Bronchiectasis:

1
Bronchiectasis
A Review of the Types, Causes, and Imaging
Features

• Amy R. Mehollin-Ray, M.D.
• Emma C. Ferguson, M.D.
• Sandra A. A. Oldham, M.D., F.A.C.R.

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Bronchiectasis

• Bronchiectasis is characterized by irreversible
  dilatation of bronchi.
• Multiple underlying conditions may result in
  bronchiectasis, including infection, congenital
  abnormalities of the airways, and pulmonary
  fibrosis.
• Although not specific, the location and
  distribution of bronchiectasis can help narrow
  the differential diagnosis.
• Additional features such as mucus plugging,
  air-fluid levels, and fibrosis can provide
  information about disease activity and possible
  etiologies.

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Radiographic and Bronchographic Findings

• Radiographic Findings
• Bronchial wall thickening
• Cysts, occasionally with air-fluid levels
• Volume loss
• Branching, tubular opacities (mucus plugs)

• Bronchographic Findings
• Bronchial dilatation
• Lack of normal tapering
• Filling defects (mucus plugs)
• Although once considered the gold standard,
  bronchography has now been replaced by
  high-resolution CT (HRCT).

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CT Findings

• Bronchial dilatation
• Defined as internal diameter of bronchus greater
  than diameter of accompanying pulmonary artery.
• Some patients can have mildly dilated bronchi
  without having other imaging findings of
  bronchiectasis (i.e. bronchial wall thickening,
  lack of normal tapering), such as asthmatics and
  patients living at high altitudes.
• Bronchial dilatation should not be used alone to
  define bronchiectasis unless the dilatation is
  severe.

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CT Findings

• Lack of Bronchial Tapering
• Defined as constant bronchial diameter at least 2
  cm distal to a branch point.
• Difficult to assess with vertically and obliquely
  oriented bronchi.
• Often cannot be assessed on HRCT, due to
  noncontiguous slices.

• Abnormally Dilated Peripheral Airways
• Dilated bronchi with thickened walls become more
  visible in the lung periphery in patients with
  bronchiectasis.
• Normal bronchi should not be seen within 1 cm of
  the costal pleural surface.

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CT Findings

• Bronchial Wall Thickening
• Subjective assessment compare to normal regions
  of lungs or to prior studies.

• Mucoid Impaction
• Mucus-filled bronchi appear as lobular or
  branching structures when imaged in plane, and
  appear nodular when cut perpendicular to the
  plane of the scan.
• IV contrast may help distinguish mucus-filled
  bronchi from pulmonary vessels in problem cases.

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Pitfalls in CT Diagnosis

• Motion Artifacts
• Respiratory motion may blur bronchial walls,
  mimicking the tram track appearance of
  bronchiectasis.
• Reversible Bronchiectasis
• Visualization of air bronchograms within areas of
  parenchymal consolidation or atelectasis may
  mimic bronchiectasis. These airways will return
  to normal within resolution of airspace disease
  on follow-up studies.
• Cystic Lung Diseases
• Air cysts in patients with Pneumocystis pneumonia
  can mimic cystic bronchiectasis, but should be
  distinguishable on the basis of other signs (no
  accompanying artery, not arranged in linear
  arrays).
• Bizarre cysts in Langerhans cell histiocytosis
  may have a branching appearance.

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Types of Bronchiectasis

• Cylindrical Bronchiectasis
• smooth dilatation of the bronchi without tapering
• Varicose Bronchiectasis
• dilated bronchi with sites of constriction
• Cystic Bronchiectasis
• ballooning of bronchi into linear arrays of cysts
• Traction Bronchiectasis
• irregular bronchial dilatation due to traction by
  adjacent fibrosis

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Cylindrical Bronchiectasis

• On plain radiography, dilated bronchi may produce
  a tram track appearance formed by parallel,
  thickened bronchial walls.
• On CT, bronchi in the plane of the image will
  appear tubular, without tapering. Bronchi cut in
  cross-section demonstrate the signet ring sign
  a dilated bronchus accompanied by the smaller
  pulmonary artery.

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Varicose Bronchiectasis

• On CT, varicose bronchiectasis will demonstrate a
  beaded appearance (string of pearls) when seen
  in the plane of the image, but may mimic
  cylindrical bronchiectasis when cut in
  cross-section.

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Cystic Bronchiectasis

• On plain radiographs, clusters of cysts may be
  evident.
• On CT, strings or clusters of cysts with
  discernible walls are typical of cystic
  bronchiectasis, known as the cluster of grapes
  appearance.
• Superinfection will produce air-fluid levels in
  some cysts. Pseudomonas aeruginosa is the most
  common pathogen in bacterial superinfection of
  pre-existing bronchiectasis.

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Traction Bronchiectasis

• Traction bronchiectasis results from
  architectural distortion and fibrosis of the lung
  parenchyma.
• It may be seen in any of the diseases that result
  in end-stage lung disease, such as idiopathic
  pulmonary fibrosis (IPF), collagen vascular
  diseases like systemic sclerosis, and asbestosis.
• Traction bronchiectasis is also commonly seen in
  the upper lobes in patients with prior
  tuberculosis and chronic interstitial lung
  disease related to sarcoidosis.
• Fibrosis, volume loss, and traction
  bronchiectasis can occur in the radiation field
  following external beam radiation therapy.

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Distribution

• The distribution of bronchiectasis may be
  classified as localized or diffuse. Although the
  distribution may not be specific, it can help
  narrow the differential diagnosis to a few
  etiologies.
• Although involving all lobes, diffuse
  bronchiectasis may be more severe in the apices
  or bases.
• For example, cystic fibrosis (CF) causes diffuse
  cylindrical bronchiectasis that is typically more
  severe in the upper lobes.
• Diffuse bronchiectasis may also affect central
  bronchi more than peripheral bronchi, as in
  allergic bronchopulmonary aspergillosis.
• If localized, bronchiectasis may have a lobar
  predilection that can help narrow the
  differential diagnosis.
• Bronchiectasis confined to one lobe is highly
  typical of infection.
• Bronchiectasis involving the middle lobe and/or
  lingula with tree-in-bud opacities is commonly
  seen with atypical mycobacterial infection.
• Localized traction bronchiectasis with sharp
  borders that does not follow an anatomic boundary
  in a patient with a history of cancer should
  raise the possibility of radiation fibrosis with
  traction bronchiectasis.

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Diffuse Bronchiectasis

• Diffuse bronchiectasis is seen in cystic fibrosis
  and other congenital causes of bronchiectasis.
• Viruses, such as adenovirus, RSV, and measles,
  can also lead to diffuse bronchiectasis.
  Bordetella pertussis was a cause of diffuse
  bronchiectasis before routine vaccination.
• Traction bronchiectasis in chronic interstitial
  lung disease will often be diffuse, but may have
  an apical or basal predominance. For example,
  patients with idiopathic pulmonary fibrosis and
  systemic sclerosis will demonstrate a basal
  predominance of fibrosis and honeycombing,
  whereas patients with sarcoidosis with
  demonstrate an apical predominance.

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Localized Bronchiectasis

• Infection is the most common cause of localized
  bronchiectasis. Tuberculosis may result in upper
  lobe bronchiectasis, while atypical mycobacteria
  characteristically cause right middle lobe and/or
  lingular bronchiectasis.
• Chronic aspiration pneumonia may result in
  bronchiectasis in the dependent portions of the
  lungs.

• Bronchial obstruction may cause bronchiectasis
  limited to the lobe(s) distal to the site of
  obstruction. Etiologies include endobronchial
  tumors such as carcinoid, bronchial atresia, and
  inhaled foreign bodies.
• External beam radiation therapy may produce
  radiation fibrosis and traction bronchiectasis in
  a localized distribution that conforms to the
  radiation field.

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Central Bronchiectasis

• Dilatation of the proximal bronchi may be seen in
  allergic bronchopulmonary aspergillosis.
• Obstruction of a main bronchus, due to an
  endobronchial lesion such as a tumor or foreign
  body, or from external compression, may result in
  central bronchiectasis.

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Causes of Bronchiectasis

• Congenital
• Cystic Fibrosis
• Dyskinetic Cilia Syndrome
• Williams-Campbell Syndrome
• Mounier-Kuhn Syndrome
• Alpha1-Antitrypsin Deficiency
• Agammaglobulinemia
• Chronic Interstitial Pneumonia / Traction
  Bronchiectasis
• Idiopathic Pulmonary Fibrosis
• Collagen Vascular Disease
• Asbestosis
• Sarcoidosis
• Radiation Fibrosis

• Infection
• Tuberculosis / other Mycobacteria
• Pneumocystis jiroveci
• Chronic Aspiration
• Viruses (Adenovirus, RSV)
• Bordetella pertussis
• Allergic Bronchopulmonary Aspergillosis
• Bronchial Obstruction
• Foreign body
• Endobronchial tumor
• Extrinsic compression
• Bronchial atresia

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Infection

• Infection is the most common cause of
  bronchiectasis. Many different pathologic
  mechanisms are involved in the formation of
  bronchiectasis
• Inflammation can lead to airway damage and
  bronchiectasis.
• Parenchymal damage may lead to fibrosis and
  traction bronchiectasis.
• Dilated airways are more susceptible to
  colonization with microorganisms.
• Impaired mucociliary clearance can predispose to
  airway colonization and can cause progressive
  airway dilatation, leading to recurrent
  infections.
• Bacterial infections can cause bronchiectasis
  through airway damage, parenchymal fibrosis, and
  airway colonization.
• Recurrent bacterial infections are an important
  source of bronchiectasis in patients with HIV
  infection and in those with deficient humoral
  immunity.
• Viral infections can damage airways and impair
  clearance of bacteria, leading to bacterial
  colonization.

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Tuberculosis

• Chronic post-primary tuberculosis typically
  manifests as fibronodular opacities in the upper
  lobes.
• Calcifications may be seen. Volume loss and hilar
  retraction is usually present.
• The process may be unilateral or bilateral.
• Upper lobe bronchiectasis is a common
  manifestation of chronic tuberculosis.
• Activity can only be determined by cultures, but
  chronic tuberculosis may be considered stable if
  there has been no radiographic change over a
  six-month period.

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Atypical Mycobacterial Infection

• Mycobacterium-avium intracellulare (MAI) is
  associated with many radiographic manifestations.
• A typical pattern of bronchiectasis and
  tree-in-bud nodules in the right middle lobe and
  lingula may be seen in middle-aged females, and
  is referred to as Lady Windermere syndrome.

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HIV-associated Bronchiectasis

• Patients with HIV have an increased incidence of
  lower respiratory bacterial infections.
• Recurrent bacterial infections may lead to
  bronchiectasis, often with a lower lobe
  predominance.

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Pneumocystis jiroveci

• Pneumocystis pneumonia typically demonstrates
  bilateral opacities radiating from the hila.
• On HRCT, ground-glass opacities on a background
  of interlobular septal thickening may be
  identified.
• Bronchiectasis is an occasional finding in
  Pneumocystis pneumonia.
• Patients with HIV may develop bronchiectasis as a
  complication of lymphocytic interstitial
  pneumonia.
• AIDS patients are also more susceptible to fungal
  infections, especially with Aspergillus.

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Chronic Aspiration Pneumonia

• Recurrent or chronic aspiration pneumonia most
  commonly affects the superior segments of the
  lower lobes and posterior segments of the upper
  lobes in patients who are supine. The basal
  segments of the lower lobes are affected in
  patients who are in the upright position.
• The right middle lobe and lingula are very rarely
  affected.
• Chronic inflammation can lead to scarring and
  bronchial wall damage, with eventual
  bronchiectasis.
• Bronchiectasis in a bilateral, dependent
  distribution in a patient at risk for aspiration
  should raise suspicion for chronic aspiration
  pneumonia.

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Swyer-James Syndrome

• Swyer-James syndrome results from acute viral
  bronchiolitis at an early age that prevents
  normal development of the lung.
• Affected lobes demonstrate decreased volume with
  inspiration and air trapping with expiration.
  The affected pulmonary arteries are typically
  small, resulting in a small hilum.
• Bronchiectasis and areas of bronchiolitis may be
  present.
• This patient demonstrates low lung volumes
  involving the right middle and lower lobes with
  inspiration. Areas of cylindrical bronchiectasis
  are present. The pulmonary arteries are very
  small.

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Childhood Pertussis

• Childhood respiratory infections, such as measles
  and pertussis pneumonia, can cause diffuse
  bronchiectasis by damaging the airways and
  impairing bacterial clearance.
• The dilated airways become more susceptible to
  bacterial colonization, and recurrent pulmonary
  infections can result.
• Air-fluid levels within some dilated bronchi
  indicate active infection in this patient with
  severe cystic bronchiectasis from childhood
  pertussis pneumonia.

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Allergic Bronchopulmonary Aspergillosis

• Mucus and Aspergillus hyphae become impacted in
  the central bronchi, causing branching tubular
  opacities (finger in glove appearance).
• When the mucus plugs are expectorated, dilated
  bronchi are revealed.
• Patients with asthma and cystic fibrosis are
  particularly susceptible.

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Bronchiolitis Obliterans

• Bronchiectasis can occur in patients with
  bronchiolitis obliterans, often in the setting of
  chronic rejection after solid organ
  transplantation or bone marrow transplantation
  (BMT).
• This patient with Severe Combined
  Immunodeficiency (SCID) underwent BMT two years
  ago. Since then, he has suffered recurrent
  episodes of graft-versus-host disease. Lung
  biopsy showed areas of bronchiolitis obliterans
  and bronchiectasis.

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Congenital Causes

• Diffuse bronchiectasis may be seen in patients
  with cystic fibrosis. Bronchiectasis is often
  most severe in the upper lobes. Bronchiectasis
  occurs due to tenacious secretions and recurrent
  pulmonary infections.
• In dyskinetic cilia syndrome, abnormal ciliary
  function results in recurrent pulmonary
  infections and bronchiectasis. Bronchiectasis
  may be diffuse or may demonstrate a basal
  predominance.
• Williams-Campbell syndrome is characterized by a
  deficiency in bronchial cartilage, resulting in
  bronchiectasis, abnormal mucus clearance, and
  recurrent pulmonary infections.
• Mounier-Kuhn syndrome is a congenital abnormality
  in the membranous and cartilaginous portions of
  the tracheal and bronchial walls.
  Tracheobronchomegaly is typical, and
  bronchiectasis may be due to the genetic defect
  or recurrent infections.
• In alpha1-antitrypsin deficiency, a genetic
  defect allows proteases to damage the lungs,
  leading to panacinar emphysema. Bronchiectasis is
  often associated.
• Patients with agammaglobulinemia and other forms
  of deficient humoral immunity may develop
  bronchiectasis from recurrent respiratory
  infections.

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Cystic Fibrosis

• Diffuse bronchiectasis, more severe in the upper
  lobes, is characteristic.
• Areas of mucus plugging may be present.
• The lungs are often hyperexpanded.

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Cystic Fibrosis

• Another patient with cystic fibrosis has CT
  findings of bronchiectasis, with multiple dilated
  bronchi, some seen in the plane of the image
  (tram tracks) and others seen in cross-section
  (signet ring sign).
• Multiple areas of mucus plugging are present,
  seen both as apparent solid nodules accompanying
  the pulmonary arteries, and as centrilobular
  nodules (tree-in-bud opacities).

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Dyskinetic Cilia Syndrome

• Bronchiectasis in patients with dyskinetic cilia
  syndrome may be diffuse or may demonstrate a
  lower lobe predominance, as in this patient.
• A subset of dyskinetic cilia syndrome is
  Kartageners syndrome, which is characterized by
  situs inversus, sinusitis, and bronchiectasis.
• Impaired mucociliary clearance results in
  recurrent pulmonary infections.

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Mounier-Kuhn Syndrome

• Marked dilatation of the trachea and main bronchi
  is typically seen, known as tracheobronchomegaly.
  Tracheal diverticula and bronchiectasis may be
  present.
• Recurrent lower respiratory infections are
  common.
• Bilateral pleural effusions and a right-sided
  chest tube in this patient with Mounier-Kuhn
  syndrome were related to a recent motor vehicle
  collision.

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Alpha1-Antitrypsin Deficiency

• Basilar panacinar emphysema is characteristic.
  Bronchiectasis may involve all five lobes of the
  lungs.
• Airway damage is caused by increased protease
  activity, and is hypothesized to be the cause for
  bronchiectasis as well as emphysema in these
  patients.

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Agammaglobulinemia

• Patients with deficient humoral immunity due to
  agammaglobulinemia are most prone to infections
  with encapsulated organisms.
• Recurrent respiratory infections may result in
  bronchiectasis, and are the greatest source of
  morbidity for these patients.

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Chronic Interstitial Pneumonia

• Any chronic interstitial pneumonia which leads to
  end-stage lung disease can produce bronchiectasis
  through architectural distortion and fibrosis,
  resulting in traction bronchiectasis. Findings
  on CT include septal and interstitial thickening,
  bronchiectasis, and honeycombing.
• These disease entities include idiopathic
  pulmonary fibrosis, collagen vascular diseases,
  asbestosis, and drug reactions.
• Sarcoidosis and external beam radiation therapy
  can also produce fibrosis and traction
  bronchiectasis.

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Idiopathic Pulmonary Fibrosis

• Idiopathic pulmonary fibrosis represents the
  end-stage of chronic interstitial pneumonia,
  regardless of etiology.
• Characteristic findings on CT include septal and
  intralobular thickening, honeycombing, and
  traction bronchiectasis. These changes are
  typically peripheral in distribution.
• Ground-glass opacities reflect areas of active
  alveolitis.

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Sarcoidosis

• Around 20 of patients with interstitial lung
  disease will progress to fibrosis, which
  typically consists of upper lobe fibrosis, hilar
  retraction, and traction bronchiectasis.
• Ground-glass opacities may be superimposed on the
  background of interstitial lung disease. As
  opposed to usual interstitial pneumonia, where
  ground-glass opacities represent alveolitis, in
  sarcoidosis these opacities are due to extensive
  interstitial sarcoid granulomata.

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Systemic Sclerosis

• Interstitial fibrosis with linear opacities
  occurs with a basilar predominance.
• Bronchiectasis may also be found in chronic
  aspiration due to esophageal dysmotility.

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Radiation Fibrosis

• Radiation fibrosis may develop 6-12 months after
  external beam radiation therapy.
• Fibrosis, consolidation, and traction
  bronchiectasis conform to the shape of the
  radiation port.
• The adjacent lung may be hyperexpanded.
• This patient underwent radiation therapy for lung
  cancer. Traction bronchiectasis and fibrosis are
  present in the previous radiation field.

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Conclusion

• The distribution and pattern of bronchiectasis
  can be helpful in forming a differential
  diagnosis.
• Traction bronchiectasis in the lower lobes with
  honeycombing
• IPF, collagen vascular diseases, asbestosis.
• Traction bronchiectasis in both upper lobes with
  hilar retraction
• post-primary tuberculosis, sarcoidosis, radiation
  fibrosis.
• Diffuse bronchiectasis
• CF, childhood pneumonias.
• Bronchiectasis in the dependent portions of the
  lungs, with mucus plugs or air-fluid levels
• chronic aspiration.
• Right middle lobe/lingular bronchiectasis with
  tree-in-bud opacities
• atypical mycobacterial infection.
• Lobar distribution of bronchiectasis
• post-infectious, including bacterial,
  tuberculous, and fungal.
• Traction bronchiectasis and fibrosis not
  conforming to a lobar distribution
• radiation fibrosis.