P sign

Last revised by Dr Daniel J Bell on 02 Apr 2021

The alphabet P sign, or just P sign, is a sonographic finding in acute epiglottitis. Using point of care ultrasound (POCUS), on a longitudinal view at the level of the thyrohyoid membrane, a P-shaped hypoechogenicity is apparent. The curved portion of the P is formed from the edematous epiglottis, whilst the straight part of the P is acoustic shadowing posterior to the hyoid bone.

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