<prompt> Sensitive most investigation to detect minimal intraperitoneal free airStanding x-ray abdomenRight lateral decubitus x-rayChest x-rayLeft lateral decubitus x-ray  <response>: Although as little as 1 ml of free gas can be demonstrated radiographically, either in chest PA or a left lateral decubitus abdominal film, CT is superior to plain radiographs in detecting minute quantities of pneumoperitoneum. Chest PA view is more sensitive than even a left lateral decubitus abdominal film. 