Impaction
In rare cases, constipation may result in a condition known as impaction, in which a solid mass of stool becomes lodged in the rectum and cannot be passed, explains the National Multiple Sclerosis Society. Impaction is a serious condition that requires immediate medical attention. Diarrhea may be caused by impaction if the impacted stool mass pushes against the anal sphincter, causing it to relax and allowing watery stool to leak around the impacted mass and out of the anus.
