CT Diagnosis of Mucocele of the Appendix in Patients with Acute Appendicitis

The purpose of this study was to identify the CT features of mucocele of the appendix coexisting with acute appendicitis and to determine whether this entity can be differentiated from acute appendicitis without mucocele. CT scans of 70 patients (12 with acute appendicitis with mucocele, 29 with acute appendicitis without mucocele, 29 with a normal appendix) were retrospectively interpreted by two readers. The appendix was evaluated for maximal luminal diameter, cystic dilatation, luminal attenuation, appendicolith, mural calcification and enhancement, periappendiceal fat stranding, fluid, and lymphadenopathy. CT findings were compared by use of Mann-Whitney U and Fisher's exact tests. Receiver operating characteristics analysis was performed to assess the diagnostic utility of appendiceal luminal diameter in differentiating acute appendicitis with from that without coexisting mucocele. Cystic dilatation of the appendix and maximal luminal diameter achieved statistical significance (p < 0.05) for the diagnosis of acute appendicitis with mucocele. Mural calcification achieved statistical significance for one reader (p = 0.0049) and a statistical trend for the other (p < 0.1). A maximal luminal diameter greater than 1.3 cm had a sensitivity of 71.4%, specificity of 94.6%, and overall diagnostic accuracy of 88.2% for the diagnosis of acute appendicitis with mucocele. Although there is overlap with acute appendicitis without mucocele, CT features suggestive of coexisting mucocele in patients with acute appendicitis include cystic dilatation of the appendix, mural calcification, and a luminal diameter greater than 1.3 cm.