대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Pulmonary tuberculosis

Radiologic Findings

Chest simple radiograph shows patchy ground-glass opacities in both upper and middle lung fields.

Chest CT with 8-mm slice thickness shows multifocal patchy ground-glass opacities in both lungs. In the areas of ground-glass opacity, tree-in-bud appearances are faintly seen.

High-resolution CT scans show tree-in-bud appearances are undoubtedly seen. Multifocal patchy ground-glass opacities on 8-mm slice thickness CT and chest simple radiograph are congregation of tree-in-bud lesions.



The sputum AFB was strongly positive. The anti-tuberculous chemotherapy was started.

On chest simple radiograph three months after anti-tuberculous chemotherapy, previous lesions nearly disappeared. Small granulomas are seen in left upper lung fields.

Brief Review

The most common route of dissemination in postprimary pulmonary tuberculosis is through the bronchi. High-resolution CT (HRCT) is extremely helpful in understanding the route of spread and the pathologic nature of the tuberculous lesions. The most common and earliest HRCT findings of the bronchogenic spread of tuberculosis are centrilobular, relatively well-defined 2- to 4-mm nodules or branching lesions showing a tree-in-bud appearance. Pathologically, these centrilobular lesions correspond with caseation necrosis within the bronchioles. Because of the compact nature of caseation necrosis, the centrilobular lesions have sharp margins and relatively high attenuation in spite of their small size (1). Terminal tufts of the "tree-in-bud" structure may represent lesions within the bronchioles and alveolar ducts, while the stalk may represent a lesion that affects the last-order bronchus within the secondary lobule (2).

The lesions of tree-in-bud appearance are commonly accompanied by 5- to 8-mm, relatively fuzzy marginated nodules, thickening of adjacent bronchi and lobular consolidation. Extension of caseation necrosis and inflammation to peribronchiolar area and bronchial wall forms fuzzy marginated nodules and thickening of bronchi. Lobular consolidation pathologically consists of centrally located granulomas that contain caseation necrosis and marginal nonspecific inflammation. The areas of nonspecific inflammation appear relatively loose compared with caseation necrosis (1).

In this case, the tree-in-bud appearance is only seen on HRCT. There was no areas of fuzzy marginated nodules, thickening of adjacent bronchi or lobular consolidation.

References

1. Im JG, Itoh H, Lee KS, Han MC. CT-pathology correlation of pulmonary tuberculosis. Crit Rev Diagn Imaging 1995;36:227-285.

2. Im JG, Itoh H, Shim YS, Lee JH, Ahn J, Han MC, Noma S. Pulmonary tuberculosis: CT findings--early active disease and sequential change with antituberculous therapy. Radiology 1993;186:653-660.

Keywords

Lung, Infection, Bacterial infection, Tuberculosis,