Medically reviewed by Amit M. Shelat, D.O.
The symptoms of multiple sclerosis (MS) can vary from person to person and may change over time. But for nearly 70 percent of individuals with MS, symptoms include bowel problems like constipation, diarrhea, incontinence (loss of bowel control), and diverticulitis (inflammation of small pouches that form in the digestive tract). Bowel problems can result from MS’ impact on the body or from unrelated issues, including food sensitivities, lack of fiber, or dehydration.
If you have bowel problems, it’s a good idea to understand what causes them, what the symptoms are, and how you can deal with them.
What Causes Bowel Problems in MS?
MS is a chronic autoimmune disease of the central nervous system, which includes the brain and spinal cord. In people with MS, the body’s defenders (white blood cells) attack the central nervous system, causing inflammation and stripping nerves of their protective coating (myelin).
This process can disrupt signals to and from the brain and spinal cord that control bowel function, leading to what’s known as neurogenic bowel dysfunction. This type of dysfunction is common among people with MS: Researchers have found it may affect anywhere from 39 percent to 73 percent of people with the condition.
MS can also prevent the muscles of the pelvic floor from relaxing. These muscles help to eliminate waste from the body. Additionally, multiple sclerosis may block the gastrocolic reflex. This reflex, which occurs naturally after eating, helps food move through the lower digestive tract.
Constipation
Constipation is the most commonly reported bowel problem in MS. It occurs when too much water is absorbed by the body, causing stools to be hard, dry, and difficult to pass.
There are several possible causes of constipation in MS. Aside from problems with the nerve signals between the bowel and brain, constipation may result from poor dietary habits, lack of physical activity, and depression, all of which can disrupt the digestive tract. Certain MS medications may also cause or worsen constipation in some people.
Many people with multiple sclerosis have difficulties with walking (gait) and fatigue. These symptoms can slow down the movement of waste through the large intestine, leading to constipation. Having weakened abdominal muscles may also make it more difficult for a person to have a bowel movement.
Spasticity, which refers to muscle spasms and stiffness, is another common symptom of multiple sclerosis. Pelvic floor muscles that are in spasm may be difficult to relax, impacting a person’s ability to move their bowels. Some people also experience bladder problems, such as incontinence or a spastic (overactive) bladder. People may try to manage these problems by limiting the fluids they drink, which can lead to constipation.
Diarrhea
Generally speaking, diarrhea is much less common than constipation in people with MS. Diarrhea refers to soft, liquid, or watery stools, which can occur when the contents of the bowel move too quickly through the digestive tract or not enough water is removed during digestion. In some cases, MS may cause the bowel to be overactive, leading to diarrhea.
If you’ve been diagnosed with MS and experience diarrhea, it may not be related to your condition, however. Diarrhea may happen as the result of a food sensitivity, food allergy, stomach virus, or change in activity levels.
Bowel Incontinence
Bowel incontinence refers to a loss of voluntary control of the bowels. This symptom frequently accompanies diarrhea in people with MS, although it may also be caused by long-term constipation.
It is possible for people with MS to experience both constipation and incontinence or bowel leakage. Some people may alternate between the two symptoms. One MyMSTeam member said that they are usually constipated as a result of their pain medication, but when they have an attack, they “don’t have full control.”
Diverticulosis and Diverticulitis
Diverticulosis refers to the presence of small pouches or bulges on the wall of the colon (large intestine). Diverticulitis occurs when one or more of these pouches (known as diverticula) become infected or inflamed.
Diverticula can form in weak spots of the colon when constipation exerts pressure on the intestinal walls. People with MS may develop diverticulosis as a result of chronic constipation or lack of exercise. Other risk factors for diverticulosis include:
- Aging
- Smoking
- Obesity
- Taking certain medications (including steroids, opioids, or nonsteroidal anti-inflammatory drugs)
- Eating a diet low in fiber and high in animal fat
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