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

Figure 1

Endoscopic images. A: Longitudinal ulcer in a patient with Crohn’s disease; B: Coblestoning in a patient with Crohn’s disease; C: Deep ileal ulcer in a patient with Crohn’s disease; D: Transverse ulcer with a stricture in a patient with intestinal tuberculosis; E: Ulcerated bulky ileocaecal valve in a patient with intestinal tuberculosis.

Figure 2

Colonic biopsy. A: Patchy distortion of crypt architecture (arrows) (× 40). B: Features of focal active cryptitis are noted (arrow) (× 200). C: Colonic biopsy in a case of Crohn’s disease shows pericrypt mucosal microgranuloma (arrow) (× 40). D: Ileal biopsy in a case of ileocaecal tuberculosis shows blunting of ileal villi with crypt branching (arrow) (× 100). E: Serosal confluent necrotizing epithelioid cell granulomas (arrows) were noted (× 40). F: Photomicrograph showing an epithelioid cell granuloma with central necrosis (arrow) and Langhan’s giant cells (× 200).

Figure 3

Coronal computed tomography images in patients with Crohn’s disease. A: Long segment ileal thickening; B: Mural stratification (arrow) and increased visceral fat (arrowhead); C: Comb sign; D: Axial computed tomography image in a patient with intestinal tuberculosis demonstrating short segment ileocaecal thickening (arrow) with necrotic lymph node (arrowhead); and E: Coronal magnetic resonance image in a patient with intestinal tuberculosis showing ileocaecal thickening (arrowhead) and necrotic lymph node (arrow).

Figure 4

Algorithm for following a patient on therapeutic anti-tubercular therapy trial. ATT: Anti-tubercular therapy; CD: Crohn’s disease; ITB: Intestinal tuberculosis.