Congenital pulmonary cyst in children

　　1. Etiology

　　The etiology is not fully understood. Some people believe that it is due to abnormal branching during the development of lung buds in the embryonic stage, with the distal part forming an epithelial cell nest, which gradually differentiates and forms a cyst. The lumen of the cyst is in a cord-like shape, not communicating with the bronchus or only partially communicating. Another explanation is that the formation of lung cysts is based on congenital atelectasis, causing the normal lung structure and arrangement of epithelial cells during the embryonic stage to be disordered and resulting in the formation of cysts.

　　2. Pathogenesis

　　The mechanism of occurrence is generally believed to be that a segment of bronchus芽 is separated from the main bronchus during the process of embryonic development, and the mucus secreted by the distal bronchus accumulates to form a lung cyst. Bronchogenic cysts are mostly located in the mediastinum, while alveolar lung cysts are mostly located in the peripheral part of the lung, within the lung parenchyma. Congenital lung cysts can be solitary or multiple. They can occur in one or several lobes of the lung. If a large part or all of the lung tissue on one side or one lobe is occupied by multiple cystic tissue, it is called polycystic lung. Macroscopically, the size of the cyst cavity is not uniform, it can be unilocular or multilocular. The surface of the cyst is smooth, the wall is thin, and it contains mucus or mucous gas. Histologically, the outer layer of the cyst cavity is composed of connective tissue, elastic tissue, and smooth muscle fibers. The lumen contains sparse cartilage tissue. The inner layer of the cyst wall is mainly composed of columnar epithelial cells or pseudostratified ciliated epithelial cells, and also contains mucous gland tissue, which often secretes mucus into the cyst cavity. The blood supply of lung cysts is the same as that of normal lung tissue, coming from the pulmonary artery and bronchial artery, which is different from pulmonary sequestration. In addition, since lung cysts do not participate in respiration, the wall of the cyst cannot see carbon dust pigmentation. When there is too much mucus retention inside the cyst, or secondary purulent infection occurs, the cyst cavity is prone to penetrate the bronchus, often forming a unidirectional valve-like ventilation, leading to a continuous increase in intracystic pressure, forming a tension pneumothorax. Some people believe that if there are more bronchial epithelial cells found in the cyst wall, it indicates that the cyst comes from the bronchus and is called bronchogenic cyst; if the wall is mainly composed of flat epithelial cells, it is called pulmonary cyst. However, in most cases, the wall layer of the cyst contains both of the above-mentioned cells, so it is not easy to explain that there are differences in the pathological basis of the two. When the cyst is complicated with infection, due to inflammatory cell infiltration, it often causes the original cell structure of the cyst wall to change. The wall of chronic lung abscess can also appear a layer of flat epithelial cells, so it is not easy to judge the nature and origin of the cyst solely by histological examination.

　　In severe cases, it can cause respiratory and circulatory failure. The main cause of this phenomenon is the communication between the cyst cavity and the bronchus, forming a tension pneumocyst. Larger cysts often have secondary infection; sudden crying, trauma, etc., can lead to tension pneumothorax. Pulmonary cysts themselves do not have gas exchange function, and large cysts can compress lung tissue, causing respiratory gas exchange obstruction. In severe cases, it may even cause increased pulmonary artery pressure, exacerbating the cardiac burden. Long-term recurrent infection may lead to adhesions in surrounding tissues, affecting lung function, increasing the difficulty of surgery, and affecting postoperative recovery. Bleeding and perforation caused by the destruction of the cyst wall may lead to pneumothorax and hemothorax. There are reports that pulmonary cysts may have the potential to become malignant.

　　The clinical manifestations of congenital pulmonary cysts can vary greatly. Depending on the size, number, and degree of impact on adjacent organs, the presence of complications such as infection and rupture, the symptoms may vary, mainly including compression and infection. Small cysts may show no symptoms and are often only discovered during X-ray examination. Larger cysts may present with symptoms when secondary infection occurs or they suddenly enlarge and compress surrounding tissues, such as causing wheezing, dry cough, and varying degrees of respiratory difficulty, even cyanosis. Compression of the esophagus may lead to dysphagia. Infection may cause fever, cough, sputum, and even hemoptysis. On physical examination, small cysts may show no abnormal signs, while larger ones may exhibit dullness or resonance on percussion, reduced or absent breath sounds, and tension pneumothorax in cases of tension pneumomediastinum. Chronic infection may manifest as recurrent cough, sputum, and low fever.

　　There are currently no effective preventive measures. This condition is a congenital abnormality of lung development and should be prevented in the same way as other congenital diseases. After an accurate diagnosis, attention should be paid to preventing infection and actively treating the condition. Infants and young children without symptoms can be closely observed for several months or years before surgery, to increase the tolerance to surgery. Surgery should be performed as soon as possible after infection is controlled to avoid secondary infection and the occurrence of various complications, which may make surgery difficult.

　　1. X-ray examination

　　Isolated fluid cysts appear as clear, round, dense shadows on chest X-rays, while isolated air-filled cysts show up as thin-walled, circular or elliptical radiolucent areas. If multiple lung cysts are located in the posterior mediastinum, esophageal compression symptoms may occur, making swallowing difficult. In such cases, barium swallow examination is necessary to understand the relationship between the mass and the esophagus, and to differentiate from diaphragmatic hernia.

　　2. Bronchography

　　It can determine the range and location of the cystic lesions.

　　3. CT

　　It is helpful in determining the location, size, and relationship of adjacent organs of the cysts. For鉴别 large bullous cysts and pneumothorax, enhanced CT scan can be performed, where pulmonary vessels can be seen in the former.

　　4. Angiography

　　It is helpful in distinguishing isolated lung.

　　5. Ultrasound

　　It has a certain effect on distinguishing intrapulmonary, pleural lesions, gases, cystic, and solid lesions, but further differentiation is needed for lung abscesses and cystic adenomas.

　　6. Fiberoptic bronchoscopy

　　Fiberoptic bronchoscopy can understand the condition of the mucosa and identify the bleeding site when hemoptysis occurs, excluding bronchial tumors.

　　1. Boil 100 grams of fresh reed root and 90 grams of winter melon seeds to make a decoction, and drink it as tea, once a day. This recipe has the effects of clearing the lungs, resolving phlegm, and promoting diuresis and pus excretion.

　　1. Cut 250 grams of field frog, 500 grams of pumpkin, 60 grams of garlic, and 15 grams of scallion. After peeling and cleaning the field frog and removing the internal organs, wash and cut it into pieces. Clean and wash the garlic, and wash and cut the pumpkin into pieces. Put them all into a pot of boiling water, boil over high heat, then change to low heat and cook for 30 minutes. Add chopped scallion for seasoning and it is ready. This recipe has the effects of removing pus, resolving phlegm, clearing heat, and detoxifying.

　　2. Cut 250 grams of lean beef into pieces, add 25 grams of ginger, and boil 600 milliliters of water. Boil until 80% done. Add 500 grams of pumpkin, peeled and cut into pieces, to the beef soup and cook together. Season with salt, monosodium glutamate, and others, and take it in several doses.

　　3. Grind 50 grams of fragrant melon seeds into powder, add an appropriate amount of sugar, and take it with warm water. It is suitable for lung abscess and intestinal abscess.

　　1. Treatment

　　Surgical treatment should be performed under the condition of controlling infection and preparing for blood transfusion, regardless of age. If surgery is delayed, it is easy to have recurrent infections, leading to severe pleural adhesions. Cystectomy can be performed for pulmonary cysts at the edge of the lung lobe; for pulmonary cysts in the middle of the lung lobe, lobectomy is required, which generally has good effects.

　　2. Prognosis

　　Patients with prolonged and recurrent infections are prone to complications such as pleural adhesions and tension pneumothorax. Severe cases can lead to respiratory and heart failure, endangering the lives of children. Successful surgery has a good prognosis.