Diffuse pulmonary nodules (differential diagnosis)

A number of differentials must be kept in mind while approaching diffuse or multiple pulmonary nodules. Interpretation is easier if nodules are the only abnormality.

Differential diagnosis

These differentials can be narrowed down based on several criteria:

Based on appearance 

• miliary nodules  
  • miliary tuberculosis
  • silicosis
  • pulmonary sarcoidosis
  • diffuse pulmonary metastases
  • diffuse panbronchiolitis
• cavitatory nodules
  • septic pulmonary emboli
  • cavitating metastases
  • multiple cavitating infection
• calcific nodules
  • tuberculosis
  • silicosis
  • calcified pulmonary metastases

Based on pattern of distribution

• centrilobular nodules
  • with tree-in-bud: bronchiolar spread of infection, e.g. pulmonary tuberculosis
  • without tree-in-bud
    • small airway disease
    • hypersensitivity pneumonitis
• perilymphatic nodules
  • nodules related to pneumoconiosis
  • pulmonary sarcoidosis
  • pulmonary amyloidosis: nodular type
• random pulmonary nodules
  • sarcoidosis
  • silicosis
  • nodular pulmonary metastases
  • benign metastasizing leiomyoma 

Based on lobar involvement

There is a lot of overlap in pathology, but as a very crude guide consider:

• upper and middle lobes: silicosis
• upper lobe: sarcoidosis, respiratory bronchiolitis
• peripheral: infection
• peripheral and lung bases: metastases