The four clinical pathological types of appendicitis are acute simple appendicitis, acute suppurative appendicitis, gangrenous and perforated appendicitis, and periappendiceal abscess. Usually, acute simple appendicitis is a mild form of appendicitis in which the lesions are confined to the mucosa and submucosa, and the clinical symptoms and signs are generally mild. gangrenous and perforated appendicitis is a heavy appendicitis in which the wall of the appendix is necrotic and perforated, and the spread of inflammation can cause acute diffuse peritonitis in patients; periappendiceal abscess is an inflammatory mass formed when the greater omentum moves to the right lower abdomen, wrapping the appendix and forming adhesions.