A chronic inflammatory bowel disease which has a protracted, relapsing and remitting course. An autoimmune condition, it may last for several years. There are many similarities with ULCERATIVE COLITIS; sometimes it can be hard to differentiate between the two conditions. A crucial difference is that ulcerative colitis is confined to the colon (see INTESTINE), whereas Crohn's disease can affect any part of the gastrointestinal tract, including the mouth and anus. The sites most commonly affected in Crohn's disease (in order of frequency) are terminal ILEUM and right side of colon, just the colon, just the ileum and finally the ileum and JEJUNUM. The whole wall of the affected bowel is oedematous (see OEDEMA) and thickened, with deep ulcers a characteristic feature. Ulcers may even penetrate the bowel wall, with ABSCESSES and FISTULAS developing. Another unusual feature of the disease is the presence in the affected bowel lining of islands of normal tissue.
Crohn's disease is rare in the developing world, but in the Western world the incidence is increasing and is now 6–7 per 100,000 population. Around 80,000 people in the UK have the disorder with more than 4,000 new cases occurring annually. Commonly, Crohn's disease starts in young adults, but a second incidence surge occurs in people over 70 years of age. Both genetic and environmental factors are implicated in the disease – for example, if one identical twin develops the disease, the second twin stands a high chance of being affected; and 10 per cent of sufferers have a close relative with inflammatory bowel disease. Among environmental factors are low-residue, high-refined-sugar diets, and smoking.
Symptoms and signs of Crohn's disease depend on the site affected, but include abdominal pain, diarrhoea (sometimes bloody), ANOREXIA, weight loss, lethargy, malaise, ANAEMIA, and sore tongue and lips. An abdominal mass may be present. Complications can be severe, including life-threatening inflammation of the colon (which may cause TOXAEMIA), perforation of the colon and the development of fistulae between the bowel and other organs in the abdomen or pelvis. If Crohn's disease persists for a decade or more there is an increased risk of the victim developing colon cancer. Extensive investigations are usually necessary to diagnose the disease; these include blood tests, bacteriological studies, ENDOSCOPY and biopsy, and barium X-ray examinations.
As with ulcerative colitis, treatment is aimed primarily at controlling symptoms. Physicians, surgeons, radiologists and dietitians usually adopt a team approach, while counsellors and patient support groups are valuable adjuncts in a disease that is typically lifelong. Drug treatment is aimed at settling the acute phase and preventing relapses. CORTICOSTEROIDS, given rectally to the affected gut or orally, are used initially as are the MONOCLONAL ANTIBODY DRUGS infliximab or adalimumab and the effects carefully monitored. To maintain remission, other drugs may be given which affect the immune system, such as the immunosuppressant agent AZATHIOPRINE or mercaptopurine. Antidiarrhoeal drugs may occasionally be helpful but should not be taken during an acute phase.
Diet is important and professional guidance is advisable. Some patients respond to milk- or wheat-free diets, but the best course for most patients is to eat a well-balanced diet, avoiding items that the sufferer knows from experience are poorly tolerated. Cessation of smoking is essential. Of those patients with extensive disease, as many as 80 per cent may require surgery to alleviate symptoms: a section of affected gut may be removed or, as a life-saving measure, a bowel perforation dealt with (see COLITIS).