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ORIGINAL ARTICLE
Comparison of indices allowing an
evaluation of detrusor contractility in women
Comparaison des index permettant l’évaluation de la contractilité du détrusor chez la femme
F.A. Valentini
a,∗, B.G. Marti
a, G. Robain
a, P.E. Zimern
b, P.P. Nelson
aaSorbonneuniversité,hôpitalRothschild,75012Paris,France
bUTSouthwesternMedicalCenter,75390Dallas,TX,USA
Received31October2019;accepted27November2019 Availableonline19December2019
KEYWORDS
Detrusorcontractility indices;
Woman;
Urodynamics
Summary
Aims.—Tocompare 3detrusor contractility indices, projectedisovolumetric pressure (PIP- BCI),PIP1,andk fromthe VBNmathematicalmodel,for womenreferredfor evaluationof variouslowerurinarytractsymptoms(LUTS)inrelationshiptoage,presentingcomplaintand urodynamicdiagnosis.
Methods.—Urodynamic tracings of non-neurologicwomen were analyzed. Three indicesof detrusorcontractility were measured from the pressure-flowstudy.Exclusion criteriawere voidedvolume<100mL,stage>2 prolapse, interrupted flow, abdominal straining. Age sub- groups were pre-, peri- and post-menopause. Urodynamic diagnosis included incontinence findingsanddetrusoractivityduringvoiding.
Results.—Main complaint was incontinence (354 women); 95 women (Other) had non- incontinenceLUTS.PIP-BCI,PIP1andkdecreasedsignificantlywithageingineachsub-group.
PIP-BCIwassignificantlydifferentbetweenMUIandOther (P=.0259)whilePIP1 wassignifi- cantlyhigherinUUIvs.Other(P=.0161)andkinUUIvs.SUI(P=.0107),MUI(P=.0010)and Other(P=.0224).LowvalueofPIP-BCIforbladderoutletobstructionvs.detrusoroveractivity
∗Correspondingauthorat:Servicedemédecinephysiqueetderéadaptation,hôpitalRothschild,5,rueSanterre,75012Paris,France.
E-mailaddress:favalentini@gmail.com(F.A.Valentini).
https://doi.org/10.1016/j.purol.2019.11.004
1166-7087/©2019ElsevierMassonSAS.Allrightsreserved.
whilePIP1andkvalueswerehighandsimilarforthesetwodiagnosesandahighvalueofPIP- BCIfordetrusoroveractivitywithimpairedcontractilityclosetothevalueforbladderoutlet obstructionwhilePIP1andkwerelow.
Conclusion.—Evaluation ofdetrusorcontractility inwomen iseasily obtained usingindices PIP-BCIandPIP1orusingtheVBNnomogramgivingindice-parameterk.PIP1andparameterk producedcomparableandconsistentresultswiththeurodynamicdiagnosiswhilePIP-BCIleads toinconsistencies.
Levelofevidence.— 4.
©2019ElsevierMassonSAS.Allrightsreserved.
MOTSCLÉS Contractilitédu détrusor; Indexde contractilité; Femme; Urodynamique
Résumé
But.—Comparer3indicesdecontractilitédudétrusor:lapressionisovolumétriqueprojetée (PIP-BCI),PIP1etleparamètre(index)kdumodèlemathématiqueVBN,chezlesfemmesayant euunbilanurodynamiquepourévaluationdediverstroublesurinairesdubasappareil(TUBA), enfonctiondel’âge,delaplainteetdudiagnosticurodynamique.
Méthodes.—Les tracésurodynamiquesdepatientesnonneurologiquesontétéanalysés.Les 3indexdecontractilitédudétrusorontétécalculésàpartirdes donnéesl’instantané mic- tionnel.Lescritèresd’exclusionétaientunvolumeuriné<100mL,unprolapsusdegrade>2, undébitinterrompuouunepousséeabdominale.Lessous-groupesd’âgeétaientpré-,péri-et post-ménopause.Lediagnosticurodynamiquecomprenaitlebilandel’incontinenceetl’activité dudétrusoraucoursdelamiction.
Résultats.—Laplainte principale était uneincontinence pour 354patientes ; 95 patientes (OTHER)avaientdesTUBAsansincontinence.PIP-BCI,PIP1etkdiminuaientdemanièresignifi- cativeaveclevieillissementdanschaquesous-grouped’âge.LePIP-BCIétaitsignificativement plusélevé pourincontinencemixte vs OTHER (p=0,0259),PIP1 pourl’urgenturie vs OTHER (p=0,0161)etkpourl’urgenturievsincontinenced’effort(p=0,0107),vsincontinencemixte (p=0,0010)etvsOTHER(p=0,0224).UnevaleurbassedePIP-BCIétaitobservéepourobstruc- tion sous-vésicale vs hyperactivité du détrusor alors que les valeurs de PIP1 et k étaient élevées etsemblables pources 2 diagnostics. Une valeur élevéede PIP-BCIétait observée pourl’hyperactivitédudétrusoravechypocontractilité,prochedelavaleurdel’obstruction sous-vésicalealorsquelesvaleursdePIP1etkétaientbasses.
Conclusion.—L’évaluationdelacontractilitédudétrusorchezlafemmeestfacilementobtenue àl’aidedes indexPIP-BCIetPIP1oudunomogrammeVBNdonnantleparamètrek.PIP1et leparamètre-indicek conduisentàdesrésultatscomparables,cohérentsavec lediagnostic urodynamique,tandisquePIP-BCIconduitàdesincohérences.
Niveaudepreuve.— 4.
©2019ElsevierMassonSAS.Tousdroitsr´eserv´es.
Introduction
Evaluation of detrusor contractility in women remains a greatchallengemainlybecausetheconcept ofcontractil- ityhasnosimpledefinitionandalsobecausefirstattempts todefineacontractilityindexinwomenweremostlyderived fromtheevaluationofdetrusorcontractilityinmen.
Assessment ofdetrusorcontractility canbe madefrom isometric testing or pressure-flow studies. For isometric testinginawoman,arelativelysatisfactorymethodinvolves acontinuousocclusionof thebladderneckwithaballoon [1]butsuchatechniquefacesdrawbacksincludingpatient discomfort, interference with voiding, and difficulties in keepingtheballooninplace.Thusassessmentsofdetrusor
contractility using pressure-flow studies (PFS) make more senseinwomen.
The first index derived from PFSwas the Watts factor (WF),introduced by Derek Griffithsin 1985 [2]. However, WFcalculationis difficult without computerand itsvalue haspoorreproducibility.Asimplifiedapproachwasproposed byWernerSchafer[3]forobstructioninmalepatients.The projectedisovolumetricpressure(PIP)calledlaterbladder contractilityindex(BCI)byPaulAbrams[4]usesalinearized bladder output relation. This index is calculated from detrusorpressureat maximumflowpdet.Qmax andmaximum flowQmaxwiththefollowingformula:PIP=pdet.Qmax+K*Qmax. Schafer took K to be 5cmH2O/mL.s−1. So the PIP unit is expressedincmH2O.
Thesamelinearizedrelationwasappliedtowomen[5].
Butonthebasisofmeasurements(comparisonwithisovol- umetricpressurefrommechanicalstoptestandcontinuous occlusiontest),itwasnotedthataKvalueof5aschosenin menledtoagreatoverestimationinwomen.Thisfindingwas consistentwiththepropertiesoffemalevoidingdynamics, whichdiffer fromthoseof men.Clearly,Kvaluesarenot thesamefor menandwomen. Asimple indexcalledpro- jectedisovolumetricpressure1,(PIP1=pdet.Qmax+Qmax)was thenproposed[5].
The VBN model from our group [6] introduced the parameterk(thirdindex),whichcharacterizesdetrusorcon- tractility.Recentlyanomogram,basedonthismathematical model,wasproposedtocalculatethedetrusorcontractility inwomenfromapressure-flowstudy(PFs).
A nomogram was built from tables giving Qmax and pdet.QmaxforvariouscombinationsofkandVini(volumeinitial i.e.bladderfillingvolumeorvolumevoidedpluspost-void residual).These tableswereproduced taking intoconsid- eration thepresence of a urethralcatheter(typically6 F or7 Fr) duringPFs.Curves iso-kwere drawnin theplane [Qmax-pdet.Qmax]. Then the curves were fitted by algebraic equationsso theycanbeeasily solved andprogrammable inExcel[7]fornomogramsandcomparisonbetweencurves [8].Forall touse,this nomograminwomen simplyneeds 3measurements: pdet.Qmax,Qmaxandinitialbladdervolume (Vini).
Therefore,withourVBNmodelandcurrentnomogram, wewerein apositionofstudying detrusorcontractility in alarge femalepopulation. Consequently, theaims ofthis studyweretocomparePIP-BCI,PIP1andkinapopulation ofnon-neurologicwomenreferredforevaluationofvarious lowerurinary tractsymptoms (LUTS)and toevaluate the impactofage,primaryurologicalcomplaintforwhichUDS wasordered,andtheurodynamicdiagnosisfindingsrelated tothedetrusorcontractilityfindings.
Materials and methods
Urodynamic tracings of non-neurologic women who were referred for investigation of various lower urinary tract symptoms (LUTS) were retrospectively analyzed. All patients were evaluatedusing medical history, review of medications,bladderdiaryforatleast48hincludingvoid- ingtimesandvoidingvolumesbothdayandnight,physical examinationanddipstickanalysis(to excludewomenwith urinarytractinfection).Eachurodynamicsessionwasper- formedusinganurodynamicunitfromLaborie(Mississauga Canada).Urodynamic testswere carried out according to theInternationalContinenceSocietyGoodUrodynamicPrac- tices[9].Bladderwasfilledwithsalineatroom-temperature at a medium filling rate of 50mL/min. Filling cystomet- rogramwasobtained via a triplelumen urethral catheter 7 F allowing for urethral pressure recording followed by an intubated flow (IF). During IF, pdet.Qmax and Qmax were measured.Post-voidresidualvolumes(PVR)weremeasured usingaBladder-scan.TheinitialbladdervolumeorViniwas calculatedbyaddingthevoidedvolumetothePVR.
Excludedwerewomenwhohadaurinarytractinfection onpresentation andthose unabletovoid during thePFS, whoexpelledtheir urethralcatheterduring theIF,voided
lessthan100mL,orhadpelvicorganprolapseofgrade≥2.
In addition, those withan interrupted flow or voiding by abdominalstrainingwerealsoexcluded.
In all patients, the main complaint for undergoing UDS, the UDS final diagnosis, age and the computations of the three studied indices were carried out to allow comparisons between symptomatology, study findings and objective detrusor contractility indices. PIP-BCI and PIP1 were expressed in cm H2O, whereas k was unit less. For agegroupanalysesand,consistentwithapriorpublication [10],thislargepopulationofwomenwasdividedbetween
‘‘reproductive(<45y)’’,‘‘peri-menopausal(46—65y)’’and
‘‘post-menopausal(>65y)’’agegroups.
AccordingtoICS/IUGArecommendations[11],themain categories of urodynamic diagnoses were bladder out- letobstruction(BOO),detrusoroveractivitywithimpaired contractility (DHIC), detrusor overactivity (DO), detru- sor underactivity (DU). Some investigations were found
‘‘normal’’ (N) and other related to urethral dysfunction (intrinsicsphincterdeficiency[ISD]orvoidingtriggered by urethralrelaxation[URA]).
This retrospective study wasconducted in accordance withthedeclarationofHelsinki.The localpracticeofour Ethics Committee does not require a formal institutional reviewboardapprovalforretrospectivestudies.
Statistical analysis
Datawere presented asmean±SDand range.Analysis of variance (ANOVA), ttest, andthe Chi2 test were usedas appropriate.All statisticalresults wereconsidered signifi- cant atP<0.05.Statisticalanalyses wereperformedusing SAS,version5.0(SASInstitute,Inc.,Cary,NC).
Results
FromJanuary2008toDecember2017,westudiedandcol- lected dataon4557 women. Fourhundredand forty-nine urodynamic tracings met study criteria in non-neurologic women referred for LUTS. Mean age was 59±16years [20—96y].Maincomplaintwasurinaryincontinence:stress (96SUI),mixed(140MUI),urge(118UUI).Womenwithcom- plaints other than incontinence (95 women) were called OTHER;amongthem, 38 complainedofurinaryfrequency (FR)and16fromdysuria(D).
Lookingatagesub-groups,PIP-BCI,PIP1andkdecreased withageing,eachsub-groupbeingsignificantlydifferentof theothers(Table1).
Table1 Valueoftestedindicesvs.age.
Age <45y(n=107) 46—65y(n=159) >65y(n=183) PIP-BCI 113.25±37.16 94.51±33.10 83.77±36.98 PIP1 49.40±20.18 38.78±16.71 32.54±14.63 k .588±.479 .358±.357 .260±.388 46—65y vs.<45y: PIP-BCI P<0001; PIP1 P<.0001; k P=<.0001.>65yvs.46—65y:PIP-BCIP=.0055;PIP1P=.0005;
kP=.0248.
Table2 Valueoftestedindicesvs.maincomplaint.
Complaint SUI(96) MUI(140) UUI(118) OTHER(95)
Age 54.8±15.7 61.7±15.9 59.4±15.4 57.8±17.4
PIP-BCI 94.8±35.6 100.0±41.7 93.5±35.1 88.8±36.6
PIP1 38.7±19.2 38.7±17.7 41.9±19.6 35.8±16.4
k 0.30±0.34 0.28±0.33 0.43±0.46 0.30±0.29
SUI:stressurinaryincontinence;MUI:mixedurinaryincontinence;UUI:urgeurinaryincontinence;OTHER:lowerurinarytractdysfunction withoutincontinence.
RegardingmaincomplaintforwhichtheUDSwasordered, there was no significant difference in PIP-BCI except between MUI andOther (P=.0259) while PIP1was signifi- cantlyhigherinUUIvs.Other(P=.0161)andkinUUIvs.SUI (P=.0107),MUI(P=.0010)andOther(P=.0224)(Table2).
Difference in age wassignificant between SUI and MUI (P=.0014)andbetweenSUIandUUI(P=.0401)asSUIwomen wereyounger.
Lookingaturodynamicdiagnosessomesurprisingresults werenotedsuchas:
• a lowvalue of PIP-BCIfor BOOvs.DO whilePIP1 andk valueswerehighandsimilarforthesetwoUD;
• a relatively high value of PIP-BCI for DHIC closeto the valueforBOOwhilePIP1andkwerelow(Table3)(Fig.1).
Discussion
Toourknowledgethisisthefirstlargestudyinwomenthat comparesthreedetrusorcontractilityindices.PIP-BCI and PIP1 were chosen because of the commonacceptance of thesetwoindices.TheVBNmodelofferedathirdindexfor comparison.Yet,bladdercontractility in womenhasbeen seldomstudiedandthereisnoconsensusonthebestindex toevaluateit.
Until the recent studies of C.Fry [12] andA. Gammie [13],indicestoestimatedetrusorcontractionstrengthfrom pressure-flowstudiescomprisedtheWattsfactorproposed byD.Griffiths[2],theW.Schafernomogram[7]leadingto PIP-BCI index, later modified to PIP1 by Tan etal. [5] in older women, and the VBN nomogram [8] which provides theVBNdetrusorcontractility parameterk.FryandGam- mieproposedindicesdeducedfromtheincreasingphaseof
Figure1. VariationsofPIP-BCI,PIP1andVBNparameterkvs.uro- dynamicdiagnosis.BOObladderoutletobstruction;DHICdetrusor overactivitywithimpairedcontractility;DOdetrusoroveractivity;
DUdetrusorunderactivity;ISDintrinsicsphincterdeficiency;Nnor- mal;URAvoidingtriggeredbyurethralrelaxation.
isovolumetricpressure,maximumrateofpressuredevelop- ment(vCE)[12]anddetrusorcontractilityparameter(DCP) alsonamedt20—80(timeintervalbetweendetrusorpressure risingfrom20to80%ofitsvalueoncetheflowstarts)[12].
Unfortunately,theseproposedindicesareseldomrelevant becauseofinherentlimitationsintheurodynamictracing, includingtheneed for veryhigh qualityurodynamic trac-
Table3 Characteristics(age,valueofthedifferentindicesandparameter)forurodynamicdiagnoses(UD).
UD n Age(y) PIP-BCI(cmH20) PIP1(cmH20) k(nounit)
BOO 47 57.8±18.1 87.5±31.6 51.6±19.6 .69±.43
DHIC 24 65.3±13.3 84.5±34.2 32.1±12.5 .22±.29
DO 82 57.9±17.2 101.9±37.2 49.4±20.9 .65±.50
DU 86 65.5±12.9 75.8±40.7 23.7±9.9 .04±.17
ISD 81 59.7±16.3 101.0±38.8 34.8±12.9 .26±.33
N 105 52.5±14.3 102.2±29.9 41.6±10.3 .43±.22
URA 24 57.0±18.9 105.9±38.9 38.7±26.6 .31±.62
BOO: bladder outlet obstruction; DHIC: detrusor overactivity withimpaired contractility;DO: detrusor overactivity; DU: detrusor underactivity;ISD:intrinsicsphincterdeficiency;N:normal;URA:voidingtriggeredbyurethralrelaxation.
ings,timedelayonthepressuresignal, negligiblepdet rise beforetheflow starts,and someassumptions suchasthe bladdershapeisalwayssphericalandthesametimecons- tant to reach the maximum isovolumetric pressure P0 in thegeneral population [14].The Watts Factorcalculation isdifficultwithoutacomputeranditsvaluehaspoorrepro- ducibility.Referencevalueswereobtainedfrom8healthy volunteerswhodidnotalwaysperformedidealvoidingtrac- ings. Forthe PIP-BCI index, it has been mostly measured inmenandis beingusedforwomen insteadofrelying on PIP1.
In this study, evaluations of PIP-BCI and PIP1 were obtainedfromcoordinates(pdet.QmaxandQmax)ofaremark- ablepointoftheintubatedflow,i.e.thepointofmaximum flow.Evaluationof theVBN contractility parameter kwas alsoobtainedfromthevaluesofthecoordinatesofthispoint buttookintoaccountthefillingvolume(Vini,pdet.Qmax and Qmax)tousethenomogram.
Of note, our mathematical model has a few hidden hypothesesincludingnosignificant contributionofabdom- inalpressurebetweenonsetofflowandQmaxandstandard nervous excitations of the detrusor until Qmax. The first hypothesis was easily dismissed as we always excluded womenwhostrainedtovoid.However,thesecondhypoth- esis holds true in general in the non-neurogenic women populationbut couldotherwise beviewedasa studylim- itation.
Regardlessoftheindicesmeasured,detrusorcontractil- itywas found to decrease withageing. This is consistent with prior study from Valentini et al. [15]. Analysis of a population (divided in sub-groups by age decade) of 125 PFsfromnon-neurogenicwomenwithoutsymptomsugges- tive of obstruction, no history of prior anti-incontinence surgery,referredforevaluationoflowerurinarytractdys- function(LUTD)showthatthevalueofkremainedsimilarin sub-groupslessthan50yearsanddecreasedregularlywith ageing.Theyconcludethatdetrusorcontractilitybeginsto decreaseatmenopauseanddeteriorates sharplywithfur- therageing.
This study offered an insight into the relationship betweenthemainpresentingcomplaintforwhichUDSwas ordered and these 3 indices of detrusorcontractility. We observedthatallindiceswerelowerforwomenwithoutany urinaryincontinencecomplaint.However,highervaluesof PIP-BCI werenoted in the MUI group, and PIP1and k for theUUIgroup.Interestingly,forthekindex,itshighvalue forUUIwassignificantlydifferentthanitsvaluefortheSUI, MUIandnoincontinencegroups.Thatconditioncouldbethe consequenceofsomedegreeofurgency.
Whencomparingthe3indiceswiththeUDSdiagnosisat thecompletion ofthe urodynamic study,PIP1and k gave similarevaluationofdetrusorcontractility,namelynormal valueswhentheurodynamicdiagnosiswas‘‘normal’’,low fordetrusorunderactivity,andhighfordetrusoroveractivity andbladderoutletobstruction [15].This consistentobser- vationconfirmedthereliabilityofthedetrusorcontractility estimatesusingtheVBNparameterkorthePIP1,whilePIP- BCIwasfoundtohavemanyinconsistencies.
ThisfindingisnovelforPIP1whichhasonlybeenstudied sofarinagroupofelderlyfemales (53—89yearsold)suf- feringfromurgeurinaryincontinence.Instead,inourstudy, 26of107womenyoungerthan45yearscomplainedofurge
incontinence.Soourstudybroadenstheagerangeforwhich PIP1canbeusedfordetrusorcontractilitymeasurements.
Lastly,therearelimitationstotheuseofkasadetrusor contractility index,andthoseareprimarily relatedtothe voidingperformance.Asalreadyalludedto,theyincludea non-interruptedflowuntilreachingQmaxandnosignificant abdominal straining. Although these two conditions were appliedinthemathematicalcomputationofthekindex,to ourknowledgetheyhavenotbeenevaluatedinthedevel- opmentofPIP-BCIandPIP1.
Conclusion
An evaluation of detrusor contractility derived from an intubated flow was obtained using indices BCI, PIP1 or the VBN-derived kparameter in a large cohort of women referred for urodynamic testing with or without inconti- nencesymptomatology.PIP1andthekparameterproduced comparableandconsistentresultswiththeurodynamicdiag- nosis while BCI had inconsistencies. All three indices of detrusorcontractilitydecreasedwithaging.SincethePIP1 and kindicesareeasy tomeasure, theymight eventually influencethemanagementofsomewomenwithloweruri- narytractsymptoms.
Disclosure of interest
Theauthorsdeclarethattheyhavenocompetinginterest.
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