Irritable bowel syndrome (IBS) is a functional disorder. Even though the digestive tract looks normal, it doesn't always function as it should. Muscles in the intestines move food from the stomach to the rectum. Normally, they contract and relax in a gentle rhythm, which moves the food along in a fairly predictable schedule. But in some people, the intestinal muscles spasm. That means the contractions are longer and stronger than normal. Those spasms are painful. They also disrupt the movement of food through the intestines. If they slow it down, you become constipated. If they speed it up, you get diarrhea. It's not unusual for people with IBS to alternate between the two. Another cause of discomfort for people with IBS results from oversensitive nerve endings in their digestive tracts. Small bubbles of gas that wouldn't bother most people might be quite painful. This heightened sensitivity can also lead to a sense of swelling and bloating.

From Mayo Clinic to your inbox

Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health.

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

Sept. 27, 2018