When serious infection occurs in the abdominal cavity and severe acute inflammation occurs, the stomach is hard, full stomach pressure pain, rebound pain, and the stomach is hard like a plank, called plank abdomen. The symptoms are mainly severe abdominal pain, full abdominal pressure and rebound pain, high fever, chills, and shock manifestations such as oliguria, thirst, and even depression. The common causes of acute diffuse peritonitis are acute gastroduodenal ulcer perforation, perforation of other parts of the digestive tract, severe acute pancreatitis, acute gangrenous appendicitis or cholecystitis.