The reasoning
| Primary TB | Post‑primary TB | |
|---|---|---|
| Host | children; adults with HIV/immunosuppression | adults (reactivation or reinfection) |
| Parenchyma | homogeneous consolidation, any lobe (often middle/lower, also upper) | apical and posterior segments of upper lobes, superior segment of lower lobes; patchy, ill‑defined |
| Lymphadenopathy | hallmark: ipsilateral hilar ± right paratracheal; CECT: central low attenuation with rim enhancement (caseation) | uncommon |
| Cavitation | uncommon (but can occur, especially in adults and progressive primary disease) | hallmark; thick‑walled → thin‑walled with treatment |
| Pleural effusion | common; may be the sole finding (adolescents/young adults) | less common |
| Airway spread | — | tree‑in‑bud, centrilobular nodules (activity) |
| Other | miliary, atelectasis from nodal compression (RML) | fibrosis, volume loss, bronchiectasis, tuberculoma |