Approximately 290,000 patients in the United States underwent urgent appendectomy in 1999. A normal appendix is removed in up to 40 percent of patients who undergo surgery because of a preoperative diagnosis of appendicitis. Several studies have reported improved diagnostic accuracy with the incorporation of computed tomography (CT) into clinical decision-making, but other studies have failed to replicate these results. Perez and colleagues studied the contribution of CT scanning to the accuracy of preoperative diagnosis of appendicitis at a community hospital.

The study included all 118 patients who underwent nonincidental appendectomy between April 1999 and June 2000 at a 300-bed community hospital. The impact of increasing the use of CT scanning in the diagnosis of appendicitis was studied by comparing data from these patients with data from 100 patients who underwent nonincidental appendectomy at the same hospital during 1994. Data included patient demographics, diagnostic tests, pathologic diagnoses, antibiotic usage, complications, duration of emergency department treatment, and length of hospital stay.

The two groups of patients were comparable in all important respects. Preoperative CT scanning was performed in 11 percent of patients in the 1994 cohort and 48.3 percent of those in the 1999–2000 cohort. In spite of the more than fourfold increase in preoperative CT scans, the percentage of normal appendixes removed increased (nonsignificantly) from 12 percent to 17.8 percent. Furthermore, the diagnostic accuracy of the CT scans did not improve significantly between the two study periods. In the 1994 study, CT accuracy was 81.8 percent, compared with 80.7 percent in the 1999–2000 study. The authors calculate that CT scanning did not add to the post-test probability of correctly diagnosing appendicitis or accurately ruling out appendicitis. The patients who underwent CT scanning spent a significantly longer time in the emergency department and had a longer hospital stay than the patients who did not undergo CT scanning.

The authors conclude that widespread use of CT scanning has not improved the accuracy of diagnosing appendicitis and has contributed to longer emergency department and hospital stays. These results confirm the findings of several previous studies but contradict the findings of other studies in which CT scanning reduced the number of normal appendixes that were removed. The authors of the present study speculate that the differences may be explained by the technique of CT used. Investigations using oral, rectal, or intravenous contrast media may have greater accuracy but may be more difficult to conduct successfully in an emergency situation.