1. Bronchiectasis, secondary to tuberculosis.

In the CT above, one can see dilated thick-walled airways in the right middle lobe and left lower lobe (arrows). The dilated bronchiectatic airways form the classic "signet-ring" with the accompanying pulmonary artery.

Bronchiectasis is a chronic, usually inflammatory, often suppurative condition that leads to irreversibly dilated airways. The CT signs of bronchiectasis include air/fluid levels in distended bronchi, a linear array or cluster of cysts, dilated bronchi in the periphery of the lung, and bronchial wall thickening due to peribronchial fibrosis. Distended bronchi are easily distinguished from bulla, which generally have no definable wall thickness and no accompanying vessels.

Bronchiectasis has been classified into cylindrical, varicose and saccular (cystic) types. However, bronchiectatic airways exhibit a clear spectrum of disease severity, not always falling neatly into this classification. Some patients may have varying severity of disease. The significance of these different classifications has little clinical use. Cylindrical is the least severe form. Varicose bronchiectasis has alternating dilatation and constriction yielding a beaded, varicoid appearance. Saccular bronchiectasis is the most severe form, the airways markedly dilated.