An evidence-based definition for perforated appendicitis derived from a prospective randomized trial

Purpose

Appendicitis is the most common urgent condition in general surgery, and yet there is no evidence-based definition for perforation. Therefore, all retrospective data published on perforated appendicitis are unreliable because of an ill-defined denominator. For approximately 2 years beginning in April 2005, we performed a prospective randomized trial investigating 2 different antibiotic regimens for perforated appendicitis. During this study, we strictly defined perforation as a hole in the appendix or a fecalith in the abdomen. Before this prospective study, perforation was staff surgeon opinion. We investigated the abscess rates in both the perforated and nonperforated appendicitis populations before and during the study to determine if our definition was safe and that there was not an increased risk of abscess formation in patients treated as nonperforated.

Methods

Records of all patients undergoing laparoscopic appendectomy for appendicitis during the immediate 2 years before using the definition were compared to those treated in the 2 years after the definition was implemented. Interval and incidental appendectomies were ruled out. The postoperative abscess rate (when perforation was not defined) was compared to the abscess rate of those for whom perforation was strictly defined.

Results

There were 292 patients treated for acute nonperforated appendicitis in the 2 years before the definition and 388 patients after the definition. There were 131 patients treated for perforated appendicitis before the definition and 161 after the definition was implemented. The abscess rate in those with perforated appendicitis increased from 14% to 18% after the definition was used. However, after the definition began to be used, the abscess rate for those patients treated as nonperforated decreased from 1.7% to 0.8%.

Conclusions

Defining perforation as a hole in the appendix or a fecalith in the abdomen is effective in identifying the patients at risk for postoperative abscess formation. Application of these criteria would allow substantial reduction in therapy for patients with purulent or gangrenous appendicitis who do not possess the same abscess risk. These data outline the first evidence-based definition of perforation.