the chest X-ray (CXR)

see also:

• radiology
• wikipedia - chest radiograph
• CXR atlas
• Emedicine chest imaging articles
• Medical student CXR interpretation tutorial
• RadiologyED.org resource library
• LITFL's 150 top CXR cases/quizzes

• optimise room lighting by turning off stray lights - unfortunately this is not likely to be possible in most ED's
• check patient name and date of examination
• check how the CXR was taken - AP/PA, supine or erect, inspiration or expiration
  • patient/film position
    • AP film gives magnification of heart and widening of the mediastinum, and thus is generally only done in those unable to sit upright in PA position (front of chest towards the Xray film with Xray tube placed 6 feet away)
    • lateral decubitus position:
      • handy to assess:
        • pleural effusions - volume, loculation or mobile
        • possible pneumothorax in a patient who cannot sit up:
          • pneumothorax may be visible superiorly if it involves the non-dependent lung
          • the dependent lung should appear denser due to the weight of the mediastinum upon it, failure to do so suggests air trapping and possible pneumothorax of the dependent lung.
  • degree of inspiration
    • well inspired film
      • diaphragm should be at level of 8-10th ribs posteriorly or the 5-6th ribs anteriorly
      • poorly inspired or expiratory films create artefacts such as loss of R heart border, presence of air bronchograms
    • is it hyper-inflated with flattened diaphragms suggesting acute asthma or emphysema?
    • inspiratory and expiratory films may be done to help diagnose pneumothorax or inhaled foreign bodies (which cause unilateral air trapping and tracheal shift in expiration)
  • is it adequately exposed (“penetrated”)?
    • on a good PA film, one should see the bronchovascular markings and just be able to see the thoracic spine disc spaces through the cardiac shadow but not see the bony details of the spine
    • on a good lateral film, the spine should become darker as one looks down the spine as there is more air and less chest wall inferiorly
  • is it rotated?
    • on a PA, clavicular heads should be equidistant from the spinous processes of the vertebral bodies
    • rotated films cause artefacts such as displaced trachea and presence of skin folds which could be mistaken for tension pneumothorax
    • on a lateral film, the sternum should be seen edge on and there should be two sets of ribs seen posteriorly

• trachea - midline shift, caliber, mass
• bilateral breast shadows:
  • patients who have had a mastectomy will have apparent assymetric lung densities on the PA film and can be mistaken for pneumonia
  • nipples may be mistaken for pulmonary nodules
• lung markings
  • ensure you use a systematic visual scanning process that covers each part of the film
  • is there a pneumothorax?
  • is there consolidation, collapse, ill-defined infiltrate or a well-defined mass?
  • silhouette sign - loss of a normal outline (eg. cardiac or diaphragm) by adjoining similar density tissue (eg. consolidation)
    • loss of R heart border suggests RML consolidation
    • loss of diaphragm suggests lower lobe consolidation or pleural effusion
  • air bronchograms can be caused by consolidation, pulmonary oedema, non-obstructive atelectasis, severe interstitial disease, neoplasm or normal expiration
  • which diaphragm is which on the lateral film?
    • R diaphragm can be seen anteriorly while the L diaphragm cannot be seen due to silhouette with the heart
    • R diaphragm continues posteriorly past the smaller looking left ribs and ends at the larger looking right ribs - in a true lateral with left chest against the X-ray film, the right ribs are magnified compared to left ribs and thus appear larger
  • elevated hemidiaphragm
    • aetiology: phrenic nerve palsy; eventration; infradiaphragmatic mass; etc.
    • see elevated hemidiaphragm
  • diaphragmatic herniae
    • hiatus hernia
    • Bochdalek hernia - posterior, left side
    • Morgagni hernia - medial
    • eventration - usually right with liver bulging superiorly
• gas under right diaphragm
  • bowel gas between liver and right diaphragm
    • this is called Chilaiditi syndrome which occurs in 1% older adults and is usually of no consequence
  • free gas under the right diaphragm
    • may be due to:
      • perforated viscus - a surgical emergency - call surg reg ASAP
      • post-laparoscopy/laparotomy air
      • penetrating abdominal trauma
• pulmonary vessels - artery or vein enlargement
• hila - masses or LN's
  • R. hilum displaced downwards may suggest RLL collapse which can be hard to see on PA view.
  • enlarged LN's (generally lumpy rather than smooth contour):
    • inflammation - sarcoidosis, silicosis, etc
    • neoplasm - lymphoma, metastases, bronchogenic Ca
    • infection - tuberculosis (TB), histoplasmosis, EBV / glandular fever / infectious mononucleosis
  • enlarged pulmonary artery (smooth rather than lumpy contour)
• heart - size, local contour pathology eg. enlarged left atrium, lung lesions behind the cardiac shadow
  • pericardial effusion - check lat. view for fat pad sign >2mm between epicardial fat and ant. mediastinal fat. Enlarged cardiac outline requires > 400ml fluid to be present.
• mediastinum - widened, mass?, vertical streaks suggesting pneumomediastinum?
  • anterior mass: LN's, thymus, teratoma, thyroid mass, aortic aneurysm, pericardial cyst, epicardial fat pad
  • middle mass: LN's, hiatus hernia, aortic aneurysm, thyroid mass, duplication cyst, bronchogenic cyst
  • posterior mass: neoplasm, LN, aortic aneurysm, adjacent lung or pleural mass, neurenteric cyst, lateral meningocele, extramedullary haematopoiesis, neuroblastoma
• pleura - effusions, thickening or calcification
  • horizontal (minor) fissure on the right lung of a PA film - position, ?effusion present
  • major fissures on the lateral film
  • pleural mass: metastases (esp. adenoCa, malignant thymoma), loculated pleural effusions, mesothelioma, pleural plaques from asbestosis, lymphoma
  • extra-pleural masses: rib tumour, rib infection, neurofibroma, schwannoma, lipoma
  • see also pleural effusion
• bones - lesions or fractures
• soft tissue - eg. mastectomy
• tubes, wires, etc - ETT position, NGT position, CVC, pacemaker, sternotomy wires, prosthetic heart valves

• collapse (reduced lobar volume) which usually causes a linear increased density with its apex near the hilum
• past scarring attaching lung to chest wall may cause a rounded peripheral atelectasis
• segmental collapse may be linear, curvilinear, or wedge-shaped opacities
• indirect radiographic signs of volume loss:
  • vascular crowding
  • fissural, tracheal or mediastinal shift towards the atelectasis
  • compensatory hyperinflation of adjacent lobes
  • hilar shift - eg upwards if upper lobe collapse, downwards if lower lobe collapse
• other signs:
  • RUL collapse:
    • easily detected on PA film - superomedial migration of upper lobe with shift of horizontal fissure with curvilinear border with concavity facing inferiorly
  • LUL collapse:
    • anterior shift of LUL and loss of left upper cardiac border
    • hyperinflation LLL which moves superiorly to fill space behind LUL ⇒ lower lobe artery shifts superiorly, left mainstem bronchus rotates to a nearly horizontal position
    • Luftsichel Sign - lucency between the mediastinum and the collapsed LUL due to hyperinflation of superior segment of LLL
  • RML collapse:
    • may be difficult to see on PA film with main finding loss of R cardiac border and easily confused with consolidation
    • best seen on lateral film as wedge shaped opacity over the cardiac shadow with apex at hilum
  • lower lobe collapse:
    • can be difficult to see on PA - triangular opacity post/medially against mediastinum; ipsilateral hilum shifted down; silhouette of descending aorta if left lobe, possible elevation of hemidiaphragm.
    • on lateral - silhouette sign with diaphragm

• endobronchial obstruction - eg. mucus plug (esp. post-op, or acute asthma), tumour, inhaled foreign body
• extrinsic bronchial compression - eg. tumour, lymph nodes
• peripheral compression eg. large pleural effusion
• scarring eg. TB, radiation Rx

• consolidation - eg. pneumonia
• pulmonary oedema - cardiogenic, ARDS, near-drowning, etc
• pulmonary haemorrhage (usually clears rapidly) - trauma, Goodpasture's synd., bleeding disorders, high altitude, mitral stenosis
• pulmonary contusion
• pulmonary fibrosis
• pulmonary infarct - usually fairly well defined peripheral wedge shaped opacity eg. pulmonary embolism (PE)

• increased density of lung shadow with indistinct borders (except where outlined by fissures) but normal or increased lobar volume
• no shift, or if present then contralateral (ie. towards opposite side in contrast to that which occurs in atelectasis)
• apex not centered at hilum as with atelectasis
• air bronchograms may be present, particularly if lobar consolidation

• cephalisation of upper lobe vessels or “upper lobe diversion” (ie. upper lobe vessels become more prominent and dilated) once pulmonary capillary wedge pressure (PCWP) > 12mmHg
• Kerley B lines due to interstitial oedema (occurs if PCWP > 18mmHg)
• peribronchial cuffing
• “bat wing” pattern as it becomes more severe due to alveolar oedema (PCWP > 24mmHg) with potential loss of cardiac borders and diaphragms from silhouetting
• patchy shadowing with air bronchograms
• cardiomegaly
• may be unilateral lung signs if patient has been lying on one side
• atypical patterns in patients with upper lobe emphysema
• +/- pleural effusions

• hazy “ground glass” opacification early and volume loss with linear opacities bilaterally
• honeycomb lung in the late stages

• idiopathic (>50%)
• collagen vascular disease
• cytotoxic agents, nitrofurantoin
• pneumoconioses
• radiation
• sarcoidosis

• is it within the chest or external - check other views
• discrete opacities within the lung may be caused by:
  • neoplasm - benign (eg. hamartoma) or malignant - primary or secondary (eg. neo_renal)
  • granuloma - eg tuberculosis (TB)
  • infection - eg. round pneumonia, abscess
  • vascular - infarct (eg. pulmonary embolism (PE)), varix, Wegener's granulomatosis, rheumatoid arthritis, A-V malformation
  • round atelectasis

• double size < 1 month ⇒ sarcoma, infection, infarction, vascular
• double size 6-18 months ⇒ benign tumour, malignant tumour, granuloma
• double size > 24 months ⇒ benign nodule, malignant tumour
• calcification
  • central, laminated or diffuse pattern suggests granuloma
  • eccentric suggests cancer
• smooth margin
• lobular margin
• corona radiata
• shape
• site

• infection - tuberculosis (TB), fungal, septic emboli
• neoplasm - metastases, lymphoma, hamartoma
• sarcoidosis
• alveolitis
• auto-immune disease - Wegener's granulomatosis, rheumatoid arthritis
• pneumoconioisis

• neoplasm - usually malignant
• infarct - usually pulmonary embolism (PE)
• infection - esp. staphylococcus, tuberculosis (TB), Gram negative bacteria (esp. klebsiella sp), anaerobic bacteria, fungi
• Wegener's granulomatosis

• horizontal lines < 2cm long, usually in the lower zones which represent thickened, oedematous interlobular septa.
• acute pulmonary oedema (APO)
• lymphangitis carcinomatosis
• lymphoma
• viral and mycoplasma pneumonia
• interstitial pulmonary fibrosis
• pneumoconiosis
• sarcoidosis

• see also tuberculosis (TB) and wikipedia

• infiltrate or consolidation
• cavitating lesion
• nodule with poorly defined margin
• pleural effusion
• hilar or mediastinal lymphadenopathy
• prominent interstitial linear markings in children
• miliary TB - multiple 1-2mm nodules throughout the lung fields

• discrete fibrotic scar
• discrete nodule with well defined margin
• upper lobe bronchiectasis