Bronchiectasis is irreversible abnormal dilation of the inner diameter of bronchi, mostly in children and young adults, and there is no significant difference in the incidence between males and females.
Clinical presentation and pathology
Etiology can be congenital and acquired, mostly acquired. Etiology of congenital bronchiectasis includes congenital immunoglobulin deficiency, cystic fibrosis, and immotile cilia syndrome. Etiology of acquired bronchiectasis includes destruction of bronchial wall tissue caused by chronic infection, increased intrabronchial pressure caused by bronchial secretion accumulation and long-term severe cough, and external traction on the bronchial wall resulting from atelectasis and pulmonary fibrosis. According to the morphology of dilation, bronchiectasis can be divided into cylindrical or tubular bronchiectasis, varicose bronchiectasis, and cystic bronchiectasis. Three types can coexist simultaneously or one of them can be dominant. Bronchiectasis generally occurs in the 3rd to 6th generation of bronchi, mainly in the lower lobes of both lungs, the lingular segment of the left lung, and the middle lobe of the right lung, and can exist on both sides simultaneously. Clinically, patients often have cough, purulent expectoration, and hemoptysis.
Imaging manifestations
X-ray
Conventional chest radiograph may be normal, and sometimes increased lung markings and/or annular lucency may be seen in the lesion.
CT
CT is currently the most used imaging method for diagnosing bronchiectasis. In cylindrical or tubular bronchiectasis, the dilated bronchus running parallel to the CT plane shows tram track sign, while the dilated bronchus running perpendicular to the CT plane shows thick-walled round lucency, forming signet ring sign with the accompanying pulmonary artery. Varicose bronchiectasis is manifested by irregular widening of the bronchial cavity and rough wall, and may be beaded. In cystic bronchiectasis, the distal end of the bronchus is cystic and dilated, clustered cystic dilations form cluster of grapes sign, also known as bunch of grapes sign, and air-fluid level may appear in the cyst when with infection. In bronchial mucoid impaction, mucoid impaction filling the dilated bronchial cavity presents clavate or nodular hyperdense opacity, forming finger in glove sign; there are patchy exudative opacities and irregular linear opacities around the dilated bronchi when with infection.
Figure 1 Cylindrical bronchiectasis
CT lung window shows widened bronchial lumen in the posterior segment of the right upper lung, the inner diameter is larger than that of the accompanying pulmonary artery, forming signet ring sign (↗).
Figure 2 Cystic bronchiectasis
CT lung window shows multiple cystic bronchiectasis in the left lower lung, with honeycomb changes, and small air-fluid levels in the lumen of some dilated bronchi.
Figure 3 Bronchiectasis with mucoid impaction
CT lung window shows cylindrical bronchiectasis with mucoid impaction in the right upper lung, presenting hyperdense finger in glove sign.
Diagnosis and differential diagnosis
Chest plain film can sometimes suggest bronchiectasis. CT examination should be performed to further confirm the diagnosis and clarify the type, range, and degree of bronchiectasis. All types of bronchiectasis have characteristic manifestations. In combination with clinical presentation, diagnosis is generally not difficult. Cystic bronchiectasis needs to be differentiated from multiple air-containing lung cysts and pneumatocele.