Citation, DOI, disclosures and article data
At the time the article was created Matt Skalski had no recorded disclosures.View Matt Skalski's current disclosures
At the time the article was last revised Frank Gaillard had the following disclosures:
- Biogen Australia Pty Ltd, Investigator-Initiated Research Grant for CAD software in multiple sclerosis: finished Oct 2021 (past)
These were assessed during peer review and were determined to not be relevant to the changes that were made.View Frank Gaillard's current disclosures
The extrapleural sign refers to the appearance of a pulmonary opacity with oblique margins that taper slowly to the chest wall when the lesion is viewed tangentially to the x-ray beam. This appearance suggests that the lesion is pleural or extrapleural in nature, as opposed to intrapulmonary where an acute angle would be expected as the lesion meets the lung periphery. This term may be confused with extrapleural air sign which refers to a different finding.
The appearance has also been referred to as the snowball sign 4. The analogy for an intrapulmonary mass is a thrown snowball just prior to impact with the (chest) wall, which maintains an acute angle. The pleural or extrapleural mass corresponds to the snowball after impact with the wall, which is flattened and makes obtuse angles with the wall.
History and etymology
The extrapleural sign was described by Ben Felson in 1973 1.
- 1. Felson B. Chest roentgenology. W.B. Saunders Company. ISBN:0721635911. Read it at Google Books - Find it at Amazon
- 2. Principles and Interpretation of Chest X-rays. Orient Longman Limited. (2007) ISBN:8125030069. Read it at Google Books - Find it at Amazon
- 3. Shields TW, LoCicero J, Reed CE et-al. General Thoracic Surgery. Lippincott Williams & Wilkins. (2011) ISBN:1451152787. Read it at Google Books - Find it at Amazon
- 4. Ouellette, H, Tetreault P. Clinical Radiology Made Ridiculously Simple. 2nd edition. MedMaster. (2015) ISBN:0940780755.