bowel thickening. Small intestine The small intestine consists of the duodenum, jejunum and ileum. Inflammation of the small intestine is called enteritis, which if localised to just part is called duodenitis, jejunitis and ileitis, respectively. Peptic ulcers are also common in the duodenum. Chronic diseases of malabsorption may affect the small intestine, including the autoimmune coeliac disease, infective tropical sprue, and congenital or surgical short bowel syndrome. Other rarer diseases affecting the small intestine include Curling's ulcer, blind loop syndrome, Milroy disease and Whipple's disease. Tumours of the small intestine include gastrointestinal stromal tumours, lipomas, hamartomas and carcinoid syndromes. Diseases of the small intestine may present with symptoms such as diarrhoea, malnutrition, fatigue and weight loss. Investigations pursued may include blood tests to monitor nutrition, such as iron levels, folate and calcium, endoscopy and biopsy of the duodenum, and barium swallow. Treatments may include renutrition, and antibiotics for infections. Large intestine Diseases that affect the large intestine may affect it in whole or in part. Appendicitis is one such disease, caused by inflammation of the appendix. Generalised inflammation of the large intestine is referred to as colitis, which when caused by the bacteria Clostridium difficile is referred to as pseudomembranous colitis. Diverticulitis is a common cause of abdominal pain resulting from outpouchings that particularly affects the colon. Functional colonic diseases refer to disorders without a known cause, including irritable bowel syndrome and intestinal pseudoobstruction. Constipation may result from lifestyle factors, impaction of a rigid stool in the rectum, or in neonates, Hirschprung's disease. Diseases affecting the large intestine may cause blood to be passed with stool, may cause constipation, or may result in abdominal pain or a fever. Tests that specifically examine the function of the large intestine include barium swallows, abdominal x-rays, and colonoscopy. Rectum and anus Diseases affecting the rectum and anus are extremely common, especially in older adults. Hemorrhoids, vascular outpouchings of skin, are very common, as is pruritus ani, referring to anal itchiness. Other conditions, such as anal cancer may be associated with ulcerative colitis or with sexually transmitted infections such as HIV. Inflammation of the rectum is known as proctitis, one cause of which is radiation damage associated with radiotherapy to other sites such as the prostate. Faecal incontinence can result from mechanical and neurological problems, and when associated with a lack of voluntary voiding ability is described as encopresis. Pain on passing stool may