Reliability and reproducibility of the American Association for the Surgery of Trauma scaling for renal injury and impact on radiologic follow-up

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ORIGINAL ARTICLE

Reliability and reproducibility of the American Association for the Surgery of Trauma scaling for renal injury and impact on radiologic follow-up

Fiabilité et reproductibilité de la classiﬁcation de l’American Association for the Surgery of Trauma et impact sur le suivi radiologique des traumatismes rénaux

Q.-B. Phan

^a^,∗

, E. Mourey

^a

, L. Estivalet

^b

, B. Delattre

^a

, F. Bardet

^a

, O. Chevallier

^b

, D. Louis

^c

, L.S. Aho

^d

,

R. Loffroy

^b

, L. Cormier

^a

aUrologie,CHUFranc¸ois-Mitterand,Dijon,France

bRadiologie,CHUFranc¸ois-Mitterand,Dijon,France

cChirurgiepédiatrique,CHUFranc¸ois-Mitterand,Dijon,France

dÉpidémiologie,CHUFranc¸ois-Mitterand,Dijon,France

Received1stJuly2017;accepted26September2017 Availableonline7November2017

KEYWORDS CTscanner;

Kidney;

Scale;

Subjectivity;

Trauma

Summary

Introduction.—TheAmericanAssociationfortheSurgeryofTrauma(AAST)OrganInjuryScale (OIS)isthemostusedclassiﬁcationforrenaltrauma.Itdeterminestheradiologicmonitoring, onlyrecommendedforhigh-gradeinjuries.Theaimofthisstudywastoassessthesubjectivity ofAASTscalinganditsimpactonshort-termfollow-up.

Methods.—We retrospectivelyreviewedallpatients withbluntrenalinjuriesadmittedata universityhospitalbetween2010and2015.ComputedTomography(CT)scanwereanalyzedand injuriesgradedaccordingtoAASTOISindependentlybyaseniorradiologist,aseniorurologist

∗Correspondingauthor.

E-mail addresses: quangbao.phan@gmail.com, quangbao.phan@chu-dijon.fr (Q.-B. Phan), eric.mourey@chu-dijon.fr (E. Mourey), louis.estivalet@gmail.com (L. Estivalet), bendelattre@gmail.com (B. Delattre), ﬂorian.bardet@chu-dijon.fr (F. Bardet), olivier.chevallier54@gmail.com (O. Chevallier), ldavid06@hotmail.com (D. Louis), ludwig.aho@chu-dijon.fr (L.S. Aho), romaric.loffroy@chu-dijon.fr(R.Loffroy),luc.cormier@chu-dijon.fr(L.Cormier).

https://doi.org/10.1016/j.purol.2017.09.013

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whowasblindtoclinicaldataandaresidenturologist.Gradingdisagreementswereanalyzed collegiallytoobtainaﬁnalrating.TheagreementofAASTscalingwasevaluatedthroughthe Cohen’sKappacoefﬁcient.

Results.—Ninety-sevenpatientshad101renalinjuries:lowgradein58.4%(11.9%gradeI,17.8%

gradeII,28.7%gradeIII)andhighgradein41.6%ofcases(23.6%gradeIVand17.8%gradeV).

TheagreementwasfairwithKappacoefficientat0.36.Theagreementwasmoderateinseverity sub-divisionanalysis(loworhighgrade):Kappacoefficientat0.59.Therewasadisagreement in49.5%betweentheseniorurologist’sandtheseniorradiologist’sratings.Thosedifferences broughttoaseveritygroupchangeandradiologicfollow-upmodificationin34%(n=17).

Conclusion.—AASTOISforrenaltraumasuffersfromsubjectivitybutisimprovedbyseverity sub-groupanalysis.Thissubjectivityinﬂuencestheradiologicfollow-upbutcouldbereduced bycollegiaterating.

Levelofevidence.— 4.

MOTSCLÉS Classiﬁcation; Rein;

Scanner; Subjectivité; Traumatisme

Résumé

Introduction.—L’AmericanAssociationfor theSurgery ofTrauma(AAST) Organ InjuryScale (OIS)estla classiﬁcation des traumatismesrénauxla plusutilisée.Elle conditionnele suivi radiologiquedeslésionsdehautgrade.L’étudeévaluelasubjectivitédelaclassiﬁcationAAST etsonimpactsurlesuiviradiologique.

Matériel.—ÉtuderétrospectivedestraumatismesrénauxfermésprisenchargedansunCHU entre2010et 2015. Le scanneraétérelu etla lésion rénalegradée selonla classification AASTindépendammentparunradiologue,unurologueenaveugledelacliniqueetuninterne d’urologie.Uneclassificationfinaleaétéobtenueaprèsrelecturecollégialedescasdiscordants.

L’accorddeclassiﬁcationAASTaétéévaluégrâceaucoefﬁcientKappa.

Résultats.—Quatre-vingt-dix-neufpatientsontprésenté101lésionsrénales:debasgradedans 58,4%(gradeI11,9%,gradeII17,8%,gradeIII28,7%)etdehautgradedans41,6%(grade IV23,6%,gradeV17,8%).L’accordentreclassificationsétaitacceptable:coefficientKappa de0,36.L’accordétaitmodéréenanalyseparsous-groupesdesévérité:coefficientKappaà 0,59.Onretrouvaitundésaccordentrelesclassificationsduradiologueetdel’urologuedans 49,5%.Cesdiscordancesentraînaientunchangementdegroupedesévéritéetdesurveillance radiologiquedans34%(n=17).

Conclusion.—LaclassiﬁcationAASTestsubjectivemaisamélioréeenanalysedesous-groupe desévérité.Cettesubjectivitéentraînedesvariationsdusuiviradiologiquemaispourraitêtre limitéeparuneanalysecollégialedesscanners.

Niveaudepreuve.— 4.

Introduction

Surgicalmanagementwithahigh riskofnephrectomywas previously the main management of renal trauma [1]. In ordertoavoid renal unitloss andtopreserve renalfunc- tion,conservativemanagementhasrisen.Itwasallowedby improvementsofinterventionalradiology,endourologyand ComputedTomography(CT)scan.

CTscanisthegoldstandardforinitialevaluationofrenal injuryinstable[2,3]orevenunstablepatients[4].Itallows anaccurateassessmentoftherenalinjurytypeandexten- sion.The American Associationfor the Surgery ofTrauma (AAST)OrganInjuryScale(OIS)isthemostusedclassiﬁcation tosortkidneyinjuries (Appendix1)[5].This 5-gradescale isapredictivewaytoassessmorbidity,mortality,needfor surgeryandfornephrectomywithincreasinggrade[6—8].

RenaltraumamanagementdependsonCTscanﬁndings.

Indeed,AAST scale has a central placein modern management algorithms. According tointernational guidelines, high-gradeinjuriesshouldbetreated,ifpossible,conserva- tivelyandshouldhaveacontrolCTscan48—96hafterthe traumatominimizetheriskofmissedcomplications[2,3].

However,usingAASTOIScouldbedifﬁcultsinceCTscan analysisissubjective [6,9]. Forexample, itcouldbehard todistinguishagradeVinjuryfromakidneywithmultiples gradeIIIorIVinjuries(Fig.1).

WehypothesizethattheAASTgrading forrenaltrauma has signiﬁcant interpersonal variability. A rating mistake could drive to an inadequate radiologic monitoring and potentialmorbidity.The principalaim ofthestudywasto assessthesubjectivityofAASTOISratingandtheimpacton radiologicmonitoring.

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Figure1. MultiplesgradeIIIandIVinjuriesorgradeVinjury?

Material and methods

After obtaining approval from the Institutional Review Board,westudied aretrospective cohort ofpatients with abluntrenalinjuryinitiallyevaluatedbyCTscan,admitted toouruniversityhospitalbetween2010and2015.

Toobtainahomogeneousgroup,weexcludedpenetrating renalinjuries.CTscanimaging(arterialandvenousphases, delayed imaging at the discretion of the radiologist) was obtained after injection of intravenous contrast material usingapowerinjector.

Patientswereidentifiedthroughtheadministrativedata andourdatabase.Weanalyzedthepatient’sdemographics (age, sex, body mass index), trauma mechanism (vehi- cle crash, pedestrian accident, fall or assault), renal and associated injuries, and radiologic monitoring during hospital stay. A follow-up CT scan was performed in case of clinical signs of complications (e.g., fever, worsening flank pain, ongoing bleeding). If the patient was asymptomatic, a control CT scan was realized five daysafter the trauma irrespective of renal injury grade.

We also analyzed the emergency interventions at admis- sion and the urological complications during the hospital stay.

WeusedAASTOIStoevaluatetherenalinjuryseverity.

The initialCT scanwasretrospectivelyanalyzed indepen- dentlybythreeraters:aresidenturologist,aseniorurologist skilledinrenalpathologyandaseniorradiologist.Thetwo seniorphysicianswereblindtotheclinicaldata.Eachcaseof gradingdisagreementwasanalyzedcollegiallybythethree initialphysicianstoﬁndaconsensusandobtainaﬁnalAAST rating.

Forstatistical analysis,we analyzed the AAST 5 levels grading,thenweclassiﬁedthepopulation intotwogroups according to the renal injury severity: low-grade group (gradesItoIII)andhigh-gradegroup(gradesIVandV)[9—13]

inordertoevaluatetheradiologicfollow-up.

Statistical analysiswasperformed usingEpiInfo^TM 6.0 (Centers of Disease Control). The reproducibility of AAST scaling was evaluated by Cohen’s Kappa coefficient with confidenceinterval (CI)tomeasurethe inter-rater agreement.The coefficient value is included between0 and1.

Thenearerto1istheKappacoefﬁcient,thehigheristhe agreementasshowninAppendix2[14].

Table1 Demographic data, trauma mechanism and emergencytreatment.

Totaln(%)

n 97

Age(years) 34.5(2—86)

BMI(kg/m²) 23.1(14—42)

Sex

Men 71(73%)

Women 26(27%)

Mechanism

Vehiclecrash 56(58%)

Car 17(18%)

Two-wheeler 36(37%)

Pedestrianaccident 3(3%)

Fall 31(32%)

Assault 10(10%)

Emergencyprocedure

Renalexploration 0

Nephrectomy 0

Endovasculartreatment 10(10%) Proximalembolization 3(3%) BMI:bodymassindex.

Results

Afterdatacollection, 123patients withbluntrenalinjury diagnosiswereincluded.Weexcluded26patientsforadmin- istrativedatamistakesin diagnosiscodeorinitialCTscan unavailable. We analyzed 97 patients who presented 101 blunt renal injury. Demographic data, trauma mechanism andemergencyinterventionsaredescribedinTable1.

TheAASTscalingforeachofthe3ratersispresentedin Table2.Theﬁnalscalingfoundrespectively58.4%and41.6%

oflowandhigh-graderenalinjury.TheKappacoefficientwas 0.36[0.24—0.47]betweenthethreeraters.Thedistribution ofeachrater’sAASTscalinghasbeencomparedtothefinal scalingthroughtheCohen’sKappacoefficient(Table2).

Kappa coefﬁcient was 0.5 between senior radiologist andseniorurologist(CI=[0.40—0.59]);0.71betweensenior urologist and resident urologist (CI=[0.61—0.82]);

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Table2 Inter-ratervariabilityofAASTscaling.

AASTrater AASTgraden(%) AgreementKappacoefﬁcient(CI)

I II III IV V

Seniorradiologist 7(6.9%) 23(22.8%) 35(34.7%) 17(16.8%) 19(18.8%) 0.73[0.63—0.83]

Seniorurologist 21(20.8%) 14(13.9%) 19(18.8%) 37(36.6%) 10(9.9%) 0.55[0.45—0.65]

Residenturologist 22(21.8%) 18(17.8%) 30(29.7%) 28(27.7%) 3(3.0%) 0.46[0,36—0,56]

Finalscaling 12(11.9%) 18(17.8%) 29(28.7%) 24(23.8%) 18(17.8%) 0.36[0.25—0.47]

CI:conﬁdenceinterval.

Table3 Inter-ratervariabilityofAASTscalinginseveritysubgroupanalyze.

AASTrater AASTseveritysubgroup AgreementKappacoefﬁcient(CI)

Lowgrade Highgrade

Seniorradiologist 65(64.4%) 36(35.6%) 0.85[0.66—1,04]

Seniorurologist 54(53.5%) 47(46.5%) 0.78[0.59—0.97]

Residenturologist 70(69.3%) 31(30.7%) 0.72[0.54—0.91]

Finalscaling 59(58.4%) 42(41.6%) 0.59[0.48—71]

CI:conﬁdenceinterval.

0.35 between senior radiologist and resident urologist (CI=[0.26—0.44]).

In severity subgroup analysis, the agreement is higher (Table3).Kappacoefﬁcientwas0.59[0.48—0.71]between thethreeraters;0.8betweenseniorradiologistandsenior urologist(CI=[0.59—1]);0.79betweenseniorurologistand resident urologist (CI=[0.60—0.99]); 0.70 between senior radiologistandresidenturologist(CI=[0.50—0.91]).

Therewasadisagreementin50cases(49.5%)between theseniorurologist’sandtheseniorradiologist’sratings.The AASTscalinggapwasmainlyof1gradein82%,2gradesin 12%andatleast3gradesin6%.Thedifferencesconcerned31 lowgradeand19high-gradeinjuries.Thosedisagreements broughttoaseveritysubgroupchangein34%(n=17)incom- parisontoﬁnalscalinganddrovetotheoreticalmodiﬁcation ofradiologicmonitoring.

Among the 17 cases of severity subgroup change, 4 patients had aurological complication of their trauma. A patient presented a nephritic colic due a ureteral blood clottreatedbyretrogradeureteralstentingonday1.Two patientsunderwentanongoingbloodlosswithnecessityof angioembolisation(respectivelyonday2andday17).The lastpatientpresented an unexplained feveronday 4due toamisseddiagnosedinjuryofcollectingsystem(gradeIV injuryinitiallyratedgradeIII)managednon-operatively.

Discussion

CTscanisthegold standardforinitialradiographicevalu- ationofrenaltrauma[2,3].TheAASTOISisthemostused classiﬁcationtoassess kidneyinjury [5] andhasa central placeinmodernmanagementalgorithms.Despitethevery clearitemsoftheAASTOIS,thegradingofrenalinjuriesis subjective andvaries amongradiologistsand urologistsas

shownbythevariationofCohen’sKappaagreementcoefﬁ- cientbetweentheraters.

Someauthorsdistinguish2severitygroups:low-andhigh- gradeinjury.Thisdifferenceisassociatedwithanincreased morbidity,mortalityand needfor surgeryor nephrectomy in high-grade injuries group. The classiﬁcation of grade III injuries is stilldiscussed. Some authors considergrade IIIinjuries inthis group[15—18].However,ourhigh-grade group included only grade IV and V injuries according to recentliterature[9—13].

AccuracyofAASTscalingisfundamentalsinceithasan importantprognosticvalue [6—8].AAST scalinginﬂuences renal injury management since only high-grade trauma should have a radiologic monitoring [2,3]. In our cohort, 2 cases of AAST rating discrepancies with severity group change presenteda complicationpotentially missed without a control CT scan. The main risk of an injury-rating mistakeisa downstaging.Indeed,it canincrease morbid- itybymissedcomplications[19,20]asillustrateinourcase of undiagnosed urinoma. An accurate scaling could help toreduce non-necessary radiologic monitoring during the patientstayandavoidpotentialCTscancomplicationssuch ascontrastnephropathy,increasedradiationanditsriskof radio-inducedcancers[21,22].

TheheterogeneityofCTscanacquisition(timeorproto- col)couldmaketheAASTscalingdifﬁcultsincesomeCTscan wererealizedinlocalhospitalsaroundourinstitution.For example,delayedimagingwasinconstantinourstudy(50%

ofCTscans)orintheliterature,althoughitallowsamore accurateanatomicgradingofrenalinjuriesandapotential targetedradiologicmonitoring[23].Infact,withoutdelayed imaging,agradeIIIinjurycanbelikentoagradeIVinjury asobservedinourcohort.

Thestrength ofourstudywasﬁrstlyitstripleindepen- dentAASTratingwithtwoseniorratersblindtotheclinical

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dataandsecondlytheanalyzeofrenalinjuryscalesubjec- tivity.Toourknowledge,onlyonestudytodateperformed a double grading of the renal injuries [13] but none has quantitativelyassessedtheAASTOISsubjectivity.

Theagreementbetweenthe3rater’sclassificationswas assessedbytheCohen’sKappacoefficient.Itshouldberead withcaution:usuallyasubjectivevariableisassociatedto alowerKappacoefficient than withan objectivevariable [14].Itcouldexplaintheoutcomesofourstudyquitedisap- pointingwithanagreementconsideredasfairtomoderate.

ThephysicianexperienceprobablyinfluencestheAASTrat- ingquality,sincetheresidenturologistobtainedthelowest Kappacoefficient. Sincethe urologist wasskilled inrenal pathology,thedifferencebetweentheseniorradiologistand thesenior urologist couldbe explained bysubjectivity of CTscanreadingandAASTscaleinterpretation.Despitethe very clear items of the AAST OIS, its use could be diffi- cultespeciallyforhigh-gradeinjuries.Indeed,thisgroupis heterogeneous:itincludes bothvascular andparenchymal injuries.Thetermofshatteredkidneyisalsosubjectiveand couldcorrespondtomultiplegradeIIIorIVinjuries[6,9]as showninFig.1.Thestudyresultshadtobeconsideredwith cautionsincethesmallnumberofreviewersfor theimag- ing.Itisdifficulttodifferentiateintra-andinter-specialty discrepanciesandtoconcludeadefinitesubjectivityofthe AAST OIS. An additional study with more CT scan raters wouldbehelpful.

BuckleyandMcAninchproposedarevisionofAASTinjury scalinginordertostandardizetherenalinjurymanagement [9].GradesItoIIIremainthesameasintheoriginalclas- sification. The new grade IV includes segmental vascular injuries and all renal collecting system injuries. The new gradeVincludesonlymainrenalpedicleinjury.Thisrevised classificationisbasedonthelifethreateningofmainvascu- larinjurieswithahigherexplorationrateandalowerrenal salvagerate but thisclassificationhas notbeen validated yet.

In thesameway, Altmann etal.suggested tocreatea gradeVIformainpedicleinjuriesorrenalinjuriesinhemo- dynamically unstable patients since their management is speciﬁc[24].

Someauthorssuggestedasubstratiﬁcationofintermedi- ateinjuries(gradeIIIandIV)accordingtotheinitialCTscan outcomes:perirenalhematomasize,intravascularcontrast extravasationand renal laceration location [12,16]. They calculatedaRenalTraumaRiskScore(RTRS)todistinguish grade IVainjury likely tobe managed conservativelyand gradeIVbinjurylikelytoneedanintervention(angiographic embolizationorsurgery)[12].

Ourstudy has a selection biasdue to itsretrospective natureanditsdependenceonadministrativedataquality.

Thetriplescalingwasrealizedretrospectivelyforstudypur- posessinceAASTscaling wasusuallynotmentioned inCT scanreportatthetimeofadmissionthoughitshouldbethe standard.

Oursinglecenter study alsogenerate alocal selection bias.High-gradeinjuries couldbeover-representedinour cohort,sinceourhospitalistheregionalreferencecenterfor severe polytrauma patients and emergencyinterventional radiology. However, our AAST grading is similar to other

Frenchstudies[18,25].ThecomparisontoNorthAmerican studiesisdifﬁcultsincetheyincludemuchmorepenetrating injurieswhicharequiteuncommoninEurope[7,8,13].

Intheinternationalguidelines,onlyhigh-grade injuries should have a control CT scan 48—96h after the trauma [2,3]. The impact of renal injury grading disagreement on radiologic monitoring was difﬁcult to assess in our study, as we could not evaluate the frequency of missed complications since our institution protocol used to rec- ommend so far a control CT scanﬁve days after trauma irrespectiveofrenalinjurygrade.However,wenotedthat AAST rating disagreements brought to a severity group changein 34%(n=17)andthereforetoapotentialchange ofradiologicmonitoring.Westronglysuggestaclosecollab- orationbetweenradiologistandurologistforAASTgrading inordertominimizethegradingmistakesandtorealizean appropriatemanagementandfollow-upofrenalinjuriesand adecreaseinunnecessaryradiologicalexams.

Conclusion

OurstudydemonstratesthatAASTgradingofrenalinjuriesis subjectiveandsuffersfrominter-raterreliability.Ourstudy stronglysuggeststheneedofanaccurateandcollegialgrad- ingbetweenradiologistsandurologists.Theoptimalstaging ofrenaltraumamayleadtoreducethemorbidityofunseen complicationsandtheiatrogenicriskofuselessimagingdue toastagingmistake.

Appendix 1. AAST OIS classiﬁcation [5]

Grade Description

I -Contusion:Microscopicorgrosshematuria, normalurologicalstudies

-Subcapsularhematoma,nonexpanding withoutparenchymal

laceration

II -Nonexpandingperirenalhematoma conﬁnedtorenalRetroperitoneum

-Laceration<1.0cmparenchymaldepthof renalcortexwithout

urinaryextravasation

III Laceration>1.0cmparenchymaldepthof renalcortex,without

Collectingsystemruptureorurinary extravasation

IV -Parenchymallacerationextendingthrough therenalcortex,medulla,andcollecting system

-VascularMainrenalarteryorveininjury withcontainedhemorrhage

V -Completelyshatteredkidney

-VascularAvulsionofrenalhilumwhich devascularizeskidney

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Appendix 2. Interpretation of Cohen’s Kappa coefﬁcient value

Kappavalue Agreement

0 Noagreement

0.01—0.2 Nonetoslight

0.21—0.40 Fair

0.41—0.60 Moderate

0.61—0.80 Substantial

0.81—0.99 Almostperfect

1 Perfect

Disclosure of interest

Theauthorsdeclarethattheyhavenocompetinginterest.

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