Radiological confirmation of intraperitoneal free gas.

Although subdiaphragmatic gas on an erect chest or abdominal radiograph usually indicates the presence of a gastrointestinal perforation, this sign is present in only 60-80% of cases. Other less well known radiographic signs of perforation that may nonetheless be of utmost importance in diagnosis are described. The presence of such signs may then prompt further diagnostic procedures or surgical intervention as appropriate.