Reassessment of CT images to improve diagnostic accuracy in patients with suspected acute appendicitis and an equivocal preoperative CT interpretation.

OBJECTIVES: To identify CT features that discriminate individuals with and without acute appendicitis in patients with equivocal CT findings, and to assess whether knowledge of these findings improves diagnostic accuracy.
METHODS: 53 patients that underwent appendectomy with an indeterminate preoperative CT interpretation were selected and allocated to an acute appendicitis group or a non-appendicitis group. The 53 CT examinations were reviewed by two radiologists in consensus to identify CT findings that could aid in the discrimination of those with and without appendicitis. In addition, two additional radiologists were then requested to evaluate independently the 53 CT examinations using a 4-point scale, both before and after being informed of the potentially discriminating criteria.
RESULTS: CT findings found to be significantly different in the two groups were; the presence of appendiceal wall enhancement, intraluminal air in appendix, a coexistent inflammatory lesion, and appendiceal wall thickening (P < 0.05). Areas under the curves of reviewers 1 and 2 significantly increased from 0.516 and 0.706 to 0.677 and 0.841, respectively, when reviewers were told which CT variables were significant (P = 0.0193 and P = 0.0397, respectively).
CONCLUSIONS: Knowledge of the identified CT findings was found to improve diagnostic accuracy for acute appendicitis in patients with equivocal CT findings. KEY POINTS: • Numerous patients with clinically equivocal appendicitis do not have acute appendicitis • Computed tomography (CT) helps to reduce the negative appendectomy rate • CT is not always infallible and may also demonstrate indeterminate findings • However knowledge of significant CT variables can further reduce negative appendectomy rate • An equivocal CT interpretation of appendicitis should be reassessed with this knowledge.