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CVM6105SmallAnimalUltrasoundSupplementalNotes,Spring2015KariL.Anderson,DVM,DACVRProfessor,MedicalImagingOffice:C350Phone:612‐625‐3762Email:kla@umn.eduLecturetopic 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

16  

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

21  

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

22  

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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