Apple core sign (colon)

Last revised by Daniel J Bell on 24 Feb 2024

The apple core sign, also known as the napkin ring sign (bowel), is most frequently associated with constriction of the lumen of the colon by a stenosing annular colorectal carcinoma.

It is not to be confused with the napkin ring sign of vulnerable coronary artery plaque or the apple core sign of the femur.

Differential diagnosis

The appearance of the apple core lesion of the colon also can be caused by other diseases 3:

History and etymology

The pioneering American GI radiologist Russell Carman (1875-1926) used the term napkin ring sign in a publication on imaging signs of the GI tract 4.

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