The equivocal appendix at CT: Prevalence in a control population

The purpose of the study was to determine the prevalence of appendices with an equivocal appearance at computed tomography (CT) in a control population. We retrospectively identified a control population of 150 patients who underwent CT of the abdomen and pelvis for evaluation of hematuria (without abdominal pain, fever, or colonic disease). One reader measured the diameter of the appendix and noted if the appendix was either isodense in appearance or airless and fluid filled. Sixty-seven of 150 cases (44.6%) demonstrated appendiceal diameter greater than 6 mm. The appendix was collapsed or isodense in 34/150 cases (22.7%). Only ten of 150 or 6.6% of cases were isodense in combination with diameter greater than 6 mm, and none had diameter greater than 10 mm. Only one of 150 cases (0.67%) demonstrated airless fluid within the lumen, and the appendix measured less than 6 mm. While the diameter of the normal appendix is frequently greater than 6 mm, none measured greater than 10 mm in combination with ambiguous morphology. Furthermore, in the normal appendix, airless fluid filling the lumen is a rare appearance with a prevalence of less than 1%. While appendicitis could undoubtedly occur in an isodense appendix between 6 and 10 mm in diameter, such an appearance can occur in up to 6.6% of the normal population.