What is the proper method for interpreting a chest x-ray (CXR) result?

Systematic Approach to Chest X-Ray Interpretation

Chest x-ray interpretation should follow a structured, systematic approach that evaluates technical quality first, then proceeds through anatomical regions in a consistent sequence to minimize missed findings and ensure comprehensive assessment. 1

Technical Quality Assessment

Before interpreting any chest radiograph, verify technical adequacy:

• Confirm adequate inspiratory effort by counting posterior ribs (should visualize 8-10 posterior ribs or 5-6 anterior ribs above the diaphragm) 1
• Assess rotation by checking that the medial ends of the clavicles are equidistant from the spinous processes 1
• Evaluate penetration by ensuring vertebral bodies are just visible through the cardiac silhouette 1
• Check for motion artifact and overlying materials that may obscure findings 1

Poor technical quality significantly reduces diagnostic accuracy—portable AP chest radiographs have reduced sensitivity compared to standard PA views, with studies showing 40% of patients with "normal" portable chest radiographs actually had injuries on CT. 1

Systematic Review Pattern

Use a consistent anatomical checklist approach to avoid missing findings, as within- and between-observer variability in chest radiograph interpretation is substantial even among expert clinicians. 1, 2

Airways and Mediastinum

• Trachea: Assess position (midline vs. deviated), caliber, and presence of endotracheal tube if present 3
• Mediastinal contours: Evaluate for widening, masses, or abnormal contours 1
• Hilar structures: Compare size and density bilaterally; asymmetry may indicate adenopathy or mass 1

Cardiac Silhouette

• Cardiothoracic ratio: Should be <0.5 on PA view (less reliable on AP portable films) 1, 4
• Cardiac borders: Loss of normal borders suggests adjacent lung pathology (silhouette sign) 5
• Right atrial enlargement: Identified by increased convexity of right heart border 4

Lungs and Pleura

• Lung parenchyma: Systematically compare upper, middle, and lower zones bilaterally for:
  • Consolidation (air-space opacification) 1
  • Interstitial disease (reticular or nodular patterns) 1, 6
  • Masses or nodules 1
  • Pneumothorax (look for visceral pleural line, especially at apices) 1
• Pleural spaces: Assess for effusions (blunting of costophrenic angles) or thickening 1

Bones and Soft Tissues

• Ribs: Trace each rib systematically for fractures (often missed on initial review) 1
• Clavicles and scapulae: Evaluate for fractures or destructive lesions 1
• Soft tissues: Check for subcutaneous emphysema, masses, or asymmetry 1
• Diaphragm: Assess position, contour, and presence of free air underneath 1

Medical Devices

When devices are present, specifically verify:

• Endotracheal tubes: Tip should be 3-5 cm above carina 3
• Central venous catheters: Tip should be in superior vena cava or cavoatrial junction 3
• Chest tubes: Position relative to pneumothorax or effusion 3
• Pacemakers/ICDs: Lead positions and integrity 3

Critical Pitfalls to Avoid

Senior radiologists achieve significantly higher diagnostic accuracy than non-specialists (p=0.002), highlighting the importance of expert review for definitive interpretation. 2

• Portable AP radiographs have lower sensitivity for pneumothorax (50% missed), hemothorax (75% missed), pulmonary contusions (50% missed), rib fractures (50% missed), and aortic injury (100% missed) compared to CT. 1
• Normal chest radiograph does not exclude significant pathology—40% of patients with "normal" portable chest radiographs had injuries detected on subsequent CT. 1
• Overlying structures and patient positioning significantly degrade image quality on portable films. 1, 6
• High-frequency, low-contrast abnormalities (interstitial disease, small pneumothoraces) are particularly difficult to detect and require careful systematic review. 6

When to Escalate for Expert Review

All chest radiographs should be reviewed by a senior clinician early during hospital admission and reported by a radiologist at the earliest opportunity. 2

Immediate radiologist consultation is warranted for:

• Suspected life-threatening findings: Tension pneumothorax, massive hemothorax, mediastinal widening suggesting aortic injury 1
• Equivocal or subtle findings in high-risk patients (trauma, immunocompromised, suspected malignancy) 1
• Device malposition requiring urgent intervention 3

Limitations of Chest Radiography

Chest CT with IV contrast is far more sensitive than chest radiography for detecting pulmonary metastases (sensitivity of chest x-ray as low as 28%), pulmonary nodules, mediastinal adenopathy, and thoracic injuries. 1

For specific clinical scenarios requiring higher sensitivity:

• Suspected pulmonary hypertension: Chest radiograph is appropriate for initial screening but transthoracic echocardiography is the definitive screening test 1, 4
• Suspected interstitial lung disease: Normal chest radiograph does not exclude clinically important ILD; CT without IV contrast is superior 1
• Blunt trauma with hemodynamic stability: CT chest with IV contrast is indicated rather than relying on chest radiograph alone 1
• Lung cancer surveillance: CT chest (with or without IV contrast) is the standard, not chest radiography 1