← All patterns
Multiple pulmonary nodules
ChestCT
Numerous discrete nodules. Distribution (random, perilymphatic, centrilobular) and clinical setting narrow the differential considerably.
Differential
Haematogenous metastases
common- •Random distribution, lower-lobe predominance
- •Variable sizes, sharply marginated round nodules
- •Known primary malignancy
Septic emboli
common- •Peripheral nodules with feeding-vessel sign
- •Cavitation and wedge-shaped infarcts
- •IV drug use / right-sided endocarditis / line sepsis
Granulomatous infection (TB / fungal)
less-common- •Tree-in-bud and centrilobular nodules
- •Upper-lobe cavities, lymphadenopathy
- •Miliary pattern if disseminated
Sarcoidosis
less-common- •Perilymphatic distribution (fissures, bronchovascular bundles)
- •Symmetric hilar/mediastinal adenopathy
- •Upper/mid-zone predominance
Granulomatosis with polyangiitis
rare- •Multiple cavitating nodules with variable wall thickness
- •c-ANCA positive, sinus/renal disease
- •Feeding vessel to nodules
Rheumatoid nodules
rare- •Peripheral, subpleural nodules that may cavitate
- •Established seropositive rheumatoid arthritis
- •Wax-and-wane with disease activity
Key discriminators
- •Distribution: random vs perilymphatic vs centrilobular/tree-in-bud
- •Cavitation and wall pattern
- •Feeding-vessel sign (emboli/vasculitis)
- •Associated lymphadenopathy
- •Clinical context (malignancy, sepsis, ANCA, RA)
Work-up / next steps
- 1.Characterise distribution on thin-section CT
- 2.Correlate with infective/inflammatory markers and cultures
- 3.Search for a primary malignancy if random pattern
- 4.Short-interval CT to assess evolution when infection suspected
References
- Radiopaedia: Multiple pulmonary nodules.
- Webb, Müller & Naidich. High-Resolution CT of the Lung.
Educational clinical decision support only. This differential does not make a diagnosis, is not a medical device, and must never substitute for interpretation by a qualified radiologist correlated with the full clinical picture and prior imaging.