What causes Rigler’s sign in the bowel on abdominal radiography?
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Rigler’s sign is caused by pneumoperitoneum, which is the presence of free gas in the peritoneal cavity. This free gas outlines both the inner (luminal) and outer (serosal) surfaces of the bowel wall, making both sides visible on plain abdominal X-rays.
Clinically, Rigler’s sign is most commonly associated with bowel perforation due to conditions such as peptic ulcer perforation, trauma, or postoperative complications that allow gas to escape into the peritoneal cavity.
Why is it called so?
The sign is named after Leo George Rigler (1896–1979), who first described it in 1941. He identified the radiologic demonstration of both the inner and outer bowel wall outlines caused by gas outlining from within and outside the bowel, and emphasized that it indicated a substantial amount of free intra-abdominal gas detectable even on supine abdominal films.
Pathophysiology
Normally, only the luminal side of gas-filled bowel walls is visible on X-rays because the surrounding soft tissues obscure the outer wall. When free gas accumulates in the peritoneal cavity (pneumoperitoneum), it collects around bowel loops. This gas surrounds the bowel walls externally, providing contrast against the soft tissues. Consequently, the bowel wall is outlined on both sides, producing a “double wall” or Rigler’s sign.
Alternative names: Double wall sign
Other associated named signs: Football sign (another radiological sign of pneumoperitoneum).
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