Constipation means having infrequent bowel movements, hard stools, or difficulty passing stool. In MS, the causes often fall into two broad categories: direct effects of nerve damage and indirect effects of living with the disease.
Neurogenic Bowel Dysfunction
The main cause of constipation in MS is the former — the development of neurogenic bowel dysfunction, says Vargas.
This is caused by demyelination in nerves that help with the function of gut control. As a result, the colon moves stool more slowly, the muscles of the pelvic floor may not work correctly, and it can become difficult to fully empty the bowels, she says.
Constipation is also often linked with bladder problems, since both systems share some of the same nerve pathways, says Vargas.
This can mean:
- Not recognizing when you need to have a bowel movement
- Difficulty coordinating the muscles that move stool through the colon
- Weaker signals triggering healthy contractions of the bowel
Reduced Mobility and Physical Activity
Physical activity plays an important role in bowel health and is frequently reduced in individuals with MS, especially in progressive forms, says Erin Wilkinson, a nurse practitioner at the Mellen Program for MS at Cleveland Clinic Nevada.
“Slow or difficult mobility, which becomes more common in progressive MS, reduces the natural intestinal movement (motility) that helps stool move through the colon.
Low Fluid Intake
Hydration is essential to minimize constipation, but many people with MS limit fluid intake to avoid urinary urgency, frequency, or incontinence, particularly those with neurogenic bladder, says Wilkinson.
When fluid intake is low, the colon absorbs more water from the stool, leading to harder, drier stools that are more difficult to pass.
Low Fiber Intake
A diet low in fiber is known to be a contributor to constipation. “Fiber, particularly soluble fiber, absorbs water to help form soft, bulky stool, which is easier to move through the colon,” says Wilkinson.
People not eating enough fiber are likely to have smaller stool volume, slower colonic transit, and increased straining.
Medication Side Effects
There are a number of medications that are commonly used in MS that will make constipation worse, says Vargas.
- Anticholinergics like oxybutynin which is prescribed for bladder symptoms
- Antidepressants like amitriptyline, commonly used for nerve-related pain
- Some antispasmodics like hyoscyamine
- Opioids when prescribed for pain control
- Iron supplements to help with anemia
“Careful review of medication regimens is essential when managing constipation in MS,” she says. But if you suspect a medication is contributing to your bowel issues, talk with your provider — don’t stop taking it without consulting them first.
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