Continuous diaphragm sign


Normally the central portion of the diaphragm is not discretely visualized on chest radiographs as it merges with the cardiac silhouette. If the diaphragm can be seen continuously across the midline then this is highly suggestive of free gas within the upper abdomen as beautifully illustrated in this case.

This is termed the continuous diaphragm sign and is one of several plain radiograph appearances in pneumoperitoneum.