INFLAMMATORY BOWEL DISEASE (IBD)
Last Updated : 12/25/2010
Dr Sharad Shah
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Definition
Inflammatory bowel disease is a chronic condition where there is inflammation of the large and or small intestine without a definite cause, which has a tendency to recur. The commonest finding on sigmoidoscopy is edema, granularity, and tendency to bruise and bleed to touch.

Types of IBD
The various type of IBD are
- Ulcerative colitis (UC)
- Crohn's disease (CD)

Causes of Inflammatory bowel disease
The exact cause of IBD is not known. However are the pointers towards these hypothesis. It may be that, there is no single cause, and there may be more than one cause, acting in unison. The causes of IBD are:

IN ULCERATIVE COLITIS:
Infection: No specific organism is isolated in patients with UC but E.coli and its strains may be releasing certain enzymes and other products that may damage the colonic mucosa. Thus, E.coli strains isolated from UC patients showed that they released certain hemotropins and microtones as compared with patients with normal colon. It has been recently reported that in patients who recover from UC, the E.coli is adhered to colonic epithelial cells and can initiate damage.

Food allergy: It has been suggested that milk might exacerbate UC which has been shown by Trulous et al; it has observed that 20% of patients may benefit with a milk free diet. Many studies have shown an increased number of antibodies to milk proteins but not lgE antibodies.

Environmental: Apart from infectious agents and diet, there are other environmental factors that can cause IBD. They are:
- Smoking
- Oral contraceptions

Smoking: This increases the risk for Crohn's disease. Smoking has an effect on the colonic mucosa and on its mucus production. There is less mucous glycoprotein synthesized by non smoking patients as compared with smoking patients. Smoking alters the colonic mucosal blood flow and decreases mucosa permeability.

IN CROHN'S DISEASE
Infections: No specific organism has been isolated for Crohn's but now mycobacteria paratuberculosis has attracted attention. The PCR method has identified mycobacterial TB DNA in the intestinal tissue of Crohn's disease.

Diet: There are an array of antibodies against food antigens, such as milk proteins & bakers yeast in Crohn's disease patients. In another study it was found that titanium, presumably of dietary origin in the intestinal transmural inflammatory infiltration of CD patients and in the Peyers patches suggested that dietary products are capable of being incorporated in the internal milieu

Genetics: A week association has been found between Crohn's disease and HLA - A2, HLA-DR4, DR1-DQ5 and inverse correlation with HLA-A11 & HLA-DR3. Association of the Crohn's with genetic disease has also been used as an indirect evidence. The diseases are ankylosing spondylitis, tyrosine positive albinism and Turours syndrome. An increased incidence of chromosomal breaks has been found in Crohn's disease patients compared with normal suggesting that inherited chromosomal fragility may be a factor in CD

Immune System: The normal gut flora is capable of suppressing the inflammatory process in the gut, but in CD this domain - regulation method is lost and therefore there is an intense inflammatory process. The gut epithelial cells are dysregulated i.e. the normal intestinal epithelium contains MHC class II and HLA DR-DP, which are important in processing other antigens. This distribution is changed on GI tract more so in the gut (intestine) in CD patients. The cells which usually stimulate proliferation of T suppressor cells in fact stimulate proliferation of T-helper cells. It is these T-helper cells which stimulate the cascade of immense activation.

Psychosocial factors: They represent a combination of external & internal factors. However Crohn's is not considered as a major psychosomatic disease in etiology.



Contributor Information and Disclosures

Dr Sharad Shah
Consultant Gastroenterologist Ex Head Department of Gastroenterology, Sir J J Hospital & Grant Medical College Hon Gastroenterologist - Sir H N Hospital, Jaslok Hospital, Breach Candy Hospital, Mumbai


First Created : 2/23/2001

References

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