What are the typical HRCT (High-Resolution Computed Tomography) chest findings in a patient with bronchitis?

HRCT Chest Findings in Bronchitis

The most characteristic HRCT findings in bronchitis are bronchial wall thickening (present in 57-62% of cases) and air trapping (31-35%), with additional features including centrilobular nodules, tree-in-bud pattern, and mosaic attenuation on expiratory imaging. 1

Direct Airway Abnormalities

Bronchial wall thickening is the most common and significant finding, appearing in the majority of bronchitis patients on HRCT. 1 This finding:

• Represents inflammation and edema of the airway walls 2
• Can be quantitatively measured and shows significant association with cough symptoms in patients with chronic airway disease 1
• May appear as diffuse thickening along visible airways 1
• Is neither highly sensitive nor specific for bronchitis alone, as it can be seen in multiple airway diseases 2

Small airway abnormalities manifest as: 1

• Centrilobular nodules (2-4 mm nodular branching patterns)
• Tree-in-bud pattern (linear branching opacities representing mucus-filled dilated bronchioles)
• These direct signs indicate inflammation or dilation of small airways

Indirect Signs of Small Airways Disease

Air trapping is a critical indirect finding that appears as: 1

• Mosaic attenuation pattern on expiratory CT scans
• Present in 31-35% of bronchitis cases
• Indicates functional small airway obstruction even when airways appear structurally normal

Additional indirect features include: 1

• Subsegmental atelectasis
• Ground-glass opacities (particularly in patients with concurrent chronic rhinosinusitis) 1
• Bronchiolectasis (dilation of small airways)

Important Technical Considerations

Expiratory imaging is essential because: 1

• Many bronchiolar abnormalities are only visible on expiratory cuts
• Air trapping and mosaic attenuation require expiratory phase imaging for detection
• Standard inspiratory imaging alone may miss significant small airways disease

HRCT limitations include: 1

• Cannot visualize normal bronchioles (resolution limited to airways >2 mm diameter)
• Clinically significant disease may exist despite normal HRCT findings
• Chest radiographs are often normal in bronchiolar disease despite significant pathology

Clinical Context and Diagnostic Yield

HRCT findings correlate with clinical severity: 1

• Bronchial wall thickening shows quantitative association with cough symptoms
• Centrilobular nodules, atelectasis, and ground-glass opacities are more prevalent in patients with concurrent chronic rhinosinusitis

Common pitfall: HRCT may be normal or noncontributory in many symptomatic patients. 1 In one military cohort with respiratory complaints, HRCT was noncontributory or normal in 48 of 49 patients, suggesting HRCT should be reserved for specific indications rather than routine screening. 1

When HRCT is Indicated

Reserve HRCT for: 3, 4

• Patients failing empiric treatment after appropriate therapeutic trials
• Symptoms persisting beyond 8 weeks (chronic cough)
• Indeterminate chest radiograph findings
• Clinical suspicion of structural abnormalities like bronchiectasis

HRCT can detect: 3, 4

• Bronchiectasis in 27% of patients with chronic cough and normal chest radiographs
• Bronchial wall thickening in 21% of such patients
• These findings are missed by standard chest radiography in up to 34% of cases