Up to two-thirds of all people with MS complain of bowel dysfunction, frequently in combination with bladder problems. The most common symptoms are constipation and faecal incontinence, which frequently coexist. Understanding of the underlying pathophysiologic mechanisms is limited, and little if any evaluation of management strategies has taken place. Possible mechanisms resulting in constipation include slow colonic transit time, abnormal rectal function, and intussusception; incontinence may result from absent or decreased sensation of rectal filling, poor voluntary contraction of the anal sphincter–pelvic floor, or reduced rectal compliance. Factors unrelated to MS such as obstetric injury to the anal sphincters may also play a role. There are no published studies on the effect of medication on bowel symptoms in MS. Most patients try laxatives and enemas before reporting constipation. Increased dietary fibre or bulk laxatives such as lactulose may be helpful in mild constipation but are unlikely to be of benefit for severe symptoms. Stimulant or osmotic laxatives such as senna and bisacodyl may be useful. Establishing a bowel programme is often advocated, although without supportive evidence.

When symptoms of faecal incontinence are mild, infrequent, and not due to impaction with overflow, treatment with loperamide or codeine phosphate may be effective, although these agents must be used with caution if incontinence coexists with constipation. An enema given in the morning may reduce the risk of incontinence during the day.

Evidence-based guidelines have recently been published by the MSCCPG and form the basis for much, although not all, of the content of this section.

In the view of the Committee, bowel dysfunction in patients with MS remains difficult to manage, with little evidence-based guidance.