Congenital bronchopulmonary cysts

　　Congenital bronchopulmonary cysts refer to congenital cysts with bronchial tissue as the cyst wall, containing mucus or gas. They were previously known as congenital cystic bronchiectasis or congenital bronchogenic cysts. The etiology of the disease is not fully understood; some believe it is due to abnormal branching during the development of pulmonary buds in the embryonic period, with the distal end forming an epithelial cell nest, which then gradually differentiates to form a cyst. The lumen of the cyst is fibrous, not communicating with the bronchi or only partially communicating. Another explanation is that the formation of pulmonary cysts is based on congenital atelectasis, causing disarray of normal lung structure and arrangement of epithelial cells during the embryonic period.

　　Congenital bronchopulmonary cysts can complicate with pneumothorax. Pneumothorax refers to the presence of air in the pleural cavity, resulting in a pneumothorax state. It is usually divided into three major types: spontaneous pneumothorax, traumatic pneumothorax, and artificial pneumothorax. Spontaneous pneumothorax occurs due to the rupture of lung tissue and parietal pleura caused by lung diseases, or due to the rupture of small air bubbles and bullae near the surface of the lung, leading to the entry of air from the lungs and bronchi into the pleural cavity.

　　The symptoms of congenital bronchopulmonary cysts vary in severity and onset time, depending on their location, size, and whether there are any complications. Adult bronchopulmonary cysts often have no symptoms, and most cases are discovered incidentally during X-ray examination or autopsy. Simple mediastinal bronchial cysts primarily present with compressive symptoms, such as dry cough, wheezing, and varying degrees of dyspnea, and may cause difficulty in swallowing and feeding due to compression of the esophagus. Obstruction of the airway can form a one-way valve, leading to the formation of tension cysts, which may compress the trachea and heart, causing displacement and symptoms such as marked dyspnea, difficulty breathing, and cyanosis. If not treated promptly, it may be life-threatening.

　　Congenital pulmonary cysts with bronchial communication often lead to secondary infection, causing symptoms such as cough, sputum, or hemoptysis, fever, or coughing up large amounts of purulent sputum, which are similar to lung abscess and bronchiectasis. A few patients may have massive bleeding within the cyst, rupture into the pleural cavity, and produce spontaneous pneumothorax or hemothorax. The physical examination findings vary depending on the size of the cyst; larger cysts filled with fluid present with localized dullness on percussion; larger cystic areas with air may present with localized tympany on percussion, and the respiratory sounds may be diminished or absent on auscultation. Smaller cysts located within the lung parenchyma without secondary infection may not show any symptoms or signs.

　　This disease is a congenital lung developmental abnormality, and the preventive methods are the same as those for other congenital diseases. After clear diagnosis, attention should be paid to preventing infection and actively treating. In daily life, pay attention to preventing colds, exercise more, and strengthen physical fitness.

　　Congenital bronchopulmonary cysts communicate with the bronchus, often secondary to infection, presenting with cough, sputum, or hemoptysis, fever, or coughing up a large amount of sputum, similar to lung abscess and bronchiectasis. A few patients may have a large amount of bleeding in the cyst, rupture into the pleural cavity, causing spontaneous pneumothorax or hemothorax. The signs vary with the size of the cyst; larger cysts filled with fluid present as localized dullness on percussion; larger aerated cysts may present as localized tympany on percussion, and the respiratory sound may be weakened or absent on auscultation; smaller cysts located within the lung parenchyma without secondary infection may show no symptoms or signs. The commonly used examination methods are as follows:

　　Laboratory examination

　　Blood gas analysis shows hypoxemia. In secondary infection, peripheral blood shows an increase in white blood cells and neutrophils.

　　Auxiliary examination

　　1, X-ray examination

　　Isolated lung cysts are more common in the lower lobe than in the upper lobe. Fluid-filled cysts appear as round or elliptical, uniformly dense shadows with sharp edges; air-filled cysts appear as thin-walled annular radiolucent shadows, the thicker the cyst, the thinner the wall; tension pneumothorax can be very large, compressing normal lung tissue, causing pulmonary vessels to only be visible at the lung apex or costodiaphragmatic angle, even pushing the mediastinum to the healthy side; giant air-filled cysts can even herniate into the opposite pleural cavity across the anterior mediastinum. Lung cysts with concurrent infection can be seen on X-ray as infiltrative inflammatory shadows around the cyst, thickening of the cyst wall; after inflammation absorption, the cyst and surrounding tissues form adhesions, the X-ray morphology is irregular, showing pleural thickening and adhesion shadows, losing the typical round or elliptical shadows. Bronchial cysts appear as round or elliptical on chest X-ray, with clear contours, smooth edges, uniform density, without lobulated shape, without calcified shadows, attached to one side of the trachea and main bronchus wall, which can be slightly flat due to compression by the trachea and main bronchus wall, and has certain diagnostic significance. Cysts attached to the tracheal wall can move up and down with swallowing movements.

　　2, Bronchial angiography

　　Bronchial angiography is helpful to determine the segment of the lung where the lung cyst is located. If the infection involves the pleura, causing the bronchus to develop stably, the lung cyst will show reduced bronchial branches in the angiography. The contrast agent generally does not enter the cyst, only the air cysts that are connected to the bronchus have contrast agent entering. This type of lung cyst is prone to secondary infection, so it is not advisable to do bronchial angiography. If it is indeed necessary, it is best not to use iodinated oil during the angiography, but to use easily absorbable diatrizoate meglumine, which is conducive to preventing infection.

　　3, CT scan

　　CT scan can further understand the size and scope of the cyst, and also help to understand the density of the cyst and the thickness of the cyst wall, whether the edge is smooth, which is convenient for differentiation from tumors. It can also find irregular shadows on the cyst wall caused by malignant transformation of the cyst. In addition, it should be avoided to puncture and biopsy to prevent the cyst from rupturing and becoming infected.

　　Congenital bronchopulmonary cysts should be surgically resected actively, the earlier the better. Some people advocate surgery within the first year of life, as infections are rare and cystectomy is more feasible. If the cyst is infected, it is better to perform surgery after controlling the infection for 3 months. Resection can cure the disease without recurrence. Patients with congenital bronchopulmonary cysts should adopt a light diet, eat more vegetables and fruits, rationally match their diet, and pay attention to adequate nutrition.

　　In the treatment of this disease, as long as the diagnosis is clear and there is no acute inflammation, early surgery should be performed. Because cysts are prone to secondary infection, drug treatment not only cannot cure the disease but can also cause widespread pleural adhesions around the cyst wall after repeated infections, making surgery more difficult and prone to complications. Young age is not an absolute contraindication for surgery. Especially in cases with symptoms of hypoxia, cyanosis, and respiratory distress, early surgery, even emergency surgery, should be performed to save lives.

　　The method of surgery should be determined according to the location, size, and infection status of the lesion: an uninfected cyst isolated under the pleura can be treated with simple cystectomy; a cyst limited to the lung margin can be treated with lung wedge resection; if the cyst is infected and leads to adhesions around the surrounding tissue or adjacent bronchial dilation, a lung lobe or pneumonectomy should be performed. In the case of bilateral lesions, the side with more severe lesions can be treated first under the premise of having surgical indications. Children should try to preserve normal lung tissue as a principle.

　　When clinically suspected of this disease, it should be avoided as much as possible to perform pleural puncture to prevent pleural infection or the occurrence of tension pneumothorax. Only in a few cases, where there is severe respiratory distress, cyanosis, and severe hypoxia, and there is no condition for emergency surgery, can cyst puncture and drainage be performed to achieve temporary decompression, relieve respiratory distress symptoms, and serve as a temporary emergency measure before surgery. Generally, the prognosis is good after resection of the affected cyst or lung lobe.

　　Adult patients with a large amount of sputum before surgery need to undergo double-lumen tracheal intubation anesthesia to prevent sputum from flowing back to the opposite side. Children can adopt a low lateral decubitus position on the affected side for thoracotomy, and after entering the chest, the affected lung bronchus should be ligated first.

　　If the lesion is too extensive, the lung function is severely decreased, or serious organic diseases such as severe heart, liver, and kidney diseases are present, surgery is contraindicated.