Irritable Bowel Syndrome

September 15, 2011

Irritable bowel syndrome (IBS) is a common condition characterized by abdominal pain or discomfort, bloating, and changes in bowel habits. An international consensus of Irritable bowel syndrome specialists has defined Irritable bowel syndrome as “a combination of chronic or recurrent gastrointestinal symptoms which are not explained by structural or biochemical abnormalities.” Although causes of Irritable bowel syndrome are poorly understood, it is thought to result from a complex interplay of changes in intestinal motility, decreased tolerance for stretching of the intestine, psychological, and social factors.

An estimated 10-15% of the population in the United States is thought to have Irritable bowel syndrome. Irritable bowel syndrome has an enormous economic impact on society both in terms of work productivity and use of health care resources. Irritable bowel syndrome is responsible for a high rate of work absenteeism, with more than three times as many days missed annually by workers with Irritable bowel syndrome compared to workers without Irritable bowel syndrome. Irritable bowel syndrome patients have 2-3 times as many health care visits annually than non-Irritable bowel syndrome patients. Irritable bowel syndrome accounts for approximately 36% of patients seen by gastroenterologists and 12% of those seen by primary care providers. However, less than half of all Irritable bowel syndrome sufferers seek medical attention. The likelihood of seeking medical care is influenced less by the severity of symptoms and more by factors such as stress, psychiatric disorders (especially major depression and anxiety disorders), personality, and a history of abuse.

In the general population, up to two times as many women than men have Irritable bowel syndrome. However, among those seeking medical attention for their symptoms, there is a strong female predominance of up to 4:1. Similarly, although population studies reveal that Irritable bowel syndrome occurs equally across all adult age groups, young people in their 20s and early 30s are more likely to seek medical attention. Women are more likely to report constipation, bloating, nausea, and psychological symptoms.

DIAGNOSIS

Given the absence of any biochemical or structural abnormality in Irritable bowel syndrome, the diagnosis is made based on the symptoms listed as criteria for Irritable bowel syndrome. Laboratory testing is obtained to rule out other medical conditions, but tests should be chosen judiciously in order to avoid an unnecessarily expensive evaluation. The symptombased criteria for Irritable bowel syndrome include 12 weeks or more (not required to be consecutive) of abdominal pain or discomfort within the previous 12 months, accompanied by two of the following three symptom patterns: (a) pain relieved by defecation; and/or (b) onset of pain associated with a change in stool frequency; and/or (c) onset of pain associated with change in stool form (e.g., hard, loose, watery). Other symptoms that are commonly reported include the sensation of urgent need to move one’s bowels, sensation of incomplete emptying of the bowels, mucus passage, and abdominal bloating. Symptoms which are brought on or worsened by stress or meals are also frequently reported.

In general, a careful history, physical examination, and focused laboratory studies, including complete blood count, chemistry panel, albumin, thyroid function studies, and erythrocyte sedimentation rate should be performed. Patients with diarrhea should also have stool examined for ova and parasites. Other conditions that cause symptoms similar to Irritable bowel syndrome include colorectal cancer, inflammatory bowel disease, lactose intolerance, thyroid disorders, celiac disease, bacterial overgrowth, parasitic infection, and endometriosis. However, subjecting all patients with Irritable bowel syndrome-like symptoms to exhaustive testing in order to exclude these diseases is not recommended. In patients who meet Irritable bowel syndrome symptom criteria and who lack “alarm” signs or symptoms, the likelihood of discovering one of these diseases through an extensive evaluation (including endoscopy and radiology tests) is less than 1%. “Alarm” symptoms that do warrant extensive evaluation are weight loss, blood in stools, fever, abnormal physical examination, anemia, chronic severe diarrhea, nighttime diarrhea, a family history of colon cancer, symptoms of Irritable bowel syndrome developing for the first time in an elderly person, or symptoms that progressively worsen. Regardless of symptoms, all patients 50 years or more should be screened for colon cancer. Recent studies suggest that celiac sprue may be more common in those presenting with Irritable bowel syndrome-like symptoms. Therefore, in patients with diarrhea, laboratory tests for celiac sprue should be considered.

TREATMENT

Education about Irritable bowel syndrome and establishing a good relationship with a physician form the cornerstone of therapy. Instead of continued efforts to find a cause or “cure” for this chronic disorder, the goal should be the reduction of symptoms and development of coping skills. A diet history should be obtained to find out whether any foods or beverages (e.g., legumes, cabbage, broccoli, caffeine, lactose, sorbitol gum, and fatty foods) bring on or worsen symptoms. If a troublesome food is identified, the patient should try eliminating it from the diet to see whether symptoms improve. Most patients do well with education, reassurance, and dietary changes alone. For those who do not, a variety of medications may be used, either alone or in combination, and are chosen based on the individual patient’s symptoms.

MEDICATIONS

A number of fiber-containing agents (e.g., psyllium and methylcellulose) are available and are used in Irritable bowel syndrome patients with either diarrhea or constipation. In diarrhea, the fiber gives bulk to the stool, and in constipation, the fiber helps intestinal contents pass through the colon more rapidly. Patients should be advised to start with a low dose and to increase gradually, as needed, in order to minimize the common side effects of bloating, excessive intestinal gas, and abdominal discomfort. For Irritable bowel syndrome patients with diarrhea who fail a trial of fiber, the antidiarrheal medication loperamide has been shown to be effective.

For the abdominal pain associated with Irritable bowel syndrome, there are a number of medications available to reduce symptoms. For pain exacerbated by meals, antispasmodic agents (dicyclomine and hyoscyamine), given 30-60 minutes before meals, will help to relax intestinal smooth muscle and thereby reduce cramping. Pain that is more frequent or severe is treated with tricyclic antidepressants (e.g., amitriptyline). Lower doses than those required to treat depression have been shown to improve abdominal pain in Irritable bowel syndrome. However, given that constipation is a common side effect of tricyclic antidepressants, they should be used with caution in Irritable bowel syndrome patients with constipation. Prozac-type antidepressants (serotonin reuptake inhibitors like sertraline) have also been tried for Irritable bowel syndrome pain, but have not been shown to be effective in randomized clinical trials to date.

Serotonin is a chemical or “neurotransmitter” found both in the brain and the intestinal nervous system that transmits messages from one nerve to another. Serotonin has been found to be involved in the regulation of intestinal motility and sensation. This observation has led to the development of two new Irritable bowel syndrome treatments, tegaserod and alosetron, which act by different mechanisms on serotonin receptors. Tegaserod, acting primarily by speeding up colonic transit and decreasing intestinal pain sensitivity, has been shown to be more effective than placebo in relieving pain, bloating, and constipation in female Irritable bowel syndrome patients. Diarrhea is the most common side effect. Alosetron decreases gastrointestinal secretions and muscle contractions, thereby slowing colonic transit. It has been shown to be effective in improving stool frequency, stool consistency, and abdominal pain in female Irritable bowel syndrome patients with diarrhea. It is approved by the Food and Drug Administration (FDA) for “women with severe, diarrhea-predominant Irritable bowel syndrome who have failed to respond to conventional Irritable bowel syndrome therapy.” Constipation, at times severe, is a common adverse event. In addition, there have been a number of reports of ischemic colitis (inflammation due to poor blood flow to the colon) in people who use alosetron. Therefore, the FDA advises that physicians not only educate patients regarding the potential risks, but also carefully weigh an individual patient’s risks and benefits before prescribing. At this time, data do not support the use of either tegaserod or alosetron in men. Studies suggest that women have greater intestinal sensory perception, that is, increased sensitivity to bowel distention and peristalsis, and this may underlie the apparent difference in response to these new Irritable bowel syndrome treatments in men versus women.

BEHAVIORAL THERAPY

Because of the frequent association of symptoms with stress and the increased prevalence of psychiatric disorders among Irritable bowel syndrome sufferers seeking health care, a variety of behavioral therapies, including relaxation, biofeedback, hypnosis, cognitive therapy, and psychotherapy, have been tried in Irritable bowel syndrome. These behavioral therapies appear to be helpful in reducing chronic Irritable bowel syndrome symptoms by reducing anxiety and improving coping skills. If a psychiatric disorder is present, these therapies improve psychological symptoms as well. Severe refractory symptoms in women may signal a history of sexual or physical abuse.

Although Irritable bowel syndrome is a chronic condition, it is not life threatening nor does it lead to cancer or inflammatory bowel disease. Most people with Irritable bowel syndrome are able to minimize or even eliminate symptoms with dietary changes and stress reduction techniques. A few patients will also need prescription medications. When the diagnosis is unclear or when moderate to severe symptoms do not respond to therapy, a gastroenterologist should be consulted. Irritable bowel syndrome centers can help in difficult cases. For those patients in whom a psychiatric component seems likely, referral to a mental health professional is advised.

SEE ALSO: Diet, Nutrition

Suggested Reading

  • Brandt, L. J., Bjorkman, D., Fennerty, M. B., Locke, G. R., Olden, K., Peterson, W., et al. (2002). Systematic review on the management of irritable bowel syndrome in North America. American Journal of Gastroenterology, 97(11 Suppl.), S7—S26.
  • Cash, B. D., Schoenfeld, P., & Chey, W. D. (2002). The utility of diagnostic tests in irritable bowel syndrome patients: A systematic review. American Journal of Gastroenterology, 97(11), 2812—2819.
  • Chang, L., & Heitkemper, M. M. (2002). Gender differences in irritable bowel syndrome. Gastroenterology, 123(5), 1686—1701.
  • Heymann-Monnikes, I., Arnold, R., Florin, I., Herda, C., Melfsen, S., & Monnikes, H. (2000). The combination of medical treatment plus multicomponent behavioral therapy is superior to medical treatment alone in the therapy of irritable bowel syndrome. American Journal of Gastroenterology, 95(4), 981—994.

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