Neurourology and Urodynamics 33:587–590 (2014)
Do We Need Better Methods of Assessing Urethral Function? ICI-RS 2013 Andrew Gammie,1* Ruud Bosch,2 Jens Chr. Djurhuus,3 Ing Goping,4 and Ruth Kirschner-Hermanns5 1
Bristol Urological Institute, Southmead Hospital, Bristol, United Kingdom 2 Department of Urology, UMC Utrecht, Utrecht, The Netherlands 3 Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark 4 Laborie Medical Systems, Mississauga, Ontario, Canada 5 Neuro-Urology University Clinic, Rheinische Friedrich-Wilhelms University, Bonn, Germany Aims: To assess whether current methods of urethral function assessment are sufficient for clinical requirement. Methods: A summary of the debate held at the 2013 meeting of the International Consultation on Incontinence Research Society, with subsequent analysis by the authors. Results: All reported methods of assessment were reviewed and a summary of reported efficacy and clinical application for each is given. Every method of assessment has limitations as to its use, and in some cases the methods have yet to be proved reliable. Conclusions: A gap exists between clinical requirements and the capacity of current urethral function assessments to assist diagnosis. Recommendations are therefore made for future research topics. Neurourol. Urodynam. 33:587–590, 2014. # 2014 Wiley Periodicals, Inc. Key words: assessment; measurement; pressure; urethra
INTRODUCTION AND METHODS
Good urethral function is essential for normal urinary continence and voiding. However, discussions over the years have questioned the usefulness and relevance of the different methods used in assessment.1 The issues concerning these methods were the subject of a debate at the 4th International Consultation on Incontinence Research Society (ICI-RS), held in Bristol, UK on 5th–7th June 2013. The discussions, summarized in this paper, were required to focus on the relevance of the topic to patients, for which reason the clinical issues relating to urethral function were considered first. A review was made of techniques of urethral function assessment described in ICI publications and also International Continence Society (ICS) standards and past scientific meetings. An analysis was made of any mismatch between clinical issues and the capability of assessment methods in order to highlight areas requiring further research. CLINICAL REASONS FOR MEASURING URETHRAL FUNCTION
The urethra should maintain urinary continence during storage and offer a low resistance to flow during voiding. Measurement of urethral function assesses the capacity of the urethra to achieve this respective closure and opening. A good quality measurement gives an accurate picture of physiological reality. The main reasons for measuring urethral function can be addressed according to patient group as follows:
Women
Defining intrinsic sphincter deficiency (ISD): There is evidence from prospective cohort studies that women with ISD have a worse outcome from surgery for stress incontinence.2,3 The ICI review points out that there is some evidence that women with ISD have worse results after colposuspension than after a fascial sling procedure, or after TOT than after TVT.2 A randomized trial concluded that lowest quartile maximum urethral pressure doubles the likelihood of experiencing incontinence after mid urethral sling surgery.4 Investigating unexplained incontinence: For example, we suggest urethral pressure variations that are not detected during standard urodynamics. Assessing idiopathic urinary retention in young women: For example, ‘‘Fowler’s syndrome’’, which is characterized in part by sphincter overactivity.5 Assessing recurrent or persistent stress incontinence after surgery: Urethral function studies were used in a prospective cohort study and in a group comparison study to define the mechanisms of failure.6,7
Christopher Chapple led the peer-review process as the Associate Editor responsible for the paper. Conflict of interest: none. Correspondence to: Andrew Gammie, Bristol Urological Institute, Southmead Hospital, Bristol BS10 5NB, United Kingdom. E-mail: [email protected] Received 19 December 2013; Accepted 14 March 2014 Published online 16 May 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22606
#
2014 Wiley Periodicals, Inc.
588
Gammie et al.
Men
Estimation of the size, and the likely obstructive effect, of the prostate: There is evidence from well documented case series that men who are more obstructed urodynamically have a better outcome after TURP than less or unobstructed men.8,9 Though pressure-flow studies will be the diagnostic test for this, a retrospective analysis suggested that urethral pressure may be a guide in the case of men unable to void.10 Estimation of need for repeat TURP: Residual prostate tissue can be seen as a raised pressure area proximal to the pressure peak due to the urethral sphincter.11 We conclude that this may be used if pressure-flow studies are for some reason inadequate. Assessing men being considered for artificial sphincter or male sling: There is evidence from several case series that men with sphincter damage alone have better outcomes after artificial sphincter or particularly male sling implantation than those with concomitant severe detrusor overactivity and/or poor compliance.12 Assessing continence mechanisms after radical prostatectomy (RP): To determine whether there is sufficient residual sphincter function to start a successful pelvic floor muscle exercise program.13 To determine the best time after RP to decide whether to treat incontinence directly or still continue with a conservative watchful waiting procedure.14 To determine whether the main problem is of sphincteric origin or not.14 Neurological
Assessing patients being considered for artificial sphincter: To determine if the incontinence is due to sphincteric weakness or whether other factors are involved.
Assessing the causes of urinary retention—‘‘urethral voiding dysfunction’’: For example, detrusor sphincter dyssynergia (DSD) or non-relaxing urethral sphincter obstruction.15 One recent study found that multiple sensor measurement of urethral pressure was better able than a single measurement to characterize DSD.16 Assessing urethral function in patients with different central and peripheral neurological lesions To identify deviation from normal function due to neuropathy.15
The ICI recommendations on urethral pressure measurements are necessarily quite vague. The general recommendation is that urodynamic testing be used to evaluate a person’s lower urinary tract function where the results are likely to alter patient management and, in general, for confirmation of diagnosis prior to invasive treatments. There
Neurourology and Urodynamics DOI 10.1002/nau
is level 1 evidence that such urodynamic testing has to include at least one complete and representative filling-voiding-postvoiding cycle with relevant pressures and flowmetry. The ICI further suggests that auxiliary assessments of urethral function can complete or augment the value of urodynamic testing for specific indications,17 for example, after radical prostatectomy.14
TECHNIQUES REPORTED AND THEIR LIMITATIONS
To carry out these assessments, a number of different techniques have been reported, all of which have been noted to suffer from certain limitations. These are summarized as follows. Fluid perfusion (UPPf)18 Although, originally specified with a single lumen catheter with two side holes, in order to minimize the effect of catheter orientation, it is known that some studies have used other catheters. The introduction of a catheter distends the urethra, and the measurement is affected by urine flow and perfusion rate.19 Lack of standardization of practice has been raised as an issue.20 Air filled balloon (UPPa)21 This too distends the urethra, and the values obtained have been shown to be higher than UPPf22 and UPPm.23 Microtip catheter (UPPm) Since the sensor face is on only one side of the catheter, the readings obtained are sensitive to the catheter orientation. Being a solid, and in mechanical contact with the urethral wall, the sensor does not measure true intra-luminal fluid pressure, despite that being the definition of urethral pressure,19 but a compound of directional forces. Urethral pressure reflectometry (UPR)24 The 5th ICI reported that the relevance of this technique still needs to be demonstrated.1 Developments are ongoing and further studies are needed. Urethral retro-resistance pressure (URRP)25 The 5th ICI ‘‘committee recommends that URRP measurements are not used as an alternative to , measurements made with conventional equipment to diagnose.’’1 Leak point pressure (abdominal/valsalva) (ALPP/VLPP)26 The voluntary raising of intra-abdominal pressure is often used to assess the conditions resulting in urine leakage. However, accurate maintenance of pressure is difficult and the test assumes there are no geometrical changes in urethra. The presence of catheter is known to affect leakage and the authors of a recent review consider there is no consensus over a standard procedure.13 In addition, the same authors do not recommend this test for use in pre-operative assessment of urethral sphincter function for patients awaiting radical prostatectomy.13
ICIRS Urethral Function Assessment Leak point pressure (detrusor) (DLPP)26 This is defined as detrusor pressure at which leakage occurs in the absence of an increase in abdominal pressure or a detrusor contraction. There is, however, no consensus on standard use.26 Urethral pressure variations (sometimes referred to as ‘‘urethral instability’’)27 Though not strictly a different measurement technique, the association of changes in urethral pressure and detrusor overactivity has attracted renewed interest. There is still debate on whether certain urethral pressure variations should be regarded as physiological or pathophysiological. The prevalence of these variations stated in the literature varies, due to the use of different definitions, together with inappropriate urethral pressure recordings.28 Thus, the aetiology and neurophysiological linkages of these variations are still unknown.29 Urethral mobility30,31 Several methods of assessing the movement of the urethra during physiological events have been reported. However, ‘‘urethral hypermobility did not appear to have an independent effect on the frequency or severity of incontinence.’’32 Even so, there may be value in further investigation since one study reported that ‘‘the Sensor-QTM and Qtip test showed a higher inter-observer reliability, etc., compared to ultrasounds.’’31 It has been suggested that the decrease of MUCP during stress profile testing could be related to urethral hypermobility.33 Urethral sphincter EMG34 This is measured using a concentric needle electrode and is therefore highly invasive. Normal values are unknown and pelvic floor muscles can obscure the signal. MRI/X-ray/ultrasound imaging Advances in imaging techniques show promise for the assessment of urethral function and mobility, but further trials of the methods are required.13 Urethral electrical conductance35 The conduction of electricity by urine in the urethra has been shown to be of little diagnostic value, but can be used as a sensitive measurement of leakage.36 Fluid bridge37 A study using a commercial device based on a modified fluid bridge test was found to be ‘‘unreliable in diagnosing genuine stress incontinence.’’38 It is clear that the severe limitations noted above confound proper assessment of a fundamental aspect of urinary continence. Where urethral function is measured by these methods, it produces results that do not accurately reflect physiology outside of the test. There is thus a considerable gap between the symptomatic realities we need to address in practice, and the variables that our current tests can assess. In addition, the lack of standard practice or normal values in UPPa, UPR, URRP, LPP, and urethral pressure variations makes study comparisons and trial design difficult. Neurourology and Urodynamics DOI 10.1002/nau
589
RECOMMENDATIONS FOR RESEARCH
It is recommended that developments be encouraged in the areas listed below, since either the currently used measurement changes the physiology measured or standard values or methods have not been developed. The most recent study13 analyzing the evidence for useful clinical information obtained from urethral function tests reviewed the prognostic value specific to radical prostatectomy of five methods, namely UPP, MRI, sphincter EMG, perfusion sphincterometry, and leak point pressure tests. Further wellconducted trials were recommended for the first three methods. The review carried out in this paper leads to the following recommendations for research, with potential study questions suggested.
Combining different assessment methods and anatomical
understanding to give a clearer multifactorial picture. Do combined results from a package of dynamic tests provide complementary and more precise information on urethral function? Urethral pressure reflectometry. This promising technology is still under development, so its relevance is yet to be demonstrated. The development of normal values and randomized trials will assist in the application of the measurements taken. Standardizing the measurement of VLPP and DLPP. Can methods of maintaining constant pressure and definition of the levels of pressure required enhance diagnostic assessment? Measurement with thinner catheters. Do the obstructive and irritative effects of catheters currently used produce clinically significant inaccuracy that could be avoided with smaller catheters? Understanding age-related changes in urethral function. Can the structural changes in the urethra be typified by age group and hormonal status, thus improve measurement specificity and patient selection for treatment through gaining more accurate age-specific normal values? Assessing different patterns of detrusor overactivity. Are there physiological patterns and pathological drops of urethral pressures following or preceding detrusor overactivity?39 Can the disappearance of urethral pressure variations be a predictor for successful treatment with sacral neuromodulation?40
CONCLUSION
Urethral function assessment does need to improve, particularly for improving prediction of outcomes for better informed consent before surgery. Study questions are proposed to enable such improvements. For many assessment methods, better standardization of technique is required. REFERENCES 1. Rosier PFWM, Kuo HC, De Genaro M, et al. Ch. 6. In: Abrams P, Cardozo L, Khoury S, et al., editors. Incontinence. 5th edition. Paris: ICUD-EAU; 2013. 436– 7, 443–4. 2. Dmochowski R, Athanasiou S, Reid F, et al. Surgery for urinary incontinence in women. In: Abrams P, Cardozo L, Khoury S, et al., editors. Incontinence. 5th edition. Paris: ICUD-EAU; 2013. 1307–76.
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Gammie et al.
3. Schierlitz L, Dwyer PL, Rosamilia A, et al. Effectiveness of tension-free vaginal tape compared with transobturator tape in women with stress urinary incontinence and intrinsic sphincter deficiency a randomized controlled trial. Obstet Gynecol 2008;112:1253–61. 4. Nager CW, Sirls L, Litman HJ, et al. Urinary incontinence treatment network. baseline urodynamic predictors of treatment failure 1 year after mid urethral sling surgery. J Urol 2011;186:597–603. 5. De Ridder D, Ost D, Bruyninckx F. The presence of Fowler’s syndrome predicts successful long-term outcome of sacral nerve stimulation in women with urinary retention. Eur Urol 2007;51:229–33. 6. Athanassopoulos A, Melekos MD, Speakman M, et al. Stamey endoscopic vesical neck suspension in female urinary stress incontinence: results and changes in various urodynamic parameters. Int Urol Nephrol 1994;26:293–9. 7. Bump RC, Fantl JA, Hurt WG. Dynamic urethral pressure profilometry pressure transmission ratio determinations after continence surgery: Understanding the mechanism of success, failure, and complications. Obstet Gynecol 1988;72:870–4. 8. Javl e P, Jenkins SA, Machin DG, et al. Grading of benign prostatic obstruction can predict the outcome of transurethral prostatectomy. J Urol 1998;160:1713–7. 9. Rodrigues P, Lucon AM, Freire GC, et al. Urodynamic pressure flow studies can predict the clinical outcome after transurethral prostatic resection. J Urol 2001;165:499–502. 10. Fang Q, Song B, Li W, et al. Role of UPP in evaluating bladder outlet obstruction due to benign prostatic enlargement. Neurourol Urodyn 2007;26: 842–6. 11. Abrams P. Chapter 5, urodynamics in clinical practice. In: Urodynamics. 3rd edition. Springer-Verlag London Ltd.; 2006. 164–5. 12. Herschorn S, Bruschini H, Comiter C, et al. Surgical treatment of urinary incontinence in men. In: Abrams P, Cardozo L, Khoury S, et al., editors. Incontinence. Paris: ICUD-EAU; 2013. 1229–1305. 13. Dubbelman YD, Bosch JL. Urethral sphincter function before and after radical prostatectomy: Systematic review of the prognostic value of various assessment techniques. Neurourol Urodyn 2013;32:957–63. 14. Bentzon DN, Graugaard-Jensen C, Borre M. Urethral pressure profile 6 months after radical prostatectomy may be diagnostic of sphincteric incontinence: Preliminary data after 12 months’ follow-up. Scand J Urol Nephrol 2009; 43:114–8. 15. Amarenco G, Ismael SS, Soler JM. The dyssynergic sphincter. In: Corcos J, Schick E, editors. The urinary sphincter. New York: Marcel Dekker Inc.; 2001. 223–30. 16. Bloch F, Pichon B, Bonnet AM, et al. Urodynamic analysis in multiple system atrophy: Characterisation of detrusor-sphincter dyssynergia. J Neurol 2010;257:1986–91. 17. Rosier PFWM, Kuo HC, De Genaro M, et al. Ch. 6. In: Abrams P, Cardozo L, Khoury S, et al., editors. Incontinence. 5th edition. Paris: 2013. 433. 18. Brown M, Wickham JEA. The urethral pressure profile. Br J Urol 1969;41:211– 7. 19. Lose G, Griffiths D, Hosker G. Standardisation of urethral pressure measurement: Report from the standardisation Sub-Committee of the International Continence Society. Neurourol Urodyn 2002;21:258–60. 20. Weber AM. Is urethral pressure profilometry a useful diagnostic test for stress urinary incontinence? Obstet Gynecol Surv 2001;56:720–35.
Neurourology and Urodynamics DOI 10.1002/nau
21. Pollak JT, Neimark M, Connor JT, et al. Air-charged and microtransducer urodynamic catheters in the evaluation of urethral function. Int Urogynecol J 2004;15:124. 22. McKinney TB, Goldstein H, Hessami S. Comparison of fiberoptic, microtip, water and air-charged pressure transducer catheters for the evaluation of urethral pressure profiles. Rome: Proc Int Uro-Gynecol Assoc; 2000. 23. Zehnder P, Roth B, Burkhard FC, et al. Air charged and microtip catheters cannot be used interchangeably for urethral pressure measurement: A prospective, single-blind, randomized trial. J Urol 2008;180:1013–7. 24. Klarskov N, Lose G. Urethral pressure reflectometry; a novel technique for simultaneous recording of pressure and cross-sectional area in the female urethra. Neurourol Urodyn 2007;26:254–261. 25. Slack M, Tracey M, Hunsicker K, et al. Urethral retro-resistance pressure: A new clinical measure of urethral function. Neurourol Urodyn 2004;23:656– 61. 26. Haylen BT, de Ridder D, Freeman RM, et al. An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint report on the terminology for female pelvic floor dysfunction. Neurourol Urodyn 2010; 29:4–20. 27. McGuire EJ. Experimental observations on the integration of bladder and urethral function. Invest Urol 1978;15:303–7. 28. Groenendijk PM, Heesakkers JPFA, Ouwerkerk TJ, et al. Urethral instability: Current pathophysiological concept, Urol Int 2009;83:125–33. 29. Gadjiev N, Brovkin S, Tabaza R, et al. Urethral sphincter instability—An important contributing factor in OAB patients? Neurourol Urodyn 2012;31:153. 30. Bergman A, McCarthy TA, Ballard CA, et al. Roleof the Q-tip test in evaluating stress urinary incontinence. J Reprod Med 1987;32:273. 31. Salvatore S, Serati M, Uccella S, et al. Inter-observer reliability of three different methods of measuring urethrovesical mobility. Int Urogynecol J 2008;19:1513–7. 32. Fleischmann N, Flisser A, Blaivas J, et al. Sphincteric urinary incontinence: Relationship of vesical leak point pressure, urethral mobility and severity of incontinence. J Urol 2003;169:999–1002. 33. Schick E, Tessier J, Bertrand PE, et al. Observations on the function of the female urethra: I: Relation between maximum urethral closure pressure at rest and urethral hypermobility. Neurourol Urodyn 2003;22:643–7. 34. Fowler CJ, Kirby RS. Electromyography of urethral sphincter in women with urinary retention. Lancet 1985;1:1455–7. 35. Plevnik S, Vrtacnik P, Janez J. Detection of fluid entry into the urethra by electrical impedance measurements. Clin Phys Physiol Meas 1983;4:309–13. 36. Mayne C, Hilton P. The distal urethral electrical conductance test: Standardisation of method and clinical reliability. Neurourol Urodyn 1988;7:55–60. 37. Sutherst JR, Brown MC. Detection of urethral incompetence in women using the fluid bridge test. Br J Urol 1980;52:138–42. 38. Myers DL, Scotti RJ. The usefulness of the Stress-Cath1 in the diagnosis of genuine stress incontinence. Int Urogynecol J 1992;3:284–87. 39. S€ orensen S. Urethral pressure and pressure variations in stress incontinent women and women with unstable detrusor. Neurourol Urodyn 1991;10:483– 92. ´ Nijeholt AAB, Urethral 40. Groenendijk PM, Heesakkers JPFA, Lycklama A instability and sacral nerve stimulation: A better parameter to predict the efficacy? J Urol 2007;178:568–72.
Do We Need Better Methods of Assessing Urethral Function? ICI-RS 2013 Andrew Gammie,1* Ruud Bosch,2 Jens Chr. Djurhuus,3 Ing Goping,4 and Ruth Kirschner-Hermanns5 1
Bristol Urological Institute, Southmead Hospital, Bristol, United Kingdom 2 Department of Urology, UMC Utrecht, Utrecht, The Netherlands 3 Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark 4 Laborie Medical Systems, Mississauga, Ontario, Canada 5 Neuro-Urology University Clinic, Rheinische Friedrich-Wilhelms University, Bonn, Germany Aims: To assess whether current methods of urethral function assessment are sufficient for clinical requirement. Methods: A summary of the debate held at the 2013 meeting of the International Consultation on Incontinence Research Society, with subsequent analysis by the authors. Results: All reported methods of assessment were reviewed and a summary of reported efficacy and clinical application for each is given. Every method of assessment has limitations as to its use, and in some cases the methods have yet to be proved reliable. Conclusions: A gap exists between clinical requirements and the capacity of current urethral function assessments to assist diagnosis. Recommendations are therefore made for future research topics. Neurourol. Urodynam. 33:587–590, 2014. # 2014 Wiley Periodicals, Inc. Key words: assessment; measurement; pressure; urethra
INTRODUCTION AND METHODS
Good urethral function is essential for normal urinary continence and voiding. However, discussions over the years have questioned the usefulness and relevance of the different methods used in assessment.1 The issues concerning these methods were the subject of a debate at the 4th International Consultation on Incontinence Research Society (ICI-RS), held in Bristol, UK on 5th–7th June 2013. The discussions, summarized in this paper, were required to focus on the relevance of the topic to patients, for which reason the clinical issues relating to urethral function were considered first. A review was made of techniques of urethral function assessment described in ICI publications and also International Continence Society (ICS) standards and past scientific meetings. An analysis was made of any mismatch between clinical issues and the capability of assessment methods in order to highlight areas requiring further research. CLINICAL REASONS FOR MEASURING URETHRAL FUNCTION
The urethra should maintain urinary continence during storage and offer a low resistance to flow during voiding. Measurement of urethral function assesses the capacity of the urethra to achieve this respective closure and opening. A good quality measurement gives an accurate picture of physiological reality. The main reasons for measuring urethral function can be addressed according to patient group as follows:
Women
Defining intrinsic sphincter deficiency (ISD): There is evidence from prospective cohort studies that women with ISD have a worse outcome from surgery for stress incontinence.2,3 The ICI review points out that there is some evidence that women with ISD have worse results after colposuspension than after a fascial sling procedure, or after TOT than after TVT.2 A randomized trial concluded that lowest quartile maximum urethral pressure doubles the likelihood of experiencing incontinence after mid urethral sling surgery.4 Investigating unexplained incontinence: For example, we suggest urethral pressure variations that are not detected during standard urodynamics. Assessing idiopathic urinary retention in young women: For example, ‘‘Fowler’s syndrome’’, which is characterized in part by sphincter overactivity.5 Assessing recurrent or persistent stress incontinence after surgery: Urethral function studies were used in a prospective cohort study and in a group comparison study to define the mechanisms of failure.6,7
Christopher Chapple led the peer-review process as the Associate Editor responsible for the paper. Conflict of interest: none. Correspondence to: Andrew Gammie, Bristol Urological Institute, Southmead Hospital, Bristol BS10 5NB, United Kingdom. E-mail: [email protected] Received 19 December 2013; Accepted 14 March 2014 Published online 16 May 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22606
#
2014 Wiley Periodicals, Inc.
588
Gammie et al.
Men
Estimation of the size, and the likely obstructive effect, of the prostate: There is evidence from well documented case series that men who are more obstructed urodynamically have a better outcome after TURP than less or unobstructed men.8,9 Though pressure-flow studies will be the diagnostic test for this, a retrospective analysis suggested that urethral pressure may be a guide in the case of men unable to void.10 Estimation of need for repeat TURP: Residual prostate tissue can be seen as a raised pressure area proximal to the pressure peak due to the urethral sphincter.11 We conclude that this may be used if pressure-flow studies are for some reason inadequate. Assessing men being considered for artificial sphincter or male sling: There is evidence from several case series that men with sphincter damage alone have better outcomes after artificial sphincter or particularly male sling implantation than those with concomitant severe detrusor overactivity and/or poor compliance.12 Assessing continence mechanisms after radical prostatectomy (RP): To determine whether there is sufficient residual sphincter function to start a successful pelvic floor muscle exercise program.13 To determine the best time after RP to decide whether to treat incontinence directly or still continue with a conservative watchful waiting procedure.14 To determine whether the main problem is of sphincteric origin or not.14 Neurological
Assessing patients being considered for artificial sphincter: To determine if the incontinence is due to sphincteric weakness or whether other factors are involved.
Assessing the causes of urinary retention—‘‘urethral voiding dysfunction’’: For example, detrusor sphincter dyssynergia (DSD) or non-relaxing urethral sphincter obstruction.15 One recent study found that multiple sensor measurement of urethral pressure was better able than a single measurement to characterize DSD.16 Assessing urethral function in patients with different central and peripheral neurological lesions To identify deviation from normal function due to neuropathy.15
The ICI recommendations on urethral pressure measurements are necessarily quite vague. The general recommendation is that urodynamic testing be used to evaluate a person’s lower urinary tract function where the results are likely to alter patient management and, in general, for confirmation of diagnosis prior to invasive treatments. There
Neurourology and Urodynamics DOI 10.1002/nau
is level 1 evidence that such urodynamic testing has to include at least one complete and representative filling-voiding-postvoiding cycle with relevant pressures and flowmetry. The ICI further suggests that auxiliary assessments of urethral function can complete or augment the value of urodynamic testing for specific indications,17 for example, after radical prostatectomy.14
TECHNIQUES REPORTED AND THEIR LIMITATIONS
To carry out these assessments, a number of different techniques have been reported, all of which have been noted to suffer from certain limitations. These are summarized as follows. Fluid perfusion (UPPf)18 Although, originally specified with a single lumen catheter with two side holes, in order to minimize the effect of catheter orientation, it is known that some studies have used other catheters. The introduction of a catheter distends the urethra, and the measurement is affected by urine flow and perfusion rate.19 Lack of standardization of practice has been raised as an issue.20 Air filled balloon (UPPa)21 This too distends the urethra, and the values obtained have been shown to be higher than UPPf22 and UPPm.23 Microtip catheter (UPPm) Since the sensor face is on only one side of the catheter, the readings obtained are sensitive to the catheter orientation. Being a solid, and in mechanical contact with the urethral wall, the sensor does not measure true intra-luminal fluid pressure, despite that being the definition of urethral pressure,19 but a compound of directional forces. Urethral pressure reflectometry (UPR)24 The 5th ICI reported that the relevance of this technique still needs to be demonstrated.1 Developments are ongoing and further studies are needed. Urethral retro-resistance pressure (URRP)25 The 5th ICI ‘‘committee recommends that URRP measurements are not used as an alternative to , measurements made with conventional equipment to diagnose.’’1 Leak point pressure (abdominal/valsalva) (ALPP/VLPP)26 The voluntary raising of intra-abdominal pressure is often used to assess the conditions resulting in urine leakage. However, accurate maintenance of pressure is difficult and the test assumes there are no geometrical changes in urethra. The presence of catheter is known to affect leakage and the authors of a recent review consider there is no consensus over a standard procedure.13 In addition, the same authors do not recommend this test for use in pre-operative assessment of urethral sphincter function for patients awaiting radical prostatectomy.13
ICIRS Urethral Function Assessment Leak point pressure (detrusor) (DLPP)26 This is defined as detrusor pressure at which leakage occurs in the absence of an increase in abdominal pressure or a detrusor contraction. There is, however, no consensus on standard use.26 Urethral pressure variations (sometimes referred to as ‘‘urethral instability’’)27 Though not strictly a different measurement technique, the association of changes in urethral pressure and detrusor overactivity has attracted renewed interest. There is still debate on whether certain urethral pressure variations should be regarded as physiological or pathophysiological. The prevalence of these variations stated in the literature varies, due to the use of different definitions, together with inappropriate urethral pressure recordings.28 Thus, the aetiology and neurophysiological linkages of these variations are still unknown.29 Urethral mobility30,31 Several methods of assessing the movement of the urethra during physiological events have been reported. However, ‘‘urethral hypermobility did not appear to have an independent effect on the frequency or severity of incontinence.’’32 Even so, there may be value in further investigation since one study reported that ‘‘the Sensor-QTM and Qtip test showed a higher inter-observer reliability, etc., compared to ultrasounds.’’31 It has been suggested that the decrease of MUCP during stress profile testing could be related to urethral hypermobility.33 Urethral sphincter EMG34 This is measured using a concentric needle electrode and is therefore highly invasive. Normal values are unknown and pelvic floor muscles can obscure the signal. MRI/X-ray/ultrasound imaging Advances in imaging techniques show promise for the assessment of urethral function and mobility, but further trials of the methods are required.13 Urethral electrical conductance35 The conduction of electricity by urine in the urethra has been shown to be of little diagnostic value, but can be used as a sensitive measurement of leakage.36 Fluid bridge37 A study using a commercial device based on a modified fluid bridge test was found to be ‘‘unreliable in diagnosing genuine stress incontinence.’’38 It is clear that the severe limitations noted above confound proper assessment of a fundamental aspect of urinary continence. Where urethral function is measured by these methods, it produces results that do not accurately reflect physiology outside of the test. There is thus a considerable gap between the symptomatic realities we need to address in practice, and the variables that our current tests can assess. In addition, the lack of standard practice or normal values in UPPa, UPR, URRP, LPP, and urethral pressure variations makes study comparisons and trial design difficult. Neurourology and Urodynamics DOI 10.1002/nau
589
RECOMMENDATIONS FOR RESEARCH
It is recommended that developments be encouraged in the areas listed below, since either the currently used measurement changes the physiology measured or standard values or methods have not been developed. The most recent study13 analyzing the evidence for useful clinical information obtained from urethral function tests reviewed the prognostic value specific to radical prostatectomy of five methods, namely UPP, MRI, sphincter EMG, perfusion sphincterometry, and leak point pressure tests. Further wellconducted trials were recommended for the first three methods. The review carried out in this paper leads to the following recommendations for research, with potential study questions suggested.
Combining different assessment methods and anatomical
understanding to give a clearer multifactorial picture. Do combined results from a package of dynamic tests provide complementary and more precise information on urethral function? Urethral pressure reflectometry. This promising technology is still under development, so its relevance is yet to be demonstrated. The development of normal values and randomized trials will assist in the application of the measurements taken. Standardizing the measurement of VLPP and DLPP. Can methods of maintaining constant pressure and definition of the levels of pressure required enhance diagnostic assessment? Measurement with thinner catheters. Do the obstructive and irritative effects of catheters currently used produce clinically significant inaccuracy that could be avoided with smaller catheters? Understanding age-related changes in urethral function. Can the structural changes in the urethra be typified by age group and hormonal status, thus improve measurement specificity and patient selection for treatment through gaining more accurate age-specific normal values? Assessing different patterns of detrusor overactivity. Are there physiological patterns and pathological drops of urethral pressures following or preceding detrusor overactivity?39 Can the disappearance of urethral pressure variations be a predictor for successful treatment with sacral neuromodulation?40
CONCLUSION
Urethral function assessment does need to improve, particularly for improving prediction of outcomes for better informed consent before surgery. Study questions are proposed to enable such improvements. For many assessment methods, better standardization of technique is required. REFERENCES 1. Rosier PFWM, Kuo HC, De Genaro M, et al. Ch. 6. In: Abrams P, Cardozo L, Khoury S, et al., editors. Incontinence. 5th edition. Paris: ICUD-EAU; 2013. 436– 7, 443–4. 2. Dmochowski R, Athanasiou S, Reid F, et al. Surgery for urinary incontinence in women. In: Abrams P, Cardozo L, Khoury S, et al., editors. Incontinence. 5th edition. Paris: ICUD-EAU; 2013. 1307–76.
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Gammie et al.
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