tubo-ovarian abscess, ovarian torsion, or ectopic pregnancy are suspected Significant pain should be treated with intravenous (IV) narcotics prior to US, as US requires graded compression of the bowel and can be quite painful in a patient with appendicitis Administration of narcotics has not been shown to mask symptoms in a clinically significant way US has a reported sensitivity of 80% to 92% with a specificity of 86% to 98% In general, US has less utility in patients with a high body mass index and patients earlier in the course of disease Secondary signs of appendicitis on US (focal edema of fat, free fluid, local ileus) are helpful if the appendix is not visualized Technically, a noncompressible enlarged appendix is diagnostic of appendicitis, although the study must be considered equivocal if the appendix is not identified The management of children with nondiagnostic US should be guided by the level of clinical suspicion; children with low suspicion who are improving may be candidates for observation, whereas children with persistent concern for appendicitis may warrant advanced imaging or admission for serial examinations When available, a pediatric surgeon should be consulted for management decisions about children with high suspicion of appendicitis but equivocal US results CT and magnetic resonance imaging (MRI) have both been used for diagnosis Focal CT has a diagnostic sensitivity of 95% with a specificity of 96% CT can identify an enlarged appendix, focal thickening of the cecum, periappendiceal inflammation, mesenteric nodes, and fluid collections associated with perforation CT should be performed using IV contrast; oral and rectal contrast are not generally necessary CT is most interpretable in patients with adequate periappendiceal fat MRI has been shown to have equivalent test characteristics to CT, and can be performed rapidly in children without the need for sedation or contrast