This 3D medical animation describes the symptoms of irritable bowel syndrome as well as possible factors that exacerbate IBS and common treatments for IBS. Irritable bowel syndrome, or IBS, is a chronic condition affecting your large intestine. The large intestine, also called the colon, absorbs water and nutrients from partially digested food moving through your digestive tract. With IBS, the muscular contractions of your colon are abnormal.