2004;113;24PediatricsBarbara M. Garcia Pea, E. Francis Cook and Kenneth D. Mandl

Selective Imaging Strategies for the Diagnosis of Appendicitis in Children

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Selective Imaging Strategies for the Diagnosis of Appendicitis inChildren

Barbara M. Garcia Pena, MD, MPH*; E. Francis Cook, ScD; and Kenneth D. Mandl, MD, MPH

ABSTRACT. Background. We previously reported anappendiceal imaging protocol in which children withequivocal clinical presentations for acute appendicitisundergo ultrasonography (US) followed by computedtomography (CT). However, risk groups of children whowould benefit most from imaging studies have not beenestablished.

Objective. To define and test selective imagingguidelines to increase diagnostic accuracy and reduceunnecessary testing for children with suspected appen-dicitis.

Methods. We modeled outcomes under 3 differentmanagement guidelines. Patients were risk-stratified bya recursive partitioning analysis of a retrospective cohort.Subjects included children with equivocal presentationsof acute appendicitis evaluated between January 1996and December 1999. By using recursive partitioning, 3risk groups were identified: low, medium, and high riskfor acute appendicitis. Three imaging guidelines weredefined. Under the first guideline, representing standardclinical practice at Childrens Hospital Boston at the timeof the study, all children with equivocal signs and symp-toms for acute appendicitis undergo US first. If the US ispositive, the child proceeds to appendectomy. If the US isnegative, the child undergoes CT. Under guideline 2,low-risk children undergo US and, if negative, are dis-charged from the hospital. High-risk children undergoCT, and medium-risk children undergo US followed byCT. Under the third guideline, low-risk children undergono imaging and are admitted for observation. High-riskchildren proceed directly to appendectomy without im-aging studies. Medium-risk children undergo US fol-lowed by CT. Clinical outcomes and the number of im-aging studies performed were modeled under currentpractice and under each guideline.

Results. Identified were 1401 cases of equivocal ap-pendicitis; 958 (68.4%) with complete data. The mean agewas 11 4.3 years. Of 958 children, 588 (61.4%) had acuteappendicitis. One hundred forty-three patients were inthe low-risk group, defined as neutrophils 10 000/mm3,

guarding, and abdominal pain >13 hours. Of these, 202(90%) had appendicitis. Under guideline 1, there were 22negative appendectomies, 35 missed or delayed diag-noses, and 958 USs and 673 CT scans performed. Underguideline 2, there would have been 23 negative appen-dectomies, 36 missed or delayed diagnoses, and 733 USsand 637 CT scans performed. Under guideline 3, therewould have been 36 negative appendectomies, 37 missedor delayed diagnoses, and 590 USs and 412 CT scansperformed.

Conclusions. Selective imaging guidelines can reducethe number of radiographic studies performed with min-imal diminution in accuracy of diagnosis of pediatricappendicitis. Pediatrics 2004;113:2428; appendicitis,computed tomography, ultrasonography, selective imag-ing guidelines.

ABBREVIATIONS. US, ultrasonography; CT, computed tomogra-phy; WBC, white blood cell.

Accurate diagnosis of acute appendicitis in thepediatric population continues to pose a dif-ficult challenge to clinicians, because the ini-tial presentation of the disease is often obscure andclosely mimicked by other common childhood dis-eases.16 As a result, many children with suspectedappendicitis are admitted to the hospital for a periodof inpatient observation.710 However, the delayeddiagnosis of appendicitis may lead to complications,which in turn lead to increased morbidity and mor-tality.1114 In addition, it has been reported that anormal appendix is removed in 15% to 40% of chil-dren who undergo appendectomy.1517

Two diagnostic imaging modalities have providedclinicians with greater accuracy in diagnosing child-hood appendicitis. Ultrasonography (US) is widelyused in the pediatric population because it does notexpose patients to ionizing radiation and is noninva-sive.1821 However, it is highly operator-dependent,and the normal appendix is rarely visualized.22 Com-puted tomography (CT) is increasingly being used inchildren for the diagnosis of appendicitis. The use ofCT in children has increased 7-fold in the past 10years.23 It has been shown to be 94% to 99% accuratefor the diagnosis of pediatric appendicitis.2427 How-ever, many are concerned about the ionizing radia-tion, albeit small, associated with CT23,2830 and theinvasiveness of oral, intravenous, or rectal contrast inthe pediatric population.

Although diagnostic imaging modalities can bevery helpful in the diagnosis of appendicitis,31 theycan also increase the time to diagnosis, the ionizing

From the *Division of Emergency Medicine, Miami Childrens Hospital,Miami, Florida; Department of Epidemiology, Harvard School of PublicHealth, Boston, Massachusetts; and Division of Emergency Medicine, Chil-drens Hospital Boston, Boston, Massachusetts.Received for publication Feb 18, 2003; accepted May 9, 2003.This work was presented in part at the Society for Pediatric Research onMay, 2001 in Baltimore, MD.Address correspondence to Barbara M. Garcia Pena, MD, MPH, Division ofEmergency Medicine, Miami Childrens Hospital, 3100 SW 62nd Ave, Mi-ami, FL 33155. E-mail: barbara.pena@mch.comPEDIATRICS (ISSN 0031 4005). Copyright 2004 by the American Acad-emy of Pediatrics.

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radiation exposure, the utilization of hospital re-sources, as well as the discomfort of the child. Manyclinicians may be tempted to order studies for chil-dren who have symptoms of classic appendicitis ornonspecific acute abdominal pain, neither of whomshould necessarily require diagnostic imaging stud-ies. The identification of children who would benefitmost from imaging should occur based on their priorprobability of having appendicitis. The purpose ofthis investigation was to define and test selectiveimaging guidelines based on risk stratification toincrease diagnostic accuracy and reduce unnecessarytesting for children with suspected appendicitis.

METHODS

Study Subjects and DesignThe study was a recursive partitioning analysis of a retrospec-

tive cohort with subsequent development of guidelines and mod-eling of the outcomes under the guidelines. A cohort of childrenbetween 3 and 21 years old who were admitted to the hospitalward or operating room of Childrens Hospital Boston with equiv-ocal presentations for acute appendicitis between January 1996and December 1999 were identified retrospectively. All patientswho were admitted to the hospital for suspected appendicitiswere eligible. Patients with equivocal presentations were definedas those children with concerning but not classic signs or symp-toms for acute appendicitis. Childrens Hospital Boston is a large,urban, pediatric teaching hospital with an emergency departmentthat sees 50 000 patient visits and a general surgical service thatperforms 4000 operations annually. All radiographic studies areperformed by either pediatric radiology attendings or fellows 24hours a day. This study was approved by the institutional reviewboard of Childrens Hospital Boston.

Patients evaluated for acute appendicitis were identifiedthrough a query of the hospital database selecting patients withInternational Classification of Diseases, 9th Revision (ICD-9) codes forappendicitis, perforated appendicitis, appendectomy, and abdom-inal pain. A single reviewer using a standardized data collectiontool abstracted data on symptoms, clinical examination findings,radiographic studies, and pathology reports. Final diagnoses weredetermined by pathologic examination of the appendix in thosechildren who were managed operatively and by clinical follow-upin those children managed nonoperatively.

Stratification of GroupsUsing CART 3.6, we conducted a recursive partitioning analy-

sis to divide the cohort into children at high, low, and medium riskfor appendicitis. Variables entered into the model included age,gender, hours of abdominal pain, nausea or vomiting, diarrhea,anorexia, temperature 38.0C, right lower quadrant tenderness,rebound tenderness, guarding, rectal tenderness, stool occultblood, white blood cell (WBC) count 10 000/mm3, neutrophilcount, and bands 5%. Ten-fold cross-validation and the Ginimethod for classification trees were used. We used the minimum-cost tree regardless of size for the standard error rule, and allsurrogates counted equally. Missing a case of appendicitis wasweighted as 10 times worse than diagnosing appendicitis in achild that did not have it.

Imaging GuidelinesWe defined, a priori, 3 imaging guidelines for the diagnosis of

acute appendicitis. Guideline 1 represents standard clinical prac-tice at Childrens Hospital Boston at the time of the study peri-od.24,32 In that strategy, all children with equivocal signs andsymptoms for appendicitis undergo US first. If the US is positive,the child proceeds to the operating room for appendectomy. If theUS is negative, the child then undergoes CT scan. If the CT ispositive for appendicitis, the child undergoes appendectomy. Ifthe CT is negative, the child is discharged from the hospital withclose follow-up. Outcomes under guideline 1 are all measured inclinical data.

Guidelines 2 and 3 are applied hypothetically to the cohort, andoutcomes are modeled. These guidelines implement more selec-

tive imaging strategies aimed at reducing the use of radiographyaccording to risk assessments. Under guideline 2, the low-riskpatients undergo US only. If the study is negative for appendicitis,the child is discharged from the hospital. If the study is positivefor appendicitis, the child proceeds to appendectomy. The high-risk patients undergo CT only. If the scan is negative, the child isdischarged from the hospital. If the scan is positive, the childundergoes appendectomy. The medium-risk children default tothe protocol for guideline 1 (standard clinical practice) where bothUS and CT are used.

In guideline 3, low-risk patients undergo no imaging while inthe emergency department and are admitted for inpatient obser-vation. Children at high risk for appendicitis receive no imagingand proceed directly to appendectomy. Again, medium-risk pa-tients default to the protocol under guideline 1.

Modeling of OutcomesBy using the highest known sensitivities, specificities, positive

predictive values, and negative predictive values of US, CT, andUS followed by CT, the number of negative appendectomies andmissed or delayed diagnoses of appendicitis were modeled foreach strategy. The number of US and CT scans performed werealso calculated based on how patients flowed through each guide-line.

Statistical AnalysisDescriptive statistics were calculated with SPSS 7.5 for Win-

dows (SPSS Inc, Chicago, IL). Recursive partitioning was per-formed with CART 3.6 for Windows (Salford Systems, Inc, SanDiego, CA).

RESULTSDuring the study period, 1401 children were iden-

tified, 958 of which (63.4%) had complete data. Themean age of the cohort was 11 4.3 years. Therewere 526 of 958 (54.9%) males. More than half (588 of958 [61.4%]) had acute appendicitis.

Stratification of GroupsRecursive partitioning analysis identified a low-

risk group of 143 patients. These children all had acomplete blood count with neutrophils 67%, bands5%, and no guarding on physical examination. Fif-teen of these 143 (10.5%) patients had appendicitis(Fig 1). A high-risk group of 225 patients was iden-tified. These patients had a complete blood countwith neutrophils 67%, WBC count 10 000/mm3,guarding on physical examination, and a history ofabdominal pain 13 hours. Of 225 children in thehigh-risk group, 202 (90%) had appendicitis (Fig 1).The remainder of the patients (590 of 958 [61.6%])comprised the medium-risk group. Appendicitis wasdiagnosed in 371 of 590 (62.9%) children in thisgroup.

Imaging GuidelinesFig 2 shows the actual data from the children

managed under guideline 1 (which was standardpractice during the period studied). More than half(588 of 958 [61.4%]) of the patients had acute appen-dicitis. The correct diagnosis was made in 901 of 958(94%) children. Of the 370 patients without appendi-citis, there were 22 (5.9%) negative appendectomies.

Outcomes under guidelines 2 and 3 are shown inFig 3. Under guideline 2, there would be 36 cases(6.1%) of missed or delayed diagnosis of acute ap-pendicitis and 23 (6.2%) cases of negative appendec-tomies. The correct diagnosis would be made in 899

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of 958 (93.8%) patients. Those children undergoingthe protocol under guideline 3 would have had 37(6.3%) cases of missed or delayed diagnosis of acuteappendicitis and 36 (9.7%) cases of negative appen-dectomies. The correct diagnosis would be made in885 of 958 (92.4%) patients.

Table 1 demonstrates the clinical outcomes asstated above and the number of radiographic studiesfor the current US-CT strategy and the proposedguidelines. Under guideline 1, there were 958 USsand 673 CT scans performed. There would have been733 USs and 637 CT scans performed under guide-line 2 and 590 USs and 412 CT scans performedunder guideline 3.

Under guideline 1, one would have to perform30.6 CT scans and 43.5 USs for each case of negativeappendectomy avoided and 19.2 CT scans and 27.4USs for each case of missed or delayed appendicitisprevented. Under guideline 2, one would have toperform 27.7 CT scans and 31.9 USs for each case ofnegative appendectomy avoided and 17.7 CT scansand 20.4 USs for each case of missed or delayedappendicitis prevented. Last, under guideline 3, 11.4CT scans and 16.4 USs would have to be performed

to avoid one case of negative appendectomy and 11.1CT scans and 15.9 USs to prevent one case of missedor delayed appendicitis.

DISCUSSIONThe diagnosis of acute appendicitis in the pediatric

population remains difficult. Delayed diagnoses andsubsequent appendiceal perforations with their con-comitant complications continue to present a chal-lenge for physicians even with the advent of im-proved diagnostic imaging techniques. In addition,the negative pediatric appendectomy rates across theUnited States remain relatively high. The use of USand CT has increased exponentially over the pastdecade and has provided a great increase in theaccuracy of the diagnosis of acute appendicitis. How-ever, there is a danger that radiographic studies maybe obtained even when they may add little to theclinical impression based on history, physical exam-ination, and basic laboratory studies. The use of CTin pediatric patients has become particularly con-cerning because of the potential long-term risks ofionizing radiation. Hence, protocols are required toreduce the number of unnecessary radiographicstudies being performed for the diagnosis of acuteappendicitis.

In this investigation, we have described 3 distinctrisk groups of children with suspected acute appen-dicitis. Children with neutrophils67%, bands5%,and no guarding on physical examination comprisea group of patients at low risk for appendicitis,whereas children with neutrophils 67%, WBCcount 10 000/mm3, guarding on physical examina-tion, and abdominal pain 13 hours comprise agroup of patients at high risk for appendicitis. Theremainder of the children comprised the medium-risk group. Using these risk groups, we compared 3selective imaging guidelines and calculated the num-bers of missed or delayed diagnoses of appendicitis,negative appendectomies, and USs and CT scansperformed for each strategy. We have shown thatthese guidelines for selective imaging based on riskstratification may reduce the number of radiographicstudies performed for diagnosing appendicitis with aminimal increase in the negative appendectomy andmissed diagnosis of appendicitis rates.

Limitations of this study include the hypotheticalnature of proposed guidelines 2 and 3. The effective-ness of these guidelines in clinical practice is un-known and thus must be confirmed with prospectiveinvestigation. Second, there are many more manage-ment strategies using selective imaging protocolsthat can be explored, and those chosen may not bethe ideal strategies for managing suspected appen-dicitis in many institutions. However, to model 3strategies would be unwieldy in the scope of a singleinvestigation. Third, a second data set was not avail-able to validate the risk groups that were created bythe regression tree. However, the data were vali-dated by the cross-validation methods provided byCART.

Although both the number of USs and CT scansperformed were markedly decreased, the number ofnegative appendectomies and cases of missed or de-

Fig 1. Low-risk and high-risk groups determined by recursivepartitioning. The low-risk group is depicted on the left and thehigh-risk group is on the right.

Fig 2. Guideline 1 (US followed by CT).

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layed diagnoses of appendicitis slightly increased inboth proposed selective imaging strategies. Underguideline 1, one would have to perform 11.8 CTscans and 16.8 USs to prevent one case of incorrectdiagnosis of appendicitis (either one negative appen-dectomy or one missed or delayed diagnosis). Underguideline 2, one would have to perform 10.8 CTscans and 12.4 USs, and under guideline 3, onewould have to perform 5.6 CT scans and 8.1 USs toprevent an incorrect diagnosis. Hence, in choosingbetween guidelines 2 and 3, one would have toweigh the increase in negative appendectomies from23 under guideline 2 to 36 under guideline 3 againstthe marked decrease in the number of USs and CTscans performed under guideline 3.

We have shown that selective imaging guidelinesin low- and high-risk groups for suspected appendi-citis may reduce the number of radiographic studiesperformed while keeping the negative appendec-tomy and missed diagnosis of appendicitis rates rel-atively stable. Selective imaging guidelines can re-duce the number of radiographic studies performedwith minimal diminution in the accuracy of diagno-sis of pediatric appendicitis.

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TABLE 1. Clinical Outcomes and Number of Radiographic Studies for Proposed Guidelines

Guideline 1 Guideline 2 Guideline 3

Negative appendectomies 22 23 36Missed or delayed diagnoses 35 36 37No. of USs performed 958 733 590No. of CT scans performed 673 637 412

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SPEED EATING A NEW SPORT?

Speed eating has been around in one form or another for the better part of acentury, practiced informally at country fairs and fraternity houses. In the last fewyears, however, it has been transformed into a national competitive circuit com-plete with television coverage, prize money and its own governing body, theInternational Federation of Competitive Eating. The federation oversees 150 eventsand counts 3000 eaters in its register. Its competitions boast strict rules andregulations vomiting leads to automatic disqualification; any food in the mouthat the buzzer counts.

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2004;113;24PediatricsBarbara M. Garcia Pea, E. Francis Cook and Kenneth D. Mandl

Selective Imaging Strategies for the Diagnosis of Appendicitis in Children

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