Sometimes the best lessons in life are the simple ones.

The learning points from this case are:

1.  Always interrogate the film characteristics - the projection is important to find the pathology

2.  Patients are always served better when clinicoradiological discussion takes place

3.  Even with advanced imaging modalities plain radiographs are still important and interesting

Pneumoperitoneum is more easily identified on the erect CXR, than the AXR, but a number of signs of free gas on AXR have been described.

These include:  the falciform ligament sign, triangles of gas, the football sign, inverted V sign and 'right upper quadrant gas sign'.