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Ultrasound scanning in the diagnosis of acute appendicitis in adults

Three Part Question

Is an [ultrasound scan] sufficiently sensitive or specific for the [diagnosis] of [acute appendicitis in adults]?

Clinical Scenario

A 24 year old patient attends the emergency department with a history and examination suggestive of acute appendicitis. You are aware that an isolated full blood count is neither specific nor sensitive and wonder whether an ultrasound scan is an alternative tool to rule-in or rule-out acute appendicitis in adults

Search Outcome

311 papers were found, of which 272 were irrelevant or of insufficient quality for inclusion. The remaining 5 papers are shown below

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Orr et al
Meta-analysis (17 papers, 3358 patients) reviewing the performance of ultrasound in the diagnosis of acute appendicitis. Papers analysing the role of USS in a paediatric population were excluded. Articles cited in the references of reviewed papers were reviewed, as were recent journals. No unpublished data sought. NPV and PPV calculated for 3 three groups: I - those normally operated on II - those usually observed III - those usually sent homeMeta-analysisUSS (overall performance)Sens 84.7% (81-87.8%), Spec 92.1 (88-95.2%), LR + 10.6, LR - 0.17Only english language papers reviewed. 1 article excluded on basis of sample size (21 pts), 2 others excluded as results felt to be outliers, though methodology thought to be sound. Inclusion criteria variable.
USS (Group I)PPV 97.6, NPV 59.5
USS (Group II)PPV 87.3, NPV 89.9
USS (Group III)PPV 19.8, NPV 99.7
Skaane et al
205 patients with suspected acute appendicitisDiagnostic test study, blindedClinical examinationSens 78%, Spec 64%, LR + 2.16, LR - 0.34No gold standard Unclear duration of follow up Not exclusively adults
USSSens 36%, Spec 88%, LR + 3.0, LR - 0.72
Zielke et al
724 unselected patients (1-90 years) with suspected acute appendicitis. All patients had an USS after clinical assessment. 3 categories of patient identified: A - those needing urgent laparotomy B - those needing inpatient observation C - those unlikely to have appendicitis and could be followed up as an outpatient Follow up of non-operative cases 1 day later.Prospective, diagnositc test studyClinical impressionSens 50%, Spec 95%, LR + 10.1, LR - 0.53No gold standard for non-operative group Unclear if sonographer blinded to clinical impression 55 excluded as no USS Short period of follow up Not exclusively adults
USS (all)Sens 89%, Spec 96%, LR + 24.6, LR - 0.21
USS (A)Sens 89%, Spec 81%, LR + 4.6, LR - 0.14
USS (B)Sens 75%, Spec 95%, LR + 16, LR - 0.26
USS (C)Sens 53%, Spec 99%, LR + 76, LR - 0.46
Chen et al
191 patients (15-79 years) with a suspected clinical diagnosis of acute appendicitis. All received an USS. The non-operative group were reviewed 2 weeks laterDiagnositic test studyUSS resultSens 99%, Spec 68%, LR + 5.79, LR - 0.22No gold standard Unclear if blinded
Franke et al
2280 patients (age>6 years) recruited from 11 departments with acute abdominal pain, up to 1 week post admission. 894 patients hadUSS, those in the non-operative group followed up at 30 days post dischargeMulti-centre, prospective diagnostic test studyUSS resultSens 55.2%, Spec 95.1%, LR + 11.4, LR - 0.46No gold standard investigation Individuals included up to one week after onset of pain Only 894 patients had an ultrasound, of which 24 results were lost No protocol to dictate which patient received an USS, the decision being left to the individual clinician Not exclusively adults


Orr's meta-analysis includes all papers identified for critical review at the initial stages fo the BET. Although the criteria use for paper selection were insufficient for a true systematic review or meta-analysis. The data from Orr, Zielke and Franke show a high specificity for USS in the diagnosis of acute appendicitis. This is supported from the smaller trial by Skaane. The remaining trial from Chen, seems to contradict the other trials, but is included as the trial is well designed. The weight of evidence however supports the use of USS in the diagnosis of appendicitis

Clinical Bottom Line

USS has a role ruling-in acute appendicitis in adults (SpIn). Those patients with clinical suspicion of acute appendicitis and a negative scan should be observed until pain resolves or a repeat scan proves positive


  1. Orr RK, Porter D. Ultrasonography to evaluate adults for appendicitis: decision making based on meta-analysis and probabilistic reasoning. Academic Emergency Medicine 1995;2(7):644-650.
  2. Skaane P, Schistad O, Amland PF et al. Routine ultrasonography in the diagnosis of acute appendicitis: A valuable tool in daily practice? The American Surgeon 1997;63(11):937-942.
  3. Zielke A, Hasse C, Sitter H, et al. Influence of ultrasound on clinical decision making in acute appendicitis: A prospective study. EUR J SURG 1998;164(3):201-209.
  4. Chen SC. Chen KM. Wang SM. Chang KJ. Abdominal sonography screening of clinically diagnosed or suspected appendicitis before surgery. World Journal of Surgery. 1998 May;22(5):449-52.
  5. Franke C. Bohner H. Yang Q. Ohmann C. Roher HD. Ultrasonography for diagnosis of acute appendicitis: results of a prospective multicenter trial.Acute Abdominal Pain Study Group. World Journal of Surgery 1999 Feb;23(2):141-6.