What causes Target sign in bowel on US/CT?
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Answer:
Concentric ring or Target sign/target-like appearance due to intussusception, where a proximal bowel segment (intussusceptum) invaginates into the distal segment (intussuscipiens), commonly ileocolic in children presenting with intermittent abdominal pain, vomiting, and currant jelly stool; also seen with target-like lymphoma deposits.
Why is it called so?
Named for the multilayered concentric rings resembling a target or bull’s eye, formed by alternating echogenic and hypoechoic layers on ultrasound or ring-enhancing appearance on CT.
Pathophysiology
Intussusception causes the intussusceptum to telescope into the intussuscipiens, drawing in mesenteric fat and vessels; on transverse imaging, this produces central hypoechoic edematous bowel wall surrounded by hyperechoic mesentery/serosa and outer hypoechoic muscularis/submucosa layers.
Alternative names: Doughnut sign, bull’s eye sign
Other associated named signs: Pseudokidney sign (longitudinal view), crescent sign (mesentery on plain film)
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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