What causes Bowler hat sign in colon on double-contrast barium enema?
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Answer:
Bowler hat sign: Biconvex filling defect representing a small sessile colonic polyp or lipoma seen en face, associated with colonic polyps that are intermediate between flat plaque and pedunculated growth.
Why is it called so?:
Resembles the rounded dome and brim of a traditional bowler hat due to the biconvex shape of the filling defect with barium coating the edges.
Pathophysiology:
In double-contrast barium enema, a small sessile polyp or lipoma projects into the lumen and is viewed en face, creating a central area of trapped barium surrounded by a biconvex rim of non-opacified mucosa resembling a Bowler hat sign; barium coats the polyp margins without fully outlining a stalk as in pedunculated lesions.
Alternative names: None
Other associated named signs: Mexican hat sign (pedunculated colonic polyp)
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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