Various cystic lesions in the lungs that develop from congenital lung diseases are collectively called congenital pulmonary cystic disease. Pulmonary alveoli and bronchial cystic dilatation following staphylococcal pneumonia are known as acquired pulmonary cystic disease. Depending on the origin of the embryonic developmental malformation, congenital pulmonary cystic disease is divided into two major categories: bronchogenic cyst and parenchymal cyst of the lung. According to their pathology, they can be divided into True congenital pulmonary cyst and Congenital cystic adenomatoid malformation of the lung.
I. Bronchogenic cysts
Congenital bronchogenic cyst is a rare malformation in which the tracheobronchial tree branches abnormally during embryonic development, and is divided into mediastinal cyst, intraesophageal wall cyst and bronchial cyst.
1. Embryo and pathology
In the 4th week of embryo, the primitive foregut begins to separate into larynx, trachea and esophagus, and the bronchial tree that splits out is impaired in early embryonic development, and the distal lung buds are tubularized and the proximal end does not communicate with the bronchus, forming a closed cystic malformation, which is called bronchogenic cyst. The cysts can be single or multiple and can range in size from a few millimeters to occupy 1/3 to 1/2 of one side of the thorax. single or multiple rooms, with walls of varying thickness and an inner layer composed of columnar or pseudostratified epithelial cells containing colorless or white mucus, with a few being bloody. The cyst wall may contain mucus glands, cartilage, elastic tissue and smooth muscle. Bronchogenic cysts are usually located in the mediastinum near midline structures (e.g., trachea, esophagus, rongeurs) or extend down the common bronchus or fuse with it, most do not communicate with the bronchus and may be filled with pus or air when infected. Occasionally, they may connect with bronchi or be multifocal cysts. They can also grow in the lung tissue and are called intrapulmonary bronchogenic cysts. Because bronchogenic cysts do not participate in respiratory activity, the cyst wall is free of carbon end pigmentation, which is characteristic of congenital bronchogenic cysts. The development process of lung can last until 14 years after birth, so the cyst can be born fetus or formed before 14 years after birth.
2.Clinical manifestations
Cysts at birth rarely have detectable symptoms. Subsequently, some cysts become symptomatic due to infection or cyst enlargement compressing the trachea, bronchus or esophagus, showing dyspnea, cyanosis, paroxysmal asthma or dysphagia, and mistakenly attracting recurrent lung infections. If it is connected to the bronchus, there is cough, sputum, and recurrent respiratory infections. In the neonatal period, cysts sometimes compress the bronchial tree branches and lung lobe emphysema occurs, but most children have insignificant clinical symptoms.
3.Diagnosis
Bronchogenic cysts usually cannot be seen on X-ray chest radiographs. when the trachea or esophagus is compressed, emphysema or pulmonary atelectasis can be seen, and barium swallow examination can reveal the cyst located between the trachea and esophagus. CT scan can show the size of the cyst, its relationship with surrounding tissues, etc.
4.Treatment
After the diagnosis is confirmed, it should be removed surgically. Treatment with appropriate antibiotics after surgery. Asymptomatic cysts do not require treatment.
II. Congenital pulmonary cyst
Congenital cyst of lung is a relatively common abnormal lung development disease, but it is still rare in pediatrics, congenital cyst of lung is also called true congenital cyst of lung, about 90% of which are solitary, about 10% combined with other malformations, most commonly isolated lung. There are many different classification methods and names in the literature, the common ones are: (1) the source of cysts can be divided into bronchogenic, alveolarogenic and mixed; (2) the number of cysts can be divided into single and multiple pulmonary cysts; (3) the distribution of cysts can be classified, such as those commonly found in one lobe, one lung or bilateral lobes, called cystic lung, honeycomb lung or multicystic lung.
1.Etiology and pathology
Bronchial cysts in the early embryonic bronchial tree developmental disorders, distal tubularization of the lung buds, proximal and bronchial disconnection, the formation of a closed cyst. These cysts are mostly round in shape, with walls of varying thickness and an inner layer composed of columnar or pseudostratified epithelial cells, which may be covered by flattened epithelium if secondary infection is present, and some of which may be granulation tissue. The outer layer is connective tissue with elastin fibers, smooth muscle fibers, mucus glands and cartilage. Since bronchial cysts do not participate in respiratory activity, the cyst wall is free of carbon end pigmentation, which is characteristic of congenital bronchial cysts. The contents of the cyst are mucus, if never connected with bronchus, it is called liquid cyst; if connected with bronchus, the mucus inside the cyst is discharged and the air enters the cyst cavity called air cyst, sometimes forming tension cyst cavity; sometimes liquid and air exist at the same time, and the cyst on chest film can appear as liquid plane. Tracheal cysts are mostly solitary, and multiple cysts are less common. The development of the lungs can continue until the age of 14 years after birth, so cysts can be born fetal or can form before the age of 14 years after birth.
Congenital pulmonary cysts can occur in any part of the lung, but are most often seen in the lower lobes. Cysts in multiple lobes of the lung are more often seen ipsilateral and less often in both lungs. Cystic lungs are located in the peripheral lung parenchyma of the lung lobes and are unicompartmental or multicompartmental capsules containing fluid or gas and lined with highly columnar ciliated endothelial cells, with chondrocytes and a small amount of smooth muscle. Some cysts may be accompanied by other disorganized tissue with abnormal epithelial cells.
Congenital pulmonary cysts are often associated with other congenital anomalies, such as a left-sided trilobar lung with anomalous branch vessels from the descending or thoracic aorta growing around the affected lung lobe. The branches of the body circulation enter the lung tissue to produce a left-to-right shunt, causing atrophy of the pulmonary arteries and veins due to disuse.
2.Clinical manifestations
Symptoms and signs Although the disease is present at birth, some children have small or single cysts, and most of them have no obvious symptoms when they are not co-infected, and they may be detected only after X-ray or in adulthood. In some cases, respiratory symptoms appear, the extent of which varies depending on the location and size of the cyst and the severity of the complications.
Pulmonary cysts communicate with the bronchi, so they are more likely to be complicated by infection. Clinical manifestations are mainly fever, cough, shortness of breath, cyanosis and other symptoms of respiratory tract infection, and in severe cases of infection, high fever, purulent sputum, and hemoptysis when the cyst is bleeding. If the cyst is large, it can produce dyspnea and wheezing when it compresses the bronchus, and the larger pneumatotic cyst has a valve-like effect when it connects with the bronchus, and it can form a tension pneumothorax-like symptom, and the child has shortness of breath and cyanosis, and the mediastinum is displaced, which can be life-threatening if not treated quickly.
In children with small cysts located in the lung parenchyma, there may be no obvious signs; in larger liquid pneumocysts, there are often reduced breath sounds and turbid percussion sounds on the affected side; in children with secondary lung infections, wet rales in the lungs may be heard; in children with tension pneumocysts, there may be respiratory distress, drum sounds on percussion on the affected side, and diminished or absent breath sounds on auscultation.
3.Diagnosis
Pulmonary cysts are mostly diagnosed due to pulmonary infection, and in a few cases, the diagnosis can be confirmed only after the pulmonary inflammation is controlled.
Isolated fluid cysts on chest X-ray show a well-defined round dense shadow. Isolated air-containing cysts present as a round or oval thin-walled translucent cavity shadow, which can occupy half of the chest cavity in large cases. The surrounding lung tissue is not infiltrated, and a normal air-containing lung or an airless atelectasis is seen. If the cyst communicates with the bronchus, a thin-walled cystic shadow containing pneumatic fluid plane is seen. In case of multiple cysts, multiple annular cavity shadows are seen in one lobe. Bronchography can determine the extent and location of the cystic lesion. A history of recurrent pulmonary infections and the above-mentioned radiographic findings are the main points of diagnosis.
CT examinations can clearly show the size, extent, and relationship of the cyst to the surrounding tissue.
Retrograde aortography can show the abnormal arteries entering the lung tissue.
Bronchial iodine oil angiography can show less than 20%-25% of cysts because the viscous iodine agent does not easily pass through small draining bronchi, but sometimes it can show simultaneous ipsilateral or contralateral bronchial dilatation, which is helpful in deciding the scope and indications for lung resection.
Cyst puncture should be contraindicated because it can cause complications such as pneumothorax and abscess chest.
4.Differential diagnosis
(1) Post-pneumonia pulmonary alveoli: are acquired pulmonary cysts, mostly seen after pneumonia such as Staphylococcus aureus, and are more common in infants and children around 6 months of age. It is characterized by the formation of cystic lesions in the lungs, the walls of which are composed of alveolar flat squamous epithelium, the sacs contain gas, the size and shape of the cavity change within a short period of time, and their appearance and disappearance are rapid, and the alveoli often disappear on their own after the infection is controlled, which is absolutely different from the long-term existence of congenital pulmonary cysts.
(2) Pneumothorax: first there is a history of pneumonia such as fever and cough, and then deteriorates after the condition improves during treatment, with symptoms such as high fever and dyspnea. x-ray shows a fluid level in the chest cavity, and the lung tissue is compressed and pushed to the lung door. After closed drainage of the chest cavity, the lung reopens and the cavity disappears. Pneumothorax can also be formed after the rupture of pulmonary cystic cavity infection, but it does not close after closed drainage, which can be distinguished.
(3) Congenital diaphragmatic hernia: It occurs on the left side, with symptoms such as paroxysmal crying, vomiting and intra-thoracic bowel sounds in addition to dyspnea.
(4) Lung abscess: the symptoms are the same as those of pulmonary cysts secondary to infection, but the X-ray performance differs in that the wall of the lung abscess is thicker, the circumference is not clear, and the surrounding lung tissue is mostly infiltrated and fibrous, which can be gradually reduced by antibiotic treatment.
(5) Intrapulmonary spherical lesions: such as pulmonary metastases, pulmonary tuberculosis spheres, malformations, hemangiomas, arteriovenous fistulas, pericardial cysts, etc. should be distinguished from pulmonary cysts, which can be identified by X-ray examination, tomography, angiography, etc. Sometimes the diagnosis can be confirmed by post-surgical pathological examination.
(6) Tension pneumothorax: it should be distinguished from tension cyst. Physical signs and X-ray examination are sometimes difficult to identify. However, generally tension cysts have their main body in the lung, and the compressed lung tissue can be seen when the angle of the cribriform septum and the apical part of the lung are carefully observed, while tension pneumothorax often presses the lung toward the lung door.
(7) Large lobar emphysema; seen in the neonatal period, mostly with acute respiratory distress, but can also start slowly, with symptoms evident after 2-3 months of life, and is not easily distinguished from a giant tension-containing pneumothorax, both of which require surgical resection.
(8) Pulmonary isolation disease: Most of them are on the left side, located in the posterior septal angle and mediastinum, with well-defined boundaries, and are smooth, round masses on X-ray, not connected with bronchi, and asymptomatic. A few compress the lower lobe lung and show signs of compression. The aortogram shows abnormal arterial branches entering the shadow.
5. Treatment
Pulmonary cysts do not heal on their own, and infection, tension cysts, and pneumothorax may occur over time, complicating surgical treatment, so surgery should be performed as soon as possible after diagnosis. Age is not a contraindication to surgery, and symptoms in the neonatal period should also be treated by active surgery. It is even more important to operate promptly when the respiratory function is affected in infancy. Surgery is contraindicated if the lesion is extensive, pulmonary function is severely reduced, or if there are multiple bilateral pulmonary cysts.
Asymptomatic pulmonary cysts can be operated electively. Pulmonary cysts with co-infection should be operated after controlling the infection first. However, preoperative control of infection is the general principle, and individual cases need to be operated earlier depending on the specific situation, and tension cysts or complications of tension pneumothorax are indications for emergency surgery. In severe respiratory distress, a drainage tube can be inserted to the cyst for closed drainage, and then anesthesia and surgery can be performed after respiratory stabilization.
The surgery is performed by posterior lateral incision, and the extent of resection depends on the site, size, multiple or single lesions, and the presence or absence of concomitant lesions. Cysts located under the pleura can be removed simply by freeing the cyst along its wall and carefully ligating the vessels and bronchi connected to the cyst. Cysts confined to the marginal part of the lung may also be subjected to segmental lung resection or wedge resection of the lung. If the cyst is large, if there is too little normal lung tissue remaining in the affected lobe, or if a large air leak is left after removal of the cyst, lobectomy is feasible because of the strong compensatory capacity of the remaining lung in children after surgery. In polycystic lung, lobectomy or total pneumonectomy is performed depending on the extent of the lesion. Clinically, the lung tissue is seen to be extremely inflated and dilated, occupying the chest cavity, pale, spongy to touch, and not collapsed. The diseased lung should be quickly lifted out so that the remaining lung and surrounding tissues return to their original position, and the diseased lung should be removed by free ligation and severing the arteries, veins and bronchi of the diseased lobe respectively.
Large unicompartmental cysts can be tried for cyst debridement to preserve more normal lung tissue. In multiatrial cysts, the involved lung segments or lobes should be removed together. During surgery, attention should be paid to the abnormal arterial branches from the body circulation into the lung lobes, and abnormal venous branches are not uncommon, which should be carefully handled during surgery to avoid accidental bleeding.
Postoperative complications such as shock, hemorrhage, pulmonary edema, pulmonary atelectasis, abscess chest and bronchopleural fistula should be taken care of.
Congenital cystic adenoma-like malformation of the lung
Congenital cystic adenomatoid malformation of the lung is a rare anomaly of lung development. It was first reported as a unique pathology by Chin and Tang in 1949.
1. Etiology and pathology
Congenital cystic adenomatoid malformation used to be thought of as a malformation, but is now considered to be a limited lung dysplasia or anomaly, occurring as a mixture of cysts and adenomatoid malformations in different proportions, or all of them may be adenomatoid malformations. Enlargement of one lobe of one lung is often cystic, compressing the rest of the ipsilateral lung and often causing a mediastinal shift that compresses the contralateral lung. As a result of the occupying lesion, the rest of the ipsilateral lung tissue may be dysplastic. The incidence is slightly higher in males. The onset of disease may be due to embryonic damage, usually within the first 50 days of gestation, and appears to involve end-unseen bronchial tissue dysplasia. Cysts are common and cartilage is rare. The presence of cartilage may indicate embryonic damage at a slightly later time, perhaps extending to the 10th to 24th week.
The embryologic basis is similar to that of pulmonary cysts in that some of the cysts have abnormal proliferation of respiratory epithelium or mucous glands and sometimes may protrude papillary-like into the cystic cavity, much like an adenoma or malformation, hence the term cystic adenomatoid malformation. The entire lung lobe or multiple ipsilateral lobes appear mass-like to the naked eye, and the diseased lung is significantly enlarged, hard and purple in color with scattered pink inflatable areas under the pleura. There are 3 morphologies on section: (1) a single large cystic cavity with trabeculae in the cyst wall and diverticulae that penetrate deep into the parenchyma; (2) containing multiple small cysts of different sizes; (3) a substantial lobule with a clear contour to the surrounding and surrounding normal lung tissue. A few cysts are connected to the bronchi and often have abnormal blood vessels entering the diseased lung from outside the pulmonary hilum. The histological characteristics are: the end of the respiratory tract is differently cystic dilated, the inner wall is compounded with cuboidal epithelium and pseudostratified ciliated columnar epithelial cells; the cyst wall contains polyp-like mucosa and elastic fiber hyperplasia; lack of cartilage plate, a small amount of cartilage and smooth muscle tissue; the cyst wall is covered with mucus cells; no inflammatory manifestations.
2.Clinical manifestations
The disease can involve all lung lobes, but it is more common in the right lower lobe. Multilobe involvement is often bilateral. There are 3 types of clinical manifestations: (1) stillbirth or perinatal death, in which the cardiac function and venous blood return of the affected child are affected due to compression of the diseased lung. Half of the deceased infants have generalized edema and maternal amniotic fluid overload. In recent years, the diagnosis can be made at 18 weeks of gestation with the use of ultrasound; (2) progressive respiratory distress and cyanosis in the neonatal period, mostly caused by progressive emphysema of the diseased lung, and most patients die in the neonatal period; (3) a few children do not develop symptoms until childhood, with fever, chest pain, cough and episodes of pulmonary infection. Occasionally, the disease may be asymptomatic and may be detected only on X-ray. Some children may have dysplastic chest wall deformities.
3.Diagnosis
A chest x-ray reveals soft tissue shadows with clear margins in the lungs, interspersed with striated and nodular shadows, containing scattered irregular translucent areas, with the mediastinum and heart shifted to the opposite side. It is easily confused with diaphragmatic hernia in newborns, and should be differentiated from pulmonary isolation and post-pneumonia emphysema in older children.
4.Treatment
Surgery should be performed after the diagnosis is confirmed. Bilateral extensive lesions contraindicate surgery and can only be treated conservatively. Local resection is feasible in parenchymal cases, lobectomy in cases limited to one lobe of the lung, and total pneumonectomy in cases of multilobar lesions. Intraoperative care should be taken to deal with the abnormal blood vessels from the body circulation.