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, recent instrumentation or surgery. A false double wall sign can result from two loops of bowel being in contact with one another.
History and etymology
It is named after Leo George Rigler (1896-1979), American radiologist 2.