What can abdominal plain film detect?

Standing abdominal plain film can roughly understand the situation in abdominal cavity and has diagnostic significance for some specific diseases. For example, the "crescent-shaped" free air shadow on both sides of the diaphragm often indicates perforation of the upper digestive tract, and multiple liquid-air planes indicate intestinal obstruction. Even if the swallowed foreign body is a metal and other objects that cannot be penetrated by X-rays, it can be developed and some ureteral stones can be observed.