Distal appendiceal dilatation in equivocal appendicitis may be a useful sign for prediction of normal appendix.

Despite many efforts to reduce unnecessary appendectomy for appendicitis, the negative appendectomy rate remains relatively high. Here, we investigated predisposing factors for normal appendix by analyzing the surgical outcomes for patients with equivocal appendicitis. Over a 3-year period, 1516 patients underwent treatment for appendicitis and 148 (10%) were prospectively diagnosed with equivocal appendicitis. We defined equivocal appendicitis as a right lower quadrant pain with tenderness and an apppendiceal diameter of 6 to 9 mm without appendicolith or severe adjacent inflammation as radiological findings. We investigated normal appendix rates in relation to clinical and radiological features. Of the 148 patients, 48 (32%) had a normal appendix and 100 had appendicitis. A higher normal appendix rate was found for low white blood cell count than for leukocytosis (41% vs 23%, odds ratio (OR) = 2.48), and laparoscopic treatment was then open (42% vs 21%, OR = 2.58). Distal appendiceal dilatation, as determined by radiological imaging, was associated with a higher normal appendix rate than whole dilatation (60% vs 27%, OR = 3.96). Low white blood cell count, laparoscopic treatment, and distal appendiceal dilatation were significant predisposing factors for normal appendix after surgery. Radiologically determined distal dilatation of the appendix may be a useful sign for predicting normal appendix.