The Impact of the Liberal Use of CT in the Work Up of Acute Appendicitis

Background: Acute appendicitis has historically been considered a clinical diagnosis, necessitating a CT scan only in the face of equivocal signs and symptoms. The purpose of this study is to determine whether or not the liberal use of CT in the work up of acute appendicitis results in a decreased negative appendectomy rate (NAR). Methods: The medical records of 940 consecutive patients who underwent emergency appendectomy between January 2002 and December 2006 were reviewed. Data collected included patient demographics, length of stay (LOS), results of contrast enhanced CT scans, emergency department (ED) work up time, and final pathology. Results: During the study period 940 patients (mean age 34.5±16.7 years, 53% males) underwent emergency appendectomy (64% laparoscopic). Eight hundred thirteen (86% patients, 50% males) underwent pre-operative CT scans. Final pathology was 76.1% acute appendicitis, 10% acute appendicitis with perforation, 7.7% gangrenous appendicitis, 1.2% acute appendicitis with abscess, 0.7% chronic appendicitis, and 4.3% negative for appendicitis. No difference was noted in the overall appendicitis rate by gender in the CT (Fishers exact test, p=0.96) or non-CT group (Fishers exact test, p=0.75). Similarly, no difference was noted by age (CT p=0.14, non-CT p=0.26). The NAR was lower for the CT group (3.4%) compared to the non-CT group (9.4%) (p=0.002). The NAR did not differ significantly by gender (Fishers exact test, p=0.491). Despite prolonging the ED work up time by 4.3 hours, the perforation rate did not differ between the CT (9.5%) and non-CT (12.6%) groups (p=0.30), nor did the LOS (3.67 vs. 3.63 days, p= 0.92). The sensitivity, specificity, negative predictive value, and positive predictive value of CT scans was 99%, 61%, 68%, and 99%, with an overall accuracy of 98%. The positive and negative likelihood ratios were 2.52 and 0.02 respectively. The ROC for CT scans in predicting appendicitis was 79.8% (95% CI: 76.9%, 82.5%). Conclusions: The use of CT in the work up of acute appendicitis is associated with a lower negative appendectomy rate independent of gender and age. The additional time spent obtaining a CT does not appear to increase the risk of perforation nor increase the LOS.