Evaluation of the normal appendix at low-dose non-enhanced spiral CT.

PURPOSE: To evaluate the frequency of visualization, thickness and location of the normal appendix at non-enhanced spiral computed tomography (CT). MATERIALS AND METHODS: Low-dose spiral CT scans obtained for renal colic assessment in 243 patients were retrospectively reviewed. The frequency of visualization, thickness and location of normal appendices were recorded without knowledge of the patients' history for the appendectomy. RESULTS: Forty of 234 patients had a past history of appendectomy (17%). Sensitivity, specificity, positive and negative predictive values, and accuracy of visualization of the normal appendix were 71%, 85%, 96%, 37% and 73%, respectively. When no intraluminal content was visualized, this area was excluded from the measurement and the mean thickness was 3.4 mm+/-0.66. CONCLUSION: The normal appendix is frequently seen at nonenhanced spiral CT. Knowing the normal thickness of the appendix can help reduce false positive and false negative diagnoses of acute appendicitis when reviewing non-enhanced spiral CT.