PORTOSYSTEMICMichaelCongenitalportosystemicshunts(pss)aremuchmorecommonandcertainlymuchmoreconfusingthanweeverimagined.AtTexasA&M,weinfrequentlyseethe“classic”congenitalPSSwiththerelativelystraightforwardpresentation(i.e.,youngYorkiewithpostprandialhepaticencephalopathy),probablybecausethosecasesareefficientlyfilteredoutandneverreferredtous.Somebreedsaremorecommonlyaffected(i.e.,Yorkshireterriers,Pugs,Maltese,Schnauzers,Poodles,ShihTzus,Havanese,IrishWolfhound,GoldenRetrievers,andLabradorRetrievers),butanydogmayhaveacongenitalPSS.Weinfrequentlyseeclassicpost-prandialhepaticencephalopathy;rather,wemorecommonlyseeayoungdog(e.g.,oneoftheabovebreedsthatislessthanayearold)thatisa"poordoer"whoisnotasbigorasstrongasthelittermateswithveryintermittentvomiting(i.e.,“heorshehasalwayshadasensitivestomach”)andsubtlesignsofencephalopathy.Therefore,itisimportanttoeliminateintestinalparasitesandhypoglycemiainanimalswithedcongenitalPSSsethesignsmaybeverysimilar.Polyuria-polydipsiacanbeamajorclinicalsign.Infact,inourpractice,mostyounganimalsreferredforpossiblecentraldiabetesinsipidusturnouttohavehepaticdisease,especiallycongenitalPSS.??|???§??--???‘#?K€????????$?,????7??”J???????B???ń?&??'???&?tdb??3 ??H#???QKT?ǜń?W???????ū??????????&ǜ???#,??d??B???ń”J??VK??=???W?2??Q???f?????o???8Ré????k???????F?N?2??°??ń?”J??í?7m????ń????é??F?(?6?????ǐ?0?????&;e??ǐ??Dz?#??z??è?????ǐb???<Oá?zǜ???ń?Y???Classichepaticencephalopathyconsistsofpost-prandialseizures,coma,somnolence,blindness,headpressingand/oraggression.However,weareseeingmoreandmoreanimalsinwhichhepaticencephalopathyismanifestedsimplybytheirlayingaroundalot,actingtiredorlethargic,orjustnotbeinginterestedinanything.Inmanycases,thereisnoobviousrelationshipbetweeneatingthesigns.Insomecases,aboutallyoucansayisthathepatienthasalwaysbeena“calm”dogandneverreallycausedalotoftroublebygettingintothings.Inolderdogs,theonlycommentbytheownermaybethattheydogis“gettingolderandslowingdownabit”.Tomakemattersmoreconfusing,wearefindingdogsthathavehepaticencephalopathythatdonotrespondtomedicalmanagementwithlactuloseormetronidazole.Someofthesepatientsonlyquithavingsignsofhepaticencephalopathywhentheshuntissurgicallycorrected.Therefore,youcannotallowlackofresponsetomedicaltherapyhelpyoudecidewhetherornotadoghashepaticencephalopathyduetoacongenitalPSS.Catswithhepaticencephalopathyduetocongenitalportosystemicshuntingoftenhavedroolingasamajorpresentingcomint.d????ń”Ja??B?????????Dg?>~∥?6???f??-- ń?￡ù6?ǐ?UkEg?ňe? ?ń??&? ??”J? ?'??V?-5J?A¤??7m<?? ??e?í ”J ???'?K???#5J>?[??ǔ??￡f?á?ǚ7???ńǜ?Eē??0?=·'I???0????` ”J3???ńǐ???í?????Oá?ǜ?? ?????ń?ā??|???§?????ń?·?e”J?Wesometimesseehematuriaduetoammoniumurateurolithiasis,butthisusuallyoftenhappensinolderdogs(especiallySchnauzers)thathavehadchronichyperammonemia.Manytimes,thisistheonlyclinicalsignintheaffectedpatient.Contrarytowhatisoftendescribedintextbooks,youcansometimesseemajorreasesinALTandSAP.WeoccasionallyseepatientswithmajorreasesinALT(i.e.,>1,000U/L)thatappeartohaveacquiredhepaticdisease,probablytoxicinnature.TheALTwaxesandwaneswithclinicalsigns.Ourguessisthatthesedogsonlyhavesignswhentheydevelopliverdiseasesecondarytoexposureto“toxins”thattheatrophiedlivercannotprocessbecauseitisinsufficient.ām??????;?"&?????·?5(mǜ??Z??<???????,"??&ǜńOá???ǐ???????‘?"6?.òZ?#"?ńǜ?.òZ? ????ǜ…??ń?&ā/? jèó??ǐ?5(???#?????ām?÷cE′ü?&??'??ǜ??5(?5m????ń"`”Jǐ??Tofurthercomplicatethesituation,weareseeingmoreandmoredogswithcongenitalthatarebeingdiagnosedforthefirsttimewhentheyare7oreven>10yearsold.ThisappearstobeespeciallycommoninSchnauzers,althoughotherbreedsmayalsobeaffected.Manytimesthesepatientshaverelativelyminorsignsthathavebeenconsideredasnormalfortheparticularpatient(i.e.,hasalwaysbeenaquietdog,hasalwaysbeenasmallishdog,etc).K????)?--??ǜ?üǘtü2"`?Sb??3?Q????????m??????M?A?Q5(?,"???ńǜ?7?@ǐ??q??????”J??=?????=???+Ascitesisexceedinglyrareinanimalswithcongenitalportosystemicshunts.ThisisindisttiontodogwithcongenitalhepaticAVfistula,whichisanothercongenitalvascularabnormalitybutwhichisentirelydifferentfromthestandpointofsigns,diagnosis,andtreatment.Ascitesisrelativelycommonindogswithacquiredportosystemicshunting.Therefore,ifascitesisseen,oneshouldfirstlookforotherhepaticdiseases.Inlikemanner,icterusisveryseldomcausedbycongenitalportosystemicshunts,andfindinghyperbilirubinemiaisanindicationtofirstlookforotherdiseases.Insummary,congenitalPSSpresentinavarietyofways,manyofwhicharenotthe“classic”presentationthatisdescribedintextbooks.?j??|???§Oáy?????????O??? ō??????ǐ????6?ǚ? co??j…?|???§????í?5J?j???é??A???ń?oR4?? ?|???§,??/???5JZ?? ê????ì?Ań???U?? Q”J???? ?'”J?Themajorcriteriaforpresumptivediagnosisofcongenitalportosystemicshuntsclassicallyconsistedofanappropriatehistoryandphysicalexaminationaswellasobviousmicrohepatiaandveryreasedserumbileacidconcentrations.ItwasgenerallyanticipatedthatdogswithcongenitalPSSwouldhaveserumbileacidconcentrations>90mmol/L.Hypoalbuminemia,hypocholesterolemia,and/ordecreasedBUNarecommonfindingsonclinicalpathology,buttheyarenotinvariable;somepatientswithcongenitalPSSdonothaveanyabnormalitiesontheserumbiochemistrypanel.Ammoniumbiuratecrystalsintheurineareusefuliftheyarepresent;but,mostofthecasesofdogswithcongenitalportosystemicshuntsthatweseedonothaveammoniumbiuratecrystalsintheurine. ?|???§e ##$"??????ǐ???? ??ń?Lǒ??[?? ?? (?ǒ??[?E??????ō????????m???? ?0??|???§ǜ?????5J??????Itnowappearsthatserumbileacidconcentrationsarenotaseasytointerpretorasasmanypeoplethink.First,youmustalwaysmeasurebothrestingandpost-prandialconcentrationsbecauseabout20%ofdogshavearestingserumbileacidconcentrationthatishigherthanthepost-prandialserumbileacidconcentrations.Second,therecanbemarkedvariationinserumbileacidconcentrationsfromdaytoday.Itiseasytoseeatwo-folddifferenceinvaluestakenafewdaysapart,andwehaveseenathree-fold reaseinsamplesthatweretaken72hoursapart.Third,somedogswithcongenitalportosystemicshuntshavesurprisinglylowserumbileacidconcentrations.WehavefounddogswithcongenitalPSSthathavewhatwewouldconsiderrelativelymodestreasesinserumbileacids(e.g.,55-65mmol/L,whichisavaluefoundinmanyanimalswithclinicallyinsignificanthepaticdisease),andrarecaseshavecompleynormalserumbileacidconcentrations.Indist tion,somedogswithoutanydemonstrablehepaticpathologyotherthanvacuolarhepatopathyhavevaluesinexcessof200mmol/L.Thismajoroverlapinthevaluesofserumbileacidconcentrationsindogswithandwithoutclinicallysignificanthepaticdiseaseleadsdiagnosticconfusioninsome ěy?i????? ??s???jèZm?B???jè??S?\Uk??? 5(?.???,T?? |Ukè???X??#)?' +"sB??pS????|???§ǜ????jè3i???#5J?? ǜ????jè?°òZ???#? ##$"????”Jg??ńOá???è????èń??μ???jè’c???o?? ?g??ń??”J6E??”J??????jèè??????0??ú?7m?0ń?Hyperammonemiaisveryspecificforhepaticinsufficiency,especiallycongenitalPSS.However,itiseasytohavelaboratoryartifactsthatfalselyreasethesevalues.Thistestcanonlyberuninhouse,andtheinstructionsmustbefollowedtothelettertoavoidartifactualresults.Measuringonlyfastingbloodammoniaconcentrationsisapproximay80%sensitiveforcongenitalPSS(andlowerfordiseasescausingacquiredhepaticinsufficiency).Theammoniatoleranceanexcellenttestwithveryhighsensitivityandspecificity,butitisaroyalpaintodo(e.g.,wouldyouliketodrinkammoniachlorideorhaveitinfusedintoyourrectum?)andconsequentlyisseldomperformed.Measuringbloodammoniaconcentrations4-8hourspost-prandiallyseemstoenhancethesensitivityforcongenitalPSSuptoabout90%.Z???÷ cY??”J?Y? ?? "?MV??z???q&??0 ??òZ? ??￡f????%g￡f2ǐ??;?[ǔ????y??? ?N?????/… ??÷ ?ń"??N?K??? ????? ūZ?N?ZY??ǒ????“2?q??W? ?N? Imagingcanbehelpful,butonemustrecognizethelimitationsofthesetechniques.WeexpecttoseemicrohepatiaindogswithPSS,althoughsometimesthechangeisverymodest.Sometimesthereisamarkeddifferenceintheapparentsizeoftheliverontheleftlalversustherightlalprojection.Radiographsareamuchmoresensitivewaytofindmicrohepatiathanultrasound.Ifthereisanydoubtaboutthesizeoftheliver,onecanadminisfewmlsofbariumsulfatetohelpoutlhestomach,allowingoeasilyascertainthecranialborderofthestomach.Theareabetweenthecranialborderofthestomachandthediaphragmisusuallytheliver.However,occasionalanimalswillappeartohaveasmallliverwheninfacttheyhaveanormalsizedliver.Fortunay,thissituationappearstobeunusualandshouldbepickedupiflalandDVviewsareú?L&??????ú?i????????#à?ǜ?&25J??'+???"???g??"??1???1?ǖ??+??,g???5J??'+??ǒ?‘a(chǎn)?ǒ?K?N??????+¤??&H?Oá|?ò????????K€μz????+???ó? ?Q??????????1v6??1?v?? Ultrasoundiscommonlyemployedwhenlookingforcongenitalportosystemicshunts.AultrasonographercanfindacongenitalPSSabout50-75%ofthetime,iftheyare plishedandcantaketheirtimeandlook.TrulyexceptionalultrasonographersseemtofindcongenitalPSSabout90%ofthetime.Therefore,youmustrememberthatfailingtofindacongenitalPSSonultrasounddoesnoiminateit.Furthermore,onecannotlookatthelivertoseeifthereareapparentlynormalportalareasasameansofdecidingifacongenitalshuntismoreorlesslikely.WehaveseenanimalswithcongenitalPSSthatappearedtohavenormalportalvasculatureonultrasound,tothepointthattheconclusionwasthongenitalshuntwasveryunlikely.Ultrasonographyisaverygoodwaytocheckforanintrahepaticshunt,whichismuchhardertocorrectthananextrahepatic????|???§"?￡fa?ǒ??1?d?a??×￠"k*???ì"?5J??|????ǖa??×ì??|?&?????í?ú?o3?a?ǒ??5J???é??ń?V????ǖ???|????????ō??|???§&??#?'??ǜ?a?ǒ??|??ú??????C#^5(|???§&?,??a?ǒ?Qy?_′?&>mǒ???Otherimagingtechniquesmay ludeoperativeorpercutaneousportograms,nuclearscintigraphy,andMRorhelicalCT.Theselattertechniquesshouldprimarilybedoneforoneoftworeasons.First,thecaseis“atypical”anditisimportanttoabsolu yconfirmthepresenceofacongenitalPSSbeforegoingtosurgery.Thesecondreasonisthatthesurgeonisunabletofindtheshuntduringanexploratorylaparotomy.Ingeneral,itisnotalwaysnecessarytodefinitively“see”theshuntviasomeimagingmodalitybeforegoingtosurgery.Ifthecaseisclassicinthatitisayounganimalwithappropriatesignsandanobviouslysmallliverandobviouslyhighserumbileacidsorammonia,thenoneisjustifiedingoingtosurgeryeveniftheshunthasnotbeenvisualized.Iftheshuntcannotbefoundduringsurgery,thenanintraoperativeportogramcanbeperformed.However,ifanyofthosethreecriteriaarenotmet(i.e.,“classic”history,obviouslysmallliver,obviouslyreasedserumbileacidsorammonia),thenconfirmationbyportography,scintigraphy,CTorMRis ????? ??"?ǎ>?????h?ī&y??'ń???s???4?y?? ?h?2??( 0????? ·'??ú?Lǒμ???????.òZ??&?ǒ￡fI??????ì0?????E′ì0???&￡f?|???ú?MV????2??????d?ń????g?'+??μ???????.òZ?"??·'|???ú?ǎ?;??? Retrogradeportographyisoftenpreferredwhenanintrahepaticshuntisbelievedlikelybecauseweprefertofixthesewithcatheters(i.e.,puttinginastentandthencoils).Nuclearscintigraphyisalsoverynice,butrequiresspecialfacilities.Oneadvantageofportographyisthatonemaycethecatheterintheshuntandleaveitthereinordertohelpthesurgeonfindtheshuntiftheyarehavingaverydifficulttimefindingit.?f?|???ú·?>m???§ńǜ?? ?ǚ?ń??ǎ?;???,}??? ??0???&???0?????Lastly,itisimportanttodoafullworkup(i.e.,CBC,serumchemistrypanel,abdominalradiographs,abdominalultrasound,serumbileacidsorbloodammonia)onalldogswithedcongenitalPSS.Thesedoayhaveother,concurrentdiseases.Infact,dogswithpreviouslywellcompensatedcongenitalportosystemicshuntsmaynot esymptomaticuntilanotherdiseaseprocesscausesthepatienttostartshowingsignsduetotheshunt.Furthermore,areasonablenumberofaffecteddogshavecysticcalculithatcanberemovedduringthesurgerytocorrectthecongenitalshunt.1B?7x??ǜ??ń?￡fcnǒ????μ(?ǒ?????v???a?ǒ???μ??????jè?,????&o"ǜ?A?ń?Dz?Us&2????|???§ǜ?&”J??ǐ????A?ńń??Oá:?3J|???§ǐ??V????è?ǜńOá?????&￡f|???§???"/???Surgicalcorrectionisusuallypreferredforyoungeranimalsandforthosethathavesignsencephalopathythatarenotcontrolledwithmedicaltherapy.But,surgeryisnotwithoutrisks.TheAmeroidconstrictormakesthesurgerymucheasierandquickerthanbefore.However,about15-20%ofdogsthathavesurgerytocorrectaPSSwillhavesomepost-operativecomplications(usuallysomethingminorlikeascites).Thisisusuallynotamajorproblem,buttheownerneedstobewarnedaheadoftime.SomedogsdevelopenoughportalhypertensiontocauseacquiredPSS,andafew(i.e.,5-7%)havemajor,life-threateningproblems(e.g.,post-ligationseizures,portalhypertension)anddie.NoteverydogwithacongenitalPSSisbenefittedbyAmeroidconstrictors.I?????>m<?Oá?>m8?3J??ń?ǐ???á?ǚEēOá??-¨??#%$!??I??q‘UsK€?ò9??? ??I??? ??°?5ǐ?W?j?? ¤????êsēTe?ǜ?5(|??Z??–V?5…? ?ń?? ?5(??(??W??B???|??Z??2?w??#%$!???>mx?? Amajorconcerncentersarounddogs(especiallythose5yearsoldandolder)withPSSthatareclinicallynormalandthathaveminimalchangesonserumbiochemistrypanelandaliverthatisnottoosmallonradiographs.WearefindingthesedogsbecauseawarenessofcongenitalPSShassubstantiallygrown,andmoreandmorepeoplearelookingforthemanddiagnosingtheminanimalswithminimalorevennoclinicalsigns.Iftheliverisnottoosmallonradiographs,theserumalbuminis>2.0gm/dl,andthereareminimaltonoclinicalsigns,thenwemightdecidetowatchthemtoseeiftheywilleverneedsurgery.DogswithcongenitalPSScausinghepaticencephalopathymaybenefitfromcorrectivesurgery,butsomedonot.Thereisconcernthatdogs>5yearsofagearemorelikelytohaveseverecomplicationsfromcorrectivesurgery.Whilethismightbethecase,manydogshavebenefittedfromsurgerydespitebeing>5yearsofage.Thisentireareaiscurrentlyverycontroversial.WeseesomedogswithcongenitalPSSthatseeminglyliveanormallifeandneverneedcorrectivesurgery.Therefore,ifyouareconsideringsurgeryinanolderdog(e.g.,>6yearsold)withoutanymajorclinicalsigns,youshouldprobablyhavealongtalkwiththeownersabouthowthedogcouldbeworseafterthesurgerythanitwasbefore.5J???PSSǜ??Y? ????”J????μ(?ǒ??[|?E???X?v???ǔ+?#5JR?0ń??? #—m??PSS?T ò?-- é???ń?????”Jg??E??”JOá??3?X?v ǔ+??μ???jèZm2.0mg/dl?|?E??”J? I??ǚ?td5(???ń??PSSǜ?&?I??ǚ?? ?ń??yWí?#íi ǜ???I?B5(???5ǐ¨?KZ?? #? ?5ü2 ǜ?·'I?ē?ǚ?a??sy??????#????PSSǜ???&2??(P?’c?￡fI??ǚ??í?W[??ǒ?7=<?ǔ?Eg???ǐ?ǜ??W?6ü2?￡fI??ǚ?&??ìe￡fu"k?·?ēTeOá?B&3J¤??&‘Ifpost-ligationsseizuresoccur,youmustfirstbesurethatthedogisnothypoglycemic.Thecauseofthisproblemisuncertain,butsomesuggestitmightbeduetocerebraledema.Wehavenottreatedrebraledemainthesepatients;rather,wetypicallyanesthetizethemwithaconstantrateinfusionofpropofoluntiltheseizureshavestopped.Donotusediazepamorphenobarbital.Some mendtreatingdogswithpotassiumbromideorKeppraandcatswithphenobarbitalbeforesurgeryforcongenitalportosystemicshunts,inanefforttoavoidthisproblem.Thisapproachiscontentious,andtimewill lifitiscorrectornot.Ingeneral,catswithcongenitalportosystemicshuntsdoseemtohavemorepost-operativeproblemsthandogs.?5(??B???ú???á?Oá-üm????ě??/¤??? ā?j????#?-?ǚ'?ńǜ?j?¤??V·??Oá?t????? ??????ǐ?5(¤???>???????￥??? ??Q_′????"k?z?????