Update on constipation: One treatment does not fit all

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ABSTRACTConstipation is a common clinical problem that can be difficult to manage. It has a variety of identifiable causes, but even idiopathic constipation has different possible mechanisms. Often, the key to improvement and patient satisfaction is to understand the mechanism and the patient.


  • A high-fiber diet often improves functional constipation, but it may worsen slow-transit constipation or dyssynergia (a failure of the pelvic floor muscles to relax). Nevertheless, fiber remains a mainstay of treatment for its ability to provide homogeneous stool consistency.
  • Drugs approved for treating constipation increase fluid in the lumen, speed intestinal transit, and improve stool consistency, while tegaserod (Zelnorm) additionally acts as a serotonin agonist.
  • Colonoscopy and other tests are reserved for patients with refractory constipation and those with symptoms suggesting colon cancer.
  • Prebiotics (short-chain carbohydrates that stimulate activity of beneficial colonic bacterial flora) and probiotics (live bacterial preparations) are under evaluation as treatments for chronic constipation.



Constipation is both a symptom and, when chronic, a multisymptom disorder, and it can overlap with other gastrointestinal tract disorders such as dyspepsia and gastroesophageal reflux disease. Furthermore, one should keep in mind the possibility of cancer and be alert for its warning signs.

Since constipation has a variety of causes and forms, one treatment does not fit all patients. Conservative measures such as recommending that the patient increase his or her intake of dietary fiber and water and engage in more physical activity are still the cornerstone of treatment, but they do not help all patients. On the other hand, polyethylene glycol and stimulant laxatives, which are traditionally given only for a short time, can be safe and effective when given long-term if other agents fail. New agents have become available or are in development.

In this article we outline our approach to constipation, as a guide for internists.


Constipation affects 2% to 27% (average 14.8%) of the North American adult population—approximately 63 million people.1 It is more common than many other chronic diseases, including hypertension (48 million people), migraine (33 million), obesity (50 million), and diabetes mellitus (15 million).1–3

Constipation affects more women than men (2.1:1 ratio) and more nonwhites than whites (1.68:1).1 It occurs in all age groups but is more common in those older than 65 years and younger than 4 years.4,5

Constipation accounts for more than 2.5 million office visits and more than $500 million spent on laxatives per year.6,7 Also, people with constipation may report decreased productivity and increased absenteeism.8

The broad range in the prevalence of constipation cited above reflects differences in how it is defined and, in particular, a lack of agreement between how patients and physicians perceive it.1,9 Physicians mainly define constipation on the basis of stool frequency, considering fewer than three bowel movements per week to be abnormal.1 In contrast, patients typically define it on the basis of bothersome symptoms such as straining, passage of hard stool, unproductive urges, inability to defecate at will, and sensations of incomplete evacuation or abdominal bloating.1,9,10

The Rome III diagnostic criteria were developed to provide a consistent diagnostic approach for use in clinical practice and clinical trials.11 The Rome III criteria define functional chronic constipation as a chronic bowel disorder characterized by two or more of the following:

  • Straining
  • Lumpy or hard stools
  • Sensations of incomplete evacuation
  • Sensations of anorectal obstruction or blockage
  • Use of manual maneuvers to facilitate defecation (eg, digital evacuation, support of the pelvic floor) during at least 25% of defecations
  • Fewer than three bowel movements per week.

In addition, loose stools should rarely occur without the use of laxatives, and there should be insufficient criteria for irritable bowel syndrome.11 Chronicity is established by symptom onset within the previous 6 months and symptom duration of at least 3 months.

In contrast, patients with irritable bowel syndrome, also a functional bowel disorder, experience recurrent abdominal pain and discomfort associated with two or more of the following: symptom improvement with defecation, symptom onset associated with a change in the frequency of bowel movements, and a change in the form or appearance of the stool.


There are three types of primary or idiopathic constipation5,9,12,13:

  • Functional
  • Slow-transit
  • Outlet dysfunction.

Functional constipation includes functional chronic idiopathic constipation and constipation-predominant irritable bowel syndrome. It presents with a sense of difficult or delayed evacuation, hard stools, or abdominal bloating or discomfort.6,9,13 The predominant symptom of constipation-predominant irritable bowel syndrome is severe discomfort or pain; in chronic idiopathic constipation, pain and discomfort may be present but are not the primary symptom.

Slow-transit constipation (or delayed-transit constipation) is associated with a prolonged time between bowel movements. Its symptoms include low stool frequency, lack of urge to defecate, abdominal distention, bloating, and abdominal discomfort.14

Outlet dysfunction. Disorders of defecation can be due to mechanical causes such as Hirschsprung disease, anal stricture, cancer, prolapse, and large rectoceles, or from pelvic floor dysfunction. Pelvic floor dysfunction may be due to inadequate or excessive perineal descent or to inadequate propulsive forces, as may occur in neurologic or neuromuscular conditions and dyssynergia.

Pelvic floor dyssynergia, also called anorectal dyssynergia, dyssynergic defecation, and anismus, results from a functional defect in coordinated evacuation. The characteristic symptom is a feeling of being unable to adequately empty the rectum.14 Other symptoms such as excessive straining and manual disimpaction indicate but are not unique to pelvic floor dyssynergia.14,15

Combined forms. Patients may have more than one type of primary constipation and presentation, and pelvic floor dyssynergia has been shown to prolong intestinal transit, which may improve with treatment.

Secondary constipation can be due to causes such as diet, lifestyle, certain medications (calcium channel blockers, beta-blockers, opioids, diuretics, antidepressants, anticonvulsants, antacids, anticholinergics, and antispasmodics),5,16 underlying medical conditions (diabetes, hypothyroidism, multiple sclerosis, parkinsonism),16,17 pregnancy, and advanced age.18


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