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ChestDemonstration data

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.