- Email: [email protected]
RE: NONINVASIVE TECHNIQUES FOR THE MEASUREMENT OF ISOVOLUMETRIC BLADDER PRESSURE
777
LETTERS TO THE EDITOR 1. Menon, M., Tewari, A., Peabody, J. and Members of the VIP Team: Vattikuti Institute prostatectomy: technique. J Urol, 169: 2289, 2003 2. Guillonneau, B. and Vallancien, G.: Laparoscopic radical prostatectomy: the Montsouris technique. J Urol, 163: 1643, 2000 DOI: 10.1097/01.ju.0000132396.04887.30
RE: METABOLIC EVALUATION OF 94 PATIENTS 5 TO 16 YEARS AFTER ILEOCECAL POUCH (MAINZ POUCH 1) CONTINENT URINARY DIVERSION J. Pfitzenmaier, J. Lotz, A. Faldum, M. Beringer, R. Stein and J. W. Thu¨roff J Urol, 170: 1884 –1887, 2003 To the Editor. It is important in clinical science that those who introduce and promote a particular surgical technique or some other kind of treatment provide an update of their results every once in a while. The article by Pfitzenmaier et al is yet another excellent example of a dedicated and meticulous followup of patients with ileocecal reservoirs from the institution where this form of urinary diversion was devised. However, in the discussion the authors perpetuate an assumption that has been impossible to eliminate from the standard reference lists in the urological literature on metabolic consequences of urinary reconstruction with bowel, namely the fact that (acute) systemic metabolic acidosis impairs the conversion of 25-cholecalciferol to 1,25dihydroxycholecalciferol was made in vitamin D depleted rats 26 years ago and has proved irrelevant in man.1, 2 We have known for quite a while now that in humans chronic metabolic acidosis has exactly the opposite effect and increases the serum concentration of 1,25dihydroxyvitamin D by stimulating its production rate.3, 4 Normal vitamin D levels in most existing experimental and clinical studies suggest that a contribution of this hormone to bone disease in continent urinary reconstruction is rather unlikely.5 Respectfully, Elmar W. Gerharz, Christopher R. J. Woodhouse and Hubertus Riedmiller Department of Urology Julius Maximilians University Medical School Josef Schneider Strasse 2 97080 Wu¨rzburg, Germany and Institute of Urology Royal Free and University College Medical School 48 Riding House St. London W1W 7EY, United Kingdom 1. Mills, R. D. and Studer, U. E.: Metabolic consequences of continent urinary diversion. J Urol, 161: 1057, 1999 2. Lee, S. W., Russell, J. and Avioli, L. V.: 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol: conversion impaired by systemic metabolic acidosis. Science, 195: 994, 1977 3. Krapf, R., Vetsch, R., Vetsch, W. and Hulter, H. N.: Chronic metabolic acidosis increases the serum concentration of 1,25dihydroxyvitamin D in humans by stimulating its production rate. Critical role of acidosis-induced renal hypophosphatemia. J Clin Invest, 90: 2456, 1992 4. Mahlbacher, K., Sicuro, A., Gerber, H., Hulter, H. N. and Krapf, R.: Growth hormone corrects acidosis-induced renal nitrogen wasting and renal phosphate depletion and attenuates renal magnesium wasting in humans. Metabolism, 48: 763, 1999 5. Gerharz, E. W., Gasser, J. A., Mosekilde, L., Moniz, C., Sitter, H., Barth, P. J. et al: Skeletal growth and long-term bone turnover after enterocystoplasty in a chronic rat model. BJU Int, 92: 306, 2003 DOI: 10.1097/01.ju.0000130865.13894.98
To the Editor: I read the article by Volkmer et al with extreme interest. However, the question arises regarding whether tensionfree vaginal tape (TVT) is actually a safe operation with respect to the 6 cases of severe complications stated by the authors. In addition, no data can be found on the total number of TVT procedures performed, so that we could form a picture of the actual prevalence of the complications described. Moreover, the prevalence of the described complications following TVT procedures seems to be too high for such a minimally invasive operative treatment for stress urinary incontinence, which is what the TVT procedure is supposed to represent. Up to 24% of patients suffer bladder perforation,1 up to 20% experience retention2 and 2% to 4% experience permanent urinary retention or subvesical obstruction (current study). At our institution TVT procedures were first introduced in 1999, and to date 143 procedures have been carried out. No significant complications have occurred during surgery, with the exception of 2 bladder perforations (1.4%) and 3 cases of retropubic hematoma (2.1%). We have had to cut the tape in 1 patient owing to postoperative urinary retention. Autocatheterization after surgery has not been necessary, and in 19 patients (13.3%) de novo overactive bladder (OAB) symptoms appeared after the procedure. Similar to Volkmer et al, we also established bladder erosion in 1 case (0.7%). Specifically, the patient complained of pain at the end of voiding, appearing for the first time 2 months after the TVT procedure. Eight months after the procedure cystoscopy and magnetic resonance imaging helped us to confirm the submucosal position of the tape. Volkmer et al also describe the operative method used to eliminate bladder erosion. If the approach to the operation itself is minimally invasive, it would only seem right to act similarly regarding complications. In the opinion of Volkmer et al the surgical method of choice should be the open suprapubic approach, where the bladder must be opened to remove the tape. We believe that in the sense of minimally invasive surgery transurethral resection of the part of the tape lying intramurally would be an option. This method is acceptable to the patient on account of the minimum invasiveness of the procedure, and at least in our patient it proved to be effective. In conclusion, according to our experience we believe that the TVT procedure represents a safe method for the treatment of patients with stress urinary incontinence. Nevertheless, more attention should be focused on the late complications of the TVT procedure, such as the occurrence of de novo OAB symptoms and bladder erosion. At any rate, an active search would be necessary to detect the latter condition, perhaps particularly in those patients stating suprapubic pain after the procedure or complaining of the appearance of disturbing de novo OAB symptoms. Certainly further reports are necessary with the aim of evaluating the actual prevalence of bladder erosion associated with the use of polypropylene tape. Respectfully, Igor But Department of Gynecology and Urogynecology Maribur Teaching Hospital Ljubljanska 5 SI-2000, Maribar Slovenia 1. Niemczyk, P., Klutke, J. J., Carlin, B. I. and Klutke, C. G.: United States experience with tension-free vaginal tape procedure for urinary stress incontinence: assessment of safety and tolerability. Tech Urol, 7: 261, 2001 2. Lebret, T., Lugagne, P. M., Herve, J. M., Barre, P., Orsoni, J. L., Yonneau, L. et al: Evaluation of tension-free vaginal tape procedure. Its safety and efficacy in the treatment of female stress urinary incontinence during the learning phase. Eur Urol, 40: 543, 2001 DOI: 10.1097/01.ju.0000130583.04707.75
RE: NONINVASIVE TECHNIQUES FOR THE MEASUREMENT OF ISOVOLUMETRIC BLADDER PRESSURE C. Blake and P. Abrams
RE: SURGICAL INTERVENTION FOR COMPLICATIONS OF THE TENSION-FREE VAGINAL TAPE PROCEDURE B. G. Volkmer, T. Nesslauer, L. Rinnab, T. Schradin, R. E. Hautmann and H.-W. Gottfried J Urol, 169: 570 –574, 2003
J Urol, 171: 12–19, 2004 To the Editor. We enjoy the friendly competition of the research groups involved in noninvasive urodynamics, which we think stimulates our common interest. In this spirit we read the review by Blake and Abrams with great interest. As the authors have personal experience with only one or two of the reviewed methods, a slight
778
LETTERS TO THE EDITOR
bias is perhaps unavoidable. In this letter we hope to counterbalance this bias. In the section on the external condom catheter it is stated that abdominal pressure was not measured in our experiments so that it is unknown how this affected the isovolumetric pressure.1–5 Indeed, we did not describe abdominal pressure in those publications. However, we measured that pressure and evaluated its effects in another study.6 At the end of the same section it is concluded, “At present, this technique is not ready to replace invasive urodynamics, but is being used in a longitudinal study. . ..”7 The reference describes the longitudinal study but not the conclusion drawn. Rather, we have earlier concluded that “in patients with a not too weak flow rate this method can replace classical urodynamics to classify BOO.”8 The “not too weak” limitation reflects our conclusion that at low flow rates the measured pressure does not accurately reflect the bladder pressure.9 We calculated a cutoff value of 5.4 ml per second for accurate measurement of bladder pressure using the condom catheter method. To our knowledge a lower limit for the maximum flow rate has not been established for the other noninvasive methods, but it is difficult to imagine that any accurate noninvasive pressure measurement would be possible in a patient voiding 3 ml per second. In Appendix 1 in the article “Failure for bladder and condom pressure to equalize” is listed as one of the possible sources of artifact of the condom method. Such failure can only result from sphincter closure. While sphincter closure is listed in Appendix 2 as a possible source of artifact for all noninvasive methods, it is not listed in Appendix 1 as a source of artifact of the cuff method. To balance Appendix 1, it would be more correct to list sphincter closure as a possible source of artifact for all methods, and to delete the resulting “Failure. . .” for the condom method. In the abstract and in the conclusions of the review it is concluded that the penile cuff and/or penile squeeze technique “would seem the most likely to be clinically useful.” It is unclear to us how this conclusion relates to the results discussed. From trying to compare methods for pressure flow analysis we have learned that a comparison of different measurement methods— especially when those methods are not measuring exactly the same variable—is difficult indeed. It would seem that a comparison should at least take diagnostic accuracy and aspects of applicability, such as the success rate of the measurement and its morbidity, into account. Diagnostic accuracy. In the review a rate of 90% is cited for “agreement with pressure flow study diagnosis” of the condom catheter method, if obstructed and equivocal groups are taken together. This rate was established in a small group of 56 patients. For the cuff method manual counting in figure 3 in a study by Griffiths et al,10 which seems to be an updated version of figure 8 in the review article, results in 76% being correctly classified in a group of 143 patients if equivocal and unobstructed groups are taken together. The total manual count did not match the number of patients in the legend. If it is assumed that all patients who were not manually identified in the plot are correctly classified, the percentage of those correctly classified would be 78%. Success rate. We have applied the condom catheter method in 1,073 subjects in a longitudinal study of changes in bladder contractility secondary to benign prostatic hyperplasia (these data were not yet available to the reviewers). In 95% of subjects at least one successful measurement was done.11 In an intermediate analysis of the first 659 subjects this figure was 94%.12 This publication also defines the test population. The missing 5% or 6% includes failures due to condom leakage. Blake and Abrams state that successful manual compression-release maneuvers were performed in 93% of patients. In an evaluation of the compression-release maneuver using the cuff Harding et al excluded 49 of 150 subjects (33%) because of low voided volume, no arrest or return of voiding, lack of comparable pressure flow study data or technical failure.13 A flow chart of those exclusions and a complete description of inclusion and exclusion criteria would be necessary for a comparison with published success rates of the other methods. Morbidity. In our study we unexpectedly encountered some morbidity of the “noninvasive” condom catheter method—macroscopic hematuria occurred in 7% of the subjects. The hematuria was light and self-limiting, and no therapy was necessary. No doubt the hematuria resulted from the exposure of the urethra to pressures of up to 200 cm H2O, for which it was not designed. No data were published on the morbidity of the cuff and squeeze methods, but the occasional occurrence of hematuria was confirmed in personal communication.
Contrary to Blake and Abrams, we think that insufficient data are available for a comparison of the clinical usefulness of the discussed methods. However, we consider the published results of the condom catheter method most encouraging.
1. 2. 3. 4.
5. 6.
7.
8.
9.
10.
11. 12.
13.
14.
15. 16.
17.
18. 19.
Respectfully, R. van Mastrigt, J. J. M. Pel and J. W. N. C. Huang Foen Chung Department of Urology, sector Furore Room EE1630 Erasmus MC P. O. Box 1738 3000 DR Rotterdam The Netherlands Pel, J. J. and van Mastrigt, R.: Non-invasive measurement of bladder pressure using an external catheter. Neurourol Urodyn, 18: 455, 1999 van Mastrigt, R.: Noninvasive bladder pressure measurement. Methodology and reproducibility. Neurourol Urodyn, 14: 480, 1995 van Mastrigt, R. and Kranse, M.: Accuracy of non-invasive urodynamics in diagnosing infravesical obstruction. Neurourol Urodyn, 14: 451, 1995 Groen, J., van Mastrigt, R., van Asselt, E., van Koeveringe, G. A. and Bosch, R.: Contractility parameters of the guinea pig bladder in situ: similarity to human bladder contractility. J Urol, 151: 1405, 1994 Rikken, B., Pel, J. J. M. and van Mastrigt, R.: Repeat noninvasive bladder pressure measurements with an external catheter. J Urol, 162: 474, 1999 Pel, J. J., Bosch, J. L., Blom, J. H., Lycklama a Nijeholt, A. A. and van Mastrigt, R.: Development of a non-invasive strategy to classify bladder outlet obstruction in male patients with LUTS. Neurourol Urodyn, 21: 117, 2002 Huang Foen Chung, J. W., Bohnen, A. M., Pel, J. J., Bosch, R., Niesing, R. and van Mastrigt, R.: Application of non-invasive urodynamics to longitudinally study changes in urinary bladder contractility. Neurourol Urodyn, 21: 351, 2002 Pel, J. J. M., Huang Foen Chung, J. W. N. C. and van Mastrigt, R.: Practical application of noninvasive tests to grade outflow obstruction and bladder contractility. The end of classical urodynamics? In: Prostate Cancer, Benign Prostatic Hyperplasia and Basic Research. An Update. Edited by C. H. Bangma and D. W. W. Newling. London: Parthenon Publishing Group, pp. 88 –97, 2003 Pel, J. J. and van Mastrigt, R.: A flow rate cut-off value as a criterion for the accurate non-invasive measurement of bladder pressure using a condom-type catheter. Urol Res, 31: 177, 2003 Griffiths, C., Blake, C., Harding, C., McIntosh, S., Drinnan, M., Robson, W. et al: Non-invasive bladder pressure: the case for using a modified ICS nomogram. Neurourol Urodyn, 22: 367, 2003 Huang Foen Chung, J. W. N. C. and van Mastrigt, R.: Unpublished data Huang Foen Chung, J. W., Bo´hnen, A. M., Pel, J. J., Bosch, J. L., Niesing, R. and van Mastrigt, R.: Applicability and reproducibility of the condom catheter method for measuring the isovolumetric bladder pressure. Urology, 63: 56, 2004 Harding, C., McIntosh, S., Robson, W., Ramsden, P., Drinnan, M., Griffiths, C. et al: Validation of the penile compressionrelease manoeuvre for non-invasive diagnosis of bladder outlet obstruction. Neurourol Urodyn, 22: 369, 2003 Gommer, E. D., Vanspauwen, T. J., Miklosi, M., Wen, J. G., Kinder, M. V., Janknegt, R. A. et al: Validity of a non-invasive determination of the isovolumetric bladder pressure during voiding in men with LUTS. Neurourol Urodyn, 18: 477, 1999 Reynard, J. M., Peters, T. J., Lamond, E. and Abrams, P.: The significance of abdominal straining in men with lower urinary tract symptoms. Br J Urol, 75: 148, 1995 Griffiths, C., Rix, D., Macdonald, A., Drinnan, M., Pickard, R. and Ramsden, P.: Noninvasive measurement of bladder pressure by controlled inflation of a penile cuff. J Urol, 167: 1344, 2002 Blake, C., Baldry, L., Hassine, A. and Abrams, P.: Evaluation of the non-invasive estimation of bladder pressure using a penile cuff. An alternative to pressure-flow studies in men? Presented at 33rd annual meeting of International Continence Society, Florence, Italy, October 5–9, 2003 Pel, J. and van Mastrigt, R.: The accuracy of non-invasive bladder pressure measurement with an external catheter. Neurourol Urodyn, 18: 251, 1999 Robson, W., McIntosh, S., Drinnan, M., Ramsden, P., Griffiths, C. and Pickard, R.: Patient acceptability of a non-invasive bladder pressure measurement technique. Presented at 32nd annual meeting of International Continence Society, Heidelberg, Germany, August 28 –30, 2002
LETTERS TO THE EDITOR 1. Menon, M., Tewari, A., Peabody, J. and Members of the VIP Team: Vattikuti Institute prostatectomy: technique. J Urol, 169: 2289, 2003 2. Guillonneau, B. and Vallancien, G.: Laparoscopic radical prostatectomy: the Montsouris technique. J Urol, 163: 1643, 2000 DOI: 10.1097/01.ju.0000132396.04887.30
RE: METABOLIC EVALUATION OF 94 PATIENTS 5 TO 16 YEARS AFTER ILEOCECAL POUCH (MAINZ POUCH 1) CONTINENT URINARY DIVERSION J. Pfitzenmaier, J. Lotz, A. Faldum, M. Beringer, R. Stein and J. W. Thu¨roff J Urol, 170: 1884 –1887, 2003 To the Editor. It is important in clinical science that those who introduce and promote a particular surgical technique or some other kind of treatment provide an update of their results every once in a while. The article by Pfitzenmaier et al is yet another excellent example of a dedicated and meticulous followup of patients with ileocecal reservoirs from the institution where this form of urinary diversion was devised. However, in the discussion the authors perpetuate an assumption that has been impossible to eliminate from the standard reference lists in the urological literature on metabolic consequences of urinary reconstruction with bowel, namely the fact that (acute) systemic metabolic acidosis impairs the conversion of 25-cholecalciferol to 1,25dihydroxycholecalciferol was made in vitamin D depleted rats 26 years ago and has proved irrelevant in man.1, 2 We have known for quite a while now that in humans chronic metabolic acidosis has exactly the opposite effect and increases the serum concentration of 1,25dihydroxyvitamin D by stimulating its production rate.3, 4 Normal vitamin D levels in most existing experimental and clinical studies suggest that a contribution of this hormone to bone disease in continent urinary reconstruction is rather unlikely.5 Respectfully, Elmar W. Gerharz, Christopher R. J. Woodhouse and Hubertus Riedmiller Department of Urology Julius Maximilians University Medical School Josef Schneider Strasse 2 97080 Wu¨rzburg, Germany and Institute of Urology Royal Free and University College Medical School 48 Riding House St. London W1W 7EY, United Kingdom 1. Mills, R. D. and Studer, U. E.: Metabolic consequences of continent urinary diversion. J Urol, 161: 1057, 1999 2. Lee, S. W., Russell, J. and Avioli, L. V.: 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol: conversion impaired by systemic metabolic acidosis. Science, 195: 994, 1977 3. Krapf, R., Vetsch, R., Vetsch, W. and Hulter, H. N.: Chronic metabolic acidosis increases the serum concentration of 1,25dihydroxyvitamin D in humans by stimulating its production rate. Critical role of acidosis-induced renal hypophosphatemia. J Clin Invest, 90: 2456, 1992 4. Mahlbacher, K., Sicuro, A., Gerber, H., Hulter, H. N. and Krapf, R.: Growth hormone corrects acidosis-induced renal nitrogen wasting and renal phosphate depletion and attenuates renal magnesium wasting in humans. Metabolism, 48: 763, 1999 5. Gerharz, E. W., Gasser, J. A., Mosekilde, L., Moniz, C., Sitter, H., Barth, P. J. et al: Skeletal growth and long-term bone turnover after enterocystoplasty in a chronic rat model. BJU Int, 92: 306, 2003 DOI: 10.1097/01.ju.0000130865.13894.98
To the Editor: I read the article by Volkmer et al with extreme interest. However, the question arises regarding whether tensionfree vaginal tape (TVT) is actually a safe operation with respect to the 6 cases of severe complications stated by the authors. In addition, no data can be found on the total number of TVT procedures performed, so that we could form a picture of the actual prevalence of the complications described. Moreover, the prevalence of the described complications following TVT procedures seems to be too high for such a minimally invasive operative treatment for stress urinary incontinence, which is what the TVT procedure is supposed to represent. Up to 24% of patients suffer bladder perforation,1 up to 20% experience retention2 and 2% to 4% experience permanent urinary retention or subvesical obstruction (current study). At our institution TVT procedures were first introduced in 1999, and to date 143 procedures have been carried out. No significant complications have occurred during surgery, with the exception of 2 bladder perforations (1.4%) and 3 cases of retropubic hematoma (2.1%). We have had to cut the tape in 1 patient owing to postoperative urinary retention. Autocatheterization after surgery has not been necessary, and in 19 patients (13.3%) de novo overactive bladder (OAB) symptoms appeared after the procedure. Similar to Volkmer et al, we also established bladder erosion in 1 case (0.7%). Specifically, the patient complained of pain at the end of voiding, appearing for the first time 2 months after the TVT procedure. Eight months after the procedure cystoscopy and magnetic resonance imaging helped us to confirm the submucosal position of the tape. Volkmer et al also describe the operative method used to eliminate bladder erosion. If the approach to the operation itself is minimally invasive, it would only seem right to act similarly regarding complications. In the opinion of Volkmer et al the surgical method of choice should be the open suprapubic approach, where the bladder must be opened to remove the tape. We believe that in the sense of minimally invasive surgery transurethral resection of the part of the tape lying intramurally would be an option. This method is acceptable to the patient on account of the minimum invasiveness of the procedure, and at least in our patient it proved to be effective. In conclusion, according to our experience we believe that the TVT procedure represents a safe method for the treatment of patients with stress urinary incontinence. Nevertheless, more attention should be focused on the late complications of the TVT procedure, such as the occurrence of de novo OAB symptoms and bladder erosion. At any rate, an active search would be necessary to detect the latter condition, perhaps particularly in those patients stating suprapubic pain after the procedure or complaining of the appearance of disturbing de novo OAB symptoms. Certainly further reports are necessary with the aim of evaluating the actual prevalence of bladder erosion associated with the use of polypropylene tape. Respectfully, Igor But Department of Gynecology and Urogynecology Maribur Teaching Hospital Ljubljanska 5 SI-2000, Maribar Slovenia 1. Niemczyk, P., Klutke, J. J., Carlin, B. I. and Klutke, C. G.: United States experience with tension-free vaginal tape procedure for urinary stress incontinence: assessment of safety and tolerability. Tech Urol, 7: 261, 2001 2. Lebret, T., Lugagne, P. M., Herve, J. M., Barre, P., Orsoni, J. L., Yonneau, L. et al: Evaluation of tension-free vaginal tape procedure. Its safety and efficacy in the treatment of female stress urinary incontinence during the learning phase. Eur Urol, 40: 543, 2001 DOI: 10.1097/01.ju.0000130583.04707.75
RE: NONINVASIVE TECHNIQUES FOR THE MEASUREMENT OF ISOVOLUMETRIC BLADDER PRESSURE C. Blake and P. Abrams
RE: SURGICAL INTERVENTION FOR COMPLICATIONS OF THE TENSION-FREE VAGINAL TAPE PROCEDURE B. G. Volkmer, T. Nesslauer, L. Rinnab, T. Schradin, R. E. Hautmann and H.-W. Gottfried J Urol, 169: 570 –574, 2003
J Urol, 171: 12–19, 2004 To the Editor. We enjoy the friendly competition of the research groups involved in noninvasive urodynamics, which we think stimulates our common interest. In this spirit we read the review by Blake and Abrams with great interest. As the authors have personal experience with only one or two of the reviewed methods, a slight
778
LETTERS TO THE EDITOR
bias is perhaps unavoidable. In this letter we hope to counterbalance this bias. In the section on the external condom catheter it is stated that abdominal pressure was not measured in our experiments so that it is unknown how this affected the isovolumetric pressure.1–5 Indeed, we did not describe abdominal pressure in those publications. However, we measured that pressure and evaluated its effects in another study.6 At the end of the same section it is concluded, “At present, this technique is not ready to replace invasive urodynamics, but is being used in a longitudinal study. . ..”7 The reference describes the longitudinal study but not the conclusion drawn. Rather, we have earlier concluded that “in patients with a not too weak flow rate this method can replace classical urodynamics to classify BOO.”8 The “not too weak” limitation reflects our conclusion that at low flow rates the measured pressure does not accurately reflect the bladder pressure.9 We calculated a cutoff value of 5.4 ml per second for accurate measurement of bladder pressure using the condom catheter method. To our knowledge a lower limit for the maximum flow rate has not been established for the other noninvasive methods, but it is difficult to imagine that any accurate noninvasive pressure measurement would be possible in a patient voiding 3 ml per second. In Appendix 1 in the article “Failure for bladder and condom pressure to equalize” is listed as one of the possible sources of artifact of the condom method. Such failure can only result from sphincter closure. While sphincter closure is listed in Appendix 2 as a possible source of artifact for all noninvasive methods, it is not listed in Appendix 1 as a source of artifact of the cuff method. To balance Appendix 1, it would be more correct to list sphincter closure as a possible source of artifact for all methods, and to delete the resulting “Failure. . .” for the condom method. In the abstract and in the conclusions of the review it is concluded that the penile cuff and/or penile squeeze technique “would seem the most likely to be clinically useful.” It is unclear to us how this conclusion relates to the results discussed. From trying to compare methods for pressure flow analysis we have learned that a comparison of different measurement methods— especially when those methods are not measuring exactly the same variable—is difficult indeed. It would seem that a comparison should at least take diagnostic accuracy and aspects of applicability, such as the success rate of the measurement and its morbidity, into account. Diagnostic accuracy. In the review a rate of 90% is cited for “agreement with pressure flow study diagnosis” of the condom catheter method, if obstructed and equivocal groups are taken together. This rate was established in a small group of 56 patients. For the cuff method manual counting in figure 3 in a study by Griffiths et al,10 which seems to be an updated version of figure 8 in the review article, results in 76% being correctly classified in a group of 143 patients if equivocal and unobstructed groups are taken together. The total manual count did not match the number of patients in the legend. If it is assumed that all patients who were not manually identified in the plot are correctly classified, the percentage of those correctly classified would be 78%. Success rate. We have applied the condom catheter method in 1,073 subjects in a longitudinal study of changes in bladder contractility secondary to benign prostatic hyperplasia (these data were not yet available to the reviewers). In 95% of subjects at least one successful measurement was done.11 In an intermediate analysis of the first 659 subjects this figure was 94%.12 This publication also defines the test population. The missing 5% or 6% includes failures due to condom leakage. Blake and Abrams state that successful manual compression-release maneuvers were performed in 93% of patients. In an evaluation of the compression-release maneuver using the cuff Harding et al excluded 49 of 150 subjects (33%) because of low voided volume, no arrest or return of voiding, lack of comparable pressure flow study data or technical failure.13 A flow chart of those exclusions and a complete description of inclusion and exclusion criteria would be necessary for a comparison with published success rates of the other methods. Morbidity. In our study we unexpectedly encountered some morbidity of the “noninvasive” condom catheter method—macroscopic hematuria occurred in 7% of the subjects. The hematuria was light and self-limiting, and no therapy was necessary. No doubt the hematuria resulted from the exposure of the urethra to pressures of up to 200 cm H2O, for which it was not designed. No data were published on the morbidity of the cuff and squeeze methods, but the occasional occurrence of hematuria was confirmed in personal communication.
Contrary to Blake and Abrams, we think that insufficient data are available for a comparison of the clinical usefulness of the discussed methods. However, we consider the published results of the condom catheter method most encouraging.
1. 2. 3. 4.
5. 6.
7.
8.
9.
10.
11. 12.
13.
14.
15. 16.
17.
18. 19.
Respectfully, R. van Mastrigt, J. J. M. Pel and J. W. N. C. Huang Foen Chung Department of Urology, sector Furore Room EE1630 Erasmus MC P. O. Box 1738 3000 DR Rotterdam The Netherlands Pel, J. J. and van Mastrigt, R.: Non-invasive measurement of bladder pressure using an external catheter. Neurourol Urodyn, 18: 455, 1999 van Mastrigt, R.: Noninvasive bladder pressure measurement. Methodology and reproducibility. Neurourol Urodyn, 14: 480, 1995 van Mastrigt, R. and Kranse, M.: Accuracy of non-invasive urodynamics in diagnosing infravesical obstruction. Neurourol Urodyn, 14: 451, 1995 Groen, J., van Mastrigt, R., van Asselt, E., van Koeveringe, G. A. and Bosch, R.: Contractility parameters of the guinea pig bladder in situ: similarity to human bladder contractility. J Urol, 151: 1405, 1994 Rikken, B., Pel, J. J. M. and van Mastrigt, R.: Repeat noninvasive bladder pressure measurements with an external catheter. J Urol, 162: 474, 1999 Pel, J. J., Bosch, J. L., Blom, J. H., Lycklama a Nijeholt, A. A. and van Mastrigt, R.: Development of a non-invasive strategy to classify bladder outlet obstruction in male patients with LUTS. Neurourol Urodyn, 21: 117, 2002 Huang Foen Chung, J. W., Bohnen, A. M., Pel, J. J., Bosch, R., Niesing, R. and van Mastrigt, R.: Application of non-invasive urodynamics to longitudinally study changes in urinary bladder contractility. Neurourol Urodyn, 21: 351, 2002 Pel, J. J. M., Huang Foen Chung, J. W. N. C. and van Mastrigt, R.: Practical application of noninvasive tests to grade outflow obstruction and bladder contractility. The end of classical urodynamics? In: Prostate Cancer, Benign Prostatic Hyperplasia and Basic Research. An Update. Edited by C. H. Bangma and D. W. W. Newling. London: Parthenon Publishing Group, pp. 88 –97, 2003 Pel, J. J. and van Mastrigt, R.: A flow rate cut-off value as a criterion for the accurate non-invasive measurement of bladder pressure using a condom-type catheter. Urol Res, 31: 177, 2003 Griffiths, C., Blake, C., Harding, C., McIntosh, S., Drinnan, M., Robson, W. et al: Non-invasive bladder pressure: the case for using a modified ICS nomogram. Neurourol Urodyn, 22: 367, 2003 Huang Foen Chung, J. W. N. C. and van Mastrigt, R.: Unpublished data Huang Foen Chung, J. W., Bo´hnen, A. M., Pel, J. J., Bosch, J. L., Niesing, R. and van Mastrigt, R.: Applicability and reproducibility of the condom catheter method for measuring the isovolumetric bladder pressure. Urology, 63: 56, 2004 Harding, C., McIntosh, S., Robson, W., Ramsden, P., Drinnan, M., Griffiths, C. et al: Validation of the penile compressionrelease manoeuvre for non-invasive diagnosis of bladder outlet obstruction. Neurourol Urodyn, 22: 369, 2003 Gommer, E. D., Vanspauwen, T. J., Miklosi, M., Wen, J. G., Kinder, M. V., Janknegt, R. A. et al: Validity of a non-invasive determination of the isovolumetric bladder pressure during voiding in men with LUTS. Neurourol Urodyn, 18: 477, 1999 Reynard, J. M., Peters, T. J., Lamond, E. and Abrams, P.: The significance of abdominal straining in men with lower urinary tract symptoms. Br J Urol, 75: 148, 1995 Griffiths, C., Rix, D., Macdonald, A., Drinnan, M., Pickard, R. and Ramsden, P.: Noninvasive measurement of bladder pressure by controlled inflation of a penile cuff. J Urol, 167: 1344, 2002 Blake, C., Baldry, L., Hassine, A. and Abrams, P.: Evaluation of the non-invasive estimation of bladder pressure using a penile cuff. An alternative to pressure-flow studies in men? Presented at 33rd annual meeting of International Continence Society, Florence, Italy, October 5–9, 2003 Pel, J. and van Mastrigt, R.: The accuracy of non-invasive bladder pressure measurement with an external catheter. Neurourol Urodyn, 18: 251, 1999 Robson, W., McIntosh, S., Drinnan, M., Ramsden, P., Griffiths, C. and Pickard, R.: Patient acceptability of a non-invasive bladder pressure measurement technique. Presented at 32nd annual meeting of International Continence Society, Heidelberg, Germany, August 28 –30, 2002