Causes for variability in repeated pressure-flow measurements

Development and Validation of a Deep Learning System for Sound-based Prediction of Urinary Flow

BACKGROUND

Uroflowmetry remains an important tool for the assessment of patients with lower urinary tract symptoms (LUTS), but accuracy can be limited by within-subject variation of urinary flow rates. Voiding acoustics appear to correlate well with conventional uroflowmetry and show promise as a convenient home-based alternative for the monitoring of urinary flows.

OBJECTIVE

To evaluate the ability of a sound-based deep learning algorithm (Audioflow) to predict uroflowmetry parameters and identify abnormal urinary flow patterns.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective open-label study, 534 male participants recruited at Singapore General Hospital between December 1, 2017 and July 1, 2019 voided into a uroflowmetry machine, and voiding acoustics were recorded using a smartphone in close proximity. The Audioflow algorithm consisted of two models-the first model for the prediction of flow parameters including maximum flow rate (Q_max), average flow rate (Q_ave), and voided volume (VV) was trained and validated using leave-one-out cross-validation procedures; the second model for discrimination of normal and abnormal urinary flows was trained based on a reference standard created by three senior urologists.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Lin's correlation coefficient was used to evaluate the agreement between Audioflow predictions and conventional uroflowmetry for Q_max, Q_ave, and VV. Accuracy of the Audioflow algorithm in the identification of abnormal urinary flows was assessed with sensitivity analyses and the area under the receiver operating curve (AUC); this algorithm was compared with an external panel of graders comprising six urology residents/general practitioners who separately graded flow patterns in the validation dataset.

RESULTS AND LIMITATIONS

A total of 331 patients were included for analysis. Agreement between Audioflow and conventional uroflowmetry for Q_max, Q_ave, and VV was 0.77 (95% confidence interval [CI], 0.72-0.80), 0.85 (95% CI, 0.82-0.88) and 0.84 (95% CI, 0.80-0.87), respectively. For the identification of abnormal flows, Audioflow achieved a high rate of agreement of 83.8% (95% CI, 77.5-90.1%) with the reference standard, and was comparable with an external panel of six residents/general practitioners. AUC was 0.892 (95% CI, 0.834-0.951), with high sensitivity of 87.3% (95% CI, 76.8-93.7%) and specificity of 77.5% (95% CI, 61.1-88.6%).

CONCLUSIONS

The results of this study suggest that a deep learning algorithm can predict uroflowmetry parameters and identify abnormal urinary voids based on voiding sounds, and shows promise as a simple home-based alternative to uroflowmetry in the management of patients with LUTS.

PATIENT SUMMARY

In this study, we trained a deep learning-based algorithm to measure urinary flow rates and identify abnormal flow patterns based on voiding sounds. This may provide a convenient, home-based alternative to conventional uroflowmetry for the assessment and monitoring of patients with lower urinary tract symptoms.

A new nomogram of urinary flow rate and volume based on multiple measurements per healthy adult Japanese men using a portable uroflowmeter (P-Flowdiary®)

BACKGROUND

To develop a nomogram of urinary volume and flow based on the data of Japanese men without lower urinary tract symptoms and multiple flows per participant whose characteristics were clear.

METHODS

Overall, 101 Japanese male volunteers without lower urinary tract symptoms aged between 20 and 59 years were enrolled. A portable uroflowmeter (P-Flowdiary®) was used to record urinary information (flow rate and volume) for 2 successive days. The model (quadratic, linear, or logarithmic regression) most fit for the relationship between maximum flow rate and voided volume was determined. The maximum flow rate at > 150 mL was compared among the 20-29-, 30-39-, 40-49-, and 50-59-year age groups. Nomograms appropriate for the age groups were created.

RESULTS

The mean age, International Prostate Symptom Score, and Overactive Bladder Symptom Score were 38.5 years, 0.42, and 0.24, respectively. The quadratic regression model was the most fit because its mean coefficient determination was 0.93 ± 0.06. The mean maximum flow rate was significantly lower in the 50-59-year age group (21.8 ± 5.05 mL/s, P < 0.01) than in the younger groups (24.14 ± 4.94, 24.05 ± 6.99, and 24.64 ± 5.72 mL/s). The 2 nomograms are Y = 28.99 {1 - exp(- 0.01 × X)} and Y = 25.67 {1 - exp(- 0.01 × X)} for the 20-49- and 50-59-year age groups, respectively.

CONCLUSIONS

The nomogram can predict maximum flow rate based on voided volume in Japanese men aged 20-59 years without lower urinary tract symptoms.

Comparison of Self-Conducted and Assistant-Supervised Uroflowmetry Methods

Objective

This study aims to compare the results and patient satisfaction scores between uroflowmetry performed under the patient's control and assistant-supervised conventional uroflowmetry.

Methods

A total of 120 patients who had previous experience with uroflowmetry were included in the study. Patients were evaluated in two even groups of 60 patients each - those not receiving medical treatment (group 1) and those receiving medical treatment (group 2). Maximum flow rate (Qmax), average flow rate (Qave), voided volume, voiding time, post-void residual volume (PVR), and patient satisfaction survey scores were compared between the two separate uroflowmetry methods.

Results

There was a significant difference between assistant-supervised and self-conducted uroflowmetry in terms of Qmax, Qave, voiding time, and patient satisfaction scores. While comparing all patients, no significant difference was found in terms of PVR and voiding volume values. There was a significant difference in Qave, Qmax, PVR, and voiding time in both assistant-supervised and self-conducted uroflowmetry. As for voided volume, there was no significant difference between the groups in either procedure. When groups were evaluated within themselves, in group 1, there was a significant difference in voided volume, Qave, and PVR, while there was no significant difference in Qmax and voiding time. In Group 2, there was a significant difference in voided volume, Qave, and PVR, although there was no significant difference in Qmax and voiding time.

Conclusion

Maximum urine flow rate and mean urine flow rate measured by self-conducted uroflowmetry are higher than assistant-supervised (conventional) uroflowmetry, which can ensure patient privacy.

Mobile sonouroflowmetry using voiding sound and volume

Uroflowmetry (UF) is a common clinic-based non-invasive test to diagnose Lower Urinary Tract Dysfunction (LUTD). Accurate home-based uroflowmetry methods are needed to conveniently conduct repeated uroflowmetries when patients are physiologically ready to urinate. To this end, we propose and evaluate a novel mobile sonouroflowmetry (SUF) method that estimates the urinary flow rate from a sound signal recorded using a mobile phone. By linearly mapping the total sound energy to the total voided volume, the sound energy curve is transformed to a flow rate curve allowing the estimation of the flow rate over time. An evaluation using data from 44 healthy young men showed high similarity between the UF and SUF flow rates with a mixed-effects model correlation coefficient of 0.993 and a mean root mean square error of 2.37 ml/s. Maximum flow rates were estimated with an average absolute error of 2.41 ml/s. Future work on mobile uroflowmetry can use these results as an initial benchmark for flow rate estimation accuracy.

Novel measurement tool and model for aberrant urinary stream in 3D printed urethras derived from human tissue

Background

An estimated 10% of male adults have split or dribbled stream leading to poor hygiene, embarrassment, and inconvenience. There is no current metric that measures male stream deviation.

Objective

To develop a novel method to measure spray in normal and abnormal anatomical conformations.

Design, setting, and participants

We developed a novel platform to reliably describe spray. We used cadaveric tissues and 3D Printed models to study the impact of meatal shape on the urinary stream. Cadaveric penile tissue and 3D printed models were affixed to a fluid pump and used to simulate micturition. Dye captured on fabric allowed for spray detection.

Outcome measurements and statistical analysis

Spray pattern area, deviation from normal location, and flowrates were recorded. Computational fluid dynamic models were created to study fluid vorticity.

Results and limitations

Obstructions at the penile tip worsened spray dynamics and reduced flow. Ventral meatotomy improved flowrate (p<0.05) and reduced spray (p<0.05) compared to tips obstructed ventrally, dorsally or in the fossa navicularis. 3D models do not fully reproduce parameters of their parent cadaver material. The average flowrate from 3D model was 10ml/sec less than that of the penis from which it was derived (p = 0.03). Nonetheless, as in cadavers, increasing obstruction in 3D models leads to the same pattern of reduced flowrate and worse spray. Dynamic modeling revealed increasing distal obstruction was correlated to higher relative vorticity observed at the urethral tip.

Conclusions

We developed a robust method to measure urine spray in a research setting. Dynamic 3D printed models hold promise as a methodology to study common pathologies in the urethra and corrective surgeries on the urine stream that would not be feasible in patients. These novel methods require further validation, but offer promise as a research and clinical tool.

A prototype non-invasive urodynamic test to estimate voiding reserve in normal adult males

Objective: To propose a prototype non-invasive test to estimate voiding reserve in normal adult men; identifying its feasibility, limitations, and initial results.

Subjects and methods: In all, 30 adult healthy male volunteers aged <40 years were included in the study. Initial free uroflowmetry was done with post-void residual urine volume (PVR) assessment using ultrasonography. The men were later asked to void into a uroflowmeter through a condom catheter attached to the glans penis and connected to an outflow tube with specific vertical heights (10, 20, 30, 40, 50 and 60 cm) on different days. The mean maximum urinary flow rate (Q_max) and PVR at each height were compared with the Q_max and PVR at the initial free uroflowmetry. The maximum height at which the Q_max and PVR remained normal was considered the normal voiding reserve for that age group.

Results: All the men completed the study without any complications. At zero level, the mean Q_max was 27.6 mL/s, which then dropped gradually to reach 17.8 mL/s at 60 cm, where still 83% of the men had a normal Q_max. The PVR was nil at zero level and started to exceed the normal range at 50 and 60 cm height (58 and 65.7 mL, respectively). So, the maximum height resistance at which the men could have a normal Q_max and normal PVR was 40 cm.

Conclusions: The use of the tube height-resistance test to assess voiding reserve is feasible, non-invasive and has no complications. A 40-cm height resistance can be considered a reference level that a young adult male should be tested against to estimate his voiding reserve.

Abbreviations: NPV: negative predictive value; P_detQ_max: maximum detrusor pressure at maximum urinary flow; PPV: positive predictive value; PVR: post-void residual urine volume; ROC: receiver operating characteristic

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.

Air filled, including "air-charged," catheters in urodynamic studies: does the evidence justify their use?

AIMS

Air filled catheters (AFCs) have been actively marketed for the past few years and in some geographic areas are widely used. However, as the scientific basis for introduction of this technology for pressure measurement in urodynamics was not clear, a study group examined the evidence.

METHODS

A search of the peer reviewed literature was carried out.

RESULTS

Four papers were identified, of which two were laboratory experiments and two were clinical papers, in female patients, that compared the pressures recorded by AFCs and those recorded using the traditional water filled catheters (WFCs). These data show that there are differences between the pressures measured by the two types of catheters. As yet, the reasons for these differences are not clear.

CONCLUSIONS

There should be further systematic laboratory and clinical research before AFCs can be recommended for routine clinical use. We would recommend that a professional worldwide multidisciplinary scientific society, such as the International Continence Society, should work with manufacturers and regulatory bodies to ensure that this urodynamic method is properly scientifically evaluated, in the wider interests of patient safety.

Evaluation of Voiding Parameters in Healthy Women Using Sound Analysis

OBJECTIVES

Sonouroflowmetry represents a novel method for estimating urinary flow parameters. The aim of this study was to compare the urinary flow parameters acquired using sonouroflowmetry with those of standard uroflowmetry in healthy female volunteers.

METHODS

Thirty-six healthy female volunteers (aged 25-54 years) were subjected to standard uroflowmetry. Simultaneously, subjects dialed a dedicated number on a mobile phone and kept recording until urination was finished. Sound data were analyzed and compared to the uroflowmetry data. Of 218 recordings, 183 were included in the final analysis. Thirty-four measurements were excluded for voided volume <150 mL or technical problems during the recording. A linear model was fitted to calculate the urinary flow parameters and the voided volume from data obtained by sonouroflowmetry. Subsequently the matching datasets of UF and SUF were compared with respect to flow time, voided volume, maximum (Q_max ) and average (Q_ave ) flow rate. Pearson's correlation coefficient (PCC) was used to compare parameters recorded by uroflowmetry with those calculated based on sonouroflowmetry recordings.

RESULTS

A strong correlation (PCC = 0.95) was noted between uroflowmetry recorded flow time and duration of the sonouroflowmetry sound signal. The voided volume measured by uroflowmetry showed a moderate correlation (PCC = 0.68) with the calculated area under the sonouroflowmetry curve. Q_max recorded using uroflowmetry and sonouroflowmetry recorded peak sound intensity showed a weak correlation (PCC = 0.38).

CONCLUSIONS

This study validates the basic concept of using sound analysis to estimate urinary flow parameters and voided volume.

Benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH), which causes lower urinary tract symptoms (LUTS), is a common diagnosis among the ageing male population with increasing prevalence. Many risks factors, both modifiable and non-modifiable, can increase the risk of development and progression of BPH and LUTS. The symptoms can be obstructive (resulting in urinary hesitancy, weak stream, straining or prolonged voiding) or irritative (resulting in increased urinary frequency and urgency, nocturia, urge incontinence and reduced voiding volumes), or can affect the patient after micturition (for example, postvoid dribble or incomplete emptying). BPH occurs when both stromal and epithelial cells of the prostate in the transitional zone proliferate by processes that are thought to be influenced by inflammation and sex hormones, causing prostate enlargement. Patients with LUTS undergo several key diagnostic investigations before being diagnosed with BPH. Treatment options for men with BPH start at watchful waiting and progress through medical to surgical interventions. For the majority of patients, the starting point on the treatment pathway will be dictated by their symptoms and degree of bother.

Comparison between uroflowmetry and sonouroflowmetry in recording of urinary flow in healthy men

OBJECTIVES

To evaluate the accuracy of sonouroflowmetry in recording urinary flow parameters and voided volume.

METHODS

A total of 25 healthy male volunteers (age 18-63 years) were included in the study. All participants were asked to carry out uroflowmetry synchronous with recording of the sound generated by the urine stream hitting the water level in the urine collection receptacle, using a dedicated cell phone. From 188 recordings, 34 were excluded, because of voided volume <150 mL or technical problems during recording. Sonouroflowmetry recording was visualized in a form of a trace, representing sound intensity over time. Subsequently, the matching datasets of uroflowmetry and sonouroflowmetry were compared with respect to flow time, voided volume, maximum flow rate and average flow rate. Pearson's correlation coefficient was used to compare parameters recorded by uroflowmetry with those calculated based on sonouroflowmetry recordings.

RESULTS

The flow pattern recorded by sonouroflowmetry showed a good correlation with the uroflowmetry trace. A strong correlation (Pearson's correlation coefficient 0.87) was documented between uroflowmetry-recorded flow time and duration of the sound signal recorded with sonouroflowmetry. A moderate correlation was observed in voided volume (Pearson's correlation coefficient 0.68) and average flow rate (Pearson's correlation coefficient 0.57). A weak correlation (Pearson's correlation coefficient 0.38) between maximum flow rate recorded using uroflowmetry and sonouroflowmetry-recorded peak sound intensity was documented.

CONCLUSIONS

The present study shows that the basic concept utilizing sound analysis for estimation of urinary flow parameters and voided volume is valid. However, further development of this technology and standardization of recording algorithm are required.

EAU Guidelines on the Assessment of Non-neurogenic Male Lower Urinary Tract Symptoms including Benign Prostatic Obstruction

CONTEXT

Lower urinary tract symptoms (LUTS) represent one of the most common clinical complaints in adult men and have multifactorial aetiology.

OBJECTIVE

To develop European Association of Urology (EAU) guidelines on the assessment of men with non-neurogenic LUTS.

EVIDENCE ACQUISITION

A structured literature search on the assessment of non-neurogenic male LUTS was conducted. Articles with the highest available level of evidence were selected. The Delphi technique consensus approach was used to develop the recommendations.

EVIDENCE SYNTHESIS

As a routine part of the initial assessment of male LUTS, a medical history must be taken, a validated symptom score questionnaire with quality-of-life question(s) should be completed, a physical examination including digital rectal examination should be performed, urinalysis must be ordered, post-void residual urine (PVR) should be measured, and uroflowmetry may be performed. Micturition frequency-volume charts or bladder diaries should be used to assess male LUTS with a prominent storage component or nocturia. Prostate-specific antigen (PSA) should be measured only if a diagnosis of prostate cancer will change the management or if PSA can assist in decision-making for patients at risk of symptom progression and complications. Renal function must be assessed if renal impairment is suspected from the history and clinical examination, if the patient has hydronephrosis, or when considering surgical treatment for male LUTS. Uroflowmetry should be performed before any treatment. Imaging of the upper urinary tract in men with LUTS should be performed in patients with large PVR, haematuria, or a history of urolithiasis. Imaging of the prostate should be performed if this assists in choosing the appropriate drug and when considering surgical treatment. Urethrocystoscopy should only be performed in men with LUTS to exclude suspected bladder or urethral pathology and/or before minimally invasive/surgical therapies if the findings may change treatment. Pressure-flow studies should be performed only in individual patients for specific indications before surgery or when evaluation of the pathophysiology underlying LUTS is warranted.

CONCLUSIONS

These guidelines provide evidence-based practical guidance for assessment of non-neurogenic male LUTS. An extended version is available online (www.uroweb.org/guidelines).

PATIENT SUMMARY

This article presents a short version of European Association of Urology guidelines for non-neurogenic male lower urinary tract symptoms (LUTS). The recommended tests should be able to distinguish between uncomplicated male LUTS and possible differential diagnoses and to evaluate baseline parameters for treatment. The guidelines also define the clinical profile of patients to provide the best evidence-based care. An algorithm was developed to guide physicians in using appropriate diagnostic tests.

The Immediate and 6-mo Reproducibility of Pressure–Flow Studies in Men with Benign Prostatic Enlargement

OBJECTIVES

Urodynamics is an objective method of diagnosing bladder outlet obstruction (BOO) in men. This study examined the immediate and 6-mo reproducibility of this investigation.

METHODS

Urodynamics was performed in men as part of a multinational, multicentre, double-blind, placebo-controlled drug trial. Each patient had two fill/void cycles both at baseline and 6 mo. The BOO index (BOOI) and bladder contractility index (BCI) were calculated for each cycle and data analysed to look for changes in immediate and 6-mo reproducibility between the two fill/void cycles.

RESULTS

A total of 114 patients had urodynamics at baseline. In the immediate term, although there was a small but statistical fall in both the BOOI and BCI, with cycle one figures greater than those in cycle two, 81% and 79% of patients remained in the same BOOI and BCI category, respectively. At 6 mo, the differences were not statistically different with 70% of patients remaining unchanged in their BOOI category in cycle one and 71% in cycle two; 65% remained unchanged in their BCI category in cycle one and 74% in cycle two. No patient with a BOOI > 65 changed category in the second investigation, and only 5 of 103 first cycles with a BOOI > or = 50 changed category to equivocal obstruction.

CONCLUSIONS

Urodynamics has good reproducibility when looking at the BOOI and BCI, indicating that a second study is not necessary in most patients and one investigation is sufficient for an accurate diagnosis on which treatment options can be based.

Variation in invasive and noninvasive measurements of isovolumetric bladder pressure and categorization of obstruction according to bladder volume

PURPOSE

We developed a noninvasive test that provides an estimate of isovolumetric bladder pressure by measuring the pressure required to interrupt voiding using controlled inflation of a penile cuff. We noted variation in serial measurements obtained during a single void and, therefore, we determined whether this represents variation in detrusor contraction strength, as predicted in previous studies, or measurement error.

MATERIALS AND METHODS

A total of 36 symptomatic men underwent simultaneous invasive and noninvasive pressure flow studies. Corresponding values of isovolumetric bladder pressure and cuff interruption pressure were recorded at each flow interruption and grouped according to bladder volume to calculate measurement error and bias at various points during a void. Individual variation in the 2 measurements across a range of normalized bladder volumes was then examined using ANOVA.

RESULTS

Cuff interruption pressure showed a consistent level of accuracy as an estimate of isovolumetric bladder pressure across a range of volumes. There were similar, statistically significant differences in isovolumetric bladder pressure and cuff interruption pressure recorded at specific volume increments with the highest values seen in the mid range and the lowest seen at lower bladder volumes (each p <0.01). When plotting, the maximum recorded value of cuff interruption pressure in each individual on our proposed noninvasive pressure flow nomogram provided the best diagnostic accuracy for obstruction.

CONCLUSIONS

This study shows that cuff interruption pressure varies in the expected manner with bladder volume and provides a consistent estimate of isovolumetric bladder pressure throughout a void. These data provide important guidance for interpreting noninvasive pressure flow studies and classifying obstruction on the proposed nomogram.

Polymorphisms in the alpha1A-adrenoceptor gene do not modify the short- and long-term efficacy of alpha1-adrenoceptor antagonists in the treatment of benign prostatic hyperplasia

OBJECTIVE To determine whether a common single nucleotide polymorphism (SNP) in the ADRA1A gene encoding the alpha(1A)-adrenoceptor modifies the short- and long-term efficacy of alpha(1)-adrenoceptor antagonists in the treatment of benign prostatic hyperplasia (BPH). PATIENTS AND METHODS For 254 patients with BPH and/or lower urinary tract symptoms who received alpha(1)-adrenergic antagonists for > or = 3 months, the ADRA1A genotype at position 1475 of the coding region was determined. The patients' short-term response to treatment was determined for four outcome measures, i.e. the International Prostate Symptom Score (IPSS), the IPSS quality-of-life score, peak urinary flow rate, and obstruction grade, stratified by genotype. Eventual BPH-related invasive therapy was used as the outcome for assessing the long-term response to treatment. Genetic variants at positions 834, 896, 898 and 1831 were too rare to be considered in the analysis. RESULTS There were no significant differences for the genotype strata in three of the four outcome measures. Patients with the CC genotype responded significantly better in quality-of-life perception than patients with the CT or TT genotype. There were also no significant differences in the risk of BPH-related invasive therapy among the three genotypes. CONCLUSIONS The 1475C-->T SNP in the ADRA1A gene does not modify the short- and long-term efficacy of alpha(1)-adrenoceptor antagonists for treating BPH. There was a small effect on perceived quality of life but this was not reflected in other variables that measured the treatment response more directly.

Are conventional pressure-flow measurements dependent upon filled volume?

OBJECTIVE

To determine, in a prospective study, whether detrusor pressure (p(det.Qmax)) and maximum urinary flow rate (Q(max)) measurements obtained after filling to maximum cystometric capacity (MCC) differ from those obtained with filling restricted to average voided volume (V(void)), as standard protocols for pressure flow studies (PFS) mandate bladder filling until the subject has a strong desire to void, which aids standardization but further divorces the test from real-life experience.

PATIENTS AND METHODS

After calculating the appropriate sample size, 84 patients attending for PFS with an adequately completed 3-day frequency-volume chart were recruited. Each underwent two consecutive PFS with filling to MCC and average V(void) in a random order, and measurements of p(det.Qmax) and Q(max) were compared. For men, the agreement for a diagnosis of obstruction between the tests was also assessed.

RESULTS

Complete data were obtained from 76 (90%) of the patients, with a mean (range) age of 64 (20-94) years. The mean (sd) difference between MCC and average V(void) was 134 (113) mL (P < 0.01). There were no significant differences between estimates of Q(max), at - 0.1 (3) mL/s (P = 0.75), and of p(det.Qmax), at - 1 (13) cmH(2)O (P = 0.91), obtained within each patient. For men there was 91% agreement (32 of 35) in the classification of obstruction.

CONCLUSIONS

Restriction of filling to the average V(void) during PFS allows a closer approximation to normal voiding and results in no clinically relevant change to the value of standard pressure-flow measurements or alters individual classification of obstruction.

The reproducibility of urodynamic findings in healthy female volunteers: Results of repeated studies in the same setting and after short-term follow-up

AIM

To assess the immediate (same testing period) and short-term (within 6 months) repeatability of urodynamic (UD) testing in asymptomatic healthy female volunteers.

MATERIALS AND METHODS

Twenty asymptomatic women with a mean age of 41.8 years (30-55) agreed to undergo a UD assessment which consisted of noninvasive uroflowmetry, post-void residual (PVR) measurement, medium-fill cystometry, and pressure flow study with perineal surface electromyographic (EMG) electrodes. The UDS evaluation was repeated immediately without removing the catheters (a two-fill and void study). Sixteen women returned for an identical UD assessment 1-5 months later. Immediate and short-term repeatability of UD parameters was assessed by calculating the coefficient of repeatability (COR).

RESULTS

The repeatability of certain parameters of immediate UD testing could not be calculated since there was an apparent influence of the first test on the second (i.e., an apparent accommodation noted in bladder filling volumes). Other immediate UD values (maximum flow, detrusor pressure at maximum flow, voided volume) had high COR values, as did all UD values on short-term testing, indicating relatively poor repeatability. Picking the 'best' pressure flow value (highest flow rate with accompanying detrusor pressure) did not consistently improve the COR values.

CONCLUSIONS

The lack of repeatability of UD studies likely stems from a combination of the true physiological fluctuations in bladder function and the inherent relative insensitivity of our instruments in conducting these testing. Knowledge of the limitations of current technology is essential in allowing us to better utilize these studies in evaluating our patients and further improving diagnostic strategies.

Weak correlation between bladder outlet obstruction and probability to void to completion

OBJECTIVES

To investigate the weak correlation between bladder outlet obstruction (BOO), as diagnosed using the provisional International Continence Society nomogram for the definition of BOO in men, and postvoid residual urine volume.

METHODS

The relationship between voiding to completion and several indexes for bladder outlet resistance and bladder contractility was studied in 131 pressure flow studies in male patients using multivariate logistic regression analysis.

RESULTS

The International Continence Society nomogram and the related BOO index weakly predict for postvoid residual urine volume (areas under the receiver operating characteristic curve 0.63 and 0.64, respectively). The BOO index primarily measures bladder outlet resistance. If the nomogram or BOO index is augmented with bladder contractility information, the postvoid residual urine volume can be predicted significantly better (eg, area under the receiver operating characteristic curve [0.89] for the combination of the BOO index and bladder contractility information).

CONCLUSIONS

The weak correlation between BOO and postvoid residual urine volume is related to the fact that emptying the bladder to completion depends on bladder contractility, as well as bladder outlet resistance. It is possible to estimate the probability to void to completion quite accurately on the basis of bladder outlet resistance and bladder contractility. We named this probability "relative bladder outlet resistance." A high probability of a postvoid residual urine volume may be assumed to indicate "relative BOO." By its very nature, the correlation between "relative BOO" and postvoid residual urine volume is good.