Chest X-ray Interpretation High-Yield Guide

Quick systematic approach

• Airway (trachea, carina, bronchi)

• Bones (ribs, clavicles, spine, shoulders)

• Cardiac (size, borders, CTR <0.5)

• Diaphragm (position, costophrenic angles)

• Extrathoracic (soft tissues, lines, tubes)

• Fields (lung zones, compare sides)

• Great vessels (aorta, mediastinum)

• Hila (size, position, density)

• Inspect hidden areas (behind heart, below diaphragm, apices)

Technical quality checklist

• Projection: PA (preferred) vs AP (magnifies heart, portable)

• Rotation: Medial clavicle heads equidistant from spinous processes

• Inspiration: 5-6 anterior ribs or 9-10 posterior ribs visible

• Penetration: Vertebrae just visible behind heart

• Patient position: Centralized, scapulae rotated out

Priority abnormalities to spot

• Absent lung markings peripheral to visceral pleural line

• Look at apices on expiration film if suspected

• Tension: mediastinal shift away, flattened hemidiaphragm

• Air space opacification

• Air bronchograms visible

• Lobar or patchy distribution

• Common locations: RLL, RML, lingula

• Volume loss: elevated hemidiaphragm, mediastinal shift toward

• Crowded ribs on affected side

• Silhouette sign helps localize lobe

• Blunted costophrenic angle (>75 mL)

• Meniscus sign on upright

• Complete opacification if massive

• Associated with collapse if significant

• Upper lobe blood diversion (early)

• Kerley B lines (interstitial)

• Bat wing/perihilar opacity (alveolar)

• Pleural effusions (often bilateral)

• Site: Which lobe/zone (lung vs zone/lobe)

• Size: Measure in cm

• Number: Solitary vs multiple

• Shape: Round, irregular, spiculated

• Margin: Smooth vs irregular

Cardiothoracic ratio (CTR)

• Measure widest cardiac diameter ÷ widest thoracic diameter

• Normal: <0.5 on PA film

• Cardiomegaly: >0.5

• Remember: AP films magnify heart, CTR unreliable

Silhouette sign

• Right heart border loss → RML or anterior segment of RUL

• Left heart border loss → Lingula or anterior LUL

• Right hemidiaphragm loss → RLL

• Left hemidiaphragm loss → LLL

• Aortic knob loss → LUL (posterior)

Hidden areas (commonly missed)

• Apices: Pancoast tumor, pneumothorax

• Behind heart: LLL collapse/consolidation

• Below diaphragm: Free air (Rigler sign)

• Lung periphery: Pneumothorax, rib fractures

• Soft tissues: Surgical emphysema, masses

Lines and tubes positioning

• ETT tip: 3-5 cm above carina (T4-T5 level)

• NGT: Below diaphragm, in stomach

• Central line: SVC, tip at cavoatrial junction

• Chest drain: In pleural space, not in fissure

Common exam patterns

• Most common cause of unilateral white-out → massive pleural effusion

• Sail sign → LUL collapse

• Golden S sign → RUL collapse with central mass

• Air under diaphragm → perforated viscus

• Rigler sign (double wall sign) → pneumoperitoneum

• Kerley B lines → pulmonary edema or lymphangitis

Reporting structure

1. Patient details: Name, ID, date, projection

2. Technical quality: Adequate/inadequate with reasons

3. Systematic review: Describe findings in each area

4. Abnormalities: List and describe all abnormalities

5. Clinical correlation: Compare with previous if available

6. Conclusion: Summary statement with differential or provisional diagnosis

Quick differential builders

• Massive pleural effusion (most common)

• Complete lung collapse

• Consolidation (extensive pneumonia)

• Large mass

• Tuberculosis

• Sarcoidosis

• Silicosis

• Ankylosing spondylitis

• Aspiration

• Pulmonary edema

• Bilateral effusions

• Interstitial lung disease (UIP, NSIP)

• Metastases (most common)

• Infection (septic emboli, abscesses)

• Granulomas (TB, fungal)

• Vasculitis (GPA)

Red flags requiring urgent action

• Tension pneumothorax

• Massive pulmonary embolism

• Ruptured aortic aneurysm

• Perforated viscus with free air

• Mediastinal widening (trauma/dissection)