Can you interpret a chest radiograph?

Can I Interpret a Chest Radiograph?

Yes, as a medical provider you can and should learn to systematically interpret chest radiographs, following established guidelines from the American College of Radiology that outline a structured approach to avoid missing clinically significant findings. 1, 2

Why Chest Radiograph Interpretation Matters

Chest radiography remains the most commonly performed radiographic examination, accounting for up to 26% of all radiographic tests. 3 However, it is a complex imaging modality with documented interpretation discrepancies even among experienced clinicians. 3 The ability to systematically read chest X-rays is essential because these studies can identify life-threatening conditions including pneumothorax, pneumonia, pulmonary edema, aortic dissection, and cardiac tamponade. 4

Systematic Interpretation Framework

Step 1: Technical Quality Assessment

• Verify patient identification, examination date, and assess image quality including proper penetration, rotation, and inspiration. 1
• Check for rotation by evaluating the relationship between the medial clavicular heads and spinous processes—rotation can mimic or obscure true pathology such as pneumothorax, pleural effusions, or mediastinal masses. 1
• Recognize that portable AP radiographs have significantly lower sensitivity (missing approximately 40-50% of pneumothoraces, pulmonary contusions, and rib fractures compared to PA/lateral views or CT). 1, 2

Step 2: Airway and Mediastinum

• Trace the trachea and main bronchi, noting any deviation or narrowing. 1
• Assess mediastinal width and contour—widening may suggest aortic pathology (dissection, aneurysm) or lymphadenopathy. 1, 2
• Evaluate the aortopulmonary window and hilar regions for abnormal masses or lymphadenopathy. 1
• In suspected pulmonary hypertension, measure the main pulmonary artery (>35 mm from midline to left lateral border) and right descending pulmonary artery (>15 mm in women, >16 mm in men), which have 93% sensitivity and 88% specificity. 2

Step 3: Cardiac Silhouette

• Assess cardiac size using the cardiothoracic ratio—a ratio >0.5 on a PA film indicates cardiomegaly. 2
• In acute coronary syndrome evaluation, chest radiography can identify acute pulmonary edema without cardiac enlargement in patients with acute MI and no prior ischemic damage. 4
• Look for abnormal cardiac contours that might suggest pericardial effusion or chamber enlargement. 2

Step 4: Lung Parenchyma

• Systematically examine all lung zones (upper, middle, lower) bilaterally for opacities, nodules, or masses using side-to-side comparison. 1, 2
• Evaluate for consolidation (focal opacities suggesting pneumonia, which has 69-75% sensitivity on chest radiography). 2
• Assess for interstitial patterns (reticular, nodular, or reticulonodular) that may indicate interstitial lung disease, though HRCT is more sensitive for early changes. 4
• Note that chest radiography has limited sensitivity—a normal chest X-ray does not exclude significant pathology, particularly early pneumonia or interstitial disease. 2

Step 5: Pleura

• Trace pleural surfaces looking for pneumothorax (visible pleural line with absence of lung markings peripherally). 2
• Assess for pleural effusion by identifying the meniscus sign and blunting of costophrenic angles. 2
• Evaluate for pleural thickening or plaques, which may indicate asbestos exposure or malignancy (asymmetric nodular pleural thickening with unilateral effusion suggests mesothelioma). 4, 2

Step 6: Diaphragm

• Assess diaphragmatic contours for flattening (suggesting hyperinflation/COPD), elevation, or depression. 1, 2
• Look for free air under the diaphragm indicating pneumoperitoneum. 2

Step 7: Bones and Soft Tissues

• Examine ribs, clavicles, scapulae, spine, and shoulders for fractures, lytic or blastic lesions. 1, 2
• Assess soft tissues for subcutaneous emphysema (lucent streaks), masses, or abnormal calcifications. 1, 2
• Verify positioning of any surgical hardware, monitoring devices, tubes, or lines. 1

Clinical Integration and Next Steps

Always correlate radiographic findings with clinical information (history, physical exam, laboratory data) to narrow differential diagnoses. 1, 2 The chest radiograph serves multiple roles:

• In acute coronary syndrome, it rules out conditions masquerading as myocardial ischemia (pneumothorax, pneumonia, aortic dissection) and identifies complications like pulmonary edema. 4
• In trauma, pay special attention to widened mediastinum, rib fractures, and pneumothorax/hemothorax, though recognize that chest radiography misses approximately 80% of hemothorax and 50% of vertebral/rib fractures compared to CT. 2
• In suspected pulmonary embolism, look for Westermark sign and Hampton's hump, though a normal chest X-ray actually increases suspicion for PE in patients with acute dyspnea and hypoxemia. 2

When to Advance to CT Imaging

Order chest CT when radiographic findings are abnormal or equivocal and require further characterization. 1, 2 Specific scenarios include:

• Suspected aortic dissection or pulmonary embolism (chest radiography has far lower sensitivity than CT for these life-threatening conditions). 4
• Equivocal findings on chest radiograph with high clinical suspicion. 4
• Diminished pulmonary function with normal chest radiograph findings. 4
• Trauma patients where approximately 40% with "normal" chest radiographs have injuries detected on CT. 1

Critical Pitfalls to Avoid

• Perceptual errors are a leading source of missed findings and malpractice litigation—use a consistent systematic approach every time. 2
• Never rely solely on portable AP films for excluding pneumothorax or hemothorax—sensitivity is significantly reduced. 1, 2
• Do not assume a normal chest radiograph excludes disease—if clinical suspicion remains high, pursue further imaging. 2
• Recognize that HRCT is more sensitive than chest radiography for detecting early asbestosis, with 34% of patients with normal chest radiographs (ILO 0/0 or 0/1) showing findings on HRCT. 4