The non-diagnostic ultrasound in appendicitis: is a non-visualized appendix the same as a negative study?

J Pediatr Surg. 2015 Jun;50(6):923-7. doi: 10.1016/j.jpedsurg.2015.03.012. Epub 2015 Mar 17.

Abstract

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.

Publication types

  • Evaluation Study

MeSH terms

  • Acute Disease
  • Adolescent
  • Appendicitis / diagnostic imaging*
  • Appendix / diagnostic imaging*
  • Child
  • Child, Preschool
  • False Negative Reactions
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Predictive Value of Tests
  • Retrospective Studies
  • Ultrasonography