RespiratoryTier 2Topic

Imaging - chest X-ray (CXR)

Role

First-line respiratory imaging - PA erect is the standard view; AP portable films are used in unwell/immobile patients but are less reliable for heart size and apical assessment
Cheap, fast, and the ubiquitous first test for nearly every respiratory presentation

Findings and causes

Finding	Cause
Consolidation	Pneumonia
Cavitation	TB, abscess, cancer
Reticular/nodular pattern	Interstitial lung disease
Hyperinflation, flattened diaphragms	COPD
Elevated hemidiaphragm	Phrenic nerve palsy, subpulmonic effusion
Widened mediastinum	Aortic pathology, lymphadenopathy

Reading the film

Systematic review approach (airway, breathing/lung fields, cardiac, diaphragm, everything else/soft tissue and bone)
AP films magnify heart size - do not use for cardiomegaly assessment
Supine films miss small pneumothorax/effusion - a lateral decubitus view is more sensitive when suspicion is high

Next steps

Guides next-step imaging (CT) when findings are equivocal or malignancy is suspected

Indications

Pneumonia, interstitial lung disease, COPD, lung cancer, pneumothorax

Follow-up films

Serial CXR tracks pneumonia resolution, which can lag clinical improvement by weeks
Repeat CXR at ~6 weeks post-pneumonia in smokers/older adults to exclude an underlying obstructing malignancy

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