Computed tomography scanning for the diagnosis of perforated appendicitis

The optimal initial treatment for perforated appendicitis may be nonoperative. For this reason it is important to be able to reliably distinguish between acute and perforated appendicitis. CT scanning has been shown to be highly accurate for the diagnosis of appendicitis, but it has not been specifically evaluated for perforated appendicitis. Our objective was to evaluate CT for the diagnosis of perforated appendicitis. Our study population comprised 84 patients who underwent appendectomy between 1993 and 1997 and who had CT scanning performed preoperatively. Medical records were reviewed retrospectively. CT scans were reviewed in a blinded fashion. CT findings were correlated with pathologic and clinical factors. Sixteen patients with acute appendicitis, 59 patients with gangrenous or perforated appendicitis, and 9 patients with normal appendices or other diagnoses were evaluated. For patients with pathologic documentation of appendicitis, CT findings that independently predict perforation or gangrene included abscess (P < 0.001), phlegmon (P < 0.001), extraluminal gas (P = 0.01), and terminal ileal wall thickening (P = 0.03). CT findings of an abscess, extraluminal gas, or phlegmon have a sensitivity of 92 per cent, specificity of 88 per cent, positive predictive value of 96 per cent, and negative predictive value of 74 per cent for perforated or gangrenous appendicitis. We conclude that CT can reliably distinguish between acute and perforated appendicitis.