Free Air

Free air is due to perforation of a hollow viscus. The most common cause is a peptic ulcer, however it is only evident in 70-80% cases. Air can persist after a laparoscopy for up to 28 days.

The erect chest x-ray is the most appropriate investigation for this but requires the patient to sit up for 5-10 minutes. On the supine abdominal film visibility of both sides of the bowel wall, outlined by free air – Rigler’s sign – may be present. Alternatively, a left lateral decubitus film may demonstrate air rising up to the right flank.

Fig.1 Erect CXR PA view – Shows Air under the right side Diaphragm

Fig.2 Erect CXR AP view – Shows Air under the bilateral Diaphragm 

Fig.3 AXR shows double wall (rigler sign)

Fig.4 Lateral decubitus view showing free Air