Management of irritable bowel syndrome - Cover Article Practical Therapeutics

Author: Anthony J. Viera, Joseph Shaughnessy
Date: Nov 15, 2002

Irritable bowel syndrome (IBS) is a benign, chronic symptom complex of altered bowel habits and abdominal pain. It is considered a functional type of bowel disorder. That is, no organic or structural cause can be detected (using currently available diagnostic modalities) to explain its symptoms. It is the most common functional disorder of the gastrointestinal (GI) tract. Other disorders in this group include functional dyspepsia, functional anorectal pain, and noncardiac chest pain. The many forms and presentations of IBS can make the diagnosis challenging, and its functional nature can make a satisfactory treatment regimen difficult.

Epidemiology

In the United States, IBS has been reported to account for up to 3.5 million physician visits annually, at an estimated cost of $8 billion. It remains the most common diagnosis in gastroenterologic practices. (1)

The reported prevalence of patients in the general population with symptoms consistent with IBS ranges from 10 to 20 percent, and only 10 to 30 percent of those patients seek medical care. (2) At five-year follow-up of IBS patients, 5 percent report complete recovery and up to 30 percent report partial recovery. (3)

In most parts of the world, women are affected more often then men. (4) IBS symptoms are common in adolescents and correlate with anxiety and depression in this population. (5) Symptoms begin before 35 years of age in 50 percent of patients, and almost all report symptom onset before 50 years of age. (4) Although IBS is seen in the elderly, new onset of symptoms after age 50 may indicate other organic pathology and warrants a more comprehensive evaluation. (6)

Etiology and Pathophysiology

The etiology of IBS remains unclear. Theories have ranged from purely psychologic to more recent proposals about postinfectious alterations in GI tract neuromuscular function. IBS may best be viewed as a biopsychosocial disorder in which altered GI motility, GI hypersensitivity, and psychosocial factors all interact to predispose someone to the syndrome.

Patients with IBS have an exaggerated gastrocolic reflex, altered gastric emptying, increased small bowel contractions, and increased small intestinal transit, all of which are exacerbated by food intake or stress. (7) However, more than 50 percent of healthy individuals report similar symptoms during increased stress. (8) Therefore, other factors likely play an important role in the patient who develops IBS.

One such factor may be the involvement of neurotransmitters such as serotonin, which may stimulate intestinal secretion and peristalsis in addition to visceral pain receptors via 5-HT3 and 5-HT4 pathways. It is at neurotransmitter receptors such as these that new and investigational therapeutic agents are targeted.

Psychosocial factors also play an important role in the development of IBS and may be the most important factors in terms of who manifests IBS and how severe it becomes. (9) For example, traumatic life events such as a history of physical or sexual abuse have been shown to correlate with the development of IBS and the severity of its symptoms. (10) Studies have repeatedly shown a higher incidence of anxiety, hypochondriasis, and depression in IBS patients. (11) A multicomponent model (Figure 1) has been proposed that shows the relationship of psychosocial (cognitive, behavior, emotional) and physiologic components of IBS. (7)

Clinical Presentation

Abdominal pain relieved by defecation and pain associated with looser or more frequent stools are the hallmark signs and symptoms of IBS. Patients also may experience diarrhea, constipation, alternating diarrhea and constipation, mucus in stools, dyspepsia, atypical chest pain, bloating, and gas. Symptoms are typically worse at times of increased stress.

The most widely accepted diagnostic criteria for IBS are the Rome Criteria. The Rome I criteria (Table 1) (12) require the presence of at least two supportive features in addition to the main criteria. The Rome II criteria (Table 2) (13) base the diagnosis on the presence of two of the three main criteria without the need of additional supportive criteria. (14) The presence of any red flags (Table 3) (6,13) should alert the physician to an alternate diagnosis. For treatment purposes, the following symptom-guided categories are useful: pain-predominant, diarrhea-predominant, or constipation-predominant. Constipation may alternate with diarrhea in some IBS patients. Table 4 lists some pharmacotherapeutic options based on predominant symptoms.

Management

EFFECTIVE THERAPEUTIC RELATIONSHIP

A strong physician-patient relationship is paramount in an effective management strategy for IBS. A good physician-patient relationship has also been shown to reduce repetitive office visits. (16) The patient may need to be reassured repeatedly of the positive diagnosis, and specific patient concerns and fears will need to be addressed. The patient needs to be confidently told that there is no serious disease and there is no increased risk of complications (such as cancer) from IBS. A previous article (17) in American Family Physician outlines specific points in the development of an effective therapeutic relationship with patients who have IBS.

DIETARY RECOMMENDATIONS

While no specific dietary advice has been shown in trials to be efficacious, many authors advocate having patients limit alcohol, caffeine, sorbitol, and fat intake. (6) Lactose should be eliminated only in those with proven lactase deficiency. If a patient believes a particular dietary substance is exacerbating the symptoms, then a trial of eliminating that substance is warranted. However, in general, there is no association between IBS and food intolerance.

PAIN-PREDOMINANT IBS

Jailwala and colleagues (18) recently published a systematic review of randomized controlled trials (RCTs) of pharmacotherapy for IBS, in which 28 high-quality trials reporting outcomes of global improvement or IBS-specific symptom improvement were identified. [Evidence level A, systematic review of RCTs] Trials using bulking agents (various fiber products), smooth-muscle relaxants (e.g., cimetropium [not marketing a brand name yet]), prokinetic agents (e.g., cisapride [Propulsid]), loperamide (Imodium), and psychotropic agents (e.g., amitriptyline [Elavil]) were included. From this analysis, the authors concluded that smooth-muscle relaxants are beneficial for the abdominal pain of IBS. However, none of the smooth-muscle relaxants used in the high-quality trials are approved by the U.S. Food and Drug Administration (FDA) for use in the United States.

Although fiber is predominantly useful for the constipation of IBS, it may also reduce pain in IBS by reducing intracolonic pressure, though this effect has not been shown to be true in high-quality patient-oriented trials. (19) The efficacy of dietary fiber therapy can be difficult to assess because the placebo response in IBS trials has been as high as 71 percent. (20) [Evidence level A, RCT] Fiber should be started gradually in low doses to avoid bloating.

If dietary advice and fiber supplementation do not adequately relieve abdominal pain, a short-term trial of an antispasmodic agent such as dicyclomine (Bentyl) (18) or hyoscyamine (Levsin) may be tried. (18) If it is effective, it can then be used as needed. Chronic use of such a drug may reduce its efficacy. (19) Narcotics should be avoided.

Psychotropic agents also may benefit patients with IBS who have abdominal pain. Seven trials of psychotropic agents were included in Jailwala's systematic review. (18) All seven trials showed these agents to be efficacious, but only one of these trials was considered high-quality. This trial, involving only 14 patients, showed that the tricyclic antidepressant amitriptyline yielded global improvement in patients with IBS. (21) [Evidence level A, RCT] The use of such tricyclic antidepressants for pain relief in IBS may be effective, but their anticholinergic side effects can be troublesome. The selective serotonin reuptake inhibitors (SSRIs) have not proved to be effective agents for IBS. (15)

Tegaserod (Zelnorm), a 5-HT4 agonist (of the aminoguanide indole class) that has visceral antinociceptive effects, is a newer agent that may prove useful in pain-predominant IBS. It has been approved by the FDA for short-term treatment of women with IBS. (15,22) Pain in IBS may also be mediated by opioid receptors such as mu, kappa, and delta. Several drugs that act at these receptors are under investigation.

The authors indicate that they do not have any conflicts of interest. Sources of funding: none reported. The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the U.S. Navy Medical Department or the U.S. Naval Service at large.

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Members of various family practice departments develop articles for "Practical Therapeutics." This article is one in a series coordinated by the Department of Family Medicine at Naval Hospital Jacksonville, Jacksonville, Florida. Guest editor of the series is Anthony J. Viera, LCDR, MC, USNR.

ANTHONY J. VIERA, LCDR, MC, USNR, is a staff family physician at Naval Hospital Jacksonville in Jacksonville, Fla. He received his medical degree from the Medical University of South Carolina, Charleston, and completed his residency at Naval Hospital Jacksonville.

STEVE HOAG, LT, MC, USN, is currently a staff family physician at Naval Hospital Guam. He received his medical degree from the Uniformed Services University of the Health Sciences School of Medicine in Bethesda, Md., and completed his residency at Naval Hospital Jacksonville.

JOSEPH SHAUGHNESSY, CDR, MC, USN, is a staff family physician at Naval Hospital Jacksonville. He received his medical degree from the Uniformed Services University of the Health Sciences School of Medicine, and completed his residency at Naval Hospital Jacksonville.

Address correspondence to Anthony J. Viera, LCDR, MC, USNR, 1505 Maple Leaf Ln., Orange Park, FL 32003 (e-mail: anthonyjviera@yahoo.com). Reprints are not available from the authors.

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