From the Guidelines
The computed tomography (CT) chest findings in tuberculosis (TB) typically include cavitation, endobronchial spread with tree-in-bud nodules, and fibro-cavitary disease in the apical posterior upper lobe or superior-segment lower lobe 1.
Key CT Findings
- Cavitation: a hallmark of TB, especially in reactivation TB
- Tree-in-bud nodules: indicative of endobronchial spread
- Fibro-cavitary disease: characteristic of reactivation TB
- Lymphadenopathy: may be present, especially in primary TB or in immunocompromised patients
Clinical Context
CT is particularly useful when chest radiography is nonrevealing or nondiagnostic, and can help identify patients with latent TB who are at risk for reactivation disease 1. In immunocompromised patients, CT may reveal abnormal lymph nodes or subtle parenchymal disease that is not apparent on chest radiography 1.
Diagnostic Approach
The American College of Radiology recommends chest radiography as the first-line imaging test for suspected TB, with CT reserved for cases where radiography is nonrevealing or nondiagnostic 1.
Important Considerations
- Clinical suspicion: a high level of suspicion for TB should be maintained in immunocompromised hosts, particularly those with AIDS
- Imaging findings: while CT can increase the specificity of the diagnosis of TB, it is not always necessary in the acute setting, especially when the disease is already suspected and appropriate precautions and testing are underway 1
From the Research
CT Chest Findings in Tuberculosis
The computed tomography (CT) chest findings in tuberculosis (TB) can be summarized as follows:
- Typical CT findings of active postprimary pulmonary tuberculosis include:
- Centrilobular nodules and branching linear structures (tree-in-bud appearance) 2
- Lobular consolidation
- Cavitation
- Bronchial wall thickening
- Inactive pulmonary tuberculosis may show:
- Calcified nodules or consolidation
- Irregular linear opacity
- Parenchymal bands
- Pericicatricial emphysema 2
- Primary tuberculosis on CT scans typically appears as:
- Homogeneous, dense, well-defined segmental or lobar consolidation
- Enlargement of lymph nodes in the hilum or the mediastinum 2
- Atypical radiologic manifestations of tuberculosis may include:
- Single or multiple nodules or masses
- Basilar infiltrates
- Miliary tuberculosis with diffuse bilateral areas of ground-glass opacity
- Reversible multiple cysts 2
- CT findings associated with smear-positive pulmonary tuberculosis include:
- Cavity
- Consolidation
- Bronchiectasis
- Upper lobe involvement
- Multiple lobe involvement
- Lymphadenopathy 3
- The "tree-in-bud" pattern on CT is highly specific for active tuberculosis, with a specificity of 97% 4
Comparison with Other Imaging Modalities
- Lung ultrasound (LUS) has a lower sensitivity (39.5%) compared to chest CT for detecting pulmonary cavitations in TB patients 5
- Chest X-ray (CXR) has a sensitivity of 68.4% for detecting pulmonary cavitations in TB patients, which is lower than CT but higher than LUS 5
- Quantitative IGRA testing has a sensitivity of 64% and specificity of 61% for diagnosing active tuberculosis, which is lower than CT findings such as the "tree-in-bud" pattern 4