Should I obtain a CT (computed tomography) chest in a patient with persistent fevers, cough, and dyspnea, who was discharged last week on doxycycline (doxy) and augmentin (amoxicillin-clavulanate) for pneumonia, and now presents with a CXR (chest X-ray) showing prominent pulmonary interstitium without leukocytosis?

CT Chest is Indicated for Persistent Pneumonia Symptoms with Interstitial Changes on CXR

A CT chest is indicated for this patient with persistent pneumonia symptoms and interstitial changes on chest X-ray despite antibiotic treatment. 1

Rationale for CT Chest in This Case

• The patient has concerning features that warrant further imaging evaluation:

  • Recent treatment for community-acquired pneumonia with doxycycline and augmentin 2
  • Persistent symptoms (fevers, cough, dyspnea) despite appropriate antibiotic therapy 1
  • CXR showing "prominent pulmonary interstitium" without leukocytosis 1

• Chest CT is appropriate when initial treatment for pneumonia fails and patients return with persistent symptoms, as it can identify underlying conditions not visible on chest X-ray 1

Clinical Significance of Interstitial Changes on CXR

• Interstitial patterns on chest X-ray have limited sensitivity and specificity, with chest radiography having a relatively low negative predictive value of 64% for relevant findings 1

• Common CT findings in patients with normal chest radiographs but persistent respiratory symptoms include:

  • Bronchiectasis (28%) 1
  • Bronchial wall thickening (21%) 1
  • Interstitial abnormalities 1
  • Mediastinal lymphadenopathy 1

• Up to 34% of chest radiographs may be reported as unremarkable in patients with CT-proven bronchiectasis 1

Diagnostic Value of CT in This Clinical Scenario

• CT chest can identify several important conditions that may explain the patient's persistent symptoms:

  • Treatment-resistant or complicated pneumonia 1
  • Interstitial lung disease that may be triggered or exacerbated by infection 1
  • Bronchiectasis that may be contributing to persistent symptoms 1
  • Pulmonary embolism (if CT angiography is performed) 1

• A recent study showed that ultra-low-dose CT changed the diagnosis in 41% of patients with suspected pneumonia compared to chest X-ray, leading to therapy changes in 37% 3

Recommended Approach

1. Obtain a non-contrast CT chest to evaluate the interstitial changes and assess for underlying lung pathology 1

2. Consider CT angiography if there is clinical suspicion for pulmonary embolism as a complication 1

3. The absence of leukocytosis does not rule out active infection but raises suspicion for non-infectious causes of interstitial changes that CT can better characterize 1

Common Pitfalls to Avoid

• Relying solely on chest X-ray findings when symptoms persist, as radiography has limited sensitivity for many pulmonary conditions 1

• Assuming that absence of leukocytosis rules out active infection; some pneumonias, particularly atypical or viral, may not present with elevated white blood cell count 4

• Failing to consider non-infectious causes of interstitial changes and persistent symptoms after antibiotic treatment 1

• Delaying appropriate imaging in patients with persistent symptoms after treatment for pneumonia 4