Etiology and pathogenesis
The main causes of bronchiectasis are bronchio-pulmonary tissue infections and bronchial obstruction. Bronchiectasis may also be caused by congenital developmental disorders and genetic factors, but is less common. Another 30% of patients with bronchiectasis have unknown causes, which may be related to genetic, immune imbalance or anatomical defects of the body.
I. Bronchial-lung tissue infection and obstruction Common viral and bacterial infections cause mucosal congestion and edema in the bronchial lumen, and secretion obstruction makes the lumen narrow, resulting in poor drainage and aggravating the infection, both of which interact with each other to promote the occurrence and development of bronchial dilatation. Pertussis, measles, and bronchopneumonia are the most common causes of bronchiectasis due to bronchio-pulmonary tissue infection in children. As the lumen of bronchi in children is thin, the wall is weak and easily obstructed. Repeated infections destroy the various layers of bronchial wall tissue, causing loss of elasticity, or fibrosis of lung tissue around the fine bronchi, pulling the wall, resulting in bronchial deformation and expansion. Chronic infection of the lung tissue or fibrous tissue pulling after the healing of tuberculosis lesions can also form bronchial dilatation. In addition, tumor, foreign body inhalation or extra-tubular enlarged lymph node compression can also lead to distal bronchial-lung tissue infection and bronchial dilatation.
Second, bronchial congenital developmental defects and genetic factors ① Bronchial congenital developmental disorders, such as giant tracheo-bronchomalacia, may be due to congenital connective tissue abnormalities and dilatation due to weakness of the tube wall. (ii) Localized weak or less flexible tube walls due to cartilage hypoplasia or insufficient elastic fibers, often associated with sinusitis and visceral transposition (right-sided heart), known as Kartagener’s syndrome, are often associated with bronchial dilatation. ③ Pulmonary cystic fibrosis and hereditary α1 antitrypsin deficiency related to genetic factors can both have bronchial mucous secretion retention, causing obstruction, pulmonary atelectasis and infection, and inducing bronchial dilatation.
Bronchiectasis may be related to immune dysfunction, and humoral immune defects are more likely to occur than cellular immune defects. Humoral immune deficiencies may lead to recurrent viral or bacterial infections due to the lack of IgA and/or IgG antibodies in their tracheobronchial secretions. In addition, immune-related diseases such as rheumatoid arthritis, Crohn’s disease, ulcerative colitis, systemic lupus erythematosus, bronchial asthma, and pan-bronchiectasis have been found to be associated with concomitant bronchiectasis.
Pathological changes
Bronchiectasis secondary to infectious lesions of the bronchio-pulmonary tissues is usually seen in the lower lobes of both lungs, and is more common in the left lower lobe than in the right lower lobe. The bronchi in the left lower lobe are elongated, have a large angle with the main trachea, and are compressed by the heart vessels, which makes them poorly drained and prone to infection. The opening of the lingual lobe bronchus is close to the dorsal segment of the lower lobe, which is easily involved by the infection of the lower lobe, so the left lower lobe and the lingual lobe bronchus are often dilated at the same time. Upper lobe bronchial dilatation is generally common in the apical and posterior segments and is mostly due to tuberculosis.
Bronchial dilatation can be classified as columnar or cystic depending on its shape, and is often mixed. Bronchial dilatation is often a result of destruction and inflammatory changes in the bronchial wall of a segment or subsegment, where the structures of the affected wall, including cartilage, muscle and elastic tissue, are destroyed and replaced by fibrous tissue. Thick purulent secretions may accumulate in the dilated bronchi, and their peripheral airways are often obstructed by secretions or replaced by fibrous tissue occlusion. The mucosal surface is often chronically ulcerated, with squamous or atrophic columnar ciliated epithelium, proliferation of cupped cells and mucus glands, and damage or loss of peribronchial connective tissue with microabscesses. Inflammatory cocoa causes increased vascularity in the bronchial wall, or the terminal branches of the bronchial arteries and pulmonary arteries dilate and anastomose, forming hemangiomas, and recurrent massive hemoptysis may occur. Bronchiectasis is prone to recurrent infections, and inflammation can spread to the adjacent lung parenchyma, causing varying degrees of pneumonia, small abscesses or lobar atelectasis, as well as pathological changes associated with chronic bronchitis.
Pathophysiology
In early stages, when lesions are mild and limited, pulmonary function measurements may be within normal limits. When the lesions are more extensive, they present as obstructive ventilation disorders. When the lesion is severe and widespread and involves the pleura, it presents as a mixed ventilation dysfunction with a predominantly obstructive nature. Intrapulmonary arteriovenous-like shunts, as well as diffusion dysfunction lead to hypoxemia. In a small number of patients, the disease progresses further, with pulmonary hypertension and complications of pulmonary heart disease.
Clinical manifestations
Bronchiectasis can occur at any age, but is more common in adolescents. Most patients have a history of measles, whooping cough, or bronchopneumonia in their early years, and some patients with bronchiectasis may have a history of chronic sinusitis or familial immunodeficiency.
I. Symptoms The typical symptoms are chronic cough, profuse pus sputum and recurrent hemoptysis.
(a) Chronic cough and copious pus sputum are related to the change of position, which is due to the accumulation of secretion at the site of bronchial dilatation and the cough and sputum discharge caused by the irritation of bronchial mucosa by the secretion when changing the position. The cough and sputum are often increased in the morning or at night when the patient is in bed and changes position. In acute attacks of infection, yellow-green pus sputum increases significantly and can reach hundreds of milliliters per day, and if the sputum has a foul odor, it indicates the combination of anaerobic bacterial infection. Sputum collected in a glass bottle at the time of infection appears to be characterized by stratification: foam in the upper layer, suspended purulent components in the lower layer, cloudy mucus in the middle layer, and necrotic tissue sediment in the lower layer. The common pathogens causing the infection are Pseudomonas aeruginosa, Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae and Catamorax.
(b) Recurrent hemoptysis 50% to 70% of patients have hemoptysis of varying degrees, and the amount of hemoptysis is sometimes inconsistent with the severity of the disease and the extent of the lesion. Some patients have recurrent hemoptysis as the only symptom without coughing or coughing up pus, which is clinically known as “dry bronchiectasis”, and the bronchiectasis is mostly located at the site of good drainage.
(iii) Recurrent pulmonary infections Characterized by recurrent pneumonia in the same lung segment and persistent. It is often caused by the downward spread of upper respiratory tract infection, with symptoms such as fever, increased cough, increased sputum, chest tightness and chest pain.
(iv) Chronic infection toxicity symptoms Repeated secondary infections may have systemic toxicity symptoms, such as fever, malaise, loss of appetite, emaciation, anemia, etc. In severe cases, shortness of breath and cyanosis may occur. In patients with severe bronchiectasis, due to purulent inflammation of peribronchial lung tissue and extensive fibrosis of lung tissue, obstructive emphysema and pulmonary heart disease may occur, followed by corresponding symptoms.
In addition, due to the continuous inflammatory response of the bronchi, some patients may develop reversible airflow obstruction and airway hyperresponsiveness, manifested as wheezing, dyspnea and cyanosis.
Early or dry bronchiectasis may have no abnormal pulmonary signs, but when the lesion is heavy or secondary to infection, fixed and persistent restricted coarse moist sounds in the lower chest and back can often be heard, sometimes croup can be heard, and some chronic patients are accompanied by pestle-like fingers (toes). Some chronic patients may have pestle-like fingers (toes). Signs may be present in the presence of complications such as emphysema and pulmonary heart disease.
Laboratory tests
I. X-ray examination ① Chest plain film: the sensitivity of plain film to bronchiectasis is poor. Early mild patients often have no special findings, and later may show a local increase and thickening of the lower lung texture on one or both sides, while the typical X-ray shows multiple irregular foveal translucent shadows in the coarse and disorganized lung texture or curly shadows along the bronchus, and the appearance of fluid planes in the shadows in case of infection; ②CT scan: the sensitivity and specificity of ordinary CT scan for the diagnosis of bronchiectasis are 66% and 92%, respectively, while the sensitivity of high-resolution CT (HRCT) has become the main diagnostic method for bronchiectasis, as the sensitivity and specificity of diagnosis can reach more than 90%. The characteristic manifestations are columnar dilatation with thickened walls or cystic changes in bunches and clusters; ③ Bronchial iodine oil imaging: it is the main basis for confirming the diagnosis of bronchial dilatation. It can determine the location, nature, extent and degree of bronchial dilatation, and provide a basis for surgical decision on the indication and scope of resection. However, because this technique is invasive, it has been replaced by CT.
Other examinations are useful for the visual or etiological diagnosis of bronchiectasis. Fiberoptic bronchoscopy can detect bleeding, dilated or obstructed areas, and local lavage can be performed for smear, bacteriological and cytological examination, and selective bronchography can be performed via fiberoptic bronchoscopy. Pulmonary function tests can confirm airflow limitation due to diffuse bronchiectasis or associated obstructive lung disease. Sputum examination often shows an abundance of neutrophils and a wide range of colonized or infected microorganisms. Sputum smear staining as well as sputum bacterial culture results may guide antibiotic therapy. Total leukocyte count and classification are generally in the normal range, with increased leukocytes and neutrophils in acute infections.
Diagnosis and differentiation
I. Diagnosis: Based on the clinical manifestations of recurrent purulent sputum and/or hemoptysis, combined with the history of respiratory tract infections that induce bronchiectasis in early childhood, a preliminary diagnosis can be made clinically, and a definite diagnosis of bronchiectasis can be made when HRCT shows abnormal imaging changes of bronchiectasis.
B. Differential diagnosis: Bronchiectasis is an irreversible lung damage, and the diseases that need to be differentiated from it are mainly chronic bronchitis, lung abscess, tuberculosis, congenital lung cyst, bronchopulmonary carcinoma and diffuse panbronchitis, etc. Careful study of medical history and clinical manifestations, as well as reference to the features of chest X-ray, HRCT, fiberoptic bronchoscopy and bronchography can often make a clear differential diagnosis.
Chronic bronchitis occurs mostly in middle-aged and elderly smoking patients, mostly white mucus sputum, usually purulent sputum only when the infection is acute, and mostly in winter and spring, recurrent hemoptysis is rare, and dry and moist woven wool with variable location can be heard at the bottom of both lungs.
Lung abscess starts rapidly with high fever, cough, and large amount of purulent sputum, and X-ray examination reveals a mass of lamellar shadows, in which there are cavities with fluid planes. After effective antibiotic treatment, the inflammation can be completely absorbed and dissipated.
Tuberculosis often has symptoms of tuberculosis toxicity such as low fever and night sweats, and the diagnosis can be made by X-ray chest X-ray and sputum tuberculosis examination.
Congenital pulmonary cysts are mostly found during physical examination or combined with acute infection, and multiple round or oval shadows with thin walls and no inflammatory infiltration of surrounding tissues can be seen in the lungs on X-ray examination, and chest CT examination and bronchography can help make the diagnosis.
V. Diffuse panbronchitis: there is chronic cough, coughing sputum, dyspnea during activity, usually without large amounts of pus sputum, often accompanied by chronic sinusitis, chest X-ray and chest CT show diffusely distributed small nodular shadows, macrolide antibiotic treatment is effective.
Disease treatment
Internal treatment of bronchiectasis is mainly to control infection and promote sputum drainage; surgical resection should be considered if necessary.
Internal treatment
In general, bronchiectasis is anatomically devastating and irreversible, so the goal of drug therapy is to control symptoms and slow the progression of the disease. Bronchiectasis is usually secondary to other diseases, so the primary disease should be treated promptly and the combined sinusitis should be treated thoroughly. Here, according to the condition, supportive treatment and reasonable rest should be strengthened, cold should be avoided, smoking cessation should be advised, and respiratory tract infections should be prevented.
(A) Control of infection Control of infection is the main treatment measure in the acute infection period of bronchiectasis. According to the condition, refer to the results of bacterial culture and drug sensitivity test to select antibacterial drugs, before the sputum culture results or when the sputum culture is negative, the following empirical scheme of antibiotics can be used. In mild cases, oral ampicillin or amoxicillin 0.5g four times a day or first or second generation cephalosporins can be used; in the presence of P. aeruginosa infection, oral quinolones can be chosen; in severe cases, intravenous combination drugs are often required. If there is anaerobic bacterial mixed infection, add metronidazole (methotrexate) or tinidazole.
(ii) Removal of sputum includes postural drainage and dilution of purulent sputum, and if necessary, aspiration via fiberoptic bronchoscope.
1.Physical drainage That is to elevate the lesion site, use gravity to drain the sputum to the pulmonary hilum, and then perform aspiration to eliminate the accumulated sputum and reduce secondary infection and toxic symptoms. Adopt suitable position according to the abscess site, so that the lesion is in high drainage, 2~4 times a day, 15~30 minutes each time. During postural drainage, cough sputum forcefully after intermittent deep breathing and pat the affected part; for those whose sputum is sticky and not easy to drain, dilute sputum by nebulized inhalation first, which is easy to drain; for patients with more sputum, prevent asphyxiation due to excessive gushing of sputum.
2.Dilute purulent sputum to facilitate sputum discharge. ①Expectorant: you can take bromhexine 8~16mg orally, 3 times a day, or aminophylline hydrochloride tablets 30mg orally, 3 times a day; ②Saline, ultrasonic nebulized inhalation can dilute sputum; ③When bronchospasm occurs, which affects sputum discharge, bronchodilators can be applied without hemoptysis, such as oral aminophylline 0.1g, 3~4 times a day or other slow-release theophylline preparations. If necessary, bronchodilator spray inhalation can be added.
3.Fiber bronchoscopic aspiration If it is still difficult to drain sputum in body position, sputum can be aspirated through fiber bronchoscope, and sputum can be diluted by saline flushing.
(iii) Anti-inflammatory therapy: chronic airway inflammation is an important pathogenic mechanism of bronchiectasis. Anti-inflammatory therapy has the potential to reduce airway inflammation and help repair damaged airway mucosa and cilia function. Currently, there are more studies on the anti-inflammatory effects of small doses of macrolides, especially for diffuse panbronchiolitis and bronchiectasis, which can reduce airway mucus secretion, disrupt the biofilm of Pseudomonas aeruginosa and reduce the number of episodes. Among them, erythromycin, roxithromycin, clarithromycin and azithromycin are effective in bronchiectasis. [4]
Surgical treatment
Recurrent acute lower respiratory tract infections or hemoptysis, lesions limited to one lung, not more than 2 lobes, not easily controlled by drug therapy, and in good general condition, lung segment or lobectomy can be performed according to the extent of the lesion. If the lesion is mild and the symptoms are not obvious, or if the lesion is more extensive involving both lungs, or if it is accompanied by severe respiratory impairment, surgical treatment is not recommended.
Disease prevention
Prevention and treatment of acute and chronic respiratory infections such as measles, whooping cough, bronchopneumonia and tuberculosis are important for the prevention of bronchiectasis. Patients with bronchiectasis should actively prevent respiratory tract infections, insist on postural sputum removal, and enhance the immune function of the body to improve its resistance to disease.