Bowler hat sign is seen in
BOWLER HAT SIGN: Cup shaped filled defect seen on air contrast barium enema that represents POLYP if it points towards lumen. The "bowler-hat sign" represents the appearance of a sessile colonic polyp observed at an oblique angle on a double contrast barium enema. The bowler-hat sign is formed by a ring of barium adjacent to the base of the polyp surrounding a domed layer of barium coating the surface of the polyp.
Sigmoid volvulus
Midgut volvulus
Intussusception
Sessile colonic polyp
Gastrointestinal Radiology