Tuberculosis

The disease caused by Mycobacterium tuberculosis

Presentation

• Wide spectrum of disease - asymptomatic to severe, active

Pathophysiology

• Transmitted by aerosol droplets, leading to one of two responses:
  • Immediate clearance of the organism
  • TB infection (previously called latent TB)
• TB infection
  • Tuberculous bacilli proliferate inside alveolar macrophages
  • A nodular granulomatous structure (tubercle) forms (seen as a Ghon focus radiologically)
  • The tubercle enlarges and bacilli enter the lymphatic drainage system, leading to lymphangitis and enlarged regional nodes
  • An effective cell-mediated response eventually develops in most patients, containing organisms
  • Caseous necrosis can be seen in this context
• Primary TB disease
  • Immediate onset of TB disease following exposure in a previously naïve host
  • Caused by failure to mount an effective response
  • Progressive tissue destruction - bacilli migrate away from lungs, producing disseminated TB
  • More common with immunosuppressed people
• Reactivation disease
  • Occurrence of TB after a period of clinical latency
  • Lifetime risk of 5-10%
  • Associated with HIV, organ transplant, silicosis, immunosuppressive drugs, diabetes, CKD
  • Tends to be localised to lung apices

Abdominal TB

• Can present with involvement of peritoneum, stomach, GIT, HPB, perianal area, and lymph nodes
• Can occur via reactivation of latent TB or by ingestion of bacilli, or can develop via miliary spread of active pulmonary TB
• Presents with fever, weight loss, abdominal pain/distension, ascites, hepatomegaly, diarrhoea, WBO, and abdominal mass
• GIT: most commonly ileocaecal.
• Management:
  • Anti-tuberculous therapy (same as pulmonary TB)
  • Surgical indications:
    • Perforation
    • Abscess
    • Fistula
    • Bleeding
    • High-grade obstruction (most common)
  • Surgery should be as conservative as possible. Bypass should be avoided due to blind loop syndrome.

Scrofula/tuberculous lymphadenitis

• One of the most common extrapulmonary manifestations of TB - responsible for about 40% of lymphadenopathy in third-world countries
• Treat with multidrug antimycobacterial therapy - often two months of rifampicin, isoniazid, ethambutol and pyrazinamide

Complications

• Haemoptysis
• Pneumothorax
• Bronchiectasis
• Broncholithiasis
• Extensive pulmonary destruction
• Respiratory failure
• Septic shock
• Malignancy
• VTE
• Chronic pulmonary aspergillosis