How are bullae formed? What causes bullae?

Knowing the cause of bullae can also help in prevention and treatment. Early detection and treatment are the most important for patients with bullae. General pneumonia and secondary lesions of emphysema can cause bullae. Timely examination is required and the diagnosis can be confirmed through chest X-ray.

1. Causes of bullae

Bullae are generally secondary to inflammatory lesions of the small bronchi, such as pneumonia, tuberculosis or emphysema. There are also some idiopathic bullae with unclear causes. After inflammatory lesions occur in the small bronchi, edema and stenosis appear, the lumen is partially blocked, and a living valve effect is produced, which allows air to enter the alveoli but is not easily discharged, causing the pressure in the alveolar cavity to increase. At the same time, inflammation damages the lung tissue, and the alveolar walls and septa gradually rupture due to the increase in alveolar pressure, and the alveoli fuse with each other to form large air sacs. Under the microscope, the alveolar wall can be seen to be composed of alveolar squamous epithelial cells, and sometimes only fibrous membrane or fibrous connective tissue may exist.

Bullae can be single or multiple. Those secondary to pneumonia or tuberculosis are often solitary; those secondary to emphysema are often multiple, and the bullae are often unclearly demarcated from the lung tissue with emphysematous changes. Emphysema with obvious bullae is also called bullous emphysema.

2. Inspection

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2. Fluoroscopic and expiratory chest X-rays: These help to detect bullae because gas retention during exhalation makes the bullae appear relatively larger and their edges clearer. Tomography is also helpful in clarifying the outline of bullae and showing the compression and displacement of surrounding lung tissue. When lobular emphysema coexists, the tomography can also show abnormalities in the shape of pulmonary blood vessels.

3. CT examination: It can reveal lung bullae with a diameter of less than 1 cm under the pleura, which are difficult to show on ordinary chest X-rays.

4. Pulmonary angiography: It can accurately show the degree of damage to the pulmonary blood vessels and the compression of the blood vessels around the bullae.