Influence of preoperative computed tomography on patients undergoing appendectomy

The frequency of computed tomography (CT) ordered by emergency department physicians at our facility was noted to sharply increase in early 1998 after a New England Journal of Medicine (NEJM) article recommending routine CT in patients with suspected appendicitis. Numerous studies have proven the accuracy of CT for detecting acute appendicitis; however, the most appropriate use of CT continues to evolve. We sought to evaluate the effect of increased CT use on negative appendectomy rate and perforation rate at our institution and to better delineate in whom CT is most beneficial. CT use was retrospectively evaluated and found to sharply increase in April 1998. The authors then reviewed the medical records of 291 consecutive patients undergoing appendectomy 18 months before and after the NEJM article. Patients with interval appendectomies and those 12 years of age or younger were excluded. The remaining 226 patients constitute the study cohort. The study cohort was then divided into the two groups. The "Discriminate Group" consists of patients from the 18 months before the NEJM article impact and a period of selective CT use. The "Indiscriminate Group" comprises patients from the subsequent 18 months in which CT use was substantially higher and routinely obtained before surgical evaluation. After chart review an objective clinical score (Alvarado score) was assigned to each patient. Comparison was then made between the two groups on perforation rate, negative appendectomy rate, time delay to operating room, and Alvarado score. Additionally patients undergoing preoperative CT were compared with those without CT. These groups were also evaluated on the basis of negative appendectomy rate, perforation rate, and delay to the operating room. CT in patients with abdominal symptoms associated with appendicitis increased from 188 in the Discriminate Group to 1035 in the Indiscriminate Group. In the Discriminate Group the negative appendectomy rate was 15.1 per cent. After the indiscriminate use of CT the negative appendectomy rate decreased to 13.3 per cent, but this was not significant. Males experienced a decrease in the negative appendectomy rate from 10.1 to 6.9 per cent, whereas the rate for females increased slightly from 21.3 to 22.9 per cent. Again we found no statistical significance in these changes. The overall perforation rate of 17.9 per cent in the first 18 months decreased to 13.3 per cent in the following 18 months but again was not statistically significant. The Alvarado scores between the Discriminate and Indiscriminate groups were 6.7 and 7.3, respectively (P = 0.02). Patients with preoperative CT averaged 11.9 hours to the operating room compared with 6.5 hours for those without CT (P = 0.03). Use of CT did not decrease perforation rate but did globally reduce negative exploration (P = 0.05). This reduction in negative exploration however was not discriminated by sex. CT use in suspected acute appendicitis has greatly increased over the past several years. The dramatic increase in CT use at our institution has not resulted in dramatic decreases in negative appendectomy rate or statistically significant changes in perforation rate. The optimal use of CT in evaluating patients with suspected appendicitis has yet to be determined. Surgical consultation should be obtained early to avoid indiscriminate tests.