Applicability and reproducibility of condom catheter method for measuring isovolumetric bladder pressure

[Diagnostic work-up of benign prostatic hyperplasia : The German S2e-guideline 2023 part 1]

BACKGROUND

Lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH; in German guidelines: benign prostatic syndrome [BPS]) is the most frequent urological disease in men and can result in a considerable deterioration of quality-of-life. BPS can be associated with LUTS, benign prostatic enlargement (BPE), and bladder outlet obstruction (BOO) or benign prostatic obstruction (BPO), respectively. The expert group on BPS of the German Society of Urology has re-evaluated the tests for the assessment of BPH and provides evidence-based recommendations.

OBJECTIVES

Presentation and evidence-based rating of tests for the assessment of patients with BPS.

MATERIALS AND METHODS

Summary and overview of chapters 5, 6, and 8 of the latest long version of the German S2e guideline on BPS.

RESULTS

The diagnostic work-up should clarify (1) whether the complaints of the patient are caused by BPS, (2) how relevant the complaints are and whether treatment is necessary, (3) whether complications of the lower or upper urinary tract already exist, and (4) which treatment will be most suitable. Baseline assessment should be done in all BPS patients and include history, measurement of LUTS and quality-of-life, urinalysis, serum prostate-specific antigen, post-void residual, ultrasound of the lower urinary tract, including measurements of prostate volume, intravesical prostatic protrusion and detrusor wall thickness, and ultrasound of the upper urinary tract. Additional tests can follow when questions remain unanswered after baseline assessment. These optional tests include bladder diaries, uroflowmetry, serum creatinine, urethrocystoscopy, other noninvasive tests for the determination of BOO/BPO such as penile cuff test, condom catheter method and near-infrared spectroscopy, and other imagining tests such as X‑ray and MRI investigations.

CONCLUSIONS

The updated German S2e guideline summarizes evidence-based recommendations on the diagnostic work-up, including the assessment of the BPS components BPE, LUTS, and BOO/BPO.

Minimally invasive measurement of vesical pressure for diagnosis of infravesical obstruction

AIMS

This study was focused on the clinical test of an improved and portable version of a previously described urethral connector (UC), designed for minimally invasive measurement of vesical pressure and diagnosis of infravesical obstruction in men.

METHODS

The conventional pressure-flow study (PFS) and the test with the new version of UC were applied to individuals reporting lower urinary tract symptoms (LUTS), who were then classified as obstructed or non-obstructed/equivocal based on the bladder outlet obstruction index (BOOI) from PFS data. Two-way analysis of variance was used to compare the values of urine flow rate and vesical pressure between methods and diagnoses.

RESULTS

Vesical pressure and urine flow values were not significantly different between methods (P > 0.05), while the former was greater in the group classified as obstructed.

CONCLUSION

The present results showed that the UC test can support the diagnosis of infravesical obstruction in a comparable way as that of the conventional urodynamic method, however with the advantages of simplicity and minimal invasiveness, having thus the potential to be an alternative method for long term follow-up of individuals reporting LUTS.

Urinary Bladder Contractility Revisited. Correlation of Noninvasively and Invasively Measured Contractility Parameters in Patients Eligible for Transurethral Resection of the Prostate

OBJECTIVE

To validate a noninvasively estimated measure of urinary bladder contractility by correlating it with 3 existing invasive contractility parameters and to compare and correlate those invasive parameters.

METHODS

A group of 74 patients, recruited in 3 different hospitals, and eligible for transurethral resection of the prostate on clinical grounds, were noninvasively studied preoperatively using the condom catheter method. The maximum condom pressure pcond.max measured during a mechanical interruption of flow rate was considered an estimate of urinary bladder contractility and compared to conventional contractility parameters calculated from preoperative (invasive) pressure-flow studies.

RESULTS

The highest correlations were found between the invasive parameters. The correlation between the noninvasive parameter on the one hand and the invasive parameters on the other hand was lower, but mostly significant. In a number of patients, pcond.max underestimated the isovolumetric bladder pressure. The underestimated patients were more obstructed than those who were not underestimated and had a higher (invasively measured) contractility. When the underestimated patients were deselected, the correlation between the noninvasive pcond.max and the invasive parameters in the remaining 52 patients was higher.

CONCLUSION

The 4 tested contractility parameters represent different aspects of urinary bladder contractility. Nevertheless, there was a significant correlation among them supporting the concept of a common basis, that is, detrusor contractility. The invasive contractility parameter bladder contractility index overestimated contractility in patients with lower urinary tract symptoms and/or benign prostatic enlargement. A modified parameter is suggested.

Correlation between penile cuff test and pressure-flow study in patients candidates for trans-urethral resection of prostate

Background

Aim of this study was to make a comparison between penile cuff test (PCT) and standard pressure-flow study (PFS) in the preoperative evaluation of patients candidates for trans-urethral resection of prostate (TURP) for benign prostatic obstruction (BPO).

Methods

We enrolled male patients with lower urinary tract symptoms candidates for TURP. Each of them underwent a PCT and a subsequent PFS. A statistical analysis was performed: sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), likelihood ratio and ratio of corrected classified were calculated. Fisher exact test was used to evaluate relationships between PCT and maximal urine flow (Q_max): a p-value < 0.05 was considered statistically significant.

Results

We enrolled 48 consecutive patients. Overall, at PCT 31 patients were diagnosed as obstructed and 17 patients as unobstructed. At the subsequent PFS, 21 out of 31 patients diagnosed as obstructed at PCT were confirmed to be obstructed; one was diagnosed as unobstructed; the remaining 9 patients appeared as equivocal. Concerning the 17 patients unobstructed at PCT, all of them were confirmed not to be obstructed at PFS, with 10 equivocal and 7 unobstructed. The rate of correctly classified patients at PCT was 79% (95%-CI 65%-90%). About detecting obstructed patients, PCT showed a SE of 100% and a SP of 63%. The PPV was 68%, while the NPV was 100%.

Conclusions

PCT can be an efficient tool in evaluating patients candidates for TURP. In particular, it showed good reliability in ruling out BPO because of its high NPV, with a high rate of correctly classified patients overall. Further studies on a huger number of patients are needed, including post-operative follow-up as well.

Assessment of BPH/BOO

The assessment of men with bladder outflow obstruction relies on an adequate history and examination. Uroflowmetry and post-void residue estimation are very revealing and may be sufficient in the majority of men. The prostate-specific antigen test may be used to select men who are at a high risk of progression. In specific situations, cystometry may be required. We discuss the use of cystometry and the newer less-invasive methods of assessment that have emerged over the last few years, including ultrasound estimation of intravesical prostatic protrusion, prostatic urethra angle, detrusor wall thickness, ultrasound-estimated bladder weight, near-infrared spectroscopy and the condom catheter and penile cuff tests. Although these techniques show promise, they still require further modifications, standardization and testing in larger populations. In addition, they should be used in men where only specific questions need to be answered.

Longitudinal changes in isovolumetric bladder pressure in response to age-related prostate growth in 1,020 healthy male volunteers

AIM

To non-invasively study if compensation and decompensation occurs in the urinary bladder of healthy male volunteers in response to benign prostatic enlargement (BPE) using the condom catheter method.

METHODS

Between 2001 and 2010, 1,020 healthy male volunteers were included in a longitudinal study based on three non-invasive urodynamic examinations during a 5-year follow-up. Inclusion criteria were an informed consent, the ability to void in a normal standing position and a minimum free flow rate of 5.4 ml/sec. Study parameters were prostate volume (PV), maximum free urinary flow rate (Q(max)) and bladder contractility, quantified by the maximum isovolumetric bladder pressure, measured in the condom (P(cond.max)). Volunteers also completed the International Prostate Symptom Score Form (IPSS).

RESULTS

Within limitations, the included volunteers had a flat age distribution between 38 and 72 years. This made it possible to combine longitudinal analysis in a 5-year observation interval, with cross sectional analysis in a 35-year age range. Longitudinal analysis showed that with increasing age, PV increased with 1.9% per year, whereas Qmax decreased with 1.1% per year. IPSS increased with 1.1% per year when volunteers were older than 55 years. P(cond.max) increased during the 5-year longitudinal follow-up, but not in the cross sectional analysis.

CONCLUSIONS

The difference between cross sectional and longitudinal results of the P(cond.max) may have been caused by compensation of the urinary bladder resulting in a selection effect. This would imply that compensation is a relatively fast process, taking approximately 5 years.

Continuous non-invasive measurement of bladder voiding pressure using an experimental constant low-flow test

PURPOSE

We developed a prototype device using an automatically controlled inflatable penile cuff to measure bladder voiding pressure continuously and non-invasively in men. The purpose of this study was to validate the pressure measurements made by this device by comparison to those during simultaneous invasive PFS.

METHODS

A device was developed to automatically modulate flow rate by controlling pressure in a penile cuff. Men undergoing conventional urodynamics studies were recruited to have an additional fill-void cycle whilst using the new device. We report on 40 men using a standardized protocol. Pressure measured by this device was compared with simultaneous vesical pressure by evaluating maximum pressure during voiding, and calculating the root mean square (RMS) difference between p(cuff) and p(ves) .

RESULTS

We recruited 80 men of whom 18 were excluded, 22 were involved in initial development phase and 40 in the standard protocol. Mean (SD) difference between maxima of p(cuff) and p(ves) (1.3 (15.6) cmH(2) O) was not significant. In 20 (50%) men, agreement between p(cuff) and p(ves) throughout the void was moderate or good (RMS difference <20 cmH(2) O). Causes of unsuccessful measurements were identified.

CONCLUSIONS

Although a prototype device, this technique appears to be promising for continuous non-invasive bladder pressure measurement. From the results of this study a number of improvements have been recommended and implemented. The next generation of this technique will allow assessment of clinical application.

Development and application of the condom catheter method for non-invasive measurement of bladder pressure

Objectives:

A non-invasive method to measure the bladder pressure in males using a condom catheter has been developed. The measurement technique, its validation and limitations, a diagnostic nomogram to non-invasively diagnose bladder outlet obstruction (BOO), and results of large-scale application are discussed.

Methods:

Modified incontinence condoms are attached to the penis. During voiding the flow of urine is mechanically interrupted. The subsequent maximum pressure in the condom reflects the isovolumetric bladder pressure. The method was validated in a group of 46 patients with lower urinary tract symptoms who were simultaneously studied invasively and non-invasively. Subsequently it was applied in a non-invasive epidemiological study in 1020 healthy males.

Results:

The reproducibility of the measured isovolumetric bladder pressure is comparable to that of conventional pressure-flow parameters. The measured pressure can be used to diagnose bladder outlet obstruction with a diagnostic accuracy (Area Under receiver operator characteristic curve) of 0.98, which compares most favorably with the area under the curve of 0.79 of Q_max in the same population. During condom catheter measurements, both the involuntary interruption of voiding and the forced diuresis increase post-void residual volume. This increase does not affect the accuracy of the pressure measurements.

Conclusions:

We conclude that in males bladder pressure can successfully be measured non-invasively using the condom catheter method. By combining the measured volumetric bladder pressure with a separately measured free flow rate, BOO can non-invasively and accurately be diagnosed.

The Role of Non-Invasive Urodynamics in Bladder Outlet Obstruction Diagnosis in Male Patients

Purpose

Many Methods have been suggested to assess bladder outlet obstruction, as defined by the gold standard of pressure flow studies. A comprehensive review of the literature on the different methods used to diagnose bladder outlet obstruction by non-invasive means was performed in order to compare those methods to invasive urodynamics in terms of sensitivity and specificity.

Materials and Methods

A MEDLINE search was done of the published literature covering from December 2003 on non-invasive methods, including only single measures to diagnose bladder outlet obstruction. We performed a comparison between all methods in terms of sensitivity and specificity for each test. For many techniques these values were calculated directly from the data presented in the article.

Results

There has been applied many methods to diagnose bladder outlet obstruction. Those methods were divided into uroflowmetry condom-catheter method, penile cuff method and Doppler ultrasonography urodynamics. Each method has been described and discussed in terms of its role in adding information to the diagnostic work-up for bladder outlet obstruction.

Conclusions

Pressure flow studies still remain the gold standard for assessing bladder outlet obstruction. However non-invasive urodynamics is a promising branch. Probably the most reliable information is given by the association of numerous methods together.

Age and volume dependent normal frequency volume charts for healthy males

PURPOSE

We report age and voided volume stratified normal values for voiding diary parameters, including urine production, in a uniform, nonreferred population of 935 healthy male volunteers.

MATERIALS AND METHODS

A total of 935 volunteers kept a 3-day voiding diary and also recorded the time of going to bed and getting up. Additionally, prostate volume was measured using transabdominal ultrasound and the maximum free flow rate was measured with a rotating disc flowmeter. From the diaries we calculated median voided volume and the mean number of voids during the day and night. We also calculated mean urine production in ml per hour during the day and night by assuming constant production between voids.

RESULTS

Volunteers voided a median volume of 220 ml 6 times daily and 0.5 times nightly. They produced 83 ml urine per hour during the day and 48 ml per hour during the night. The median maximum flow rate was 16 ml per second and median prostate volume was 31 ml. All diary parameters, free flow rate and prostate volume depended significantly on International Prostate Symptom Score. However, all parameters except urine production during the day depended significantly on age and all except prostate volume depended significantly on voided volume.

CONCLUSIONS

Values in a subgroup of 788 volunteers with an International Prostate Symptom Score of 10 or less may be considered normal for male voiding diary parameters. Age and voided volume stratified normal values were also derived.

Is it possible to improve elderly male bladder function by having them drink more water? A randomized trial of effects of increased fluid intake/urine output on male lower urinary tract function

OBJECTIVES

Several animal studies have shown that bladder performance improves as a result of diuresis. Whether increased urine output also has beneficial effects on elderly male bladder function and lower urinary tract symptoms is unknown.

METHODS

We performed a randomized placebo-controlled trial of 141 men, 55 to 75 years of age, with moderate lower urinary tract symptoms. The experimental group drank 1.5 L of extra water daily. The control group consumed one tablespoon of placebo syrup daily. After 6 months, we evaluated bladder contractility, voided volumes, and the severity of lower urinary tract symptoms. The actual increase in water consumption was measured using the deuterium urine dilution method.

RESULTS

Water consumption in the intervention group increased by 359 mL (95% confidence interval [CI] 171 to 548) per 24 hours compared with the control group. At 6 months, no statistically significant effect was found in the maximal flow rate (0.9 mL/s, 95% CI -0.4 to 2.2) compared with placebo. A statistically significant effect was found for bladder pressure (20 cm H2O, 95% CI 6 to 34) and bladder wall stress (1.9 N/cm2, 95% CI 0.3 to 3.5). In addition, it showed that the experimental group had greater maximal (44 mL, 95% CI -1 to 90) and average (26 mL, 95% CI 1 to 51) voided volumes per urination. The subjective effect parameters improved in both groups, but no statistically significant differences were found between the two groups.

CONCLUSIONS

It seems possible to improve some aspects of male bladder function by drinking more water. However, the effects are too small to be clinically relevant.

Development of a CFD urethral model to study flow-generated vortices under different conditions of prostatic obstruction

A novel, non-invasive method to diagnose bladder outlet obstruction involves the recording of noise with a contact microphone pressed against the perineum (between anus and scrotum). This noise results from flow-generated vortices caused by prostatic obstruction. We developed a computational fluid dynamic (CFD) urethral model including urethral geometry to study the relation between generated noise and the degree of obstruction. This model comprised a bladder, bladder neck, prostate and urethra. Calculations were carried out at four bladder pressures, five degrees of obstruction and three obstruction shapes. For each of the sixty simulations, the velocity and pressure distributions along the urethra were calculated including wall shear stresses to localize flow transition from disturbed to normal. Negative pressures at the obstruction outlet induced recirculation of flow. The location of transition was independent of the applied bladder pressure, but it depended primarily on the degree and secondarily on the shape of the obstruction. Based on the presented results, we hypothesize that the location of the maximum amplitude of perineal noise mainly depends on the degree and shape of the prostatic obstruction. Our future aim is to test our hypothesis in male patients and to extend the presented model to 3D with a viscoelastic urethral wall to calculate the fluid-wall interaction.

Epidemiological Aspects of Recruitment of Male Volunteers for Non-Invasive Urodynamics

INTRODUCTION

We studied epidemiological aspects of recruitment of volunteers for a non-invasive urodynamic study.

MATERIALS AND METHODS

9,236 volunteers were invited by 20 general practitioners (GPs), using two different recruitment methods, i.e. by mail only, or during a subsequent visit to the GP's office. Factors influencing the response rates were analyzed. We also tested how much the recruited population of volunteers differed from the general population, by comparing it to another, proven representative study carried out earlier in 1,662 subjects.

RESULTS

In the recruited population the prostate volumes were not significantly different from the proven representative study, but the symptom score was statistically significantly higher, although the difference was so small it may be called clinically irrelevant. Recruitment of volunteers in two steps, i.e. asking them first to visit the GP's office, and inviting them there to visit the outpatient clinic, rather than directly inviting them (in writing) to the clinic seemed to lead to a higher response, although this effect could not be statistically discriminated from the difference in response rates between GPs.

CONCLUSION

The population recruited was not urologically different from the general population. The response depended on age, being highest around the age of 60, and increased with social economic status. It also depended on the GP who recruited the subjects, and/or on the recruitment method.

Noninvasive methods of diagnosing bladder outlet obstruction in men. Part 2: Noninvasive urodynamics and combination of measures

PURPOSE

Many methods have been suggested to diagnose bladder outlet obstruction, as defined by the gold standard of pressure flow studies. Difficulty arises when comparing completely different methods of diagnosing bladder outlet obstruction. A comprehensive review of the literature on the different methods used to diagnose bladder outlet obstruction by noninvasive means was performed with a view to allow such a comparison.

MATERIALS AND METHODS

A MEDLINE search was done of the published literature covering until the end of 2004 on noninvasive methods, including single measure and combinations of measures, to diagnose bladder outlet obstruction. A direct comparison of all of the different methods was made using the sensitivity, specificity, likelihood ratio, and pretest and posttest probability of diagnosing bladder outlet obstruction for each test. For many techniques these values were calculated from the data presented in the article.

RESULTS

A multitude of methods has been applied to diagnose bladder outlet obstruction. Broadly the methods were divided into nonurodynamic and noninvasive urodynamic methods. Nonurodynamic methods were considered in part 1 of the review. Part 2 considered noninvasive urodynamic techniques, such as uroflowmetry, the penile cuff, the condom method and Doppler urodynamics. A combination of single measures was also considered and the relative merits of these approaches were discussed.

CONCLUSIONS

A combination of noninvasive urodynamics and ultrasound derived measures provide promising methods of diagnosing bladder outlet obstruction. However, pressure flow studies still remain the gold standard for assessing bladder outlet obstruction.

[Non-invasive urodynamics in male patient]

PURPOSE

Pressure-flow studies are currently recognized as the criterion standard to quantify urethral obstruction and its consequence on detrusor contractility. These tests have some disadvantages: they are invasive, time-consuming and expensive and entail risk of disease for the patient. Less invasive methods have been proposed to give the same results without the disadvantages. In this study, we conducted a critical analysis of the devices and techniques and their results.

METHOD

After a brief reminder of the general behavior of the flow in an obstructed urethra, we describe the main non-invasive techniques: penile urethral compression-release (PCR), cuffs, and condoms. Using the VBN method, we tried to quantify data from these techniques to specify the relation with the usual parameters of bladder outlet obstruction.

RESULTS

In the absence of brisk change of the flow rate, the voiding phases are easily analyzed. With minor corrections, recorded external or cuff pressures could be used in the ICS nomogram; unfortunately, these pressures are greatly modified by perturbations of the nervous control. The spike of flow (due to urine storage in the urethra) observed at resumption of flow after each interruption presents mathematical difficulties for quantitative and reliable modeling but could give a consistent empirical interpretation.

CONCLUSION

Of the reported non-invasive tests, all except PCR have an important instrumental heaviness and induce strong perturbations of the nervous control. If they cannot allow an accurate quantification of urethral obstruction and detrusor contractility, they could allow for classification of benign prostatic hypertrophy (BPH) patients. Despite the mathematical problems set by the theory of spikes, the empirical use of the spikes amplitude could perhaps be clinically useful.

Bladder volume sensitivity of isovolumetric intravesical pressure

AIMS

Recently, methods have been introduced for non-invasively measuring the isovolumetric bladder pressure. This pressure can also be measured invasively using a stop test. In itself, the isovolumetric pressure is a measure of urinary bladder contractility, by combining it with maximum urinary flow rate it can be used to diagnose infravesical obstruction. We have studied the (possible) volume dependence of this pressure in order to enhance the accuracy of this type of measurements and to explore its physiological background and possible diagnostic relevance.

MATERIALS AND METHODS

In 1,020 healthy subjects, recruited for an ongoing longitudinal study of changes in bladder contractility secondary to prostatic enlargement, we measured the isovolumetric bladder pressure using the condom catheter method. In each subject, voiding was repeatedly interrupted. The resulting pressure-volume relations were normalized and averaged.

RESULTS AND CONCLUSIONS

There is an optimum bladder volume for isovolumetric pressure measurements, averaging 264 +/- 122 ml (mean +/- SD). Measurements should be taken at or above the optimum volume. At volumes below the optimum volume, the pressure decreases by approximately 5% for each 10% of volume decrease. At bladder volumes smaller than 247 ml pressure readings in 50% of subjects are suboptimal. The optimum volume for isovolumetric pressure generation is only marginally related to voiding diary parameters. Probably it represents mechanical properties of the bladder, whereas voiding diary parameters more likely represent neurophysiological properties. However, the optimum volume does not reflect the optimum (smooth) muscle length for force generation of the bladder wall: during normal voiding bladder smooth muscle always operates at a suboptimal length for force generation.

Prostate volume ultrasonography: the influence of transabdominal versus transrectal approach, device type and operator

OBJECTIVES

We conduct a longitudinal non-invasive study of changes in urinary bladder contractility secondary to benign prostatic enlargement. In that study, the prostate volume is estimated by transabdominal ultrasonography. The accuracy of those measurements was verified by comparison of transabdominal to transrectal stepwise planimetric ultrasonography as the gold standard. Also, two different transabdominal devices used were compared, and the influence of different operators was studied.

MATERIALS & METHODS

Two series of measurements in 100 patients each were done. In the first series, transabdominal and transrectal sonography were pairwise compared in each patient. In the second series, transabdominal measurements were done with two devices (a hospital Aloka SSD-1700 and a portable Aloka SSD-900). Transrectal scannings were done by three investigators whilst all transabdominal scannings were done by one. Regression graphs, ratio plots and statistical analyses of the data quantified the reproducibility of different methods, observers and device types.

RESULTS

In the transrectal-transabdominal series of prostate volume measurements (in cm3), the Pearson correlation coefficient was 0.84 (p < 0.001), the mean of the means was 51.8 +/- 23.0 (mean +/- S.D.), and the mean of the differences was 1.0 +/- 1.4. In the series with two devices, the Pearson correlation coefficient was 0.73 (p < 0.001), the mean of the means was 31.0 +/- 10.9, and the mean of the differences was 1.0 +/- 1.3.

CONCLUSION

No statistically significant differences were found between the transabdominal- transrectal ultrasonography, two different transabdominal devices nor between different observers. However, for those using these measurements in everyday clinical practice, it is worth to point out that in our data a transabdominal scan and a transrectal scan in the same patient, on the same day, differed more than 30% in one fourth of the patients and that two transabdominal scans in the same patient (with two different devices, on two different days) differed more than 30% in every fifth patient.

Correlation of non-invasive urodynamics with International Prostate Symptom Score (IPSS) and prostate volume

AIM

To study the correlation between non-invasive urodynamic data, the International Prostate Symptom Score (IPSS) and the prostate volume.

MATERIALS AND METHODS

Data of 667 healthy volunteers participating in a longitudinal study of changes in urinary bladder contractility secondary to BPE were analyzed. The prostate volume was assessed by transabdominal ultrasonography. Uroflowmetry followed to verify if a minimum free flow rate of 4.5 ml/sec could be achieved. While (re)filling the bladder by drinking, the subjects completed the Dutch version of the IPSS. Next, the bladder pressure was non-invasively measured using the condom catheter method. The urethral resistance (URR) was calculated from the maximum condom pressure and the maximum free flow rate.

RESULTS

The IPSS ranged from 0 to 29, (6.1 +/- 4.8) (mean +/- SD), whereas the prostate volumes ranged from 8 to 140 cm3, (34 +/- 18). Twenty eight percent (185/667) of the subjects had a non-invasively quantified high URR and a significantly higher IPSS (7.3 +/- 5.2) than those with a low URR (IPSS (5.7 +/- 4.6)), Mann-Whitney U-test: P < 0.001. The IPSS and the URR were significantly correlated, Spearman's rho (rho) = 0.20, P < 0.001. A significant difference between the prostate volumes, 36 +/- 21 cm3 in the high URR versus 33 +/- 17 cm3 in the low URR group, was not found, P = 0.18.

CONCLUSIONS

A weak though statistically significant correlation was found between the non-invasively quantified URR and the IPSS. This suggests that an elevated resistance is a necessary, but not a sufficient condition for lower urinary tract symptoms (LUTS). No correlation was found between the URR and the prostate volume.

Comparison of repeatability of non-invasive and invasive urodynamics

AIMS

We have developed a method for the non-invasive measurement of urinary bladder pressure, and we apply this method in a longitudinal study of changes in bladder contractility in response to prostatic enlargement. In each volunteer in this study, we measure the bladder pressure twice. In the present study we have used this data to compare the repeatability of the non-invasive method to that of pressure-flow studies in a comparable population of patients.

METHODS

Difference plots were made of non-invasive bladder pressure measurements in 457 volunteers and of pressure-flow studies in a comparable population of 397 male patients. To compare the repeatability of two different methods for clinical measurement, the standard deviation of differences between repeated measurements in one individual needs to be normalised. Often a normalisation by dividing by the mean is done. We show that that normalisation may lead to erroneous results. We have normalised the standard deviations by dividing by the difference between the 97.5th and 2.5th percentile of the mean of the two observations in each subject.

RESULTS

Normalised repeatability of the non-invasive method was 0.15, that of the various parameters derived from the pressure-flow studies varied from 0.11 to 0.22.

CONCLUSIONS

We conclude that the repeatability of the tested non-invasive urodynamic method is comparable to, or slightly better than, that of pressure-flow studies. We further conclude that normalising standard deviations of differences by dividing by the difference between the 97.5th and 2.5th percentile of the mean is a suitable method to compare the repeatability of different methods for clinical measurement.