Multiple Sclerosis and Bowel Problems
When you have multiple sclerosis (MS), you may be bothered by problems with bowel or bladder control. Like bladder control, bowel control depends on a healthy nervous system in which nerve signals flow smoothly between your gastrointestinal tract, spinal cord, and brain.
Here’s how the bowel system is supposed to work:
The stomach partially digests the food you eat and then sends it to the small intestine, which in turn sends it, with slow, propulsive movements, to the large intestine.
After it makes its way to the large intestine, the food passes through four sections, the last of which is called the sigmoid colon, where the fluids are absorbed and a solid mass is formed.
When the mass moves from the sigmoid colon into the rectum, you feel the urge to have a bowel movement.
After the rectum has filled, nerve endings in the rectal wall send messages to the spinal cord, which signals the internal sphincter (which is normally closed) to open, allowing the mass to pass through the anal canal.
The internal sphincter is controlled by the spinal cord, which means you don’t have conscious control over it. The external sphincter (which is also part of the anal canal) is controlled jointly by the spinal cord and brain, which gives you the control to decide when and where to take care of business.
When your various parts can’t talk to each other, as is sometimes the case with MS, normal bowel activities can get messed up, and that’s when you need to contact your neurologist or nurse. The most common problem is constipation. Diarrhea and incontinence occur much less frequently.
Constipation, which is defined as infrequent (compared to your usual habits) or difficult (painful or hard to pass) bowel movements, is caused by the following factors:
Demyelination in the areas of the brain and spinal cord that control bowel function: This demyelination can slow the process to the point that too much fluid is withdrawn from the stool. The result is a hard, dry mass that’s difficult and sometimes painful for you to pass.
Symptoms that limit your mobility: Symptoms such as weakness, fatigue, or stiffness slow bowel activity, which results in a dry, hard stool.
Limited fluid intake: When you stop drinking fluids in an effort to manage your bladder problems, you deprive your body of the fluids it needs to function properly. To make up for this, your body absorbs more fluid from the stool as it passes through your system. The result, again, is a hard stool that’s difficult to pass.
Some medications: Certain medications, particularly those used to treat bladder problems, may slow bowel activity and result in — you guessed it — a hard stool that’s difficult to pass.
Diarrhea (loose watery stools) is actually uncommon in MS. If you experience this kind of change, you and your doctor should be looking for a different cause. What sometimes happens in MS, however, is that moist stool from higher up in the colon leaks out around hardened stool that’s trapped in your rectum. In other words, the real problem is constipation rather than diarrhea.
Loss of bowel control can also occur in MS when your brain doesn’t receive the necessary signals telling you that you need to go. Fortunately, this problem is pretty rare, and the same strategies discussed in the following section will also help you avoid unpleasant accidents.