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Updated: 12/26/06 02:17 PM |
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| HOME | HEAL | EDUCATE | RESEARCH | DIRECTORY | OUTREACH |
Authors: D.R. Saunders, C.E. Rubin, and J.D. Ostrow
Download Chapter ♦ Download Lecture Slides & Notes
Download Chapter ♦ Download Lecture Slides & Notes
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V. Crohn’s Disease
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| Crohn's disease involves all layers of the intestinal wall |
Dr. Crohn of New York in 1932 described 52 patients who had thickened bowel, and enlarged mesenteric lymph nodes. The disease can affect any area of the Gl tract, but because it often involves the lower ileum, it is sometimes referred to as regional ileitis.
Diseased bowel is firm, and often narrowed like a rubber hose. There are often intervening areas of normal-appearing bowel. Several coils of intestine may be bound together by adhesions. Fistulous connections can form between bowel segments, between bowel and bladder, or skin. Intraabdominal abscesses are common. The adjacent mesentery is thickened and the lymph nodes are enlarged. Mesenteric fat creeps around the bowel wall towards the antimesenteric border. The intestinal mucosa is red, swollen, and ulcerated. Long ulcerations may intersect so that the surviving mucosa has the appearance of cobblestones. |
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| All layers of gut wall are involved. Granulomas are often present |
Microscopically, an acute and chronic inflammatory process involves all layers of the intestinal wall. In about half the cases, there are granulomas (focal collections of epithelioid cells, lymphocytes, and giant cells). There is no caseous necrosis, however, as in the tuberculous granuloma.
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Abnormal immune responses in gut Genetic susceptibility Cytokine TNF is a key mediator |
No pathogen has yet been found. We know that something in chyme (food particles, or bacteria, or both) incites an inflammatory reaction in the intestine wall of susceptible humans. Disturbances of the patient's immune system can be found such as circulating immune complexes, anergy, or reduction in T-lymphocyte counts, but these changes may be a response to the intestinal inflammation rather than a cause. In 2001, a breakthrough (discovery of a Crohn’s disease susceptibility gene, CARD 15) established a definite role for genetics in this disease. Increased understanding about inflammation is resulting in novel therapies for Crohn’s disease. Tumor necrosis factor (TNF) is a proinflammatory cytokine that seems to play a role in the pathogenesis. Genetically engineered proteins, given parenterally to block the effects of intestinal TNF, can improve the condition of patients whose disease is refractory to standard therapy.
Smoking tobacco increases susceptibility, and it is detrimental to the course of Crohn’s disease. |
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| Crohn’s disease often predominantly affects one region of the lower bowel |
Clinically, Crohn's disease has varied presentations depending on the site in the intestinal tract which is most afflicted. In general, there are two groups of patients. The first group of patients has disease of the ileum or right colon. Pain in the right lower quadrant often leads to a mistaken diagnosis of appendicitis and an appendectomy. Malabsorption of vitamin B12 and bile salts can occur if the ileum is extensively diseased. The second group of patients, whose disease predominates in the left colon and rectum, frequently has perirectal abscesses and perianal fistulas. Rectovesical and rectovaginal fistulas may occur.
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