Irritable bowel syndrome (IBS) is the failure of the large intestine to operate properly. In patients with IBS, the large intestine appears to be more sensitive and reactive than normal, resulting in a collection of chronic symptoms that commonly occur after eating or when under stress.

The term "syndrome" is used to describe a pattern of symptoms that tend to occur together. The most common symptom of IBS is abdominal pain associated with diarrhea, constipation or both. Other symptoms of IBS include gas, bloating, cramping and indigestion.

Some patients experience diarrhea-predominant IBS or constipation-predominant IBS. However, most alternate between symptoms of diarrhea and constipation. Abdominal pain is often relieved by having a bowel movement.

IBS is one of the most common disorders diagnosed by physicians in the United States. It is estimated that one in five Americans has IBS. It typically begins around age 20 and occurs in women more often than in men.

Examination of patients with IBS will usually reveal no abnormality of the gastrointestinal tract. Thus, a physician may diagnose IBS based on a patient’s symptoms. A medical history and physical examination can identify any other possible causes for the symptoms. Various imaging or lab tests may also be conducted to rule out other possible medical conditions.

No single cause for IBS has been identified, although diet, stress and anxiety appear to play a role in triggering symptoms in patients with the condition. IBS symptoms may also be aggravated by certain medications or during a woman’s menstrual period. 

There is no cure for IBS, so treatment consists of controlling its symptoms. Various medications can be used to prevent or lessen symptoms. Avoiding particular foods that aggravate IBS symptoms is a common treatment strategy. For example, large meals, alcohol, chocolate, dairy products and caffeinated beverages should be avoided since they can cause diarrhea. Carbonated beverages and chewing gum should also be avoided since they can cause gas and bloating. On the other hand, adding adequate amounts of fiber to the diet can help to alleviate the constipation, and certain kinds of fiber can help to alleviate the diarrhea associated with IBS.  

Activities that reduce stress levels may also help prevent IBS symptoms. These include using relaxation techniques, getting regular exercise and adequate sleep, as well as receiving emotional support through the help of a mental health professional, family members and/or friends.

IBS can affect a person’s quality of life. The severity of symptoms can range from mild and inconvenient to severe and debilitating. IBS may affect a person’s physical functioning and ability to participate in daily activities. Most patients with IBS are able to control their symptoms through a combination of diet, stress management and medication.

IBS is not related to inflammatory bowel diseases that damage the digestive tract, such as Crohn’s disease or ulcerative colitis.

It can, however, affect a person’s quality of life. The severity of symptoms can range from mild and inconvenient to severe and debilitating. IBS may affect a person’s physical functioning and ability to participate in daily activities. Most patients with IBS are able to control their symptoms through a combination of diet, stress management or medication.

It is important to note that the manufacturer of the prescription medication tegaserod maleate (Zelnorn), which was indicated for use in women with constipation-predominant IBS, agreed to discontinue marketing the drug in March 2007 due to a high incidence of adverse cardiovascular events. Patients currently taking this medication are urged to consult their physician. However, select individuals who do not respond to any other form of treatment may be able to continue taking the medication under a restricted access program.