an acute diarrheal illness due to viral or bacterial infection; however, many patients continue to have distressing urgency resulting in considerable lifestyle impairment. Many curtail their travel and social activities outside the home for fear of fecal incontinence. The etiology is often multifactorial; however, side effects of medications that increase small bowel and colonic motility should always be considered in the workup of diarrhea in older patients. Common culprits include medications for dementia (anticholinesterase inhibitors), serotonin-antagonist antidepressants, and antiarrhythmic drugs. Small bowel overgrowth is an underdiagnosed cause of diarrhea and bloating in older patients and can result from use of medications that inhibit intestinal motility. Breath hydrogen testing and treatment with bismuth products or antibiotics should be considered in patients with unexplained diarrhea that is not related to infection or inflammatory disease. Decreased rectal compliance occurs with aging113 and may contribute to sensations of fecal urgency in these patients. Constipation Constipation can be variably described as a decrease in the frequency of defecation or as increasing difficulty with defecation. The latter is usually due to either stool that is excessively hard or functional and/or anatomic conditions that prevent normal defecation. Anorectal dyssynergy or paradoxical anal contraction or inability to relax or coordinate the pelvic floor muscles during defecation is an example of the latter; rectoceles, enteroceles, and perineal descent often are a consequence of multiparity and/or difficult deliveries. Megarectum may result from impaired sensation and can lead to fecal impaction resulting from the formation of large amounts of stool in a very compliant rectum. Medication side effects often contribute to constipation, particularly narcotics and those with anticholinergic properties. Constipation results in increased stool retention times. This may have implications for carcinogenesis, because prolonged retention of carcinogenic compounds that are ingested, or formed by metabolism of precursors, may increase the risk of colon cancer. Constipation is extremely prevalent in older patients.114 Surveys in both the United States and the United Kingdom indicate that in individuals older than 60 years, the prevalence of constipation is 12% of community-dwelling seniors, 41% of hospitalized patients, and more than 80% of patients in long-term care institutions.115 This is likely a result of multiple superimposed risk factors: the effect of normal aging on neuromuscular function in the colon, mild dehydration from decreased water intake or use of laxatives,116 decreased mobility due to functional decline or forced inactivity due to disease or institutionalization, use of drugs that inhibit colonic motility (anticholinergic and narcotic medications), and effects of superimposed diseases that result in neurodegeneration. While some factors are not modifiable, it is important for gastroenterologists to recognize risk factors for constipation and avoid iatrogenic worsening of colonic slowing. A medication review should always be performed to identify potential culprits. Patients in long-term care facilities are particularly vulnerable to constipation due to decreased mobility and use of neuroleptic medications with anticholinergic side effects. Current recommendations stress the use of both fiber and stimulant laxatives in older patients, because fiber alone may not be effective in