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CVM6105SmallAnimalUltrasoundSupplementalNotes,Spring2015KariL.Anderson,DVM,DACVRProfessor,MedicalImagingOffice:C350Phone:612‐625‐3762Email:[email protected] NotespagesUpperurinarytract 2‐10Lowerurinarytract 11‐16Reproductivetract 17‐22Gastrointestinaltract 23‐26Adrenalglands 27‐31References 32‐33Thesesupplementalnotesshouldnotreplaceultrasoundtextbooks.Pleaserefertothesyllabusforreferencetextbookswhichcanbeusedforadditionalcaseexamplesandmorethoroughdescriptionoffindingsanddifferentials.
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UltrasonographyoftheUpperUrinaryTract
Ultrasoundoftheupperurinarytractinveterinarymedicineisaroutineprocedurewhichcanprovideimportantanatomicinformationregardingsize,shapeandinternalarchitectureofthekidneys.Ultrasoundcanoffermoreinformationthanconventionalradiography,especiallyinthepresenceofemaciation,retroperitonealandperitonealeffusion,andimpairedrenalfunction.Ultrasoundcanalsobeusedtoguideinvasiveproceduressuchasfine‐needleandcorebiopsy,percutaneouspyelocentesis,andantegradepyelography.Itshouldbeunderstoodthatultrasoundhasitslimitations.Itcanbedifficulttoimagekidneys(especiallytherightkidney)inlarge/giantbreeddogsandinpatientswithexcessivebowelgas.Thenormaluretercannotbeimaged,andultrasounddoesnotprovideinformationregardingrenalfunction.Additionally,itcanbemoredifficulttolocalizeureteralcalculithanwithradiographs,especiallyiftheureterisnotespeciallydilatedandthepatientisnotcooperative.Anexcretoryurogramissuperiortoultrasoundforqualitativeassessmentofrenalfunction,visualizationofnon‐dilatedureters,identificationofsubtlepyelectasisandureterectasis,andlocalizationofureteraltrauma.Nuclearscintigraphy(GFRscan)canbeperformedforassessmentofindividualkidneyGFR.
Indications:evaluationofabnormalradiographicfindings(abnormalsize,shape,position
ornon‐visualizationofkidneys),evaluationofinternalrenalarchitecture,azotemia/uremia,hematuria,recurrenturinarytractinfections,cranialretroperitonealmass,screeningforPKD
Transducer:thehighestfrequencytransducer(atleast7.5MHz)shouldbeusedinorder
toobtainhigh‐qualityimagesofthekidneys,pelvisandureters;occasionallyalowerfrequencytransducermaybenecessaryinlargepatientsorinpatientswithsevereascites
ScanPlane:positionanimalindorsalrecumbency,obtainsagittalandtransverseimages
routinely–supplementaldorsalimagesareoftenobtainedaswell;therightkidneymayhavetobeimagedthroughtheright11‐12thintercostalspace(dorsalandtransverseimages);theorientationofthekidneytothetransducercanmarkedlyalterthesonographicappearance
Artifacts:bowelgascanimpedeimagingandleadtoimagingartifactsofthekidneys–
considerabletransducerpressureshouldbeusedtodisplaceoverlyingintestine;acousticshadowingcanbeseenduetothenormalrenalsinusfat;edgeshadowingartifactswilloftenbeseenattheedgesoftheroundkidneypoles
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NormalSonographicAppearance
Location: Leftkidney:caudaltogreatercurvatureofstomach,medialandoftenventralto
spleen,lateraltoaorta Rightkidney:liesinrenalfossaofcaudateliverlobe,morecranialthanleft,ventral
andoftenmedialtoduodenum,lateraltocava RenalAnatomy:
therenalmedullaisseparatedintomultiplesectionsbypelvicrecessesandinterlobarvessels,whicharerepresentedbyparallellinearhyperechoicstructures;mosttubulesofthecollectingsystemarelocatedinthemedulla
thearcuateandintralobararteriescanbeseenasdiscreteechogenicitiesatthecorticomedullaryjunctionandwithinthecortex,respectively
essentiallyallglomeruliarelocatedintherenalcortex bothcortexandmedullacontainrenaltubules,vessels,andconnectivetissue
NormalSonographicAppearance:Thekidneysarebeanshapedstructureswithanindentationonthemedialaspectatthelevelofthehilus.Inthedog,theleftkidneyismorelooselyattachedthantheright;andinthecat,bothkidneysaremorelooselyattachedthaninthedog.Becauseofthis,lesstransducerpressuremaybeneededsothatthekidneysarenotdisplacedfromtheirnormallocation.Thespleencanbeusedasanacousticwindowtoimagetheleftkidneyinthedog.Thenormalrenalpelvisandureterarealmostneverseensonographically.Theymaysometimesbevisualizedasechogeniclinearstructures,butshouldnotbedistended.Distinctechogenicregionsofthekidneyscanberecognized.1)Thereisabrightcentralechogeniccomplexthatrepresentstherenalsinusandperipelvicfat.Thefatmaycauseanacousticshadow,anditisimportanttodifferentiatethisfromacousticshadowingcausedbymineralization.2)Thereisahypoechoichomogenousregionsurroundingthepelvisthatisthemedulla.3)Thereisanouterzoneofintermediateechogenicityandfinespeckledechotexturewhichistherenalcortex.4)Thereisathinperipheralbrightlinearechorepresentingthefibrousrenalcapsule.Therenalpelvicrecessesandinterlobarvesselsareoftenseenasmultiple,evenlyspaced,linearechogenicitiesextendingperpendicularlyfromtherenalpelvicregion.Thereshouldbedistinctdemarcationbetweenthecortexandthemedulla.Renalcorticalechogenicityissimilarorslightlylessthantheliverparenchymalechogenicity.Renalcorticalechogenicityshouldbequiteabitlessthanthesplenicparenchymalechogenicity.Itisimportanttocomparetheorgansatthesamedepth.Itis
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alsoevidentthattheorganechogenicityrelationshipmayvarywithfrequencyandtypeoftransducerused.
Thefelinerenalcortexismoreechogenicthanthedog,withamarkeddifferencefromthemedulla.Thisisduetofatvacuolesinthecorticaltubularepithelium.Thecorticalechogenicityisalsomorevariableincats.Thustherelationshiptootherparenchymalorgansisoftendifferentinthecat.
Duringdiuresis(withfurosemide)ithasbeenshownthatthemedullawillincreaseinsize,aswellasdecreaseinechogenicity,likelyfromtheincreasedfluidflow.Physiologicortherapeuticdiuresiscanleadtominimalbilateralorunilateralpyelectasisinmanypatients(2‐3mm).Inonestudy,noureterectasiswasnotedwithsalinediuresisin25dogs.Kidneyscanbemeasuredfromanultrasoundimageoptimizedforlength,width,andheight.However,thesemeasurementsarebesttakenfromradiographs.Indogs,althoughthereisagreatvariationinkidneymeasurements,thereisapositivecorrelationofkidneylengthandvolumewithbodyweight.Therefore,kidneysizejudgmentsindogsarerelativelysubjective.Becausecatshaveamorestandardbodysize,sonographicmeasurementsaremoreuseful.Inasmallstudyofyoungcats,kidneylengthwas3.66±0.46cm,widthwas2.53±0.3cmandheightwas2.21±0.28cm.Therenalcortexhasbeenreportedasmeasuringbetween3‐8mminthedogand2‐5mminthecat.Themedullaryrimsignisanon‐specificandoftennormalfindingseenindogsandcats.Thispresentsasathinlinearhyperechoicband(1‐3mmthick)intheouterzoneoftherenalmedulla,severalmminsideandparallelingthecorticomedullaryjunction.Incatsithasbeenshownthatthisiscausedbynon‐pathologicmicroscopicdepositsofmineralwithinmedullarytubularlumens.Itistruethatthisfindingcanbeseenwithpathologicconditionssuchashypercalcemicnephropathy,nephrocalcinosis,acutetubularorcorticalnecrosis,FIP,andethyleneglycoltoxicity.Themedullaryrimsigncanbeduetomineralization,necrosis,congestion,and/orhemorrhageandattributedtoaninsulttotherenaltubulesinthedeepestportionofthemedulla,whichismostmetabolicallyactiveandthereforemoresusceptibletoischemia.Inonestudyof32dogs,ofdogsinwhichthemedullaryrimsignwastheonlysonographicfindinginthekidneys,72%hadnoevidenceofrenaldysfunction;ofdogsthathadthemedullaryrimsignincombinationwithothersonographicrenalabnormalities,78%hadrenaldisease.Thusthemedullaryrimsignisnotanaccurateindicatorofrenaldisease.
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AbnormalSonographicAppearance
Ultrasonographicpatternsandechogenicityaremorespecificforfocalormultifocalrenalabnormalitiesandareoftennon‐specificfordiffuserenaldisease.Ultrasoundhaslimiteduseindistinguishingbetweenbenignandmalignantlesions.Additionally,findingsmaychangewithdurationofdisease.Becauseofthenon‐specificityofmanyrenalsonographicabnormalities,thesonographicfindingsshouldbecorrelatedwithsignalment,history,physicalexam,andbiochemicalparametersinordertorefineadifferentialdiagnosis.Finally,afine‐needleorcorebiopsymaybeindicatedforadefinitivecytologicalorhistopathologicaldiagnosis.
Diffuseabnormalitiesofrenalparenchyma Increasedcorticalechogenicitywithpreservedcorticomedullarydifferentiation
generallyassociatedwithdiffuseinfiltrativeprocess thisisanabnormalbutnon‐specificchange differentialsinclude:glomerularandinterstitialnephritis,glomerulosclerosis,
acutetubularnecrosisornephrosissecondarytotoxicagentsorethyleneglycol,end‐stagerenaldisease,parenchymalcalcification(nephrocalcinosis),amyloidosis,FIP,oftendiffuserenallymphosarcomaincatsorsometimesdiffusesmallcysts
IncreasedoverallrenalechogenicitywithdecreasedCMdifferentiation
chronicinflammatorydiseases(pyelonephritis),renaldysplasia,GNdisorders “end‐stage”kidneys‐thesekidneysaretypicallysmall,irregular,diffusely
echogenicwithpoorvisualizationoftheCMjunctionandtheinternalarchitecture
Decreasedechogenicity lymphomamayresultinill‐definedmultifocalhypoechoicnodulesthatappearas
diffusehypoechoicdisease inpeople,mayresultfromacutediseasesassociatedwithedema
Becauseofthenon‐specificnatureoffindingsmakingitdifficulttodistinguishclinicallynormalkidneysfromacuteandchronicrenaldiseaseprocesses,theuseofotherultrasoundparameters,suchassize,shape,contourandinternalarchitecturecanbehelpful.Kidneysaffectedbychronicdiseaseprocessestendtobecomesmall,irregular,andmorediffuselyhyperechoic.Duetofibrosis,architecturaldistortionscanbepresent,aswellasdystrophicmineralizationespeciallyintheregionofthecollectingsystem.Kidneysaffectedbyacuteprocessescanbecomeenlargedandhyperechoicwiththecontourgenerallyremainingsmooth.Protein‐losingglomerulardiseases,suchasGNandrenalamyloidosis,cannotbedistinguishedfromotherdiffuserenaldisorders.Affectedkidneyscanvaryinsizeaccordingtothechronicityofthediseasebutarecommonlyhyperechoic.
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Focalabnormalitiesofrenalparenchyma
Renalcysts:
maybesolitaryormultiple,mayinvolveoneorbothkidneys sonographiccharacteristicsoftruecyst:roundorovoid,echo‐freecontents,
smooth,sharplydemarcatedthinwallswithadistinctfar‐wallborder,strongacousticenhancement(throughtransmission)
maybewithinmedullaorcortex maydeformtherenalcontouriftheyarelargeorifpolycysticdiseaseispresent,
maydisplace/distort/dilatethecollectingsystem acquired:secondarytoinflammationorobstructionofrenaltubules Polycystickidneydisease:
» containmultiplefluid‐filledcystsderivedfromrenaltubules» inherited:Cairnterriers,long‐hairedcats» morecommonincats,mayhaveconcurrenthepaticcysts» oftenassociatedwithclinicalrenaldisease/failureascystsdisplacenormal
functioningtissue Otherdifferentialsmustbeincludediftherearethickorirregularwalls,internal
septations,echogeniccontents» Ddx:complicatedcyst,hematoma,infarct,granuloma,abscess,tumor» Fine‐needlebiopsywouldbenecessaryfordiagnosis
Renalnodulesandmasses: Commonlyneoplastic(primaryormetastatic),mayseegranuloma(rare) Nodulesandmassesmayappearhypoechoic,isoechoic,orhyperechoic;the
patternisnon‐specific,althoughuniformlyhypoechoicmasseshaveoftenbeenassociatedwithlymphoma
Renallymphomaisgenerallyeffectsbothkidneys;theremaybemultifocalhypoechoicnodulesandsubcapsularinfiltrate;theremaybemoreuniforminfiltrateaswell
Massesmaycontainsomeareasofhemorrhageornecrosis,whichappearssonographicallyasmixedechogenicitywithpossiblecavitaryareas
Mostcommonpatterniscomplexorhypoechoicmass Althoughprimaryrenaltumorsareuncommon,themostcommontumorisrenal
carcinoma,whichusuallybeginsatonepoleofthekidneyandgenerallyproducesfocalhyperechoiclesions;oftentheotherkidneywillbeaffected
mustobtainfine‐needleorcorebiopsyfordefinitivediagnosis Renalinfarct:
wedge‐shapedortriangularwithabroaderbaseatthecapsularsurface acutelesionsarehypoechoic(1‐7days) lesionsgraduallybecomehyperechoicastheyfibroseandeventuallyleadto
depressionsinthecortex
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Focalhyperechoicareasinrenalcortex:
causes:neoplasia,calcification,fibrosis,gas FNAorbiopsynecessaryfordefinitivediagnosis
SpecificRenaldiseases
AcuteRenalFailure: causes:ATN,corticalnecrosis,acuteinterstitialnephritis,diseasesofthe
glomeruli,lymphosarcoma sonographicfindingsareoftenunremarkable kidneysmaybeslightlyenlarged echogenicityofcortexmayrangefromhypoechoictohyperechoic
ChronicRenalFailure: causes:GN,chronicpyelonephritis,polycysticrenaldisease,autoimmune
disease,nephrotoxins sonographicfindingsarenon‐specific generally,ultrasounddoesnotprovidemuchinformationandmaynotbe
indicatedexceptincasesofanacutecrisisontopofchronicrenalfailure(evaluatingforobstructionorinfection)
findingsrangefromnormalkidneystohyperechoic,irregularlyshapedkidneys renalfunctioncannotbedirectlycorrelatedwithkidneysizeandechogenicity
Renaldysplasia:
disorganizeddevelopmentofrenalparenchymaduetoanomalousdifferentiation;maybefamilial(Lhasaapso,Shihtzu,cats,tonameafew)orsecondarytofetal/neonatalinfectionorteratogenesis
sonographicfindingsaresimilartoanychronicinfiltrativerenaldisease,andthediagnosisisbasesupontheyoungageoftheanimalandrenalbiopsy
generallythekidneysaresmall,misshapen,andhyperechoic theinternalarchitectureisabnormalandthereispoorCMdifferentiation cystsanddilateduretersmaybepresent
Pyelonephritis: inflammationofrenalpelvisandrenalparenchyma acutepyelonephritis:
» possiblerenomegaly» mayhaveageneralizedhyperechoiccortexormedulla,focalormultifocal
hyper‐orhypoechoicareasinthecortexandmedulla» generallythereispoorCMdifferentiation» mayseeahyperechoiclineparallelingtherenalpelvis,renalrecesses,and/or
proximalureter» therenalpelvismaybedilatedwithanechoicorhyperechoicdebris
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» mildcasesmayhavenoabnormalities chronicpyelonephritis:
» changesaregenerallysecondarytofibrosisofthekidney» oftenthekidneysaresmallandirregularlyshaped» mayhaveincreasedcorticalandmedullaryechogenicitywithpoorCM
differentiation» mildtomoderatepelvicandproximalureteraldilationwithdistortionofthe
collectingsystemgenerallypresent;urinemaybeanechoicorcontainhyperechoicdebris
Peri‐renalpseudocyst:
encapsulatedaccumulationoffluidsurroundingrenalcortex documentedinbothdogsandcats,morecommonincats causes:trauma,neoplasia,ureteralobstruction,infections maybeassociatedwithprimaryrenaldisease sonographicallyappearsasellipticalanechoicorhypoechoicfluidcollecting
subcapsularlyandhavingmarkeddistantenhancement mayhaveinternalseptaorlowlevelsofinternalechoes
Disordersoftherenalpelvis,collectingsystemandureters
Renalpelvicdilation:
recognizedbyseparationofthenormal,uniformlyhyperechoiccentralrenalsinusechoesbyananechoicspace
thedegreeofdistentionisfromminimaltoadvanced;advancedcasesarereadilyapparentbecausethedilatedpelvicdiverticulaandproximalureterareeasilyvisualized
differentiatetheureterfromtherenalvein;therenalveincanbefollowedtothevenacava
excretoryurographyisthemostsensitivemethodfordetectingsubtlepelvicandureteraldilation
milddilationmaybeseeninstatesofdiuresis Ddx:congenitaldisease,pyelonephritis,obstructiontourineflowby
intraluminal,mural,orextramuralcauses Hydronephrosis:
» themostdramaticformofpelvicdilation–canbefrommildtomoderatedegree
» causesinclude:ureteralobstructionfromabladder,urethral,orprostatictumorinvolvingthetrigone;obstructionoftheureterbyureteralinflammation,calculi,extrinsicmasses,orstrictures;ectopicureter
» inlongstandingcasesonlyathinrimofrenaltissueremains(parenchymalatrophy)withseveralechogeniclinearbandsextendingfromthehilustowardthecapsulerepresentingvesselsandassociatedfibroustissue
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» sonographicappearancewillbeofdilatedanechoicrenalpelvisandrecesseswithdistantenhancement;aspelvisdilatesitwilldistortandgraduallyreplacethemedullaandfinallythecortex;initiallythedilationwilltaketheshapeoftherenalrecessesandwilleventuallybecomeoval
Calculi:
bothradiopaqueandradiolucentcalculiwillbeseensonographically sonographicappearanceisanintensehyperechoicfocuswithstrongacoustic
shadowing;thismaybewithintherenaldiverticula,therenalpelvis,ortheureter
thedetectionofshadowingisincreasedbyhavingthecalculuswithinthefocalzone,usingahigh‐frequencytransducer,andbyloweringtheoverallgain
mayseeaccompanyingdilationofthepelvisordiverticula smallcalculiorrenalparenchymalcalcificationmaybedifficulttodistinguish
fromthenormalshadowingofthewallsoftherenalcollectingsystem(excretoryurogramwouldberecommended)
bloodclotsormasseswithinthepelvisaremorerareanddonotproduceacousticshadowing
Ultrasound‐guidedfine‐needleandcorebiopsy:Asmentionedmanytimesinthesenotes,manyofthesonographicfindingsareverynon‐specificinrenaldisease.Incertaincases,itwillbenecessarytoobtainafine‐needleorcorebiopsyaspartofthework‐upofthecaseinordertoestablishadiagnosis,therapeuticplan,and/orprognosis.Afine‐needlebiopsyofthekidneyisarelativelysafeprocedure.Thecortex,medulla,orpelvisofthekidneycanbesampled.Suspicionofthefollowingentitieswouldindicateconsiderationofafine‐needlebiopsy:lymphoma,metastaticorprimaryneoplasia,FIP,abscess,fungalinfection,ortoconfirmacyst.Acorebiopsyofthekidneyisamoreinvasiveprocedurerequiringheavysedationoranesthesia.Indicationswouldincludeglomerulardisease,acuterenalfailurethatisnotresponsivetomedicalmanagement,orrenalneoplasianotdiagnosedbyafine‐needlebiopsy.Abiopsyshouldnotbeperformedinpatientswithuncorrectablecoagulopathy,uncontrolledhypertension,extensiveinfection,hydronephrosis,PKD,orchronic/end‐stagerenaldisease.Complicationscanincludehemorrhage,hematuria,fibrosis,andotherlesscommonproblems.Itshouldbenotedthatgenerallyonlythecortexissampled;thusmedullarydiseasecannotbediagnosedwiththistechnique.
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Dopplervascularstudies:Dopplerexaminationofthekidneyshasemergedfromhumanstudies.DopplersonographyutilizestheconceptoftheDopplereffect,anapparentshiftinsoundfrequencyassoundwavesarereflectedfromthemovingbloodcells.Ifmotionistowardthetransducer,thefrequencyofthereturningechoeswillbehigherthanthetransmittedsound;andifmotionisawayfromthetransducer,thefrequencyofthereturningechoeswillbelowerthanthetransmittedsound.ThedifferencebetweenthereceivedandtransmittedfrequenciesisknownastheDopplershift.AgreatervelocitywillresultinagreaterDopplershift.Usingpulsed‐waveDopplertoinvestigateaspecificvesselwillresultinaspectralwave‐formplottingtimeversusvelocityforthevessel.Theultrasoundcomputerwillhavesoftwaretoallowforcalculationspertainingtotheinformationgathered.Dopplersonographycanprovideadditionalinformationinpatientswithurinarytractobstruction,acuterenalfailure,renaltransplantsandrenalneoplasia.Commonlytherenalvascularresistanceisevaluatedbycalculatingaresistiveindex(RI)withtheuseofDopplersonography.TheRIiscalculatedbysubtractingthediastolicfrequencyfromthepeaksystolicfrequencyanddividingtheresultbythepeaksystolicfrequency.AnRIoflessthan0.70isconsiderednormal.Withincreasedvascularresistance,thediastolicflowisreducedingreaterproportionthanthesystolicflowandtheRIwillincreaseinvalue.TheRImaybeabletodifferentiatebetweenpre‐renalfailure(normalRI)andacuterenalfailureoracutetubularnecrosis(elevatedRI).TheamountofRIelevationandthereturntonormalmaybeabletoofferaprognosis.TheRIisoftenelevatedinacuteureteralobstruction,whichcanhelpdifferentiateobstructivedilationfromnon‐obstructivedilationofthecollectingsystem.Finally,anelevatedRIismaybeseenwithacuterejectionofrenaltransplants.
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UltrasonographyoftheLowerUrinaryTractTheurinarybladderisideallysuitedfortheultrasonographicexaminationbecauseoftheexcellentacousticpropertiesofthefluidnatureofurineandthesuperficiallocationoftheurinarybladder.Ultrasonographycanprovideinformationrelativetothecapacityofthebladder,changeinbladderoutline,changesinthethicknessandstructureofthewall,identificationofluminalstructuresandmuralmasses,andidentificationofextrinsiclesionswhichmaydisplacethebladderordistortthewall.Indications:chronicorrecurrentUTI,stranguria,dysuria,hematuria,caudalabdominal
massTransducer:thehighestfrequencytransducerpossible/availableshouldbeusedinorder
toaccuratelyassessthebladderwall–atleasta7.5MHztransducer;occasionallyalowerfrequencytransducermaybenecessaryforevaluationofadjacentstructuresinalargepatient
Scanplane:positionpatientindorsalrecumbency,examineinsagittalandtransverse
planesArtifacts:bothusefulanddetrimentalartifactswillbeencounteredduringimagingofthe
urinarybladder Detrimentalartifacts:slicethickness,near‐fieldreverberation,sidelobe
(“pseudosludge”),hypoechoicpseudolesionor“walldefect”,colonmimickingstoneormass
Usefulartifacts:acousticshadowing
Simpletechniquessuchasrepositioningthetransducer,changingtheimagingplane,usingastand‐offpadorstandingthepatientandimagingfromventralmayaidinidentificationofartifactsfromtruelesions.
Patientpreparation:theurinarybladdershouldbemoderatelydistendedforaccurate
evaluationofmucosaldetailandwallthickness,aswellastoallowforevaluationofthebladderneckandproximalurethra.Imagingthepatientfirstthinginthemorningbeforeurinationisideal.Ifthebladderisnotdistendedenoughforevaluation,aurinarycathetermaybeplacedandthebladderdistendedwithsaline.Becarefulnottointroduceair,whichcouldsignificantlyhinderevaluation.Alternatively,thepatientcouldbeimagedatalatertimeafterthebladderhasnaturallyfilledwithurine.
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NormalSonographicAppearance
Theurinarybladderisanecho‐freecysticstructure.Thebladdershapevariesfromroundtoovoidtooblong.Therearefourlayersofthebladderwall:themucosa,thesubmucosa,themuscularlayer(innerlongitudinalmuscle,middlecircularmuscle,outerlongitudinalmuscle),andtheserosalsurface.Theselayersarenotusuallyclearlydemarcated.Generallytwothin,parallel,hyperechoiclinesseparatedbyahypoechoiclineareseen:1)hyperechoicserosa/perivascularfatinterface,2)hypoechoicmuscularis,and3)hyperechoiclineoflaminapropriasubmucosaparallelingmucosalinterface.Whenthebladderisnearlyempty,themucosalandsubmucosallayersmaybeabletobedifferentiated.Theproximalurethrainthefemalecanbeimaged,butthemiddleanddistalportionswillnotbeimagedduetoacousticshadowingfromthepubicbone.Almosttheentireprostaticportionoftheurethracanbeimagedinthemale(itisnotalwayswelldemarcatedfromtheprostaticparenchyma),andthemembranousandpenileurethra,wherenotwithinthepelviccanal,canalsobeimaged.Thenormalbladderwallthicknessis1‐3mmindogsand1.3‐1.7mmincats.Themeanthicknessis1.4mmwithmoderatedistensionand2.3mmwithminimaldistentionindogs.Thebladderwallthicknessdecreasesasthebladderdistensionincreasesandincreasesasthesizeofthepatientincreases(canbe1mmthickerinalargerdog).Thebladderwallisfairlyuniforminthicknessthroughout.Theentranceoftheuretersmayberecognizedbyasmallelevationofmucosalocatedoneithersideofmidlineatthetrigoneregion(theureteralorifices).Onemayseeperiodicstreamingofbright,specularechoesattheentranceoftheureters,astheuretersintermittentlyemptyintothebladder.Thisisknownasureteraljeteffect.Thiscanbedetectedbothwithreal‐timegrayscalesonography,aswellascolor‐flowDopplersonography.Themostlikelyreasonfortheureteraljeteffectisduetotemperatureordensitydifferencebetweenureteralandbladderurine;howeverothertheoriesincludemicrobubblesofparticulatematterinurineandturbulenceorcavitationattheureteralorifice.Tofacilitateviewingoftheureteraljets,havethepatienturinate,withholdwaterforseveralhoursandthenallowfreeaccesstowaterpriortoimaging.Alternatively,adiureticmaybegiventoassistinfindingtheureteralorifices.Theureteraljeteffectcanbehelpfulindemonstratingpatencyoftheuretersoridentifyingtheureteralorificeincasesofectopicureters.
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AbnormalSonographicAppearance
Heterechoicurine: mobileechogenicparticlesfloatingfreelywithinthelumen Ddx:crystals,proteinaceousmaterial,cellulardebris,fatdroplets(especiallycats),
gas alargeamountofsedimentmayaccumulateinthedependentportionofthe
bladder» urinary“sludge”:cellulardebris,mucin,blood» agitationofthebladderwilldemonstratethemobility
Gasbubbles:» occursecondarytocatheterization,cystocentesis,gas‐formingbacterial
infection» mayappearasfloating,hyperechoicfociinthelumen» foundinthenon‐dependentportionoftheurinarybladder» generallycauseareverberationartifactor“dirtyshadow”
Cysticcalculi:
bothradiopaqueandradiolucentcalculiaredetectablewithultrasound ultrasoundappearanceisfocal,dependent,hyperechoic,curvilinear
echogenicitieswhichgenerallychangepositionaspatientpositionchanges associatedacousticshadow
» notallstoneswillshadow(butmostwill!)» thedegreeofshadowingcorrelateswithchemicalcomposition,thelocationof
thecalculusinrespecttothefocalzone,andthefrequencyofthetransducer anaccuratecountofcalculiandaccuratemeasurementofcalculiisdifficult
sonographically(doublecontrastcystographyisrecommended)–higherfrequency(7.5MHz)transducermoreaccurate
onemayidentifyshadowingmineralizeddependentsediment,suchasthatfoundwithfelinelowerurinarytractdisease
falsenegativeexaminationscanoccur» emptybladder» sand/calculustoosmalltoresolve(<0.1‐0.2cm)» poorexam
Bloodclots:
generallytheultrasonographerisexpectingthisfindingbaseduponhistory clotsoccursecondarytotrauma,bleedingdisorders,infection,neoplasia ultrasoundappearanceisgenerallymediumechogenictomildlyhyperechoic,
nonshadowingechogenicities,withanirregular/amorphousshape bladderlumenmaybefilledwithlacyechogenicmaterial generallyaremobileandsettletothedependentportionofthebladder
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maybeadherenttothebladderwallandhaveassociatedmucosalirregularity(Ddx:muralmass);lookforunderlyingbladderwallthicknesswhichmorelikelyindicatesneoplasia
onemayagitatethebladderordopositionalstudiestoassessattachment
Cystitis: canbesterileorseptic ultrasoundappearanceisgenerallyathickenedbladderwalldecreasedin
echogenicity,oftenwithasmoothoutlineofthemucosalsurface,althoughthemucosamaybeirregular;therecanbearoundedintraluminalmass» wallthickeningisusuallymostpronouncedcranioventrally» gradualtransitiontonormalmucosa» thickeningmaybecomegeneralizedinseverecases
theurinemaybeheterechoicorcontainsuspendedordependentechogenicmaterialwhichrepresentscellulardebris(Ddx:crystals,fatdroplets)orcalculi
Polypoidcystitis:» rare;causeunknownbutisduetochronicinflammationofmucosa» multiplesmallpolypoidorlargerpedunculatedmassesprojectingintolumen
whicharegenerallyisoechoictothebladderwall» maybeshortorlongandlocatedcranioventraland/orcraniodorsal» generallyassociatedbladderwallthickening» mustconfirmwithbiopsytorule‐outneoplasia–polypshavenohistologic
evidenceofneoplasia Granulomatouscystitis:
» willhaveaveryirregularbladderinternalsurface Emphysematouscystitis:
» causedbygas‐formingbacterialinfection(forexample,E.coli)» multifocalhyperechoicareasofintramuralgaswithvariableshadowingand
reverberation» gasdoesn’tchangewithpositionalchangeofpatient» mayhaveintralumenalgasaswell
Neoplasia: only1%ofallcaninetumors;catsalsogetbladderneoplasia themostcommonneoplasiainthedogistransitionalcellcarcinoma(TCC);other
tumortypes:squamouscellcarcinoma,adenocarcinoma,undifferentiatedcarcinoma,rhabdomyosarcoma,metastaticdisease
ultrasoundappearanceisgenerallyofafocalecho‐complexhypoechoicormediumechogenicity(tobladderwall)masswithabrupttransitionbetweentumorandnormalmucosa
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» characterizedbyfocalwallthickeningwithanirregular,sessilemassextendingintothebladderlumen;themucosalsurfaceisoftenirregular;mayseedystrophicmineralization
commonly,bladderneoplasiaoccursatthetrigoneregion,bladderneck,andurethra;however,neoplasiacanoccuratanylocationwithinthebladder
thesizeofthelesionisthemostimportantfactorintherateofdetection;bladderdistentionalsoplaysanimportantrole;ventrallesionsmaybemissedduetoimagingartifacts
carefullyevaluateformetastasistoregionallymphnodes,obstructionofureters,involvementofurethra
Bladderrupture: mayseedefectofbladderwallatlevelofrupture(orurinarycatheterprotruding
intoperitonealspace)» bewaryofthehypoechoicpseudolesionpreviouslydescribed
bladderwallmaybethickfromedemaand/orhemorrhage mayutilizecontrastcystosonography
» thisinvolvestheinjectionofmicrobubbledsaline(salineandairagitatedtogether)throughtheurinarycatheter
» visualizemicrobubblesinfluidaroundthebladder positive‐contrastcystographymaybemorereliablefordiagnosisofrupture
Distalureter:
onlyseenwithultrasoundiftheureterisdilatedfromectopia,ureteritis,orobstruction
commonly,primaryneoplasiaofthebladder,urethra,orprostatecausesureteralobstruction
occasionallycalculiormassesobstructingtheureternearthebladderareidentified
ureterocele:acongenitaldilationoftheterminalureterresultingfromstenosisoftheureteralmeatus;seenasasmooth,well‐definedcysticstructurewithinornearthebladderwallinthetrigoneregion;theaffecteduretermaybeectopicandhydroureterorhydronephrosismaybepresent
Urethralpathology:
ultrasoundhaslimitedusefulness maydetecturethraltumors,evaluateforlocalinvasion,localizecalculi urethraltumorsgenerallyappearassymmetricwallthickeningwithirregular
mucosalsurface,mayextendintotheneckofthebladder retrogradepositivecontrasturethrographyorcystographyisthebestmethodto
characterizethelocationandextentofpathology
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Ultrasound‐guidedfine‐needleandcorebiopsy:Afine‐needleorcorebiopsymaybeveryimportantinthework‐upofbladder/urethraldiseaseasonecannotdifferentiatepolypoidcystitis,granulomatouslesions,andneoplasiabyappearancealone.Complicationsofthisprocedureincludetumorseedingalongthetractofthebiopsy.Thisisararecomplication(estimatedfrequencyof0.009%inhumans),buthasbeenreportedindogs.Itismorecommonwithcertaintumors,suchasurologictumorsandprostatetumors.Thelikelihoodmayincreasewithlargerboreneedlesandincreasingnumberofneedlepasses.Considerusingultrasoundtoguideacatheterorendoscopicbiopsyviaurethralaccesstoavoidthecomplicationoftumor‐trackseeding.Inthisprocedure,oneattemptstodisplacethelesiontowardtheinstrumentusingtransducerpressureonthebladder.Ifurethralaccessisimpossible,thenutilizepercutaneousfine‐needleorcorebiopsyifitisimportanttoobtainahistopathologicdiagnosis.
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UltrasonographyoftheReproductiveTract
FemaleReproductiveTract
Indications:pregnancydiagnosis,fetalviability,pyometra,ovarianoruterinetumor,infertilityTransducer:7.5MHzisidealforevaluationofnormalovariesanduterus;5.0MHzisadequateformostdiseasestatesScanplane:multiplescanningplanesandpositionsmaybeneededtovisualizetheentirereproductivetract ownersofshowanimalsmayobjecttoclippingthehaircoat;applicationofalcohol
priortoapplyingacousticgelmayimproveimagequality anegativesonogramunderthisless‐than‐idealconditioninearlypregnancyshouldbe
repeatedseveralweekslatertoconfirmafalse‐negativediagnosis scanthecaudalpoleofthekidneyandtheadjacentareaintransverseandsagittal
planestolocatetheovary adistendedurinarybladderisanacousticwindowforimagingtheuterus theuterinebodyisclosetomidline;theuterinehornsaredifficulttoidentifyinthe
normalpatient
NormalUterus composedofthreelayers:mucosa,muscularis,serosa dorsaltourinarybladder,ventraltodescendingcolon anormal,small,nongraviduterinebodyandcervixcansometimesbeimaged identifiedasasolid,homogenous,relativelyhypoechoicstructure;layersareusually
notdifferentiated;lumenusuallynotseen difficulttoidentifythehornsNormalOvary theovariesaresmallandovaltobeanshaped theovariesmeasureapproximately1.5cminlength,0.7cminwidth,and0.5cmin
thickness(25lbdog);catovariesaresomewhatsmaller theovaryhasacortexandamedulla;thecortexcontainsthefollicles sonographicappearancevariesduringtheestrouscycle anestrus/earlyproestrus:homogeneous,echogenicitysimilartorenalcortex proestrus:follicularcystsidentifiedatday2‐7;initiallyseemultiple,diffuse,
smallanechoiccyststhatenlargewithtimeuntilovulation;mayreach1cm
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ovulation:detectedsonographicallywhenthereisadecreaseinthenumberandsizeoffolliclesfromonedaytothenext;requiresdailyserialscanning
metestrus:multifocal,anechoic‐to‐hypoechoicareas,aswellashyperechoicareasarepresent;thesemayrepresentcorporahemorrhagicaorcorporalutea
Pregnancy
ultrasoundhasbeenusedtodetectpregnancyinthebitchasearlyas10dayspostbreedingandinthequeenasearlyas11dayspostbreeding
accuratedeterminationoffetalnumberisunreliable;mostaccuratebetweenday28to35
atday10‐20agestationalsacconfirmspregnancy;seenasananechoicroundstructurewithvariablyechoicwalls;surroundinguterinetissueisfocallythickened
atday23‐25theembryoisfirstseenasanoblongechogenicstructureeccentricallylocatedwithintheenlarginggestationalsac
atday28cardiacactivityisreadilyseen;approximatelytwotimesthematernalheartrate
fetalorientationiseasilyrecognizedbyday28 limbbudsnotedaboutday35 fetalskeletonisidentifiedbyday33‐39;seenashyperechoicstructureswith
acousticshadowing urinarybladderseenbyday35‐39 kidneysandeyesareseenbyday39‐47 thereareformulastoestimategestationalage slowingoffetalheartratetolessthantwicethebitch’sheartrateanddecreased
fetalmovementindicatefetalstress
UterinePathology
Pyometra: sonographicfindingsincludeanenlargeduterusanduterinehorns;enlargementis
usuallysymmetric,butmaybefocalorsegmental luminalcontentsareusuallyhomogenousandechogenic,butmaybeanechoic
withstrongdistalenhancement theuterinewallisvariableinappearance,fromverysmoothandthintothickand
irregular
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Ddx:hydrometraandmucometra;theseconditionsmaybesuspectediftheluminalcontentsareanechoicandtheuterinewallisthin;alsoifclinicalsignsarelacking
Stumppyometra:
classicallyalarge,complexmasslesionisidentifiedintheregionoftheuterineremnant
needtoevaluateforovarianremnantNeoplasia:
rareinbothdogandcat sonographicappearancewillbeamasslesionprojectingintotheuterinelumen iflargeandnecrotic,maybecomplexininternalarchitecture
OvarianPathology
Cysticovariandisease: sonographicappearanceisthatoftruecysticlesions,characterizedbyanechoic
contents,athinwall,anddistantacousticenhancement generallyquitelarge,>2.5cm maybesolitaryormultiple associatedchangesincludepyometra,cysticendometrialhyperplasia,or
hydrometraNeoplasia:
uncommonindogsandcats maybeunilateralorbilateral recognizedultrasonographicallyasamasslesioninthelocationoftheovary variablysized;iflarge,theyareusuallycomplexinarchitecturewithmixed
echogenicity oftenisadiagnosisofexclusionbyrulingoutsplenic,renalorlymphnodemasses
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MaleReproductiveTract
Indications:clinicalsignsofurogenitaldisease,constipation,prostatomegaly,infertilityTransducer:usehighfrequencytransducerwheneverpossible,7.5MHz;imagingwithinthefocalzoneisimportantforoptimalresolutionScanplane:scanintransverse,longitudinal,anddorsalplanes;mayneedastand‐offpadforthetesticles
NormalProstate surroundsthepelvicurethra,beginningatthelevelofthetrigone;theurethramaybe
eccentricallylocateddorsallyinthegland,ormaycoursethroughthecenter seenasabilobedstructure sonographicallyhasahomogeneousparenchymalpattern echogenicityisvariable,moderateechogenicityismostcommon(similartothespleen) thenormalprostateshouldbesymmetricalandwellmarginatedbythethinechogenic
capsule
ProstaticPathologyBenignhyperplasia:
sonographicallyappearsasanenlargedprostategland enlargementmaybesymmetricorasymmetric,smoothornodular,maydistort
themargin echogenicityvaries;maybehypoechoictohyperechoic scatteredhyperechoicfocimaybepresent(fibrosis) intraparenchymalcystscanbepresent,varyinginsizeandnumber ingeneral,changesarelessseverethanwithinfectionorneoplasia ifheterochoic,Ddx:infectionorneoplasia hyperplasiashouldnotdisruptthecapsule,norshouldtherebelymphadenopathy commontohavemultipleprocesses,needFNA
Prostatitis: maybeacuteorchronic sonographicappearancemaybesimilartothatofbenignhyperplasia mayseesymmetricorasymmetricenlargement overallappearanceisusuallyaheterogeneous,mixedpatternofvarying
echogenicity cystsorcystlikestructuresmaybepresent,includingabscessformation capsuleisusuallyintact uncommontodetectmorethanmildlymphadenopathy
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Neoplasia: manifestsinavarietyofsonographicappearances typically,theglandwillbeenlarged,irregularinshape,haveaheterogeneous
echotexture mineralizationmaybepresent cavitary,cystlikelesionsmaybepresent differentiationfrominfectionmaybedifficult;bothmaybepresent stronglysuggestiveofneoplasiaisextensionofchangestourethraortrigone,
disruptionofthecapsulewithextensiontosurroundingtissues,lymphadenopathy biopsy
Paraprostaticcysts:
fairlycommon maybeattachedtotheprostatebyastalk sonographicallyareanechoic,fluid‐filledstructures wallthicknesscanvary contentsofcystmaycontainfocalechogenicities maybeseptated differentiatefromurinarybladderbycarefulexamination
NormalTesticles testicleappearshomogeneouswithacoarsemediumechopattern thetunicformsathinhyperechoicperipheralecho themediastinum(rete)testisisseenasaveryechogeniccentrallinearstructureonthe
midsagittalplane theepididymisislessechoicandmaybenearlyanechoic thetailisthemostconsistentlyimagedportion maximumwidthofepididymisis1/4thatoftesteswidth
TesticularPathologyNeoplasia:
threecommontypes:interstitialcell,Sertolicell,andseminoma sonographicappearanceoftesticulartumorsisvariable;notspecificfortumor
type interstitialcelltumorsmaybefocalhypoechoiclesionslessthan3cmdia largelesionsgenerallyhaveamixedorcomplexpattern;thismaybesecondaryto
hemorrhageandnecrosis focalandmultifocallesionsoccur Sertolicelltumorsmostcommonincryptorchid
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Orchitis/epididymitis: sonographicallyappearsasdiffuse,patchy,hypoechoicpattern usuallyseetesticularandepididymalenlargement(concurrentepididymitis) abscessescanoccur mayseeextratesticularfluid increasedthicknessandhyperechogenicityoftunics
Torsion:
sonographicallyseetesticularenlargement,characterizedbydiffuselydecreasedparenchymalechogenicity
seeconcurrentenlargementoftheepididymisandspermaticcord willhavelossoftheDopplersignal(lackofbloodflow)
Retainedtestes:
identifyanabdominaloringuinalmassasatesticle lookforretetestis(mediastinaltestis) generallysmall,maybeatrophied evaluateforneoplasia
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UltrasonographyoftheGITract
Ultrasonographically,thestomachwallis3‐5mmthickinthedog.Inthecat,themeanthicknessoftheinter‐rugalregionis2mmandthemeanthicknessoftherugaeis4.4mm.Ithasbeenshownthatsmallintestinalwallthicknessvarieswithweightinthedog,andtheduodenalwallisalwaysthicker(mainlyduetothemucosallayer)thanthejejunum.Theduodenalwallthicknessindogsis≤5.1mmindogs<20kg,≤5.3mmindogs20‐30kg,and≤6.0mmindogs>30kg(95%confidenceinterval).Thejejunalwallthicknessindogsis≤4.1mmindogs<20kg,≤4.4mmindogs20‐40kg,and≤4.7mmindogs>40kg(95%confidenceinterval).Incatstheduodenalwallthicknessrangesfrom1.5‐3.5mm(average2.4mm)andthejejunalwallthicknessrangesfrom1.5‐3.5mm(average2.1).Inbothspeciesthecolonwallisgenerallythinnerthantheadjacentsmallintestine,especiallywhenthecolonisdistended.Incatsspecifically,themeancolonicwallthicknessis1.7mm(range1.1‐2.5mm).Thickerwallsshouldbeviewedwithsuspicionduringultrasoundexaminations.Theappearanceofultrasonographicallyisnotetiologicallyspecific.Guidedaspiration,endoscopy(ifpossible),orfullthicknessbiopsy(atlaparotomy)willbenecessaryforfurtherdefinition.Lesionsareclassifiedbyultrasoundasintramural,extramural,annularorintraluminaljustastheyareforradiography.
Lesionidentificationinthealimentarytractbyultrasoundcanbe“hitormiss”astheentireintestinaltractcannotconsistentlybeevaluatedduetomanyfactors,includingnormalorabnormalgasinthealimentarytractandoperatorskill.Additionally,oftenalesioncannotbepreciselylocalizedtoaspecificbowelloop.However,asonographicstudyhastheadvantagesofneedingnospecialpreparation(otherthanarecommended12hourfast),isnon‐invasive,allowsevaluationoftheentiregastrointestinalwallratherthanjustthemucosa,yieldsmoreconsistentwallthicknessmeasurements,givesreal‐timeassessmentofmotilitywithoutionizingradiation,providesassessmentofregionaldisorders(metastasis,peritonitis),andcanguidesamplingofdiseasedtissues.Becarefulofusingultrasonographictechniquesto“screen”thealimentarytractforintramuralorintraluminallesionsbecausetherearenumerousfalsenegativesduetogasinterference.However,massescanbelocalizedtoalimentarytractstructures(particularlystomach,smallintestineandcolon)bythepresenceofabright(echogenic)stripe.
Normalstomachandbowelhave5layersidentifiableonhigh‐frequencyultrasonography,butonly3maybeseenwithsomeequipment.Themucosalsurface‐luminalinterfaceisseenasathinhyperechoicline.Themucosaitselfisarelativelythickhypoechoiclayer.Theadjacentsubmucosaisathinhyperechoicline.Intheileum,thesubmucosaismoreprominentandcanallowspecificlocalizationoftheileum,particularlyinthecat.Thenextlayer,themuscularispropriaisathinhypoechoicline.Theoutersubserosa‐serosaisathinhyperechoicinterface.Allfivelayersaregenerallydistinguishableinthestomach,butinthesmallintestinethemuscularispropriaandsubserosa‐serosamaynotbeidentifiable.Themostnotablelayersaretheechogenicsubmucosaandtheechogeniccomplexofthemucosaandluminalairinterface.Thesesamebrightstripescanbeseenwithinalimentarytract‐associatedmassesimagedbyultrasonography.Theseechogenic“stripes”maybedistorted,thickened,orirregularly
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interruptedbyinfiltrativediseasedependingontheorigin.Fortunately,thereisalmostalwaysnormalgutintheregionforcomparison.Itisimportanttorememberthatnotdistinguishingallofthelayersdoesnotnecessarilyindicatepathology,asgasartifactandlimitedresolutioncanleadtoafalselossofthenormallayering.Inadditiontothelayers,differentintestinalpatternscanbeseenwithultrasound.Themucouspatternisseenwithacollapsedbowelthathasanechogeniclumenwithoutshadowing.Afluidpatterniswhenthebowellumencontainsanechoicluminalcontents,thusoptimizingvisualizationofthebowelwall.Agaspatternshowsintraluminalhighlyechogenicreflectivesurfacewithshadowingthatpreventsdeepstructureevaluation.Thealimentarypatternisgutcontainingfoodparticles.Excessfluidwithfloatingluminalmaterialissuspiciousforatleastpartialobstructionatultrasonography.
SPECIFICORGANCONSIDERATIONS–ULTRASONOGRAPHYEsophagus:1) Theesophagusisonlyrarelyidentifiedsonographicallyatthelevelofthecardia.Stomach:1) Appearancevarieswithcontentanddegreeofdistention.2) Stomachgascausesreverberationand/orcomettailartifactandinterfereswith
imagingofthedeepportion.3) Thestomachcanbeemptiedofgasanddistendedwithfluidforimproved
evaluation,especiallyofthemucosallayer.4) Themeannumberofgastriccontractionsis4‐5perminute.Thisisinfluencedby
manyfactors.Foranaccurateestimateofgastriccontractions,thestomachshouldbeobservedfor3minutes.
5) Allfivelayersofthestomachwallaregenerallydistinguishable.Bewareofartifactualthickeningofthestomachwallduetorugalfolds,imagingplane,anddegreeofdistension.Rugalfoldsareseenwhenthestomachisemptyandtendtodisappearwhenthestomachisdistended.
6) Athickwallisthemostcommonabnormalityidentified.Itcanbedifficulttorecognizediffusethickening.
7) Tumorsandgranulomasgenerallyproducefocal,asymmetricalthickeningwithdisruptionofnormalwalllayering.Otherinflammatoryorinfiltrativediseasesgenerallyproducediffusethickeningandgenerallymaintainwalllayering.
8) Lymphomagenerallyproducesamorefocalmassthanadenocarcinoma.Lymphomaalsooftenproducestransmuralcircumferentialthickening,ishypoechoicandhasregionallossofmotility.Carcinomamayappearasapseudolayeredlesionofamoderatelyechogeniczonesurroundedbyouterandinnerpoorlyechogeniclines.Leiomyosarcomatendstobeexophytic,largeandcomplex.
9) Bewareofthegastriccontentpseudomass.Amuralmasswillbeseenasadiscreteroundedorlobulatedlesionthatisfixedinpositiondespiteperistalsisorchangesinpatientposition.
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10) Hypertrophicpyloricgastropathyproducesuniform,circumferentialthickeningofthehypoechoicmuscularlayer–generallythenormalwalllayeringispreserved.Thestomachisfluiddistendedandreducedpassageofgastriccontentsisseen.
11) Uremicgastritispresentsasathickwallandthickrugaewithdecreaseddefinitionofthewalllayers.Thefundusandbodyaremostoftenaffected.Themucosamaybemineralized–appearingasathinveryechogeniclineatmucosal‐luminalinterface.
12) Agastricforeignbodyisasharplydefined,hyperechoicinterfacewithdistalshadowingandgenerallymovesinposition.
Smallintestine:1) Completeassessmentofthesmallintestineincludesassessmentofthesize,shape
andwallthickness.Thetransverseaxisisoftenpreferableformeasuringasthereislesschanceoferror.Measurementsaremoreaccuratewhenwalllayerscanbeseensothatcaliperscanbepreciselyplaced.Wallthicknessandluminaldiameterdovarywithperistalsis.Rememberthatnotseeingthewalllayersdoesnotnecessarilyindicatepathology.
2) Intestinalcontractionsaregenerally1‐3perminute.3) Usinganacousticwindowsuchasthespleencanenhanceimagingoftheintestine.4) Pyerspatchesintheduodenummaybevisibleasoutpouchesfromthelumen.Do
notmistaketheseasulcers–thewallwillbenormalinthicknessandlayering.5) Obstructiveileushassegmentaldilationwithincreasedperistalsisacutely.With
chronicobstruction,decreasedperistalsiswillbepresent.Causesidentifiedwithsonographymayincludeforeignbodies,regionalinflammationandadhesions,intussusceptionorneoplasia.
6) Non‐obstructiveileushasmildtomoderategeneralizeddilationwithdecreasedmotility.
7) Mostforeignbodieswillbeasharplydefinedhyperechoicinterfacewithdistalshadowing.Thesecanbemaskedbyairbutmanipulationofbowelwiththetransducerandchangesinpatientpositionshouldaidinevaluationofthatportionofbowel.Proximalfluidorgasdistentionandhyperperistalsisgenerallyaccompanies–thereforethesefindingsshouldmandatecarefulsearchfortheobstructinglesion.Linearforeignbodieshaveaclassic“ribboncandy”appearancecausedbytheplicationofthesmallintestine.Donotconfuseaspasticloopofbowelwithplication.
8) Intussusceptionsappearsonographicallyasamultilayeredlesionwithlinearstreaksofhyperechoicandhypoechoictissueinlongsectionandconcentricrings(“ring”sign)incross‐section.Theoutersegmentisoftenthickenedandedematous.
9) Wallthickeningismosteasilydetectedwhenasymmetric.10) Inflammatorydiseasesingeneralhaveextensive,symmetricalmildtomoderate
wallthickeningwithmaintenanceofwalllayering.Regionalaffectedlymphnodeswillonlybemildlyenlargedandgenerallyofnormalechogenicity.
11) Anulcermayappearasalocalizedthickening.Perforationmaybeidentifiedbyfocalgasdissectioninthethickenedwallwithechogenicregionalfat,fluidaccumulation,orfreegas.
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12) IBDmaypresentasmildlythickenedbowel(oneormoresegments)thatishypomotileandrigid.Generallythemucosaandsubmucosaarethethickenedlayersandmayhavealteredechogenicity.Walllayeringmaybeindistinct.
13) Neoplasiaingeneralpresentsasfocal,asymmetric,moderatetoseverewallthickeningwithlossofwalllayering.Regionalmoderatelymphadenopathywithalteredechogenicityiscommon.
14) Lymphomamostcommonlypresentsastransmural,circumferential,homogenous,hypoechoicthickeningwithlossofnormalwalllayering.Lymphomatendstoinvolvealongbowelsegmentormultiplebowelsegments.Regionalmoderate,hypoechoiclymphadenopathyisgenerallypresent.Lymphomaislesslikelytocauseobstructionofthelumen.
15) Carcinomaislocalized,irregular,oftenmixedechogenicitythickeningofbowelwallwithlossoflayering.Oftenashortersegmentofbowelisaffectedthanwithlymphomaandhasassociatedobstruction.Carcinomacanpresentasanannularconstrictivelesion.Generallyonlyonesegmentofbowelinvolvedincomparisontolymphoma.
16) Smoothmuscletumorsofenappearaseccentric,poorlyechogenicmassesthatareexophyticandrarelycauseobstruction.Massesgreaterthan3cmareoftencavitary.
Colon:1) Thewalllayersofthecolonarenoteasilyidentified.2) Diffusethickeningmaybeobservedininflammatoryandinfiltrativeprocessessuch
asinfectiousorlymphocyticplasmacyticcolitis.Thisfindingisnon‐specific.3) Focalwallthickenings,disruptionofwalllayeringandheteroechoicmassesmaybe
neoplasiaorgranulomas.
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UltrasonographyoftheAdrenalGlands
Ultrasoundhasquicklybecomeanimportantmodalityfortheevaluationofadrenalglandsinthesmallanimalpatient.Theadvantagesofadrenalsonographyincludetheabilitytoimagebothnormalandabnormalglands,theeaseandrapidityoftheprocedure,thelackoftheneedforanesthesia,andtheavailabilityofultrasoundtopractitioners.However,thechallengeofimagingtheadrenalglandsshouldnotbeunderestimated.Evenforanexperiencedsonographer,thesmallsizeoftheglands,thedeepandsometimesvariablepositionoftheglands,theinterpositionofbowelgas,theobesenatureofmanypatients,andthelackofpatientcompliancecanleadtoafrustratingandsometimesunrewardingexamination.Indications:hyperadrenocorticism,cranialretroperitonealmassTransducer:thehighestfrequencytransduceravailableshouldbeusedinordertoassesstheadrenalglands–atleasta7.5MHztransducershouldberoutinelyused;occasionallyalowerfrequencytransducermaybenecessaryinalargerpatientScanplane:positionanimalindorsalrecumbency,obtainsagittalandtransverseimages,attimesyoumayneedtoimagethepatientinlateralrecumbencyforthenondependentadrenalglandArtifacts:bowelgaswillinvariablyleadtoimagingartifactsoftheadrenalglands;considerabletransducerpressureshouldbeusedtodisplaceoverlyingintestineIngeneral,bothadrenalglandscanbeimagedinallpatients,buttheexaminationcanbedifficultandtimeconsumingforthenormaladrenalgland.Therightadrenalglandtendstobemoredifficulttoimagethantheleftadrenalgland.Ifnecessary,thepatientmayneedtobesedatedforoptimalimaging.
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NormalSonographicAppearance
Location:Theadrenalglandsareretroperitonealstructures. Leftadrenal:craniomedialtoleftkidney,ventrolateraltoaortabetweenoriginof
cranialmesentericandleftrenalarteries Rightadrenal:craniomedialtohilusofrightkidney,dorsalordorsolateraltocaudal
venacava,cranialtorightrenalarteryandcranialmesentericartery Thephrenicoabdominalarteryisdorsaltoeachadrenalgland,andthe
phrenicoabdominalveinisventraltoeachadrenalgland. Inthecat,theadrenalglandsseemtobelocatedmorecranialwithrespecttokidney.
Theadrenalglandsaresmall,elongated,hypoechoicstructures.Theglandsaresurroundedbyhyperechoicfat.Withoptimalimagingandhigh‐frequencytransducers,onecanappreciatethelessechogenicoutercortexandthemoreechogenicinnermedullaasstriationoftheadrenalgland.Itisimportanttodistinguishtheadrenalglandsfromhypoechoicvessels.Theadrenalglandswillhaveadefinitebeginningandend,whereasthevesselswillbeabletobefollowedfromagreatvessel(aortaorcava)toaparenchymalorgan.
Theleftadrenalglandiscentrallyconstrictedwithenlargedextremities,havinga“dumbbell”or“peanut”shape.Inordertoimagetheleftadrenalglandinatruelongitudinalplane,thetransducershouldberotatedapproximately10‐15°clockwise.Therightadrenalglandis“comma”,“wedge”,or“boomerang”shaped.Oftentheentireglandcannotbeimagedinoneplane.Theextremitiesoftheadrenalglands(cranialandcaudalpoles)areoftenasymmetric.
Severalstudieshaveassessedthenormalsizeoftheadrenalgland,yieldingalargerangefornormallengthanddiameter.Therangeofnormallengthhasbeendocumentedfrom10.7‐50.0mm,themaximumtransversediameterupto16.0mm,andtheminimumtransversediameterdownto3.0mm.Inpractice,thetransversemaximumdiameterisgenerallythemostsensitiveandspecificforadrenalglandenlargement.Anupperlimitof7.4mmhasbeenproposedasacut‐offforthenormaladrenalgland.Arecentstudyhassuggestedthatindogs<10kg,acut‐offof6.0mmshouldbeusedasthecriterionfordifferentiatinganormaladrenalglandfromadrenalhyperplasia.Itisimportanttorememberthatthereisapopulationofnormaldogswhichwillhavegreatermeasurements.Theleftadrenalglandisgenerallylargerinbothlengthandtransversediameterthantherightadrenalgland.
Inthecat,theadrenalglandsaresmallhypoechoicstructuresofovalorcylindricalshape.Occasionally,theshapewillbesimilartodogs.Thestriationofcortexandmedullaismoredifficulttodistinguish.Again,itisimportanttodistinguishtheadrenalglandsfromregionalvessels,aswellasfromlymphnodes.Onestudyof10catsdeterminedthatthelengthoftheadrenalglandsis10.7±0.4mm,themaximumtransversediameteris4.3±0.3mm,andtheminimumtransversediameteris3.9±0.2mm.Anotherstudyof20catsshowedarangeoflengthfrom4.5‐13.7mmandarangeofwidthfrom2.9‐5.3mm.
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AdrenalGlandPathologyinDogsPituitary‐dependenthyperadrenocorticism:
Classically,theadrenalglandsarebilaterally,uniformly,symmetricallyenlarged» Usingamaximumtransversediameterof7.4mmyieldsasensitivityof77%
andaspecificityof80%and91%forhyperadrenocorticism;using6.0mmindogs<10kgyieldsasensitivityof75%andaspecificityof94%
» Mayseemildbilateralorunilateraladrenomegaly(ifunilateral,mustdifferentiatefromprimaryormetastatictumor)
» Adrenalsizemaybenormal–rememberthatthereisagreatoverlapbetweenthesizeofnormalandabnormaladrenalglands
Shapeisgenerallynormal,mayseenodularhyperplasia(smallmasslesionorshapechangeinoneorbothglands)» Severehyperplasiacanresultinbilaterallymasses
Echogenicityisgenerallyuniformandoftenhypoechoictothenormalexpectedadrenalgland» mayseehyperechoic,hyperplasticnodules
Evaluateforsteroidhepatopathy(generallyuniformincreaseinechogenicityofliver)
Interpretultrasoundfindingsinconjunctionwithclinicalfindingsandresultsofhematological,serumbiochemicalandendocrinetests
Adrenal‐dependenthyperadrenocorticism:
Generallyseeaunilateral,well‐definedshapeormasschange» Massisgenerallyroundorovalastheabnormaltissuegrowsinroughlya
concentricfashion» Smallmassesmayinvolveonlyaportionofthegland,whereaslargemasses
oftencausesphericalenlargement Variableechogenicity–solidtocomplex DDx:adenomavs.adenocarcinoma(thelattertendtobelarger) Mayseehyperechoic,shadowingfoci(mineralization);morecommonwith
adenocarcinoma(adrenalmineralizationisanormalfindinginupto30%ofthepopulation)
Thecontra‐lateralglandmaybenormalsizeorsmall(atrophied) Evaluateforlocalextensiontokidneyornearbyvessels,aswellasformetastasis
–malignanttumors Adrenocorticaltumorsarereportedmorefrequentlyinfemalesandlarger
breedsPheochromocytoma:
Tumorsofchromaffincellsofmedulla;produceepinephrine 50%foundincidentally;clinicalsignsareoftenvagueandnonspecific,patient
mayhaveconcurrentdisease Generallyseeaunilateral,well‐definedshapeormasschangeofvariable
echogenicity(difficulttodistinguishfromadrenocorticaltumor)
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» Massisgenerallyroundorovalastheabnormaltissuegrowsinroughlyaconcentricfashion
» Smallmassesmayinvolveonlyaportionofthegland,whereaslargemassesoftencausesphericalenlargement
Lesslikelytomineralizethanadrenocorticaladenocarcinoma;frequentlyinvaderegionalvesselsandmetastasize
Incidentaladrenalnodules/masses: DDx:pheochromocytoma,non‐functionalorsubclinicallyfunctioning
adrenocorticaltumor,metastaticneoplasia,hyperplasticnodule Variableappearance Benignprocessesshouldnotbeinvasive;regionalorvascularinvasionishighly
indicativeofmalignanttumor Approachwilldependuponclinicalpresentation,otherfindings,andowner
» Surgicallyremove,surgicalorultrasound‐guidedbiopsy,waitandre‐evaluate
Adrenalmassesingeneral:
Inpresenceofadrenaltumor,observationofnormalcontra‐lateralglandmayindicateapheochromocytoma,nonfunctionaladrenocorticaltumor,metastaticneoplasia,orpotentiallyafunctionaladrenocorticaltumor
Acombinationofalloftheabovemayoccurandcanbeconfusing Inonestudy,masses>4cmweremalignant;masses2‐4cmtendedtobe
malignant,masses<2cmwereaslikelytobebenignormalignant Anodule(<1cm)wasnon‐specific
Smalladrenalglands:
Onestudyshowedthatdogswithhypoadrenocorticismhadadrenalglandssmallerthannormal,healthydogs
Norealestablishedlowernormallimit DDx:exogenouslyadministeredsteroids,hypoadrenocorticism
DiseasesoftheAdrenalGlandsinCats
Diseasesoftheadrenalglandsarefairlyrareincats.Pituitary‐dependentandadrenal‐dependenthyperadrenocorticismhasbeendocumentedincats.Metastaticdiseasetotheadrenalglandscanalsooccur.
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Ultrasound‐guidedFine‐needleandCoreBiopsyoftheAdrenalGlandTheseproceduresareroutinelyperformedinpeoplewithquitelowcomplicationrates.Theseproceduresareperformedindogsandcats,butthereisnotmuchinformationintheliteratureregardingcomplications.Itshouldbenotedthatthereisthepossibilityofahypertensivecrisisorfatalhemorrhageaftersamplingofapheochromocytoma.Itshouldalsobenotedthatsmallsamplesoftheadrenalglandsmaynotyieldenoughtissueforaccuratecytologicalorhistopathologicdeterminationofunderlyingprocesses.
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