Irritable bowel syndrome is a disorder of the digestive tract that causes recurring abdominal pain and constipation or diarrhea.
Symptoms vary but often include lower abdominal pain, bloating, gas, and constipation or diarrhea.
A variety of substances and emotional factors can trigger symptoms of irritable bowel syndrome.
A doctor usually diagnoses irritable bowel syndrome based on the symptoms but does tests to rule out other problems.
Diet modification and drugs can usually relieve specific symptoms.
Irritable bowel syndrome (IBS) is common among the general population. Some but not all studies suggest women with IBS are more likely to consult a doctor. IBS is the most common disorder diagnosed by gastroenterologists (doctors who specialize in disorders of the digestive tract) and is a common reason why many people visit their primary care physician.
IBS is a disorder of the movement of the intestines, the sensitivity of the nerves of the intestines, or the way in which the brain controls some of these functions. However, although the normal functioning is impaired, there are no structural abnormalities that can be found with an endoscope (a flexible viewing tube), imaging studies, biopsies, or blood tests. Thus, IBS is identified by the characteristics of the symptoms and, when done, normal results of tests.
Causes of IBS
The cause of IBS is not clear. In many people with IBS, the digestive tract is especially sensitive to stimuli. People may experience discomfort caused by intestinal gas or contractions that other people do not find distressing. Although the changes in bowel movements that occur with IBS might seem to be related to abnormal intestinal contractions, not all people with IBS have abnormal contractions, and in many of those who do, the abnormal contractions do not always coincide with symptoms. In some people, symptoms of IBS begin after an episode of gastroenteritis.
For some people, high-calorie meals or a high-fat diet may be a trigger.
For other people, wheat, dairy products, beans, chocolate, coffee, tea, some artificial sweeteners, certain vegetables (such as asparagus or broccoli), or stone fruits (such as apricots) seem to aggravate the symptoms. These foods contain carbohydrates that are poorly absorbed by the small intestine. The carbohydrates become fermented by bacteria in the intestine, which causes gas, bloating, and cramping. Because many food products contain several ingredients, it may be difficult to identify the specific trigger.
Other people find that eating too quickly or eating after too long a period without food stimulates a flare-up (a bout or attack). However, the relationship is inconsistent.
Emotional factors (for example, stress, anxiety, depression, and fear), drugs (including laxatives), or hormones may trigger or worsen a flare-up of IBS.
People do not always get symptoms after a usual trigger, and symptoms often appear without any obvious trigger. It is not clear how all the triggers relate to the cause of IBS.
Symptoms of IBS
IBS tends to begin in adolescence and the 20s, causing bouts of symptoms that come and go at irregular periods. The start of IBS symptoms in late adult life is less common but not rare. Flare-ups almost always occur when a person is awake, and they rarely wake a person from sleep.
Symptoms of irritable bowel syndrome include abdominal pain related to or relieved by having a bowel movement (defecation). The abdominal pain is associated with a change in stool frequency (such as constipation or diarrhea) or consistency (loose or lumpy and hard). The pain may come in bouts of continuous dull aching or cramps, usually over the lower abdomen. Symptoms of IBS can also include abdominal expansion (distention), mucus in the stool, and the sensation of incomplete emptying after defecation.
Bloating, gas, nausea, headaches, fatigue, depression, anxiety, muscle aches, problems with sleep, and difficulty concentrating are other possible symptoms.
Diagnosis of IBS
A doctor's evaluation based on the person's symptoms
Some laboratory tests to look for other disorders
Most people with IBS appear healthy. Doctors base the diagnosis of irritable bowel syndrome on the characteristics of the person's symptoms. Doctors also use standardized symptom-based criteria for diagnosing IBS called the Rome criteria. They may also do tests to diagnose common illnesses that can cause similar symptoms, particularly when people are over 45 or have warning signs such as weight loss, rectal bleeding, or older age.
Doctors use the Rome criteria to diagnose IBS in people who have had abdominal pain for at least 1 day a week in the last 3 months along with 2 or more of the following:
Pain is related to defecation.
Pain is associated with a change in stool frequency (constipation or diarrhea).
Pain is associated with a change in the consistency of stool.
A physical examination generally does not reveal anything unusual except sometimes tenderness over the large intestine. Doctors do a digital rectal examination, in which a gloved finger is inserted in the person's rectum. Women also may undergo a pelvic examination.
Doctors usually do some tests, for example, blood tests, to differentiate IBS from Crohn disease, ulcerative colitis, cancer (mainly in people over age 45), microscopic colitis, celiac disease, and other diseases and infections that can cause abdominal pain and changes in bowel habits. These test results are usually normal in people with IBS.
Doctors may do other tests, such as ultrasonography of the abdomen or x-rays of the intestines, in people who have symptoms that are unusual for IBS, such as fever, bloody stools, weight loss, and vomiting. Colonoscopy usually is done in people over 45 years of age to rule out tumors or polyps in the large intestine.
Other digestive tract disorders (such as appendicitis, gallbladder disease, ulcers, and cancer) may develop in a person with IBS, particularly after age 45. Thus, if a person’s symptoms change significantly, if new symptoms develop, or if symptoms are unusual for IBS, further testing may be needed.
Because IBS symptoms can be triggered by stress and emotional conflicts, doctors ask questions to help identify stress, anxiety, or mood disorders. Doctors also ask questions to rule out laxative abuse.
Treatment of IBS
Eating a normal diet and avoiding gas-producing and diarrhea-producing foods
Increasing fiber and water intake for constipation
Sometimes drugs
Treatment of IBS differs from person to person. If particular foods or types of stress appear to bring on the problem, they should be avoided if possible. For most people, especially those who tend to be constipated, regular physical activity helps keep the digestive tract functioning normally.
Diet
(For more information about diet and IBS, see these recommendations from the National Institute of Diabetes and Digestive Disease.)
Many people do better eating frequent, smaller meals rather than less frequent, larger meals (for example, 5 or 6 small meals rather than 3 large meals a day). People should try to slow their pace while eating. People with bloating and increased gas (flatulence) should avoid beans, cabbage, and other foods that are difficult to digest.
Some people find relief from IBS symptoms by restricting their intake of foods that are high in certain carbohydrates called fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These foods are collectively called FODMAPs. FODMAPs are carbohydrates that are poorly absorbed and rapidly fermented by bacteria in the small intestine, leading to increased gas and discomfort.
lactose intolerance), which is found in milk and other dairy products, should consume dairy products only in moderation.
People can try reducing their intake of the foods mentioned above one at a time and noting whether their symptoms change, or they can try a low-FODMAP diet, which restricts all of these foods.
A low-fat diet helps some people, particularly those whose stomach empties too slowly or too quickly.
Drugs
Certain laxatives
Anticholinergic drugs, see Anticholinergic: What Does It Mean?), such as dry mouth, blurred vision, or difficulty urinating.
Antidiarrheal drugs,
The antibiotic
is occasionally used for diarrhea in older women for whom other drugs are ineffective, but alosetron has been associated with increasing the risk of ischemic colitis, so its use is restricted in the United States.
Certain antidepressants
Probiotics, which are bacteria naturally found in the body that promote the growth of good bacteria, may be given.
Aromatic oils, such as peppermint oil, often help relieve pain caused by cramps in some people.
Other treatments
Behavior modification techniques (such as cognitive-behavioral therapy), psychotherapy, and hypnotherapy (hypnosis) may help some people who have IBS.
More Information
The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
International Foundation for Functional Gastrointestinal Disorders (IFFGD): Education, assistance, and support for people affected by gastrointestinal (GI) disorders
National Institutes of Health (NIH): Eating, diet (including FODMAP diet), and nutrition information for irritable bowel syndrome
