What causes crohn's
In the early part of the 20th century tuberculosis was a common cause of inflammation of the ileum. Dr Crohn identified some patients with inflammation in the ileum (ileitis) but could not find any evidence of tuberculosis. Suspecting that there must be some other infecting organism, he searched assiduously but could not find an infection causing the disease. Since then many have looked for an infection without success. While some hold to an infectious theory of causation, it is now commonly believed that it is not due to an infection.
There has been accumulation of evidence to show that genetic factors play a role. There is an increased occurrence in family members most marked in identical twins but not in dissimilar twins. There is no increase in spouses. There are at least 7 genes which have an association with the development of Crohn's. Grouping of more of these may be critical in determining the probability of developing the disease.
No one single agent has been identified as causing the disease. However, it is commonly accepted that environmental factors are important. It may be a toxin, a food, or even an acute infection which temporarily damages the lining of the bowel in persons with the collection of genes necessary to establish the immune reactions that are characteristic of Crohn's. Once established there is an immune reaction which is finely balanced to counteract a host of environmental factors including reactions to some foods, bacterial products, and to produce actions outside the bowel such as skin lesions, arthritis, etc.
How common is Crohn's disease?
The incidence is highest in white populations and low in black and Polynesian races. The incidence (the number of new cases diagnosed each year) is increasing, making the disease, formally considered to be rare, to be considered in people with chronic bowel symptoms. The incidence in New Zealand is thought to be greater than 1 in 10,000. The prevalence in New Zealand has not been calculated but is probably 1 in several thousand.
What is the natural history of Crohn's disease?
Crohn's is a chronic condition usually with exacerbations and remissions. Once the disease is established it is considered to be a life-long illness. Many patients will have variable periods of remission and a few can have very long remissions.
A number of complications can occur including anaemia, narrowing of the bowel (stricture), with a variable degree of obstruction, communications (fistula) between adjacent loops or the skin, or arthritis.
What symptoms can be expected with Crohn's disease?
The most common symptoms of Crohn's disease is abdominal pain, often in the right lower abdomen and with or without diarrhoea. Joint pains, loss of appetite, weight, and fever are common. Sores and abscesses may occur in the anal area. People with Crohn's frequently have recurring mouth ulcers.
How is Crohn's disease diagnosed?
Crohn's may be seen at any age but it appears most frequently during the third decade of life. It is said that men and women are equally affected but there is a change developing, with it occurring more frequently in women.
A thorough history and a physical examination will often raise the possibility of Crohn's. This will be followed by blood tests to determine if there is anaemia or other abnormalities and a test of faeces to exclude an infectious cause of diarrhoea.
A flexible tube examination of the large bowel and extending into the lower part of the small bowel may show inflammation, ulceration, and a generally thickened bowel wall. Small pieces of bowel lining are taken for examination under the microscope.
An x-ray examination of the large bowel will usually be done to show the extent and severity of the disease. These examinations will include an upper series (enteroclysis) and a lower series (barium enema). Barium is put in the bowel. The barium appears white on the x-ray giving a shadow showing inflammation and ulceration.
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