Central Chest Opacities – CXR

Table of Contents

Table of Contents

August 2023

Samantha King, MD1, Daniel Gergen, MD1, Markus Wu, MD2
Section Editor: Tami J. Bang, MD3
Executive Editor: Brandon Fainstad, MD4

1. Fellow, Pulmonary and Critical Care Medicine, University of Colorado, 2. Assistant Professor, Cardiothoracic Diagnostic Radiology, University of Colorado, 3. Assistant Professor, Cardiothoracic Diagnostic Radiology, University of Colorado, and National Jewish Health, 4. Associate Professor, Medicine, University of Colorado

Objective(s)

  1. Identify a lower lobe consolidation based on the diaphragm silhouette sign and positive spine sign.
  2. Identify a retrocardiac opacity by noting the obscuration of lung markings.
  3. Use pleural fissures to determine the location of right upper lobe pneumonia.
  4. Construct a differential diagnosis for cavitary lung lesions based on size, air- or fluid-filled, wall thickness, location, and surrounding parenchymal changes
  5. Determine appropriateness for sputum cultures, blood cultures, and urine antigens in a patient with CAP.
  6. Identify appropriate antibiotic coverage for CAP in ambulatory patients either with comorbidities or without comorbidities.
  7. Identify a peripheral opacity with concerning clinical features that justify obtaining cross-sectional imaging.
  8. Determine the most appropriate approach to biopsy a suspicious lung nodule.

Teaching Instructions

Preparation: Plan to spend 45 minutes to an hour familiarizing yourself with the background information below, key findings on the chest radiographs, and the progressions of animations on the PowerPoint. This conference is intended as the introduction to our six-part chest radiograph conference series.  Each case builds on foundational concepts introduced in the preceding case conferences from this curriculum:

 

How to present: Present the PowerPoint either by expanding the window (bottom right icon on the viewer below) in a browser or downloading the PowerPoint file to use on a desktop app (downloading is recommended).  Have the image pulled up in presenter mode before learners look at the screen to avoid revealing the diagnosis. Each case progresses through three or more questions, beginning with an overall interpretation, identification of a generalizable rule, and a clinical integration question.  We recommend a pair-share structure with a junior and senior trainee.  For each successive question, the presenter can elect to have pairs discuss their thoughts and then ask for a volunteer to share or, to expedite the conference, simply ask for an audience response.  Ask a learner to provide an overall interpretation.  Advance using the keyboard arrows or mouse click to reveal subsequent questions and then answers with their accompanying graphics.  You can go back to prior graphics and questions by using the back arrow or scrolling back on the mouse wheel.

Case 1: PA Enlargement

Official CXR Read: Right-sided central venous catheter with tip terminating in the SVC. Cardiomegaly with massive enlargement of the central pulmonary arteries.  Faint ill-defined opacities bilaterally are redemonstrated and unchanged when compared to prior CTs.  Minimal left basal atelectasis/scarring.  No consolidation pleural effusion, or pneumothorax. No acute osseous abnormality.

Severe enlargement of the main pulmonary artery measuring up to 6.2 cm.

Diagnosis: Familial PAH (Class 1) with severe enlargement of the main pulmonary artery.

Teaching

    • Enlarged cardiac silhouette is defined as a cardiac silhouette that is greater than half of the internal thoracic diameter. The differential for an enlarged cardiac silhouette on chest radiograph includes, cardiomegaly, pericardial effusion, and portable/AP film.
    • The differential for perihilar enlargement includes lymphadenopathy, malignancy, pulmonary arterial hypertension, and pulmonary venous hypertension. In this case, the smooth contours of the of the vessels, lack of interstitial pattern to indicate pulmonary edema, and the clinical history, indicate pulmonary arterial hypertension.
    • From top to bottom, the normal moguls are the aortic knob, left main pulmonary artery, and left ventricle. A possible fourth mogul (between the left main PA and LV) is the left atrial appendage (not visualized in this image).
    • The “moguls” are used to identify pathologic enlargement of left-sided structures of the cardiomediastinal silhouette. Enlargement of a mogul indicates pathology.

Case 2: Hilar LAN

Official CXR Read: Rounded, bulky densities in the bilateral hila and paratracheal region.

Diagnosis: Sarcoidosis with bulky hilar lymphadenopathy. This is a case of Lofgren's syndrome: acute arthritis, EN, and hilar lymphadenopathy

Teaching

    • The hilum consists of blood vessels (pulmonary arteries and veins) and the main bronchi of the lung. On CXR, “hilar points” are the angles (which look like horizontal ‘vees’) formed by pulmonary arteries sloping up and down.  The fact that these opacities do not taper (look more like potatoes) tells you this is lymphadenopathy, not pulmonary hypertension. On a normal CXR, hilar lymph nodes cannot be seen. When there are enlarged lymph nodes, they will disrupt the normal appearance of a tapering pulmonary vessel.
    • Common causes of hilar lymphadenopathy include inflammation (sarcoidosis, silicosis), neoplasm (lymphoma, metastases, bronchogenic carcinoma), and infection (TB, infectious mono).
    • Typically, a case of suspected sarcoidosis requires a biopsy for confirmation.  The case of Lofgren’s syndrome (the triad of hilar LAN, acute arthritis, and EN), is an exception given the high specificity of this triad in a young adult.  It is appropriate to treat empirically with NSAIDs and escalate to steroids if there is not a good response to NSAIDs alone.  If still not responding, may require additional imaging or biopsy.

Case 3: Hilar lung mass 

Official CXR Read: Right hilar pulmonary mass with right upper lobe volume loss suggesting at least partial bronchial obstruction centrally.

Diagnosis: Primary Squamous Cell Carcinoma of the Lung.

Teaching:

    • There is a partial upper lobe collapse from compression of the R bronchus.  Signs of volume loss (light green arrows) include upward displacement of the minor fissure, “peaking” of the right hemidiaphragm, and rightward displacement of the trachea.  This may be confusing because malignancies are ‘space-occupying' lesions. This case demonstrates how the mass is obstructing part of the upper lobe airways, leading to partial collapse.  The remaining right upper lobe remains lucent, so there is not a complete upper lobar collapse.
    • Squamous cell and Small cell lung cancers are more commonly Central.  Adenocarcinomas are more commonly peripheral.2

Case 4: Cardiomegaly

Official CXR Read: The heart is markedly enlarged.  No focal regions of consolidation are appreciated.  No free air is noted below the diaphragm.

Diagnosis: Ebstein anomaly complicated by severe tricuspid regurgitation and right ventricular failure

Teaching:

    • An enlarged cardiac silhouette is defined as a cardiac silhouette that is greater than half of the internal thoracic diameter. The differential for an enlarged cardiac silhouette on a chest radiograph includes cardiomegaly, pericardial effusion, and portable/AP film.
    • An enlarged right heart border with smooth contours is due to enlargement of either the right atrium, right ventricle, or both structures.
    • The right ventricle is an anterior structure. The lateral view demonstrates partial loss of the retrosternal clear space, the area between the sternum and the right ventricle. Loss of the retrosternal clear space is much more commonly due to anterior mediastinal masses.
    • The apical 4-chamber view from the patient’s echocardiogram demonstrates a significantly enlarged right ventricle as well as an enlarged right atrium.
    • Ebstein anomaly is a congenital malformation of the tricuspid valve and right ventricle.
 

Case 5: Pericardial effusion

Official CXR Read: There are diffuse bibasilar hazy opacities and prominent vasculature with a visible right minor fissure all consistent with vascular congestion.  There is also a large balloon-shaped cardiac silhouette with loss of the usual contours suggesting pericardial effusion.

Diagnosis: Uremic pericardial effusion

Teaching:

    • This patient presented after missing multiple rounds of dialysis found to have volume overload and symptomatic uremia with confusion and a large pericardial effusion.  He underwent HD with resolution of his symptoms
    • The recently normal cardiac silhouette suggests this is less likely due to cardiomegaly.
    • While the patient has a pericardial effusion, there is no concern for tamponade given he is hypertensive and not tachycardic.
 

Case 6: Mediastinal mass

Official CXR Read: Soft tissue mass in the pre-vascular (anterior) mediastinum. The lateral projection shows a loss of retrosternal clear space. The frontal projection shows a hilar overlay sign. No pulmonary vascular engorgement, no infiltrates, no nodules, and no pleural abnormalities were identified.

Diagnosis: Anterior mediastinal germ cell tumor.

Teaching:

    • Visualization of the hilar vessels through the mass, the “hilar overlay sign”, shows this mass is not involving the hilar structures.
    • Loss of retrosternal clear space suggests an anterior mediastinal process. 
    • The differential for anterior mediastinal mass: the terrible T’s (thymoma, thyroid, terrible lymphoma, and teratoma (germ cell tumors))

Presentation Board

Take Home Point

  1. From top to bottom, the normal moguls are the aortic knob, left main pulmonary artery, and left ventricle. A possible fourth mogul (between the left main PA and LV) is the left atrial appendage (not visualized in this image).
  2. “Hilar points” are the angles formed by pulmonary arteries which then taper as move peripherally.  Hilar opacities that do not taper are suggestive of hilar lymphedenopathy, not pulmonary hypertension. 
  3. Squamous cell and Small cell lung cancers are more commonly Central.  Adenocarcinomas are more commonly peripheral.2
  4. The differential for an enlarged cardiac silhouette on a chest radiograph (greater than half the internal thoracic diameter) includes cardiomegaly, pericardial effusion, and portable/AP film.
  5. Visualization of the hilar vessels through the mass, the “hilar overlay sign”, shows this mass is not involving the hilar structures.

References

  1. Goodman, L. R. (2019). Felson's Principles of Chest Roentgenology E-Book: A Programmed Text. Netherlands: Elsevier Health Sciences.
  2. Sharma, C. P., Behera, D., Aggarwal, A. N., Gupta, D., & Jindal, S. K. (2002). Radiographic patterns in lung cancer. Indian Journal of Chest Diseases and Allied Sciences44(1), 25-30.

Brandon Fainstad

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