G. I. TB

 Gastrointestinal TB

Gastrointestinal TB is uncommon, Various pathogenetic mechanisms are involved: swallowing of sputum with direct seeding, hematogenous spread, or (largely in developing areas) ingestion of milk from cows affected by bovine TB. Although any portion of the gastrointestinal tract may be affected, the terminal ileum and the cecum are the sites most commonly involved. Abdominal pain (similar to that associated with appendicitis) and swelling, obstruction, hematochezia(blood in stool) and a palpable mass in the abdomen are common findings at presentation. Fever, weight loss, anorexia, and night sweats are also common. With intestinal-wall involvement, ulcerations and fistulae may simulate Crohn's disease; the differential diagnosis with this entity is always difficult.

Tuberculous peritonitis follows either the direct spread of tubercle bacilli from ruptured lymph nodes and intraabdominal organs (e.g., genital TB in women) or hematogenous seeding. Nonspecific abdominal pain, fever, and ascites should raise the suspicion of tuberculous peritonitis. The coexistence of cirrhosis in patients with tuberculous peritonitis complicates the diagnosis. In tuberculous peritonitis, paracentesis reveals an exudative fluid with a high protein content and leukocytosis that is usually lymphocytic.

Clinical Profile and Risk Assessment

Presenting Features: Long-standing right lower abdominal pain, changes in bowel habit (obstructive symptoms or diarrhea), weight loss, low-grade pyrexia, night sweats, and sometimes gastrointestinal bleeding.

Physical Findings: Right iliac fossa mass on palpation or signs of partial intestinal obstruction.

Predisposing Factors: Residence in areas where TB is endemic, HIV, or other immunocompromised conditions, a history of pulmonary TB, and less frequently consumption of unpasteurized milk harboring M. bovis.

Associated Disease: Simultaneous pulmonary or peritoneal TB can be identified through chest imaging or fluid analysis.

  Laboratory Workup

Routine Tests: Normocytic anemia and elevated ESR or CRP are common but non-specific.

Tuberculin Skin Test , IGRA: Indication of exposure to TB, but not specific to gastrointestinal involvement.

Microbiological Evidence:

AFB Staining and Culture: Still the gold standard, but sensitivity in mucosal biopsies is low (<30–40%).

PCR for M. tuberculosis: Provides increased sensitivity; multiplex PCR for IS6110 and MPB64 increases specificity but may produce false positives from non-tuberculous mycobacteria.

   Radiologic Evaluation

  CT and MRI Findings

CECT or CT Enterography: Typical signs include asymmetric ileocecal wall thickening, retracted cecum, rim-enhancing necrotic lymph nodes, and peritoneal thickening.

MRI Enterography: Useful in the evaluation of detailed bowel wall and extraluminal complications when a reduction of radiation exposure is needed.

Key Differentiators

·         ITB: Short-segment disease, ileocecal predominance, necrotic nodes.

·         Crohn's disease: Long-segment or skip lesions, creeping fat, and common fistulas.

·         Endoscopy and Biopsy

·         Colonoscopy: Can show transverse ulcers with a ragged border, nodularity, deformed or patent ileocecal valve, and strictures.

·         Sampling: Deep biopsies in multiple numbers increase diagnostic yield; endoscopic ultrasound-guided FNAC of lymph nodes can add to confirmation.

  Histopathological Characteristics

Diagnostic Clues: Confluent, large, caseating granulomas with epithelioid  histiocytes and Langhans-type giant cells are strongly suggestive.

Quantitative Indicators: Submucosal granulomas >200 μm and >5 granulomas per high-power field suggest ITB instead of CD.

Additional Testing: Ziehl–Neelsen staining identifies AFB in only a minority; culture is still essential for drug-susceptibility testing.

  Differential Diagnosis

Aspect	ITB	Crohn’s Disease	Adenocarcinoma/Lymphoma
Location	Predominantly ileocecal	Ileum ± colon, skip lesions	Variable
Ulcer Orientation	Transverse	Longitudinal	Irregular masses
Lymph Node Pattern	Necrotic, rim-enhancing	Homogeneous	Firm, non-necrotic
Fistulization	Uncommon	Common	Rare
ATT Response	Marked improvement in 6–8 weeks	No specific response	No response

 

Other conditions  e.g., Yersinia enterocolitica infection, amebiasis, and Behçet's disease can also present as ITB but are differentiated by stool cultures, serology, or systemic signs.

 Trial of Therapy

When biopsy and microbiology are still not yielding evidence, a monitored course of ATT can be attempted. Significant symptom and imaging response within 6–8 weeks is highly suggestive of ITB. Malignancy must always be ruled out before such therapy.

 Multidisciplinary Collaboration

 Gastroenterologists: Carry out endoscopy and follow therapeutic response.

 Radiologists: Offer detailed cross-sectional imaging interpretation.

 Pathologists: Diagnosis of granulomatous features and histologic confirmation of TB.

 Infectious Disease Specialists: Evaluate pulmonary involvement and resistance patterns.

Conclusion

ITB diagnosis involves the combination of clinical suspicion with radiologic, endoscopic, histologic, and microbiologic information. Ulcer shape, lymph node morphology, granuloma type, and initial response to ATT are noted with attention to differentiate ITB from CD or malignancy. Coordination and multidisciplinary management reduce delays in diagnosis and maximize patient management.