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.
When the surgeon encounters an unsuspected abscess during appendectomy, it is usually best to proceed and remove the appendix. If the abscess is large and further dissection would be hazardous, drainage alone is appropriate.
Appendicitis recurs in only 10% of patients whose initial treatment consisted of antibiotics or antibiotics plus drainage of an abscess. Therefore, when the presence of ancillary conditions increases the risks of surgery, interval appendectomy may be postponed unless symptoms recur.