What imaging tests are recommended for a patient with chronic cough?

Imaging Recommendations for Patients with Chronic Cough

Chest radiography should be the initial imaging test for all patients with chronic cough lasting more than 8 weeks, followed by CT chest for persistent symptoms or concerning features. 1

Initial Imaging Approach

First-Line Imaging: Chest Radiography

• Chest radiography is recommended by both the American College of Radiology (ACR) and American College of Chest Physicians (ACCP) as the first imaging study for chronic cough evaluation 1, 2
• Purpose: To exclude treatable and serious underlying pulmonary pathology such as:
  • Bronchiectasis
  • Interstitial lung disease
  • Neoplasms
  • Infectious processes

Findings on Chest Radiography

• May show bronchial wall thickening, peribronchial cuffing, and hyperinflation 2
• Can be normal in up to 34% of patients with significant bronchial disease 2
• Abnormal radiography is positively associated with underlying primary pulmonary pathology other than asthma (odds ratio 7.7) 1

When to Proceed to Advanced Imaging

Indications for CT Chest

CT chest (with or without IV contrast) is indicated in the following scenarios:

1. Persistent symptoms despite initial clinical evaluation and empiric treatment 1, 2
2. Abnormal findings on chest radiograph requiring further characterization 1
3. Presence of red flag symptoms:
   • Hemoptysis
   • Unintentional weight loss
   • Fever or night sweats
   • Recurrent pneumonia 2, 3
4. Increased risk for lung cancer:
   • Smoking history
   • Occupational exposures (asbestos, silica)
   • Family history of lung cancer 1, 2

CT Protocol Considerations

• Non-contrast CT is generally sufficient for evaluation of chronic cough 2
• High-Resolution CT (HRCT) is the reference standard for detecting bronchial abnormalities with sensitivity and specificity exceeding 90% 2
• HRCT is particularly valuable for detecting:
  • Bronchiectasis (bronchial-arterial ratio >1, "signet ring sign")
  • Bronchial wall thickening
  • Mosaic attenuation on expiratory imaging
  • Peribronchial inflammation 2

Limitations of Chest Radiography

The negative predictive value of chest radiography in diagnosing pulmonary causes of chronic cough is relatively low at approximately 64% 4. In a study of patients with chronic cough and normal chest radiographs:

• 36% had abnormalities on CT that were relevant to chronic cough 4
• Most common missed findings included:
  • Bronchiectasis (11.9%)
  • Bronchial wall thickening (10.2%)
  • Mediastinal lymphadenopathy (8.5%) 4

Clinical Decision Algorithm

1. Initial presentation of chronic cough (>8 weeks):

   • Perform chest radiography for all patients 1, 2

2. If chest radiography is normal:

   • Proceed with empiric treatment for common causes (upper airway cough syndrome, asthma, GERD) 1, 5
   • Monitor response to treatment

3. Proceed to CT chest if:

   • Symptoms persist despite optimal treatment
   • Red flag symptoms are present
   • Patient has risk factors for lung cancer
   • Abnormal findings on chest radiography 1, 2, 3

4. Consider bronchoscopy if:

   • CT findings suggest malignancy or infection
   • Patient is a smoker with persistent cough, especially with hemoptysis 2

Special Considerations

• In patients with suspected occupational exposures, CT may detect abnormalities not visible on chest radiography 1
• Low-dose CT techniques may be considered to reduce radiation exposure while maintaining diagnostic accuracy for most pulmonary abnormalities 1
• Patients with unintentional weight loss, fevers, and productive cough with CT findings of tree-in-bud nodularity should be evaluated for tuberculosis and other infectious etiologies 2

By following this evidence-based approach to imaging in chronic cough, clinicians can efficiently diagnose underlying pulmonary pathology while minimizing unnecessary radiation exposure and invasive procedures.