What causes Doughnut sign in bowel on cross-sectional imaging?
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Answer:
Ring-shaped thickening of the bowel wall with central lucency seen in intussusception, where telescoping of proximal bowel (intussusceptum) into distal bowel (intussuscipiens) creates layered appearance, or in annular masses causing circumferential narrowing; also manifests as small-bowel wall target sign on ultrasound. (Also described as the Doughnut sign on cross-sectional imaging.)
Why is it called so?:
Named for the resemblance to a doughnut, with peripheral ring of thickened edematous bowel wall and central lucency representing compressed intraluminal fat or mesenteric vessels.
Pathophysiology:
In intussusception, peristalsis drives the intussusceptum into the intussuscipiens, causing bowel wall edema and mesenteric fat trapping in the center, producing a targetoid configuration with hyperechoic center on ultrasound or central lucency on CT; annular masses like carcinoma produce similar ring thickening via circumferential infiltration.
Alternative names: Target sign, bull’s eye sign
Other associated named signs: Crescent-in-doughnut sign
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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