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IschemicColitisRi陳宏彰ReferencebooksHarrison’sonline15thMarx:Rosen'sEmergencyMedicine:ConceptsandClinicalPractice,5thed.,Copyright©2002Mosby,IncIschemicColitisIschemiaofthecolonmostoftenaffectstheelderly

(90%ofpatients>60y/o).Ischemiccolitisisalmostalways

nonocclusive.

(emboliarethemostcommoncauseofacutemesentericischemia)Shuntingofbloodawayfromthemucosa

maycontributetothiscondition,butthe

mechanismisunknown.IschemicColitisMostpatientsischemiaoccurssecondarytoarteriolarshunting,

spasm,orpoorperfusionofmucosalvessels.Mostcasesinvolvethesplenicflexure,whichissuppliedbyend-arteries.Therectumisusuallyspared,becauseitsbloodsupplyisdifferentfromtherestofthecolonandlessdependent

ontheinferiormesentericartery.Marx:Rosen'sEmergencyMedicine:ConceptsandClinicalPractice,5thed

TypesofIschemicColitisAcutefulminantischemiccolitis

Subacuteischemiccolitis

HARRISON’SONLINE15TH

TypesofIschemicColitisGangrenousischemiccolitis

acompletelossofarterialflowcausesbowelwallinfarctionandgangrene,whichcanprogresstoperforation,peritonitis,anddeath.Stricturingischemiccolitis

agrossimpairmentofthearterialsupply,leadingtohemorrhagicinfarctionofthemucosa,whichulcerates,healsbyfibrosis,andfinallyleadstostenosis.Transientischemiccolitis

atransient,reversibleimpairmentofthearterialsupply,whichcausesapartialmucosalsloughthathealsbymucosalregenerationinafewdays.themostcommon

Marx:Rosen'sEmergencyMedicine:ConceptsandClinicalPractice,5thed

Acutefulminantischemiccolitismanifestations

Theonsetischaracteristicallyacute,withgeneralizedlowerabdominalpain,usuallyintheleftlowerquadrant,followedwithin24hoursbybloodydiarrheaorrectalbleeding.Dilationofthecolonandphysicalsignsofperitonitisareseeninseverecases.Withthegangrenoustype,bothsymptomsandsignsprogressrapidly.

AcutefulminantischemiccolitisDiagnosticStrategyNospecificserummarkersproveninthediagnosisofintestinalischemia.

Abdominalfilmsmayreveal

thumbprintingfromsubmucosalhemorrhageandedema.*(bariumenemaiscontraindicatedincasesofgangrenousischemic

colitis

becauseoftheriskofperforation)thumbprinting

AcutefulminantischemiccolitisDiagnosticStrategySigmoidoscopyorcolonoscopymaydetectulcerations,friability,andbulgingfoldsfromsubmucosalhemorrhage.(Colonoscopyispreferredoversigmoidoscopy

)Thesegmentaldistributionandrectalsparingofthediseaseprocessaresuggestivebutarenotdiagnostic.Colonoscopicviewshowingmarkederythemaandexudateinsigmoidcolon

Endoscopicviewofmucosaledema,exudates,andulcerationsinsigmoidcolon

Endoscopicimageofdescendingcolonshowingseverecolitiswithpneumatosisintestinalis.

AcutefulminantischemiccolitisDiagnosticStrategyAngiographyisnothelpfulinthemanagementofpatientswithpresumedischemiccolitisbecausearemediableocclusivelesionisveryrarelyfound.

CTscanisnormalinearlystagesofbowelinfarction,althoughitmayshownonspecificfindingssuchasbowelwallthickeningandpneumatosis.

CTshowingleftsidedcolonicthickening.PneumatosisIntestinalisPneumatosisIntestinalisAcutefulminantischemiccolitismanagementWhenischemiccolitisissuspected,asurgeonshouldbeconsulted.Gangrenousischemiccolitisorevidenceofperforationrequiresimmediatesurgeryassoonasthepatientisstabilized.

managementVasopressorsshouldbeavoided,ifpossible.Lowblood-flowstates(hypotension)shouldbeaggressivelyreversed.TypesofIschemicColitisAcutefulminantischemiccolitis

Subacuteischemiccolitis

Subacuteischemiccolitis

manifestations

Itproduceslesserdegreesofpainandbleeding,oftenoccurringoverseveraldaysorweeks.

Theleftcolonmaybeinvolved,buttherectumisusuallysparedbecauseofthecollateralbloodsupply.Subacuteischemiccolitis

managementSubacute

Ischemic

colitiswithoutevidenceofperitonitisorperforationisgenerallyself-limitedandrequiresonlyconservativemanagement,includingbowelrest,parenteralfluids,andantibiotics.Subacuteischemiccolitis

management

Mostcasesofnonocclusiveischemiccolitisresolvein2to4weeksanddonotrecur.Surgeryisnotrequiredexceptforobstructionsecondarytopostischemicstricture.

DifferentialConsiderationsIschemic

colitisoftenmimicsinfectiouscolitis,inflammatoryboweldisease,orevencoloncarcinoma.ManycasesofcolitisintheelderlyonceconsideredtobeCrohn’sdiseaseorulcerativecolitisinretrospectwerereallycolonicischemia.

DifferentialConsiderationsThefeaturesconsideredatypicalininflammatoryboweldiseases,suchas1.segmentaldistributionofthedisease,infrequentrectalinvolvement,2.highrateofspontaneousrecovery,lowrateofrecurrence,3.lackofadequateresponsetousualinflammatoryboweldiseasetherapy,4.frequentprogressiontofibroticstenosiswithdelayedobstructionThefeaturesabovearenowrecognizedascharacteristicofcolonicischemia.

DifferentialConsiderationsAlwaysconsiderthediagnosisofischemic

colitiswhenevercontemplatingthediagnosisofinflammatoryboweldiseaseinanelderlypatient.

DifferentialDiagnosisClinical

Radiologic

UlcerativecolitisBloodydiarrheaExtendsproximallyfromrectum;finemucosalulcerationCrohn’scolitisPerianallesionscommon;frankbl