Chest X-Ray (PA/Lateral)

The PA and lateral chest radiograph is the most frequently performed imaging examination worldwide and the first-line study for evaluating the thorax. It provides a rapid, low-dose overview of the lungs, mediastinum, heart, pleura and bony thorax, and guides decisions about further cross-sectional imaging. Despite the rise of CT, the plain chest radiograph remains the workhorse for triage of cardiorespiratory symptoms and monitoring of inpatients.

Indications

Suspected pneumonia, cough, fever or purulent sputum
Dyspnoea and suspected cardiac failure or pulmonary oedema
Pleuritic chest pain, suspected pleural effusion or pneumothorax
Screening or follow-up of pulmonary tuberculosis and other chronic infections
Evaluation of a suspected lung mass or metastatic disease
Assessment of COPD, bronchiectasis and interstitial lung disease
Confirmation of line, tube and device position (ETT, CVC, NGT, pacemaker)
Pre-operative assessment in selected patients and post-procedure surveillance

Contraindications & Cautions

No absolute contraindications; benefit almost always outweighs the small radiation dose
Pregnancy is not a contraindication when clinically indicated; use abdominal shielding and justify the request
Effective dose is very low (~0.02 mSv PA), equivalent to a few days of natural background radiation
Avoid unnecessary repeat films; apply ALARA and justify each examination
Supine/AP portable technique should be reserved for patients unable to stand, as it degrades assessment of cardiac size and effusions

Patient Preparation

No fasting or special preparation required
Remove clothing, jewellery, ECG leads and other metallic or radiopaque objects from the field
Explain the breath-hold; coach full inspiration for the PA film
Standard erect PA position: patient facing the detector, chin raised, shoulders rolled forward with hands on hips to rotate scapulae off the lung fields
For the lateral view the left side is placed against the detector with arms raised
Confirm patient identity and pregnancy status where relevant

Technique & Parameters

Standard projections: erect PA (frontal) and left lateral in full inspiration
Source-to-image distance 180 cm (72 inches) to minimise cardiac magnification
High kVp technique 110-125 kVp with a grid to reduce bony contrast and improve mediastinal penetration
Short exposure time to minimise motion; expose at end of a deep inspiration
Adequate inspiration shows 6 anterior or 9-10 posterior ribs above the diaphragm
Portable AP films use lower SID (~100 cm) and lower kVp; note the projection and position on the report
Additional views as needed: expiratory film for pneumothorax, lateral decubitus for small effusions, apical lordotic for apical lesions

Systematic Review

Check demographics, projection, side markers, rotation, inspiration and penetration (adequacy)
A - Airway: tracheal position central, carina, main bronchi
B - Breathing: lung fields zone by zone, symmetry, vascular markings, pleural surfaces and costophrenic angles
C - Circulation: cardiac size (cardiothoracic ratio <0.5 on PA), mediastinal contour, aortic knuckle, hila
D - Diaphragm: contours, right usually higher than left, subdiaphragmatic free air, gastric bubble
E - Everything else / Edges: bones (ribs, clavicles, spine, shoulders), soft tissues, breast shadows, review areas
Deliberately inspect hidden review areas: apices, behind the heart, retrodiaphragmatic lungs, hila and bones

Key Findings & Significance

Airspace (alveolar) consolidation with air bronchograms suggests pneumonia or pulmonary oedema
Cardiomegaly (CTR >0.5), upper-lobe diversion, Kerley B lines and effusions indicate cardiac failure
Blunting of the costophrenic angle indicates a pleural effusion (>200-300 mL to be visible on PA)
A visceral pleural line with absent peripheral lung markings indicates pneumothorax
A discrete opacity or nodule raises concern for malignancy, granuloma or metastasis
Upper-zone fibronodular change and cavitation suggest reactivation tuberculosis
Hyperinflation, flattened diaphragms and bullae suggest emphysema/COPD
Widened mediastinum may indicate lymphadenopathy, mass or aortic pathology

Differential Considerations

Airspace opacity: pneumonia, pulmonary oedema, haemorrhage, aspiration, adenocarcinoma
Solitary pulmonary nodule: granuloma, primary lung cancer, metastasis, hamartoma, carcinoid
Bilateral hilar enlargement: sarcoidosis, lymphoma, pulmonary arterial hypertension, infection
Reticular/interstitial pattern: pulmonary fibrosis, oedema, atypical infection, lymphangitis carcinomatosa
White-out hemithorax: large effusion, collapse, pneumonectomy, extensive consolidation
Cavitating lesion: TB, abscess, squamous cell carcinoma, septic emboli, granulomatosis with polyangiitis
Mediastinal widening: lymphadenopathy, thymic/germ cell mass, retrosternal goitre, aortic aneurysm or dissection

Pearls & Pitfalls

Always inspect the classic review areas where lesions hide: lung apices, hila, behind the heart, below the diaphragm and the bones
The lateral film discloses retrocardiac and posterior costophrenic lesions missed on the frontal view
A rotated film distorts cardiac and mediastinal contours; check clavicle symmetry before diagnosing cardiomegaly
Expiratory or supine films exaggerate cardiac size and vascular crowding - do not overcall failure
Silhouette sign: loss of a border localises pathology (right heart border = RML, left hemidiaphragm = LLL)
Skin folds, hair braids, clothing and companion shadows can mimic a pneumothorax line or mass
A small pneumothorax or subtle free air under the diaphragm is easily missed on a supine portable film

Structured Report

State projection (PA/AP, erect/supine), adequacy and comparison with prior films
Describe lungs and airways, pleura, cardiomediastinal contour, diaphragm, bones and soft tissues
Report any lines, tubes and devices and their positions
Give measurements where relevant (nodule size, CTR, effusion depth)
Impression: concise summary of significant findings and likely diagnosis
State clinically important negatives and give clear recommendations (e.g. CT for a nodule, follow-up film for resolution)

References

ACR-SPR-STR Practice Parameter for the Performance of Chest Radiography
Fleischner Society Glossary of Terms for Thoracic Imaging (Hansell et al., Radiology 2008)
Royal College of Radiologists iRefer: Making the Best Use of Clinical Radiology
Corne J, Pointon K. Chest X-Ray Made Easy, Elsevier
Fleischner Society 2017 Guidelines for Management of Incidental Pulmonary Nodules (MacMahon et al., Radiology 2017)

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

Chest X-Ray (PA/Lateral)

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References