What is a close mimicker of abdominal tuberculosis (TB) in a patient with gastrointestinal symptoms and a history of abdominal issues?

Close Mimickers of Abdominal Tuberculosis

Crohn's disease is the most important and challenging mimicker of abdominal tuberculosis, particularly when involving the ileocecal region, and distinguishing between these two conditions is critical because misdiagnosis leads to catastrophic consequences—immunosuppressive therapy for presumed Crohn's can worsen tuberculosis, while prolonged anti-tubercular therapy in Crohn's disease causes fibrotic complications. 1, 2, 3

Primary Differential Diagnosis

Crohn's Disease - The Classic Mimicker

Crohn's disease mimics abdominal TB so closely that multiparametric scoring systems are required for differentiation. Both conditions present with:

• Ileocecal involvement (50-90% in TB, similar distribution in Crohn's) 2, 4
• Chronic abdominal pain, diarrhea, and weight loss 2, 4
• Granulomatous inflammation on histology 5, 6, 7
• Skip lesions and segmental involvement 6, 8

Key distinguishing features favoring tuberculosis:

• Night sweats and constitutional symptoms (fever in 70-84% of TB cases) 2, 4
• Transverse ulcers, patulous ileocecal valve, and pseudopolyps on colonoscopy 1
• Necrotic lymph nodes >20mm with peripheral enhancement and central hypodensity on CT 9
• Positive tuberculin skin test (though often negative in immunocompromised patients) 2, 4
• Concomitant pulmonary TB (though absent in 85% of abdominal TB cases) 1, 2

Key distinguishing features favoring Crohn's disease:

• Anorectal lesions, longitudinal ulcers, aphthous ulcers, and cobblestone appearance 1
• Relapsing-remitting course over years 4
• Elevated fecal calprotectin (useful for monitoring response) 4
• Absence of caseating granulomas on histology 3

Other Important Mimickers

Ischemic colitis can present identically to abdominal TB with acute abdominal pain and ileocecal involvement, but typically shows:

• Sharply defined segments at watershed territories (sigmoid to splenic flexure) 1
• Normal rectum with petechial hemorrhages 1
• Rapid resolution on serial examinations 1

Typhoid perforation mimics TB perforation but differs in:

• Acute presentation in week 3 of illness (versus subacute TB over weeks-months) 9
• Ileal/jejunal perforation sites (versus ileocecal predominance in TB) 9
• Positive blood/bone marrow culture for Salmonella 9

Gastrointestinal malignancy (particularly cecal adenocarcinoma) can mimic TB with:

• Ileocecal mass and obstruction 8
• Weight loss and constitutional symptoms 8
• Requires tissue diagnosis to differentiate 8

Diagnostic Algorithm for Differentiation

When abdominal TB is suspected, pursue this systematic approach:

1. Epidemiological assessment: Immigration from endemic areas (Asia, Africa), HIV/AIDS status, immunosuppression 2

2. Colonoscopy with multiple biopsies: Look for ulcer morphology (transverse vs longitudinal), ileocecal valve appearance, and anorectal lesions 1

3. CT abdomen with contrast: Evaluate lymph node characteristics (size >20mm, peripheral enhancement with central necrosis strongly suggests TB) 9

4. Histopathology: Search for caseating granulomas, acid-fast bacilli, and send tissue for mycobacterial culture 2, 5

5. If diagnosis remains uncertain in TB-endemic areas: Consider therapeutic trial of anti-tubercular therapy with objective monitoring at 2 months (early mucosal response on repeat endoscopy, resolution of ascites, declining fecal calprotectin) 2, 3

Critical Clinical Pitfalls

The most dangerous error is treating presumed Crohn's disease with immunosuppression when the patient actually has tuberculosis—this leads to fulminant TB progression and death. 5, 6 Multiple case reports document fatal outcomes from this misdiagnosis. 6

Conversely, prolonged anti-tubercular therapy in actual Crohn's disease causes fibrotic strictures and delays appropriate immunosuppressive treatment. 3

In immunocompromised patients (transplant recipients, HIV/AIDS), tuberculosis is one of the most common abdominal diseases and should be the primary consideration, especially 1-6 months post-transplant when immunosuppression is maximal. 1

Up to 85% of abdominal TB patients have no pulmonary involvement, so normal chest imaging does not exclude the diagnosis. 1, 2