Diagnostic Accuracy of Noncontrast Computed Tomography for Appendicitis in Adults: A Systematic Review

doi:10.1016/j.annemergmed.2009.06.509

Annals of Emergency Medicine

Volume 55, Issue 1, January 2010, Pages 51-59.e1

https://doi.org/10.1016/j.annemergmed.2009.06.509 Get rights and content

Study objective

We seek to determine the diagnostic test characteristics of noncontrast computed tomography (CT) for appendicitis in the adult emergency department (ED) population.

Methods

We conducted a search of MEDLINE, EMBASE, the Cochrane Library, and the bibliographies of previous systematic reviews. Included studies assessed the diagnostic accuracy of noncontrast CT for acute appendicitis in adults by using the final diagnosis at surgery or follow-up at a minimum of 2 weeks as the reference standard. Studies were included only if the CT was completed using a multislice helical scanner. Two authors independently conducted the relevance screen of titles and abstracts, selected studies for the final inclusion, extracted data, and assessed study quality. Consensus was reached by conference, and any disagreements were adjudicated by a third reviewer. Unenhanced CT test performance was assessed with summary receiver operating characteristic curve analysis, with independently pooled sensitivity and specificity values across studies.

Results

The search yielded 1,258 publications; 7 studies met the inclusion criteria and provided a sample of 1,060 patients. The included studies were of high methodological quality with respect to appropriate patient spectrum and reference standard. Our pooled estimates for sensitivity and specificity were 92.7% (95% confidence interval 89.5% to 95.0%) and 96.1% (95% confidence interval 94.2% to 97.5%), respectively; the positive likelihood ratio=24 and the negative likelihood ratio=0.08.

Conclusion

We found the diagnostic accuracy of noncontrast CT for the diagnosis of acute appendicitis in the adult population to be adequate for clinical decisionmaking in the ED setting.

Introduction

Acute appendicitis is frequently in the differential diagnosis of patients presenting to the emergency department (ED) with right lower quadrant abdominal pain. Unfortunately, the diagnosis is difficult, with the classic presentation of periumbilical pain followed by nausea and vomiting, with migration of pain to the right lower quadrant occurring in only 50% to 60% of patients with appendicitis.¹ An increased leukocyte count occurs in 70% to 90% of cases but is nonspecific because it can occur in other disease processes.² Although there has been some conflicting evidence, the use of computed tomography (CT) has been reported to significantly reduce the negative appendectomy rate in many studies.3, 4, 5, 6 Institutions use different combinations of oral, intravenous, and rectal contrast, as well as noncontrast protocols. Noncontrast CT is particularly appealing in today's crowded EDs because there is no delay caused by waiting for oral contrast transit, no risk of contrast-induced nephropathy, and no risk of allergic reaction. However, the use of noncontrast CT has been controversial because of concerns about diagnostic accuracy and the need for repeated scanning with contrast in a subset of patients when the interpretation is inconclusive.7, 8 The goal of this systematic review was to assess the evidence for the use of noncontrast CT for the diagnosis of acute appendicitis among adults.

Section snippets

Materials and Methods

The clinical question addressed in this systematic review is, in adult patients presenting to the ED with acute abdominal pain and suspected of having acute appendicitis, what are the test characteristics of noncontrast helical CT? A written systematic review protocol was developed to directly address this clinical question and was reviewed and agreed upon by all authors a priori.

All relevant electronic databases were searched for studies assessing the accuracy of noncontrast helical

Results

There was good agreement between the 2 reviewers (V.H., J.A.D.) for the relevance screen of the 1,161 titles identified in the MEDLINE, Cochrane, and EMBASE databases (κ=0.62). The comprehensive search yielded a total of 1,258 publications (Figure 1). After adjudication of the relevance search, a full article review was completed on the remaining 32 articles. Upon full article review, 15 studies did not meet our inclusion criteria for various reasons such as inappropriate patient spectrum,

Limitations

There were a number of studies that were omitted from our systematic review after we were unable to confirm length of follow-up with the authors.35, 39, 40 If we had been able to confirm adequate follow-up, the addition of these studies to our meta-analysis may have affected our overall estimates of sensitivity and specificity.

The inconsistency of reporting inconclusive CT results is an important limitation because at least 1 study has demonstrated a 41% incidence of acute appendicitis with

Discussion

Acute appendicitis remains the most common cause of acute abdominal pain requiring urgent surgery.⁴⁴ Despite the high prevalence of appendicitis, the diagnosis is still problematic and perforation can occur within 24 hours of the onset of symptoms.¹² The lifetime incidence of appendicitis in the Western world is 6.7% for females and 8.6% for males, but the lifetime chance of appendectomy is 23.1% and 12.0%, respectively.⁴⁷ Traditionally, a high negative appendectomy rate of 10% to 20% has been

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ACR Appropriateness Criteria® Right Lower Quadrant Pain: 2022 Update
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This document focuses on imaging in the adult and pregnant populations with right lower quadrant (RLQ) abdominal pain, including patients with fever and leukocytosis. Appendicitis remains the most common surgical pathology responsible for RLQ abdominal pain in the United States. Other causes of RLQ pain include right colonic diverticulitis, ureteral stone, and infectious enterocolitis. Appropriate imaging in the diagnosis of appendicitis has resulted in decreased negative appendectomy rate from as high as 25% to approximately 1% to 3%. Contrast-enhanced CT remains the primary and most appropriate imaging modality to evaluate this patient population. MRI is approaching CT in sensitivity and specificity as this technology becomes more widely available and utilization increases. Unenhanced MRI and ultrasound remain the diagnostic procedures of choice in the pregnant patient. MRI and ultrasound continue to perform best in the hands of the experts.
The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.
Adult appendicitis: Clinical practice guidelines from the French Society of Digestive Surgery and the Society of Abdominal and Digestive Imaging
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The French Society of Digestive Surgery (SFCD) and the Society of Abdominal and Digestive Imaging (SIAD) have collaborated to propose recommendations for clinical practice in the management of adult appendicitis.
An analysis of the literature was carried out according to the methodology of the French National Authority for Health (HAS). A selection was performed from collected references and then a manual review of the references listed in the selected articles was made in search of additional relevant articles. The research was limited to articles whose language of publication was English or French. Articles focusing on the pediatric population were excluded. Based on the literature review, the working group proposed recommendations whenever possible. These recommendations were reviewed and approved by a committee of experts.
Recommendations about appendicitis in adult patients were proposed with regard to clinical, laboratory and radiological diagnostic modalities, treatment strategy for uncomplicated and complicated appendicitis, surgical technique, and specificities in the case of macroscopically healthy appendix, terminal ileitis and appendicitis in the elderly and in pregnant women.
These recommendations for clinical practice may be useful to the surgeon in optimizing the management of acute appendicitis in adults.
Accuracy of Nonenhanced CT vs Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults
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Citation Excerpt :
CT is highly sensitive and specific for diagnosing acute appendicitis, with a respective pooled sensitivity and specificity of 96% and 92%.21 Generally, CT is performed with the administration of intravenous contrast media; however, recent studies—including a systematic review by Hlibczuk et al22 and a meta-analysis by Xiong et al23—indicated comparable results for CT without contrast. A few studies directly compared the accuracy between the 2 techniques.
Acute appendicitis is one of the most common causes of acute abdominal pain requiring emergency intervention. It is often difficult for the clinician to make an accurate diagnosis due to nonspecific and overlapping clinical symptoms. Computed tomography (CT) has become the imaging modality of choice for the evaluation of suspected acute appendicitis. The main purpose of our study was to compare nonenhanced CT (NECT) with contrast-enhanced CT (CECT) for the diagnosis of acute appendicitis.
A total of 140 patients were enrolled in the study. Two abdominal radiologists—masked to both the clinical information and the final diagnosis—retrospectively reviewed the computed tomographic findings and made an imaging diagnosis based on (1) NECT only, (2) CECT only, and (3) both NECT and CECT. With the final diagnosis as the reference standard, the accuracy of each CT technique was estimated.
The respective sensitivity, specificity, and accuracy for NECT, CECT, and NECT + CECT for the diagnosis of acute appendicitis were 80.7%, 86.7%, and 84.3%; 86.0%, 81.9%, and 83.6%; and, 87.7%, 80.7%, and 83.6%. There was no significant difference in the diagnosis of acute appendicitis among the 3 techniques. In order to make a correct diagnosis, the presence of at least 3 imaging findings for NECT or at least 4 for CECT had the best diagnostic accuracy. We also found that 9.25 mm was the optimal cut-off threshold for the detection of patients with acute appendicitis.
Our study allowed direct comparison between NECT, CECT, and NECT + CECT combined. There was no difference in the ability of each CT technique for diagnosing patients with acute appendicitis. For a patient whom iodinated contrast media is contraindicated or a patient who has an increased risk of severe adverse reaction, we would encourage the use of NECT because it provides comparable diagnostic accuracy without further exposing such patient to the contrast media.
Systematic Review: The Role of Intravenous and Oral Contrast in the Computed Tomography Evaluation of Acute Appendicitis
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Citation Excerpt :
Eight studies, six prospective and two retrospective, met criteria for review (Table 5). These results are similar to a previous high-quality systematic review published in 2010 (2). This review adds one additional study published in 2013 with results similar to the other included studies (9).
This systematic review provides practicing emergency physicians updated information regarding the role of oral and intravenous contrast in the computed tomography (CT) evaluation of acute appendicitis.
A PubMed literature search was conducted from January 1, 1996 to December 31, 2018 and limited to human clinical trials written in English with relevant keywords. High-quality studies were identified and then underwent a structured review. Recommendations are made based on the literature review.
Fifty-seven articles met criteria for rigorous review, of which 14 were appropriate for citation in this review. Excellent evidence shows that oral contrast does not improve the test characteristics of CT with intravenous contrast (IVCT) in the evaluation of adults suspected of having acute appendicitis. Good evidence shows that noncontrast abdominal CTs have excellent test characteristics for this same group of patients.
Considering its downsides and lack of utility, the medical literature does not support using oral contrast in the evaluation of acute appendicitis. There is no direct evidence showing that IVCT is better than a noncontrast CT in the evaluation of acute appendicitis; however, the available literature is consistent with slightly better test characteristics for IVCTs. Still, if IVCT cannot be obtained in a timely manner, noncontrast CTs are extremely accurate in detecting this disease.
Use of oral contrast for CT scanning and time to diagnosis and treatment of acute appendicitis
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: Supervising editor: Allan B. Wolfson, MD

: Author contributions: VH and JAD conceived the study and reviewed and assessed all relevant studies. VH, JAD, and MDB supervised the conduct of the systematic review and data collection. VH, JAD, and LF conducted the search of all relevant electronic databases, meeting abstracts, and bibliographies. ZJ and MDB provided statistical advice. VH, JAD, ZJ, and MDB analyzed the data. VH and JAD drafted the article, and all authors contributed substantially to its revision. VH takes responsibility for the paper as a whole.

: Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.

: Earn CME Credit: Continuing Medical Education is available for this article at: http://www.ACEP.EMedHome.com.

: Reprints not available from the authors.

: Publication date: Available online September 5, 2009.

: Please see page 52 for the Editor's Capsule Summary of this article.

: Provide feedback on this article at the journal's Web site, www.annemergmed.com.

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General medicine/original researchDiagnostic Accuracy of Noncontrast Computed Tomography for Appendicitis in Adults: A Systematic Review

Study objective

Methods

Results

Conclusion

Introduction

Section snippets

Materials and Methods

Results

Limitations

Discussion

Am J Gastroenterol

J Am Coll Surg

Am J Emer Med

Am J Surg

J Clin Epidemiol

J Clin Epidemiol

Am J Surg

J Emerg Med

Am J Surg

Am J Surg

J Clin Epidemiol

Appendicitis at the millennium

Radiology

Suspected appendicitis

N Engl J Med

Effect of computed tomography of the appendix on treatment of patients and use of hospital resources

N Engl J Med

Impact of helical computed tomography in clinically evident appendicitis

Emerg Med J

Suspected acute appendicitis: nonenhanced helical CT in 300 consecutive patients

Radiology

US or CT for diagnosis of appendicitis in children and adults?a meta-analysis

Radiology

Systematic review: computed tomography and ultrasonography to detect acute appendicitis in adults and adolescents

Ann Intern Med

Diagnosis of appendicitis in adults by ultrasonography or computed tomography: a systematic review and meta-analysis

Int J Technol Assessm Health Care

Systematic reviews of diagnostic test accuracy

Ann Intern Med

The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews

BMC Med Res Methodol

Evidence of bias and variation in diagnostic accuracy studies

CMAJ

A methodological review of how heterogeneity has been examined in systematic reviews of diagnostic test accuracy

Health Technol Assess

Review Manager (RevMan) [computer program]. Version 5.0.16

Challenges in systematic reviews of diagnostic technologies

Ann Intern Med

Imaging for suspected appendicitis: negative appendectomy and perforation rates

Radiology

Radiodiagnosis of acute appendicitis

Khirurgiia (Mosk)

The value of unenhanced CT in the diagnosis of acute appendicitis

Sao Paulo Med J (Rev Paul Med)

General medicine/original research
Diagnostic Accuracy of Noncontrast Computed Tomography for Appendicitis in Adults: A Systematic Review