Discrete Lung Opacites – CXR

Table of Contents

Table of Contents

June 2023

Daniel Gergen, MD1, Samantha King, 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: Lower Lobe Pneumonia

Official CXR Read: Normal cardio-mediastinal silhouette. Left greater than right basilar opacities. No definite pleural effusion. No visible pneumothorax. No visible acute displaced fracture.

Diagnosis: Left lower lobe pneumonia

Teaching

    • The most common causes of a lobar consolidation on chest x ray are bacterial pneumonia, followed by lobar collapse. Air bronchograms (not seen here) can help identify an alveolar filling process whereas signs of volume loss (not seen here) can help identify lobar atelectasis.
    • The vertebral bodies should become more radiolucent (black) as you move down the spine on a lateral chest x-ray. This is due to the presence of more air in the lower thorax as compared to the upper, as the lungs occupy more space inferiorly.
    • Increased soft tissue density (white) as you move down the spine is indicative of a pathologic process, typically a basilar consolidation or pleural effusion.

Case 2: RUL Cavitary Lesion

Official CXR Read: Interval development of sub-pleural mass-like consolidative opacity in the anterior and posterior segments of the right upper lobe. Findings are suspicious for infectious pneumonitis but may also represent malignancy.

Diagnosis: Right upper lobe bacterial pneumonia complicated by abscess formation

Teaching

    • The most common cause of a lobar consolidation on chest x ray is bacterial pneumonia
    • Consolidation surrounding a cavitary lesion in a patient with acute infectious symptoms is most concerning for pneumonia with abscess formation
    • The minor fissure separates the right upper lobe from the middle and lower lobes (there is no minor fissure on the left as there is no left middle lobe)
 

Case 3: LUL Cavitary Lesion 

Official CXR Read: Rounded thick-walled cavity in the left upper lobe surrounded by interstitial markings and ground-glass opacities.

Diagnosis: Left upper lobe bacterial pneumonia complicated by abscess formation.

Teaching

    • A thick-walled cavity with surrounding alveolar opacities in a patient with systemic inflammatory symptoms is suspicious for lung abscess or necrotic pneumonia
    • It is valuable to identify the pathogen in lung abscesses to offer more targeted prolonged antibiotics. 
 

Case 4: Lung metastases

Official CXR Read: Numerous bilateral basilar predominant, well-defined pulmonary nodules, concerning for metastases. Large right pleural effusion.

Diagnosis: Diffusely metastatic neuroendocrine tumor from an unknown primary.

Teaching:

    • Lung metastases are typically well-defined, and distributed toward the bases and the periphery reflecting hematogenous spread.
    • Primary lung cancer nodules tend to have ill-defined spiculated margins and are often located centrally or apically.
 

Case 5: Retrocardiac opacity

Official CXR Read:There is an opacity in the left lung base that obscures the normal lung markings (compare it to the right lung base where branching vessels are well visualized). The opacity also obscures/silhouettes the left hemidiaphragm, which localizes this abnormality to the left lower lobe. Conversely, the left heart border is still visible, so we know that it's not in the lingula.

On the lateral projection, you see a “spine sign”. The vertebral bodies should get more lucent (g. darker) as you follow the spine inferiorly.  However, in this case, we see an opacity projecting over the low thoracic spine, which confirms that the opacity is in the left lower lobe.

Diagnosis: Left lower lobe bacterial pneumonia

Teaching:

    • Retrocardiac left lower lobe densities can be identified by noting the obscuration of lung markings and a loss of the left diaphragm silhouette.
    • Sputum and blood cultures are not indicated in CAP that is managed outpatient, not severe, and no known risks for MRSA or pseudomonas.
    • Patients with chronic organ dysfunction diagnosed with CAP and managed as an outpatient should receive broader antibiotic coverage.
 

Case 6: Peripheral nodule

Official CXR Read: AP portable upright expiratory chest radiograph with hazy opacity in the lateral right mid-lung surrounding a peripheral nodule.

Diagnosis: Peripheral mid-right lung opacity concerning for infection or malignancy.

TeachingDiscrete lung opacities that are not likely explained by reversible infectious process, based on clinical clinical, context, should be further evaluated with repeat imaging or advanced imaging. 

Presentation Board

Take Home Point

  1. The most common causes of a lobar opacity on chest x ray are bacterial pneumonia (suggested by air-bronchograms), followed by lobar collapse (suggested by ipsilateral volume loss).
  2. Increased soft tissue density (white) as you move down the spine is indicative of a pathologic process, typically a basilar consolidation or pleural effusion.
  3. A thick-walled cavity with surrounding alveolar opacities in a patient with acute infectious symptoms is most concerning for necrotizing pneumonia or lung abscess.
  4. Lung metastases are typically well-defined, and distributed toward the bases and the periphery reflecting hematogenous spread.
  5. Sputum and blood cultures are not indicated in CAP that is managed outpatient, not severe, and no known risks for MRSA or pseudomonas.
  6. Patients with chronic organ dysfunction diagnosed with CAP and managed as an outpatient should receive broader antibiotic coverage.
  7. Discrete lung opacities that are not likely explained by reversible infectious process, based on clinical clinical, context, should be further evaluated with repeat imaging or advanced imaging. 
  8. CT-guided biopsy is best for accessing peripheral lesions.  Bronchoscopy is best for central lesions.
  9. Emphysema increases the risk of post-biopsy pneumothorax.

References

  1. Goodman, L. R. (2019). Felson's Principles of Chest Roentgenology E-Book: A Programmed Text. Netherlands: Elsevier Health Sciences.
  2. Gafoor K, Patel S, Girvin F, Gupta N, Naidich D, Machnicki S, Brown KK, Mehta A, Husta B, Ryu JH, Sarosi GA, Franquet T, Verschakelen J, Johkoh T, Travis W, Raoof S. Cavitary Lung Diseases: A Clinical-Radiologic Algorithmic Approach. Chest. 2018 Jun;153(6):1443-1465. doi: 10.1016/j.chest.2018.02.026. Epub 2018 Mar 6. PMID: 29518379.

Brandon Fainstad

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