Appendicitis is the most common disease in pediatric abdominal surgery and ranks first among pediatric acute abdominal conditions. Appendicitis can occur in all age groups, with a peak incidence of 6-10 years of age and a significant decrease below 5 years of age, with only 1% of cases less than 1 year of age and rare in neonates. The incidence is slightly higher in males than in females. Pediatric appendicitis is divided into three types according to its pathological changes: simple, septic, and gangrenous. There are five stages according to the progress of the disease, namely simple, limited peritonitis, diffuse peritonitis, infiltrative and abscess formation. (1) Clinical manifestations (1) Abdominal pain In elderly people, the pain is initially epigastric pain or periumbilical pain, and after a few hours of onset, the pain shifts and is fixed in the right lower abdomen. After the appendix perforation causes diffuse peritonitis, there is persistent pain throughout the abdomen. Infants and young children are incapable of expressing changes in pain and show abdominal pain by crying and restlessness, curling up and not moving, and refusing to be patted or shaken. Neonatal appendicitis can be induced by distal colonic obstruction (e.g., congenital megacolon) and is prone to early perforation. 2. Vomiting appears 5-6 hours after the onset of abdominal pain, and the vomit is the stomach contents, not many times, and frequent vomiting is rare. In infants and children, vomiting appears earlier and can even occur before abdominal pain. In older children, nausea and anorexia are the main causes, and vomiting is relatively uncommon. 3. fever Progressive fever starts a few hours after abdominal pain, and the younger the child, the more obvious the increase in temperature, and the high fever may persist after perforation. 4.Diarrhea When appendiceal perforation is complicated by peritonitis, pelvic abscess formation, and the appendix is located in the pelvic cavity, diarrhea can occur when the rectum and sigmoid colon are stimulated by inflammatory exudate, and diarrhea is characterized by frequent and small amount of mucus stool with frequent urination in some children. 5, abdominal signs right lower abdomen fixed pressure pain is a reliable basis for the diagnosis of appendicitis, wall peritoneum stimulation can appear local muscle tension and rebound pain. 6, rectal examination The anterior rectal wall is edematous, hypertrophic, and the right wall is painful to palpation. In the pelvic position of the appendix, the right anterior wall of the rectum is thickened, and even the swollen appendix in the form of cords can be palpated. In the case of periappendiceal infiltration or abscess formation, it is supplemented by double coaptation of the inflammatory masses palpated in the pelvis. (B) Ancillary tests 1. Routine blood tests Increased total white blood cells and increased central granulocytes. 2.Laparotomy The puncture fluid may be purulent, with leukocytes or pus cells on microscopic examination and E. coli on smear. 3.Ultrasound examination The normal appendix or the early stage of the lesion is not shaped, the appendix of septic change is hypoechoic tubular structure, its cross-section shows concentric circle-like target-like shadow, the diameter of the appendix is ≥6mm, there is a limited fluid around the appendix, and strong echogenic fecal stone is visible in the appendix lumen. In case of periappendiceal infiltration or appendiceal abscess formation, well-defined or poorly defined masses with uneven, non-echoic, hypoechoic or moderate internal echogenicity were detected. 4.X-ray examination X-ray standing abdominal plain film is not specific for the diagnosis of appendicitis, but certain indirect signs have some reference significance, such as disappearance of the right peritoneal fatty line; localized intestinal paralysis in the right iliac fossa; appendix perforation to a small amount of free gas under the diaphragm; calcified fecal stone shadow. Barium enema is helpful in the diagnosis of chronic appendicitis in older children and is used sparingly in clinical practice. Common positive findings are compressive defect of the cecum, non-filling of the appendix and irritation and spasm of the terminal ileum. 5, laparoscopy Through laparoscopy can directly observe the presence of inflammation of the appendix, but also distinguish other diseases adjacent to appendicitis with similar symptoms, which can play a decisive role in determining the diagnosis. If it is appendicitis, resection will be performed at the same time. (a) Surgical treatment Regardless of the type of pediatric acute appendicitis, in principle, early appendectomy should be performed. The common procedure is still the traditional open appendectomy, but laparoscopic appendectomy can also be used for obese children, girls, those with limited inflammation, and those with unclear diagnosis. (B) Antibiotic treatment The causative organisms of appendicitis are mostly a mixture of aerobic and anaerobic bacteria. The combination of ampicillin, gentamicin and metronidazole is used in early appendicitis, and the combination of cephalexin and metronidazole is used in late or perforated appendicitis. Normal body temperature and declining white blood cells can be switched to oral antibiotics. (iii) Treatment of infiltrative and abscess appendicitis The course of the disease is more than 3 days in older children, more than 5 days in infants and children, without peritonitis, with limited lesions and palpable abdominal masses, should be treated conservatively and actively anti-infective. Abscess formation can be treated with ultrasound-guided puncture and pus aspiration, and if necessary, surgical incision and drainage. Appendectomy can be performed at an optional stage 3-6 months after the inflammation subsides.