(krōn)

[Burrill B. Crohn, U.S. gastroenterologist, 1884-1983]
ABBR: CD An inflammatory bowel disease marked by patchy areas of full-thickness inflammation anywhere in the gastrointestinal (GI) tract, from the mouth to the anus. It frequently involves the terminal ileum of the small intestine or the proximal large intestine.
SEE: regional enteritis; SEE: regional ileitis
SEE: inflammatory bowel disease;
SEE:

INCIDENCE
In the U.S., the incidence of CD is greater than 10 per 100,000. Like ulcerative colitis, the disease typically presents in the second or third decade of life.

CAUSES
Although the cause of CD is unknown, one identified risk factor is tobacco use.

SYMPTOMS AND SIGNS
Initial symptoms include mild, nonbloody diarrhea (three to five semisoft stools per day); fatigue; anorexia; and vague, intermittent abdominal pain. As the disease progresses, the symptoms include abdominal pain (typically in the right lower quadrant); weight loss; more severe fatigue; and moderate fever. Some patients also report skin breakdown in the perineal and rectal areas.

DIAGNOSIS
The presence of calprotectin in stools (fecal calprotectin) reliably distinguishes Crohn disease from irritable bowel syndrome with diarrhea. An upper GI study with small bowel follow-through, barium enema, lower endoscopy, and biopsy of suspicious lesions are used to diagnose CD. Biopsies reveal granulomatous lesioning of the intestinal wall. The radiological or endoscopic appearance of the bowel in CD reveals discrete (segmental) involvement of the bowel rather than continuous bowel involvement (as is found in ulcerative colitis). Even with contemporary endoscopic and pathological evaluation, a small percentage of patients have “indeterminate colitis,” i.e., after extensive study it is uncertain whether the patients have CD, ulcerative colitis, or some other disease of the bowel. Blood tests should be done to rule out iron deficiency, malnutrition, and active inflammation, e.g., C-reactive protein. Stool cultures should be performed to exclude infectious colitis/dysentery.


Complications of CD include bowel strictures, obstructions, or fistulae.

TREATMENT
CD is not cured by contemporary medical therapy, rather, it can usually be controlled. 5-ASA compounds and steroids are used to encourage remission, but steroids alone do not sustain remission. Immune modulating agents (azathioprine, 6-mercaptopurine) can induce and sustain remission in many patients. Antibiotic therapy (metronidazole, ciprofloxacin) often can help manage disease that involves the colon. Antitumor necrosis factor inhibitors (infliximab/adalimumab) maintain remission, but recrudescence of TB infection is possible with these medications. Cytapheresis is used occasionally, e.g., in Japan. Nutritional support of the patient may be needed during flares of the disease. Surgical removal of diseased bowel segments is often followed by relapse and may result in malnutrition.

IMPACT ON HEALTH
About one in seven CD patients is incapacitated or disabled by the illness. Crohn disease that begins in childhood tends to be more difficult to treat than adult-onset disease

PATIENT CARE
When surgical intervention is needed to repair bowel perforation, obstruction, or massive bleeding, general patient care concerns apply.