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Crescent in a doughnut sign

Dr Yuranga Weerakkody and Dr Frank Gaillard et al.

The crescent in a doughnut sign refers to the transverse ultrasound appearance of intestinal intussusception, and is a variation of the target sign (which is also known as the doughnut sign)

The doughnut is formed by concentric alternating echogenic and hypoechogenic bands. The echogenic bands are formed by mucosa and muscularis whereas the submucosa is responsible for the hypoechoic bands.

The crescent is formed by mesentary which is dragged into the intussusception. It is naturally located only on one side of the bowel and therefore forms a crescent which is echogenic.

It is thus the transverse equivalent of the pseudokidney sign.

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References

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1. Del-pozo G, Albillos JC, Tejedor D. Intussusception: US findings with pathologic correlation--the crescent-in-doughnut sign. Radiology. 1996;199 (3): 688-92. Radiology (citation) - Pubmed citation