Irritable Bowel Syndrome Definition

A constellation of symptoms that reflect functional disturbance of the gastrointestinal system. Irritable Bowel Syndrome (IBS) is one of the most common gastrointestinal disorders that cause people to seek medical care, accounting for 10 percent of doctor visits each year. IBS symptoms are episodic and may range from mild to debilitating and typically manifest before age 35 years. IBS affects three times as many men as women.

Symptoms of Irritable Bowel Syndrome (IBS) and Diagnostic Path

The hallmark symptoms of Irritable Bowel Syndrome (IBS) are

Periods of exacerbation alternate with periods of remission. In women, exacerbation may accompany other symptoms of premenstrual syndrome (pms). Stress, emotional or physical, is a significant catalyst of symptoms for many people who have IBS. The diagnostic path generally includes the gamut of gastrointestinal tests, though diagnosis of IBS relates to the length of time the person has had symptoms and the frequency with which symptoms occur. Current diagnostic guidelines support a diagnosis of IBS when all of these four symptoms persist for longer than three months and doctors cannot detect any underlying pathologic reasons for the gastrointestinal disturbances.

Irritable Bowel Syndrome (IBS) Treatment Options and Outlook

Treatment targets symptoms and may include Antidiarrheal medications, anticholinergic medications to slow intestinal motility, and certain antidepressant medications that are successful in relieving symptoms in chronic pain syndromes. Several medications specifically to treat IBS are available. There are significant risks and restrictions for some of these medications, and current regulatory and practice standards limit their use to people whose symptoms fail to respond to other treatments and interfere with daily living.

Alosetron (Lotronex)

Alosetron specifically targets the neuroreceptors in the colon to block thepassage of nerve signals that cause the colon to contract. This slows peristalsis only in the colon, increasing the amount of time digestive matter remains in the colon so the colon can absorb more water from it. Alosetron is available only for use in women who have debilitating diarrhea as the primary component of their IBS and under strict guidelines in which the prescribing doctor and the woman must agree to follow.

Alosetron is not available for men because there is insufficient evidence of its effectiveness in men; clinical research studies enrolled primarily women. The most significant risks of alosetron are severe constipation that causes bowel obstruction (ileus) and ischemic colitis (blocked blood flow to the colon that results in infection).

Tegaserod (Zelnorm)

Tegaserod mimics the action of serotonin, increasing the response of serotonin neuroreceptors in the intestinal tract. Serotonin is a neurotransmitter most commonly recognized for its role in carrying nerve impulses related to emotion in the brain. However, 95 percent of the serotonin in the body is concentrated in the gastrointestinal tract where it facilitates intestinal motility (peristalsis), gastric acid and other gastrointestinal fluid secretions, and the sensitivity of cells in the gastrointestinal tract to register pain. Like alosetron, tegaserod is available only for use in women who have debilitating diarrhea and presents the risk of ischemic colitis. Tegaserod also can cause severe diarrhea.


Antidepressant medications affect the actions of several neurotransmitters, such as dopamine and serotonin, that play roles both in brain activity related to emotion and in gastrointestinal functions. The tricyclic antidepressants, such as amitriptyline (Elavil) and imipramine (Tofranil), have been instrumental in treating chronic pain syndromes and provide relief from IBS symptoms for some people. Selective serotonin reuptake inhibitor (SSRI) antidepressants, such as paroxetine (Paxil) and fluoxetine (Prozac), seem to have similar effects. These medications also treat the mild to moderate DEPRESSION that commonly accompanies IBS.


There is a strong correlation between episodes of IBS symptoms and stress. Stress management techniques, meditation, guided imagery, biofeedback, yoga, acupuncture, and therapeutic counseling are among the methods that can help keep symptoms in remission. Many people can control IBS largely through diet and lifestyle, after they understand the nature of the disorder and learn to recognize the triggers that bring on attacks of symptoms. Helpful dietary and lifestyle changes include

  • reduce or eliminate caffeine, which can contribute to diarrhea
  • add fiber by eating more fruits, vegetables, and whole grain products, or by taking a fiber supplement such as psyllium (Metamucil) or methylcellulose (Citrucel)
  • eliminate foods and beverages that cause intestinal upset (especially foods high in fat)
  • maintain healthy weight
  • develop a daily process for stress relief that may incorporate exercise, meditation, warm baths, designated quiet time or alone time, or other methods for de-stressing
  • note circumstances and situations that appear to precipitate exacerbations of symptoms and work out approaches to mitigate them
  • get 30 to 45 minutes of physical exercise, such as walking, daily to improve circulation, muscle tone, and gastrointestinal function as well as to aid in relieving stress

Risk Factors and Prevention Efforts

Unlike many other chronic disorders affecting the gastrointestinal tract, Irritable Bowel Syndrome (IBS) does not cause any damage to gastrointestinal tissue or increase the risk for cancer. Even during attacks of symptoms, the bowel shows no evidence of inflammation or disease process. Tests that measure muscle contraction activity, usually performed only in clinical research studies because they have little diagnostic or therapeutic value, show accelerated peristalsis (intestinal motility).

A significant contingent of researchers and doctors believes IBS has a strong psychological component. This derives in part from the difficulty in identifying any organic, or physical, changes in the gastrointestinal tract that account for the symptoms and in part from a high correlation of diagnosed psychological conditions, such as generalized anxiety disorder (gad) and depression, among people who have IBS. As well, a high percentage of people who have IBS have experienced physical or sexual abuse. Though few argue that these correlations exist, disagreement remains as to what the correlations mean in the context of either the psychological disorder or the IBS, especially in regard to treatment options.

One intriguing direction of research is the exploration of neurohormonal processes that handle both psychological and autonomic (involuntary) functions, raising the possibility of crossover between the two. Some clinical research studies have noted similarities in altered brain activity patterns, as detected via imaging procedures such as positron emission tomography (pet) scan in people who have, independently, clinical depression and IBS. Other directions in research focus on gaining improved understanding of intestinal motility mechanisms. Though for some people IBS is a lifelong condition that requires vigilant management, for many others symptoms abate with an appropriate integration of medical and lifestyle interventions.


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