Non-invasive measurement of bladder pressure using an external catheter

The Use of Urodynamics Assessment Before the Surgical Treatment of BPH

Lower urinary tract symptoms (LUTS) are a common problem in men especially with aging. The International Continence Society (ICS) revealed an overall prevalence of LUTS of about two-thirds of men age 40 years and above. The treatment approach depends on accurate determination of the underlying etiology. LUTS is not unique to benign prostate enlargement (BPE) and can be secondary to other causes. In the era where quality of care is important, accurate diagnosis and counseling to meet patients' expectations is of extreme paramount. Thus, proper assessment of patients who present with BPE and LUTS should be an important part of the work up process. Accurate diagnosis and identification of the cause will help to improve quality of treatment, optimize counseling, and improve treatment outcomes. Pressure flow urodynamic studies (PFUDs) are not only important tools that help to identify the underlying causes of LUTS; it is considered the "gold standard" for diagnosis of bladder outlet obstruction (BOO) in patients with enlarged prostate [1, 2]. However, there is a continuous debate on the value of using PFUDs and its association with improved outcomes.

Dependence of ultrasound decorrelation on urine scatter particle concentration for a non-invasive diagnosis of bladder outlet obstruction

AIMS

To develop a non-invasive method to diagnose Bladder Outlet Obstruction (BOO) based on decorrelation of subsequently acquired UltraSound (US) data of urinary flow, we studied the influence of scatter particle concentration on the decorrelation process in urethra models using both aqueous solutions of scattering particles and urine samples.

METHODS

A tissue mimicking urethra model made from PolyVinyl Alcohol (PVA) solution was infused with seven aqueous solutions containing different particle concentrations at a constant flow rate value of 10 ml/sec. The average correlation coefficients between subsequent US images were calculated and plotted as a function of particle concentration. This procedure was also applied to stepwise diluted urine samples from nine healthy volunteers. An inversely exponential curve was fitted to the experimental data to estimate the scatter particle concentration in the urine samples.

RESULTS

The average correlation values between subsequent US images increased with the particle concentration. The morning urine samples contained an appropriate number of scattering particles to make clinical application of the decorrelation method possible. The fitted correlation curves made an estimation of urine particle concentration possible.

CONCLUSION

The results of this study show that morning urine is suitable for US decorrelation without correcting for differences in particle concentration.

Application of guidelines to the evaluation of the male patient with urgency and/or incontinence

PURPOSE OF REVIEW

To review and evaluate the evidence from contemporary evidence-based guidelines regarding the assessment of men with urinary urgency and/or incontinence.

RECENT FINDINGS

There are a number of evidence-based guidelines which describe the pathways for assessing men with the symptoms of urgency and/or incontinence. We summarize the conclusions of the European Association of Urology, American Urological Association and National Institute of Clinical Excellence guidelines.

SUMMARY

All guidelines recommend a directed history, examination (including digital rectal examination), urinalysis and bladder diary as being essential in the assessment of men with lower urinary tract symptoms, although there are no high levels of evidence studies to support this. Creatinine estimation and prostate-specific antigen are recommended in selected groups of men, the latter after appropriate counselling. Uroflowmetry with postvoid residual assessment is recommended for at specialist assessment. Pad tests may be useful to quantify leakage. Ultrasound assessment of prostatic size and protrusion into the bladder base may be useful. Cystometry is recommended for men considering prostatic surgery, although there is a poor level of evidence underpinning this. Noninvasive surrogates for cystometry, such as penile plethysmography, lack sufficient evidence to allow recommendations to be made.

Estimation of urinary flow velocity in models of obstructed and unobstructed urethras by decorrelation of ultrasound radiofrequency signals

The feasibility of estimating urinary flow velocity from the decorrelation of radiofrequency (RF) signals was investigated in soft tissue-mimicking models of obstructed and unobstructed urethras. The decorrelation was studied in the near field, focal zone and far field of the ultrasound beam. Furthermore, the effect of beam width was investigated. The results of this study suggest that it is feasible to estimate flow velocity in models of the urethra by quantifying the decorrelation of RF ultrasound signals. The decorrelation slope increased more rapidly and more linearly with increasing velocity in the focal zone than in the near and far field. A preliminary example of an in vivo measurement in a healthy volunteer illustrated that this method has potential for clinical use in the future.

Detrusor underactivity and the underactive bladder: a new clinical entity? A review of current terminology, definitions, epidemiology, aetiology, and diagnosis

CONTEXT

Detrusor underactivity (DU) is a common cause of lower urinary tract symptoms (LUTS) in both men and women, yet is poorly understood and underresearched.

OBJECTIVE

To review the current terminology, definitions, and diagnostic criteria in use, along with the epidemiology and aetiology of DU, as a basis for building a consensus on the standardisation of current concepts.

EVIDENCE ACQUISITION

The Medline and Embase databases were searched for original articles and reviews in the English language pertaining to DU. Search terms included underactive bladder, detrusor underactivity, impaired detrusor contractility, acontractile detrusor, detrusor failure, detrusor areflexia, raised PVR [postvoid residual], and urinary retention. Selected studies were assessed for content relating to DU.

EVIDENCE SYNTHESIS

A wide range of terminology is applied in contemporary usage. The only term defined by the standardisation document of the International Continence Society (ICS) in 2002 was the urodynamic term detrusor underactivity along with detrusor acontractility. The ICS definition provides a framework, considering the urodynamic abnormality of contraction and how this affects voiding; however, this is necessarily limited. DU is present in 9-48% of men and 12-45% of older women undergoing urodynamic evaluation for non-neurogenic LUTS. Multiple aetiologies are implicated, affecting myogenic function and neural control mechanisms, as well as the efferent and afferent innervations. Diagnostic criteria are based on urodynamic approximations relating to bladder contractility such as maximum flow rate and detrusor pressure at maximum flow. Other estimates rely on mathematical formulas to calculate isovolumetric contractility indexes or urodynamic "stop tests." Most methods have major disadvantages or are as yet poorly validated. Contraction strength is only one aspect of bladder voiding function. The others are the speed and persistence of the contraction.

CONCLUSIONS

The term detrusor underactivity and its associated symptoms and signs remain surrounded by ambiguity and confusion with a lack of accepted terminology, definition, and diagnostic methods and criteria. There is a need to reach a consensus on these aspects to allow standardisation of the literature and the development of optimal management approaches.

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.

Review of invasive urodynamics and progress towards non-invasive measurements in the assessment of bladder outlet obstruction

OBJECTIVE

This article defines the need for objective measurements to help diagnose the cause of lower urinary tract symptoms (LUTS). It describes the conventional techniques available, mainly invasive, and then summarizes the emerging range of non-invasive measurement techniques.

METHODS

This is a narrative review derived form the clinical and scientific knowledge of the authors together with consideration of selected literature.

RESULTS

Consideration of measured bladder pressure urinary flow rate during voiding in an invasive pressure flow study is considered the gold standard for categorization of bladder outlet obstruction (BOO). The diagnosis is currently made by plotting the detrusor pressure at maximum flow (p(detQmax)) and maximum flow rate (Q(max)) on the nomogram approved by the International Continence Society. This plot will categorize the void as obstructed, equivocal or unobstructed. The invasive and relatively complex nature of this investigation has led to a number of inventive techniques to categorize BOO either by measuring bladder pressure non-invasively or by providing a proxy measure such as bladder weight.

CONCLUSION

Non-invasive methods of diagnosing BOO show great promise and a few have reached the stage of being commercially available. Further studies are however needed to validate the measurement technique and assess their worth in the assessment of men with LUTS.

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.

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.

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.

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.

Noninvasive Techniques for the Measurement of Isovolumetric Bladder Pressure

PURPOSE

A total of 184,000 prostatectomies were performed in the United States in 2000 for the relief of presumed bladder outlet obstruction. However, it has been reported that prostatectomy using current indications fails to bring about symptomatic improvement in approximately one-fourth of patients. Pressure flow studies are currently recognized as the gold standard for the diagnosis of bladder outlet obstruction. However, these studies are associated with a number of disadvantages. They are time consuming, invasive and expensive, and carry some morbidity for the patient. It has been suggested that the use of pressure flow studies should be mandatory before surgery. The invasive nature of this test limits its application, and a variety of noninvasive methods have been suggested to circumvent the need for conventional urodynamics.

MATERIALS AND METHODS

We conducted a MEDLINE search of the published literature on the use of noninvasive techniques to measure bladder pressure.

RESULTS

Two promising techniques involve the noninvasive measurement of isovolumetric detrusor pressure. The first of these methods uses an external condom catheter and the second an inflatable cuff around the penis. Both of these methods rely on the interruption of urinary flow and the measurement of the bladder pressure transmitted along the fluid column between bladder and site of urethral occlusion. An alternative strategy analyzes flow patterns following compression and release of the urethra during voiding.

CONCLUSIONS

Of the methods reported the penile cuff, which is inflated during voiding, or the penile squeeze technique, which infers bladder pressure from flow patterns, would seem the most likely to be clinically useful. A noninvasive measure of bladder pressure, allied to a free flow rate, would give a useful adjunct to the assessment of men with lower urinary tract symptoms.

Development of a non-invasive strategy to classify bladder outlet obstruction in male patients with LUTS

To diagnose bladder outlet obstruction in male patients with lower urinary tract symptoms (LUTS), it is necessary to measure the bladder pressure via a transurethral (or suprapubic) catheter. This procedure incurs some risk of urinary tract infection and urethral trauma and is sometimes painful to the patient. We developed an external condom catheter to measure non-invasively the bladder pressure and developed a strategy to classify bladder outlet obstruction (BOO) based on this measurement. Seventy-five patients with a wide range of urological diagnoses underwent a pressure-flow study followed by a non-invasive study. We tested five different strategies to classify the patients using the provisional International Continence Society (ICS) method for definition of obstruction as the gold standard. Leakage of the external catheter occurred in eight (40%) of the first 20 tested patients. In the remaining 55 patients, only five (9%) of the measurements failed because of leakage. Of the 75 patients, 56 were successfully tested non-invasively. According to the ICS nomogram, the PFS showed that 22 of these patients were non-obstructed, 12 patients were equivocal, and 22 patients were obstructed. Ten of these 56 patients strained, and we found that the relatively high abdominal pressures in these patients were not reflected in the externally measured bladder pressure. Of the remaining 46 patients, 12 of 13 non-obstructed patients and 30 of 33 combined equivocal and obstructed patients could be correctly classified. We developed a simple, non-invasive classification strategy to identify BOO in those male patients who did not strain during voiding.

The variable outflow resistance catheter: a new method to measure bladder pressure noninvasively

PURPOSE

In a previous study an external condom catheter was used to measure noninvasively bladder pressure during interruption of the flow rate. The pressure increase in the condom sometimes caused a sphincter contraction that made bladder pressure measurement unreliable. Therefore, we developed a new variable outflow resistance catheter to measure noninvasively bladder pressure without interrupting the flow rate.

MATERIALS AND METHODS

The new catheter consists of an incontinence condom connected to a set of various outflow tubes and a pressure transducer. A remotely controlled pneumatic valve was fitted over each tube to interrupt flow through it. We measured isovolumetric pressure, maximum flow rate, and pressure and flow rates at various outflow resistances in 9 healthy male volunteers.

RESULTS

We derived a mathematical equation to estimate isovolumetric pressure from the pressure and flow rate values measured at various outflow resistances. The difference in the estimated and truly measured mean isovolumetric pressures plus or minus standard deviation was 0 +/- 6 cm. water.

CONCLUSIONS

The new variable outflow resistance catheter may be used to measure isovolumetric bladder pressure noninvasively without interrupting the flow rate. It has been previously shown that a combination of this pressure and a separately measured maximum flow rate may be used to diagnose bladder outlet obstruction noninvasively.