Irritable bowel syndrome (IBS) is a common disorder that affects the large intestine. Signs and symptoms include cramping, abdominal pain, bloating, gas, and diarrhea or constipation, or both. IBS is a chronic condition that you'll need to manage long term. Only a small number of people with IBS have severe signs and symptoms. Some people can control their symptoms by managing diet, lifestyle and stress. More-severe symptoms can be treated with medication and counseling.

Symptoms

The signs and symptoms of IBS vary. The most common include: Abdominal pain, cramping or bloating that is typically relieved or partially relieved by passing a bowel movement, Excess gas, Diarrhea or constipation — sometimes alternating bouts of diarrhea and constipation, Mucus in the stool Most people with IBS experience times when the signs and symptoms are worse and times when they improve or even disappear completely.

Causes

The precise cause of IBS isn't known. Factors that appear to play a role include: • Muscle contractions in the intestine. The walls of the intestines are lined with layers of muscle that contract as they move food through your digestive tract. Contractions that are stronger and last longer than normal can cause gas, bloating and diarrhea. Weak intestinal contractions can slow food passage and lead to hard, dry stools. • Nervous system. Abnormalities in the nerves in your digestive system may cause you to experience greater than normal discomfort when your abdomen stretches from gas or stool. Poorly coordinated signals between the brain and the intestines can cause your body to overreact to changes that normally occur in the digestive process, resulting in pain, diarrhea or constipation. • Inflammation in the intestines. Some people with IBS have an increased number of immune-system cells in their intestines. This immune-system response is associated with pain and diarrhea. • Severe infection. IBS can develop after a severe bout of diarrhea (gastroenteritis) caused by bacteria or a virus. IBS might also be associated with a surplus of bacteria in the intestines (bacterial overgrowth). • Changes in bacteria in the gut (microflora). Microflora are the "good" bacteria that reside in the intestines and play a key role in health. Research indicates that microflora in people with IBS might differ from microflora in healthy people.