UMEM Educational Pearls

Category: Trauma

Title: What's wrong with this picture? By John Greenwood, MD

Keywords: Apical cap, dissection, blunt aortic injury, chest xray, radiology (PubMed Search)

Posted: 1/31/2011 by Haney Mallemat, MD
Click here to contact Haney Mallemat, MD


44 y/o female restrained driver s/p motor vehicle crash complaining of chest pain and shortness of breath. 


Answer: Left pleural apical cap.


The Apical Cap

An apical cap is a unilateral or bilateral irregular density over the apex of the lung, generally less than 5mm. The lower border is often sharp but undulating. 

Differential diagnosis:

  • Trauma: Blunt aortic injury (BAI) or dissection
  • Inflammatory: TB or extra-pleural neck abscess
  • Post-radiation fibrosis
  • Neoplasm
  • Vascular abnormalities: e.g.,aortic coarctation with dilated collateral vessels
  • Non-specific (most common): Subpleural thickening, scarring, or other diseases;  especially common in elderly. 


Fabian TC, Richardson JD, Smith JS Jr, et al. Prospective study of blunt aortic injury: multi-center trial of the American Association for the Surgery of Trauma. J Trauma 1997;42:374-383.

McLoud TC, Isler RJ, Novelline RA, et al.  The apical cap.  Amer J Rad 1981; 137:299-306.

Rivas LA, Fishman JE, Munera F, et al.  Multislice CT in thoracic trauma.  Radiol Clin North Am2003; 41:599-616.