Chest x-ray - an approach (summary)

Systematic Review

Image quality

• position: PA erect CXR in full inspiration (semi-erect or supine AP in sick patient)
• penetration: disc spaces of lower thoracic spine visible
• rotation: medial ends of the clavicles equidistant from the spinous processes
• inspiration: 10 to 11 posterior ribs on left side

Heart

Assess the heart size and shape on fully inspired PA films

• cardiothoracic ratio (maximal cardiac diameter/maximal thoracic diameter) should be <50%

Mediastinum & Hila

Assess the trachea for deviation, narrowing or intraluminal lesions

• if deviated towards, think volume loss
• if deviated away, think volume gain

Assess the mediastinal width

• if widened, think mediastinal mass or vascular abnormality

Check hila position, equal density and normal branching vessels

• left hilum normally higher than right

Lungs

Look for areas of increased density comparing the left and right upper, middle and lower zones

• Ifif increased density, think consolidation, atelectasis, interstitial or nodule/mass

Ensure the heart borders and domes of diaphragm are clearly defined

• Ifif not, think consolidation +/- collapse
• localise:  right heart border = RML, left heart border = LUL, right diaphragm dome = RLL, left diaphragm dome = LLL

Assess the vascular markings

• vessels should taper and be almost invisible at the peripheries
• lower lobe vessels are larger than upper lobe on erect films

Pleura

Assess the horizontal fissure for fluid or displacement

• if displaced upwards, think volume loss of RUL
• if displaced downwards, think volume loss of RLL

Check the costophrenic and cardiophenic angles

• Ifif costophrenic angle is blunted, think pleural effusion

Diaphragm

Assess shape, position and below for free air

• right hemidiaphragm should be higher than the left (1-3cm)
• if flattened, think hyperinflation
• Ifif free air, think pneumoperitoneum

Thoracic wall & Softsoft tissue

Scan the ribs, clavicles, scapulae and spine for fractures and bony destruction.

Scan the soft tissues for breast shadows, surgical emphysema and foreign bodies.

Review areas

Double-check the apices (masses, pneumothorax), hila (masses, lymphadenopathy), retrocardiac zone (lobar collapse, hiatus hernia) and below the diaphragm (tubes and free air).

Finally, always compare to old films.

Common pathology

Pneumonia

• most common cause of death due to infectious diseases
• higher incidence at the extremes of age
• streptococcus pneumoniae - most common organism
• homogenous opacification in lobar pattern
• characteristic air bronchograms and volume loss
• more: lobar pneumonia

Lobar collapse

• due to obstruction; luminal (aspiration, mucous plugging), mural (cancer) or extrinsic (mass compression)
• RUL: right upper medial opacification, elevated horizontal fissure and right hilum
• LUL: left hemithorax ‘veil-like’ opacity, elevated left hilum
• RML: horizontal fissure not visible, ill-defined right heart border
• RLL: right medial basal triangular opacification, depressed right hilum
• LLL: left retrocardiac triangular opacification, double cardiac contour, depressed left hilum, loss of descending aortic and left medial hemidiaphragmatic outline
• secondary signs: elevated hemidiaphragm, crowding of ribs and mediastinal shift towards affected side
• more: lobar collapse

Pneumothorax

• air in pleural space
• categorised as primary spontaneous, secondary spontaneous (underlying lung disease) or iatrogenic/traumatic
• simple: clearly defined visceral pleural edge paralleling chest wall, peripheral lucency with absent lung markings
• tension: overexpanded hemithorax, depressed hemidiaphragm, contralateral mediastinal shift
• more: pneumothorax

Congestive cardiac failure

• commonly due to left ventricular failure
• stage 1: redistribution (upper lobe diversion, cardiomegaly)
• stage 2: interstitial oedema (Kerley B lines, peribronchial cuffing, hazy hilar vessels)
• stage 3: alveolar oedema (consolidation, air bronchogram, cottonwool appearance, pleural effusion)
• more: congestive cardiac failure

Pleural effusions

• collection of fluid within pleural cavity
• most commonly due to cardiac failure (transudate) or malignancy (exudate)
• >200ml fluid required for meniscus at costophrenic angle on erect CXR
• opaque hemithorax and contralateral mediastinal shift in large volume effusions
• hydropneumothorax - no meniscus visible
• more: pleural effusion

Lung carcinoma

• leading cause of cancer mortality worldwide
• divided into non-small cell and small cell carcinomas
• adenocarcinoma most common histological subtype
• may present as a peripheral rounded or spiculated mass, hilar/perihilar mass, mediastinal widening, lobar collapse or pleural effusion
• more: lung carcinoma

Pulmonary metastases

• metastatic spread to lungs via blood or lymphatics
• most common primaries include breast cacancer, colorectal cacancer and renal cell cacancer
• peripheral, rounded nodules scattered throughout lungs
• more: pulmonary metastases

Pneumoperitoneum

• gas within peritoneal cavity
• commonly due to perforated hollow viscus, post-laparoscopy-operative, peritoneal dialysis
• subdiaphragmatic free gas on erect CXR
• beware of pseudopneumoperitoneum - basal linear atelectasis and Chilaiditi syndrome
• more: pneumoperitoneum