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Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4087_Библиотеки_им_академика_М_И_Перельмана

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Adiagramtoshowthesurfaceanddeepveinsoftheleg.Therearetwomain
surfaceveins,bothconnectingwiththedeepveinsthroughthemusclesheath.
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Acrosssectionofaveinunderthemicroscope.
whichareemptiedbythesqueezingeffectofsurroundingmuscleswhenthesecontract,andbytheforceofgravitywhenyoukeepyourlegraised.
Thevalvesinthelegveins,whosefunction,aswehaveseen,istohelpthebloodflowbacktowardstheheart,consistofadoublefoldofthesmoothinnermostlayer
oftheveinwiththeadditionofacertainamountofsmoothmuscleandconnectivetissuefromthemiddleandouterlayers.Itisafailureofthesevalvesthatisthebasic
causeofvaricoseveinsinourlegs.Ifthedefectivevalveisinoneoftheveinsalongthesurfaceanddeepveinsystems,thepartofthesurfaceveinnormallyprotected
bythisvalveissuddenlymadetocopewithahighpressurebackflowofbloodfromthemusclepumpoftheleg.Thevein'swallsexpandtocopewiththeinfluxof
extrablood.Inturn,thispieceofdilatedveinputspressureonneighbouringvalvesbecause,astheveinswells,thevalveedgescannolongerreacheachotherinthe
closedposition,so,gradually,ofteninatimescalemeasuredinyears,valveaftervalvebecomesunabletooperateandexpansion,ordilation,ofthesurfacevein
systembecomeswidespread.Ifthefirstvalvetobreak
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Ifavalvebetweenthesurfaceanddeeplegveinsfails,tehbackflowofblood
swellsthesurfacevein,whichbecomesvaricose.
downisatthebackofyourknee,wheretheshortsaphenousveinends,thentheveinsatthebackofthecalfareaffected.Ifitisthevalveinyourgroin,attheendof
thelongsaphenousvein,thendilationsmayoccurdowntheinnersideofyourthighandtheinnersideofthecalf.Therecouldbeotherdilationsbecauseofthefailure
ofanyoftheotherlinkingveinsscatteredthroughouttheleg.
Itseemsincrediblethatsomuchworry,embarrassment,painandmiserycananddoesdependontheproperworkingofthesetinyflapsoftissuewithintheveinsof
ourlegs.InChapter3weshallbelookingatthelikelyreasonswhytheygowrong.
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Chapter3—
WhatCausesVaricoseVeins?
Herewedescribetheprimarydefectofvaricoseveins—
theineffectivevalveswithinthevein.Thedefectmaybesomethingyouarebornwithormayfollowinjuryor
anepisodeofclottinginthevein.Aggravatingfactorsincludestandingforlongperiodsandpregnancy.
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Nowwhyshouldavalvebecomeineffective?Thereare,webelieve,anumberofcauses,althoughwemustsayherethatdoctorsarehamperedbyalackofreal
researchintotheearlystagesofvaricoseveins.Afterall,wecannotreproducevaricoseveinsexperimentallyinanimalstostudythisconditioninthelaboratory,andno
oneisparticularlyanxiousforustoremovehisorherearlyvaricoseveinsandputthemunderamicroscopesothatwecaninvestigatetheearliestchangesthattake
placeinthisprocess.
FailureofValvesintheYoung
First,althoughwedonotknowforsure,webelievethatthevaricoseveinsinyoungadultsmaybeduetoaveryearlydefectofoneormoreofthevalves.Perhapsthe
valvesactuallyfailtodevelop,andthereissomeevidencethatpeoplewithvaricoseveinshavefewervalvesalongthecourseofthemajorsurfaceveinsthanisthought
normal.Thereissomeevidencethatthevalvemaybecomeincompetentduetodilatationoftheveinwallsupportingthevalve.Muchofthestrengthoftheveinwallis
derivedfromastructuralproteincalledcollagen,andaweakeningofthecollagenallowsthediameteroftheveintoincrease,whichinturncausesthevalvecuspsto
separateandsoallowsbloodtoreturnthroughthevalve.Thisproblemmaybeinheritedandexplainswhytheincidencesofvaricoseveinsruninfamilies.
Theprotectivevalvesmayhavedevelopednormally,butthentheyhavebecomedamagedbysomeprocess.Thiscouldbedue,forexample,toathrombosis,or
clotting,whicheventuallydisappearsbutleavesbehindadamagedvalve.Oritmayfollowaninjurytotheleg,perhapsminorandcompletelyforgottenabout,but
enoughtoproducethedefect.
ThrombosisandVaricoseVeins
Sometimesvaricoseveinsappearafteraseverethrombosisinvolvingthedeepveinsthatdrainthemusclesofthecalforthethigh.Thethrombosismayoccuraftera
majoroperation,aseriousaccidentorchildbirth.Thethromboseddeepveinisfirstcompletelyblockedwithabloodclotbut,althoughthisquiterapidlyclears,the
delicatevalvesmaybepermanentlydamagedasaresult.Damagetothevalvesinthedeepveinspreventsthelegmusclesfrompumpingbloodout
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efficientlysothatthereisabuildupofhighpressureintheseveinswhichisthentransmittedtothelinkingveinsandbackintothesurfaceveins.Theseintheirturn
becomeswollenandvaricose(seediagramonpage117.)
Oncethevalvesystemhasbeendamaged,anumberofotherfactorsmayencouragetheformationofvaricoseveins,includingprolongedstanding,pregnancyand
possiblytheclimate.
Whenyou'reonyourfeetallday
Ifyouareoneofthosepeopleinanoccupationthathasyouonyourfeetagreatdeal,youwillhavenotroublefromyoursurfaceveinsprovidedthatthevalvesare
perfectlyhealthy.Butifthevalvesaredefectiveinanyway,thenthehighpressurethatarisesintheveinswhenyouarestandingwillundoubtedlyincreaseyourchances
ofdevelopingvaricoseveins.Althoughvaricoseveinsarenotcausednecessarilybyoccupationsthatinvolvestanding,peopleintheseprofessionsaremorelikelyto
noticethem.
Pregnancy
Thishaslongbeenknowntohaveaneffectonvaricoseveins.Manywomencomplainthattheirvaricoseveinsbecomemoreprominentanduncomfortableduring
pregnancy,andmanyevenclaimthattheyoriginatedduringtheirpregnancy.Therearetworeasonsforthis.Thefirstisthattheenlargedwombpressesontheveins
withinthemother'spelvisandthisactionslowsthereturnofbloodfromthelegstotheheart.Thismeansthatpressurebuildsupwithintheseveinsandthepressureis
transmittedallthewaybacktothesurfaceveinsoftheleg,whichthenexpand.Second,weknowthatfemalesexhormones(oestrogens)relaxthemusclesintheveins
andthisalsoincreasesthetendencyoftheveinstoexpand.Interestingly,theuncomfortablevaricoseveinsofpregnancyrapidlyimproveoncethebabyhasbeenborn
andoncethesetwoaggravatingfactorshavebeenremoved.
VaricoseveinsoccuringinpregnancyissuchanimportanttopicthatweshallbeexaminingtheproblemmorefullyinChapter4.
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Avalvedamagedbythrombosisinadeepveinallowsbloodtoflow
backwardsanddistendthesurfaceveins.
Heat
Awarmenvironmentorclimatecanalsoresultintheswellingofthesurfaceveinsoftheleg,andpeoplewithvaricoseveinswholiveorworkundersuchconditions
willcertainlynoticethattheirvaricoseveinsbecomerathermoreswollenanduncomfortable.
StayupStockings
Weareoftenaskediftight,constrictingarticlesofclothingaroundthelegscanproducevaricoseveins.Theredoesn'tseemtobeanyevidencethatthisisso.
However,itistruethatifyoualreadyhavevaricoseveinsthetightconstrictionaroundthelegmadebystayupstockingswillproducestagnationofthebloodinthe
dilatedveinsbelowtheconstriction,andthismaywellleadtoclottingofthebloodandanattack
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ofthrombosisintheleg.Long,tightboots,whichbecomefashionableeverynowandthen,compressthelegalongitslengthandareprobablyharmlessevenifyou
sufferfromvaricoseveins.Mostpeopletodaywearsensible,nonconstricting,comfortableclothes.Thosewhodoweargarters,suspendersandsoonneednot
worrythattheywillcausevaricoseveins.Theyshouldbeavoided,however,ifvaricoseveinsarealreadypresent.Sotooshouldanyothercauseofstagnationofthe
bloodsuchasprolongedsittingorstandingstill.
IsthereaCommonFactor?
Nowthatwehaveafairideaofwhatvaricoseveinsareandwhatcausesthem,thequestionthatinevitablyarisesiswhydotheyseemtobesocommon?Youonly
havetokeepyoureyesopenattheseasideorataswimmingpooltorealisejusthowcommontheyare.Yet,asfarasweknow,varicoseveinsoccuronlyin
people—wehaveneverseenasingleexampleofvaricoseveinsinanyotherspecies!Nodoubtthisistheresultoftheuprightpositionuniquetohumans,sothatthe
veinslyinginthesuperficialtissuesofourlegscometolie3547inches(or90120centimetres)belowtheheart,unsupportedexceptforalittlesurroundingfibrous
andfattytissue.Butifthatwerethecasethenpracticallythewholehumanracewouldbeafflicted,whereasweknowthisisnotso.
Therearefourimportantfactorsthatmanydoctorsbelievehavesomebearingonthefrequencyofvaricoseveins—heredity,race,dietandyoursex.
Heredity
Thereseemstobequitealotofevidencetosupporttheideathatvaricoseveinsareinheritedfromgenerationtogeneration.Ifthisistrue,thensomegoodadviceto
anyyoungpersonwishingtoavoidthemistobeverycarefulinthechoiceofhisorherparents!Infact,somethinglikethreequartersofallpatientswithvaricoseveins
haveotherclosemembersofthefamilywiththesamecondition.Thismaybeoneorbothparents,oneormorebrothersandsisters,andoftenothercloserelatives
suchasuncles,aunts,cousinsorgrandparents.Whenvaricoseveinsstartintheearlyteens(andoccasionallyweseevaricoseveinsbeginninginschoolchildren)
almostinvariablythereisaclearfamilyhistoryofthecondition.Inonestudyofpatientswithvaricoseulcers,
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''WernerBokelberg/theImageBank,©1999"
Alltheevidencepointstovaricoseveinsbeinghereditary.
Threeoutoffoursufferershaveclosefamilywiththesamecondition.
nofewerthannineoutofthetenpatientswereabletorecallcloserelativeswhosufferedfromvaricoseveins.
Race
Fromtheracialpointofview(andthisagainmayrepresentaninheritedfactor)itiswellknownthatpeoplesofthemoretechnologicallyadvancednationsofEurope,
NorthAmericaandAustralasiaareparticularlypronetovaricoseveins.Indeed,ithasbeenestimatedthatbetween10and20%ofthewhitepopulationofthe
Westernworldsuffersfromvaricoseveinstosomeextent.AlthoughvaricoseveinsdooccuramongpeoplesinAfrica,ontheIndiansubcontinentandintheFarEast,
theyarecertainlyfarlesscommonthanintheWesternworld.
ItistruethatsurgeonsworkingintheThirdWorldreportthattheyrarelyhavetooperateonthiscondition,butwehavetobeverycareful
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whenusinghospitalstatisticstobackupargumentsaboutracialdifferencesintheoccurrenceofvaricoseveins.
Interestinglyenough,varicoseveinsarefrequentlyfoundintheblackpopulationoftheUnitedStatesofAmerica.Itisafactthatraisesfascinatingargumentsasto
whethertheiroccurrencecanbeexplainedbyintermarriage—todayonlyaminorityofblackAmericansareofpureAfricanancestry—
orwhetherotherfactorssuch
asdietandexercisehavesomeparttoplay.
DoVaricoseVeinsResultfromourWesternLifestyle?
LetuslookalittlemorecloselyatsomeofthedifferencesbetweensocalledcivilizedWesternersandpeoplelivingin,say,ruralcommunitiesintheThirdWorld.Is
thewidespreadoccurrenceofvaricoseveinsamongWesternerscomparedwiththeirrelativeabsenceamongThirdWorldpeoplesdueentirelytoheredityorcan
someotherfactorsbeatwork?
Anyonewhohastravelledextensivelywillimmediatelyrealisethatthetwomostsignificantdifferencesbetweenthesetwogroupsofpeoplearetheirdifferentdietsand
theirdifferentlevelsofphysicalactivity.
Diet
Primitivemanexistedonadietoffruit,vegetablesandunprocessedgrains,withtheoccasionalluxuryofmeat,ifhewaslucky.Thissituationhasn'tchangedmuch
todaythroughoutmostoftheThirdWorld.Totakeinanadequateamountofenergy,largeamountsofthesefoodstuffsmustbeconsumeddaily.Consequently,the
ruralcommunitiesinmuchofAfrica,theIndiansubcontinentandtheFarEast,forexample,haveplentyofbulk,orroughage,intheirdiet,mostofitintheformof
cereal,fruitandvegetablefibre.Thesearethesubstancesthatformthecellwalloftheplantandprovideitsrigidstructure.Asaconsequence,thesepeoplespass
large,soft,bulkystools(faeces),witharapidtransittimethroughtheintestine.
ContrastthissituationwithourWesternculutrewhichhasadietofhighlyrefined(processed)foods.BreadintheWesternworldisprocessedsothatmuchofthe
coarsefibreofthegrainisremoved.Insteadofchewingonasugarcane,withitshighfibrecontent,wegetpure,refinedsugaroutofapacket.Thelowbulkofour
refinedfoodisreflectedinthemuchsmalleramountofstoolthatwepassdaily,oftenintheformofconstipatedpellets.Indeed,studiescomparingtheamountofstool
passedbytheaverageEnglishtowndweller(100
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