Inflammatory bowel disease. Computer artwork of an ulcerated (yellow) intestine. Inflammatory bowel disease causes inflammation, ulceration and thickening of the intestinal lining. Symptoms include diarrhoea, abdominal pain and malabsorption of food leading to weight loss. The two most common types of inflammatory bowel disease are Crohn's disease and ulcerative colitis. The cause of inflammatory bowel disease is unknown. Treatment is with anti-inflammatory drugs and antibiotics. In some cases surgery to remove part of the intestines is needed.