Purpose: The purpose of this retrospective study was to investigate outcomes in children who underwent a non-diagnostic ultrasound (US) evaluating for appendicitis and to identify predictors of a negative diagnosis.
Methods: An IRB-approved retrospective chart review was performed on patients age 0-18, who underwent an abdominal US evaluating for acute appendicitis from 2004 through 2013. Clinical data and specified outcomes were recorded, and exams were categorized into non-diagnostic studies and further separated into studies where the appendix was non-visualized.
Results: Of the 1383 studies included for analysis, 876 were non-diagnostic for acute appendicitis (63.34%) with 777 specifically because the appendix was non-visualized. Seven hundred forty of the 876 non-diagnostic studies and 671 of the 777 non-visualized studies were ultimately considered true negatives, corresponding to a negative predictive value (NPV) of 84.47 and 86.36%, respectively. In patients with WBC <7.5×10(9)/L, the NPV of non-diagnostic and non-visualized studies increased to 97.12 and 98.86%, respectively. Patients with WBC <11.0×10(9)/L have similarly high NPVs of 95.59 and 96.99% (non-diagnostic and non-visualized).
Conclusion: Based on the high NPV of a non-diagnostic US in children without leukocytosis, these patients may safely avoid further diagnostic imaging for the workup of suspected appendicitis.
Keywords: Abdominal ultrasound; Appendicitis; Negative predictive value; Non-diagnostic ultrasound.
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