Definition/General
Introduction:
Tuberculous colitis is chronic granulomatous inflammation of the colon caused by Mycobacterium tuberculosis
Common in endemic areas including India
Shows epithelioid granulomas and caseating necrosis
Important differential for Crohn disease in endemic regions.
Origin:
Caused by Mycobacterium tuberculosis complex
Results from hematogenous spread or direct extension from pulmonary TB
Shows ileocecal predilection
Demonstrates chronic granulomatous inflammation
Associated with systemic tuberculosis in 50-80% cases.
Classification:
Primary gastrointestinal tuberculosis (no pulmonary involvement)
Secondary GI tuberculosis (with pulmonary TB)
Ulcerative type (transverse ulcers)
Hypertrophic type (mass-like lesions)
Ulcerohypertrophic type (mixed pattern).
Epidemiology:
High incidence in developing countries
India has highest burden globally
Peak incidence in young adults (20-40 years)
Male predominance
Associated with HIV infection
Malnutrition and immunosuppression risk factors.
Clinical Features
Presentation:
Chronic abdominal pain (right lower quadrant)
Diarrhea (with or without bleeding)
Weight loss and anorexia
Low-grade fever
Night sweats
Palpable mass (ileocecal region).
Symptoms:
Crampy abdominal pain (80-90% cases)
Chronic diarrhea (alternating with constipation)
Constitutional symptoms (fever, weight loss)
Rectal bleeding (30-50% cases)
Intestinal obstruction
Perianal involvement rare.
Risk Factors:
Living in endemic areas
HIV infection
Immunosuppression
Malnutrition
Diabetes mellitus
Contact with TB patients
Overcrowding
Poor socioeconomic conditions.
Screening:
Tuberculin skin test
Interferon-gamma release assays
Chest radiography
CT scan (abdomen)
Colonoscopy with biopsy
Acid-fast staining
PCR for TB.
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Gross Description
Appearance:
Transverse ulcers (characteristic)
Thickened bowel wall
Strictures and adhesions
Mass-like lesions (hypertrophic type)
Perforation (complications)
Lymph node enlargement.
Characteristics:
Circumferential ulceration
Nodular mucosa
Fibrous strictures
Serosal adhesions
Caseating lymph nodes
Fistula formation
Perforation sites.
Size Location:
Ileocecal region (90% cases)
Terminal ileum and cecum most common
Ascending colon
Pan-colonic involvement (rare)
Rectal involvement uncommon
Skip lesions possible.
Multifocality:
Ileocecal predominance
Segmental involvement
Skip areas between lesions
Multiple strictures
Associated small bowel involvement
Lymph node involvement common.
Microscopic Description
Histological Features:
Epithelioid granulomas with caseating necrosis
Langhans giant cells
Acid-fast bacilli (variable)
Mucosal ulceration
Chronic inflammation
Fibrosis and stricture formation.
Cellular Characteristics:
Epithelioid cells (activated macrophages)
Langhans giant cells (peripheral nuclei)
Lymphocytes and plasma cells
Caseating necrosis (central)
Fibroblasts and fibrous tissue.
Architectural Patterns:
Confluent granulomas
Transmural involvement
Submucosal granulomas
Mucosal ulceration with granulation tissue
Crypt destruction
Fibrosis and scarring.
Grading Criteria:
No specific grading
Assessment of granulomas (number, distribution)
Degree of caseation
Extent of fibrosis
Presence of AFB
Activity assessment (ulceration, inflammation).
Immunohistochemistry
Positive Markers:
CD68 (macrophages/epithelioid cells)
CD3 (T lymphocytes)
Anti-TB antibodies (when available)
Lysozyme (epithelioid cells)
Alpha-1-antitrypsin (macrophages).
Negative Markers:
Cytokeratin (granulomas)
CD20 (within granulomas)
S-100 (granulomas)
Specific tumor markers
Other mycobacterial antigens.
Diagnostic Utility:
Confirms granulomatous inflammation
Differentiates from malignancy
TB antigen detection (when available)
Excludes other granulomatous diseases
Usually morphology sufficient.
Molecular Subtypes:
M
tuberculosis complex
Drug-sensitive strains
Multi-drug resistant TB (MDR-TB)
Extensively drug-resistant TB (XDR-TB)
HIV-associated TB.
Molecular/Genetic
Genetic Mutations:
M
tuberculosis resistance genes (rpoB, katG, inhA)
Host susceptibility genes
HLA associations
Cytokine gene polymorphisms
Vitamin D receptor genes.
Molecular Markers:
IS6110 insertion sequence
16S rRNA
65 kDa heat shock protein
MPB64 antigen
Interferon-γ
TNF-α.
Prognostic Significance:
Early diagnosis improves outcome
Drug resistance worsens prognosis
HIV coinfection poor prognostic factor
Extent of disease
Nutritional status
Immune status.
Therapeutic Targets:
Anti-tubercular therapy (isoniazid, rifampin, ethambutol, pyrazinamide)
Duration 6-9 months
DOT strategy
Drug susceptibility testing
Surgical intervention (complications).
Differential Diagnosis
Similar Entities:
Crohn disease (most important differential)
Yersinia enterocolitis
Actinomycosis
Lymphoma
Adenocarcinoma
Other atypical mycobacteria.
Distinguishing Features:
Tuberculous colitis: Caseating granulomas, AFB, endemic area
Crohn disease: Non-caseating granulomas, younger age
Yersinia: Acute onset, organisms
Lymphoma: Monomorphic cells, markers
Adenocarcinoma: Dysplasia, malignant cells.
Diagnostic Challenges:
Distinguishing from Crohn disease (major challenge in endemic areas)
Identifying AFB (often scanty)
Recognizing complications
Correlating with clinical findings
Culture confirmation ideal.
Rare Variants:
Primary colonic tuberculosis
Atypical mycobacterial colitis
Tuberculous proctitis
Perianal tuberculosis
Tuberculous peritonitis.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
[specimen type] from [anatomical location]
Clinical Information
Clinical suspicion: [tuberculosis]. Systemic TB: [yes/no/unknown]
Granulomatous Features
Epithelioid granulomas: [present/absent]. Caseating necrosis: [present/absent]. Giant cells: [Langhans type/other]
Special Stains
Acid-fast staining: [positive/negative]. Organisms identified: [yes/no]
Inflammatory Features
Chronic inflammation: [present/absent]. Mucosal ulceration: [present/absent]
Differential Diagnosis
Features favor tuberculosis over Crohn disease: [caseating granulomas, AFB positivity]
Recommendations
Culture for mycobacteria recommended. PCR for TB may be helpful. Clinical correlation advised.
Final Diagnosis
Chronic granulomatous colitis, consistent with tuberculous colitis