Rigler's sign, also known as the double wall sign, is seen on an x-ray of the abdomen when air is present on both sides of the intestine; a Rigler's sign is present when air is present on the inside (lumenal side) and the outside (peritoneal side). Air in the peritoneum is considered abnormal, unless the patient had a recent abdominal surgery.
A false double wall sign can result from two loops of bowel being in contact with one another.
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