RADIOGRAPHIC FINDINGS

The right lung is hyperlucent and increased in volume  ,with mediastinal shift  across the mid-line. The left lung is compressed by the displaced heart and mediastinum. The left lung remains aerated and normal bronchi are seen on that side. The right main bronchus cannot be traced from its origin.

The physical  manisfestation of pulmonary tuberculosis tends to differ by age of onset . Young infant and adolescent manifests significant signs , whereas school aged children usually have silent radiographic disease.

In chest radiography , hilar lymphadenpoathy is always almost  present with childhood tuberculosis, but it may not be distinct on plain radiograph when calcification is not present . As the hilar  or mediastinal lymph node continue to enlarge , partial obstruction caused by external compression causes  air trapping , hyprerinflation  or even lobar emphysema .

As the lymph node attach to and infiltrate the bronchial wall resorption of  air and atelectasis occur .

The radiographic findings are similar to those of foreign body aspiration with lymph node acting as foreign body .

Multiple segmental lesions in different lobes may be apparent simultaneously , and segmental atelectasis and hyperinflation can occur together .

The course of  thoracic lymphadenopathy  and bronchial obstruction can follow several paths if antituberculous treatment is not initiated. In many cases , the segment or lobe re expands,and resolves completely .

Or it may cause scarring and progressive contraction of lobe or segment which may be associated with cylindrical bronchiectasis and chronic pyogenic infection.

Radiographic clue  to lymph node enlargement on chest radiograph..

1.Enlargement of the right upper paratracheal nodes causes uniform or lobular widening of the right paratracheal stripe, and an increase in density of the superior vena cava of which the border may become convex to the lung.

2.The enlarged right lower paratracheal nodes push the azygos vein laterally increasing the diameter of the combined opacities of both node and azygos arch .

3.The aortopulmonary nodes may cause a bulge in the angle between the aortic arch and the main pulmonary artery. If they are substantially enlarged, the left upper paratracheal nodes induce mediastinal widening.

4.The radiographic features of subcarinal node enlargement include the displacement of the azygo-oesophageal line that becomes convex to the lung, an increased opacity of the subcarinal space on the posteroanterior film and a lack of visibility of the external surface of the medial wall of the intermediate bronchus.

5.Enlargement of the anterior mediastinal nodes may be substantial to be visible on the chest films. In such case, mediastinal widening is frequently bilateral and lobulated in outline. Increased opacity of the retrosternal area on the lateral view may be sometimes the early sign

6.Enlarged paraoesophageal and posterior mediastinal nodes produce displacement of the azygo-oesophageal and paraspinal lines. The radiographic signs of enlargement of hilar lymph nodes are hilar enlargement, lobulation of outline or rounded mass in a portion of the hilum .