Cystic Fibrosis

Gerald F. Abbott, MD

Key Facts

Terminology

Cystic fibrosis (CF): Hereditary disorder that affects gene regulating chloride transport
Accounts for up to 25% of adult cases of bronchiectasis

Imaging Findings

Diffuse bronchiectasis with predominant involvement of upper lobes
- Right upper lobe often 1st and most severely affected
Airways primary site of pathology in CF
- Bronchial wall thickening earliest finding
- Bronchiectasis most common finding; diffuse involvement, usually predominant in both upper lobes
Hyperinflation early finding; may be reversible initially, then permanent (100%)
CT more sensitive to deterioration in clinical status than pulmonary function tests
Role of CT tempered by large life-time radiation dose

Top Differential Diagnoses

Allergic Bronchopulmonary Aspergillosis
Immotile Cilia Syndrome
Tuberculosis

Clinical Issues

Patients with mild disease may be asymptomatic and not diagnosed until adulthood

Diagnostic Checklist

CF in any adult with unexplained bronchiectasis

Axial NECT shows cylindrical bronchiectasis

, centrilobular nodules, and tree-in-bud opacities that predominantly involve both upper lobes.

Axial NECT shows a small subpleural consolidation

, mild cylindrical bronchiectasis

, and small centrilobular nodules

in this patient with cystic fibrosis.

TERMINOLOGY

Abbreviations and Synonyms

Cystic fibrosis (CF), mucoviscidosis

Definitions

Hereditary disorder that affects gene regulating chloride transport
- Production of abnormal secretions from exocrine glands (salivary and sweat glands, pancreas, large bowel, tracheobronchial tree)
- Thick viscous secretions affecting multiple organs, primarily lungs and pancreas
Accounts for up to 25% of adult cases of bronchiectasis

IMAGING FINDINGS

General Features

Best diagnostic clue: Diffuse bronchiectasis with predominant involvement of upper lobes
Patient position/location
- Predominant abnormalities in upper lobes
  - Right upper lobe often 1st and most severely affected

CT Findings

Airways
- Primary site of pathology in CF
- Bronchial wall thickening earliest finding
  - Due to inflammation or infection of airway wall; precedes development of bronchiectasis
- Bronchiectasis most common finding; diffuse involvement, usually predominant in both upper lobes
- Mucous plugging manifests as centrilobular nodular, tubular, and V- or Y-shaped (tree-in-bud) opacities
Lung
- Air-trapping
  - Hyperinflation is early finding; may be reversible initially, then permanent (100%)
  - Mosaic lung attenuation
- Recurrent areas of consolidation
  - May represent superimposed pneumonia or atelectasis and retained secretions distal to bronchial obstruction
- Cystic or bullous changes may occur, typically subpleural in upper lobes (predisposes to pneumothorax) in end-stage disease
Cardiac
- Acute increase in heart size (cor pulmonale; ominous clinical sign)
- Pulmonary arterial hypertension in end-stage disease
Associated findings
- Mild lymphadenopathy (reactive) common
- Pleural effusions uncommon
Evolution
- Early
  - Mild bronchial wall thickening
  - Regional (lobular) air-trapping
  - Centrilobular nodules (from mucus plugging in peripheral airways)
- Moderate progression
  - Increased bronchial wall thickening
  - Development of cylindrical bronchiectasis
  - Increased air-trapping (segmental to lobar)
- End-stage
  - Progression to varicose or saccular bronchiectasis
  - More proximal mucus plugging
  - Chronic lobar collapse
Correlation with pulmonary function
- Dissociation between progressive structural damage evidenced by CT and stable or improved pulmonary function tests in many patients
  - CT more sensitive to deterioration in clinical status than pulmonary function tests
- Scoring systems: Bhalla and others
  - Shown to have good interobserver agreement
  - No consensus yet as to which is most appropriate for evaluating new therapies or monitoring disease

Radiographic Findings

Radiography
- Less sensitive for earliest changes in CF
- Primary role is longitudinal assessment

Angiographic Findings

Bronchial artery embolization for hemoptysis

Imaging Recommendations

Best imaging tool
- Chest radiography every 2-4 years recommended by Cystic Fibrosis Foundation
  - Annually for those with frequent infections or declining lung function
- CT role currently being defined
  - Now being used as outcome measure for therapeutic trials
Protocol advice
- Role of CT tempered by large life-time radiation dose
  - 1st CT often in childhood
  - Chest CT average dose of 6 mSv
- Radiation dose reduction important
  - Incremental CT vs. volumetric scans (reduces dose 8x)
  - Lower mAs to 20 (reduces dose 10x from typical mAs of 200)

DIFFERENTIAL DIAGNOSIS

Allergic Bronchopulmonary Aspergillosis

Central upper lobe predominant bronchiectasis
History of asthma, often eosinophilia
10% of patients with CF have allergic bronchopulmonary aspergillosis (ABPA)

Immotile Cilia Syndrome

Not upper lobe predominant
Dextrocardia or situs inversus; sinusitis also common

Postinfectious Bronchiectasis

Usually unilateral, lobar, or sublobar; often lower lobe (except for tuberculosis)

Williams-Campbell Syndrome

Rare; congenital deficiency of cartilage in subsegmental bronchi
Bronchiectasis limited to 4th-6th generation bronchi

Tuberculosis

Reactivation can produce upper lobe volume loss; bronchiectasis in 50%
Often associated with calcifications in pulmonary granulomas and hilar mediastinal lymph nodes

Ankylosing Spondylitis