Which finding is characteristic of primary tuberculosis infection on imaging?

The characteristic finding of primary tuberculosis infection on imaging is middle/lower lobe consolidation. In primary tuberculosis, the infection typically begins in the peripheral regions of the lung, which often results in consolidation in the middle and lower lobes, reflecting the initial site of infection and the body’s immune response to the Mycobacterium tuberculosis organism.

This is in contrast to later stages of tuberculosis, where cavitary lesions may develop, usually indicating a reactivation of the disease and often appearing in the upper lobes. Granuloma formation is certainly a feature of tuberculosis but is not exclusive to primary infection; granulomas can also be found in secondary and latent phases of the disease. Thus, while granuloma formation can be associated with tuberculosis, it does not serve as a primary imaging characteristic for initial infection, making middle/lower lobe consolidation the defining feature on imaging for primary tuberculosis.