Urodynamics: prediction, outcome and analysis of mechanism for cure of stress incontinence by periurethral collagen

Transcription

1 British Journal of Obstetrics and Gynaecology February 1997, Vol. 14, pp Urodynamics: prediction, outcome and analysis of mechanism for cure of stress incontinence by periurethral collagen Ash K. Monga Senior Registrar, Stuart L. Stanton Consultant (Urogynaecology) Urogynaecology Unit, St George i Hospital, London Objective To assess the role of urodynamics in the prediction and assessment of outcome and analysis of the mechanism of cure for stress incontinence using periurethral collagen as our treatment model. Design Prospective longitudinal study. Setting A teaching hospital tertiary referral centre. Patients Sixty women with genuine stress incontinence. Results The objective cure rate was 54% (n = 54) at 12 months. Subtracted cystometry, urethral electrical conductivity and bladder neck excursion measurements did not predict cure. A low pre-injection maximum urethral closure pressure adversely affects outcome (31 cmh2 (success) vs 19 cmh,o (failure), P =.4); all women with a maximum urethral closure pressure > 39 cmh,o were rendered dry. Urethral pressure profilometry can analyse mechanism of cure. Total profile length, stress maximum urethral closure pressure, stress functional urethral length and pressure transmission ratio in the first quarter of urethral length were increased in successful cases (P <.5), and rest maximum urethral and maximum urethral closure pressures, area under rest profile and pressure transmission ratio in the second quarter of urethral length were increased in failed cases (P < -2). Conclusions In successful cases the increased area and pressure transmission ratio in the first quarter of the functional urethral length suggest that collagen placement occurs at the bladder neck or proximal urethra. Cure appears to be due to prevention of bladder neck opening during stress and not obstruction. In addition the cephalad elongation of the urethra caused by collagen probably accounts for the increased abdominal pressure transmission in the first quarter of the urethra. In failures, there is an increased length and increased area to peak pressure suggesting collagen is deposited more distally. This study confirms the role of certain urethral pressure profilometry variables in the prediction and analysis of mechanism of cure. INTRODUCTION Ideally, urodynamic investigations should predict and assess outcome, and analyse the mechanism of cure for treatment of urinary incontinence. Most studies investigating these issues have evaluated surgical techniques that correct genuine stress incontinence, although some authors have examined pelvic floor exercises, using variables obtained fiom uroflowmetry, subtracted cystometry with or without video studies and urethral pressure profilometry. It has been demonstrated that pre-operative detrusor instability has an adverse affect on the outcome of continence surgery 12. This appears to be accentuated in women with systolic detrusor instability compared with low compliance detrusor instability3, and the height of systolic contraction has an inverse relation Correspondence: Mr S. L. Stanton, Urogynaecology Unit, St George s Hospital, Blackshaw Road, London SW17 SQT, UK. with success4. Bhatia and Bergmad reported that women with low pre-operative voiding pressure had increased post-operative voiding difficulty. The delay in resumption of normal voiding was greater in those women with low maximum flow rate. The predictive value of low voiding pressure has been confirmed by Lose et al6. A low maximum urethral closure pressure and hctional urethral length have been shown to predispose to an adverse outcome in women with genuine stress incontinence undergoing pelvic floor exercises, colposuspension8, suburethral sling9j, anterior colporrhaphy, StameyloJ2 and Marshall- Marchetti-Krantz procedures. The mechanisms by which treatments achieve continence have been examined using urodynamic studies. Outflow obstruction plays a role after colposuspension8: a significant increase in maximum urethral closure pressure and functional urethral 158 RCOG 1997 British Journal of Obstetrics and Gynaecology

2 URODYNAMICS AND CURE OF STRESS INCONTINENCE 159 Table 1. Patient characteristics. Values are shown as mean (range). Table 2. The means of pre- and post-injection cystometric variables. Variables Group 1 Group 2 (n = 29) (n = 25) Variables Group 1 Group 2 Pre Post Pre Post Age (years) 62 (2-85) 65.5 (31-9) Parity 2.5 (-7) 1.7 (-5) Weight (kg) 65 (48-88) 67 (46-89) Duration of incontinence (years) 1.2 (1-29) 13.2 (1-37) Previous continence procedures (n = 55) 1.6 (4) 1.6 (-5) length and enhancement of pressure transmission ratio in the proximal urethra during stress profilometry is reported after successful colposuspension. In failure, pressure transmission ratio was raised more distally. Increased pressure transmission ratios are also recorded after successful pelvic floor exercises and significant increases occur after successful Marshall-Marchetti-Krantz pro~edure ~, Stamey procedurei and both abdominal and abdomino-vaginal sling procedures1 J4. In a prospective study we used a 1 h pad test, subtracted cystometry, urethral pressure profilometry, urethral electrical conductivity and ultrasound for bladder neck excursion before and after periurethral collagen for genuine stress incontinence and analysed the results to determine if these investigations can predict urodynamic outcome or explain the mechanism of continence; we have tried to determine if urodynamic assessment is relevant for women undergoing collagen injection. We have previously published clinical outcomes at two yearsi5 for the whole group and for the elderly women within the group (this issue, pages )16. METHODS Following approval by the hospital s ethical committee, 6 women were enrolled and gave informed written consent. Inclusion criteria and methodology have been previously de~cribed ~J J~ as follows: Allergy test. Pre-injection: cystometry, pad test, urethral pressure profilometry, urethral electrical conductivity, bladder neck ultrasound for excursion measurement. Day case injection under local anaesthetic. 3 and 12 months post-injection: cystometry, pad test, urethral pressure profilometry, urethral electrical conductivity, bladder neck ultrasound for excursion measurement. Contigen collagen (Bard, Crawley, United Kingdom) was utilised in this study. Objective cure was defined as the inability to demonstrate genuine stress incontinence during provocative cystometry and Bladder capacity (ml) Peak flow rate (ml/s) Maximum voiding pressure (cmh,o) Detrusor instability (n) Bladder neck excursion (mm) ,6 7.9 Urethral electrical conductivity (cm) 4.* 4.4* 3.6* 4.1 * * P <.5 Wilcoxon s signed rank test negative (< 1 g) pad test. All terms and definitions are in accordance with the International Continence Society19. Urodynamic data have been analysed to determine if they are useful in the prediction and assessment of outcome and whether they will explain the mechanism of cure. In particular specific variables from urethral pressure profiles were analysed. Paired t tests were utilised to analyse differences within groups for parametric data and the Wilcoxon s signed rank test for nonparametric data. Unpaired t tests were used to analyse difference in pre- and post-operative means between success and failure (nonparametric data were logarithmically transformed first). A P value <.5 was considered significant. RESULTS Fifty-nine women attended for the three month follow up and 54 for the 12 month follow up. The objective cure rate was 61% at three and 54% at 12 month follow up. Those that were objectively cured at one year are referred to as Group 1 and those that were objective failures as Group 2. The characteristics of the patients are shown in Table 1. There were no clinically significant differences. The mean pre-injection urine loss (1 h pad test) did not influence outcome at 12 months (Group 1, 18.6 g vs Group 2, 22.3 g, P = not significant). Table 2 displays cystometric variables, bladder neck excursion and urethral electrical conductivity measurements in Group 1 and Group 2. There is no increase in maximum voiding pressure or decrease in peak flow rate which might have suggested obstruction and this was unsupported by the absence of subjective evidence of voiding difficulty. No pre-operative cystometric variable predicted outcome and with the exception of urethral electrical conductivity, no variable changed significantly after collagen injection. Although the numbers are small, detrusor instability did not appear to influence outcome. Table 3 shows the mean and median values of urethral pressure profile parameters pre and post RCOG 1997 Br J Ohstet Gynaecol 14,

3 16 A. K. MONGA & s. L. STANTON Table 3. Pre- and post-injection urethral pressure parameters. Parametric data are given as mean (SD) and nonparametric by median (range). L-P = length to peak pressure; MUCP = maxumum urethral closure pressure; FUL = functional urethral length. Cure Fail Pre Post Pre Post Total profile length (mm) 3.6 (6.1) 34.1 (5.2)*t 28.4 (7.3) 27.9 (9.7) Functional urethral length (mm) 25 (6.2) 28.4 (6)' 22 (7.5) 24.4 (9.3)* L-P (mm) 14.6 (8-21) 15.2 (7-22) 13.5 (2-27) 15.8 (3-35)* MUCP (cmh,o) 3.7 (16) 24.4 (18) 18.9 (9.4) 23.2 (13.2)t Area to peak pressure (mm.cmhzo) 228 (57-5) 185 (37-547) 167 (2-554) 222 (12432)* Area at 1/4 FUL (mm.cmh, ) 55 (347) 88 (8-96)* 55 (2-7) 56 (443) Stress FUL (mm) 13.8 (-28) 17.8 (4-35)*t 9.6 (-28) 14.2 (-31) Stress L-P (mm) 6.9 (-16) 9.7 (2-23)* 4.8 (-13) 7.3 (-16)* Stress MUCP (cmh,o) 17.6 (24) 22.4 (-7)*t 16.7 (-34) 22 (-32)' Pressure transmission ratio ("h) 1 st quarter 88 (24) 19 (2)*t 98 (35.2) 11 (2.5) 2nd quarter 94 (27) 12 (14) 83 (2.9) 12 (21.8)* 3rd quarter 79 (2) 91 (17) 71 (22.1) 85 (17.6) 4th quarter 66 (19) 78 (18) 69 (19.5) 74 (17.6) *P <.5 denotes significant change between pre- and post-injection data (paired t test for parametric and Wilcoxon's signed rank for nonparametric data). tp <.5 denotes significant differences in mean change when comparing cured with failed patients (unpaired t test after log transformation). injection in relation to objective outcome at 12 months. In the cured women there were significant increases in total profile length, rest and stress functional urethral length, stress under the first quarter of functional urethral length, maximum urethral closure pressure and pressure transmission ratio in the first quarter of urethral length. Of all the listed rest and stress urethral pressure profile parameters, the only pre-operative variable that significantly affected outcome at 12 months was mean resting maximum urethral closure pressure (Group 1, 31 cmh,o vs Group 2, 19 cmh,o; P =.4); however, no clear cutoff point could be identified. The mean increase or decrease in post treatment UPP variables in cured and failed treatments were compared using unpaired t tests. The increases in total profile length, stress maximum urethral closure pressure, stress functional urethral length, and pressure transmission ratio in the first quarter of urethral length were significantly greater in Group 1 (P <.5), and increases in rest maximum urethral and maximum urethral closure pressures and area under the rest profile were significantly greater in Group 2 (P <.2). DISCUSSION In addition to subjective assessment of outcome, objective measures are necessary to confirm cure and detect complications such as detrusor instability or voiding difficulty. The accepted objective urodynamic investigation is subtracted cystometry with or without video studies and we have used this to assess outcome. The short and long term reproducibility of standardised subtracted cystometry has been shown to be high2,21; however the sensitivity of detection of genuine stress incontinence is lower. Swift and Ostergard,, have demonstrated genuine stress incontinence in 59 of 65 patients with the symptom of stress incontinence during subtracted cystometry. The other six had negative cystometry and a positive cough stress test. The reproducibility of the one hour perineal pad test has been demonstrated by several investigator^^^^^^. Klarskov and Hald23 repeated a standardised one hour pad test in 19 women and found no significant difference in loss. To quantify urine loss and increase the sensitivity of detection of genuine stress incontinence we included a standard one hour pad test19 to assess outcome. Prediction We have examined the use of various factors as possible predictors of outcome. The severity of pretreatment urine loss and the values of cystometric measurements, such as peak flow rate or maximum voiding pressure, did not influence outcome after collagen injection. Although it is suggested that the presence of pre-injection detrusor instability has a deleterious effect on outcome25, it did not decrease cure of stress incontinence in this study. Bladder neck hypermobility is thought to decrease SUCC~SS~~ although no definition of hypermobility is proposed. Fifty-five (92%) of our women had undergone previous continence surgery and consequently had decreased bladder neck mobility demonstrated by an RCOG 1997 Br J Obstet Gynaecol 14,

4 excursion < 1 mm. However, cure rates are not reduced for the other five women with up to 2.5 cm movement. There was no demonstrable difference in cure or failure. It is quite surprising that a low resting maximum urethral closure pressure should adversely affect outcome as periurethral injections are recommended in those patients with well elevated bladder necks with stress incontinence due to intrinsic sphincter defi~iency~~ and consequently a low pressure urethra. However, this finding is consistent with other procedures. M~Guire~~ reported a 4 1 % failure rate for colposuspension if the maximum urethral URODYNAMICS AND CURE OF STRESS INCONTINENCE 161 there is an increased length and increased area to peak pressure, and a significant increase in pressure transmission ratio in the second quarter of the urethra, suggesting collagen is deposited more distally and therefore does not increase the functional urethral length or prevent bladder neck opening during episodes of stress. Our findings confirm that voiding difficulty (increased MVP and decreased PFR), mild detrusor instability or a mobile unsupported bladder neck (as opposed to a fixed and elevated bladder neck) are not contraindications to collagen injection. The closure pressure was < 2 cmh2; Sand et ~ 1 noted. ~ review ~ of continence surgery by Jarvis3 confirms that in 86 women undergoing colposuspension, a pre-operative maximum urethral closure pressure < 2 cmh,o was three times more likely to give an unsatisfactory outcome. Bowen et alz9 performed a case-controlled study with 2 1 patients in each group; of the successfully treated women 17 had a maximum urethral closure pressure > 2 cmh,o compared with five of the failures. These findings were confirmed by Wolf et al3: success rates fell from 91% to 75% if the maximum urethral closure pressure was that there is a failure rate of 6% to 55% for primary procedures in addition to complications and side effects. Jarvis acknowledges that no single operation should be offered to all women in all situations as a.first choice. The success of operations for urinary incontinence and their complications are only likely to be improved by understanding the urodynamic effects of each and being able to tailor the procedure to the urodynamic characteristics of the individual patient. < 2 cmh,o prior to colposuspension. A maximum urethral closure pressure cutoff of 2 cmh2 also predicts the success of the Stamey procedure Acknowledgement (P. Hilton, personal communication). In our series a We wish to thank the Medical and Clinical Affairs resting pretreatment maximum urethral closure Department, Bard Europe for providing Contigen@ pressure > 39 cmh,o was associated with success and financial support. We also wish to thank in all seven women; however, there was a marked Professor M. Bland, Department of Public Health overlap between success and failure at lower closure Sciences, St Georges Hospital Medical School for his pressures. No other pre-injection urethral pressure invaluable statistical advice. variable appears to be able to predict outcome. Mechanism Residual urine, peak flow rate and maximum voiding pressure remained unchanged, contrary to evidence from other studies that collagen acts by obstruction In successful cases the increased area and pressure transmission ratio in the first quarter of functional urethral length suggests that collagen placement occurs at the bladder neck or proximal urethra preventing bladder neck opening under stress. The cephalad elongation of the urethra accounts for the increase in pressure transmission ratio in the first quarter of urethral length. Increase in pressure transmission ratio in combination with a higher resting maximum urethral closure pressure is associated with greater success rates. The increase in stress functional urethral length and the resulting increase in pressure transmission provides a second mechanism. Long term cure is probably due to maintenance of this increased pressure transmission. The changes in failed cases are quite different: References Stanton SL, Cardozo L, Williams J, Ritchie D, Allan V. Clinical and urodynamic features of failed incontinence surgery in the female. Obstet Gynecoll978; 51: Pow-Sang J, Lockhart J, Suarez A, Lansman H, Politano V. Female urinary incontinence: preoperative selection, surgical complications andresults. J Uroll986; 136: Wilkie D, Barzilai M, Stanton SL. Combined urethral sphincter incompetence and detrusor instability: does colposuspension help? Proceedings of the 16th Annual Meeting of the International Continence Society; Boston, Massachussetts, USA; 1986: Lockhart J, Vorstman B, Politano V. Anti incontinence surgery in females with detrusor instability. Neurourol Urodymti 1984; 3: Bhatia NN, Bergman A. 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