Appendicitis: use of arrowhead sign for diagnosis at CT.

PURPOSE: To determine the frequency of collection of a contrast medium in the upper portion of the cecum, which the authors call the arrowhead sign, on computed tomographic (CT) scans of the lower abdomen and to assess the sensitivity and specificity of this sign for appendicitis. MATERIALS AND METHODS: One hundred consecutive patients clinically suspected of having appendicitis prospectively underwent helical CT limited to the lower abdomen. Contrast media were administered orally and by means of an enema. Each scan was reviewed for the arrowhead sign, and the findings were correlated with surgical and pathologic results or clinical follow-up findings. RESULTS: The arrowhead sign was present in 17 of 56 cases (30%) of appendicitis and in no case of excluded appendicitis. It allowed the unequivocal diagnosis of appendicitis in four cases (7%) of otherwise non-specific right lower-quadrant inflammation and in one case (2%) of subtle appendicitis seen at CT. CONCLUSION: The arrowhead sign is an often present, highly specific sign of appendicitis that can add specificity to the diagnosis of right lower-quadrant inflammatory processes at CT.