What are the imaging features of right middle lobe (RML) collapse in patients with atelectasis?

Updated: Oct 22, 2020
  • Author: Tarun Madappa, MD, MPH; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Answer

Right middle lobe (RML) collapse (see images below) obscures the right heart border on a posteroanterior (PA) film. Occasionally, a triangular opacity may be observed. The lateral view demonstrates a triangular opacity overlying the heart because the major fissure shifts upward and the minor fissure shifts downward. Upon CT scanning, the atelectatic RML appears as a triangular opacity against the right heart border with the apex pointing laterally and is termed the "tilted ice cream cone sign."

Atelectasis. A lateral chest x-ray film confirms t Atelectasis. A lateral chest x-ray film confirms the diagnosis of right middle lobe collapse. The minor fissure moves down, and the major fissure moves up, leading to a wedge-shaped opacity.
Atelectasis. Left lower lobe collapse. Atelectasis. Left lower lobe collapse.
Atelectasis. Right middle lobe collapse showing ob Atelectasis. Right middle lobe collapse showing obliteration of the right heart border.
Atelectasis. Right middle lobe collapse on a later Atelectasis. Right middle lobe collapse on a lateral chest x-ray film.

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