Endobronchial Tuberculosis (10 Marks)

Definition and Introduction

Epidemiology

• Prevalence in autopsy studies: 3% to 72%; most series report ~40%.
• Prevalence in bronchoscopic studies: 10%-20% of active TB patients (older studies); lower in recent studies due to timely chemotherapy.
• In non-endemic areas, current prevalence may be as low as 0.18%.
• Most common in 21-40 years of age, though also seen in the elderly.
• Female preponderance - attributed to voluntary cough suppression for socio-cultural reasons, allowing sputum implantation into airways; smaller airway calibre in women also contributes.

Pathophysiology - Mechanisms of Endobronchial Infection

1. Direct extension from the lung - bronchi adjacent to infected lung parenchyma are directly involved; tracheobronchial ulceration is more common near extensive parenchymal TB.
2. Implantation from infected sputum - organisms from cavities are deposited onto the bronchial mucosa; the contralateral bronchial wall at the opening of a diseased lobe is typically affected.
3. Haematogenous dissemination - uncommon; rarely described in miliary TB.
4. Lymphatic spread - retrograde passage of tubercle bacilli through lymphatics from bronchioles upward; however, Auerbach's data suggests this is not a common mechanism.
5. As part of primary infection - lymph node erosion into a bronchus; the inflamed lymph node attaches to the bronchial wall and infects the mucosal lining. This mechanism predominantly occurs in children.

Pathology

• Earliest sign: erythematous mucous membranes.
• Discrete tubercles → shallow ulcers → deep ulcers involving the bronchial wall.
• Extensive granulation tissue may form a tumour-like mass mimicking a neoplasm.
• Healing leads to fibrosis and bronchial stenosis (also from oedema or extrinsic lymph node compression).
• Ulcers are 1-5 mm, long axis parallel to cartilaginous rings; more common near the carina and the posterior surface.

• Early: small oval/round epithelioid granulomas (with or without caseation) in the subepithelial region and around mucous glands.
• Advanced: foci extend to adventitia; cartilage involvement occurs only in very extensive cases.
• Rupture of submucosal foci → ulceration → granulation tissue with fibrin pseudomembrane → healing by connective tissue replacement → stenosis if circumferential.

Clinical Features

• In adults: may occur in primary or reactivation TB.
• In children: usually a complication of primary TB.
• Barking cough - most common symptom.
• Dyspnoea, chest pain, fever, weight loss, haemoptysis.
• Localised fixed wheeze (low-pitched, constantly present over the same area) - characteristic.
• Bronchorrhea (>500 mL/day) - rare.
• Presentations include: acute respiratory failure, subacute mimicking asthma/pneumonia/foreign body aspiration, or insidious mimicking lung cancer.
• Unusual findings: expectoration of bronchial cartilages, right-left main bronchi fistula.
• Symptoms may appear years after treatment of pulmonary TB.

Investigations

Sputum Examination

Chest Radiograph

• 10%-20% may have a normal chest radiograph.
• Findings: patchy infiltrates, collapse (25%-35%), consolidation (35%-60%), hyperinflation, cavities, pleural effusion, miliary infiltrates, mediastinal lymphadenopathy.

CT Chest

• Tree-in-bud pattern (centrilobular nodules connected to branching linear opacities) - reflects plugging of small airways with mucus/pus, dilated bronchioles, and peribronchiolar inflammation.
• Stenosis or obstruction of major airways; peribronchial soft tissue cuff.
• Active stage: irregular, circumferential luminal narrowing.
• Fibrotic stage: smooth or irregular narrowing with less wall thickening.
• Enlarged lymph nodes, segmental collapse, cavities, mucoid impaction.
• CT is inaccurate in distinguishing endobronchial, submucosal, or extrinsic disease.
• Cannot reliably differentiate from bronchogenic carcinoma - bronchoscopy is ultimately needed.

Spirometry

Bronchoscopy - Gold Standard

• TB suspects with three negative smears.
• Diagnosed TB with refractory cough, localised wheeze, persistent dyspnoea, diminished breath sounds, radiographic atelectasis, or failure to respond to anti-TB treatment.

Seven Bronchoscopic Types (Chung and Lee Classification)

Differential Diagnosis

• Bronchial asthma (most common misdiagnosis)
• Lung cancer / bronchogenic carcinoma
• Foreign body aspiration (especially in children)
• Atypical mycobacterial infection, sarcoidosis, actinomycosis, papillomatosis
• Wegener's granulomatosis, relapsing polychondritis, amyloidosis, rhinoscleroma
• Anthracofibrosis (non-smoking elderly women exposed to biomass fuel; co-exists with TB but spares central airways)

Treatment

1. Anti-TB Chemotherapy

2. Corticosteroids

• Used empirically to suppress barking cough.
• No strong evidence that corticosteroids prevent bronchostenosis (one RCT in adults showed no benefit).
• May be beneficial in children with lymph node TB causing bronchial obstruction (small double-blind studies).
• Not recommended for routine use.

3. Bronchoscopic Interventions (for airway stenosis)

• Mechanical dilatation: balloon bronchoplasty (radial force, less mucosal trauma; useful for short stenotic segments).
• Debulking: rigid bronchoscope; curettage with forceps.
• Thermal debulking: electrocautery, Argon Plasma Coagulation (APC) - FiO₂ must be <40%; effective in symptomatic obstruction.
• Nd-YAG / CO₂ Laser: Nd-YAG preferred (tissue vaporisation + coagulation); FiO₂ <40%.
• Cryotherapy: freeze-thaw cycles; safe (cartilage is cryoresistant); no airway fire risk.
• Airway stents:
  • Silicon stents: preferred; require rigid bronchoscopy; higher migration but easier to remove.
  • Metal stents: should be avoided (FDA black-box warning 2005 for benign stenosis); granulation tissue ingrowth, difficult to remove, frequent complications.
  • Hybrid (covered metal) stents: prevent ingrowth but higher migration.
  • Stents kept for 6-18 months in benign stenosis.

4. Surgery

• Sleeve resection (bronchoplasty with end-to-end anastomosis) - low mortality with modern techniques.
• Lobectomy for lobar/segmental bronchi involvement.
• Pneumonectomy as last resort for extensive bronchiectasis or completely obliterated main-stem bronchus.
• Ideally performed when active disease is no longer present.

Special Situations

• Children: incidence 40%-60%; primarily from lymph node erosion into bronchus; most common bronchoscopic finding is extrinsic compression; corticosteroids show some benefit.
• Elderly: at least 15%; often diagnosed during work-up for lung cancer; 60% develop bronchial stenosis.
• HIV: tumorous form more common (due to lymph node erosion); progressive bronchostenosis not commonly reported.
• Pregnancy: hormonal/vascular changes worsen airway stenosis; Heliox (79% He + 21% O₂) can reduce work of breathing; airway intervention preferably earlier in pregnancy.
• IRIS: paradoxical worsening; endobronchial extension of inflamed mediastinal lymph nodes in HIV-positive patients on ART.

Key Points for Exam

• EBTB is underdiagnosed because 10%-20% have normal CXR and sputum smear yield is only 15%-20%.
• Bronchoscopy is the gold standard and is both diagnostic and prognostic.
• Fibrostenosis is the most feared complication (occurs in 50%-90% despite therapy).
• Most common form: actively caseating; worst prognosis: tumourous type.
• Risk factors for persistent airway stenosis: age >45 years, anti-TB treatment delayed >90 days after initial symptoms.
• Multidisciplinary approach (interventional pulmonologist, thoracic surgeon, radiologist, TB specialist) is ideal.

1. Bronchostenosis / Bronchial stenosis - most significant complication (50%-90% despite effective therapy)
2. Atelectasis / Lung collapse
3. Bronchiectasis
4. Post-obstructive pneumonia
5. Lung abscess
6. Obstructive emphysema / Hyperinflation
7. Respiratory failure
8. Tension pneumothorax (from partial obstruction acting as one-way valve)
9. Tracheostomy / difficult endotracheal intubation (from tracheal stenosis)
10. Death by suffocation (from severe tracheal stenosis)
11. Pseudomembranous tracheobronchial aspergillosis (on stenotic area)
12. Fistula formation (between right and left main bronchi)
13. Expectoration of bronchial cartilages
14. Tract TB - concomitant intestinal and laryngeal involvement (Auerbach)