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Crohn's Disease

Definition

Crohn's disease is an inflammatory disease of the gastrointestinal tract, which may involve separated segments, or portions of the entire gastrointestinal tract from mouth to anus. These two features set Crohn's disease squarely apart from ulcerative colitis in which only the colon is affected and the disease process is Crohn's disease.

The typical site of disease is the terminal ileum, with the next common areas being the terminal ileum and cecum, followed by involvement of the colon alone. It is not unusual to have significant skipping of bowel between segments of disease.

Clinical manifestations

In Crohn's disease, the major pathology is submucosal in location, and the process becomes transmural early on. The surface is involved later in the course of the disease. Thus the typical symptoms include pain as the lumen of the gut becomes narrowed by the fibrosing and stricturing outcome of the inflammation. Fever and diarrhea are noted, but bleeding is less common. Prior

Systemic manifestations

The systemic manifestations in Crohn's disease are the same as those noted in ulcerative colitis. Thus, uveitis, sclerosing cholangitis, pyoderma gangrenosum, erythema nodosum, arthritis, sacroiliac disease, ankylosing spondylitis, liver disease are noted in Crohn's disease.

Diagnosis

The diagnosis is made on the basis of clinical and pathologic criteria. Because the mucosa may not be immediately involved, it may at times be difficult to make this diagnosis. The hallmark of the pathology is the granuloma which is non-caseating, and may be noted anywhere in the gut and may be seen in up to 50% of patients. It is possible to see the granuloma even in areas of normal looking mucosa. The inflammation is transmural and is responsible for the classic manifestations of the disease: narrowing of the lumen, and development of fistulas. Deep fissures are

Evaluation of the colon by direct endoscopy may show the typical skip lesions, sparing of the rectum, and the characteristic aphthous ulcer. As the aphthous ulcer gets bigger it can coalesce into longitudinal ulcers. These can aggregate and create the pattern of cobblestones. The colonoscope can be inserted into the terminal ileum for a direct look and to obtain biopsies. Barium x

Treatment Strategies in Crohn's disease

The general principles of treatment for Crohn's disease are the same as those outlined for ulcerative colitis. The specific differences deal with the use of Pentasa as the 5-ASA of choice in small bowel Crohn's since this is the only drug designed to release the active ASA in the small bowel and not in the colon. 6-mercaptopurine has been used extensively in Crohn's but it must be remembered that it has a 2-4 month lag between the initiation of therapy and the onset of a beneficial effect. This means that it is not useful to treat an acute episode of the disease, but is

Metronidazole may have a special role in the treatment of Crohn's disease. It has been especially useful in the treatment of fistulous disease. Vitamin E in doses of 800 units per day has been used as part of the treatment strategy in both ulcerative colitis and Crohn's.

Lymphocytic colitis is a poorly understood condition in which patients present with diarrhea as the major clinical manifestation. Biopsy of the colon shows the epithelial cell layer to be infiltrated by lymphocytes. In most instances the disease is self limited and treatment with sulfasalazine may be effective in decreasing the symptoms. There may be an association with celiac

Collagenous colitis is another variant in which diarrhea is the presenting complaint. In this condition, there is no important inflammation. Biopsy of the colon shows a greatly thickened collagen layer just below the epithelial cells. It is not understood how this layer of collagen results in the diarrhea characteristic of this condition. There is no specific treatment and again there is frequently a limited course.