BENIGNFOCALLIVERLESIONSAbscessesandHaematomaClinicalfeaturesofanabscess(膿腫)Patientspresentwithfever,oftenaccompaniedbyrightupperquadrant(RUQ)painandvomiting（嘔吐）.Abnormalliverfunctiontests(LFTs)andanaemia（貧血）canalsobepresent.Theclinicalhistoryhelpsthesonographer（超聲醫(yī)生）toestablishthenatureofthefocallesionandaetiologyoftheabscess.Abscessesofanytypemaybesolitaryormultiple.Becausetheultrasoundappearancesofabscessescanbesimilartothoseofnecrotic（壞死的）tumoursorhaematoma（血腫）,theclinicalpictureisofparticularimportancetothesonographer.UltrasoundappearancesHepaticabscessesmaydisplayavarietyofacousticfeatures.Theirinternalappearancesvaryconsiderably.Intheveryearlystagesthereisazoneofinfected,oedematous（水腫的）livertissuewhichappearsonultrasoundasahypoechoic,solidfocallesion.Astheinfectiondevelops,thelivertissuebecomesnecrotic（壞死的）andliquefactiontakesplace.Theabscessmaystillappearfullofhomogeneousechoesfrompusandcanbemistakenforasolidlesion,butasitprogresses,thefluidcontentmaybecomeapparent,usuallywithconsiderabledebris（碎片）withinit.Becausetheyarefluid-filled,abscessesdemonstrateposteriorenhancement(Fig.4.7A).Themarginsofanabscessareirregularandoftenill-definedandfrequentlythickened.Theinflammatorycapsuleoftheabscessmaydemonstratevascularity（多血管）oncolourorpowerDopplerbutthisisnotinvariableanddependsonequipmentsensitivityandsizeofthelesion.Infectionwithgas-formingorganismsmayaccountforthepresenceofgaswithinsomeliverabscesses(Fig.4.7B).Thegascontainedwithinthislargeabscessintherightlobeoftheliverobscuresthefullextentofthelesion.(Largeabscesseslikethis,whichcontaingas,maymimictheacousticappearancesofnormalbowel.)TherearethreemaintypesofabscessPyogenicabscess（化膿性膿腫）Amoebicabscess（阿米巴膿腫）Candidiasisabscess（念珠菌膿腫）PyogenicabscessTheseformasaresultofinfectionenteringtheliverthroughtheportalvenoussystem(門靜脈系統(tǒng)).Mostcommonly,appendiceal（闌尾的）ordiverticular（憩室的）abscessesareresponsible,butintrahepaticabscessesarealsoseeninimmunosuppressed（免疫抑制的）patientsandfollowingpostoperativeinfection.Theyarefrequentlymultiple,andthepatientmustbecloselymonitoredafterdiagnosistopreventrapidspread.Pyogenicabscessisstillconsideredalethal（致命的）condition,whichhasincreasedinrecentyearsduetoincreasinglyaggressivesurgicalapproachestomanyabdominalneoplasms.4AmoebicabscessThisisaparasitic（寄生蟲的）infectionwhichisrareintheUK,butfoundfrequentlyinpartsofAfrica,IndiaandthesouthernpartsoftheUSA.Suspicionshouldberaisedwhenthepatienthasvisitedthesecountries.Itisusuallycontractedbydrinkingcontaminatedwater（污水）andinfectsthecolon（結(jié)腸）,ulceratingthewallandsubsequentlybeingtransportedtotheliverviatheportalvenoussystem.ManagementofhepaticabscessesAnultrasound-guidedaspiration（吸引術(shù)）toobtainpusforcultureisusefulforidentifyingtheresponsibleorganism.Aspirationcombinedwithantibiotictherapyisusuallyhighlysuccessfulforsmallerabscessesandultrasoundisusedtomonitortheresolutionoftheabscessesintheliver.Ultrasound-guideddrainageisusedforlargelesions,andsurgicalremovalisrarelyrequired.Furtherradiologymaybeindicatedtoestablishtheunderlyingcauseandextent,forexamplebariumenema（鋇劑灌腸）orCT,particularlyifamoebicinfectionissuspected.HaematomaTheliverhaematomamayhavesimilaracousticappearancestothoseofanabscess,butdoesnotsharethesameclinicalfeatures.Ahaematomaistheresultoftrauma（創(chuàng)傷）(usually,therefore,viatheAccidentandEmergencydepartment)butthetraumamayalsobeiatrogenic（醫(yī)源性）,forexamplefollowingabiopsy（活檢）procedure(hencethevalueofusingultrasoundguidancetoavoidmajorvesselsintheliver)orsurgery.Intrahepatichaematomafollowingaroadtrafficaccidentwithribfractures.Thelesionisrelativelyfreshandcontainssomelow-levelechoes.2-day-oldsubcapsularhaematoma.Thecollectionbecameprogressivelysmallerandhyper