When first described in 1932 this idiopathic disorder was thought to be limited to the terminal ileum, hence the designation terminal ileitis. Recognition that sharply delineated bowel segment s might be affected, with intervening unaffected areas, led to the alternate name regional enteritis. Predominant involvement of the colon give raise to the term granulomatous colitis. It is now clear that any level of the alimentary tract may be involved and that there are systemic manifestations; thus the eponymic name crohn disease is preferred. When fully developed, crohn disease is characterized pathologically by (1) sharply delimited and typically transmural involvement of the bowelby an inflammatory process with mucosal damage, (2) the presence of noncaseating granulomas and (3) fissuring with formation of fistulas.



Epidemiology

Crohn disease occurs throughout the world but primarily in Western developed populations. Its annual incidence in the United States is around 3 per 100,000. It occurs at any age from young childhood to advanced age, but peak ages of detection aer the teens and twenties with a minor peak in the fifties and sixties. Females are affected slightly more often than males. Whites appear to develop the disease two to five times more often than do nonwhites. In the United States, Crohn disease occurs three to five times more often among jews than among non-jews. Smoking is a strong exogenous risk factor.

Clinical Features

The clinical manifestations of Crohn disease are extremely variable. The disease usually begins with intermittent attacks of relatively mild diarrhea, fever, and abdominal pain spaced by asymptomatic periods lasting for weeks to many months. Often the attacks are precipitated by periods of physical or emotional stress. In those with clonic involvement , occult or overt fecal blood loss may lead to anemia over the span of time but massive bleeding is uncommon. In about one fifth of patients, the onset is more abrupt with acute right lower quadrant pain fever and diarrhea sometimes suggesting acute appendicitis or an acute bowel perforation.

During the lengthy, chronic disease , complications may arise from fibrosing strictures, particularly of the terminal ileum and fistulas to other loops of bowel the urinary bladder or perinal skin or in to a peritoneal abscess. Extensive involvement of the small bowel including the terminal ileum, may cause marked loss of albumin (protein ? losing enteropathy), generalized malabsorption specific malabsorption of vitamin B12 or malabsorption of bile salts, leading steatorrhea.

Extraintestinal manifestations of this disease include migratory polyarthritis sacroiliitis , ankylosing spondylitis, erythema nodosum, or clubbing of the fingertips. Hepatic primary scelerosing cholangitis occurs, but the association is not as strong as in ulcerative colitis. Any of these manifestations can develop before onset of intestinal symptoms. Deranged systemic immunity is thought to undrly these related disorders. Uvitis, nonspecific mild hepatic pericholangitis, and renal disorders secondary to traping of the ureters in the inflammatory process sometimes develop.

There is an increased incidence of cancer of the gastro intestinal tract in patients with long standing progressive Crohn disease, representing fivefold to sixfold increased risk over age- matched populations. The risk of cancer in Crohn disease, however appears to be considerably less than that in patients with chronic ulcerative colitis.