Lung cyst is a pathological cavity in the lung parenchyma filled with air or liquid contents. The course of a lung cyst can be asymptomatic, clinically pronounced (with shortness of breath, cough, heaviness and chest pain) and complicated (infection, pneumothorax, bleeding, etc.). The main diagnosis of the cyst is X-ray, including an overview chest x-ray, CT of the lung, angiopulmonography, bronchography. Treatment of pulmonary cysts is mainly surgical – cyst removal or lung resection by thoracotomy or videothoracoscopic intervention.
Lung cysts are called intrapulmonary cavities of polyethological origin, usually containing mucous fluid or air. Due to the wide variety of pathomorphological forms of the disease, it is quite difficult to judge the true prevalence of lung cysts in the population. According to some researchers, among all patients with respiratory diseases, patients with lung cysts account for 2.9-5.3%. Lung cysts are found in representatives of all ages: from newborn infants to the elderly. Despite its good quality, with a complicated course, a lung cyst can pose a serious threat to life, therefore, in pulmonology, surgical treatment tactics are used in relation to these pathological formations.
Lung cyst causes
The origin of congenital and dysontogenetic lung cysts is associated with defects in the formation of the lung in the embryonic period. Most often, such intrauterine disorders include alveolar agenesis, expansion of terminal bronchioles, or delayed formation of peripheral bronchi. Pulmonary cysts are a structural component of such congenital anomalies of lung development as:
- cystic hypoplasia
- congenital lobular emphysema
- McLeod syndrome and a number of others.
Among dysontogenetic lung cysts, dermoid cysts and cystic lymphangiomas are the most frequent, which are also often considered as benign lung tumors.
Acquired lung cysts formed in the outcome of diseases of parasitic, infectious and nonspecific (post-inflammatory, post-traumatic) and other genesis are more common in the practice of thoracic surgeons. Among the parasitic and infectious cysts are those that form in the lungs with echinococcosis, cysticercosis, tuberculosis, syphilis. The causes of other cysts may be inflammatory and destructive processes: pneumonia, lung abscess, bacterial destruction of the lung, injuries and wounds of the lung, bronchial obstruction, etc.
According to morphological features, lung cysts are divided into true and false. The first of them are always congenital, their outer shell is represented by connective tissue with elements of the bronchial wall (cartilaginous plates, smooth muscle and elastic fibers, etc.). The inner layer of a true lung cyst is formed by an epithelial lining of cells of cubic and cylindrical epithelium producing mucous secretions (bronchogenic cysts) or alveolar epithelium (alveolar cysts). False cysts are acquired in nature, and there are no structural elements of the bronchus and mucous membrane in their wall.
Depending on the etiopathogenesis (origin and mechanisms of formation), congenital, dysontogenetic and acquired lung cysts are distinguished.
- Congenital cysts are formed in the antenatal period, and the child is born with the presence of this lung malformation. Such cysts are usually detected in childhood. These include: cystic hypoplasia of the lungs, bronchiolar emphysema of the lungs, cystically altered accessory lung, intra-lobular sequestration, congenital giant cysts.
- Dysontogenetic lung cysts are also congenital formations caused by a violation of the development of bronchopulmonary kidneys in embryogenesis. However, the development of dysontogenetic cysts begins already in the postnatal period, so the pathology can be detected at different ages. Such formations include dermoid cysts, bronchogenic cysts, bronchogenic lung cysts.
- Acquired cysts are formed at a certain stage of life under the influence of diseases and injuries of the lungs. These include echinococcal lung cyst, bullous emphysema, pneumocele, tuberculous caverns, “melting lung”, emphysematous bullous lung sequestration, etc.
Taking into account the number of cavities, cysts are divided into single (solitary) and multiple (in the latter case, polycystic lung disease is diagnosed). If the cyst communicates with the bronchial lumen, it is called open; in the absence of such a message, they speak of a closed lung cyst. According to the type of content, there are air and filled cavities; according to the size of the cavity – small (up to 3 segments), medium (3-5 segments) and large (more than 5 segments). Finally, the course of lung cysts can be uncomplicated and complicated.
Lung cyst symptoms
Small and uncomplicated lung cysts are asymptomatic. Clinical signs appear with an increase in the size of cysts and compression of surrounding structures or due to a complicated course. Large or multiple cysts are accompanied by heaviness and chest pain, cough, shortness of breath, and sometimes dysphagia.
The transition from an asymptomatic to a complicated course can be initiated by ARVI or pneumonia. With suppuration of the lung cyst, signs of severe intoxication (weakness, adynamia, anorexia) and hectic fever come to the fore. Against the background of general malaise, a cough with mucopurulent sputum occurs, hemoptysis is possible.
The breakthrough of a pus-filled cyst into the bronchus is accompanied by coughing up copious, sometimes fetid sputum, improving the general condition, reducing intoxication. The cyst cavity is freed from pus, but its complete obliteration rarely occurs. More often, the disease acquires a recurrent course, gradually leading to the formation of secondary bronchiectasis and diffuse pneumofibrosis.
When the contents of the cyst break into the pleural cavity, a clinic of spontaneous pneumothorax, pyothorax, pleurisy may develop. Complications of this type are characterized by the sudden appearance of chest pain, severe, paroxysmal cough, increasing cyanosis, tachycardia and shortness of breath. Possible outcomes of such complications may be the formation of a bronchopleural fistula and chronic empyema of the pleura.
The inflammatory process in the bronchus draining the cyst contributes to the formation of a valve mechanism, leading to an increase in pressure inside the cyst cavity and its tension. The cyst rapidly increases in size, squeezes the surrounding segments of the lung, causes displacement of the mediastinal organs. The clinical picture of a strained lung cyst resembles a clinic of valvular pneumothorax (shortness of breath, tachypnea, cyanosis, swelling of neck veins, tachycardia). The severe condition of the patients is due to respiratory failure and hemodynamic disorders. During a stressed lung cyst, compensated, subcompensated and decompensated stages are distinguished. In addition to all of the above, a lung cyst can be complicated by pulmonary bleeding and malignancy. With draining cysts in children, there is a threat of asphyxia.
Due to the absence or scarcity of symptoms, uncomplicated lung cysts usually remain unrecognized. They can become an accidental find during preventive fluorography. Physical data may include shortening of percussion sound, weakening of breathing, sometimes “amphoric” breathing.
The main role in the detection of lung cysts belongs to the methods of X-ray diagnostics. The changes detected by lung x-ray are due to the type and origin of cysts. Usually, the formation of a spherical shape with clear contours is detected. A horizontal fluid level is sometimes visible in the cyst cavity. To clarify the localization and origin of cysts, MSCT and MRI of the lungs are used.
The results of bronchography are the most informative in the diagnosis of open lung cysts, when it is possible for a contrast agent to enter the cavity. With closed cysts, bronchography and angiopulmonography can detect a cyst by indirect signs – in this case, the bronchi and vessels will bend around the rounded shadow in the lung. Confirmation of the diagnosis can be achieved during diagnostic thoracoscopy.
Lung cysts should be differentiated with benign and malignant lung tumors of peripheral localization, lung metastases, tuberculoma, blocked abscess, limited pneumothorax, coelomic pericardial cyst, mediastinal tumors, etc.
Lung cyst treatment
Therapeutic tactics in relation to lung cysts are mainly surgical. Uncomplicated lung cyst should be removed as planned. At the same time, surgical intervention should not be delayed, since the occurrence of complications can transfer the status of the operation to the category of emergency, which can negatively affect the prognosis and survival. Most often, with uncomplicated variants of the disease, isolated cyst removal or economical lung resection is performed. The operation is performed both by thoracotomy and with the use of videothoracoscopy. With common processes (polycystic, secondary irreversible changes in parenchyma), lobectomy or pneumonectomy can be performed.
In case of lung cysts complicated by suppuration, preoperative drug preparation is carried out, and surgical intervention is performed after relief of the exacerbation. In case of development of pio- or pneumothorax, emergency drainage of the pleural cavity is performed, followed by local and systemic antibiotic therapy. Emergency care for a strained lung cyst complicated by respiratory insufficiency consists in urgent puncture and transthoracic drainage of the cyst under ultrasound control. In all these cases, surgical intervention is carried out in the second stage and is more radical in nature.
Prognosis and prevention
The prognosis for the planned treatment of uncomplicated lung cyst is favorable; long-term postoperative results are good. In the case of a complicated course, the outcome depends on the timing and completeness of primary care. In the acute period, the death of patients can occur from respiratory and cardiovascular insufficiency, massive bleeding; postoperative mortality reaches 5%. In other cases, disability is possible due to persistent secondary changes in the lungs (bronchiectasis, widespread pneumofibrosis, chronic purulent processes). Such patients require lifelong dispensary observation of a pulmonologist. Prevention of acquired lung cysts is to prevent injuries, specific and nonspecific lung diseases.