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Irritable bowel syndrome (IBS) is a gastrointestinal disorder characterized by recurrent abdominal pain and altered bowel habits in the absence of any identifiable structural abnormality in the bowel. It is one of the most common, and one of the most baffling, chronic digestive disorders in industrialized countries. It affects about 20% of women and 10% of men. It is thought that about 70% of affected people never seek medical attention. Earlier terms describing the same condition are irritable colon, spastic colitis, mucous colitis, and nervous colon.
It is usually a disorder of the large intestine (colon) but it may involve the small intestine and the stomach. The colon serves two important functions. First, it absorbs water from the stools so that a soft formed stool is formed. Second, it propels the stool from the right side of the colon to the rectum where it is stored until it is evacuated. This movement occurs in rhythmic contractions called peristalsis. When IBS occurs, the colon does not contract normally. Instead it may contract in a disorganized and at time violent manner.
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Symptoms
Persons with IBS may present with a wide variety of symptoms, which include both gastrointestinal and nongastrointestinal complaints.
Abdominal pain: Pain is usually intermittent and varies in intensity. It is often described as crampy in nature. The severity may range from mildly annoying to debilitating.
Altered bowel habit: Persons with IBS may complain of diarrhea or constipation, or both. They may notice mucous in the stools. There may be a sense of incomplete evacuation after a bowel movement. Bleeding is not a feature of IBS
Other gastrointestinal symptoms: There may also be gastroesophageal reflux, nausea, abdominal bloating, and flatulence.
Nonintestinal manifestations: Persons with IBS often have a broad range of nongastrointestinal symptoms. Depression, sexual dysfunction, asthma, and fibromyalgia may at times accompany IBS.
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Causes
The cause of IBS remains uncertain. Despite intensive studies, results have been conflicting and no single abnormality has been found to be specific for this disorder. It has been shown that alertness, arousal, and anxiety lead to alterations in patterns gastrointestinal muscle contraction in normal individuals. The current view is that persons with IBS may have a dysfunction in the relationship between gut and brain manifest by enhanced muscle activity in the gut and altered perception and modulation of that activity in the brain. Serotonin (a chemical in the brain which plays an important role in the regulation of mood) also occurs in the intestine and seems to play an important role in controlling colonic muscle activity, secretion of fluid in the intestine, and pain perception in the intestine.
Gastrointestinal motility: Several studies have demonstrated abnormal patterns of muscle contraction in the colon and the small intestine of persons with IBS. In some persons with IBS there is prolonged and enhanced muscle activity in the colon and rectum following a meal.
Hypersensitivity to colon activity: Persons complaining of bloating and excess gas usually have similar volumes of gas in the GI tract as those without complaints. In clinical studies in which balloons are inflated in the intestine, persons with IBS experience pain sooner than normal controls. These and other studies suggest that persons with IBS may have a hypersensitivity to colon activity and distention.
Psychosocial factors: Many persons with IBS who report to referral centers also suffer from anxiety and depression. Persons with IBS are also slightly more likely to have suffered from abuse. However, persons with IBS who do not seek medical attention are psychologically indistinguishable from normal controls. The implication of these observations is that psychologic distress may influence the experience of IBS but does not cause the symptoms.
Infections: Persistent IBS symptoms are frequently observed in patients who have acute bacterial infections of the gastrointestinal tract. However, there have been no comprehensive studies to investigate this.
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Diagnosis
Classic symptom complex includes at least 3 months of continuous or recurring abdominal pain or discomfort relieved with a bowel movement, or associated with a change in frequency or consistency of stool. Bleeding and weight loss are not features of IBS. General physical examination is normal. Diagnostic studies should be minimal. Routine blood and stool tests should be done. Flexible sigmoidoscopy or colonoscopy, or combination sigmoidoscopy and barium enema should be done in those over 50 years old. In persons with diarrhea predominant, it may be necessary to do x-rays of the small intestine.
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Treatment
General principles: IBS is a chronic condition with no known cure. Symptoms tend to come and go and do not result in progressive damage or disability. Therefore the focus of treatment should be on relief of symptoms and addressing the patient’s concerns. Since symptoms tend to vary over time, it is important for the individual with IBS to have an understanding of the symptoms, the benign nature of the condition, and the various modalities of therapy available. This will empower the individual to take control of his/her condition. Control of symptoms may involve a simple change in daily habits, eating better, and exercising regularly.
Dietary modification: Dairy foods should be avoided by individuals with lactose intolerance (see article on lactose intolerance in the Diet section of this web site). Exclusion of foods that increase flatulence (beans, onions, cabbage, brussel sprouts, wheat germ, etc.) should be considered in those with complaints of excessive gas and bloating. However, oftentimes complaints of excessive gas are due to diminished tolerance of normal levels of gas. An increase in fiber is often recommended either through diet (see article on high fiber diet in the Diet section of this web site) or fiber supplements such as Metamucil, Citrucel, or Fibercon. Fiber causes retention of water in the stool, making the stools bulkier and softer. This is often helpful for patients with constipation predominant IBS. Since the simple act of eating may trigger colon activity, it is sometimes helpful to eat smaller, more frequent meals.
Antispasmodic (anticholinergic) drugs: Theseare the most frequently used drugs for the treatment of IBS. They inhibit gastrointestinal muscle activity and may be particularly helpful for those with abdominal pain, bloating, and fecal urgency. Dicyclomine (Bentyl) and hyocyamine (Levsin) are examples of commonly used antispasmodics. They are generally safe to use but could be problematic for those with glaucoma or prostate problems. In addition, they could make heartburn worse.
Antidepressants: Most antidepressants have analgesic properties independent of their mood improving effects. There is some evidence that they may diminish the hypersensitivity to colon activity that may account for some of the symptoms. Tricycle antidepressants such as amitriptyline (Elavil) have antispasmodic properties and may be helpful in those with pain and diarrhea. The serotonin reuptake inhibitors such as fluoxetine (Prozac) and sertraline (Zoloft) may be particularly effective for those with pain and constipation.
Serotonin 5-HT3 antagonists: This is a new class of drug which became commercially available in the form of alosetron (Lotronex) in February, 2000. Although very helpful to many patients, it was taken off the market because of concern about side effects. However, it is now available again under a restricted prescribing program for women with diarrhea predominant irritable bowel syndrome. Your gastroenterologists at Main Line Gastroenterology Associates are accredited to prescribe this drug.
Serotonin 5-HT4 antagonists: Tegaserod (Zelnorm) became available in the fall of 2002. It has been very helpful for many women with constipation predominant irritable bowel syndrome. However, it was taken off the market on March 30, 2007 because of reports of a high incidence of cardiovascular disease in individuals taking Zelnorm. It is unknown at this time if there is a cause and effect relationship between Zelnorm and cardiovascular disease. It is also not known if or when it will become available.
Antibiotics: There have been several reports that a rifaximin (Xifaxan), new antibiotic that is not absorbed across the lining of the intestine, may be helpful for those with complains of gas and bloating. This suggests that bacterial overgrowth in the intestine may be responsible for symptoms in some individuals with irritable bowel.
Antianxiety drugs: Antianxiety drugs such as alprazolam (Ativan) and lorazepam (Xanax) have a limited role in the management of IBS because of the risk of dependence and withdrawal reactions. Furthermore, they may actually lower pain thresholds. However, they, at times, can be very useful for short-term control of acute situational anxiety that may be contributing to symptoms.
Antidiarrheal agents: Loperimide (Imodium) has been shown to be beneficial in reducing diarrhea, urgency to defecate, and bloating. It can be used on as needed basis.
Laxatives: Chronic use of laxative should be avoided. Constipation should be treated with high fiber diet and fiber supplements. If constipation does not respond to diet manipulation, lactulose and Miralax can be used safely on a regular basis. Herbal laxatives usually contain senna, which can be harmful to the colon if used on a regular basis.
Psychosocial therapies: Behavioral treatments may be useful for motivated patients who associate symptoms with stressors. Hypnosis, biofeedback, psychotherapy, and relaxation therapies help to reduce anxiety levels, encourage health-promoting behavior, and improve pain tolerance. The Jefferson Health System and Main Line Health offer a course in "Mindfulness" which should be considered by those who wish to reduce their anxiety and learn relaxation techniques. Physical exercise may also be helpful.
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Prognosis
IBS does not lead to cancer. It is not associated with progressive disability. Symptoms will disappear, although they are likely to return. It is realistic to expect that proper management can result in symptoms becoming infrequent and mild.
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