Pleural Effusion – CXR

Table of Contents

Table of Contents

Published February 2021

Samantha King, MD
Daniel Gergen, MD
Expert review – pending


  1. Identify a pleural effusion on chest x ray using the meniscus sign

  2. Identify distal tracheal deviation as a sign of volume loss

Teaching Instructions

Plan to spend 5-10 minutes familiarizing yourself with the animations of the PowerPoint and the key findings of this chest x-ray.

Present the image either by expanding the window (bottom right) in a browser or downloading the PowerPoint file (downloading is recommended).  Have the image pulled up in presenter mode before learners look at the screen to avoid revealing the diagnosis.  Ask a learner to provide an overall interpretation.  Then advance through the animations to prompt learners with key questions and reveal the findings, diagnosis, and teaching points.

Instructions: Ask a leaner to provide an overall interpretation.  Advance using the arrows or scroll wheel on the mouse reveal subsequent questions with answers and graphics.  You can go back to prior graphics and questions by using the back arrow or scrolling back on the mouse wheel. 

Official CXR Read: There is a moderate sized pleural effusion with adjacent consolidation, likely compressive atelectasis. The distal trachea is slightly deviated to the right. The lungs are otherwise clear without consolidation, effusion or pneumothorax. Right heart border is silhouetted by the effusion

Diagnosis: Malignant moderate right pleural effusion with associated compressive atelectasis

Teaching: A pleural effusion can manifest on  chest x-ray s blunting of the costophrenic angle. Larger free flowing effusions may have  meniscus sign – the lung opacity has  well delineated concave upward interface.  

Larger effusions can result in tracheal and mediastinal displacement. Massive effusions that result in the complete opacification of the hemithorax results in displacement of the mediastinum AWAY from the effusion. Atelectasis result in tracheal deviation TOWARDS the side of the opacity. With moderate and large effusions, there is a component of compressive atelectasis. The ultimate direction of mediastinal shift is determined by relative degree of atelectasis and effusion. 

Presentation Board

Take Home Points

  1. Moderate to large effusions can manifest as “meniscus sign”
  2. Very large effusions can cause tracheal deviation away from the side of the effusion. However, moderate-sized effusions can cause collapse of adjacent lung parenchyma


Guo L & Ackman JB.  “The Pleural, Diaphragm, and Chest Wall.” Thoracic Imaging: The Requisites Third edition. Edited by Shepard JO. Elsevier, 2019, pp. 159-192.

Yilin Zhang


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