Acute appendicitis is one of the most common emergencies in pediatric surgery. The incidence generally increases with age from the age of 5 years, peaking at the age of 12 years, after which the incidence decreases. The course of acute appendicitis in pediatric patients progresses rapidly, and the late stage of the disease is severe and can cause purulent portal phlebitis, septic sepsis, infectious shock and even death. The younger the age, the more obvious the systemic symptoms, the diagnosis is relatively difficult, early and correct treatment is quite important. Anatomy and physiology】The appendix of pediatric patients is about 4cm~8cm long and 0.3cm~0.5cm in diameter.The appendiceal cavity of infants and children can be funnel-shaped with a large base, while in older children it is tubular and relatively elongated. The appendiceal artery is a terminal artery and has no traffic branches with the cecum blood flow, which is the anatomical basis for the susceptibility of the appendix to inflammation. The appendiceal artery is small and the appendiceal wall is thin, so once blood flow is impaired, necrosis and perforation are likely to occur; in addition, the omentum is underdeveloped in children, and the resistance to abdominal infection is poor; the peritoneum absorbs toxicity and is weak against germs, which is also the reason why abdominal inflammation in pediatric appendicitis spreads easily. [Etiology] Fecal stones in the appendix are a common cause of pediatric appendicitis. The appendiceal cavity is small and the appendix is a blind tube, which is prone to poor drainage. Bacteria from the intestinal tract can invade the appendiceal wall and cause appendicitis. Acute appendicitis can also occur when bacteria from other sites enter the appendix through the bloodstream and remain in the lymphatic tissue within the appendiceal wall. Viral infections in the upper respiratory tract and digestive tract may be a causative factor in the development of appendicitis. Pathology】Simple appendicitis, purulent appendicitis, gangrenous appendicitis. Clinical manifestations】Main symptom: right lower abdominal pain. Typical cases have metastatic right lower abdominal pain, i.e. abdominal pain starts in the upper abdomen or around the umbilicus and then shifts to the right lower abdomen after a few hours. Concomitant symptoms: nausea, vomiting, some of them have loose stools or even diarrhea, fever, and in the late stage, high fever and dehydration may appear. Physical examination: stooped and painful appearance when walking. Fixed, limited pressure pain in the right lower abdomen is the most reliable sign of pediatric acute appendicitis. Ultrasound examination: Enlarged and deformed appendix and surrounding abscesses can be detected, although ultrasound diagnosis of early appendicitis is difficult. Diagnosis and differentiation】Typical cases can be diagnosed based on medical history and clinical manifestations such as abdominal pain, right lower abdominal pressure and abdominal wall tension. Infants and young children are unable to give an accurate history and are often uncooperative, relying mainly on the physician’s objective examination. Early appendicitis is sometimes not easy to diagnose and should be distinguished from the following diseases: acute mesenteric lymphadenitis, allergic purpura, acute gastroenteritis, intestinal ascariasis, right ureteral calculus, ovarian cyst torsion, acute necrotizing enterocolitis, etc. 【Treatment principle】The treatment principle of pediatric acute appendicitis is: early surgery to remove the appendix to avoid the spread of infection. Late appendicitis surgery often cannot eliminate the lesion and can destroy the formed adhesions, allowing the infection to spread, so non-surgical treatment is mostly used. If the appendix has become a limited periappendiceal abscess and the symptoms are not reduced by anti-inflammatory treatment, the abscess can be drained by incision and the appendix can be removed at a later stage after it has healed. In clinical practice, many children and parents do not accept surgery at first, and then ask for surgery when the inflammation spreads and cannot be controlled by medication, which often misses the best time for surgery. The best time for surgery is often missed. At this time, surgery is risky and has many complications; continued anti-inflammatory treatment will have a longer course, and appendicitis may still develop in the future. Postoperative treatment] Surgery is only part of the treatment of acute appendicitis in children. Post-operative anti-inflammatory therapy should be intensified, usually combined with the application of two to three antibacterial drugs intravenous drip. The postoperative position should be semi-recumbent to facilitate the drainage of inflammatory exudate from the abdominal cavity to the pelvic floor. The child should be encouraged to move out of bed more often to facilitate early recovery of intestinal function.