Crohn's Disease Diagnosis

What should be considered in the differential diagnosis of Crohn's Disease?

Infectious colitis is the most important clinical entity to consider. In the immuno-competent patient, a number of organisms may be responsible for infectious enterocolitis: Yersinia enterocolitica, shigellae, salmonellae, Campylobacter jejuni, Escherichia coli, Aeromonas hydrophila, Clostridium difficile, Entamoeba histolytica, and Giardia lamblia. In the immunocompromised patient, one must consider the diagnosis of intestinal tuberculosis and the various infectious etiologies responsible for the gay bowel syndrome and HIV-associated colitis. These organisms include Cryptosporidium sp., herpes simplex virus, cytomegalovirus, Isospora belli, Mycobacterium avium-intracellulare, Neisseria gonorrhoeae, and Chlamydia trachomatis.

Among the noninfectious diseases to consider in the differential diagnosis of Crohn's disease are intestinal lymphoma, diverticulitis, ischemic colitis, collagenous colitis, irritable bowel syndrome, eosinophilic gastroenteritis, and radiation enteritis. In patients presenting with initial onset of Crohn's disease, one must consider the diagnosis of acute appendicitis or acute Yersinia enterocolitis. When Crohn's disease is limited to the rectum or left colon, it must be differentiated from ulcerative colitis. Sometimes, typical ulcerative proctitis is recognized in patients with typical Crohn's disease involving the ileum or right colon.

What diagnostic steps should be taken for crohn's disease?

In addition to the history and physical findings, the diagnosis is based on objective evidence obtained from contrast radiography, endoscopic appearance, and mucosal biopsies. Barium radiography is the preferred method for evaluating the extent and severity of Crohn's disease in the upper GI tract. A baseline study of the upper GI tract, even in patients with quiescent disease or disease seemingly limited to the colon, is highly recommended. Typical early findings on barium studies include mucosal and submucosal edema and thickening of mucosal folds. Findings in patients with more advanced disease include mucosal erosions and linear ulcerations, cobblestoning of the mucosa, matting of bowel loops, pseudo diverticula, narrowing and stricturing of the bowel lumen, and various fistulae (enteroenteric, entero-colonic, enterovesical, enterovaginal, and enterocutaneous). Ultrasonography and CT scanning are useful in documenting and localizing suspected abscesses or intra-abdominal masses.

Endoscopy is useful in providing direct visualization of the intestinal mucosal inflammatory process, determining severity and distribution of disease, and identifying complications of disease (pseudopolyps, narrowing, strictures, and carcinoma). Typical endoscopic appearances may include mucosal edema, erythema, granularity, nodularity, cobblestoning, pseudopolyposis, mucopus, friability (bleeding on contact), ulcerations, luminal narrowing, and strictures. Colonoscopy is also extremely valuable in determining response to acute medical therapy. It is also used for surveillance of dysplasia and carcinoma transformation, as in ulcerative colitis.

Pathohistologic evaluation of surgical specimens and mucosal biopsies obtained during endoscopy may provide objective evidence to support a diagnosis of Crohn's disease. Grossly, the bowel wall appears thickened and stiff, with narrowing of the lumen. This occurs as a consequence of chronic transmural inflammation and the resulting fibrosis. In addition, there is extension of adipose tissue from the mesentery onto the serosal surface, which may result in the matting of loops of small bowel.

The most common pattern of colonic inflammation is that of rectal sparing, with skip areas of normal mucosa intervening between segments of diseased mucosa. Histologic examination usually reveals focal areas of acute, subacute, and chronic inflammation, with lymphoid hyperplasia and aggregates of lymphoid follicles within the submucosa and occasionally external to the muscularis propria, as well as thickening and shortening of intestinal villi. Superficial aphthous ulcerations, which may progress to deep linear longitudinal and transverse ulceration, are commonly encountered. Mucosal and sub-mucosal noncaseating granulomas are found in approximately 50 percent of pathologic specimens. Currently, this is the most specific pathologic feature supporting a diagnosis of Crohn's disease.

Last updated Jan 4/07