兽医临床病理(英)教学教程

VeterinaryClinicalPathology兽医临床病理学CollegeofVeterinaryMedicine,SouthChinaAgriculturalUniversity,Guangzhou,China,510642PrefaceVeterinaryClinicalPathology:VeterinaryLaboratoryMedicineInclude:1ClinicalHematology2Clinicalbiochemistry3Clinicalcytology4Clinicalmicrobiology5Clinicalparasitology6ClinicaltoxicologyPrefaceGeneralLaboratoryconceptsVeterinarianshavemanychoicesregardinglaboratorytesting.Importantfactorsinclude:--Needandusefulness--Practicality--Cost-effectiveness--Accuracy--TurnaroundtimeCompleteBloodCountandBoneMarrowExamination:generalcommentsandselectedtechniquesCompletebloodcountQuantitationtechniquesBloodsmearanalysisOtherdeterminationsBonemarrowexaminationBonemarrowbiopsyandaspirateCompletebloodcount(CBC)CBCisaprofileoftestsusedtodescribethequantityandqualityofthecellularelementsinbloodandafewsubstancesinplasma.CBCisacost-effectivescreenthedetectsmanyabnormalitiesanddiseaseconditions.BonemarrowexaminationisusedinselectedinstancestoanswerquestionsthemorereadilyavailableCBCcannot.QuantitationTechniquesSamplesubmissionMicrohemotcritHemoglobinconcentrationCellcountsAbsolutenucleatedRBCcountAutomatedhematologycellcountersBloodSmearAnalysisMakingthesmearStainsEvaluatingbloodsmears--plateletmorphology--leukocytemorphology--leukocyteestimation--leukocytedifferentialcount--erythrocytemorphologyBoneMarrowExaminationBonemarrowisusuallyexaminedtoanswercertainquestionthatarosefromevaluatingtheCBC.Indicationsforbonemarrowexaminationinclude:--nonregenerativeanemia--Persistentneutropenia--Persistentthrombocytopenia--Unexplainedpolycythemiaorthrombocytosis--AtypicalcellsinbloodErythrocytesBasicconceptsoferythrocytefunction,metabolism,productionandbreakdownHemesynthesisGlobinsynthesisIronmetabolismErythrocytemetabolismEmbden-meyerhofpathway--GlycolysisgeneratesATPandNADHPentosephosphatepathway--ThispathwayproducesNADPHMethemoblobinreductasepathway--Methemoglobin(Fe3+)cannottransportoxygenRapoport-lueberingpathway--2,3diphosphoglycerate(2,3DPG)RedbloodcellsThefundamentalstimulusforproductionofredbloodcells(erythropoiesis)iserythropoietin(红细胞生成素）,aglycoproteinproducedbythekidneysinresponsetorenaltissuehypoxia.Otherhormones,suchascorticosteroids,thyroidhormoneandandrogens,stimulatetheproductionorreleaseoferythropoietinbuthavenointrinsicerythropoieticactivity.Theaveragelifespanofacirculatingerythrocyteis110-120daysinthedogand68daysinthecat.Agedordamagedredcellsareremovedprimarilybymacrophagesintheliver,spleenandbonemarrow.NeutrophilsTheproductionofneutrophils,eosinophilsandbasophilsistermedgranulopoiesis.Theneutrophilsinthebloodstreameithercirculatefreely(thecirculatingpool)oradheretothevascularendothelium(themarginalpool).Inthedogthemarginalpoolandthecirculatingpoolareapproximatelyequalinsize,whilstinthecatthemarginalpoolistwotothreetimeslargerthanthecirculatingpool.Thereisacontinualexchangeofcellsbetweenthesetwopools.Thehalf-lifeofcirculatingneutrophilsisonly6-14hours,afterwhichtimetheyleavethecirculationandpassintothetissuepool.Thecirculatingtimeisshortenedduringacuteinfectionsasneutrophilspasstothesiteofinfectioninthetissues.Themainfunctionoftheneutrophilisthephagocytosisofpyogenicbacteria.LymphocytesLymphoidprimitivestemcellsdivideanddifferentiateintopre-Blymphocytesandpre-Tlymphocytesinthebonemarrow.Pre-TlymphocytesmatureandproliferateintoTcellsinthethymus.Pre-Bcellsproliferateinthebonemarrowandmigratetoperipherallymphoidorgans(spleenandlymphnodes)wherefurtherproliferationtakesplace.PlateletsPlateletsareproducedfromthecytoplasmofmegakaryocytesOnceinthecirculation,plateletssurvivefor8-12days.Upto20-30%ofcirculatingplateletscanbesequesteredinthespleen;thefiguremaybeahighas90%ifthereissplenomegaly.Oldordamagedplateletsareremovedfromthecirculationbythespleen,liverandbonemarrow.ROUTINEHAEMATOLOGY

Thecompletebloodcountisanintegralpartofthediagnosticinvestigationofanysystemicdiseaseprocess.Itconsistsoftwocomponents:Aquantitativeexaminationofthecells,including:packedcellvolume(PCV)totalredcellcount(RBC)

totalwhitecellcount(WBC)differentialwhitecellcountplateletcountmeancorpuscularvolume(MCV),meancorpuscularhaemoglobin(MCH),meancorpuscularhaemoglobinconcentration(MCHC),totalplasmaproteinconcentration.Aqualitativeexaminationofbloodsmearsforchangesincellularmorphology.

Table1ReferencevaluesforredcellindicesDogsCatsTotalredbloodcells(x1012/L)5.5~8.55.0~10.0Haemoglobin(g/dl)12.0~18.08.0~15.0PCV(L/L)0.37~0.550.26~0.45MCV(fl)60.0~77.039.0~55.0MCH(pg)19.5~24.512.5~17.5MCHC(g/dl)32.0~37.030.0~36.0ROUTINEHAEMATOLOGY

REDBLOODCELLINDICESMCV(fl飞升)=PCV(L/L)×1000/totalredcells(×1012/L)MCH(pg皮克)=totalhaemoglobin(g/dl)×10/totalredbloodcells(×1012/L)MCHC(g/dl)=totalhaemoglobin(g/dl)/PCV(L/L)RBCindicesarehelpfulintheclassificationofcertainanemias.ROUTINEHAEMATOLOGY

Differentialwhitecellcounts

Thedifferentialwhitecellcountisperformedbycounting200leucocytesinabloodsmear.

Thecellsarecountedalongthelongedgeofthesmear,usingthebattlementmeandermethod:fourhigh-powerfieldsarecountedinonedirection,thenfourmoreinadirectionatrightanglestothefirst,andsoon,followingtheshapeofabattlement.

Thepercentageofeachtypeofcellisdetermined.

Thispercentageisthenmultipliedbythetotalwhitecellcounttoobtainanabsolutecountforeachcelltype.ROUTINEHAEMATOLOGY

Plasmaproteinconcentration(Referencerange:60-80g/1forthedogandcat)

Totalplasmaprotein(TPP)andPCVshouldbeinterpretedtogether.

QualitativeexaminationofabloodsmearAbloodsmearshouldalwaysbeevaluatedwhenautomatedcellcountsaremadeorwhenin-practiceinstrumentationislimitedtoacentrifugeforPCV

Preparationofabloodsmear

Asmalldropofbloodisplacedononeendofaglassslide,usingacapillarytube.Aspreaderslide(madebybreakingoffthecomerofanotherslide,afterscoringitwithaglasscutterordiamondwriter)isplacedontotheslideholdingtheblooddrop,infrontofthedropandatanangleof20-40°.ROUTINEHAEMATOLOGY

ANAEMIA

Anaemiaischaracterizedbyanabsolutedecreaseinredcellcount,haemoglobinconcentrationandPCV.Acutehaemorrhage

Acutehaemorrhagemaybeduetotraumaorsurgery,bleedinggastrointestinalulcersortumours,ruptureofavasculartumour(e.g.splenichaemangiosarcoma),oracoagulopathy(e.g.warfarintoxicity).

Immediatelyfollowingacutehaemorrhagetheredcellparameters,includingPCV,arenormalbecausebothredcellsandplasmahavebeenlostinproportion.CompensatorymechanismssuchasspleniccontractionmayfurtheroffsetanyfallinPCV.ThePCVfallswhenbloodvolumeisreplacedbyinterstitialfluidandsodoesnotindicatethefullmagnitudeofbloodlossforatleast24hoursaftertheonsetofhaemorrhage.ROUTINEHAEMATOLOGY

ChronichaemorrhageChronicexternalbloodloss(e.g.chronicgastrointestinalhaemorrhage,renalorbladderneoplasia)initiallyresultsinaregenerativeanaemiabutgraduallytheanaemiabecomesnon-regenerativeastheironstoresbecomedepleted.Younganimalsbecomeiron-deficientmorebonemarrowisalreadyveryactiveproducingredcellsquicklythanadultsfollowingbloodloss,partlybecausetheyhavelowironstoresandpartlybecausetheirtomatchtheirgrowthrateandsohaslesscapacitytoincreaseitsrateofhaemopoiesis.

HaemolyticanaemiasMostcasesofhaemolyticanaemiaareimmune-mediated.Inthedogmostcasesofimmune-mediatedishaemolyticanaemia(IHA)areprimary(idiopathic)andaretermedautoimmunehaemolyticanaemia(AIHA).IHAmayoccurinassociationwith:drugs(e.g.potentiatedsulphonamides);lymphoreticulardiseases(e.g.lymphoidleukaemia);systemiclupuserythematosus;orinfections(e.g.Babesia,bacterialendocarditis).ROUTINEHAEMATOLOGY

DISORDERSOFWHITECELLNUMBERNeutrophiliaFigure3.20CausesofneutrophiliaPhysiologicalresponse(fear,excitement,exercise)Stress/corticosteroid-inducedAcuteinflammatoryresponse:bacterialinfection(localizedorgeneralized),immune-mediateddisease,necrosis,e.g.pancreatitis,neoplasia,especiallywithtumornecrosis.ChronicgranulocyticleukaemiaNeutrophildysfunctionParaneoplasticsyndromesNeutropeniaThethreemaincausesofneutropeniaare:

•Anoverwhelmingdemandforneutrophils

•Reducedproductionofneutrophilsinthebonemarrow•Defectiveneutrophilmaturationinthebonemarrow.

Anoverwhelmingdemandforneutrophilsmayoccurwithperacutebacterialinfections,especiallyGram-negativesepsisandendotoxaemia.

Otherpossiblecausesincludeperitonitis,pyometra（子宫蓄脓）,aspirationpneumoniaandcanineparvovirusinfection.DISORDERSOFWHITECELLNUMBEREosinophilia

Eosinophilsaredistributedinthebodyamongvariouspoolsinasimilarwaytoneutrophils,althoughthebonemarrowstoragepoolisminimal.Eosinophilscirculateinthebloodstreamforonlyafewhoursbeforeenteringthetissues,wheretheymayliveforseveraldays.Theirtwomainfunctionsaretokillparasitesandtoregulateallergicandinflammatoryreactions.Eosinopenia

Eosinopeniaincombinationwithlymphopeniaoccursfollowingstress,administrationofcorticosteroidsandinspontaneoushyperadrenocorticism(Cushing'ssyndrome).Basophilia

Basophilscontaininflammatorymediatorssuchashistamineandheparinandfunctioninasimilarmannertomastcellsinhypersensitivityreactions.DISORDERSOFWHITECELLNUMBERLymphocytosisCausesoflymphocytosis1.Physiologicallymphocytosis,withconcomitantneutrophilia,inresponsetoexcitement(especiallycats)2.Strongimmunestimulation(e.g.inchronicinfection,viraemiaorimmune-mediateddisease)3.Chroniclymphocyticleukaemia4.Hypoadrenocortiscism(lymphocytosismaybeassociatedwithaneosinophilia)5.Increasednumbersoflargereactivelymphocytesmayoccurtransientlyfollowingvaccination6.YounganimalshaveahigherlymphocytecountthanadultanimalsDISORDERSOFWHITECELLNUMBERLymphopeniaCausesoflymphopeniaarelisted.StressGlucocorticoidtherapyHyperadrenocorticismChylothorax(lossoflymphocytesintothepleuralspace)Lymphangiectasia(lossoflymphocytesintothegut)Acutephaseofmostviralinfections(e.g.caninedistemper,parvovirus,FeLV)Septicaemia/endotoxaemiaDISORDERSOFWHITECELLNUMBERDogsCatspercentageAbsolutevaluepercentageAbsolutevalue(10/TotalWBCN/a6~17N/a5.5~19.5Bandneutropils0~30~0.30~30~0.3Neutropils60~773~11.535~372.5~12.5Lymphocytes12~301~4.820~551.5~7Monocytes3~100.2~1.51~40~1.5Eosinopils2~100.1~1.32~120~1.5basopilsrarerarerareRareReferencerangesfortotalanddifferentialwhitebloodcellcountsTable2showsthealterationsinsomeofparametersinvariousdiseases.LaboratoryassessmentTeststoassessprimaryhaemostasisinclude:PlateletcountBleedingtimeClotretraction.Teststoassesssecondaryhaemostasisinclude:Wholebloodclottingtime(WBCT)Activatedclottingtime(ACT)Activatedpartialthromboplastintime(APPT)One-stageprothrombintime(OSPT)Thrombintime(TT)DISORDERSOFWHITECELLNUMBERDisseminatedintravascularcoagulation(DIC):Thismaybetriggeredbyawidevarietyofdiseases,including

endotoxaemia

neoplasia(especiallyhaemangiosarcoma血管肉瘤)

acuteinfections(e.g.infectiouscaninehepatitis)

haemolyticanaemia

pancreatitis

heatstroke.TheclinicopathologicalfeaturesofDICare:

•Thrombocytopenia

•IncreasedOSPT/APTT

•ElevatedFDPs

•Lowfibrinogen•Schistocytesinthebloodfilm.DISORDERSOFWHITECELLNUMBER兽医临床病理学CollegeofVeterinaryMedicine,SCAU,Guangzhou,China510642VeterinaryClinicalPathologyClinicalbiochemistryIntroductionSerumproteinsTotalproteinandalbuminGlobulinsIndicatorsofrenalfunctionUreanitrogenCreatinineMarkersofhepaticdiseaseAlanineaminotransferaseAspartateaminotransferaseAlkalinephosphataseGamma-glutamyitransferaseBilirubinBileacidsAmmoniaPancreaticdiseaseAmylaseLipaseElectrolytesSodium;Potassium;ChlorideMagnesium;Calcium;

PhosphorusMuscleenzymesCreatinekinaseAspartateaminotransferaseCarbohydratemetabolismGlucoseFructosamineLipidmetabolismCholesterolTriglyceridesMiscellaneoustestsIronLeadZincCopperChemicalprofilesandtestselection

SERUMPROTEINSTotalproteinandalbumin

PhysiologyThecirculatingproteinsaresynthesizedpredominantlyintheliver,althoughplasmacellsalsocontributetotheirproduction.Quantitativelythesinglemostimportantproteinisalbumin(35-50%ofthetotalserumproteinconcentration).Theotherproteinsarecollectivelyknownasglobulins.Thefunctionsofproteinsaremanyandvariedbutincludemaintenanceofplasmaosmoticpressure,transportofsubstancesaroundthebody(e.g.ferritin铁蛋白,ceruloplasmin血浆铜蓝蛋白),humoralimmunity,bufferingandenzymeregulation.IndicationsforassayThemeasurementofproteinsisgenerallyincludedinaninitialhealthscreeninallpatientsbutespeciallywhereintestinal,renalorhepaticdiseaseorhaemorrhageissuspected.AnalysisProteinconcentrationscanbeestimatedinserum,plasma,urineorbodyfluidswitharefractometerorbyspectrophotometry.Serumalbuminlevelsaremeasuredbybromocresolgreendye溴甲酚绿

bindingandtheserumglobuliniscalculatedbysubtractionofthealbuminconcentrationfromthetotalproteinconcentration.ReferencerangesNeonatesandveryyounganimalshavelowerconcentrationsofalbuminandglobulins(duetominimalquantitiesofimmunoglobulins).Astheanimalgainsimmunocompetencetheproteinconcentrationsrisetoreachadultvalues.Physiologicaldecreasesinalbuminmaybenotedduringpregnancy.CriticalvaluesMarkedhypoalbuminaemia(<15g/L)isassociatedwiththedevelopmentofascitesandtissueoedema.Accumulationofperitonealfluidmayoccurathigheralbuminconcentrationsifthereisconcurrentportalveinhypertension,e.g.inchronicliverdisease.InterferingphenomenaLipaemia,haemolysisandhyperbilirubinaemiaproducefalseincreasesintotalproteinconcentrations.DrugeffectsHormoneshaveamarginaleffectonplasmaproteinconcentrations.Corticosteroidsandanabolicsteroidsmayincreasetheproteinconcentrationduetotheiranaboliceffectswhilethecataboliceffectsofthyroxinecancauseadecrease.SERUMPROTEINSFigure4.3:Causesofhypoalbuminaemia.IncreasedlossGlomerularproteinlossProtein-losingenteropathyCutaneouslesions,e.g.bumsExternalhaemorrhageDecreasedproductionHepaticinsufficiencyMalnutritionMaldigestionMalabsorptionSequestrationBodycavityeffusionSERUMPROTEINSGlobulinsAnalysisSerumproteinelectrophoresis(SPE)oncelluloseacetategelsallowsfractionationoftheproteins,dependingpredominantlyontheirchargeandsize.Afterstainingforprotein,thecelluloseacetatestripisscannedbyadensitometerwhichconvertstherelativeintensitiesoftheproteinbandstopercentagesandgeneratesagraphthatdemonstratestheproteinfractions(albumin,α1-globulin,α2-globulin,β1-globulin,β2-globulin,γ-globulin).CausesofhypoglobulinaemiaThemostcommonpathologicalcausesarehaemorrhageandprotein-losingenteropathies.SERUMPROTEINSFigure4.4:Causesofhyperglobulinaemia.PolyclonalgammopathyInfections:BacterialdiseaseViraldisease(e.g.FIP)Immune-mediateddiseases:SystemiclupuserythematosusRneumatoidartnntisImmune-mediatedhaemolyticanaemiaImmune-mediatedthrombocytopemaNeoplasia,especiallylymphosarcomaMonoclonalgammopathyNeoplasia:MultiplemyelomaMacroglobulinaemiaLymphosarcomaFelineinfectiousperitonitis(rare)SERUMPROTEINSUreanitrogenPhysiology★Dietaryproteinsarehydrolysedintheintestinestotheirconstituentaminoacidswhichmay,inturn,bedegradedtoammoniabytheactionofgutbacteria.★Theammoniaandaminoacidsaretransportedtotheliverviatheportalcirculationwheretheyareutilizedintheureacycle.★Theureaformedinthehepatocytesisexcretedviathekidneytubules.★Ureaplaysanimportantroleinconcentratingtheurine;thepresenceofhighconcentrationsofureaandsodiumchlorideintherenalmedullaryinterstitiumcreatesanosmoticgradientforreabsorptionofwater.INDICATORSOFRENALFUNCTIONIndicationsforassayTheureanitrogen(urea)concentrationisoneofthetestsusedwhenscreeningrenalfunction.Itisoftenmeasuredwhentheclinicalsignsincludevomiting,anorexia,weightloss,polydipsiaanddehydration.AnalysisUreacanbemeasuredinserum,plasmaandurinebyspectrophotometry.Sticktestsforwholebloodarealsoavailable.ReferencerangesDogs3.0-9.0mmol/LCats5.0-10.0mmol/LInterferingphenomenalipaemiainterfereswiththeanalysisandproducesvariableeffectsdependingonthemethodology.INDICATORSOFRENALFUNCTIONCausesofreducedbloodurea

☆Reduceddietaryproteinintakeisassociatedwithalowbloodurea.

☆Inaddition,patientswithdiffuseliverdiseasehaveanimpairedcapacitytosynthesizeureaandreducedhepaticproduction.Wherehepaticdiseaseissuspected,acompletebiochemistryprofileandabileacidstimulationtestareindicated.

☆Themarkeddiuresis（多尿）

associatedwithsomeconditions,especiallyhyperadrenocorticismanddiabetes,resultsinincreasedurinarylossofureawhich,inturn,causesareductionofthebloodurea.INDICATORSOFRENALFUNCTIONCausesofincreasedbloodurea☆Increaseddietaryproteinintakeproducesahighlevelofureaintheblood.Amoderateincreaseindietaryproteinisnotcommonlyassociatedwithanotableriseinureaabovethereferencerange,buthigh-proteindietscancausesignificantincreases.☆A12-hourfastisrecommendedbeforesamplingformeasurementofurea.☆Intestinalhaemorrhagealsoresultsinanincreasedconcentrationwhichisreportedtocorrelatewiththeseverityofbloodloss.☆Ureaisfreelyfilteredattheglomerulusandreabsorbedintherenaltubules.Therateofreabsorptionishigheratslowerurinaryflowrates,e.g.indehydratedpatients.☆Bloodureaisthereforenotareliableestimateoftheglomerularfiltrationrate(GFR).Increasedureaconcentrationsareassociatedwithconditionsotherthanparenchymalrenaldisease.☆Thepresenceofaconcentratedurinesample(urineSG>1.030indogs,>1.035incats)supportsthediagnosisofaprerenalazotaemia.INDICATORSOFRENALFUNCTIONCreatininePhysiology◤Creatinineisformedfromcreatineinthemusclesinanirreversiblereaction.Thequantityofcreatinineproduceddependsupondiet(smallcontribution)andthemusclemass.Diseaseaffectingthemusclemassmayaffectthedailycreatinineproduction.◤BothureaandcreatininearefreelyfilteredattherenalglomerulusbutureaissubjecttotubularreabsorptionandthuscreatinineissaidtobeabetterindicatorofGFR.Analysis◤Creatininecanbemeasuredinserum,plasmaorabdominalfluidbyspectrophotometricmethods.Referenceranges

Dogs20-110umol/LCats40-150umol/LINDICATORSOFRENALFUNCTIONCausesoflowserumcreatinine◤

Sincethedailyproductionofcreatinineisdependentuponthemusclemassoftheanimal,thebodyconditionshouldbeconsideredwheninterpretingserumcreatinineconcentrations.Apoorbodyconditionmaybeassociatedwithlowconcentrationswhileminorrisesinsuchcasesmaybemoresignificantthaninotherindividuals.Causesofincreasedserumcreatinine

◤

Decreasedglomerularfiltrationisthemajorcauseofraisedserumcreatinine.However,approximately75%ofnephronfunctionmustbeimpairedbeforeserumcreatinine(andurea)isincreased.CreatinineisconsideredamorereliableindicatorofGFRthanisureanitrogen,sincetherearefewerfactorswhichinfluencetheserumconcentrationofcreatinine.INDICATORSOFRENALFUNCTION►Thebiochemicalparametersusedtoassessliverpathologymaybedividedintotwoclasses:thehepaticenzymesthatreflectliverdamageandcholestasis,andtheendogenousindicatorsofliverfunction.►Alanineaminotransferase(ALT)isthemostusefulenzymeforidentifyinghepatocellulardamageindogsandcatsbutshouldnotbeusedaloneasascreeningtestforliverdisease.►Theproductionofotherenzymes,i.e.alkalinephosphatase(ALP)andgamma-glutamyltransferase(GGT),isincreasedsecondarytointra-andextrahepaticcholestasis.►Theseenzymesaremarkersofcholestaticdisease.►Bilirubin,serumalbuminandserumbileacidsareconsideredtobeindicatorsofhepaticfunction.►Itiscommonforextrahepaticdisease(e.g.pancreatitis,diabetesmellitus,hyperadrenocorticismandinflammatoryboweldisease)tocauseabnormalitiesofthesebiochemicalparameters.MARKERSOFHEPATICDISEASEAlanineaminotransferase(ALT)Physiology

ALTisfoundinthecytosolofhepatocytesandinmuscletissueinthedogandcat.Activitiesintheserumareelevatedbyleakageoftheenzymesecondarytoanincreaseinhepatocytemembranepermeabilityorcellnecrosis.Theformermaysimplybeaconsequenceofhypoxiaandneednotreflectcelldeath.IncreasedserumALTmaybenotedwithin12hoursofanacutehepaticinsultbutcantake3-4daystoreachpeaklevelsafterexperimentalcholestasis（胆汁阻塞）.Thedegreeofincreaseinenzymeactivitycorrelatesapproximatelywiththenumberofhepatocytesaffectedbutdoesnotindicatethenature,severityorreversibilityofthepathologicalprocess.ALTactivityisnotanindicatorofhepaticfunction.IndicationsforassaySerumALTisausefulaidinthediagnosisofhepaticdiseaseandismeasuredwheretheclinicalsignsmightsuggestahepatopathy,e.g.weightloss,anorexia,polydipsia,vomiting,diarrhoea,ascitesandjaundice.AnalysisTheactivityoftheenzyme(ininternationalunits)ismeasuredinserumorplasmabyspectrophotometricmethodsunderspecifiedconditions.ReferencerangesDogs<100units/LCats<75units/LMARKERSOFHEPATICDISEASECausesofraisedALTactivity

GuidelinesfortheinterpretationofraisedliverenzymeactivitiesinrelationtoliverdiseasesaregiveninChapterliver.ThemajorityofdiseasesthataffectthelivercouldpotentiallycauseanincreaseinserumALTactivitybutthosepathologicalprocessesthatmightcauseamarkedincreaseincludeparenchymaldisease/damage,cholangitis,cholangiohepatitis,chronichepatitis,anoxia,cirrhosisanddiffuseneoplasia,e.g.lymphoma(lymphosarcoma).However,insomecasesthesediseasesmaybeaccompaniedbyanegligibleincreaseornoincreaseinserumALTactivity.CausesofreducedALTactivity

Anartefactualreductioninserumenzymeactivitiesmayresultfromsubstratedepletion.Dilutionandrepeatassayofthesamplearenecessarytoexcludethisphenomenon.ReducedALTactivities(belowthereferencerange)aregenerallynotconsideredtobeofclinicalsignificance,butthepossibilityofchronicliverdiseaseandnutritionaldeficiencies(zincorvitaminB6)shouldbeconsidered.MARKERSOFHEPATICDISEASEAspartateaminotransferase(AST)(seealsoMuscleenzymes)PhysiologyASTislocatedinthemitochondriaofthecellandispresentinsignificantquantitiesinhepatocytes,erythrocytesandinmuscle.ASTisthereforenotliver-specificbut,likeALT,itsactivityintheserumiselevatedbyleakageoftheenzymefromthecell.IndicationsforassayASTisincludedindiagnosticprofilesforinvestigationofsuspectedliverdiseaseormuscledisease.AnalysisTheenzymeactivityismeasuredinserumandheparinizedplasmabyspectrophotometry.ReferencerangesDogs7-50units/LCats7-60units/LCausesofraisedASTThemostcommoncausesofincreasedASTarehepaticdisease,muscledisease(trauma,inflammation)andhaemolysis.Concurrentmeasurementofotherhepaticenzymes(ALT,ALP,GGT)andhepaticfunctionindicators(albumin,urea,bilirubin,bileacids)areessentialtoestablishtheoriginoftheincreasedserumASTandtoprovidefurtherinformationregardingliverdamageandfunction(seeChapter9).Withrespecttoliverdamage,theserumactivityofASTtendstoparallelthatofALT.MARKERSOFHEPATICDISEASEAlkalinephosphatase(ALP,SAP)PhysiologyIndogsandcatsthereareisoformsofALPlocatedinbrushbordersintheliver,placenta,intestine,kidneyandbone.Inthedogthereisalsoasteroid-inducedisoenzyme(SIALP),theoriginofwhichhasnotbeenfullydetermined.TheproductionofSIALPisincreasedbytheadministrationofglucocorticoids(oral,parenteralortopical),byexcessiveproductionofendogenousglucocorticoids(hyperadrenocorticism)andinassociationwithchronicdisease(e.g.renalorhepatic).Theliverisoenzymeisresponsiblefortheserumactivityinthenormaladultdogandcat.IndicationsforassaySerumALPisoneofthetestscommonlyincludedinscreeningprofilesforhepaticdisease(cholestasis)andhyperadrenocorticism.Itisthereforeusefulwheretheclinicalsignssuggesteitherofthesediagnoses,e.g.weightloss,anorexia,polydipsia,vomiting,diarrhoea,ascitesandjaundice.AnalysisSerumALPactivityismeasuredinserumorheparinizedplasmabyspectrophotometry.ReferencerangesDogs<200units/LCats<100units/LMARKERSOFHEPATICDISEASECausesofraisedALP