What structures and abnormalities can be seen on a chest x-ray?

Structures and Abnormalities Visible on Chest X-Ray

Normal Anatomical Structures

A chest radiograph can visualize multiple thoracic structures including the heart, mediastinum, lungs, pleura, diaphragm, ribs, clavicles, thoracic spine, and the aorta with its characteristic contours. 1

Cardiovascular Structures

• The cardiac silhouette is visible, with the right heart border formed by the right atrium and the left border by the left ventricle 1
• The aortic arch, ascending aorta, and descending aorta can be identified, with the aortic knob typically visible on posteroanterior views 1
• The mediastinum should have a sharply demarcated normal contour 1

Pulmonary Structures

• Lung parenchyma is visible bilaterally, though chest radiography has limited sensitivity for detecting early parenchymal changes 1
• The pleural spaces can be assessed, though radiographs detect only 50-80% of pleural thickening compared to CT 1
• The diaphragm should appear as smooth hemidiaphragmatic contours 1

Skeletal Structures

• Ribs, clavicles, sternum, and thoracic vertebrae are visible and should be assessed for fractures or other abnormalities 1
• Cervical ribs or first rib anomalies may be identified, which are relevant in thoracic outlet syndrome 2

Common Abnormalities Detectable on Chest X-Ray

Pulmonary Pathology

• Pneumothorax: Loss of lung markings peripherally, though sensitivity is limited and expiratory films do not improve detection 3
• Pleural effusion: Blunting of costophrenic angles or larger collections 1
• Pneumonia/consolidation: Airspace opacities, though chest radiographs have limited sensitivity and specificity, with interpretation challenges 4, 5
• Atelectasis: Volume loss and increased opacity 6

Cardiovascular Abnormalities

• Widened mediastinum: May suggest aortic pathology, though sensitivity is only 64% for aortic dissection 1
• Abnormal aortic contour: Can indicate aneurysm or dissection, with 71% sensitivity 1
• Cardiomegaly: Enlarged cardiac silhouette 1
• Hemopericardium: Enlarged cardiomediastinal silhouette 1

Skeletal Abnormalities

• Rib fractures: Detected in only 4.9% of nontraumatic chest pain cases, with chest radiographs missing 50% of fractures compared to CT 1
• Sternal fractures: May indicate cardiac contusion 1
• Displaced rib fractures (especially ribs 3-9): May suggest underlying cardiac injury 1

Diaphragmatic Abnormalities

• Hemidiaphragm elevation: May indicate diaphragmatic hernia 1
• Abnormal bowel gas pattern or air-fluid levels in thorax: Suggests diaphragmatic hernia, though sensitivity is only 2-60% for left-sided and 17-33% for right-sided hernias 1

Critical Limitations of Chest Radiography

Chest radiographs are insensitive for many important pathologies and should not be relied upon to definitively exclude disease in most clinical scenarios. 1, 5

Key Limitations

• Perceptual errors are the predominant source of missed findings and a leading cause of malpractice lawsuits 5
• Normal chest radiographs occur in 11-62% of diaphragmatic injuries, 15-20% of asbestosis cases, and frequently in early interstitial lung disease 1
• Rib cartilages, costochondral junctions, and chest wall soft tissues are poorly visualized 1
• Portable/AP radiographs have additional technical limitations including motion artifacts and limited mediastinal evaluation 1

When CT is Superior

• CT chest with IV contrast provides superior characterization of lung parenchymal changes, pleural abnormalities, mediastinal pathology, and chest wall lesions 1, 6, 7
• CT is the gold standard for diagnosing diaphragmatic hernia (sensitivity 14-82%) and thoracic aortic disease (sensitivity up to 100%) 1
• CT detects 80% more hemothorax cases and 50% more vertebral/rib fractures than chest radiographs 1

Clinical Pitfalls to Avoid

• Do not rely solely on chest radiographs to exclude pneumothorax, rib fractures, aortic dissection, or diaphragmatic injury in high-risk patients 1
• Radiographs not taken at full inspiration may mimic lung disorders and lead to misdiagnosis 8
• Junior clinicians have significantly lower accuracy in interpretation; all chest radiographs should be reviewed by senior clinicians and reported by radiologists 9
• Commonly missed findings include subtle pneumothorax, small pleural effusions, rib fractures, and early infiltrates 5