Question

How can Crohn’s disease be differentiated from gastrointestinal tuberculosis on imaging?

Hint:

Mesenteric lymphadenopathy and asymmetrical bowel wall thickening are more indicative of gastrointestinal tuberculosis, whereas Crohn’s disease tends to have a more segmental, transmural, and irregular pattern.

Answer 1

Step 1: Overview of Differentiation.
Crohn’s disease and gastrointestinal tuberculosis (GI T can present with similar symptoms and imaging findings, making differentiation challenging. However, certain radiological features can help distinguish between the two conditions.
Step 2: Radiological Features of Crohn’s Disease vs GI Tuberculosis.
1. Location of Disease:
- Crohn’s disease: Can affect any part of the GI tract, but most commonly affects the terminal ileum and right colon. It is often segmental and involves the entire bowel wall (transmural).
- GI Tuberculosis: Often affects the ileocecal region, but can also involve the colon, particularly the ileocecal junction. The lesions tend to be more continuous and less segmental compared to Crohn’s disease.
2. Bowel Wall Thickening:
- Crohn’s disease: Wall thickening is typically concentric and circumferential, with associated fat stranding. It often leads to strictures and cobblestone appearance.
- GI Tuberculosis: Bowel wall thickening is often asymmetric and can show less pronounced fat stranding. It may show a more smooth, irregular pattern without strictures in early stages.
3. Mesenteric Lymphadenopathy:
- Crohn’s disease: Lymphadenopathy is usually absent or mild.
- GI Tuberculosis: Significant mesenteric lymphadenopathy is commonly seen on imaging, particularly in the ileocecal region. Enlarged lymph nodes may appear on CT or MRI.
4. Fistulas and Abscesses:
- Crohn’s disease: Fistulas, abscesses, and granulomas are common features, especially in the later stages of the disease.
- GI Tuberculosis: Fistulas are less common, and abscesses typically develop later in the disease course.
5. Other Specific Findings:
- Crohn’s disease: “String sign” due to strictures and visible inflammation of the bowel wall.
- GI Tuberculosis: Can show a “comma sign” or “apple core” sign, which represents a narrowing of the bowel lumen due to fibrosis and inflammation.
Step 3: Final Diagnosis.
- Endoscopy and Biopsy: While radiology helps in differentiating between Crohn’s disease and GI tuberculosis, endoscopy with biopsy is often required to confirm the diagnosis.
- Bacterial Cultures: For tuberculosis, culture of Mycobacterium tuberculosis from stool or tissue biopsy confirms the diagnosis.