An HRCT Approach to Diffuse Nodular Lung Disease
A distribution-first HRCT approach to diffuse pulmonary nodules, separating perilymphatic, random, and centrilobular patterns and translating them into a focused report.
Diffuse small pulmonary nodules have a broad differential diagnosis. On high-resolution CT, the most useful first step is to determine their relationship to the secondary pulmonary lobule. Nodule margin, attenuation, size uniformity, craniocaudal predominance, and accompanying parenchymal or extrapulmonary findings then refine the interpretation.
Perilymphatic distribution
Perilymphatic nodules involve the peribronchovascular interstitium, interlobular septa, fissures, and subpleural surfaces. Sarcoidosis, silicosis or coal-worker pneumoconiosis, and lymphangitic carcinomatosis are key considerations. Upper-lung predominance and symmetric hilar or mediastinal lymphadenopathy support sarcoidosis. Irregular septal thickening, pleural effusion, and asymmetric involvement may favor lymphangitic tumor spread, while occupational exposure and conglomerate upper-lobe masses support pneumoconiosis.