Imaging of acute appendicitis and its impact on negative appendectomy and perforation rates: the St. Paul's...

Preoperative imaging of acute appendicitis is widely practised. The aim of this study is to determine the prevalence of preoperative imaging of acute appendicitis in our institution and its effect on the negative appendectomy rate and perforation rates.

We undertook a retrospective review of all patients who underwent appendectomy from January 2000 to December 2004. All available preoperative ultrasound (US), computed tomography (CT), and pathology results were reviewed.

A total of 380 appendectomies were performed over this time period for the preoperative diagnosis of acute appendicitis. Fifty-nine patients had histologically normal appendices, giving an overall negative appendectomy rate of 15.5%. Overall, patients who had preoperative imaging showed a lower negative appendectomy rate (11.4%) than did those without imaging (22.2%). Without preoperative imaging, women had a higher negative appendectomy rate (34.3%) than did men (17.4%). Reduction in the negative appendectomy rate was demonstrated with preoperative imaging in both sexes (16.7% and 5.7%, respectively). Also demonstrated is a definite trend toward increased use of preoperative CT and away from US as the sole preoperative imaging modality. This is associated with a reduced negative appendectomy rate.

The increased use of preoperative imaging, particularly CT, is associated with a decreased negative appendectomy rate and a decreased perforation rate at our institution.