Ultrasound and computerized tomography (CT) may provide additional information.

Acute appendicitis is the most common cause of emergency abdominal surgery in children. It occurs throughout childhood but is most common during the second decade of life. Appendicitis occurs infrequently in children younger than 2 years of age. Diagnosis and surgical intervention before perforation is the most important determinant of a good clinical outcome.

Appendicitis develops when the lumen of the appendix is obstructed by a fecalith, food, lymphoid tissue, or tumor. Obstruction leads to bacterial overgrowth and inflammation of the appendiceal wall. Perforation is common after 48 hours and very common after 72 hours. Rupture of the appendix is followed in most instances by generalized peritonitis from contamination with fecal bacterial flora.

Presenting symptoms vary with age. Early diagnosis is especially difficult in children who are younger than 4 years of age. For many reasons, the appendix may already be ruptured at the time most infants and toddlers present for care. These young children may not be able to complain of pain and often present with symptoms suggestive of acute gastroenteritis, such as vomiting and irritability. In addition, the disease may evolve more quickly in this age group. Children of preschool and school age typically present with fever, abdominal pain, and vomiting. Anorexia is almost always present. Older school-aged children and teenagers are more likely to localize their pain to the right lower quadrant.