Tuberculosis - Reactivation

Pathophysiology:  See Tuberculosis – Primary

Post primary tuberculosis is now felt to be largely reactivation of dormant foci of tubercle bacilli in the lungs or elsewhere.  True re-infection tuberculosis is far less common.

Occurs in situations of host susceptibility: genetic or in various host suppressed states: e.g. bad health habits (indigents), high risk geographic areas (far East, Africa, India etc…), immuno-compromised hosts (HIV), drug treatments (steroids, chemotherapy).

The dormant TB foci are most prevalent in the upper apices of the lungs (especially the apical and posterior segment) and during reactivation, an exudative hyperimmune pneumonia occurs.  This is characterized by tissue destruction, cavitation, airways involvement with bronchiectasis, and marked fibrosis including the pleural surfaces.

Clinical and Radiologic Clues:  Think tuberculosis! Commonest cause of failure to diagnose is the physician not thinking of tuberculosis!

Tuberculosis, especially post primary TB, is a great imposter mimicking many lung disease processes. Tuberculosis and sarcoidosis are classic “Aunt Sophies”.

CXR/CT Findings:

1. upper lung, apical, superior segment of lower lobe airspace disease; cavitary

2. calcified granulomata (small nodules)

3. calcified hilar lymph nodes

4. Ghon complex

5. Ranke complex

6. disease with fibrotic changes and architectural distortion

7. pleural fibrosis, hilar traction, traction of vessels and airways

8. pleural effusion

9. fibrothorax: any cause

10. bronchiectasis: upper lung, superior segment predilection

11. rarely may see regional adenopathy in re-activation TB

12. lung nodules and masses: may be non-specific but in upper lungs

13. pneumothorax, broncho-pleural fistula with pneumothorax

14. empyema: encysted pleural infection with Slit Pea Sign on CT

15. “tree and budding” on CT

16. skeletal tuberculosis: Pott’s disease, thoracic spine osteomyelitis, paralumbar masses

17. rarely: rib destruction and empyema leading to empyema necessitatis

“Aunt Sophies”:

1. granulomatous infections: fungal, atypical tuberculosis

2. granulomatous diseases: e.g. sarcoidosis stages III and IV; eosinophilic lung disease; end stage hypersensitivity alveolitis, silicosis

3. CAP: e.g. severe gram negative, mixed aerobic and anaerobic pneumonias and lung abscesses, Legionella pneumonia

4. COLD: complicated emphysema, bullous disease, bronchiectasis of any cause, cystic fibrosis

5. cavitary lung disease gamut: infections, tumours, vasculitis, pneumatoceles etc…

6. pleural effusions and fibrosis: infections, tumours, asbestos-related pleural disease and mesothelioma, hemothorax, causes of fibrothorax

7. miliary pattern (micronodular): fungal diseases, mycoplasma pneumonia, sarcoidosis, micronodular metastases (e.g. thyroid)