Size matters: Computed tomographic measurements of the appendix in emergency department scans

Abstract

Background: Radiologists use a size cutoff in appendiceal diameter to assist surgeons in diagnosing appendicitis, however, no consensus exists as to the size of a normal adult appendix. We aim to evaluate radial appendiceal diameter on CT in adult patients both with and without appendicitis.

Methods: Retrospective review of adults who underwent abdominal CT was performed. Variables collected include: demographics, BMI, WBC count at presentation, radial diameter of appendix (mm), presence of fat stranding, fecalith, and free fluid.

Results: During the study period, 3099 patients underwent CT. The appendix was visualized on 74% of scans. Mean appendiceal diameter was 6.6 mm (±1.7). The appendix was larger in patients with appendicitis (6.6 vs. 11.4; p < 0.0001). Overall appendectomy incidence was 3.2%. Sensitivity and specificity of CT in diagnosing appendicitis in this cohort of patients were 90% and 94%. NPV was 99.5%.

Conclusion: While appendiceal diameter was larger in patients with appendicitis, >20% of patients without appendicitis had an appendiceal diameter >7 mm. Diameter alone should not be relied upon to diagnose appendicitis.