Inflammatory condition of the large intestine. It can occur in episodes, such as irritable bowel syndrome, or it can be one of the more serious, chronic, progressive, inflammatory bowel diseases, such as ulcerative colitis. See Ulcerative colitis. Irritable bowel syndrome is characterized by bouts of colicky abdominal pain, bloating, diarrhea or constipation, and fatigue, often due to emotional stress. Treatment includes stress reduction, diet changes and sometimes medication.