Computed Tomography Mimics of Acute Appendicitis: Predictors of Appendiceal Disease Confirmed at Pathology

PURPOSE: Imaging and pathology findings are used to analyze the capability of computed tomography (CT) to distinguish between acute appendicitis and radiological mimickers. MATERIALS AND METHODS: A retrospective review of 5861 patients undergoing abdominopelvic CT from 2000 to 2008 for suspicion of acute appendicitis was performed. Appendix diameter, surrounding inflammation, appendicolith, and location were assessed. Only those cases were included where patients underwent surgery for acute appendicitis on CT findings. Pathology specimens were examined and those indicative of acute appendicitis were identified. Statistical analysis was performed to correlate pathology and CT signs. RESULTS: A total of 969 of the 5681 patients were included in the study. Acute appendicitis was verified in 870/969 (89%) cases, while 99/969 (11%) demonstrated either chronic findings (i.e., fibrosis [32%], granulomatous disease [16%], lymphoid hyperplasia [11%]) or no abnormality. In regression models, appendiceal diameter >7 mm (odds ratio [OR] = 3.98, P < 0.0001) and mesenteric fat stranding (OR = 6.04, P < 0.0001) were associated with acute appendicitis. Nearly 87% (754/870) of acute appendicitis cases showed both signs on CT, compared with 53% (52/99) of those with other pathologic finding (P < 0.0001). In cases with non-appendicitis findings, 39% (39/99) had only one of these signs compared with 13% (112/870) of those with acute appendicitis (P < 0.0001). CONCLUSION: Diseases of the appendix other than acute appendicitis may manifest with isolated radiological findings and should be considered as part of the differential diagnosis in cases of borderline acute appendicitis.