Under normal circumstances after abdominal exercise, abdominal stiffness can occur after abdominal exertion, which is a normal phenomenon. If the patient is sick, the pathological state of abdominal stiffness is considered to be a platysmal abdomen, which is a symptom of acute diffuse peritonitis. It is common to see diffuse inflammation in the abdominal cavity due to perforation of the upper gastrointestinal tract, such as gastric or duodenal perforation, and perforation of the appendix. When diffuse inflammation occurs, gastric juice, intestinal juice and pus in the abdominal cavity penetrate into the abdominal cavity, resulting in inflammation and infection of the peritoneal wall, which manifests as abdominal pain, a plate-like abdomen, and a hard abdomen when the abdomen is pressed by hand, and the patient does not give pressure, an abdominal CT examination can be performed, which can reveal free gas in the abdominal cavity. In the case of appendicitis, swelling of the appendix with a large amount of exudation around it can be found. When there is perforation of the upper gastrointestinal tract, laparoscopic or open surgery is required to repair the perforation. In the case of appendicitis, the appendix will need to be removed and abdominal drainage will be done.