Rebound pain indicates a sign of peritonitis, mostly seen in lesions caused by acute diffuse peritonitis or appendicitis. When there is inflammation in the abdominal cavity, the inflammatory cells invade the peritoneal wall layer, causing inflammation in the peritoneal wall layer, and when the hand is pressed on the most obvious place of pain, the patient will experience abdominal pain, and when the hand is suddenly lifted, the patient feels abdominal pain again, and this pain is called rebound pain. When rebound pain occurs, it means that the inflammation in the abdominal cavity has become very serious and has spread to the peritoneal wall layer, which routinely requires surgery for treatment, such as surgery to remove the appendix if the rebound pain is caused by appendicitis, or surgery to repair the perforation if the rebound pain is caused by diffuse peritonitis or perforation of the digestive tract.