A 42-year-old woman with known pulmonary tuberculosis undergoes high-resolution CT chest. Multiple imaging patterns are identified. Which is the most common radiological pattern seen in active pulmonary tuberculosis?
A. Bronchiectasis with bronchial dilatation
B. Cavitary lesion with surrounding consolidation
C. Solitary nodule with halo sign
D. Tree-in-bud opacities with bronchial wall thickening
Explanation
Most Common Radiological Pattern in Active TB on HRCT
Key Point
Tree-in-bud opacities with bronchial wall thickening are the most common and characteristic HRCT pattern of active pulmonary tuberculosis, reflecting endobronchial spread of infection.
Radiological Patterns of TB — Frequency on HRCT
Table
Pattern
Frequency
Clinical Significance
Typical Location
Tree-in-bud opacities + bronchial wall thickening
Most common (~60–80%)
Endobronchial/bronchogenic spread; active disease
Upper lobe, centrilobular
Consolidation ± cavitation
Common (~40–60%)
Active disease; highly infectious
Upper lobe apical-posterior
Solitary nodule ± halo
Less common (~10–15%)
Early/nodular TB
Variable
Bronchiectasis
Sequela (~5–10%)
Chronic/healed TB
Lower lobes
High-YieldNEET PG
On HRCT, tree-in-bud opacities represent:
Centrilobular nodules (2–4 mm) connected by branching linear structures
Filling of terminal and respiratory bronchioles with caseous material, mucus, or pus
Pathognomonic of bronchogenic spread of TB — the dominant mechanism of active disease dissemination
Mechanism of Tree-in-Bud Pattern in TB
1.
Caseous material from a primary focus liquefies and drains into the bronchial tree
Centrilobular nodules form as bronchioles fill with infected material
4.
Branching pattern on HRCT resembles a "tree in bud" (budding tree in spring)
5.
Bronchial wall thickening accompanies the peribronchial inflammation
Clinical Pearl
The question specifically asks about HRCT findings in active TB. While cavitation is a well-known feature, tree-in-bud opacities are the most frequently identified pattern on HRCT in active disease, as described in standard radiology references (Webb, Müller & Naidich — High-Resolution CT of the Lung; Hansell et al.). Cavitary lesions, though highly specific, are present in a smaller proportion of HRCT-confirmed active TB cases.
Why Other Options Are Less Correct
Cavitary lesion with surrounding consolidation (Option C): Highly specific for TB and indicates active disease, but cavitation is seen in only ~40–50% of active TB cases on HRCT — less frequent than tree-in-bud opacities
Solitary nodule with halo sign (Option B): Halo sign is more characteristic of angioinvasive aspergillosis; uncommon in TB
Bronchiectasis with bronchial dilatation (Option D): A sequela of chronic/healed TB, not a primary active disease pattern
