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CT vs USS in the diagnosis of acute appendicitis

Three Part Question

[In patients presenting with symptoms suggestive of acute appendicitis] is [CT or Ultrasound better] in [confirming the diagnosis of acute appendicitis]?

Clinical Scenario

A young girl presents in the emergency department with right iliac fossa pain, anorexia, nausea and vomiting for the past 12hours. On examination she has significant right iliac fossa tenderness but no rebound or guarding. Her temperature is 37.3„aC and the inflammatory markers are normal. You are not entirely certain if she has acute appendicitis and would not like her to go through an unnecessary operation. You are wondering whether Ultrasound or CT is better in confirming the diagnosis of acute appendicitis.

Search Strategy

The Pubmed database from 1950-2006 was searched (
The terms used were [acute appendicitis] AND [Ultrasound or CT] AND [diagnosis].

Search Outcome

The search result yielded 887 articles. The search was then narrowed down to 552 articles by excluding non-English articles and articles with no abstracts. Among these 552 articles, articles not directly in relevance to the 3-part question were excluded. The remaining 8 articles are summarised below.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Keyzer C
94 patients aged 16-81 years.Prospective patient studyAccuracy of USS = 84% ; Accuracy of CT = 90%No difference in diagnostic performancePaediatric population not included
Blebea JS et al
100 adult patientsProspective patient studyAccuracy of USS = 73%-75% ; Accuracy of CT = 93%CT is the best initial exam for suspected appendicitis in the adult pt.Paediatric population not included
Poortman P et al
199 patients aged 3-89yearsProspective patient studyAccuracy of USS = 78% ; Accuracy of CT = 78%CT was not superior to USS in the diagnosis of acute appendicitisCT scans evaluated by less experienced radiology staff. Use of non-helical CT
Wise SW et al.
100 patients >18yrs oldProspective patient studyAccuracy of USS = 74-76% ; Accuracy of CT = 87-93%CT had significantly better diagnostic performance than sonographyPaediatric population not included
Pickuth et al.
120 patients aged 8-81yrs.Prospective studySensitivity of USS = 87%, Sensitivity of CT = 95% ; Specificity of USS = 74%, Specificity of CT 89%Unenhanced spiral CT is more accurate than USS in patients suspected of having acute appendicitisOnly equivocal cases were imaged
Horton DH et al.
89 patients aged 18-65 yearsProspective randomised studySensitivity of USS = 76%, Sensitivity of CT = 97% ; Specificity of USS = 90%, Specificity of CT = 100%Non-contrast CT scan is the superior diagnostic modalityPaediatric population not included.
Cho CS et al.
51 patients aged 13-80 yearsRetrospective reviewAccuracy of USS = 68% ; Accuracy of CT = 97%CT can be used to improve the accuracy of diagnosis of obscure RIF painSmall sample size Retrospective review
Balthazar EJ et al.
100 patients aged 15-82years .Prospective study.Accuracy of USS = 83% ; Accuracy of CT = 94%CT was superior to USS in evaluating patients suspected of having acute appendicitis.Paediatric population not included.


Most of these studies did not include paediatric patients. Studies that suggested CT superiority employed helical CT. The majority of these studies did not find any significant benefit in the use of intravenous or rectal contrast material during CT. USS accuracy seems to be strongly dependent on operator experience and skill.

Clinical Bottom Line

Helical CT without contrast is more accurate than Sonography in the diagnosis of acute appendicitis.


  1. Keyzer C et al 'Comparison of US and Unenhanced Multi-Detector Row CT in Patients Suspected of Having Acute Appendicitis'. Radiology 2005 ; 236(2) : 527-34
  2. Blebea JS, Meilstrup JW and Wise SW 'Appendiceal Imaging : Which Test is Best?' Seminars in Ultrasound, CT and MRI 2003 2003 ; 24(2) : 91-95
  3. Poortman P et al ' Comparison of CT and Sonography in the Diagnosis of Acute Appendicitis : A Blinded Prospective Study' AJR Am J Roentgenol 2003 ; 181(5) : 1355-9
  4. Wise SW et al. 'Comparative Assessment of CT and Sonographic Techniques for Appendiceal Imaging' AJR Am J Roentgenol 2001 ; 176(4) : 933-41
  5. Pickuth D, Heywang-Kobrunner S and Spielmann RP 'Suspected Acute Appendicitis : Is Ultrasonography or Computed Tomography the Preferred Imaging Technique?' Eur J Surgery 2000 ; 166(4) : 315-9
  6. Horton MD, Counter SF, Florence MG and Hart MJ 'A Prospective Trial of Computed Tomography and Ultrasonography for Diagnosing Appendicitis in the Atypical Patient' Am J Surgery 2000 ; 179(5) : 379
  7. Cho CS, Buckingham JM, Pierce M and Hardman DT 'Computed Tomography in the Diagnosis of Equivocal Appendicitis'. Aust NZ J Surg 1999 ; 69(9) 664-7
  8. Balthazar EJ et al. 'Acute Appendicitis : CT and US Correlation in 100 patients' Radiology 1994 ; 190(1) : 31-5