History: abdominal pain.
Name the sign and what it means.
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Rigler's sign of pneumoperitoneum
Rigler's sign = "double bowel wall sign". Seen with pneumoperitoneum (free air).
Remember, what you see on X-rays is based on changes of densities rather than the denisty itself.
- No air in the bowel = you don't see the bowel
- intraluminal air = you see the inner mucosal wall
- extra-luminal air = you see the outer serosal wall
So when air inside + air outside means you see both the inner mucosal and outer serosal walls = double bowel wall sign!