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Bronchiectasis

By Başak Çoruh, MD, Assistant Professor, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Washington ; Alexander S. Niven, MD, Adjunct Professor of Medicine;Senior Associate Consultant, Uniformed Services University of the Health Sciences;Division of Pulmonary and Critical Care Medicine, Mayo Clinic

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Bronchiectasis is dilation and destruction of larger bronchi caused by chronic infection and inflammation. Common causes are cystic fibrosis, immune defects, and recurrent infections, though some cases seem to be idiopathic. Symptoms are chronic cough and purulent sputum expectoration; some patients may also have fever and dyspnea. Diagnosis is based on history and imaging, usually involving high-resolution CT, though standard chest x-rays may be diagnostic. Treatment and prevention of acute exacerbations are with bronchodilators, clearance of secretions, antibiotics, and management of complications, such as hemoptysis and further lung damage due to resistant or opportunistic infections. Treatment of underlying disorders is important whenever possible.

Etiology

Bronchiectasis is best considered the common end-point of various disorders that cause chronic airway inflammation. Bronchiectasis may affect many areas of the lung (diffuse bronchiectasis), or it may appear in only 1 or 2 areas (focal bronchiectasis).

Diffuse bronchiectasis develops most often in patients with genetic, immunologic, or anatomic defects that affect the airways. In developed countries, many cases appear initially to be idiopathic, probably partly because onset is so slow that the triggering problem cannot be identified by the time bronchiectasis is recognized. With newer, improved genetic and immunologic testing, an increasing number of reports describe finding an etiology in these idiopathic cases after careful, systematic evaluation.

Cystic fibrosis (CF) is commonly associated with this condition, and previously undiagnosed CF may account for up to 20% of idiopathic cases. Even heterozygous patients, who typically have no clinical manifestations of CF, may have an increased risk of bronchiectasis.

Immunodeficiencies such as common variable immunodeficiency (CVID) may also lead to diffuse disease, as may rare abnormalities in airway structure. Undernutrition and HIV infection also appear to increase risk.

Congenital defects in mucociliary clearance such as primary ciliary dyskinesia (PCD) syndromes may also be a cause, explaining almost 3% of previously idiopathic cases.

Diffuse bronchiectasis sometimes complicates common autoimmune disorders, such as RA or Sjögren syndrome, and can occur in the setting of hematologic malignancy, organ transplant, or due to the immune compromise associated with treatment in these conditions.

Allergic bronchopulmonary aspergillosis, a hypersensitivity reaction to Aspergillus spp that occurs most commonly in people with asthma, but sometimes in patients with CF, can cause or contribute to bronchiectasis.

In developing countries, most cases are probably caused by tuberculosis, particularly in patients with impaired immune function due to undernutrition and HIV infection.

Focal bronchiectasis typically develops as a result of untreated pneumonia or obstruction (eg, due to foreign bodies, tumors, postsurgical changes, lymphadenopathy). Mycobacteria (tuberculous or nontuberculous) can both cause focal bronchiectasis and colonize the lungs of patients with bronchiectasis due to other disorders (see Table: Factors Predisposing to Bronchiectasis).

Factors Predisposing to Bronchiectasis

Category

Examples and Comments

Infections

Bacterial

Haemophilus influenzae

Pseudomonas aeruginosa

Moraxella catarrhalis

Staphylococcus aureus

Streptococcus pneumoniae

Mycoplasma pneumoniae

Bordetella pertussis

Klebsiella spp

Fungal

Aspergillus spp

Histoplasma capsulatum

Mycobacterial

Mycobacterium tuberculosis

Nontuberculous mycobacteria

Viral

Adenovirus

Herpes simplex virus

Influenza

Measles

Respiratory syncytial virus

Congenital disorders

Alpha1-antitrypsin deficiency

If severe, can cause bronchiectasis

Ciliary defects

Can cause bronchiectasis, sinusitis, otitis media, and male infertility

50% of patients with primary ciliary dyskinesia (PCD) have situs inversus

Kartagener syndrome (clinical triad of dextrocardia, sinus disease, situs inversus)

Cystic fibrosis

Causes viscous secretions due to defects in Na and Cl transport

Often complicated by P. aeruginosa or S. aureus colonization

Immunodeficiencies

Primary

Chronic granulomatous disease

Complement deficiencies

Hypogammaglobulinemia, particularly common variable immunodeficiency

Secondary

HIV infection

Hematologic malignancy

Immunosuppressants

Airway obstruction

Cancer

Endobronchial lesion

Extrinsic compression

Due to tumor mass or lymphadenopathy

Foreign body

Aspirated or intrinsic (eg, broncholith)

Mucoid impaction

Allergic bronchopulmonary aspergillosis

Postoperative

After lobar resection, due to kinking or twisting of remaining lobes

Connective tissue and systemic disorders

RA

Commonly causes bronchiectasis (frequently subclinical), more often in men and in patients with long-standing RA

Sjögren syndrome

Bronchiectasis possibly due to increased viscosity of bronchial mucus, which leads to obstruction, poor clearance, and chronic infection

SLE

Bronchiectasis in up to 20% of patients via unclear mechanisms

Inflammatory bowel disease

Bronchopulmonary complications occurring after onset of inflammatory bowel disease in up to 85% and before onset in 10 to 15%

Bronchiectasis more common in ulcerative colitis but can occur in Crohn disease

Relapsing polychondritis

Congenital structural defects

Lymphatic

Yellow nail syndrome

Tracheobronchial

Williams-Campbell syndrome (cartilage deficiency)

Tracheobronchomegaly (eg, Mounier-Kuhn syndrome)

Vascular

Pulmonary sequestration (a congenital malformation in which a nonfunctioning mass of lung tissue lacks normal communication with the tracheobronchial tree and receives its arterial blood supply from the systemic circulation)

Toxic inhalation

Ammonia

Chlorine

Nitrogen dioxide

Direct airway damage altering structure and function

Other

Transplantation

May be secondary to frequent infection due to immunosuppression

Diffuse panbronchiolitis

Rare syndrome involving bronchiolitis and chronic sinusitis

Adapted from Barker, AF: Bronchiectasis. The New England Journal of Medicine 346:1383–1393, 2002.

Pathophysiology

The pathophysiology of bronchiectasis is not fully understood, likely in part because it is the common end-point of a heterogenous group of disorders predisposing to chronic airway inflammation.

Diffuse bronchiectasis occurs when a causative disorder triggers inflammation of small and medium-sized airways, releasing inflammatory mediators from intraluminal neutrophils. The inflammatory mediators destroy elastin, cartilage, and muscle in larger airways, resulting in irreversible bronchodilation. Simultaneously, in the inflamed small and medium-sized airways, macrophages and lymphocytes form infiltrates that thicken mucosal walls. This thickening causes the airway obstruction frequently noted during pulmonary function testing.

With disease progression, inflammation spreads beyond the airways, causing fibrosis of the surrounding lung parenchyma. What inflames the small airways depends on the etiology of bronchiectasis. Common contributors include impaired airway clearance (due to production of thick, viscous mucus in CF, lack of ciliary motility in PCD, or damage to the cilia and/or airways secondary to infection or injury) and impaired host defenses; these factors predispose patients to chronic infection and inflammation. In the case of immune deficiency (particularly CVID), autoimmune inflammation may also contribute.

Focal bronchiectasis usually occurs when a large airway becomes obstructed. The resulting inability to clear secretions leads to a cycle of infection, inflammation, and airway wall damage. The right middle lobe is involved most often because its bronchus is small and angulated and has lymph nodes in close proximity. Lymphadenopathy due to mycobacterial infection sometimes causes bronchial obstruction and focal bronchiectasis.

As ongoing inflammation changes airway anatomy, pathogenic bacteria (sometimes including mycobacteria), colonize the airways. Common organisms include

  • Haemophilus influenzae: 35%

  • Pseudomonas aeruginosa: 31%

  • Moraxella catarrhalis: 20%

  • Staphylococcus aureus: 14%

  • Streptococcus pneumoniae: 13%

S. aureus colonization is strongly associated with CF; a culture finding of S. aureus should raise concern for undiagnosed CF. Also, colonization with P. aeruginosa tends to indicate severe disease and portends a rapid decline in lung function. Colonization by multiple organisms is common, and antibiotic resistance is a concern in patients who require frequent courses of antibiotics for treatment of exacerbations.

Complications

As the disease progresses, chronic inflammation and hypoxemia cause neovascularization of the bronchial (not the pulmonary) arteries. Bronchial artery walls rupture easily, leading to massive hemoptysis. Other vascular complications include pulmonary hypertension due to vasoconstriction, arteritis, and sometimes shunt from bronchial to pulmonary vessels.

Colonization with multidrug-resistant organisms can lead to chronic, low grade airway inflammation. This inflammation can progress, causing recurrent exacerbations and worsen airflow limitation on pulmonary function tests.

Symptoms and Signs

Symptoms characteristically begin insidiously and gradually worsen over years, accompanied by episodes of acute exacerbation.

The most common presenting symptom is chronic cough that produces thick, tenacious, often purulent sputum. Dyspnea and wheezing are common, and pleuritic chest pain can develop. In advanced cases, hypoxemia and right-sided heart failure due to pulmonary hypertension may increase dyspnea. Hemoptysis, which can be massive, occurs due to airway neovascularization.

Acute exacerbations are common and frequently result from new or worsened infection. Exacerbations are marked by a worsening cough and increases in dyspnea and the volume and purulence of sputum. Low-grade fever and constitutional symptoms (eg, fatigue, malaise) may also be present.

Halitosis and abnormal breath sounds, including crackles, rhonchi, and wheezing, are typical physical examination findings. Digital clubbing is uncommon but may be present. In advanced cases, signs of hypoxemia, pulmonary hypertension (eg, dyspnea, dizziness), and right-sided heart failure are common. Chronic rhinosinusitis and nasal polyps may be present, particularly in patients with CF or PCD. Lean body mass commonly decreases, possibly due to inflammation and cytokine excess and, in patients with CF, malabsorption.

Diagnosis

  • History and physical examination

  • Chest x-ray

  • High-resolution chest CT

  • Pulmonary function tests for baseline evaluation and monitoring disease progression

  • Specific tests for suspected causes

Diagnosis is based on history, physical examination, and radiologic testing, beginning with a chest x-ray. Chronic bronchitis may mimic bronchiectasis clinically, but bronchiectasis is distinguished by increased purulence and volume of daily sputum and by dilated airways shown on imaging studies.

Imaging

Chest x-ray is usually abnormal and may be diagnostic. X-ray findings suggestive of bronchiectasis involve thickening of the airway walls and/or airway dilation; typical findings include ill-defined linear perihilar densities with indistinctness of the central pulmonary arteries, indistinct rings due to thickened airways seen in cross section (parallel to the x-ray beam), and “tram lines” (or tram-track sign) caused by thickened, dilated airways perpendicular to the x-ray beam. Dilated airways filled with mucous plugs can also cause scattered elongated, tubular opacities.

Radiographic patterns may differ depending on the underlying disease; bronchiectasis due to CF develops predominantly in the upper lobes, whereas bronchiectasis due to an endobronchial obstruction causes more focal x-ray abnormalities.

High-resolution CT is the test of choice for defining the extent of bronchiectasis and is nearly 100% sensitive and specific. Typical CT findings include airway dilation (in which the inner lumen of 2 or more airways exceed the diameter of the adjacent artery) and the signet ring sign (in which a thickened, dilated airway appears adjacent to a smaller artery in transaxial view (see Figure: Bronchiectasis). Lack of normal bronchial tapering can result in visible medium-sized bronchi extending almost to the pleura. "Tram lines" are easily visible on CT.

As airway damage increases over time, bronchiectasis changes progress from cylindrical to varicose and then cystic findings on imaging. Atelectasis, consolidation, mucous plugs, and decreased vascularity are nonspecific findings. In traction bronchiectasis, pulmonary fibrosis pulls or distorts airways in ways that simulate bronchiectasis on imaging.

Pulmonary function tests

Pulmonary function tests can be helpful for documenting baseline function and for monitoring disease progression. Bronchiectasis causes airflow limitation (reduced forced expiratory volume in 1 sec [FEV1] with reduction in the FEV1/FVC ratio); the FEV1 may improve in response to beta-agonist bronchodilators. In more advanced cases, progressive fibrosis may result in decreases in forced vital capacity (FVC), evidence of a restrictive defect on lung volume measurements, and a decreased diffusing capacity for carbon monoxide (DLco).

Diagnosis of cause

During an exacerbation-free period, all patients should have expectorated or induced sputum cultured to determine the predominant colonizing bacteria and their sensitivities. This information helps with antibiotic selection during exacerbations.

A CBC and differential can help determine the severity of disease activity and identify eosinophilia, which may suggest complicating diagnoses. Staining and cultures for bacterial, mycobacterial (Mycobacterium avium complex and M. tuberculosis), and fungal (Aspergillus spp) organisms may also help identify the cause of chronic airway inflammation.

Clinically significant nontuberculous mycobacterial infection is diagnosed by finding high colony counts of these mycobacteria in cultures from serial sputum samples or from bronchoalveolar lavage fluid in patients who have granulomas on biopsy or concurrent radiologic evidence of disease.

When the cause of bronchiectasis is unclear, additional testing based on the history and imaging findings may be done. Tests may include the following:

  • Serum immunoglobulins (IgG, IgA, IgM) and serum electrophoresis to diagnose CVID

  • Targeted assessment of baseline and specific antibody responses to peptide and polysaccharide antigens (ie, tetanus, capsular polysaccharide of S. pneumoniae and H. influenzae type b) done to assess immune responsiveness

  • Two sweat chloride tests and CFTR gene mutation analysis to diagnose CF (including in adults > 40 yr without an identifiable cause of bronchiectasis, especially in the setting of upper lobe involvement, malabsorption, or male infertility)

  • Rheumatoid factor, ANA, and antineutrophil cytoplasmic antibody testing if an autoimmune condition is being considered

  • Serum IgE and Aspergillus precipitins if patients have eosinophilia, to rule out allergic bronchopulmonary aspergillosis

  • Alpha1-antitrypsin level to evaluate for alpha1-antitrypsin deficiency if high-resolution CT shows lower lobe emphysema

PCD should be considered if adults with bronchiectasis also have chronic sinus disease or otitis media, particularly if problems have persisted since childhood. Bronchiectasis in such patients may have right middle lobe and lingular predominance, and infertility or dextrocardia may be present. Diagnosis requires examination of a nasal or bronchial epithelial sample for abnormal ciliary structure using transmission electron microscopy.

The diagnosis of PCD should typically be done in specialized centers because evaluation can be challenging. Nonspecific structural defects can be present in up to 10% of cilia in healthy people and in patients with pulmonary disease, and infection can cause transient dyskinesia. Ciliary ultrastructure may also be normal in some patients with PCD syndromes, requiring further testing to identify abnormal ciliary function.

Bronchoscopy is indicated when an anatomic or obstructive lesion is suspected.

Evaluation of exacerbations

The degree of testing depends on the severity of the clinical presentation. For patients with mild to moderate exacerbations, repeat sputum cultures to confirm the causative organism and sensitivity patterns may be sufficient. These help narrow antibiotic coverage and exclude opportunistic pathogens.

For more severely ill patients, a CBC, chest x-ray, and possibly other tests may be warranted to exclude common complications of serious pulmonary infection, such as lung abscess and empyema.

Prognosis

Prognosis varies widely. Mean yearly decrease in FEV1 is about 50 to 55 mL (normal decrease in healthy people is about 20 to 30 mL). Patients with CF have the poorest prognosis, with a median survival of 36 yr, and most patients continue to have intermittent exacerbations.

Treatment

  • Prevention of exacerbations with regular vaccinations and sometimes suppressive antibiotics

  • Measures to help clear airway secretions

  • Bronchodilators and sometimes inhaled corticosteroids if reversible airway obstruction is present

  • Antibiotics and bronchodilators for acute exacerbations

  • Sometimes surgical resection for localized disease with intractable symptoms or bleeding

The key treatment goals are to control symptoms and improve quality of life, reduce the frequency of exacerbations, and preserve lung function.

As for all patients with chronic pulmonary disease, smoking cessation, annual influenza vaccination, and both pneumococcal 13-valent conjugate (PCV13) and polysaccharide vaccination (PPSV23) are recommended (see Pneumococcal Vaccine) for individuals with bronchiectasis. PPSV23 revaccination is recommended 5 yr later in patients who are < 65 at the time of their initial pneumococcal vaccination and for patients who are asplenic or immunosuppressed.

Airway clearance techniques are used to reduce chronic cough in patients with significant sputum production and mucous plugging and to reduce symptoms during exacerbations. Such techniques include regular exercise, postural drainage and chest percussion, positive expiratory pressure devices, intrapulmonary percussive ventilators, pneumatic vests, and autogenic drainage (a breathing technique thought to help move secretions from peripheral to central airways) (see Chest Physiotherapy). Patients should be taught these techniques by a respiratory therapist and should use whichever one is most effective and sustainable for them; no evidence favors one particular technique.

For patients with airway obstruction, bronchodilator therapy (eg, with some combination of a long-acting beta-adrenergic agonist, tiotropium, and a short-acting beta-adrenergic drug as indicated by symptoms and severity of lung obstruction, as used in patients with COPD) can help improve function and quality of life. Inhaled corticosteroids may also be used in patients with frequent exacerbations or marked variability in lung function measurements (ie, reversible airway obstruction following bronchodilator administration). Pulmonary rehabilitation can be helpful.

In patients with CF, a variety of nebulized treatments, including a mucolytic (rhDNase) and hypertonic (7%) saline, can help reduce sputum viscosity and enhance airway clearance. In patients without CF, evidence of benefit with these agents is inconclusive, so only humidification and saline are recommended as inhaled treatments. Inhaled terbutaline, dry powder mannitol, and mucolytics such as carbocysteine and bromhexine have mechanisms that might be expected to accelerate tracheobronchial clearance. However, most of these agents have had mixed results in limited trials in patients with and without CF.

There is no consensus on the best use of antibiotics to prevent or limit the frequency of acute exacerbations. Use of suppressive antibiotics regularly or on a rotating schedule reduces symptoms and exacerbations but may increase the risk that future infections will involve resistant organisms. Current guidelines suggest using antibiotics in patients with ≥ 3 exacerbations per year and possibly also in those with fewer exacerbations who have culture-proven P. aeruginosa colonization.

Chronic macrolide therapy reduces acute exacerbations in patients with bronchiectasis, and can slow the decline in lung function in patients with CF. For example, azithromycin, 500 mg po 3 times/wk has been used, but the optimal dose is unknown. Macrolides are thought to be beneficial mainly due to their anti-inflammatory or immunomodulatory effects.

Inhaled antibiotics (amikacin, aztreonam, ciprofloxacin, gentamicin, colistin, or tobramycin) can reduce sputum bacterial load, and may also reduce the frequency of exacerbations. The evidence supporting their use and benefit is strongest in the CF population.

Additional treatment depends on the cause. (For CF, see Cystic Fibrosis : Treatment.) Allergic bronchopulmonary aspergillosis is treated with corticosteroids and sometimes azole antifungals. Patients with immunoglobulin or alpha1-antitrypsin deficiencies should receive replacement therapy.

Acute exacerbations

Acute exacerbations are treated with antibiotics, inhaled bronchodilators (particularly if patients are wheezing), and increased attempts at mucus clearance, using mechanical techniques, humidification, and nebulized saline (and mucolytics for patients with CF). Inhaled or oral corticosteroids are frequently given to treat airway inflammation and worsening airway obstruction. Antibiotic choice depends on previous culture results and whether or not patients have CF. (See Cystic Fibrosis Pulmonary Guidelines: Treatment of Pulmonary Exacerbations.)

Initial antibiotics for patients without CF and with no prior culture results should be effective against H. influenzae, M. catarrhalis, S. aureus, and S. pneumoniae. Examples include amoxicillin/clavulanate, azithromycin, clarithromycin, and trimethoprim/sulfamethoxazole. Antibiotics should be adjusted based on culture results and given for a typical duration of up to 14 days. Patients with known P. aeruginosa colonization or more severe exacerbations should receive antibiotics effective against this organism (eg, ciprofloxacin 500 mg po bid, levofloxacin 500 mg po once/day for 7 to 14 days) until repeat culture results are available.

Initial antibiotic selection for patients with CF is guided by previous sputum culture results (done routinely in all patients with CF). During childhood, common infecting organisms are S. aureus and H. influenzae, and quinolone antibiotics such as ciprofloxacin and levofloxacin may be used. In the later stages of CF, infections involve highly resistant strains of certain gram-negative organisms including P. aeruginosa, Burkholderia cepacia, and Stenotrophomonas maltophilia. In patients with infections caused by these organisms, treatment is with multiple antibiotics (eg, tobramycin, aztreonam, ticarcillin/clavulanate, ceftazidime, cefepime). IV administration is frequently required.

Complications

Significant hemoptysis is usually treated with bronchial artery embolization, but surgical resection may be considered if embolization is ineffective and pulmonary function is adequate.

Superinfection with mycobacterial organisms such as M. avium complex almost always requires multiple drug regimens that include clarithromycin or azithromycin; rifampin or rifabutin; and ethambutol (see Other Mycobacterial Infections Resembling Tuberculosis). Drug therapy is typically continued until sputum cultures have been negative for 12 mo.

Surgical resection is rarely needed but may be considered when bronchiectasis is localized, medical therapy has been optimized, and the symptoms are intolerable. In certain patients with diffuse bronchiectasis, lung transplantation is also an option.

Five-year survival rates as high as 65 to 75% have been reported when a heart-lung or double lung transplantation is done. Pulmonary function usually improves within 6 mo, and improvement may be sustained for at least 5 yr.

Key Points

  • In bronchiectasis, chronic inflammation from various causes destroys elastin, cartilage, and muscle in larger airways, resulting in irreversible damage and dilated airways that are chronically colonized by infectious organisms.

  • Patients have chronic productive cough with intermittent acute exacerbations, usually 2 to 3 times/yr.

  • Diagnosis is with imaging, usually CT; cultures should be done to identify colonizing organism(s).

  • Prevent exacerbations using appropriate immunizations, airway clearance measures, and sometimes macrolide antibiotics.

  • Treat exacerbations with antibiotics, bronchodilators, more frequent airway clearance measures, and corticosteroids.

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