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chest x-ray

Image: “Medical X-rays” by Nevit Dilmen. License: CC BY-SA 3.0


Introduction

Chest X-ray is the most commonly-ordered radiological screening test for pulmonary disease. Due to its low accuracy, however, correct interpretation requires experience. Keep the following general principles in mind: 

  • Obtain knowledge of the patient’s medical history and physical examination.
  • Follow one systematic approach every time you read a chest X-ray.
  • Compare frontal and lateral views and compare to older studies (if available).
  • Begin with differentials rather than a single diagnosis.
Note: We recommend studying the images and their descriptions as you read through this content.

Essential Elements of a Complete Search on a Frontal Chest X-ray

Preliminaries:

  • Confirm name, date, and time.
  • Distinguish PA (Image 1) from AP (Image 2). In AP view, findings are less accurate and pathology may be missed due to the following features:
    • Magnified heart
    • Widened mediastinum
    • More clearly defined posterior ribs
    • Prominent vascular markings
    • Incomplete inspiration: In image 2, 6th rib intersects diaphragm lateral to the midclavicular line. (Compare with image 1.)  
    • Superimposition of scapulas over the lung fields
    • Superimposition of clavicles over lung apices 
    • Superimposition of chin over the neck
    • Connected lines (e.g. chest leads in this image)
    • Endotracheal tube if intubated (not seen in this image)
  • Determine the side of the film based on the right or left marker.

Confirm appropriate technique in frontal PA view:

  • Performed in inspiration: 
    • 6th (range: 5th-7th) rib intersects diaphragm in midclavicular line anteriorly (diagonal ribs) (Image 1)
    • 8-10 posterior ribs (horizontal ribs) visualized above diaphragm
  • Penetration: 
    • Good penetration:
      • Vertebrae and posterior ribs are only faintly visible behind the heart. 
      • Left diaphragm is visible to the edge of the spine.
      • Lung fields are symmetrically dark.
      • Vascular markings are non-prominent and fade peripherally.
    • Under penetration (Image 3): Film appears whiter and above features are less apparent
    • Over penetration: Film appears darker and above features are less apparent.  
  • Rotation: 
    • There should be no rotation: Spinous processes are midway between the medial ends of the clavicles. (Image 1)
    • Rotation to right: 
      • Spinous processes appear closer to the left clavicle. (Image 4a)
      • Mediastinum and hilum on the right appear larger.
    • Rotation to left:
      • Spinous processes appear closer to the right clavicle. (Image 4b)
      • Mediastinum and hilum on the left appear larger.
  • Proper position:
    • Lungs: fully visible from apices above the clavicles to bases
    • No or minimal superimposition of scapula over lung fields
    • No superimposition of chin over the neck or arms over the peripheral chest

Image 1: Normal frontal X-ray in the PA view (i.e. patient faces the screen). By Stillwaterising – Own work. License: CC0 1.0

 

Image 2: Normal frontal chest X-ray in the AP view (i.e. patient’s back faces the screen) obtained with the patient in supine position.
By Khan AN, Al-Jahdali H, Al-Ghanem S, Gouda A. License: CC BY 2.0

Image 3: Frontal chest X-ray with poor technique showing under penetration. By Hetal Verma.

Image 4: Frontal chest X-ray with poor technique showing rotation. By Hetal Verma.

Perform a step-wise search in the frontal PA view:

Note: Many of the following features may apply to the AP and lateral views, as well.
  • Lungs:
    • Study from top to bottom and side to side: Note volume, symmetricity, and overall whiteness (Image 5). 
    • Apices: Check for symmetricity (Compare images 1 & 6)
    • Recognize significant opacities:
      • Larger than the diameter of nearest vessel
      • Cloud-like: consolidation (Image 7)
      • Extra lines: interstitial pattern (Image 8)
    • Check lung periphery: 
      • Pneumothorax (Image 9)
      • Costophrenic angles for effusions (Image 10)
      • Pleural-based masses (Image 11)
  • Mediastinal and cardiac borders and shape: Look for loss of normal silhouette (i.e. contrast caused by different densities of 2 adjacent structures such as the heart and lung). 
    • Normal bulges on the left side of the mediastinum from top to bottom: (Image 12)
      • Aortic knob
      • Main pulmonary artery
      • Left ventricle
    • Normal bulge on the right side: 
      • Right atrium
  • Trachea, paratracheal region (Image 13), angle of carina (Image 14), and main bronchi: Search for abnormal deviation, widening, and narrowing.
  • Hila: Search for enlargement or abnormal bulging (Image 15)
  • Trace the chest periphery from top to bottom:
    • Neck: Check both sides of the trachea
    • Chest wall:
      • Follow ribs especially at their turning points.
      • Observe the inferior margin of ribs for rib notching (Image 16), suggesting coarctation of aorta.
    • Bones 
    • Diaphragm 
      • Observe for shape and position: right diaphragm is normally higher.
    • Upper abdomen: search for free air under diaphragm (Image 17) and abnormal bowel gas, distension (Image 18) or location.

Image 5: Frontal chest X-ray in AP view and supine position shows increased whiteness of both lung fields with predominance in the central and lower areas of the lungs suggesting pulmonary edema.
By Lee BJ, Chen CY, Hu SY, Tsan YT, Lin TC, Wang LM. License: CC BY 2.0

Image 6: Frontal chest X-ray in PA view. Note the asymmetric lung apices that ultimately led to the diagnosis of poorly undifferentiated adenocarcinoma in this patient.
By Van Bael K, La Meir M, Vanoverbeke H. License: CC BY 2.0

Image 7: Frontal chest X-ray in a 67-year-old man with lobar pneumonia shows a cloud-like opacity or consolidation. By Mikael Häggström, M.D. License: CC0 1.0

Image 8: Frontal chest X-ray in the PA view shows diffuse interstitial opacities (reticulonodular) with predominance in the lower areas. Compare with image 1 to better appreciate the extra lines throughout the lung fields.
By Khalid I, Khalid TJ, Jennings JH. License: CC BY 3.0

Image 9: Frontal chest X-ray in the PA view shows left-sided pneumothorax. Arrow indicates the edge of the collapsed lung. No vascular markings are seen beyond this edge. By Mynameisderek – Own work. License: Public Domain

Image 10: Frontal chest X-ray in the AP view with the patient in the erect position. A right pleural effusion is recognized by the blunting of the right costophrenic angle (green arrow). The relatively normal left costophrenic angle does not exclude pleural effusion on the left side as effusions < 200 mL may not show up on chest X-ray. By Salih M, Aljarod T, Ayan M, Jeffrey M, Shah BH. License: CC BY 3.0

 

Image 11: Frontal chest X-ray shows a peripheral mass (white arrow). This patient had a rare finding of intrathoracic and subcutaneous splenosis years after post-trauma splenectomy.

Image 12: Normal frontal chest X-ray in PA view. The normal bulges include: aortic knob (thin arrow), pulmonary artery (thick arrow), left ventricle (solid arrowheads), right atrium (empty arrowheads).
By Stillwaterising – Own work. License: CC0 1.0

 

Image 13: Frontal chest X-ray in PA view in a patient with mediastinal tuberculosis. Note the abnormal bulging of the right side of the trachea due to significant regional lymphadenopathy.
By Maguire S, Chotirmall SH, Parihar V, Cormican L, Ryan C, O’Keane C, Redmond K, Smyth C. License: CC BY 4.0

Image 14: Frontal chest X-ray in the PA view shows marked cardiomegaly with a widened angle of carina indicating left atrial enlargement.
By Darwazah AK, El Sayed H. License: CC BY 2.0

Image 15: Frontal chest X-ray in the PA view shows bilateral hilar lymphadenopathy (white arrows) in a patient with sarcoidosis.
By Conte G, Zugni F, Colleoni M, Renne G, Bellomi M, Petralia G. License: CC BY 3.0

Image 16: Frontal chest X-ray in the PA view shows rib notching in a patient with coarctation of aorta.
By Koletsis E, Ekonomidis S, Panagopoulos N, Tsaousis G, Crockett J, Panagiotou M. License: CC BY 2.0

Image 17: Frontal chest X-ray in the AP view in a patient in the erect position. The crescentic lucency (i.e. free air) beneath the curved white line (right hemidiaphragm) has resulted from intestinal perforation due to metastatic disease.

Image 18: Frontal chest X-ray in the AP view in the erect position. Note bowel distension in this patient with bowel ischemia.
By Journal of Medical Case Reports. License: CC BY 4.0

Essential Elements of a Complete Search on a Lateral Chest X-ray

Lateral chest X-ray is an adjunct to the frontal chest X-ray, especially for examining the retrosternal and retrocardiac airspaces.

Preliminaries: 

  • Confirm name, date, and time.

Confirm appropriate technique in frontal PA view: 

  • Performed in inspiration: 
    • Minimum of 10 posterior ribs visualized above diaphragm
  • Good penetration:
    • Ribs are only faintly visible behind the heart. 
    • Vascular markings are non-prominent but clear. 
  • Proper position:
    • Lungs: fully visible from apices to bases in the posterior costophrenic angle 
    • Sternum: seen anteriorly with superimposition of anterior ribs
    • Expected normal superimpositions:
      • Anterior ribs
      • Posterior costophrenic recess
    • No superimposition of chin over mediastinal structures or arms over the chest

Perform a step-wise search in the lateral view:

  • Lungs:
    • Observe size and shape
    • Retrosternal space:
      • Normally lucent
      • Opacity indicates pathology in upper lobes or anterior mediastinum. (Image 2)
    • Retrocardiac space:
      • Normally lucent
      • Opacity indicates pathology in lower lobes or posterior mediastinum.
  • Diaphragms:
    • Contours of left and right diaphragms should be visible.
    • Evaluate flattening of the diaphragm by measuring the distance between the line drawn from the anterior to posterior costophrenic angles and the diaphragmatic dome: < 2.7 cm is abnormal (e.g. seen in emphysema)
  • Trachea to hilum:
    • Follow airways from neck to hilum: look for any widening, narrowing or deviations
    • Evaluate pulmonary arteries at the hilum and search for hilar lymphadenopathies
  • Cardiac borders: 
    • Anterior side:
      • Right ventricle
    • Posterior side from top to bottom: 
      • Left atrium
      • Left ventricle
      • Inferior vena cava
  • Follow heart upward as it darkens:
    • There is no edge at the top of the heart
  • Follow vertebrae downward as they darken:
    • Excessive lightning in the vertebrae above the diaphragm indicates adjacent consolidation or mass in the lower lung zones or posterior mediastinum 
  • Observe chest periphery:
    • Check for bowel gas and free air under the diaphragm
    • Move up the sternum into the neck and down the vertebrae and ribs and search for pleural effusion at the costophrenic angle.

Image 1. By: Hetal Verma.

Image 2: Frontal (a) and lateral (b) chest X-ray in a patient with newly diagnosed Hodgkin’s lymphoma: a) Note the widening of mediastinum mainly due to 2 abnormal bulges (arrows); b) Note the opacity in the normally lucent retrosternal space.
By Ellis AK, Waserman S. License: CC BY 2.0

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