Bronchiectasis is the clinical term that defines the irreversible, progressive dilation, expansion, inflammation, and scarring of the bronchi (the tubes conducting air to the lungs), which eventually lead to airway obstruction and impaired mucociliary clearance, causing further damage.
Bronchiectasis often occurs secondary to another medical condition such as cystic fibrosis, sinopulmonary disorders, respiratory tract infections, and allergies. It results in distortion and damage to one or more of the conducting airways and generally involves a single lobe, a segment, or a sub-segment of the lungs.
Common symptoms include productive sputum along with a cough (occasionally tinged with blood), chest pain, shortness of breath, wheezing, and fatigue. Exacerbations (flare-ups) are common, especially with underlying bacterial infections, increased mucus production, more viscous sputum production, and worsening of respiratory and pulmonary functions.
Diagnosing bronchiectasis involves sputum culturing and analysis, chest radiography, computed tomography (CT) scanning, measuring vitamin D levels (a recent diagnostic measure), pulmonary function tests, and a physical exam to verify the underlying condition.
Treating the conditions includes combinations of bronchodilators, corticosteroids, and antibiotics (depending on the intensity and severity of the symptoms; anti-pseudomonal and anti-mycobacterial antibiotics are the common choices due to underlying cystic fibrosis or tuberculosis, respectively).
Supportive nutritional therapy, physical fitness, and maintenance of a healthy diet are equally important to increase the quality of life during and after therapy.
The causative agents of bronchiectasis can be broadly divided into two classes:
- Impaired mucociliary clearance due to dysfunctional cilia lead to bronchiectasis in many cases. Some of the major conditions associated with this include primary ciliary dyskinesia and Kartagener syndrome.
- Congenital immunodeficiency syndromes such as X-linked agammaglobulinemia — immunoglobulin A, G, E, and M (IgA,IgG, IgE, IgM, respectively) deficiencies — lead to impaired immune systems and immune dysfunctions. This leads to repeated pulmonary infections and an inability to clear the system, which in turn leads to bronchiectasis.
- Congenital anatomic defects, including Swyer-James syndrome (unilateral hyper lucent lung), Mounier-Kuhn syndrome (tracheobronchomegaly), Williams-Campbell syndrome (congenital cartilage deficiency), and others can lead to bronchopulmonary sequestration. This is a condition where a tissue developing in the lungs is not connected to the pulmonary artery supply and consequently is disconnected from the normal bronchial airway, interrupting pulmonary functions, eventually leading to lower-respiratory infections and bronchiectasis.
- Cystic fibrosis is another congenital, autosomal recessive condition which is detected in early or late childhood or in adults. It’s caused from a mutation in the cystic fibrosis transmembrane regulator (CFTR) protein, leading to impaired transport of sodium and chloride across membranes. This is accompanied by thick mucous that clogs the lungs and harbors harmful Pseudomonas aeruginosa, leading to bronchiectasis. Many cases of bronchiectasis are secondary to cystic fibrosis.
- Young’s syndrome is another genetic variation of cystic fibrosis, also found to be a contributor in the development of bronchiectasis.
- Bacterial infections are one of the primary causes that lead to the development of bronchiectasis. The most common bacteria involved include Staphylococcus aureus, Mycobacterium tuberculosis, Klebsiella pneumoniae, Hemophilus influenzae , Mycoplasma pneumoniae and Pseudomonas aeruginosa. Also contributing to the disease are viruses like measles, adenovirus, influenza, and herpes. Tuberculosis, apart from cystic fibrosis, is a pivotal condition leading to bronchiectasis.
- Non-tuberculous bacteria like those included within the Mycobacterium avium complex (MAC) has been recognized as a causative agent in women over age 6o with no other history of any pulmonary disorder.
- Non-cystic fibrosis bronchiectasis has been found to affect a certain population of people with chronic Pseudomonas and Hemophilus infections, where the bacteria lives in the airways, leading to biofilm formation and airway obstruction, eventually leading to bronchiectasis.
- HIV is another notable background condition recognized as responsible for the development of pulmonary disorders including bronchiectasis. A simple explanation might be the impaired and compromised immune system which makes the patients susceptible to all kinds of infections, with repeated exacerbations.
- Allergic bronchopulmonary aspergillosis (ABPA) is a condition manifested by the allergic reaction caused by the inhalation of the fungal spores of Aspergillus sp. The hyphae of these spores are found to clog the pulmonary airways, which cause excess mucus secretion and eventually lead to central-airway bronchiectasis (thin-walled bronchiectasis affecting the small and medium sized airway passages). A method to distinguish this particular condition from other types is the detection of eosinophilia — the deficiency, hypersensitivity and extreme reaction to inhaled corticosteroids.
- Aspirations, predisposed by altered mental status, leading to aspiration of unchewed food, peptic acid and microbes from the stomach, can lead to post-obstructive pneumonia and subsequent bronchiectasis.
- Bronchial obstruction caused as a result of non-malignant endobronchial tumors, bronchial stenosis from infections, mechanical traction from scarring of surrounding lung parenchyma, angulation of lobar bronchus (right or middle lobe obstruction), among others, also lead to development of bronchiectasis.
- Autoimmune and idiopathic inflammatory diseases like rheumatoid arthritis, ankylosing spondylitis, relapsing polychondritis, sarcoidosis, and systematic lupus erythematosus have also been noted as indirect precursors to the development of pulmonary disorders including endobronchial inflammation, pulmonary parenchymal scarring, and extrinsic compression of bronchi, all of them eventually leading to bronchiectasis.
- Connective tissue disorders like Marfan syndrome can also lead to bronchiectasis in a number of cases. An explanation of this is the weakening of the connective tissue constituting the broncho-pulmonary walls, which predisposes bronchiectasis.
- Other less common acquired causes include exposure to toxic gases, onset of an irritable bowel disease (Crohn’s disease) and alpha-1-antirypsin deficiency, which causes irreversible damage to bronchi, predisposing bronchiectasis.
No specific systemic data is available for the number of people affected by bronchiectasis. This may be due to the fact that it is most commonly recognized as a secondary complication to some of the major diseases, such as cystic fibrosis and tuberculosis. Also, because of non-specific symptoms, most cases are left underdiagnosed in their initial stages. Non-cystic fibrosis and atypical mycobacterial bronchiectasis affect around 50 percent of the patients associated with the condition.
Data from the 1980s suggests a total prevalence of 100,000 cases in the U.S., but this has gradually decreased since the introduction of vaccines and the spread of awareness for immunization in the 20th century. Generally, countries with greater access to medical benefits, higher socioeconomic status, and better education and awareness have a lower prevalence of the disease.
Apart from affecting children (congenital cases), bronchiectasis normally affects people older than 50, and is more common in women than men.
Signs and symptoms
The most common symptoms of bronchiectasis are the production of mucoid sputum, occurring in almost 90 percent of patients, with daily production of sputum being reported by more than 70 percent of patients. The sputum is generally colorless and odorless. Occasional production of blood-tinged sputum (hemoptysis) is also a possibility in patients with acute infection and damage to the pulmonary airway vasculature. Once infected by bacteria, the sputum can turn greenish, with an offensive odor.
At one time, the amount of sputum produced used to be a diagnostic indicator of the intensity of bronchiectasis. Now, however, radiographic exams are taken as the gold standard for diagnosis.
Other common symptoms include dyspnea, chest pain, wheezing, weight loss, and fatigue (from the increased energy required as a result of constant coughing). Fever might be an indicator on the onset of inflammation and acute infection.
Radiographic exams are the most commonly accepted means of diagnosis as far as broncho-pulmonary conditions are concerned. According to the recommendations by the British Thoracic Society, every case of non-cystic fibrosis should be confirmed by a computed tomography (CT) scan analysis.
For the complete assessment of a case of bronchiectasis, clinicians should check for the consistent production of sputum first, which is one of the major indicators of the disease. On a stethoscopic exam, the physician is most likely to find crackles in people with acute infection, and wheezing sounds in patients with airway obstruction and endobronchial damage. In patients with very severe forms of the disease, digital clubbing and cyanosis (as a result of respiratory obstruction) is observed.
A chest radiograph and CT scan shows the presence of a “tree-in-bud” appearance (which refers to airway obstruction in radiologic terms), which is another strong indicator of airway obstruction and subsequent bronchiectasis. The accuracy levels of high-resolution CT (HRCT) scans are very high with a sensitivity and specificity of 84 percent to 97 percent, and 82 to 99 percent, respectively. A typical finding in HRCT is the expansion of the bronchial lumen to 1.5 times the adjacent vessel.
A bronchoscopy is conducted when the radiographic findings are not accurate enough to confirm the condition. But this is very rare, given the high success rates of HRCT scans.
A medical history of the patient should be taken to check for pre-disposing conditions which could lead to bronchiectasis (cystic fibrosis, tuberculosis, respiratory tract infections, allergies, auto-immune disorders).
To confirm findings, the patient’s blood and sputum cultures should be analyzed. The patient’s immunoglobulin levels (IgM, IgA, IgG, IgE) should also be analyzed to detect an underlying immune deficiency (hypogammaglobulinemia). Patients with suspected cystic fibrosis undergo a sweat test to analyze the amount of sodium and chloride excreted through sweat.
Pulmonary function tests are conducted to detect the degree of damage to pulmonary functions as a result of bronchiectasis.
Treating bronchiectasis includes taking care of current symptoms, reducing their severity so that exacerbations aren’t as frequent (or are avoided completely, depending on the severity), and reducing morbidity and mortality by caring for the underlying conditions. Early diagnosis helps in planning a more effective therapeutic intervention.
Common medications prescribed by physicians include a combination of antibiotics, bronchodilators, expectorants (mucus thinning agents to improve mucociliary clearance), and free oxygen therapy if necessary. Surgical procedures are also conducted if necessary in severe cases.
For mild to moderate cases, oral and inhaled antibiotics are often preferred, but in cases of severe complications, intravenous doses are administered. Commonly used antibiotics include amoxicillin, tetracycline, trimethoprim-sulfamethoxazole, and macrolides.
In cases of cystic fibrosis-induced bronchiectasis, a stronger antibiotic regimen and an antipseudomonal synthetic penicillin, a third-generation cephalosporin, or a fluoroquinolone are often prescribed. For MAC-induced bronchiectasis, a combination of clarithromycin, rifampin, ethambutol, and possibly streptomycin are prescribed as standard therapy by the American Thoracic Society.
Additionally, physical means (use of percussion, vibrations, and shaking, to dislodge sputum from the chest walls) might be performed in cases of emergency to clear chest congestion.
Surgical intervention is sometimes necessary in people with severe complications. Indicators for surgical interference include extreme hemoptysis, an ineffective treatment regimen with antibiotics, presence of a foreign body or a non-malignant tumor, severe infections with MAC, Pseudomonas or Aspergillus sp.
Maintaining a healthy lifestyle contributes to lower morbidity, mortality rates, and an increased lifespan for patients. This incluedes not smoking and not coming in contact with second-hand smoke, vaccinations against pneumonia and influenza, and adequate nutritional supplements and hydration.