Neurourology and Urodynamics 34:50–54 (2015)
The Impact of Tension-Free Vaginal Tape on the Urethral Closure Function: Mechanism of Action Marie-Louise Saaby,* Niels Klarskov, and Gunnar Lose Department of Obstetrics and Gynecology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark Aim: To investigate if the tension-free vaginal tape (TVT) works by increasing the abdominal to urethral pressure impact ratio (APIR). Methods: Twenty one women with urodynamically proven stress urinary incontinence (SUI) were assessed by ICIQ-SF, pad-weighing test, incontinence diary and Urethral Pressure Reflectometry (UPR) before and after TVT. UPR was conducted during resting and increased intra-abdominal pressure (PAbd) by straining. Related values of PAbd and urethral opening pressure (Po) were plotted into an abdomino-urethral pressuregram. Linear regression of the values was conducted, and the slope of the line was found. The slope expresses the ratio of pressure increase in the urethra compared to the pressure increase in the abdomen and was called APIR. Results: The urethral opening pressure at rest (Po-rest) was unchanged after TVT, while APIR increased in all women (from 0.7 to 1.4, P < 0.0001). Conclusions: The TVT seems to strengthen the urethral closure function by increasing the APIR while Po-rest is unchanged regardless of the type of pre-operative dysfunction. This confirms the theory of TVT’s mechanism of action being mid-urethral support. Neurourol. Urodynam. 34:50–54, 2015. # 2013 Wiley Periodicals, Inc. Key words: APIR; PTR; SUI; TVT; UPR; closure function; closure mechanism; intra-abdominal pressure increase; pressure reflectometry; strain; tension-free vaginal tape; urethra; urinary incontinence; urodynamics INTRODUCTION
Stress urinary incontinence (SUI) occurs when the bladder pressure exceeds the urethral pressure on effort or exertion or on sneezing or coughing1 and depends on the efficiency of the urethral closure function and the pressure to which it is subjected.2 The urethral closure mechanism has been described anatomically consisting of a sphincteric unit and a support system.3 Urodynamically, the urethral closure function has been characterized by means of the permanent and the adjunctive closure forces.4 The permanent closure forces, primarily generated by the urethral sphincteric unit, can be assessed by the resting urethral opening pressure (Po-rest).4,5 The adjunctive closure forces superposed during intra-abdominal pressure increase, suggested primarily to be generated by the support system, has previously been measured as the ‘‘pressure transmission ratio (PTR).’’6–10 However, the PTR has very poor reproducibility and has never shown to be clinical relevant.11 The term is, in addition, confusing as pressure does not transmit.12 Therefore a new method for measuring the adjunctive closure forces has been developed. The method is called the abdominal to urethral pressure impact ratio (APIR). APIR expresses the ratio of pressure increase in the high pressure zone of urethra (HPZ) compared to the increase in intra-abdominal pressure5 and is measured with Urethral Pressure Reflectometry (UPR). The dysfunctional basis of SUI is suggested principally to be urethral sphincter deficiency and/or urethral hypermobility (due to deterioration of urethral support).11 Correspondingly, recent results have shown that Po-rest and APIR differ statistically significantly between SUI and continent women, and the urethral closure function can be insufficient due to deteriorated Po-rest and/or APIR.5 The impact of TVT on the urethral opening pressure during intra-abdominal pressure increase is ambiguous. MUCP has shown to be unchanged after TVT,7–9,13 hence the empirically shown effect of TVT might be caused by increased APIR #
2013 Wiley Periodicals, Inc.
subsequent to the urethral support, which could explain the mechanism of action behind the procedure. The aim of this study was to investigate if the TVT works by increasing the APIR. MATERIALS AND METHODS
Women with bothersome urodynamically proven SUI and scheduled for TVT were consecutively recruited via the outpatient clinic. Subjects were excluded if they had pelvic organ prolapse (POP) stage 2 or greater, previous surgery for SUI or POP, hysterectomy within the last year before enrolment, detrusor overactivity on filling cystometry, intake of anti-muscarinic drugs within the last 3 months, overt neurological diseases, signs of lower urinary tract infection on urine dipstick, or were pregnant. In addition to the UPR measurements, the pre- and postoperative assessment included a comprehensive medical history, the International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF), pelvic examination, uroflowmetry, measurement of post-void residual urine volume (PVR), cough stress test, urine analysis, pad-weighing test (2 24 hr), bladder diary (2 days), incontinence episode diary (7 days), and 3D and 4D ultrasound. Cystometry was performed at enrolment if not previously conducted within the 3 months before enrolment.
Heinz Koelbl led the peer-review process as the Associate Editor responsible for the paper. Conflict of interest: Gunnar Lose—Research cooperation with Coloplast under grant from Advanced Technology Foundation. Correspondence to: Marie-Louise Saaby, Department of Obstetrics and Gynecology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark. E-mail: [email protected] Received 27 June 2013; Accepted 25 September 2013 Published online 8 November 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22513
Increased APIR After TVT Cough stress test (five forceful coughs) was carried out in the standing position after insertion of 150 ml of saline to the bladder via a catheter (10 F). Filling cystometry (Duet Logic, Mediwatch, Rugby, UK or MMS Solar Gold, MEQ, Enschede, The Netherlands) was undertaken using two 5 F transurethral catheters, one for filling the bladder and one for pressure measurements, and a fluid filled rectal catheter for measurement of abdominal pressure. With the patient seated, saline was infused at a medium filling rate (50 ml/min), and the diagnosis of urodynamic stress incontinence was based on the detection of urinary leakage during coughing in the absence of detrusor activity. The 2-day bladder diary included records of incontinence episodes, liquid intake, the time of micturitions and voided volumes. In the 7-day incontinence diary, the patient noted every incontinence episode in seven consecutive days. 3D and 4D perineal ultrasound (Voluson E8, GE Medical Systems, Zipf, Austria) was used as biofeedback to ensure straining without voluntary contraction of the pelvic floor muscles.
The UPR Measurements
The UPR equipment consists of a computer with an integrated pressure recorder which via a PVC tube is connected to a probe (containing an acoustic transmitter and a microphone), a 12 ml syringe and a polyurethane bag.14 The technique enables simultaneous measurement of pressure and cross-sectional area in the entire length of the urethra by use of the very thin and highly flexible polyurethane bag. It is reproducible,15 meets the requirements of investigation in a collapsible tube such as the urethra,16 and avoids the common artifacts encountered with conventional catheters. The urethral opening pressure can be obtained at a specific site of the urethra, for example the HPZ. The UPR enables measurement within 7 sec opposed to conventional techniques which require several minutes.14 This faster technique allows assessment during resting, squeezing and increased intra-abdominal pressure by straining (bearing down).14 With the woman supine the polyurethane bag was inserted in the urethra as earlier described.15 Air was injected into the bag by the syringe thereby increasing the pressure and distending the bag. The cross-sectional area within the bag, and thus the urethra, was measured continuously with acoustic reflectometry, and the pressure needed just to open the collapsed urethra, the opening pressure (Po),16 was obtained. We only evaluated measurements from the HPZ of the urethra, defined as the position in the urethra where the cross-sectional area was smallest. Measurements at rest. The woman was instructed to relax. The pressure in the polyurethane bag was raised from 0 cm H2O to 200 cm H2O within approximately 7 sec and the resting urethral opening pressure (Po-rest) was measured. Hereafter the pressure was decreased to 0 cm H2O.14 Measurements during increased intra-abdominal pressure. The woman was instructed to increase the intra-abdominal pressure by straining 10 times at different intensities and keep the pressure for 7 sec. At each strain the pressure in the bag was raised from 0 cm H2O to 200 cm H2O within 7 sec and the urethral opening pressure measured. Hereafter the pressure was decreased to 0 cm H2O. The abdominal pressure (PAbd) was simultaneously measured with an air filled catheter (T-dock, Wenonah, NJ) in the rectum. Neurourology and Urodynamics DOI 10.1002/nau
51
The related values of Po and PAbd at the 10 different abdominal pressures were recorded and plotted into a HPZ abdomino-urethral pressuregram (Fig. 1). Linear regression of the values was conducted, and the slope of the line was found.2 The slope expresses the APIR.5 An APIR of 1 means that the pressure in the HPZ of the urethra increases exactly as much as the increase in the abdominal pressure. An APIR 1 means that the pressure in the HPZ increases more than the abdominal pressure and in this case the subject will not be stress incontinent even at very high abdominal pressures.5 The TVT procedure (Gynecare, Division of Ethicon and Johnson & Johnson, Somerville, NJ) was carried out under local anesthesia with no concomitant surgical procedures using the technique described by Ulmsten et al.17 Subjective ‘‘Cure’’ was defined as no reported stress incontinence on ICIQ-SF, ‘‘improvement’’ as 50% decrease in postoperative ICIQ-SF score, and ‘‘failure’’ as 50% decrease in postoperative score. Objective ‘‘Cure’’ was defined as negative stress test and
The Impact of Tension-Free Vaginal Tape on the Urethral Closure Function: Mechanism of Action Marie-Louise Saaby,* Niels Klarskov, and Gunnar Lose Department of Obstetrics and Gynecology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark Aim: To investigate if the tension-free vaginal tape (TVT) works by increasing the abdominal to urethral pressure impact ratio (APIR). Methods: Twenty one women with urodynamically proven stress urinary incontinence (SUI) were assessed by ICIQ-SF, pad-weighing test, incontinence diary and Urethral Pressure Reflectometry (UPR) before and after TVT. UPR was conducted during resting and increased intra-abdominal pressure (PAbd) by straining. Related values of PAbd and urethral opening pressure (Po) were plotted into an abdomino-urethral pressuregram. Linear regression of the values was conducted, and the slope of the line was found. The slope expresses the ratio of pressure increase in the urethra compared to the pressure increase in the abdomen and was called APIR. Results: The urethral opening pressure at rest (Po-rest) was unchanged after TVT, while APIR increased in all women (from 0.7 to 1.4, P < 0.0001). Conclusions: The TVT seems to strengthen the urethral closure function by increasing the APIR while Po-rest is unchanged regardless of the type of pre-operative dysfunction. This confirms the theory of TVT’s mechanism of action being mid-urethral support. Neurourol. Urodynam. 34:50–54, 2015. # 2013 Wiley Periodicals, Inc. Key words: APIR; PTR; SUI; TVT; UPR; closure function; closure mechanism; intra-abdominal pressure increase; pressure reflectometry; strain; tension-free vaginal tape; urethra; urinary incontinence; urodynamics INTRODUCTION
Stress urinary incontinence (SUI) occurs when the bladder pressure exceeds the urethral pressure on effort or exertion or on sneezing or coughing1 and depends on the efficiency of the urethral closure function and the pressure to which it is subjected.2 The urethral closure mechanism has been described anatomically consisting of a sphincteric unit and a support system.3 Urodynamically, the urethral closure function has been characterized by means of the permanent and the adjunctive closure forces.4 The permanent closure forces, primarily generated by the urethral sphincteric unit, can be assessed by the resting urethral opening pressure (Po-rest).4,5 The adjunctive closure forces superposed during intra-abdominal pressure increase, suggested primarily to be generated by the support system, has previously been measured as the ‘‘pressure transmission ratio (PTR).’’6–10 However, the PTR has very poor reproducibility and has never shown to be clinical relevant.11 The term is, in addition, confusing as pressure does not transmit.12 Therefore a new method for measuring the adjunctive closure forces has been developed. The method is called the abdominal to urethral pressure impact ratio (APIR). APIR expresses the ratio of pressure increase in the high pressure zone of urethra (HPZ) compared to the increase in intra-abdominal pressure5 and is measured with Urethral Pressure Reflectometry (UPR). The dysfunctional basis of SUI is suggested principally to be urethral sphincter deficiency and/or urethral hypermobility (due to deterioration of urethral support).11 Correspondingly, recent results have shown that Po-rest and APIR differ statistically significantly between SUI and continent women, and the urethral closure function can be insufficient due to deteriorated Po-rest and/or APIR.5 The impact of TVT on the urethral opening pressure during intra-abdominal pressure increase is ambiguous. MUCP has shown to be unchanged after TVT,7–9,13 hence the empirically shown effect of TVT might be caused by increased APIR #
2013 Wiley Periodicals, Inc.
subsequent to the urethral support, which could explain the mechanism of action behind the procedure. The aim of this study was to investigate if the TVT works by increasing the APIR. MATERIALS AND METHODS
Women with bothersome urodynamically proven SUI and scheduled for TVT were consecutively recruited via the outpatient clinic. Subjects were excluded if they had pelvic organ prolapse (POP) stage 2 or greater, previous surgery for SUI or POP, hysterectomy within the last year before enrolment, detrusor overactivity on filling cystometry, intake of anti-muscarinic drugs within the last 3 months, overt neurological diseases, signs of lower urinary tract infection on urine dipstick, or were pregnant. In addition to the UPR measurements, the pre- and postoperative assessment included a comprehensive medical history, the International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF), pelvic examination, uroflowmetry, measurement of post-void residual urine volume (PVR), cough stress test, urine analysis, pad-weighing test (2 24 hr), bladder diary (2 days), incontinence episode diary (7 days), and 3D and 4D ultrasound. Cystometry was performed at enrolment if not previously conducted within the 3 months before enrolment.
Heinz Koelbl led the peer-review process as the Associate Editor responsible for the paper. Conflict of interest: Gunnar Lose—Research cooperation with Coloplast under grant from Advanced Technology Foundation. Correspondence to: Marie-Louise Saaby, Department of Obstetrics and Gynecology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark. E-mail: [email protected] Received 27 June 2013; Accepted 25 September 2013 Published online 8 November 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22513
Increased APIR After TVT Cough stress test (five forceful coughs) was carried out in the standing position after insertion of 150 ml of saline to the bladder via a catheter (10 F). Filling cystometry (Duet Logic, Mediwatch, Rugby, UK or MMS Solar Gold, MEQ, Enschede, The Netherlands) was undertaken using two 5 F transurethral catheters, one for filling the bladder and one for pressure measurements, and a fluid filled rectal catheter for measurement of abdominal pressure. With the patient seated, saline was infused at a medium filling rate (50 ml/min), and the diagnosis of urodynamic stress incontinence was based on the detection of urinary leakage during coughing in the absence of detrusor activity. The 2-day bladder diary included records of incontinence episodes, liquid intake, the time of micturitions and voided volumes. In the 7-day incontinence diary, the patient noted every incontinence episode in seven consecutive days. 3D and 4D perineal ultrasound (Voluson E8, GE Medical Systems, Zipf, Austria) was used as biofeedback to ensure straining without voluntary contraction of the pelvic floor muscles.
The UPR Measurements
The UPR equipment consists of a computer with an integrated pressure recorder which via a PVC tube is connected to a probe (containing an acoustic transmitter and a microphone), a 12 ml syringe and a polyurethane bag.14 The technique enables simultaneous measurement of pressure and cross-sectional area in the entire length of the urethra by use of the very thin and highly flexible polyurethane bag. It is reproducible,15 meets the requirements of investigation in a collapsible tube such as the urethra,16 and avoids the common artifacts encountered with conventional catheters. The urethral opening pressure can be obtained at a specific site of the urethra, for example the HPZ. The UPR enables measurement within 7 sec opposed to conventional techniques which require several minutes.14 This faster technique allows assessment during resting, squeezing and increased intra-abdominal pressure by straining (bearing down).14 With the woman supine the polyurethane bag was inserted in the urethra as earlier described.15 Air was injected into the bag by the syringe thereby increasing the pressure and distending the bag. The cross-sectional area within the bag, and thus the urethra, was measured continuously with acoustic reflectometry, and the pressure needed just to open the collapsed urethra, the opening pressure (Po),16 was obtained. We only evaluated measurements from the HPZ of the urethra, defined as the position in the urethra where the cross-sectional area was smallest. Measurements at rest. The woman was instructed to relax. The pressure in the polyurethane bag was raised from 0 cm H2O to 200 cm H2O within approximately 7 sec and the resting urethral opening pressure (Po-rest) was measured. Hereafter the pressure was decreased to 0 cm H2O.14 Measurements during increased intra-abdominal pressure. The woman was instructed to increase the intra-abdominal pressure by straining 10 times at different intensities and keep the pressure for 7 sec. At each strain the pressure in the bag was raised from 0 cm H2O to 200 cm H2O within 7 sec and the urethral opening pressure measured. Hereafter the pressure was decreased to 0 cm H2O. The abdominal pressure (PAbd) was simultaneously measured with an air filled catheter (T-dock, Wenonah, NJ) in the rectum. Neurourology and Urodynamics DOI 10.1002/nau
51
The related values of Po and PAbd at the 10 different abdominal pressures were recorded and plotted into a HPZ abdomino-urethral pressuregram (Fig. 1). Linear regression of the values was conducted, and the slope of the line was found.2 The slope expresses the APIR.5 An APIR of 1 means that the pressure in the HPZ of the urethra increases exactly as much as the increase in the abdominal pressure. An APIR 1 means that the pressure in the HPZ increases more than the abdominal pressure and in this case the subject will not be stress incontinent even at very high abdominal pressures.5 The TVT procedure (Gynecare, Division of Ethicon and Johnson & Johnson, Somerville, NJ) was carried out under local anesthesia with no concomitant surgical procedures using the technique described by Ulmsten et al.17 Subjective ‘‘Cure’’ was defined as no reported stress incontinence on ICIQ-SF, ‘‘improvement’’ as 50% decrease in postoperative ICIQ-SF score, and ‘‘failure’’ as 50% decrease in postoperative score. Objective ‘‘Cure’’ was defined as negative stress test and
![[Intravesical migration of a sub-urethral tension-free vaginal tape (TVT) sling: about a case and review of the literature].](/assets/img/hold.png)
