IBS is a common digestive disorder that affects about 20% of people in the United States, mostly women. It affects how the large intestine (colon) works.
Food moving through the digestive tract passes from the small intestine to the colon. The main function of the colon is to absorb water. Muscles in the colon usually contract in a way that pushes stool (waste products) through. In IBS, these muscle contractions may be abnormal. Too many contractions may cause diarrhea. Slowed or fewer contractions may cause constipation. Irregular or intermittent (spasmodic) muscle contractions may cause pain or a feeling of urgent need to move the bowels (go to the bathroom).
The cause is unknown but appears to be related to the nervous system. People with IBS have a colon that reacts very strongly to signals from the brain. Many people find that stress, anxiety, and emotional upset trigger symptoms. Certain foods or eating too much or too little may also cause the colon to overreact.
The most common symptoms are pain in the abdomen (belly), bloating, and constipation or diarrhea or both. Other symptoms include an urgent need to move the bowels and feeling of incomplete evacuation. These symptoms come and go over days, weeks, or months.
Not everyone who has gastrointestinal symptoms has IBS. The health care provider diagnoses IBS by taking a careful medical history to detail the symptoms. No test can prove that someone has IBS. The health care provider may use blood tests, x-rays, and looking at the colon through a thin, flexible tube (special instrument called an endoscope) to rule out other disorders.
Lifestyle changes may help relieve IBS symptoms. These changes include eating a high-fiber diet, avoiding foods that make symptoms worse, eating regular meals that are not too big, drinking enough water, getting regular exercise, and reducing stress.
Several medicines are available for IBS. The health care provider can help decide which are best. Over-the-counter laxatives should be taken only under a doctor’s direction, because overuse of laxatives may be harmful. Tranquilizers and antidepressants may also help people with IBS.
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