Objective:

To establish the accuracy of unenhanced CT in the preoperative diagnosis of acute appendicitis.

Design:

Accuracy study, prospective and blinded.

Setting:

The University Hospital.

Participants:

52 patients with clinical and laboratorial manifestations of acute appendicitis.

CT diagnosis was made by:

presence of an abnormal appendix, appendiceal calculi with pericecal phlegmon or alterations in the pericecal appendicular site and absence of signs that may lead to other diagnosis.

Main outcome measures:

Overall accuracy, comparing the tomographic aspects with the intra-operative findings and pathological reports ("gold standard").

Results:

Acute appendicitis was confirmed in 44 cases. Efficacy was 92 per cent, sensitivity was 91 per cent, specificity was 100 per cent, positive predictive value was 100 per cent and negative predictive value was 67 per cent.

Conclusions:

Unenhanced CT presents a similar overall accuracy to that reported by other authors who studied enhanced CT diagnosis of acute appendicitis.