going for the gold: urinalysis and beyond · going for the gold: urinalysis and beyond joe bartges,...
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GOINGFORTHEGOLD:URINALYSISANDBEYONDJoeBartges,DVM,PhD,DACVIM,DACVNProfessorofMedicineandNutrition
• Partofaminimumdatabase• Evaluatewithurinarydisease:“Godmadeitgoldforareason”• Collectbyvoid,cystocentesis,catheterization
• Evaluatewithin30minutes• Ifnotpossible,refrigerate(2-8C)upto24hours• Re-warmtoroomtemperature
• Delaymayalterresults• Bacterialcontaminationordeath• Glucoseutilization• FalseincreaseinpHandprotein• Castsandcellsdeteriorate• Invivoprecipitationofcrystals
• Componentsofcompleteurinalysis• Urineappearance
• Color• Normalurineistransparentandyelloworamber• Intensityofcolorisrelatedtovolumeofurinecollectedandconcentrationofurine• Interpretincontextofurinespecificgravity(USG)• Diseasemayexistwithnormalcolor• Abnormalcolormaybecausedbypresenceofendogenousorexogenouspigments,butitdoesnot
providespecificinformation.Interpretationofsemi-quantitativereagentstrips,whicharecolorimetrictests,requiresknowledgeofurinecolorbecausediscoloredurinemayresultinafalsepositiveresult.Equineurinemayturnbrownafteraperiodoftime.
• Redurinedoesnotmeanblood(hematuria)• PositiveOCCULTBLOODonteststrip–canbeblood,hemoglobin,ormyoglobin• Pigment:e.g.myoglobin(clearserum)orhemoglobin(redserum)• Otherpigments:e.g.drugs
Table.PotentialcausesofdiscoloredurineURINECOLOR CAUSES URINECOLOR CAUSESYelloworamber Urochromes
UrobilinYellow-brownorgreen-brown
Bilepigments
Deepyellow HighlyconcentratedurineQuinacrine*Nitrofurantoin*Phenacetin*Riboflavin(largequantities)*Phenolsulfonphthalein(acidicurine)*
Browntoblack(brownorred-brownwhenviewedinbrightlightinthinlayer)
MelaninMethemoglobinMyoglobinBilepigmentsThymol*Phenoliccompounds*Nitrofurantoin*Nitrites*Naphthalene*Chlorinatedhydrocarbons*Anilinedyes*Homogentisicacid*
Blue MethyleneblueIndigocarmineandindigobluedye*Indicans*Pseudomonasinfection*Water-solublechlorophyll*Rhubarb*Toluidineblue*Triamterene*Amitriptyline*Anthraquinone*Bluefooddye*
Colorless Verydiluteurine(diuretics,diabetesmellitus,diabetesinsipidus,glucocorticoidexcess,fluidtherapy,overhydration)
Green MethyleneblueDithiazanineUratecrystalluriaIndigoblue*Evan’sblue*BilirubinBiliverdinRiboflavin*Thymol*Phenol*Triamterene*Amitriptyline*Anthraquinone*Greenfooddye*
Milkywhite LipidPyuriaCrystals
Red,pink,red-brown,red-orange,ororange
HematuriaHemoglobinuriaMyoglobinuriaPorphyrinuriaCongoredPhenolsulfonphthaleinNeoprontosilWarfarin(orange)*Foodpigments(rhubarb,beets,blackberries)*
Carbontetrachloride*
Brown MethemoglobinMelaninSulfasalazine*Nitrofurantoin*Phenacetin*Naphthalene*Sulfonamides*Bismuth*Mercury*Feces(rectal-urinaryfistula)Favabeans*
PhenazopyridinePhenothiazine*Diphenylhydantoin*BromsulphaleinChronicheavymetalpoisoning*Rifampin*Emodin*Phenindione*Eosin*Rifabutin*Acetazolamide*Redfooddye*
Rhubarb*Sorbitol*Metronidazole*Methocarbamol*Anthracincathartics*Clofazimine*Primaquine*Chloroquine*Furazolidone*Coppertoxicity
Orange-yellow HighlyconcentratedurineExcessurobilinBilirubinPhenazopyridineSulfasalazine*Fluoresceinsodium*Flutamide*Quinacrine*Phenacetin*2,4-d*Acetazolamide*Orangefooddye*
*Onlyobservedinhumanbeings• Turbidity
• Urineistypicallyclear• Maybelesstransparentwithpigmenturia,crystalluria,hematuria,pyuria,lipiduria,orother
compoundssuchasmucous.• Theincreasedturbiditymaydisappearwithcentrifugationofthesampledependingonthe
causeofincreasedturbidity.• Odor
• Normalurinehasaslightodorofammonia;however,theodorisdependentonurineconcentration.
• Somespecies,suchascats(felinine)andgoats,havepungenturineodorbecauseofurinecomposition.
• Bacterialinfectionmayresultinaverystrongodorduetopyuriaandastrongammoniaodorifthebacterialorganismproducesurease.
• Centrifugefor3-5minutesat1500-2000rpm
• Pouroffsupernatant• CandoUSG• Usefordipstick(semi-quantitativechemicaltesting)
• Leavesmallpelletwithlittleurineintubeformicroscopicexamination• Dipstick(semi-quantitative,colorimetricreagentstrips)
• ReagentstripssuchasMultistix®orChemstrip®canbeusedtoperformseveralsemi-quantitativechemicalevaluationssimultaneously.
• DetermineurinepH,proteinglucose,ketones,bilirubin/urobilinogen,andoccultblood.• Somereagentstripsincludetestpadsforleukocyteesterase(fordetectionofwhiteblood
cells,(WBC)),nitrite(fordetectionofbacteria),andUSG;thesearenotvalidinanimalsandshouldnotbeused.
• Reagentstripsareadverselyaffectedbymoistureandhavealimitedshelflife.Bottlesshouldbekepttightlycapped,andunusedstripsshouldbediscardedaftertheirexpirationdate.
• pH• Variesfrom5.0-9.0• Accuratetowithin0.5pHunits
• Areadingof6.5meanstheactualpHislikelytobebetween6.0and7.0• Typicallyacidicindogsandcatsandalkalineinhorsesandruminants,
• Variabledependingondiet,medications,orpresenceofdisease.• Falselyincreasedifleftatroomtemperature• Abacterialurinarytractinfectionwithaurease-producingmicrobewillresultin
alkaluria.• UrinepHwillaffectcrystalluriabecausesomecrystals,suchasstruvite,formin
alkalineurine,whileothercrystals,suchascystine,forminacidicurine.• Protein
• Methods• Dipstick
• Detectsprimarilyalbumin• 30-3,000mg/dl
• Falsenegativeforotherproteins(e.g.globulins)• Falsepositivewithalkaluria
• Sulfasalicylicacidprecipitationtest• Detectsalbuminandglobulins• Usedasverification• Notaccurate
• Quantitative• Measurealbuminorproteinina24-hoururinesample• Urineproteintourinecreatinine(UPC)
• <0.2=normal• 0.2–0.4(cats)and0.5(dogs)=borderline• >0.4(cats)and>0.5(dogs)=abnormal
• Microalbumin• Semi-quantitativeELISAtestformicroalbuminuria
• 1-30mg/dl• Differentkitsfordogsandcats
• Interpretation
• Smallamountisnormal• Alkaluriacangiveslightfalsepositivereaction• Canbeseenwithinflammation,hemorrhage,orglomerulardisease.• ApositivereactionmustbeinterpretedinlightofUSG,pH,andurinesediment
examination.• Forexample,atraceamountofproteininconcentratedurineislesssignificant
thanatraceamountofproteinindiluteurine.• Presenceofotherproteins,suchasBence-Jonesproteins,willgivefalse
negativeresults.• Glucose
• Notpresentnormally• Renalthresholdis>180mg/dlinmostspecies;>240mg/dlincats.• Witheuglycemia,theamountoffilteredglucoseislessthantherenalthresholdandall
ofthefilteredglucoseisreabsorbedintheproximalrenaltubules.• Glucosuriacanresultfromhyperglycemia(duetodiabetesmellitus,excessive
endogenousorexogenousglucocorticoids,orstress)orfromaproximalrenaltubulardefect(suchasprimaryrenalglucosuriaorFanconisyndrome).
• Ifglucosuriaispresent,bloodglucoseconcentrationshouldbedetermined.• Ketones
• Detectsacetateandacetoacetate,butnotbeta-hydroxybutyrate.• Associatedwitheitherprimaryketosis(ruminants),ketosissecondarytodiabetes
mellitus(smallanimals),andoccasionallywithprolongedfastingorstarvation.• Afalsepositivereactioncanoccurwithpresenceofreducingsubstancesinurine.
• Bilirubin/urobilinogen• Bilirubinuriaoccurswhenconjugatedbilirubinexceedsrenalthresholdaswithliver
diseaseorhemolysis.• Indogswithconcentratedurine,asmallamountofbilirubincanbenormal.• BilirubinuriaisALWAYSabnormalincats• Atablettest,Ictotest®,ismoresensitive• Pigmenturiamayresultinafalsepositivereaction.
• Urobilinogen,formedfrombilirubinbyintestinalmicroflora,isabsorbedintotheportalcirculationandisexcretedrenally• Notspecificenoughtobeclinicallyuseful.
• Occultblood• A“pseudoperoxidase”methodtodetectintactredbloodcells(RBC),hemoglobin,and
myoglobin.• Apositivereactioncanbeduetohemorrhage(hematuria),intravascularhemolysis
(hemoglobinuria),ormyoglobinuria.• Thelattertwoprocessescanbedistinguishedbyexaminationofplasma;plasma
willappearpinktoredafterintravascularhemolysis,whilemyoglobinisrapidlyclearedfromplasmaresultinginclearplasma.
• Aswithothercolorimetrictestpads,discoloredurinemayyieldfalsepositiveresults.
• Apositiveresultshouldbeinterpretedwithmicroscopicexaminationofurinesediment.
• Othersemi-quantitativetestpads• Nitrite,leukocyte,andurinespecificgravity–therearetestpadsfordetectionofnitrite
(frombacterialinfection),leukocytes(leukocyteesterasefromwhitebloodcellspresentinurine),andurinespecificgravity.Thesearenotreliableforuseinanimals.
• Urinespecificgravity• Indirectmeasureofosmolality,whichisabettermeasureofconcentration
• Doonwholeurineorsupernatantaftercentrifugationifurineisdiscolored• Determinedusingarefractometerdesignedforveterinarysamples,whichincludesascalecalibrated
specificallyforcaturine.• USGforspeciesotherthancatsshouldbedeterminedusingthescalefordogs• Interfaceofdarkandlight• Massrelativetothemassofdeionizedwater(USG=1.000)
• Highlyvariable,dependingonfluidandelectrolytebalanceofthebody• Interpretationdependsonclinicalpresentationandserumchemistryfindings.• Ananimalthatisdehydratedorhasothercausesofprerenalazotemiawillhavehypersthenuric
urinewithaUSG>1.025-1.040(dependingonspecies).• Diluteurineinadehydratedorazotemicanimalisabnormalandcouldbecausedbyrenalfailure,
hypoadrenocorticism,hyperadrenocorticism,hypercalcemia,diabetesmellitus,hyperthyroidism,diuretictherapy,ordiabetesinsipidus.
• GlucosuriaincreasestherefractiveindexofurineresultinginanincreasedUSGdespiteincreasedurinevolume.
• UrineSediment
• Followingcentrifugation,decantsupernatantleavingapproximately0.5mlofurineandsedimentinthetipoftheconicaltube.
• Re-suspendpelletbytappingthetipoftheconicaltubeagainstthetableseveraltimes.• Transferafewdropsofthesedimenttoaglassslide,andacoverslipisapplied.• Examinationofunstainedurineisrecommendedforroutinesamples.• Microscopicexaminationisperformedat100X(forcrystals,casts,andcells)and400X(forcells
andbacteria)magnifications.• Contrastofthesampleisenhancedbyclosingtheirisdiaphragmandloweringthecondenser
ofthemicroscope.• StainssuchasSedistain®andnewmethylenebluecanbeusedtoaidincellidentificationbut
tendtodilutethespecimenandintroduceartifactssuchasstainprecipitateandcrystals.• Interpretresultswithurinedipstickevaluation,USG,andurinespecimenhandling• Cells
• Redbloodcells• Smallandroundandhaveaslightorangetintandsmoothappearance.• Normalurineshouldcontain<5RBC/fieldat400Xmagnification.• IncreasedRBCinurine(hematuria)indicateshemorrhagesomewhereintheurogenital
system;however,samplecollectionbycystocentesisorcatheterizationmayinducehemorrhage.
§ Whitebloodcells• SlightlylargerthanRBCandhavegrainycytoplasm.• Normalurineshouldcontain<5WBC/fieldat400Xmagnification.• IncreasedWBC(pyuria)canoccurduetoinflammation,infection,trauma,orneoplasia.• CatheterizationorcollectionofvoidedurinemayintroduceafewWBCfromthe
urogenitaltract.
Whitebloodcell(left)and2redbloodcells(right)\
• Epithelialcells
• Transitionalepithelialcells,acommonurinecontaminantderivedfromthebladderandproximalurethra,resembleWBCbutarelarger.• Theyhaveagreateramountofgrainycytoplasmandaround,centrallylocated
nucleus.• Inavoidedurinesample,squamousepithelialcellsmaybeobserved.
• Theyarelarge,ovaltocuboidalinshape,andmayormaynotcontainanucleus.• Occasionally,neoplastictransitionalcellsmaybeobservedinananimalwitha
transitionalcellcarcinomaorneoplasticsquamouscellsmaybeobservedinananimalwithasquamouscellcarcinoma.
• Cylindruria(casts)• Elongated,cylindricalstructuresformedbymucoproteincongealingwithinrenaltubules
andmayormaynotcontaincells.• Hyalinecastshaveparallelsidesandroundedends,andarecomposedofmucoprotein.
• Theymayoccurwithfever,exercise,andrenaldisease.• Cellularcasts
• Epithelialcellularcastsformfromentrapmentofsloughedtubularepithelialcellsinthemucoprotein;theymaybeobservedwithrenaldisease.
• Granularcastsarethoughttorepresentdegeneratedepithelialcellularcasts.• Mostcommontypeofcast
• Waxycastshaveagranularappearance,andarethoughttoarisefromlong-standinggranularcasts.• Theytypicallyhavesharpborderswithbrokenends.
• Afewhyalineorgranularcastsareconsiderednormal.However,presenceofcellularcastsorothercastsinhighnumbersindicaterenaldamage,andmaybeoneoftheearliestlaboratoryabnormalitiesnotedwithtoxicdamagetorenalepithelialcells(eg,gentamicin,amphotericinB).• Erythrocytecastsformbecauseofrenalhemorrhage.• WBCcastsoccurbecauseofrenalinflammation,aswithpyelonephritis.
• Fattycastsarenotcommon,butcanbeobservedwithdisordersoflipidmetabolism,suchasdiabetesmellitus.
• Infectiousorganisms
• Presenceofbacteriainurinecollectedbycystocentesisindicatesinfection.• Smallnumbersofbacteriafromthelowerurogenitaltractmaycontaminatevoided
samplesorsamplescollectedbycatheterization,anddonotindicateinfection.• Bacterialrodsaremosteasilyidentifiedinurinesediment.• Particlesofdebrismaybemistakenforbacteria.• SuspectedbacteriacanbeconfirmedbystainingurinesedimentwithGram’sstain;
however,aerobiccultureisbesttoconfirmabacterialurinarytractinfection.• Rarely,yeastandfungalhyphaeandparasiticovamaybeobservedinurinesediment.
• Theirpresenceisnotalwaysassociatedwithclinicaldisease.• ParasiticovaobservedincludeStephanusdentatus,Capillariaplica,Capillariafelis,
andDioctophymarenale.• Additionally,microfilariaeofDirofilariaimmitismaybeobservedinurinesediment.
WBCwithbacteria Capillariafelis
• Crystals
• Manyurinesedimentscontaincrystals.• ThetypeofcrystalpresentdependsonurinepH,concentrationofcrystallogenic
materials,urinetemperature,andlengthoftimebetweenurinecollectionandexamination.
• Crystalluriaisnotsynonymouswithurolithiasis,andisnotnecessarilypathologic.• Furthermore,urolithsmayformwithoutobservedcrystalluria.• Struvite
• Struvitecrystalsappeartypicallyas“coffin-lids”or“prisms”;however,theymaybeamorphousinappearance.• OccurinalkalinepH
• Struvitecrystalsarecommonlyobservedincanineandfelineurine.• Herbivoresoftenhavestruvitecrystalluriaduetoalkaluria
• Struvitecrystalluriaindogsisnotaproblemunlessthereisaconcurrentbacterialurinarytractinfectionwithaurease-producingmicrobe.• Withoutaninfection,struvitecrystalsindogswillnotbeassociatedwith
struviteurolithformation.• Someanimals,suchascats,however,doformstruviteurolithswithoutabacterial
urinarytractinfection.• Intheseanimals,struvitecrystalluriamaybepathologic.
• Calciumoxalate• OccursinacidicpH• Twoforms:
• Monohydrate:“dumb-bell”inshape.• Dihydrate:“envelope”or“squarewithX”
• Occurslesscommonlyindogsandcats• Anunusualformofcalciumoxalatecrystalsistypicallyseeninassociationwith
ethyleneglycoltoxicity.• Maybeassociatedcalciumoxalateurolithformation.
• Commoninhorsesandcattle• Calciumcarbonate
• Commoninhorses,rabbits,guineapigs,andgoats• OccursinalkalinepH
• Variablysizedandoftenappearaslargespheroidswithradialstriations• Mayalsobesmallercrystalswithround,ovoid,ordumbbellshapes
• Colorlesstoyellow-brown• Ammoniumurate
• OccurinacidicpH• Yellow-brownsphereswithirregular,spinyprojections;however,theymayalsobe
amorphous• Ammoniumaciduratecrystalssuggestliverdisease(eg,portosystemicshunt).• Certainspecies,suchasbirdsandreptiles,andcertainbreedsofdogs,specifically
Dalmatians,cannormallyhaveammoniumaciduratecrystalluria.• Cystine
• Cystinecrystalsaresix-sidedandofvariablesize.• Theyoccurinacidicurine.• Presenceofcystinecrystalsrepresentsaproximaltubulardefectinaminoacid
reabsorption.• Cystinuriahasbeenreportedtooccurinmanybreedsofdogsandrarelyincats,but
Dachshunds,Newfoundlands,Englishbulldogs,andScottishterriershaveahighincidenceofcystineurolithiasis.
• Bilirubin• Bilirubincrystalsoccurwithbilirubinuria;however,thesemaybenormalinsmall
numbersindogs.
Ammoniumuratecrystals Bilirubin Cystine
Calciumoxalatemonohydrate Calciumoxalatedihydrate Struvite
• Lipid• Fatdropletsarecommonlypresentinurinefromdogsandcatsandmaybemistakenfor
RBC.However,theyoftenvaryinsizeandtendtofloatonadifferentplaneoffocusthantheremainderofthesediment.Theyarenotconsideredtobepathologic.
• Spermatozoa• Spermatozoamaybeobservednormallyinurinecollectedfrommaledogs.
• Artifact• Occasionally,plantmaterialmaybeobservedinurinesamplescollectedbyvoiding.
Whenpresent,theyindicatecontaminationoftheurinesample,andarenotpathologic.
• Talcpowdergranulesmaybeobservedinvoidedsamplesifthecollectoriswearinggloves
• Enzymuria.• Enzymaticactivity,usedasamarkerforAKI,belongtoenzymesthatarefoundwithintherenaltubularcells.• Theseenzymesaretoolargetobefilteredthroughanormalglomerulus,andsointheabsenceofprofound
glomerulardisease,ariseintheurinaryactivityofsuchenzymesistypicallycausedbyacutedamagetothetubulesandleakagefromthetubularcells.
• Urinaryenzymes,GGT,andNAGarethemostcommonlyusedandmostpracticalenzymestoassessurinaryactivity.• NAGisfoundwithintheproximaltubularlysosomesandGGTwiththeproximaltubulebrushborder.• Theactivityoftheseenzymesisasensitivemethodofdetectingacutetubularkidneyinjury,moresensitive
thanchangesinglomerularfiltrationrate,serumbiochemistry(azotemia)andclinicalsigns.• Changesinurinaryenzymeconcentrations,GGTandNAG,canbeestimatedbyenzymetocreatinineratioson
spoturinesamples,deeming24-hoururinecollectionsnotabsolutelynecessary.• Examplesofsuchcasesincludetheuseofrenaltoxicchemotherapeuticagents,theuseofaminoglycosides,a
veryrecentoverdoseofanon-steroidalanti-inflammatorydrug(NSAID)ortheuseofanNSAIDinarenalcompromisedpatient.
• Point-of-caretestingforurinarytractinfections• Thesetestsmaydetectpresenceofbacteria,determinetypeofbacteria(Gram+versusGram-),identifythe
bacterialorganism,and/orprovidesusceptibilitytoalimitednumberofantimicrobialagents• Otherinfectiousagents
• UrinemaybesubmittedforLeptospirosisPCRfordiagnosisofleptospirosisorforfungalPCRfordiagnosisoffungalinfectionssuchasBlastomycosis,Aspergillus,andHistoplasmosis
• Bladdertumorantigentest(VBTA)• TheVBTAcanbeusedasascreeningtestfortransitionalcellcarcinomaindogs.• Theresultsarenotspecificandnon-neoplasticdisease(e.g.urinarytractinfections,hematuria,etc)cangive
positiveresults.• Anegativetest;however,ismeaningfulinthatatransitionalcellcarcinomaisnotlikelytobepresent.• Thistestmaybeusefulforroutinescreeningofdogsathigherriskofdevelopingtransitionalcellcarcinoma(e.g.
Scottishterriers)thatdonothaveothersignsorlaboratoryfindingsoflowerurinarytractdisease.