Neurogenic lower urinry trct dysfunction: the role of urodynmics The min im in mnging neurogenic lower urinry trct dysfunction is preservtion of the upper trcts y ensuring optiml ldder function. Krlheinz Jehle, MB ChB, MRCS, FC Urol (SA) Registrr, Deprtment of Urology, Groote Schuur Hospitl, Cpe Town Krlheinz Jehle is registrr in the Deprtment of Urology t Groote Schuur Hospitl nd hs n interest in peditric urology. John Lzrus, MB ChB, MMed, FCS (Urol) Consultnt Peditric Urologist, Red Cross Wr Memoril Children s Hospitl, Cpe Town John Lzrus is consultnt peditric urologist t Red Cross Wr Memoril Children s Hospitl nd senior lecturer in the Division of Urology t Groote Schuur Hospitl nd the University of Cpe Town. Jenette Rd, Nt Dipl Med Tech (Hem, Micro & L Animl) Urodynmicist, Red Cross Children s Hospitl, University of Cpe Town Jenette Rd trined s medicl technologist in hemtology nd microiology. She joined the Deprtment of Peditric Surgery s resercher in 1988 nd hs estlished dedicted peditric oesophgel nd norectl mnometry nd urodynmic units t Red Cross Children s Hospitl in Cpe Town. Before the 1980s, ptients with spinl cord injury died minly from urinry trct complictions, prticulrly renl filure, ut lso stone disese nd infections. Even tody ptients with neurogenic lower urinry trct dysfunction (NLUTD) present significnt chllenge to clinicins. 1 The chief mngement ojective remins preservtion of the upper trcts y ensuring optiml ldder function. Bldder dysfunction remins mjor cuse of moridity, nd urodynmic studies (UDS) offer criticl informtion which guides medicl nd surgicl cre nd undoutedly impcts positively on ptient qulity of life. This rticle focuses on the role of urodynmics nd its interprettion in this setting, nd gives some index cse studies to illustrte its role. of prolems with the ldder itself, the outlet, or oth) or filure to empty (ecuse of prolems with ldder function, outlet resistnce or comintion). A schemtic exmple of the functionl clssifiction is shown in Fig. 1. Aetiology nd clssifiction of NLUTD Mny custive fctors re responsile for neurogenic ldder dysfunction. Congenitl cuses include neurl tue defects, most commonly myelomeningocele (spin ifid) nd tethered spinl cord (spin ifid occult) s well s scrl genesis, norectl mlformtions nd clocl nomlies. Acquired cuses include, mong others, spinl cord trum nd tumours. Clssifying neurogenic ldders ccording to the level of the neurologicl insult is difficult ecuse neurologicl diseses do not respect these ntomicl oundries nd mixed lesions re common. It is, however, useful to differentite rodly etween n overctive upper motor neuron-type ldder nd n tonic lower motor neuron-type ldder. Among the mny different clssifiction systems of neuropthic ldders, we find the functionl clssifiction simple nd cliniclly useful. 1 It is sed on evluting the two primry functions of norml ldder: firstly, to store sufficient volume of urine t low pressure; nd secondly, to efficiently empty the ldder. Pthology cn then e clssified into either filure to store urine (ecuse Fig. 1. The Europen Assocition of Urology (EAU)-Mderscher clssifiction system. Investigtion nd dignosis Prior to urodynmic ssessment comprehensive history, physicl exmintion nd urinlysis (to exclude infection) re required. History should focus on pst nd present ldder, owel nd sexul function. Exmintion ttempts to define the level of the neurology tht usefully predicts ldder function. Imging studies to exclude upper-trct dilttion (ultrsound) nd ssess ldder cpcity nd reflux (cystogrm) re indicted, in ddition to mesurement of renl function (serum cretinine). 166 CME My 2012 Vol.30 No.5
Types of urodynmic studies Before discussing the vrious types of nd indictions for UDS, it is importnt to rememer Victor Nitti s three principles of UDS: 2 A study which does not duplicte symptoms is not dignostic. Filure to record n normlity does not rule out its existence. Not ll normlities recorded on UDS re cliniclly significnt. Terminology used in this pper conforms to the updted stndrdised terminology produced y the Interntionl Continence Society. 3 A similr document is ville for peditric prctice. 4 The prcticl nd technicl spects of performing UDS re eyond the scope of this rticle nd the reder is referred to textooks listed under Suggested reding. Bldder dysfunction remins mjor cuse of moridity, nd urodynmic studies (UDS) offer criticl informtion which guides medicl nd surgicl cre nd undoutedly impcts positively on ptient qulity of life. Non-invsive urodynmics Volume voided chrt On the chrt, lso clled ldder diry, the ptient records fluid intke, time nd volume of voids, incontinence episodes nd ctheteristion episodes. When documented for 2-3 dys, these detils cn give informtion out functionl ldder cpcity. Flow rte nd residul This is non-invsive wy of mesuring the mount of urine pssed within period of time, expressed in millilitres per second (ml/s). One cn lso evlute the grph shpe (norml ell-shped v. stccto- or plteu-shped) to gin insight into voiding prolems. Use two consecutive mesurements with voided volume of t lest 150 ml nd comine with ultrsound to ssess postvoid residul volume. Electromyogrphy (EMG) cn ssess sphincter function. A mximum flow rte (Q mx ) in men of more thn 15 ml/sec is norml nd less thn 10 ml/sec is considered norml. Invsive urodynmics Cystometrogrm This investigtion mesures the pressure-to-volume reltionship of the ldder during filling nd voiding, usully recorded on grph. It ims to ssess the ldder s senstion, cpcity, complince nd detrusor ctivity. During ldder filling the first senstion of ldder filling (which correltes with 50% cpcity) through to the strong desire to void (correlting roughly with 90% cpcity) re recorded, long with senstions of urgency. Mximum cystometric cpcity (when ptient with norml senstion cnnot dely micturition ny longer) must e correlted with functionl cpcity, which is the lrgest volume voided recorded in voiding diry. A norml cpcity is etween 300 nd 500 ml. Bldder complince descries the reltionship etween the chnge in volume nd chnge in detrusor pressure nd is expressed in millilitres per centimetre of wter (ml/cmh 2 O) with 20 eing the norml vlue. Norml detrusor function (or stle ldder) shows no chnge in detrusor pressure during filling while overctivity shows involuntry detrusor contrctions, which my e spontneous or provoked y certin ctions such s coughing. Pressure flow studies simply depict the reltionship etween volume nd pressure during micturition nd thus cn differentite etween ostruction nd hypocontrctility. They cn lso identify ptients with normlly high pressure voiding nd consequently norml flow rtes, ut cnnot identify the site of ostruction. Lek-point pressures re importnt prmeters to record when performing cystometrogrphy in neurogenic ptients. The detrusor lek-point pressure (DLPP) is the lowest detrusor pressure reding t which lekge is oserved in the sence of incresed dominl pressure or detrusor contrction. This is very importnt s high DLPP (over 40 cmh 2 O) my indicte tht the upper trcts re t risk of deteriortion ecuse the ldder hs lost the ility to fill while mintining low pressure. According to the functionl clssifiction, this could either e due to prolems with the outlet (detrusorsphincter dyssynergi (DSD)) or prolems with the ldder. With incresing pressures inside the ldder the incresing volume of urine hs only two options: to lek out vi the urethr or to reflux ck up towrds the kidney vi the ureter. The higher the pressure needed to overcome the urethrl outlet, the more likely the urine is to cuse upper trct dmge. Invsive UDS is indicted to evlute nd chrcterise NLUTD. It should e used erly in the mngement nd repeted to void upper trct deteriortion. In the peditric setting children with meningomyelocele should first undergo UDS in the neontl period. Clssifying neurogenic ldders ccording to the level of the neurologicl insult is difficult ecuse neurologicl diseses do not respect these ntomicl oundries nd mixed lesions re common. When performing urodynmics in ptients with spinl cord lesions ove T6 level, one runs the risk of precipitting utonomic dysreflexi. This usully presents with hypertension ssocited with rdycrdi, dizziness or hedche nd profuse sweting nd is cused y n uninhiited sympthetic outflow in response to stimulus elow the level of the injury, for exmple overfilling of the ldder or high detrusor pressures. Cre should e tken to void this y using slow filling. If utonomic dysreflexi occurs, the study should e stopped nd the ldder emptied; hypertension should e treted. 167 CME My 2012 Vol.30 No.5
Neurogenic LUTD Electromyogrphy (EMG) Normlly the urethr opens nd is continuously relxed during voiding so tht micturition tkes plce t norml pressure with mximum flow. Modern urodynmic mchines include ptch electrodes (like those used for electrocrdiogrms (ECGs)) for ssessment of pelvic floor neuromusculr tone (through which the urethr runs). This non-invsive ssessment is useful djunct to urodynmics. Its iggest role is to dignose DSD. This is common finding in neurogenic ldders nd is evidenced y lck of the norml relxtion (grphiclly quiet trce ) of the externl urethrl sphincter during contrction of the detrusor to void. Pressure flow studies simply depict the reltionship etween volume nd pressure during micturition nd thus cn differentite etween ostruction nd hypocontrctility. Video-urodynmics This modlity comines cystometry with fluoroscopic imging of the lower urinry trct nd enles the urologist to evlute the ntomy together with function. This is importnt when identifying lek point pressures nd DSD, ut cn lso detect vesico-ureteric reflux, diverticule nd stones. In ptients with incontinence, the ntomy of the ldder neck nd urethrl hypermoility my e demonstrted. Cse studies This section ims to descrie UDS ptterns tht re commonly seen in clinicl prctice. Fig. 2 illustrtes the typicl UDS setup nd ctheter rrngement. A dul lumen ctheter is plced in the ldder to infuse sterile sline nd simultneously mesure intrvesicl pressure vi the second chnnel. A rectl ctheter cts s control to sutrct the contriution of intr-dominl pressure from true detrusor pressure. This detrusor pressure is computer-derived vlue displyed in rel time. The cystometrogrm mesures the volume/pressure reltionship s shown in Fig. 3. A norml cystometrogrm is shown in Fig. 3. Here the 3 top lines represent the vesicl, dominl nd computer-derived or true detrusor (vesicl minus dominl) pressure. The 4th line (in yellow) represents urine flow during norml micturition reflex t the end of the study. The normlity of the study is confirmed y low pressure filling to norml cpcity, indicting normlly complint ldder, with n pproprite rise in detrusor pressure during the micturition reflex nd ttendnt ell-shped uroflow. Fig. 4 illustrtes the importnce of the derived detrusor vlue. This trce shows tht the rise in vesicl pressure (Pves) is ccompnied y simultneous rise in dominl pressure (Pd) nd hence is cncelled out on the Pdet or the derived detrusor trce. This represents n rtefct, proly cough nd not n uninhiited detrusor contrction. 1 = ureter; 2 = ldder; 3 = prostte glnd; 4 = penis; 5 = urethr; 6 = testes; 7 = epididymis; 8 = vs deferens; 9 = rectum; 10 = seminl vesicle. Fig. 2.. Typicl UDS setup. Dul lumen ctheter to llow simultneous infusion nd pressure mesurement, nd seprte rectl ctheter s control for intr-dominl pressure nd thus llowing computerderived true detrusor pressure.. Dedicted peditric urodynmic nd sonr suite t Red Cross Children s Hospitl. 168 CME My 2012 Vol.30 No.5
Fig. 5. Typicl steep trce of poorly complint ldder, with reduced cpcity nd elevted detrusor lek point pressure (DLPP). cpcity is usully reduced nd the DLPP is elevted ove the dnger threshold of 40 cmh 2 O. Aove this vlue urine flow from the kidneys is impired. Additionlly, there re smll wves of detrusor instility throughout the study. Bldder senstion is reduced nd other senstions (e.g. utonomic dysreflexi) nd incontinence occur. 1 Fig. 3.. Cystometrogrm mesures ldder volume/pressure reltionship;. Norml cystometrogrm: vesicl, dominl nd derived trces. Fig. 6 shows mrked neurogenic detrusor overctivity with reduced complince nd ttendnt urine incontinence with ech wve of instility. This overctivity would e expected to improve with nticholinergic therpy. Fig. 4. Artefct shown y rise in vesicl pressure (Pves) ccompnied y rise in dominl pressure (Pd) without computer-derived rise in true detrusor pressure (Pdet). Fig. 5 demonstrtes the cystometrogrm of ptient with neuropthic ldder secondry to myelomeningocele. It shows, from top to ottom, the vesicl, detrusor (clculted y computer) nd dominl trces. Compred with the norml trce in Fig. 3, there is steep rise in pressure with ldder filling. This represents typicl poorly complint ldder. The Fig. 6. A ptient with neurogenic detrusor overctivity with decresed ldder complince s well s involuntry detrusor contrctions leding to urine leks. At the other end of the neuropthic ldder spectrum is the tonic ldder with n underctive detrusor tht shows incresed cpcity nd complince on UDS. Fig. 7 demonstrtes such ldder. Typiclly filling exceeds >1.5 times the expected cpcity with reduced senstion of ldder filling noted y the ptient. 169 CME My 2012 Vol.30 No.5
Fig. 7. A ptient with n tonic or underctive detrusor with incresed cpcity (700 ml), incresed complince nd reduced senstion during filling. In ddition to stndrd UDS, EMG dt cn esily e otined with non-invsive ptch electrodes. The dditionl informtion derived from EMG is n ttempt to dignose DSD. DSD occurs when the ldder contrcts ginst closed pelvic floor (the externl urethrl sphincter). This usully ccompnies poorly complint ldder with high DLPP. DSD represents the most serious consequence of the neuropthic ldder s it produces so-clled hostile ldder tht thretens the upper urinry trcts. Fig. 8 schemticlly shows the norml EMG trce during the micturition reflex. Note tht the EMG trce of the pelvic floor is sid to e quiet (i.e. relxed) during the detrusor contrction. Fig. 8 demonstrtes DSD. Here the sphincter is hyperctive during n ttempted micturition. Conclusion UDS plys n importnt role in the dignosis, tretment plnning nd surveillnce of ptients with NLUTD. In South Afric these services re underdeveloped nd underutilised, which results in preventle moridity. It is hoped tht this overview of UDS will prompt doctors to refer more ptients for comprehensive ssessment. References nd suggested reding ville t www.cmej.org.z Fig. 8.. Schemtic representtion of norml ( quiet ) EMG trce during the micturition reflex.. Detrusor-sphincter dyssynergi (DSD) is shown y the hyperctive sphincter/pelvic floor (EMG) trce during micturition. In nutshell Neurogenic ldders cn cuse moridity (infections, stones, incontinence) nd mortlity (renl filure, urosepsis). Urodynmic studies (UDS) re functionl studies of the lower urinry trct; they evlute oth the storge nd the emptying functions of the ldder. Different types of neurogenic ldders exist nd the chrcteristics of prticulr ldder my chnge with time. History should py ttention to ldder, owel nd sexul function. Exmintion should define neurology nd exclude infection nd upper trct dilttion. UDS cn e simple nd non-invsive (ldder diry, flow rte) or invsive (cystometrogrm, video-urodynmics). A cystometrogrm mesures the reltionship etween ldder filling nd pressure. Prmeters used to chrcterise the ldder re cpcity, complince, detrusor ctivity nd sphincter ctivity. Detrusor lek-point pressure (DLPP) over 40 cmh 2 O predicts upper trct deteriortion in neurogenic ldders. 170 CME My 2012 Vol.30 No.5