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Pediatric Appendicitis: CT or Ultrasound?

Posted May 08 2013 12:00am



Appendicitis is the most common pediatric surgical emergency accounting for 5% of urgent pediatric outpatient visits for abdominal pain. Computed tomography (CT) and ultrasonography (US) are two imaging modalities used in the diagnostic evaluation of acute appendicitis. Both have decreased the incidence of negative appendectomy results. It is well known that CT has greater diagnostic accuracy than US for diagnosing acute appendicitis, but there is concern over long-term cancer risk, with routine use of CT in children.


Is CT or US more accurate in the diagnosis of acute appendicitis?
Doria AS et al. US or CT for Diagnosis of Appendicitis in Children and Adults? A Meta-Analysis. Radiology 2006 Oct; 241(1): 83–94. PMID: 16928974
  • What they did:
    • Meta-analysis
    • 26 studies involving children
    • 9,356 total patients
  • Primary outcome:
    • Pooled sensitivity and specificity of CT and US in diagnosis of acute appendicitis in children
  • Results:
    • Pooled sensitivity and specificity for US in diagnosis of appendicitis in children: 88% and 94%
    • Pooled sensitivity and specificity for CT in diagnosis of appendicitis in children: 94% and 95%
  • Conclusion: CT has a higher sensitivity than US for diagnosis of acute appendicitis in children.

Does duration of abdominal pain increase accuracy of ultrasound?
Bachur RG et al. The Effect of Abdominal Pain Duration on the Acuracy of Diagnostic Imaging for Pediatric Appendicitis. Ann Emerg Med 2012; 60: 582–90. PMID:22841176
  • What they did:
    • Prospective multicenter observational study
    • 2,349 children with suspected appendicitis at 9 pediatric EDs
    • Age 3 – 18 years
    • Placed into categories based on duration of time of symptoms: <12 h, 13 – 24 h, 25 – 36 h, 37 – 48 h, and 49 – 72 h
  • Primary Outcome:
    • The presence or absence of acute appendicitis
  • Results:
    • 1,884 underwent CT only
    • 586 underwent US only
    • 282 underwent CT and US
    • Most frequent abdominal pain duration at presentation: 12 – 23 hrs category
  • Limitations:
    • 1,082 pts did not undero surgery, but followed up with telephone calls (Only had 88.6% follow up)
  • Conclusions:
    • Duration of abdominal pain DID NOT affect sensitivity or specificity of CT to diagnose appendicitis
    • Duration of abdominal pain DID increase sensitivity and NPV for US with longer duration of abdominal pain, but no affect on specificity or PPV
    • US sensitivity and NPV is as good as CT after 48 hrs of pain symptoms.
    • Do not rely on US to rule-out appendicitis early in the course of illness.
  • Read more about this paper at PEMLit.org !

Summary
The advantages of US include low cost, lack of radiation, and dynamic information with graded compression. The advantages of CT include: no operator dependency, delineation of extent of disease (i.e. perforated appendicitis), easier visualization, unchanged quality of imaging over time, and multiplanar reconstruction of images. Based on the above study, if symptoms have been present for >48 hours, US is just as good as CT for ruling out the diagnosis of acute appendicitis.

The decision to obtain an US vs CT for children with suspected appendicitis remains a challenge. On a case by case basis, one should consider the following 4 major goals in care:
  1. Minimize rates of missed appendicitis
  2. Minimize risk from radiation exposure
  3. Avoid misdiagnosis leading to negative appendectomy
  4. Properly identify appendicitis before perforation
Question
How do YOU approach a pediatric patient in whom you have a moderate pretest probability for appendicitis?  


References
  1. Bachur RG et al. The Effect of Abdominal Pain Duration on the Acuracy of Diagnostic Imaging for Pediatric Appendicitis. Ann Emerg Med 2012; 60: 582 – 90.  PMID:22841176
  2. Doria AS et al. US or CT for Diagnosis of Appendiitis in Children and Adults? A Meta-Analysis. Radiology 2006 Oct; 241 (1): 83 – 94.  PMID: 16928974
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