title: Accuracy of Magnetic Resonance Imaging and Ultrasound for Appendicitis in Diagnostic and Nondiagnostic Studies.
abstract: OBJECTIVE
  Suggestive radiographic studies with nonvisualization of the appendix can present a challenge to clinicians in the evaluation of pediatric abdominal pain. The primary objective of this study was to quantify the accuracy of magnetic resonance imaging (MRI) and of ultrasound (US) in the setting of nonvisualization of the appendix. Secondary objectives reported include sensitivity of MRI and US overall and correlation between MRI and US for diagnosis of appendicitis.
  
  
  METHODS
  Records of pediatric emergency department patients aged 3 to 21 years undergoing MRI and/or US for the evaluation of appendicitis were retrospectively reviewed. Radiographs were categorized as a normal appendix, neither demonstrating the appendix nor demonstrating abnormalities consistent with appendicitis; equivocal, not demonstrating the appendix but showing evidence of appendicitis; demonstrating an abnormal appendix consistent with appendicitis; or demonstrating an alternate pathology. The reading was compared with the final diagnosis for accuracy.
  
  
  RESULTS
  Of the 589 patients included, 146 had appendicitis. Diagnostic accuracy for studies with a nonvisualized appendix without secondary signs of appendicitis was 100% for MRI and 91.4% (95% CI = 87.3% to 94.2%) for US. Diagnostic accuracy for studies with a nonvisualized appendix with secondary signs of appendicitis was 50% (95% CI = 2.5% to 97.5%) for MRI and 38.9% (95% CI = 18.2% to 64.5%) for US. Appendicitis was ultimately diagnosed in 8.6% of patients with an otherwise negative right lower quadrant (RLQ) US that failed to directly identify the appendix. There was a moderate correlation between US and MRI (ρ = 0.573, p = 0.0001) when all studies were considered.
  
  
  CONCLUSIONS
  Magnetic resonance imaging without secondary signs of appendicitis is effective in excluding appendicitis regardless of whether the appendix is directly visualized, while otherwise negative RLQ US that fail to identify the appendix are less useful. Secondary signs of appendicitis without visualization of the appendix were not helpful regardless of radiographic modality. Results of MRI and US correlated moderately well.
authors.affiliation: Department of Emergency Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Y Liza
authors.initials: YL
authors.lastname: Kearl
authors.affiliation: Department of Emergency Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Ilene
authors.initials: I
authors.lastname: Claudius
authors.affiliation: Department of Emergency Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Sol
authors.initials: S
authors.lastname: Behar
authors.affiliation: Department of Pediatrics, Los Angeles County and University of Southern California Hospital, Los Angeles, CA.
authors.forename: John
authors.initials: J
authors.lastname: Cooper
authors.affiliation: University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Dollbaum
authors.affiliation: Department of Emergency Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Madhu
authors.initials: M
authors.lastname: Hardasmalani
authors.affiliation: Department of Emergency Medicine, Los Angeles County and University of Southern California Hospital, Los Angeles, CA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Hardiman
authors.affiliation: Department of Emergency Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Emily
authors.initials: E
authors.lastname: Rose
authors.affiliation: Department of Emergency Medicine, University of Southern California, Keck School of Medicine, Los Angeles, CA.
authors.forename: Genevieve
authors.initials: G
authors.lastname: Santillanes
authors.affiliation: Department of Emergency Medicine, Los Angeles County and University of Southern California Hospital, Los Angeles, CA.
authors.forename: Carl
authors.initials: C
authors.lastname: Berdahl
mesh_terms: D015746:Abdominal Pain / Q000209:etiology*; D000293:Adolescent; D001064:Appendicitis / Q000175:diagnosis*; D001065:Appendix / Q000000981:diagnostic imaging; D002648:Child; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D010808:Physical Examination; D011237:Predictive Value of Tests; D011859:Radiography; D012189:Retrospective Studies; D014463:Ultrasonography / Q000592:standards*