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Summary Table

Domain	Details
Risk Factors	Cystic fibrosis (most common cause in developed countries), prior severe lower respiratory infections (TB, pertussis, measles), primary ciliary dyskinesia (Kartagener syndrome), immunodeficiency (CVID, HIV), allergic bronchopulmonary aspergillosis (ABPA), foreign body aspiration, rheumatoid arthritis, inflammatory bowel disease
Etiology	Permanent, irreversible dilation of bronchi caused by a self-perpetuating cycle of infection, chronic inflammation, and destruction of the bronchial wall's muscular and elastic components
Patient Presentation	Chronic daily productive cough with copious purulent or mucopurulent sputum (often described as "cupfuls"), recurrent respiratory infections, progressive dyspnea, intermittent hemoptysis
Classic Physical Exam	Persistent coarse crackles that do not clear with coughing, wheezing, digital clubbing (in advanced or long-standing disease), rhonchi
Key Diagnostic Results	High-resolution CT (HRCT) showing dilated airways with a broncho-arterial ratio > 1 (signet ring sign), tram-track opacities, lack of normal bronchial tapering; sputum culture often growing Pseudomonas aeruginosa or Haemophilus influenzae
Management	Aggressive airway clearance (chest physiotherapy), prolonged antibiotics for acute exacerbations, treatment of the underlying cause, inhaled bronchodilators, consideration of macrolide prophylaxis for frequent exacerbators, surgical resection for localized refractory disease or life-threatening hemoptysis
Keywords	"Copious foul-smelling sputum," "recurrent pneumonias in the same lobe," "signet ring sign on CT," "tram-track lines," "digital clubbing with chronic cough," "situs inversus with recurrent sinusitis" (Kartagener)

1. Pathophysiology

Bronchiectasis is the end result of a vicious cycle involving three interdependent elements: airway obstruction, chronic infection, and inflammatory tissue destruction. Understanding this cycle is central to answering exam questions because almost every clinical feature and management decision traces back to it.

The cycle begins when an initial insult damages the bronchial wall or impairs mucociliary clearance. This insult may be an infection (e.g., childhood pertussis, tuberculosis), a genetic defect in ciliary motility (primary ciliary dyskinesia), abnormal mucus viscosity (cystic fibrosis), or an immune deficiency that prevents effective pathogen clearance. Once clearance is impaired, mucus stasis occurs, creating a favorable environment for bacterial colonization. The organisms most commonly implicated are Haemophilus influenzae (early disease) and Pseudomonas aeruginosa (advanced or long-standing disease). The presence of Pseudomonas on sputum culture is a prognostic marker associated with more rapid decline in lung function.

Persistent bacterial colonization triggers a neutrophil-dominant inflammatory response. Neutrophils release proteases (particularly elastase) and reactive oxygen species that damage the elastic and muscular layers of the bronchial wall. This structural destruction causes the airway to become permanently dilated and floppy, losing its ability to effectively propel mucus outward. The dilated, damaged airway then traps even more mucus, perpetuating infection and further inflammation. This is why the condition is irreversible once established.

The chronic inflammation also leads to bronchial artery hypertrophy. These hypertrophied systemic vessels are fragile and prone to rupture, which explains why hemoptysis is a common and sometimes life-threatening complication of bronchiectasis. On exam, a patient with known bronchiectasis presenting with sudden large-volume hemoptysis should prompt concern for bronchial artery bleeding, and the next best step is bronchial artery embolization if the bleeding is severe.

The pathophysiology also explains the physical exam findings. Coarse crackles result from air passing through mucus-filled, dilated airways. Digital clubbing develops in chronic disease due to prolonged hypoxemia and circulating growth factors. Foul-smelling sputum reflects anaerobic bacterial overgrowth in stagnant mucus pools.

2. Classification and Clinical Manifestation

Morphologic Classification (Reid Classification)

This classification is based on HRCT appearance and carries prognostic significance.

Type	HRCT Appearance	Clinical Correlation
Cylindrical (tubular)	Uniformly dilated airways that fail to taper toward the periphery; "tram-track" lines on longitudinal view, "signet ring sign" on cross-section	Most common form; often seen in early or mild disease; may be partially reversible if the underlying cause is treated promptly
Varicose	Irregular, beaded dilation of airways resembling varicose veins; alternating areas of dilation and constriction	Intermediate severity; less common
Cystic (saccular)	Cluster of thin-walled cysts at the end of bronchi, often with air-fluid levels	Most severe form; associated with advanced disease, frequent infections, and higher risk of hemoptysis

Clinical Manifestation by Disease Phase

Phase	Manifestation
Stable / Baseline	Daily productive cough with purulent sputum, mild dyspnea on exertion, occasional blood-streaked sputum, baseline coarse crackles
Acute Exacerbation	Increased sputum volume and purulence, worsening dyspnea, fever, new or worsening crackles/wheezing, decline in $FEV_1$, possible hemoptysis; often triggered by new bacterial or viral infection
Advanced / End-stage	Chronic respiratory failure, cor pulmonale, recurrent severe hemoptysis, persistent Pseudomonas colonization, progressive weight loss, digital clubbing

Distribution Pattern as a Clue to Etiology

Distribution	Suggested Etiology
Upper lobe predominant	Cystic fibrosis, post-tuberculosis, ABPA
Lower lobe predominant	Idiopathic, primary ciliary dyskinesia, recurrent aspiration, immunodeficiency
Focal / single lobe	Post-obstructive (tumor, foreign body), post-infectious (childhood pneumonia)
Diffuse / bilateral	Cystic fibrosis, primary ciliary dyskinesia, CVID, ABPA

3. Diagnostic Workup

Test	Role	Key Findings
Chest X-ray	Initial screening test	Tram-track opacities (thickened bronchial walls seen in longitudinal section), ring shadows, increased bronchovascular markings; may be normal in early disease
HRCT of the chest	Gold standard / confirmatory test	Bronchial dilation with broncho-arterial ratio > 1 (signet ring sign), lack of bronchial tapering, visualization of airways within 1 cm of the pleural surface, mucus plugging, tree-in-bud pattern
Sputum culture	Identify colonizing and infecting organisms	H. influenzae (early), Pseudomonas aeruginosa (advanced), Aspergillus species (if ABPA suspected)
Pulmonary function tests	Assess functional severity	Obstructive pattern ($\downarrow FEV_1$, $\downarrow FEV_1/FVC$); mixed obstructive-restrictive in advanced disease
Sweat chloride test	Rule out cystic fibrosis	Sweat chloride $\geq 60\ mmol/L$ is diagnostic of CF; should be ordered in any young adult with unexplained bronchiectasis
Serum immunoglobulins (IgG, IgA, IgM)	Screen for immunodeficiency	Low levels suggest CVID or other humoral immune defect
Total IgE + Aspergillus-related testing	Evaluate for ABPA	Elevated total IgE (> 1000 IU/mL), positive Aspergillus-related IgE, serum precipitins, peripheral eosinophilia
Nasal nitric oxide / ciliary biopsy	Evaluate for primary ciliary dyskinesia	Low nasal NO; electron microscopy showing outer dynein arm defects

The best initial test when bronchiectasis is suspected clinically is a chest X-ray. However, CXR has limited sensitivity; it can appear normal in mild or early cases. When the clinical picture is suggestive (chronic productive cough, recurrent infections, hemoptysis) and the CXR is either abnormal or inconclusive, the next step is HRCT of the chest without contrast.

HRCT is the gold standard for diagnosing bronchiectasis. The hallmark finding is the signet ring sign, where the dilated bronchus (the "ring") is seen adjacent to its accompanying pulmonary artery (the "stone"), and the bronchus is larger than the artery. Normally, the broncho-arterial ratio is approximately 1:1; in bronchiectasis, this ratio exceeds 1. Other HRCT findings include airways visible within 1 cm of the costal pleura (normally airways taper and are not visible this far out) and the "tree-in-bud" pattern suggesting mucoid impaction of small airways.

Once the diagnosis is confirmed, the workup shifts to identifying the underlying cause, because treatment of the etiology can slow disease progression. This is a commonly tested concept. Every patient with newly diagnosed bronchiectasis should have: sputum cultures (to guide antibiotic therapy), serum immunoglobulin levels (to rule out CVID), and a sweat chloride test in patients under 40 or those with upper-lobe predominant disease (to rule out cystic fibrosis). If the distribution is upper-lobe predominant and there is peripheral eosinophilia, ABPA workup is warranted. If situs inversus or chronic sinusitis accompanies the bronchiectasis, evaluate for primary ciliary dyskinesia (Kartagener syndrome).

Pulmonary function testing is performed to assess baseline severity and monitor progression. The expected pattern is obstructive ($\downarrow FEV_1/FVC$ ratio), though advanced disease can produce a mixed pattern.

4. Management and Treatment

Setting	Intervention	Details
All patients (baseline)	Airway clearance techniques	Chest physiotherapy, postural drainage, oscillatory PEP devices, flutter valve; performed daily
All patients	Treat the underlying cause	CF: CFTR modulators, pancreatic enzymes; ABPA: systemic corticosteroids + antifungals; CVID: immunoglobulin replacement; obstruction: bronchoscopic removal
Acute exacerbation	Empiric antibiotics	Amoxicillin-clavulanate 875/125 mg PO BID for 14 days if no prior Pseudomonas; if Pseudomonas is known or suspected: ciprofloxacin 500-750 mg PO BID for 14 days, or IV anti-pseudomonal beta-lactam (piperacillin-tazobactam, cefepime) for severe cases
*Chronic Pseudomonas* colonization**	Inhaled antibiotics	Inhaled tobramycin (300 mg nebulized BID, 28 days on / 28 days off cycles) or inhaled colistin
Frequent exacerbations ($\geq 3$/year)	Macrolide prophylaxis	Azithromycin 250 mg PO daily or 500 mg PO three times per week for a minimum of 6-12 months; acts via anti-inflammatory and immunomodulatory properties rather than purely antimicrobial effect
Airflow obstruction	Bronchodilators	Inhaled short-acting beta-agonists (albuterol) PRN; long-acting bronchodilators if concurrent COPD features
Severe hemoptysis	Bronchial artery embolization	First-line for acute life-threatening hemoptysis; surgical resection if embolization fails or is unavailable
Localized refractory disease	Surgical resection (lobectomy)	Reserved for focal disease that fails medical therapy, recurrent severe infections confined to one lobe, or recurrent life-threatening hemoptysis from a localized source
End-stage bilateral disease	Lung transplantation	Considered when $FEV_1$ falls below 30% predicted despite optimal medical therapy; CF-related bronchiectasis is one of the leading indications for bilateral lung transplant

Airway clearance is the cornerstone of bronchiectasis management and should be prescribed for every patient regardless of severity. The goal is to break the vicious cycle by mechanically removing stagnant, infected mucus. This is performed at least once or twice daily. Options include manual chest percussion with postural drainage, oscillatory positive expiratory pressure (PEP) devices, high-frequency chest wall oscillation vests, and active cycle breathing techniques. On exam, if asked about the "most important non-pharmacologic intervention," airway clearance is the answer.

For acute exacerbations, the standard antibiotic course is 14 days (longer than typical community-acquired pneumonia treatment). Initial empiric coverage should be guided by prior sputum culture results. In patients without a history of Pseudomonas, amoxicillin-clavulanate is a reasonable first-line oral agent. In patients with documented or suspected Pseudomonas colonization, oral ciprofloxacin is used for mild to moderate exacerbations, and IV anti-pseudomonal agents (piperacillin-tazobactam, cefepime, or meropenem) are reserved for severe exacerbations or treatment failure.

Macrolide prophylaxis with azithromycin is one of the most testable management points. It is indicated in patients with three or more exacerbations per year despite optimized airway clearance. The benefit comes primarily from the drug's anti-inflammatory and immunomodulatory effects (reduction of neutrophilic inflammation, inhibition of biofilm formation), not purely from its antibacterial activity. Before initiating long-term azithromycin, sputum cultures must be sent for acid-fast bacilli (AFB) to rule out nontuberculous mycobacterial (NTM) infection, because macrolide monotherapy in NTM disease promotes resistance and complicates future treatment.

Inhaled corticosteroids are generally not recommended for bronchiectasis unless there is coexisting asthma or ABPA. Mucolytics such as hypertonic saline (7% nebulized) can be used to improve mucus clearance, but recombinant DNase (dornase alfa) is only indicated in cystic fibrosis-related bronchiectasis and is actually harmful in non-CF bronchiectasis. This is a commonly tested distinction.

For life-threatening hemoptysis, the immediate step is hemodynamic stabilization, positioning the patient with the bleeding side down, and pursuing bronchial artery embolization. Surgical resection is a second-line option if embolization is unsuccessful or technically not feasible.

5. Differential Diagnosis and Distractors

Differential	Why It Looks Similar	Key Discriminator
Chronic obstructive pulmonary disease (COPD)	Chronic cough, sputum production, obstructive PFTs, history of recurrent exacerbations	COPD sputum is typically mucoid and less voluminous; HRCT shows emphysematous changes (centrilobular lucencies, flattened diaphragms) rather than dilated airways with signet ring sign; smoking history is the dominant risk factor in COPD
Chronic bronchitis	Daily productive cough for $\geq 3$ months in 2 consecutive years, obstructive physiology	Chronic bronchitis is a clinical diagnosis defined by symptom duration; sputum is mucoid, not copious or purulent; HRCT does not show permanent bronchial dilation; no signet ring sign
Lung abscess	Foul-smelling sputum, fever, cavitary lesion on imaging, chronic course	Lung abscess presents as a single thick-walled cavity with air-fluid level, not diffuse bronchial dilation; history often includes aspiration risk (alcoholism, altered consciousness, poor dentition)
Tuberculosis	Chronic cough, hemoptysis, upper-lobe cavitary disease, weight loss	TB presents with constitutional symptoms (night sweats, weight loss), positive AFB smear/culture, and upper-lobe cavities on CXR; can coexist with or cause bronchiectasis, but the primary diagnosis hinges on microbiologic confirmation
Allergic bronchopulmonary aspergillosis (ABPA)	Central bronchiectasis, recurrent wheezing, mucus plugging, elevated IgE	ABPA is actually a cause of bronchiectasis, not an alternative diagnosis; differentiated by central bronchiectasis (rather than peripheral), markedly elevated total IgE, positive Aspergillus serology, and history of asthma
Cystic fibrosis	Young patient with recurrent lung infections, upper-lobe bronchiectasis, Pseudomonas colonization	CF should be considered in any young adult with unexplained bronchiectasis; differentiated by sweat chloride $\geq 60\ mmol/L$, pancreatic insufficiency (steatorrhea, malnutrition), male infertility, and positive CFTR genetic testing
Primary ciliary dyskinesia (Kartagener syndrome)	Recurrent sinopulmonary infections, bronchiectasis from childhood	Triad of situs inversus + bronchiectasis + chronic sinusitis; diagnosis confirmed by nasal nitric oxide measurement (low) and electron microscopy of cilia (outer dynein arm defects)

6. Traps and High-Yield Pearls

The most common way students lose points on bronchiectasis questions is by confusing it with COPD or chronic bronchitis when the vignette describes a patient with chronic productive cough and obstructive PFTs. The discriminating clue is the character and volume of sputum: bronchiectasis produces large quantities of purulent, often foul-smelling sputum ("cupfuls per day"), while COPD and chronic bronchitis produce modest amounts of mucoid sputum. If the vignette mentions "daily production of large volumes of purulent sputum" or "recurrent pneumonias in the same anatomic distribution," that is the signal pointing toward bronchiectasis rather than COPD.

Another classic trap involves the diagnostic test. Students often select bronchoscopy or CXR as the confirmatory test. The gold standard is always HRCT of the chest. CXR is the initial screening tool but lacks sensitivity. Bronchoscopy has a role in ruling out endobronchial obstruction in focal bronchiectasis but is not the confirmatory imaging modality.

A third trap involves dornase alfa (recombinant DNase). Students who associate this drug with "mucus clearance in bronchiectasis" may select it as a correct treatment. Dornase alfa is only indicated in cystic fibrosis-related bronchiectasis. In non-CF bronchiectasis, it has been shown to worsen outcomes and is contraindicated. Hypertonic saline (nebulized 7%) is the appropriate mucolytic alternative in non-CF disease.

A fourth high-yield pearl involves macrolide prophylaxis. Before starting long-term azithromycin, you must rule out NTM infection with AFB sputum cultures. Macrolide monotherapy in undiagnosed NTM disease leads to macrolide resistance, making subsequent NTM treatment far more difficult. This sequencing question ("what should you do before starting azithromycin prophylaxis?") is a favorite exam setup.

Finally, when a bronchiectasis patient presents with acute, large-volume hemoptysis, the next best step is not intubation or surgical consultation as the initial move. The answer is bronchial artery embolization, which is both diagnostic and therapeutic for identifying and occluding the hypertrophied bronchial artery causing the bleed. Surgical resection is reserved for failure of embolization.

The core competency being tested in bronchiectasis questions is the ability to (1) recognize the disease through its hallmark presentation of voluminous purulent sputum with recurrent infections, (2) correctly identify HRCT as the confirmatory test, (3) distinguish it from COPD and chronic bronchitis, (4) identify and treat the underlying etiology, and (5) apply the correct pharmacologic nuances (dornase alfa only in CF, macrolide prophylaxis only after ruling out NTM, anti-pseudomonal coverage in advanced disease).

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