A. Double bubble sign.
B. Triple bubble sign.
C. Rigler sign.
D. Blumberg sign.
The sign marked by a red arrow as shown in the photograph above represents Rigler sign.
The Rigler sign, also known as the double wall sign, is seen on a radiograph of the abdomen when the air is present on both sides of the intestine, i.e. when there is air on both the luminal and peritoneal side of the bowel wall.
Pneumoperitoneum may be a result of perforation or, from recent instrumentation or surgery. A false double wall sign can result from two loops of bowel being in contact with one another.
Rigler sign should not be confused with the Rigler triad, the Rigler notch sign, orHoffman- Rigler sign.