What percentage of patients have an undetermined type of IBD with features of both Crohn disease and ulcerative colitis and what are other diagnostic considerations?

Updated: Jul 26, 2019
  • Author: Leyla J Ghazi, MD; Chief Editor: Praveen K Roy, MD, AGAF  more...
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Despite extensive workup, 15% of patients with isolated colitis have an undetermined type of IBD that shows features of both Crohn disease and ulcerative colitis. The distinction is often difficult to make, especially if the patient meets all diagnostic criteria for ulcerative colitis but is a smoker or has rectal sparing—features that suggest the possibility of Crohn disease or IBD of undetermined type.

In addition, there is a subpopulation of patients with Crohn colitis who will not develop small bowel disease in their lifetime. This group represents approximately 20% of the colitis patients.

Tuberculosis is also in the differential diagnosis of Crohn disease. Simple clinical findings (eg, fever, rectal bleeding, diarrhea, symptomatic duration) appear to be most accurate for differentiating Crohn disease from intestinal tuberculosis. [57] Anti–Saccharomyces cerevisiae antibodies (ASCA) do not help in differentiating small bowel tuberculosis from small bowel Crohn disease, but if both ASCA and interferon-gamma release assays are available and the ASCA result is positive, while the interferon gamma release assay result is negative, the specificity for Crohn disease is high, particularly in Asian populations. [57] Endoscopy in combination with radiologic and laboratory findings are also useful for differentiating between Crohn disease and intestinal tuberculosis.

In addition to excluding ulcerative colitis and intestinal tuberculosis, guidelines from the World Gastroenterology Organization recommend ruling out the following in the differential diagnoses of Crohn disease [58, 57] :

  • Behςet disease

  • Celiac disease

  • Irritable bowel syndrome (IBS) (if inflammatory changes are present, it is not IBS)

  • Nonsteroidal anti-inflammatory drug (NSAID) enteropathy

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