CT Findings in Pulmonary Tuberculosis

1. CT Findings in Pulmonary Tuberculosis

2. Primary Tuberculosis • CT helps confirm the presence of an ill-defined parenchymal infiltrate, as well as lymphadenopathy. • CT scans may demonstrate enlarged lymph nodes typically measuring more than 2 cm. Lymph nodes demonstrate central hypoattenuation with peripheral rim enhancement with the administration of contrast material. This appearance reflects central necrosis within the node. • CT is the examination of choice for evaluating lymphadenopathy and involvement of the tracheobronchial tree. Lymphadenopathy causing bronchial compression can be identified on CT scans, and airway compromise can be monitored during chemotherapy.

3. Primary Tuberculosis • Broncholiths may be identified in rare cases. • Morphologically, the stenoses in active disease are areas of irregular luminal narrowing with circumferential wall thickening. • Associated mediastinitis and even mediastinal abscesses may be present. • In patients who are severely affected, segmentectomy or lobectomy may be required to treat the symptoms.

4. Primary Tuberculosis • Small pleural effusions are detected more readily on CT scans than on other images. Contrast enhancement may be useful in identifying evolution into an empyema.

5. Reactivation Tuberculosis • Cavitation is best demonstrated on CT scans. • The outer wall of the cavity tends to be thick walled and irregular, whereas the inner wall tends to be smooth. • An air-fluid level may be identified. The connection of the cavity to the airway may be visualized. • Complications of cavitary disease may become apparent with mycetoma formation, which appears as an intraluminal collection of material with a crescent of surrounding air. Changes in patient positioning demonstrate a change in the position of the mycetoma relative to the cavity.

6. Reactivation Tuberculosis • Tuberculomas can be identified on CT scans as rounded nodules that usually have surrounding associated satellite lesions. • The bronchogenic spread of tuberculosis is recognized on CT scans by the presence of acinar shadows and nodules of varying sizes in a peribronchial distribution. The lesions are seen throughout both lungs.

7. Airway Involvement • Lymphadenopathy is a feature of primary infection; however, calcified lymph nodes may cause persistent extrinsic compression on the bronchi. • Bronchial stenosis is more common in postprimary disease than in primary tuberculosis. In fibrocavitary tuberculosis, the proximal bronchi are more typically involved than the peripheral airways. Variable areas of stenosis are demonstrated. Wall thickening tends to be less marked than in primary tuberculosis.

8. Airway Involvement • Bronchiectasis is a well-known sequela of postprimary disease. Bronchiectasis tends to occur in the upper lobes and often manifests as traction bronchiectasis on the basis of fibrotic disease with subsequent traction on the airways. Recurrent infections and hemoptysis may result from traction bronchiectasis.

9. Pleural Involvement • Empyema is visualized on contrast-enhanced CT scans with enhancement of the parietal and visceral pleurae. • They may demonstrate enhancing septa within the pleural fluid collections. The pleural fluid collections are characterized by low attenuation; however, they do not have attenuation values consistent with simple fluid. • Empyemas demonstrate the so-called split pleura sign. This sign consists of the pleural fluid collection tracking between the abnormally enhancing parietal and visceral pleura.

10. Pleural Involvement • Spontaneous pneumothorax is an uncommon complication of disease, may be secondary to peripherally located lesions. • Involvement of the pericardium and spine may be demonstrated on CT images.