The Rigler sign, also known as the double-wall sign, is a sign of pneumoperitoneum seen on an abdominal radiograph when gas is outlining both sides of the bowel wall, i.e. gas within the bowel's lumen and gas within the peritoneal cavity. It is seen with large amounts of pneumoperitoneum (>1000 mL).
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, thus the wall thickness is double that of a single loop.
History and etymology
It is named after Leo George Rigler (1896-1979), American radiologist .