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Superiormesentericarterysyndromesuperiormesentericarterysyndromeisaveryrare,life-threateninggastrovasculardisordercharacterizedbyacompressionofthethirdportionoftheduodenumbythesuperiormesentericartery.SMAsyndromewasfirstdescribedin1861byCarlFreiherrvonRokitanskyinvictimsatautopsy,butremainedpathologicallyundefineduntil1927whenWilkiepublishedthefirstcomprehensiveseriesof75patients.Withonlyabout500reportedcasesinthehistoryofEnglish-languagemedicalliterature,SMAsyndromeisestimatedtohaveamortalityrateof1in3.SMAsyndromeisalsoknownasWilkie'ssyndrome,castsyndrome,mesentericrootsyndrome,chronicduodenalileusItisdistinctfromNutcrackersyndrome,whichistheentrapmentoftheleftrenalveinbetweentheAAandtheSMA.causesThesyndromeistypicallycausedbyanangleof6-25°betweentheAAandtheSMA,incomparisontothenormalrangeof38-56°duetoalackofretroperitonealandvisceralfat.Inaddition,theaorto-mesentericdistanceis2-8millimeters,asopposedtothetypical10-20.Retroperitonealfatandlymphatictissuenormallyserveasacushionfortheduodenum,protectingitfromcompressionbytheSMA.SMAsyndromeisthustriggeredbyanyconditioninvolvinganinsubstantialcushionandnarrowmesentericangle.SMASyndromecanpresentintwoforms:chronic/congenitaloracute/induced.Riskanatomicfactorssuchas:verythinorlankybodybuild,anunusuallyhighinsertionoftheduodenumattheligamentofTreitz,aparticularlyloworiginoftheSMA.Predispositioneasilyaggravatedsuchaspoormotilityofthedigestivetractretroperitionaltumorscachexiaexaggeratedlumbarlordosisvisceroptosisabdominalwalllaxityperitonealadhesionsabdominaltraumarapidlinearadolescentgrowthspurt,weightlossstarvationcatabolicstates(cancerandburns).Symptomsearlysatietynauseabiliousvomitingextremestabbingpostprandialabdominalpain(duetoboththeduodenalcompressionandthecompensatoryreversedperistalsis)severemalnutritionwithspontaneouswasting.This,inturn,increasestheduodenalcompressionspurringaviciouscycle.Symptomsarepartiallyrelievedwhenintheleftlateral,proneorknee-to-chestposition.Symptomsareoftenaggravatedwhenleaningtotherightortakingasupineposition.DemographicsSMAsyndromeisextremelyrare,evidentinonly0.013-0.3%ofuppergastrointestinal-tractbariumstudies.Asthesyndromeinvolvesalackofessentialfat,fourofeveryfiveafflictedareunderweight,oftentothepointofsicklinessandemaciation.Femalesareimpactedtwiceasoftenasmales,with75%ofcasesoccurringbetweentheagesof10and30.MortalitySMAsyndromeisestimatedtohaveamortalityrateof1in3.DelayinthediagnosisofSMAsyndromecanresultin:fatalmalnutritiondehydrationoliguriaelectrolyteabnormalitieshypokalemiaacutegastricruptureintestinalperforation(fromprolongedmesentericischemia)gastrectasiaDiagnosispostprandialabdominalpainnauseabiliousvomitingwastingsymptomsrelievedviatheleftlateral,proneorknee-to-chestpositionuppergastrointestinalbariumabdominalandpelvicCTscanwithcontrastUppergastrointestinalseriesshowingextremeduodenaldilation(whitearrow)abruptlyprecedingconstrictionbytheSMAAbdominalandpelvicCTscanshowingduodenalcompression(blackarrow)bytheabdominalaortaandthesuperiormesentericartery.TreatmentConservativetreatmentshouldbeattemptedfirst,involvingthereversalorremovaloftheprecipitatingfactorwithpropernutritionandreplacementoffluidandelectrolytes.Pro-motilityagentssuchasmetoclopramidemayalsobebeneficial.Ifconservativetreatmentfails,orifthecaseissevereorchronic,surgicalinterventionisrequired.ThemostcommonoperationforSMAsyndrome,duodenojejunostomy,wasfirstproposedin1907byBloodgood.LesscommonsurgicaltreatmentsforSMAsyndromeincludeRoux-en-Yduodeno-jejunostomy,gastro-jejunostomyandlysisoftheligamentofTreitz.Theworld'sfirstrobotically-assistedintestinalbypassforSMAsyndromewasperformedonJuly30,2008attheLondonHealthSciencesCentreinOntario,Canada.