Localized perforation occurs when the periappendiceal infection of appendix becomes walled off by omentum and adjacent viscera. The clinical presentation consists of the usual findings in appendicitis plus a right lower quadrant mass. An ultrasound or CT scan should be performed; if an abscess is found, it is best treated by percutaneous ultrasound-guided aspiration. Opinion differs about how small abscesses and phlegmons should be handled. Some surgeons prefer a regimen consisting of antibiotics and expectant management followed by elective appendectomy 6 weeks later. The purpose is to avoid spreading the localized infection, which usually resolves in response to the antibiotics. Other surgeons recommend immediate appendectomy, which some believe shortens the duration of the illness. However, the immediate surgery approach has significant complications in a higher percentage of patients. There is not currently a consensus.