It is not always particularly painful to suffer from appendicitis. The pain of appendicitis is mainly caused by the following factors: a. The appendix is often blocked by fecaliths or hyperplastic lymphoid follicles. The fluid secreted by the appendix itself increases the pressure in the appendiceal cavity. If the pressure is high, the pain will be severe, and if the pressure is low, the pain will be mild. When the pressure is too high, the appendix will be perforated, and then the patient will change from very painful to less painful, but after some time, the pus, fecal stone and intestinal fluid will irritate the abdominal cavity and the abdominal wall, and the pain will be aggravated again. Secondly, when suffering from appendicitis, as there will be purulent fluid or inflammatory fluid in the periphery, these fluids will irritate the peritoneum and abdominal wall muscles and cause pain. If the omentum and intestinal tubes wrap the appendix, the fluid can’t come out so it can’t be stimulated and the pain will be mild. This is the reason why periappendiceal abscesses are heavily infected, but the pain is mild instead.