Standing on the abdominal plain film, you can see the shadow of free gas under the diaphragm, and the first consideration is ().

Gastrointestinal perforation is the most common perforation of stomach or duodenum, which is caused by ulcer penetrating the gastrointestinal wall and reaching the free abdominal cavity, leading to acute diffuse peritonitis. The patient suddenly developed persistent and severe upper abdominal pain, which quickly spread to the whole abdomen with shock. Physical examination: Abdominal tenderness, rebound pain, plate abdomen, dullness boundary of liver narrowed or disappeared, bowel sounds weakened or disappeared. Peripheral blood leukocytes and neutrophils increased, and vertical X-ray fluoroscopy showed arc or half-moon transparent gas shadows on both sides of diaphragm.