Andersons pediatric cardiology 690

screenedforintestinalmalrotation.Datasuggestthatthisislikelynotnecessary.
Asdiscussedearlier,thereisahighproportionofisomericpatientswhowill
haveintestinalmalrotation,buttheincidenceofvolvulusisquitelow.Yet-to-bepublisheddatademonstratethatthosewhoexperiencevolvulustendto
experiencesymptomsanddevelopvolvulusinthefirstmonthsoflife.Thus
observingpatientsclosely,andimagingonlywhensymptomsarise,hasbecome
anincreasinglymorepopularandsafeapproach.Thosewithoutsymptoms
shouldnotundergouppergastrointestinalseriesroutinely.Ifanasymptomatic
patientdoesundergosuchtestingforindicationssuchasgastrostomytube
placement,andintestinalmalrotationisnoted,aprophylacticLaddprocedure
mayreasonablybedeferred.Ifsymptomsoccur,aLaddprocedurecanbedone
atthattime.Thisisaparticularlyusefulapproachinthosewhorequirea
Blalock-Taussigshunt.ThosewhoalreadyhaveaBlalock-Taussigshuntatthe
timeofLaddprocedureorthosewhoundergoplacementofsuchashuntshortly
afterLaddprocedureareatincreasedriskforthrombosisoftheBlalock-Taussig
shunt.88,93–96Growthandfeedingonlyinthosewithisomerismhasnotbeenthe
solefocusofstudiestothispoint,butitisanecdotallyknownthatfeeding
difficultiesarenotedinafairnumberofpatientswithisomerism.Infact,25%of
infantswithisomerismwillrequireeitheranasogastricorgastrostomytube.Ina
majorityofthesepatients,thetubecanberemovedby1yearofage.

ImmuneSystem
Theimmunesystemisoftenaffectedinthosewithisomerism.Infact,splenic
morphologywasinitiallyusedtosegregateso-calledheterotaxyintosubsets.
Althoughwenowunderstandthatsplenicmorphologyisnotthebestmeansby
whichtodividepatientswithisomerism,itisstillimportanttounderstandthe
splenicmorphologyinthesettingofisomerism.Traditionalsegregationof
isomerismhasbeenintothesubsetsofaspleniaandpolysplenia,althougha
proportionofpatientswithisomerismwillhaveasolitaryspleen.Thusallthree
ofthesearrangementsarepossible.Absenceofthespleen,orasplenia,isoften
notedinthosewithrightisomerism,whilepresenceofmultiplespleens,or
polysplenia,isoftennotedinthosewithleftisomerism.Asolitaryspleenis

locatedinasmallproportionofeithersubsetofisomerism.1,3,48,97Inadditionto
abnormalsplenicmorphology,thosewithisomerismmayalsohaveabnormal
thymicmorphology.Abnormalthymicinvolutionisfoundinnearly20%of
patientswithisomerismatthetimeofnecroscopy.48


Splenicfunctionisobviouslyabsentinthosewithisomerismandasplenia,but
splenicfunctionmayalsobediminishedorabsenteitherinthosewithisomerism
andpolyspleniaorinthosewithasolitaryspleen.98Inthosewithpolysplenia,
12%willhaveabnormalsplenicfunction,whileinthosewithasolitaryspleen,
11%willhaveabnormalsplenicfunction.Duetothisandlikelyotherfactors,
25%ofthosewithisomerismwillhaveadocumentedepisodeofbacteremia.An
overwhelmingmajorityoftheseepisodesofbacteremiaarenosocomialand
occurbefore2yearsofage.Mortalityinisomericpatientswithbacteremia
rangesbetween10%and58%.Thosewhodoexperiencemortalitybelievedto
bearesultofbacteremiaaregenerally21monthsofage.97,99–103Bacteremiais
duetoencapsulatedorganismsinnearly70%ofthosewithisomerism.Apart
fromabnormalsplenicmorphology,alownumberofimmunoglobulinmemory
Bcellsalsoincreasestheriskofbacteremiainthosewithisomerism.97,104
Becauseoftheincreasedriskofbacteremiainpatientswithisomerismandthe
increasedriskofmortalityassociatedwiththisbacteremia,specialprecautions
shouldbetaken.Basedondatafrompatientswithsicklecellanemia,inwhom
splenicfunctionisabnormal,antibioticprophylaxismaybehelpful.Thelimited
datathusfaravailablealsosupporttheuseofantibioticprophylaxis.
Whileitseemsintuitivethatsplenicfunctionshouldbedeterminedearlyin
lifetohelpguidetheinitiationofantibioticprophylaxis,currentlyavailable
splenicfunctiontestingisnotaccurateinthefirstfewyearsoflife.Testingprior
to2yearsofageisnotreliablebycurrentmethodology.101Thusallpatientswith
isomerism,eventhosewithmultiplespleensorasolitaryspleen,shouldbe
placedonantibioticprophylaxiswithamoxicillin,givenas20mg/kgperday,

dividedtwicedailyoronetimedaily.Forthosenottoleratingenteral
medications,ampicillincanbeusedinstead,withthetransitionmadeto
amoxicillinonceenteralmedicationsaretolerated.105,106
Forthosewithmultiplespleensorasolitaryspleen,splenicfunctiontesting
shouldbedoneat2yearsofage.Pittedredbloodcelltestingisthepreferred
method,duetoincreasedsensitivityandspecificity,butHowell-Jollybody
testingcanbeutilizedaswell.107–110Ifsplenicfunctionisnormal,antibiotic
prophylaxismaybediscontinued.Ifsplenicfunctionisabnormal,however,
antibioticprophylaxisshouldbecontinueduntil5yearsofage.Antibiotic
prophylaxismaybediscontinuedinallisomerismpatientsat5yearsofage
basedondatafromisomerismpatientsandsicklecellpatients.97,111
Inadditiontoantibioticprophylaxis,vaccinationsarealsoimportantin


patientswithisomerism.Thestandardvaccinationscheduleforchildren,as
establishedbytheAmericanAcademyofPediatrics,shouldbeused.However,a
fewadditionalvaccinationsshouldalsobeadministered.Thosewithisomerism
shouldreceivea23-valentpolysaccharidepneumococcalvaccinationafter2
yearsofageinadditionto(notinplaceof)the13-valentpolysaccharide
pneumococcalvaccination.Meningococcalvaccinationshouldalsobeslightly
alteredinthosewithisomerism,withHib-MenCY-TTbeingadministeredat2
months,4months,5months,and12monthsofage.112
Febrileepisodesinthosewithisomerismshouldleadtoroutineevaluation.All
isomericpatientswithatemperatureof38.5°Corgreatershouldbeevaluated
eitherintheoutpatientsettingorintheemergencydepartment.Evaluation
shouldincludeacompletebloodcountwithmanualdifferentiation,C-reactive
protein,andbloodculture.Additionaloptionalevaluationmayincludechest
radiographsandurineculture.Thosewhoappearhealthycanbedischarged
homeafterbeingadministeredasingledoseofintramuscularceftriaxoneand
appropriatefollow-upwhilebloodculturesaremonitored.Thosewhoappearill

shouldreceiveintravenousantibioticsandbeadmitted.Anypatientwith
isomerismwithapositivebloodcultureshouldcompleteafullcourseof
antibiotics,whichcanbedoneeitherinpatientoroutpatient.Thoseadmittedto
thehospitalcanbedischargedwhentheyappearwell,withcompletionof
antibioticspossiblyasanoutpatient.Thosewhoareadmittedandplacedon
antibiotictherapybecausetheyappearedillbutwhohavenegativeblood
culturescanhaveantibioticsstoppedafter48hours.111,113

GenitourinarySystem
Anatomicanomaliesofthegenitourinarysystemhavebeennotedinisomerism.
Theseincludehorseshoekidney,ectopicureters,ureteralduplication,cystic
kidney,solitarykidney,andcloacalduplications.Whathaveyettobedelineated
areanyfunctionalimplicationsofisomerismonkidneyfunction.