• Most infected patients have a + PPD and a normal chest radiograph
  
• Primary tuberculosis: focal consolidation, lymphadenopathy and small effusion
  
• Reactivation TB: apical-dorsal cavities

Chest radiography

• Primary TB
  • Focal consolidation in any lobe, cavitation uncommon (10-30%)
    
  • Indolent, weeks to months to clear
    
  • Evolves into scar, calcified nodule (20%) or clears completely
    
  • Ipsilateral hilar adenopathy common
    
  • Pleural effusion (25%); usually unilateral and small
    
  • Healed pneumonia results in calcified lung nodule (Ghon lesion) and calcified ipsilateral lymph nodes (Ranke complex)
• Reactivation TB
  • Patchy subsegmental consolidation located in apical/posterior segments of upper lobes, and superior segments of lower lobes
    
  • Bilateral, right apex more severe than left
    
  • Cavitation, with or without air fluid levels
    
  • Pneumothorax uncommon
    
  • Bronchogenic spread: Intrabronchial spread of cavity contents
• Miliary TB
  • 2-3mm nodules may be missed with chest radiography
  • As nodules enlarge, become larger in upper lung zones
• HIV and TB
  • CD4 count < 200/mm3 primary TB pattern
  • CD4 count > 200/mm3, reactivation TB pattern
    

CT/HRCT

• Bronchogenic spread
  • Peribronchial patchy opacities or centrilobular rosettes
  • Tree-in-bud appearance
    
• Lymph nodes
  • Low density center with rim enhancement

• Fungal infection
  • Histoplasmosis
  • Coccidiomycosis
  • Sporotrichosis
• Ankylosing spondylitis
  
• Progressive massive fibrosis
  
• Sarcoidosis

• Pigmented “dirty” marcophages surrounding respiratory bronchioles
  
• May be precursor of centriacinar emphysema

• Variable
  • Primary pneumonia often asymptomatic
  • Miliary disease may have nonspecific malaise and weight loss
• Treatment
  • Respiratory isolation
  • Anti-tuberculous drugs

Goo JM et al. CT of tuberculosis and nontuberculous mycobacterial infections. Radiol Clin North Am 40(1): 73-87, 2002