Inflammatory bowel disease (IBD) comprises ulcerative colitis (UC), Crohn’s disease (CD), and IBD unclassified (IBD-U). IBD diagnoses require chronic inflammation in the GI tract and exclusion of other causes of inflammation, including infectious diseases, allergic diseases, vasculitis disorders, drugs, and primary immunodeficiency disorders. Accurate diagnosis of PIBD is based on a combination of history, physical examination, esophagogastroduodenoscopy, and ileocolonoscopy with histology and small bowel imaging. Investigations to exclude GI infections are mandatory. Diagnosis of PIBD in developing countries can be challenging due to limited facilities and a high prevalence of GI infections mimicking PIBD, including various bacteria, protozoa, fungi, and viruses. Initiation of immunosuppression and biologics for the treatment of presumptive diagnosis of IBD in individuals who are undiagnosed with infectious diseases could cause severe illness and dissemination of infection. In many developing countries, the prevalence of tuberculosis (TB) and intestinal amebiasis remains high, and both can mimic IBD. Investigations to exclude these two diseases are crucial for patients residing in the endemic area before diagnosing IBD.
Intestinal TB can mimic CD in both clinical presentations and endoscopic findings. Transverse ulcers, patulous IC valve, and isolated ileocecal involvement favor TB diagnosis, while longitudinal ulcers, cobblestoning, left-sided colonic lesions, luminal stricture, and fistula favor CD diagnosis. In a high endemic area, tuberculin skin test or interferon-gamma release assay, chest radiographs, and endoscopic biopsies for PCR for TB should be routinely performed in patients suspected of IBD. Histology of intestinal TB includes large and confluent granulomas, caseation necrosis, multinucleated giant cells, and absence of transmural crack and fissures (CD feature).
Intestinal amebiasis is caused by E. histolytica infection. Fulminant colitis and a liver abscess may develop after corticosteroid therapy. Stool antigen tests, stool PCR, or stool microscopy are typically used to diagnose intestinal amebiasis. Colonoscopic findings include discrete ulcerations, or flask-shaped ulcers, covered by exudate with skip area. Scrapings or biopsy specimens taken from the edge of ulcers may reveal cysts or trophozoites on microscopy.
In summary, many diseases mimic PIBD and should be excluded using careful clinical evaluation, relevant investigations, endoscopy, and histological examination.
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