Differentiating Crohn’s disease from intestinal tuberculosis

Abstract

Differentiating Crohn’s disease (CD) and intestinal tuberculosis (ITB) has remained a dilemma for most of the clinicians in the developing world, which are endemic for ITB, and where the disease burden of inflammatory bowel disease is on the rise. Although, there are certain clinical (diarrhea/hematochezia/perianal disease common in CD; fever/night sweats common in ITB), endoscopic (longitudinal/aphthous ulcers common in CD; transverse ulcers/patulous ileocaecal valve common in ITB), histologic (caseating/confluent/large granuloma common in ITB; microgranuloma common in CD), microbiologic (positive stain/culture for acid fast-bacillus in ITB), radiologic (long segment involvement/comb sign/skip lesions common in CD; necrotic lymph node/contiguous ileocaecal involvement common in ITB), and serologic differences between CD and ITB, the only exclusive features are caseation necrosis on biopsy, positive smear for acid-fast bacillus (AFB) and/or AFB culture, and necrotic lymph node on cross-sectional imaging in ITB. However, these exclusive features are limited by poor sensitivity, and this has led to the development of multiple multi-parametric predictive models. These models are also limited by complex formulae, small sample size and lack of validation across other populations. Several new parameters have come up including the latest Bayesian meta-analysis, enumeration of peripheral blood T-regulatory cells, and updated computed tomography based predictive score. However, therapeutic anti-tubercular therapy (ATT) trial, and subsequent clinical and endoscopic response to ATT is still required in a significant proportion of patients to establish the diagnosis. Therapeutic ATT trial is associated with a delay in the diagnosis of CD, and there is a need for better modalities for improved differentiation and reduction in the need for ATT trial.

Keywords: Crohn's disease; Intestinal tuberculosis; Endoscopy; Computed tomographic enterography; Granuloma

Core tip: There is a constant challenge of differentiating Crohn’s disease (CD) from intestinal tuberculosis, especially with the increasing burden of inflammatory bowel disease in tuberculosis-endemic areas. Caseation necrosis on biopsy, positive acid-fast bacillus smear/culture, and necrotic lymph node on computed tomography (CT) are the only differentiating features with 100% specificity, though are limited by poor sensitivity. Multi-parametric models have their own limitations and a therapeutic trial of anti-tubercular therapy is often required. Upcoming markers include the latest Bayesian meta-analysis, enumeration of peripheral blood T-regulatory cells, and updated CT based predictive score. Therapeutic trial is associated with a delay in CD diagnosis, and better modalities/biomarkers are required for improved differentiation and reduction in the need for anti-tubercular therapy trial.