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

How to Read a Chest X-Ray: A Systematic Approach

Use a standardized, systematic approach every single time you interpret a chest x-ray, examining the same anatomical structures in the same order to avoid missing critical findings. 1, 2

Essential Pre-Reading Considerations

Before interpreting the radiograph itself, assess these technical factors:

• Verify adequate lung inflation – Films taken at less than total lung capacity can mimic lung disorders and lead to false-positive interpretations 3
• Check patient positioning – Rotation or improper positioning alters the appearance of mediastinal and cardiac structures 1
• Note if portable vs. standard technique – Portable radiographs have inherent technical limitations that affect image quality 3
• Always compare with prior films when available – This is mandatory to confirm findings and extend your differential diagnosis 2

The Systematic Review Sequence

Follow this exact order for every chest x-ray interpretation:

1. Soft Tissues and Chest Wall

• Examine subcutaneous tissues for air, masses, or asymmetry 1
• Look for surgical clips, pacemakers, or other foreign bodies 2

2. Bones

• Systematically review each rib, clavicle, scapula, and visible spine 1
• Check for fractures, lytic or blastic lesions, and degenerative changes 2

3. Pleura

• Trace the pleural surfaces bilaterally looking for thickening, calcification, or effusions 1
• Ultrasound is the preferred initial imaging modality for identifying and characterizing pleural effusions 4
• Absence of contralateral mediastinal shift with a large effusion suggests trapped lung or fixed mediastinum 4

4. Mediastinum

• Assess mediastinal contours and width 1
• Identify tracheal position and any deviation 2
• Examine the aortic knob and descending aorta 1

5. Heart and Cardiac Silhouette

• Evaluate cardiac size and contour 1
• Check for chamber enlargement patterns 2

6. Pulmonary Vasculature and Hila

• Compare hilar size, density, and symmetry 1
• Assess pulmonary vascular markings for redistribution or prominence 2

7. Lung Parenchyma

• Systematically scan each lung zone: upper, middle, and lower on both sides 2
• Compare symmetry between left and right lungs 1
• Look for nodules, masses, infiltrates, or areas of consolidation 2
• For lung nodules, thin-section CT (≤1.5 mm slices) with multiplanar reconstructions is required for accurate characterization 5

8. Review Hidden Areas

• Examine the lateral chest x-ray, which reveals 15% of lung tissue hidden on the PA view 2
• Check lung apices, behind the heart, and behind the diaphragm 2
• Review the costophrenic angles bilaterally 1

Critical Pitfalls to Avoid

• Never read the radiologist's report first – Interpret the film yourself, then discuss findings with radiology colleagues 2
• Do not rely on chest x-ray alone for detecting pulmonary metastases – Sensitivity is only 28% compared to chest CT, and CXR-detectable metastases indicate late-stage disease 6
• Avoid using chest radiography for follow-up of nodules <1 cm – Most are not visible on plain films 5
• Do not attempt pleurodesis in malignant effusions without first demonstrating complete lung expansion 4

When Additional Imaging Is Required

• For pulmonary nodule characterization or follow-up, use CT chest without IV contrast – Contrast adds no value for detecting nodules, assessing growth, or characterizing morphology 5
• CT scanning can differentiate pleural effusion from lung abscess and identify endobronchial obstruction 4
• Chest fluoroscopy and CT offer further clarification when plain films are equivocal 3

Building Competence

• Read hundreds of normal chest x-rays to develop confidence in identifying abnormalities – Clinicians can only reliably distinguish normal from abnormal through extensive exposure 2
• Senior clinicians (consultants and registrars) achieve significantly higher accuracy than junior doctors (p=0.001), and radiologists outperform other specialists (p=0.002) 7
• All chest x-rays should be reviewed by a senior clinician early in hospital admission and reported by a radiologist at the earliest opportunity 7
• Structured teaching on CXR interpretation should be provided to newly qualified doctors 7