Acute appendicitis can be classified into four types based on the clinical course. The first type is acute simple appendicitis, where the lesions are mostly confined to the mucosa and submucosal layer, with small ulcers and bleeding spots on the mucosal surface. The symptoms and signs are relatively mild. The second type is acute suppurative appendicitis, where the lesion has spread through all the layers of the appendix wall, and pus may accumulate inside, also known as acute cellulitis appendicitis. The third type is gangrenous and perforated appendicitis, which occurs due to pus in the appendix cavity causing increased internal pressure and circulatory disturbances in the appendix wall, leading to mucosal ischemic necrosis and perforation, causing acute diffuse peritonitis. The fourth type is peri-appendiceal abscess, which forms an inflammatory mass encapsulated by the surrounding omentum during suppuration or perforation of acute appendicitis.