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Upon completion of the chapter, the reader will be able to:

  1. Identify the causes of constipation.

  2. Compare the features of constipation with those of irritable bowel syndrome with constipation (IBS-C).

  3. Recommend lifestyle modifications and pharmacotherapy for treatment of constipation.

  4. Distinguish between acute and chronic diarrhea.

  5. Compare and contrast diarrhea caused by different infectious agents.

  6. Explain how medication use can cause diarrhea.

  7. Discuss nonpharmacologic strategies for treating diarrhea.

  8. Identify the signs and symptoms of IBS.

  9. Contrast IBS with diarrhea (IBS-D) and IBS-C.

  10. Establish treatment goals for IBS.

  11. Evaluate the effectiveness of pharmacotherapy for IBS.


KEY CONCEPT Constipation, when not associated with symptoms of irritable bowel syndrome (IBS), is a syndrome characterized by infrequent bowel movements (less than 3 stools per week) or difficult passage of stools, hard stools, or a feeling of incomplete evacuation.1,2,3 Occasional constipation usually does not require medical evaluation or treatment.


Constipation affects all ages and occurs in approximately 16% of all adults and in one-third of adults age 60 and older.1,4 Although constipation is rarely life threatening, it results in over 8 million physician visits, 1.1 million hospitalizations, and 5.3 million prescriptions annually.5,6,7

Non-whites, institutionalized elderly, and women are more prone to develop constipation. Some disease states and many medications are associated with constipation.1,2 Constipation has significant socioeconomic costs and considerable quality-of-life ramifications.8,9


Constipation can be due to primary and secondary causes (Table 21–1). Primary or idiopathic constipation is categorized as normal-transit constipation (NTC), slow-transit constipation (STC), or defecatory disorder constipation. In NTC, colonic motility is unchanged and patients experience hard stools despite normal movements. In STC, motility is decreased or caloric intake is inadequate, leading to infrequent, harder, drier stools. Defecatory disorders involve prolonged rectal storage of fecal residue or disorders of evacuation with normal or delayed colonic transit resulting in incomplete expulsion of feces from the rectum. Underlying causes may include inadequate relaxation of muscles or paradoxical contractions of the pelvic diaphragm, perineal membrane and deep perineal pouch (the pelvic floor) and the external anal sphincter during defecation.

Table 21–1Some Causes of Constipation

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