Negative appendectomy rate in the era of CT: an 18-year perspective.

To estimate the correlation between the negative appendectomy rate (NAR) and the rate of preoperative computed tomography (CT) in patients suspected of having acute appendicitis who presented to the emergency department during an 18-year period. This retrospective institutional review board-approved, HIPAA-compliant study was performed in a 719-bed tertiary care adult teaching hospital with 58,000 annual emergency department visits. The authors obtained a waiver of informed consent and used the medical records system to compare patients suspected of having appendicitis who presented to the emergency department between 2003 and 2007 to those who presented between 1990 and 1994, the period just before CT became commonly used at the authors' institution for the evaluation of appendicitis. Surgical and pathology reports were reviewed to determine the NAR, and the authors queried the radiology databases to determine the proportion of appendectomy patients who underwent preoperative imaging. Outcome measures included the NAR, the proportion of appendectomy patients who underwent preoperative CT, and the annual number of appendectomies performed. The chi(2) test for trend was used to assess for changes in proportions, and linear regression was used to evaluate numeric trends. From 1990 to 2007, the NAR decreased significantly from 23.0% to 1.7% (P < .0001), the annual number of appendectomies decreased significantly from 217 per year to 119 per year (P = .0003), and the proportion of patients undergoing appendectomy who underwent preoperative CT increased significantly from 1% to 97.5% (P < .0001). There was a significant reduction in both the NAR and the number of appendectomies in patients who presented to the emergency department during an 18-year period, which was associated with a significant increase in the use of preoperative abdominal CT.