From the Guidelines
Active tuberculosis on a CT scan is characterized by findings such as nodular opacities, tree-in-bud patterns, cavitary lesions, and consolidation in the upper lobes of the lungs, as described in the study by 1. These characteristic findings are crucial for the diagnosis of active TB, and CT scans are particularly useful in increasing the specificity of the diagnosis, especially in cases where chest radiography does not show classic findings of TB 1. The CT findings can also be helpful in predicting acid-fast bacilli smear positivity and identifying patients with latent TB who are at risk for reactivation disease 1. Some of the key CT scan findings of active TB include:
- Nodular opacities
- Tree-in-bud patterns
- Cavitary lesions with thick, irregular walls
- Consolidation areas
- Ground-glass opacities
- Miliary tuberculosis with numerous tiny nodules scattered throughout both lungs
- Enlarged lymph nodes with central low density and peripheral enhancement
- Pleural effusions
- Fibrotic changes, bronchiectasis, and calcifications in the upper lobes in post-primary TB. The study by 1 highlights the importance of CT scans in the diagnosis and management of active TB, particularly in immunocompromised patients where the disease may present with atypical findings.
From the Research
CT Scan Findings of Active Tuberculosis (TB)
The computed tomography (CT) scan findings of active tuberculosis (TB) include:
- Consolidation, centrilobular nodules with tree-in-bud branching, cavitating lesions, and miliary nodules 2
- Ground-glass pattern, poorly marginated nodules, and infiltrates 3
- Micronodules, nodules, tree-in-bud appearance, consolidation, and cavities 4
- Nodules indicating the presence of a tree-in-bud pattern, ill-defined nodules, consolidation, architectural distortion, cavitary lesions, and ground glass opacities 5
- Airway involvement, characterized by increased thickness and dilatation of the bronchial walls, and pleural involvement 5
Atypical CT Patterns
Atypical CT patterns of granulomatous disease including tuberculosis have been described, such as:
- Clusters of nodules without confluence or with confluence 2
- Reversed halo sign, the galaxy sign, and the cluster sign, which are signs borrowed from other diseases 6
Evolution of CT Findings
The evolution of CT findings in active TB includes: