IBS (irritable bowel syndrome) is a common gastrointestinal disorder involving an abnormal condition of gut contractions (motility) characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with alternating diarrhea and constipation, symptoms that tend to be chronic and to wax and wane over the years. Although IBS can cause chronic recurrent discomfort, it does not lead to any serious organ problems. Making the diagnosis usually involves excluding other illnesses. Treatment is directed toward relief of symptoms and includes changes in diet (eating high fiber and avoiding caffeine, milk products and sweeteners), exercise, relaxation techniques, and medications. Also called spastic colitis, mucus colitis, nervous colon syndrome.