Rigler sign: a subtle finding of pneumoperitoneum.

A 75-year-old woman with a past medical history of hypertension, presented to the emergency department (ED) with 12 h of persistent, non-radiating, diffuse abdominal pain. The patient had undergone a colonoscopy the day before. A chest X-ray study was done in the ED after the patient was sitting upright for at least 10 min, but shows no free air under the diaphragm (Fig. 1). The abdominal X-ray (Fig. 2) shows air both on the inside and outside of the bowel wall consistent with free air, also known as the Rigler sign [1]. Additionally, there is a great amount of parahepatic air, outlining the lower liver edge. The Surgery service was consulted immediately for a possible bowel perforation, and the patient was taken to the operating room. Exploratory laparotomy revealed a perforated sigmoid colon. The patient underwent sigmoid colon resection, bowel re-anastomosis, and had an uncomplicated hospital course. She was discharged home in good condition.