When is a chest x-ray recommended for a patient with acute bronchitis and how is it interpreted?

Chest X-ray in Acute Bronchitis: Indications and Interpretation

Chest X-rays are not routinely indicated for patients with uncomplicated acute bronchitis and should only be performed when pneumonia is suspected based on specific clinical findings or in cases of persistent cough lasting more than 3 weeks. 1

When to Order a Chest X-ray

• Chest X-rays should be considered when one or more of the following signs and symptoms are present:

  • New focal chest signs on examination
  • Dyspnea
  • Tachypnea
  • Pulse rate >100 beats/min
  • Fever persisting >4 days 1, 2

• Additional indications for chest X-ray include:

  • Age ≥60 years (especially with comorbidities)
  • Abnormal vital signs (heart rate ≥100 beats/min, respiratory rate ≥24 breaths/min, oral temperature ≥38°C)
  • Focal consolidation on chest examination (rales, egophony, or fremitus)
  • Hemoptysis
  • Cough persisting >3 weeks 1

• Patients with C-reactive protein (CRP) >100 mg/L should undergo chest X-ray as this level makes pneumonia likely 1, 2

When to Avoid Chest X-ray

• Chest X-rays are unnecessary in patients with:

  • Normal vital signs
  • Normal pulmonary auscultation
  • CRP <20 mg/L with symptoms present for >24 hours 1

• In healthy, non-elderly adults (<40 years), pneumonia is uncommon (only 4%) in the absence of vital sign abnormalities or asymmetrical lung sounds 1

Interpretation of Chest X-ray Findings

• Normal chest X-ray in a patient with acute cough supports the diagnosis of acute bronchitis 3, 4

• Chest X-ray findings that suggest pneumonia rather than bronchitis include:

  • Focal consolidation
  • Pleural effusion
  • Interstitial infiltrates 5

• Radiological signs in acute bronchitis may include:

  • Peribronchial cuffing
  • Increased bronchovascular markings
  • Enlarged hilar regions 6, 5

Special Considerations

• Lower threshold for chest X-ray is warranted in elderly patients (≥60 years) even with normal vital signs and physical examination findings due to:

  • Higher incidence of pneumonia
  • Increased risk of mortality
  • Less typical presentation of symptoms 1

• Patients with underlying comorbidities (COPD, heart failure, immunosuppression) require individualized assessment that may include earlier use of chest X-ray 1

• In patients with suspected aspiration, chest X-ray should be performed to evaluate for aspiration pneumonia 1

Alternative Imaging Modalities

• CT scan is not indicated for initial imaging of immunocompetent patients with suspected acute bronchitis and low pretest probability of pneumonia 1

• Ultrasound has shown higher sensitivity than chest X-ray in detecting small consolidations and interstitial infiltrations in some respiratory infections, but is not currently recommended in guidelines for routine diagnosis of acute bronchitis 6

Clinical Implications

• The primary purpose of chest X-ray in patients with acute cough is to rule out pneumonia, which requires antibiotic treatment, unlike acute bronchitis 1, 3

• Acute bronchitis is typically viral in origin (≥90% of cases) and antibiotics provide minimal benefit (reducing cough by only about half a day) while exposing patients to adverse effects 3, 4

• Patient education about the expected duration of cough in acute bronchitis (typically 2-3 weeks) is essential and more important than radiographic evaluation in uncomplicated cases 4, 7