Chest X Ray Interpretation

Related Subjects: |Chest X Ray Interpretation |Chest X Ray Collection

📖 Introduction

• Postero-anterior (PA): Standard view. Patient stands facing the plate, scapulae rotated out. Best quality, less cardiac magnification.
• Antero-posterior (AP): Portable view in sick patients. Heart shadow appears larger, often poorer inspiration/quality.
• Lateral (LAT): Used to assess posterior mediastinum, retrosternal and retrocardiac areas. CT is usually superior for localisation.

🧭 Technical Quality Checks

• ✅ Patient details: name, DOB, date/time of CXR.
• ✅ Projection: PA or AP? (important for heart size).
• ✅ Rotation: medial clavicles equidistant from spinous processes.
• ✅ Inspiration: ≥6 anterior ribs above diaphragm.
• ✅ Penetration: vertebrae just visible behind heart.

🫁 Normal Anatomy & Landmarks

📊 Stepwise Interpretation of a CXR (ABCDE)

1. 📝 A – Airway – Trachea central? (deviation = effusion, pneumothorax, collapse, mass). – Carina and main bronchi visible.
2. 🦴 B – Bones & Soft Tissues – Ribs, clavicles, scapulae, vertebrae → fractures, lytic lesions, metastases. – Look for cervical rib, lytic deposits. – Breast shadows present? Absent shadow = mastectomy.
3. ❤️ C – Cardiac & Mediastinum – Heart size: cardiothoracic ratio >0.5 = cardiomegaly (only valid PA). – Aortic knuckle, pulmonary artery, mediastinal width. – Situs? (stomach bubble, cardiac apex).
4. ⬇️ D – Diaphragm – Right higher than left. – Sharp costophrenic angles? Blunting = pleural effusion. – Free air under diaphragm = perforated viscus. – Gastric bubble under left diaphragm.
5. 🌫️ E – Effusions / Equal Lung Fields – Compare both lungs side by side. – Peripheral absence of markings = pneumothorax. – Opacities = consolidation, collapse, mass, interstitial patterns. – “Bat’s wing” shadowing = pulmonary oedema.
6. 🔌 F – Foreign Bodies / Lines – NG tube → below diaphragm, midline. – Central line → tip at cavo-atrial junction. – ETT tube → 3–5 cm above carina. – Pacemakers, chest drains, prosthetic valves.
7. 🧭 G – Great Vessels & Hila – Left hilum slightly higher than right. – Unilateral enlargement → TB, cancer, lymphoma. – Bilateral hilar enlargement → sarcoid, TB, lymphoma.
8. 🔍 H – Hidden Areas (Final Sweep) – Apices: small PTX, Pancoast tumour. – Behind the heart: pneumonia, hiatus hernia. – Bones again: subtle fractures, mets. – Soft tissues: subcutaneous emphysema.

📌 Common Pathologies on CXR

• 🌫️ Lobar consolidation (pneumonia)
• 💨 Pneumothorax (loss of markings)
• 💦 Pulmonary oedema (bat’s wing)
• 🌪️ Pleural effusion (meniscus sign)
• 📉 Lobar collapse (volume loss, mediastinal shift)
• 🫀 Cardiomegaly (CT ratio >0.5 PA)
• 🦠 TB (upper zone cavitation, fibrosis, hilar nodes)
• 🎯 Lung mass / Pancoast tumour
• 📍 NG tube / central line / pacemaker position

⚠️ “Normal” CXR in Sick Patients

• Asthma, COPD
• Pulmonary embolism
• Early pneumonia
• Pneumocystis pneumonia
• ARDS (may evolve)
• DKA with Kussmaul breathing (normal CXR)

🚨 Things Commonly Missed

• Apices: small pneumothorax, Pancoast tumour.
• Retrocardiac: pneumonia, hiatus hernia, vertebral lesions.
• Cardiac: valve calcifications.
• Skeletal: cervical rib, subtle mets.
• Gas: pneumoperitoneum, pneumomediastinum.
• Soft tissue: absent breast shadow (mastectomy).

🌿 Fibrosis Patterns

• Upper zone: TB, sarcoid, silicosis, ankylosing spondylitis, hypersensitivity pneumonitis.
• Lower zone: idiopathic pulmonary fibrosis, asbestosis, connective tissue disease (RA, SLE, SSc), drugs (amiodarone, bleomycin, methotrexate).

🔎 Classic Exam Findings

• 🫧 Bilateral hilar lymphadenopathy → sarcoid, TB, lymphoma.
• 🫀 Opaque hemithorax → effusion, consolidation, collapse, pneumonectomy.
• 🕳️ Cavitating lesion → TB, abscess, squamous carcinoma, septic emboli.
• ⚡ Pneumothorax → absent markings, pleural edge.
• 💦 Pulmonary oedema → peri-hilar “bat’s wing” shadowing.

💡 Teaching Pearls: – Always start with technical quality before pathology. – Use a systematic approach (A → H). – Comment on tubes and devices. – A “normal CXR” does not exclude serious pathology (PE, asthma, early pneumonia, PCP).