What does the presence of Rigler sign on radiography indicate?

The presence of the Rigler sign on radiography indicates the existence of free air in the abdominal cavity, which typically suggests a perforation in a hollow viscera, most commonly due to a perforated duodenal ulcer. The Rigler sign is characterized by the visibility of both the inner and outer walls of the intestine due to air trapped between the two layers, indicating that air has escaped from the gastrointestinal tract into the peritoneal cavity.

While other conditions such as appendicitis and inflammatory bowel disease may result in abnormal radiographic findings, they do not typically present with the Rigler sign. Instead, these conditions have different clinical and radiographic features that do not involve the clear identification of free air within the peritoneal cavity. Overall, the specific radiographic manifestation of the Rigler sign is highly suggestive of a perforated duodenal ulcer, confirming significant gastrointestinal pathology requiring urgent intervention.