To summarize the clinical and ultrasonographic features of neonatal appendicitis.

There were twenty-eight neonatal patients who were diagnosed as neonatal appendicitis by clinical and surgical findings in Beijing Children's Hospital, Capital Medical University, from January 2007 to October 2017. The characteristics of clinical and ultrasonographic features were summarized.

Among twenty-eight cases of neonatal appendicitis, appendix could be identified on ultrasonography in nine cases, including three cases with outer diameter less than 0.4 cm and six cases greater than 0.4 cm. And in two cases the wall of appendix was thinner than 0.2 cm, while it was thicker than 0.2 cm in seven cases. Although appendix was not identified in some cases, there were abnormal findings around the anatomical site of appendix. Ultrasonography showed that periappendicural mesentery was swelled in all twenty-eight cases and periappendicural abscess was present in twenty-six cases. Twenty-two cases of neonatal appendicitis were correctly diagnosed by ultrasonography. For the other 6 cases, four cases were necrotizing enterocolitis, one case was gaslrointestinal perforation, and one case was normal with merely abdominal distension. Among the twenty-eight cases, two cases were adhesive ileus, and two cases were complicated hydrocele of testes. On follow-up, twenty-one cases were treated conservatively, and their inflammation were controlled effectively within a month (in four cases relapsed in 5-10 months, two cases underwent another surgery while the other two cases improved after conservative treatments). Among the seven cases with surgical treatment, ultrasonography follow-up in four cases find only mild adhesion one week after surgery.

The clinical symptoms of appendicitis in neonates are highly varied. Ultrasound could identify some abnormal findings including periappendiceal mesangial swelling, enlargement of appendiceal outer diameter (≥0.4 cm), thickening of appendiceal wall (≥0.2 cm), and pyogenic/inflammatory mass. Ultrasonography can provide valuable evidences for the diagnosis and treatment in neonatal appendicitis.