• Kimberly Garcia, Marta Hernanz-Schulman, Debbie Lee Bennett, Stephen E Morrow, Chang Yu, and J Herman Kan.
• Department of Radiology and Radiological Sciences, Vanderbilt Children's Hospital, Vanderbilt University, Nashville, TN 37232, USA.
• Radiology. 2009 Feb 1;250(2):531-7.

PurposeTo determine whether lack of visualization of the appendix on otherwise normal abdominopelvic computed tomographic (CT) images can help exclude appendicitis in the pediatric population.Materials And MethodsThe study was institutional review board approved and HIPAA compliant. One thousand one hundred thirty-nine children suspected of having appendicitis were referred for CT examination between July 2002 and December 2006. Exclusion criteria included CT diagnosis of appendicitis or other cause of symptoms and lack of clinical follow-up. Consensus review was performed by two pediatric radiologists to determine normal examinations, leaving a final study group (nonvisualized appendix) of 156 patients (mean age, 9.6 years; boys, 7.2 years; girls, 10.2 years) and a control group (visualized appendix) of 421 patients (mean age, 11.0 years; boys, 9.8 years; girls, 11.2 years). In the control group, there were 168 subjects with a partially visualized (PV) appendix and 253 with a fully visualized (FV) appendix. Pericecal fat was graded according to published criteria. Diagnosis was confirmed at surgery or clinical follow-up. Negative predictive values were calculated with 95% confidence intervals (CIs).ResultsThere were three false-negative findings (study group, two; control group, one [FV]). The negative predictive value of a normal CT examination in pediatric patients with a nonvisualized appendix was 98.7% (95% CI: 95.5%, 99.8%); that with a visualized appendix, 99.8% (95% CI: 98.7%, 99.99%); that with a PV appendix, 100% (95% CI: 97.8%, 100%); and that with a FV appendix, 99.6% (95% CI: 97.8%, 99.99%).ConclusionPediatric abdominopelvic CT images with nonvisualized appendix have a high negative predictive value, without significant difference from cases with a PV or even FV appendix. The false-negative rate was similar to those reported in two adult series.

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