Irritable Bowel Syndrome
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Irritable Bowel Syndrome National Digestive Diseases Information Clearinghouse What is irritable bowel IBS is often classified into four subtypes based on a person’s usual stool consistency. syndrome (IBS)? These subtypes are important because they Irritable bowel syndrome is a functional affect the types of treatment that are most gastrointestinal (GI) disorder, meaning likely to improve the person’s symptoms. symptoms are caused by changes in how the The four subtypes of IBS are GI tract works. People with a functional GI disorder have frequent symptoms; however, • IBS with constipation (IBS-C) the GI tract does not become damaged. IBS – hard or lumpy stools at least is a group of symptoms that occur together, 25 percent of the time not a disease. In the past, IBS was called – loose or watery stools less than colitis, mucous colitis, spastic colon, nervous 25 percent of the time colon, and spastic bowel. The name was changed to reflect the understanding that • IBS with diarrhea (IBS-D) the disorder has both physical and mental – loose or watery stools at least causes and is not a product of a person’s 25 percent of the time imagination. – hard or lumpy stools less than IBS is diagnosed when a person has had 25 percent of the time abdominal pain or discomfort at least three • Mixed IBS (IBS-M) times a month for the last 3 months without other disease or injury that could explain – hard or lumpy stools at least the pain. The pain or discomfort of IBS 25 percent of the time may occur with a change in stool frequency – loose or watery stools at least or consistency or be relieved by a bowel 25 percent of the time movement. • Unsubtyped IBS (IBS-U) – hard or lumpy stools less than 25 percent of the time – loose or watery stools less than 25 percent of the time What is the GI tract? The GI tract is a series of hollow organs joined in a long, twisting tube from the Esophagus mouth to the anus—the opening through Mouth which stool leaves the body. Food is digested by the movement of muscles in the GI tract, along with the release of hormones and Stomach enzymes. Organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine—which includes the appendix, cecum, colon, and rectum—and anus. The intestines are sometimes called the bowel. The last part of the GI tract— called the lower GI tract—consists of the Small large intestine and anus. intestine The large intestine absorbs water and any Large remaining nutrients from partially digested intestine food passed from the small intestine. The Appendix large intestine then changes waste from Anus liquid to a solid matter called stool. Stool Rectum passes from the colon to the rectum. The rectum is located between the last part of The organs of the GI tract the colon—called the sigmoid colon—and the anus. The rectum stores stool prior to a bowel movement. During a bowel movement, stool moves from the rectum to the anus. 2 Irritable Bowel Syndrome How common is IBS and • constipation—having fewer than three bowel movements a week. During a who is affected? bowel movement, stools can be hard, Studies estimate IBS affects 3 to 20 percent dry, and small, making them difficult to of the adult population, with most studies pass. Some people find it painful and ranging from 10 to 15 percent.1 However, often have to strain to have a bowel only 5 to 7 percent of the adult population movement. has been diagnosed with the condition.2 IBS affects about twice as many women as men • feeling that a bowel movement is and is most often found in people younger incomplete. than age 45.1 • passing mucus—a clear liquid made by the intestines that coats and protects What are the symptoms tissues in the GI tract. of IBS? • abdominal bloating. The most common symptoms of IBS are Symptoms may often occur after eating abdominal pain or discomfort, often reported a meal. To meet the definition of IBS, as cramping, along with changes in bowel symptoms must occur at least three times a habits. To meet the definition of IBS, the month. pain or discomfort will be associated with at least two of the following three symptoms: What causes IBS? • bowel movements that occur more or The causes of IBS are not well understood. less often than usual Researchers believe a combination of • stool that appears less solid and more physical and mental health problems can watery, or harder and more lumpy, than lead to IBS. usual Brain-Gut Signal Problems • bowel movements that improve the Signals between the brain and nerves of the discomfort small and large intestines, also called the gut, Other symptoms of IBS may include control how the intestines work. Problems with brain-gut signals may cause IBS • diarrhea—having loose, watery stools symptoms, such as changes in bowel habits three or more times a day and feeling and pain or discomfort. urgency to have a bowel movement. GI Motor Problems Normal motility, or movement, may not be present in the colon of a person who has IBS. Slow motility can lead to constipation and fast motility can lead to diarrhea. Spasms, or sudden, strong muscle contractions that 1Grundmann O, Yoon SL. Irritable bowel syndrome: come and go, can cause abdominal pain. epidemiology, diagnosis, and treatment: an update for Some people with IBS also experience health-care practitioners. Journal of Gastroenterology and Hepatology. 2010;25:691–699. hyperreactivity—a dramatic increase in bowel contractions in response to stress or 2 Irritable bowel syndrome. American College of eating. Gastroenterology website. www.patients.gi.org/topics/ irritable-bowel-syndrome. Accessed May 27, 2014. 3 Irritable Bowel Syndrome Hypersensitivity IBS, and some studies have shown antibiotics People with IBS have a lower pain threshold to be effective in treating IBS. However, for bowel stretching caused by gas or stool more research is needed to show a link compared with people who do not have IBS. between small intestinal bacterial overgrowth The brain may process pain signals from the and IBS. bowel differently in people with IBS. Body Chemicals Mental Health Problems People with IBS have altered levels of Mental health, or psychological, problems neurotransmitters—chemicals in the such as panic disorder, anxiety, depression, body that transmit nerve signals—and GI and post-traumatic stress disorder are hormones, though the role these chemicals common in people with IBS. The link play in developing IBS is unclear. Younger between these disorders and development of women with IBS often have more symptoms IBS is unclear. GI disorders, including IBS, during their menstrual periods. Post- are often found in people who have reported menopausal women have fewer symptoms past physical or sexual abuse. Researchers compared with women who are still believe people who have been abused tend to menstruating. These findings suggest that express psychological stress through physical reproductive hormones can worsen IBS symptoms. problems. Bacterial Gastroenteritis Genetics Some people who have bacterial Whether IBS has a genetic cause, meaning gastroenteritis—an infection or irritation it runs in families, is unclear. Studies have of the stomach and intestines caused by shown IBS is more common in people with bacteria—develop IBS. Researchers do family members who have a history of GI not know why gastroenteritis leads to IBS problems. However, the cause could be in some people and not others, though environmental or the result of heightened abnormalities of the GI tract lining and awareness of GI symptoms. psychological problems may be factors. Food Sensitivity Small Intestinal Bacterial Many people with IBS report that symptoms Overgrowth are triggered by foods rich in carbohydrates, spicy or fatty foods, coffee, and alcohol. Normally, few bacteria live in the small However, people with food sensitivity intestine. Small intestinal bacterial typically do not have clinical signs of food overgrowth is an increase in the number or allergy. Researchers have proposed that a change in the type of bacteria in the small symptoms may result from poor absorption intestine. These bacteria can produce extra of sugars or bile acids, which help break gas and may also cause diarrhea and weight down fats and get rid of wastes in the body. loss. Some researchers believe that small intestinal bacterial overgrowth may lead to 4 Irritable Bowel Syndrome How is IBS diagnosed? Additional diagnostic tests may include a stool test, lower GI series, and flexible To diagnose IBS, a health care provider will sigmoidoscopy or colonoscopy. Colonoscopy conduct a physical exam and take a complete may also be recommended for people who medical history. The medical history will are older than age 50 to screen for colon include questions about symptoms, family cancer. history of GI disorders, recent infections, medications, and stressful events related to A stool test is the analysis of a sample of the onset of symptoms. An IBS diagnosis stool. The health care provider will give the requires that symptoms started at least person a container for catching and storing 6 months prior and occurred at least three the stool. The sample is returned to the times a month for the previous 3 months. health care provider or a commercial facility Further testing is not usually needed, though and sent to a lab for analysis. The health the health care provider may perform a care provider may also do a rectal exam, blood test to screen for other problems. sometimes during the physical exam, to Additional diagnostic tests may be needed check for blood in the stool. Stool tests can based on the results of the screening blood show the presence of parasites or blood.