Effect of 6F urethral catheterization on urinary flow rates during repeated pressure-flow studies in healthy female volunteers

Voiding efficiency in children is significantly impaired by the presence of the urethral catheter during pressure-flow studies

BACKGROUND

Little is known about the effect of catheterization during pressure-flow studies (PFS) on voiding efficiency in children. Our objective was to determine the effect of urethral catheterization on Qmax and flow index (FI) during PFS compared to the free flow of uroflowmetry (UF).

METHODS

We retrospectively reviewed 63 consecutive children who underwent UF and PFS at our center on the same day (2019-2022). Voiding data was available for 46 patients. Patients first underwent a UF with full bladder, then PFS after urethral catheter insertion. Patients with urethral pathologies (n = 6), on clean intermittent catheterization (CIC) (n = 2) and with major comorbidities (n = 2) were excluded. Indications for UF/PFS were LUTS, recurrent UTIs, incontinence or neurosurgical pre-operative evaluation. Data was collected from the UF and the PFS and compared using paired t-test. The idealized Qmax and flow index (FI) were calculated for UF and PFS using the formulas described by Franco et al.: Male Qmax = 11.26 + 0.0701(TBC [total bladder capacity]) - 0.0000513(TBC); Female Qmax = 10.723 + 0.073(TBC) - 0.0000423(TBC), FI = Actual Qmax/Expected Qmax (Franco and et al., 2016; Franco et al., 2018; Franco and et al., 2016).

RESULTS

Median age was 7 years old (IQR 5-11). Twenty-one (40%) patients were male and 32 (60%) patients were female. Of the 53 patients, 3 boys and 4 girls (n = 7; 13%) were unable to void with the catheter in place during PFS but able to void after its removal. Of the remaining 46 cases, the Qmax during PFS was 5 mL/s slower than the Qmax recorded on the UF without catheter, representing a decrease of 29% (12.3 vs 17.3 mL/s; p < 0.0001). The impact of urethral catheter during PFS was more important in males vs females (Qmax decreased by 7.7 vs 3.3 mL/s, or 45 vs 19%). The mean FI during PFS was 44%, which was a 30% reduction compared to the 74% FI obtained with UF (p < 0.00001). In males, the FI decreased by 37% on PFS, whereas it decreased 26% in females, similar to the Qmax decrease.

CONCLUSIONS

Voiding efficiency, as assessed by Qmax and FI, is decreased during PFS compared to uroflow studies. Our data documents for the first time the impact of urethral catheterization on pediatric voiding efficiency. Abnormal flow rates and elevated PVRs should be used to guide patient management only if obtained by uroflow. Prospective validation comparing free flow with PFS studies will help characterize the impact of urethral catheter relative to bladder pathology, age, gender and catheter size used.

A Velocity-Based Approach to Noninvasive Methodology for Urodynamic Analysis

PURPOSE

To date, invasive urodynamic investigations have been used to define most terms and conditions relating to lower urinary tract symptoms. This invasiveness is almost totally due to the urethral catheter. In order to remove this source of discomfort for patients, the present study investigated a noninvasive methodology able to provide diagnostic information on bladder outlet obstruction or detrusor underactivity without any contact with the human body.

METHODS

The proposed approach is based on simultaneous measurements of flow rate and jet exit velocity. In particular, the jet exit kinetic energy appears to be strongly related to bladder pressure, providing useful information on the lower urinary tract functionality. We developed a new experimental apparatus to simulate the male lower urinary tract, thus allowing extensive laboratory activities. A large amount of data was collected regarding different functional statuses.

RESULTS

Experimental results were compared successfully with data in the literature in terms of peak flow rate and jet exit velocity. A new diagram based on the kinetic energy of the exit jet is proposed herein. Using the same notation as a Schäfer diagram, it is possible to perform noninvasive urodynamic studies.

CONCLUSION

A new noninvasive approach based on the measurement of jet exit kinetic energy has been proposed to replace current invasive urodynamic studies. A preliminary assessment of this approach was carried out in healthy men, with a specificity of 91.5%. An additional comparison using a small sample of available pressure-flow studies also confirmed the validity of the proposed approach.

Pressure Measurement in a Bladder Phantom Using Contrast-Enhanced Ultrasonography-A Path to a Catheter-Free Voiding Cystometrogram

OBJECTIVES

The long-term goal of this study is to investigate the efficacy of a novel, ultrasound-based technique called subharmonic-aided pressure estimation (SHAPE) to measure bladder pressure as a part of a cystometrogram (CMG) in a urodynamic test (ie, pressure-flow study). SHAPE is based on the principle that subharmonic emissions from ultrasound contrast microbubbles (MBs) decrease linearly with an increase in ambient pressure. We hypothesize that, using the SHAPE technique, we can measure voiding bladder pressure catheter-free. This is of importance because the CMG catheter, due to its space-occupying property and non-physiological effects, can undermine the reliability of the test during voiding and cause misdiagnosis. In this study, we tested this hypothesis and optimized the protocol in a controlled benchtop environment.

MATERIALS AND METHODS

A bladder phantom was designed and built, capable of simulating clinically relevant bladder pressures. Laboratory-made lipid-shelled MBs (similar in composition to the commercial agent, DEFINITY) was diluted in 0.9% normal saline and infused into the bladder phantom using the CMG infusion system. A typical simulated CMG consists of 1 filling and 4 post-filling events. During CMG events, the bladder phantom is pressurized multiple times at different clinically relevant levels (small, medium, and large) to simulate bladder pressures. Simultaneous with pressurization, MB subharmonic signal was acquired. For each event, the change in MB subharmonic amplitude was correlated linearly with the change in bladder phantom pressure, and the SHAPE conversion factor (slope of the linear fit) was determined. In doing so, a specific signal processing technique (based on a small temporal window) was used to account for time-decay of MB subharmonic signal during a simulated CMG.

RESULTS

A strong inverse linear relationship was found to exist between SHAPE and bladder phantom pressures for each of the CMG filling and post-filling events ( r2> 0.9, root mean square error < 0.3 dB, standard error <0.01 dB, and P < 0.001). SHAPE showed a transient behavior in measuring bladder phantom pressure. The SHAPE conversion factor (in dB/cm H 2 O) varied between filling and post-filling events, as well as by post-filling time. The magnitude of the SHAPE conversion factor tended to increase immediately after filling and then decreases with time.

CONCLUSIONS

Microbubble subharmonic emission is an excellent indicator of bladder phantom pressure variation. The strong correlation between SHAPE signal and bladder phantom pressure is indicative of the applicability of this method in measuring bladder pressure during a CMG. Our results suggest that different SHAPE conversion factors may be needed for different events during a CMG (ie, at different time points of a CMG). These findings will help us better protocolize this method for introduction into human subjects and allow us to take the next step toward developing a catheter-free voiding CMG using SHAPE.

Ultrasound Contrast Stability for Urinary Bladder Pressure Measurement

The goal of this study was to evaluate ultrasound contrast microbubbles (MB) stability during a typical cystometrogram (CMG) for bladder pressure measurement application using the subharmonic-aided pressure estimation technique. A detailed study of MB stability was required given two unique characteristics of this application: first, bulk infusion of MBs into the bladder through the CMG infusion system, and second, duration of a typical CMG which may last up to 30 min. To do so, a series of size measurement and contrast-enhanced ultrasound imaging studies under different conditions were performed and the effects of variables that we hypothesized have an effect on MB stability, namely, i) IV bag air headspace, ii) MB dilution factor, and iii) CMG infusion system were investigated. The results verified that air volume in intravenous (IV) bag headspace was not enough to have a significant effect on MB stability during a CMG. We also showed that higher MB dosage results in a more stable condition. Finally, the results indicated that the CMG infusion system adversely affects MB stability. In summary, to ensure MB stability during the entire duration of a CMG, lower filling rates (limited by estimated bladder capacity in clinical applications) and/or higher MB dosage (limited by FDA regulations and shadowing artifact) and/or the consideration of alternative catheter design may be needed.

Impact of urethral catheterization on uroflow during pressure-flow study

Objective

To investigate the impact of urethral catheterization on uroflow by comparing urodynamic parameters of free uroflowmetry versus pressure-flow study in adult patients with benign prostatic hyperplasia, female stress incontinence, lumbosacral spinal injury or spina bifida.

Methods

Each patient was required to perform pressure-flow study immediately following free uroflowmetry. Maximum flow rate (Q_max), average flow rate (Q_ave), voided volume (VV), T_max (time to Q_max) and post-voiding residual urine (PVR) were compared between the two tests.

Results

Out of 120 patients, transurethral catheterization significantly impacted uroflow. In male patients with benign prostatic hyperplasia (n = 50), Q_max, Q_ave and T_max were significantly different between free uroflow and pressure-flow study. In patients with female stress incontinence (n = 30), there were no statistically significant between-test differences in VV and T_max, but Q_max, Q_ave and PVR were significantly different. In patients with spinal injury or spina bifida (n = 40), Q_max, Q_ave and VV were significantly different between free uroflow and pressure-flow study.

Conclusion

Urethral catheterization adversely impacts uroflow in patients with benign prostatic hyperplasia, female stress incontinence, spinal injury or spina bifida. Free uroflowmetry should be performed before pressure-flow study.

Differences in urodynamic voiding variables recorded by conventional cystometry and ambulatory monitoring in symptomatic women

OBJECTIVES

To determine whether there are differences in pressure and flow measurements between conventional cystometry (CONV) and ambulatory urodynamic monitoring (AMB) in women with overactive bladder syndrome and urinary incontinence.

MATERIALS AND METHODS

Retrospective study which included female subjects who underwent both CONV (with saline filling medium) and AMB, separated by less than 24 months, not using medication active on the lower urinary tract and without history of prior pelvic surgery. Both tests were carried out in compliance with the International Continence Society standards. The paired Student's t test was used to compare continuous variables. Bland-Altman statistics were used to assess the agreement of each variable between both studies.

RESULTS

Thirty women with a median (range) age of 50 (14 - 73) years met the inclusion criteria. AMB was carried out at a mean (SD) of 11 (6) months after CONV. Measurements of pves and pabd at the end of filling, and Qmax were significantly higher from AMB recordings. There were no differences in pdet at the end of filling, pdetQmax or pdetmax during voiding, nor significant difference in Vvoid.

CONCLUSIONS

We provide previously undocumented comparative voiding data between CONV and AMB for patients who most commonly require both investigations. Our findings show higher values of Qmax but similar values of pdetQmax measured by AMB which may partly reflect an overall lower catheter caliber, physiological filling but perhaps also more 'normal' voiding conditions.

The effect of a 6 Fr catheter in women: Are they obstructive?

OBJECTIVES

Our objective was to evaluate the effect of a 6 Fr transurethral catheter on the uroflowmetry and to assess whether it potentially contributes to the bladder outlet obstruction (BOO) in women.

METHODS

We reviewed the charts of 1367 women who underwent an urodynamic study. We included patients with a non-invasive free-flow study (NIFFS) and pressure flow study (PFS) performed through a 6 Fr double lumen transurethral catheter.

RESULTS

In total, 120 women met the inclusion/exclusion criteria. Mean maximal flow rate (Qmax) was significantly higher (p < 0.001) in the NIFFS (27.2±11.1 mL/s) than in the PFS (19.3±10.6 mL/s). The mean difference between both Qmax was 7.9±12.0 mL/s. Of these women, 92.3% (24/26) with a Qmax <12 mL/s during PFS were found to have a Qmax ≥12 mL/s during the NIFFS. Ten of the 72 women with an available Pdet.Qmax were deemed to have a BOO according to the PFS and all of them had a Qmax >12 mL/s during the NIFFS. Of the 10 patients, only 2 reported obstructive symptoms.

CONCLUSION

The presence of 6 Fr transurethral catheters alters the PFS and results in a significant reduction of the Qmax in patients who voided more than 250 mL. We believe that NIFFS should be performed in all patients before any urethral manipulation to lower a possible overdiagnosis of BOO and findings should always be correlated to clinical symptoms.

Decreased maximum flow rate during intubated flow is not only due to urethral catheter in situ

INTRODUCTION AND HYPOTHESIS

We used the Valentini-Besson-Nelson (VBN) mathematical micturition model to analyze the potential obstructive effect of a 7-F transurethral catheter on the voiding process during intubated flow (IF) in women. Our hypothesis was that incomplete sphincter relaxation leads to residual sphincter pressure.

METHODS

We reviewed a urodynamic database of women referred for evaluation of lower urinary tract dysfunction. Exclusion criteria were neurological disease or grade ≥2 prolapse. Eligible women underwent free uroflow (FF-1) before cystometry, an IF (7-F urethral catheter), and a second FF (FF-2) at the end of the session. Interpreted flows were restricted to voided volumes ≥100 ml and continuous flow patterns. Analysis of FF and IF was made using the VBN model.

RESULTS

Among 472 women, 157 met the inclusion criteria. The effect of the urethral catheter was geometric only in 60 (38.2 %) patients. An additional effect, identified as incomplete sphincter relaxation, was observed in 97 (61.9 %) patients. Among this second group, the same residual sphincter excitation was found for 30 (30.97 %) patients during FF-2.

CONCLUSION

When comparing IF with FF with the VBN model, the decrease in maximum flow rate (Q(max)) did not appear to result only from the geometric effect of the catheter but from incomplete sphincter relaxation during voiding, possibly because of patient's anxiety or a urethral reflex induced by the presence of the catheter. These findings emphasize the need to perform an FF before the IF to strengthen the reliability of conclusions of a urodynamic investigation.

Preoperative clinical, demographic, and urodynamic measures associated with failure to demonstrate urodynamic stress incontinence in women enrolled in two randomized clinical trials of surgery for stress urinary incontinence

INTRODUCTION AND HYPOTHESIS

The unexpected absence of urodynamic stress incontinence (USI) in women planning surgery for stress urinary incontinence (SUI) is a challenge to surgeons. We examined the prevalence and clinical and demographic factors associated at baseline (preoperatively) with the unexpected absence of USI among study participants of two multicenter randomized clinical trials of surgery for treating SUI.

METHODS

Women with SUI symptoms and positive stress tests on physical examination enrolled in two separate clinical trials-one comparing the autologous fascial sling with the Burch colposuspension [Stress Incontinence Surgical Treatment Efficacy Trial (SISTEr), and the other comparing the retropubic mid-urethral sling with the transobturator midurethral sling [Trial of Mid-Urethral Slings (TOMUS)]-were evaluated for USI preoperatively. The association of clinical, demographic, and urodynamic parameters was examined in women without USI in univariate and multivariate analyses.

RESULTS

Overall, 144 of 1,233 women (11.7 %) enrolled in the two studies showed no USI. These women had a significantly lower mean volume at maximum cystometric capacity than those with USI (347.5 vs. 395.8 in SISTEr, p = 0.012), (315.2 vs. 358.2 in TOMUS, p = 0.003) and a lower mean number of daily accidents reported on a 3-day diary (2.2 vs 2.7 in SISTEr, p = 0.030) (1.7 vs 2.7 in TOMUS, p < 0.001). Additionally, those without demonstrable USI were more likely to have Pelvic Organ Prolapse Quantification (POP-Q) stage III/IV (31.7 % vs 14.4 % in SISTEr, p = 0.002), (15.5 % vs 6.9 % in TOMUS, p = 0.025). SUI severity as recorded on the Urogenital Distress Inventory (UDI) correlated strongly with the presence of USI in both studies.

CONCLUSIONS

We observed that about one of eight women planning surgery for SUI does not show USI. Stage 3/4 POP was strongly associated with the unexpected absence of USI. A diminished urodynamic bladder capacity among women who did not display USI may reflect an inability to reach the limits of capacity during urodynamics, at which these women normally leak.

Differences between the data from free flow and intubated flow in women with urinary incontinence. What do they mean?

AIMS

To assess the effects of a urethral catheter on the urodynamic data extracted from uroflow in women, and to interpret the differences from free uroflow using the VBN mathematical micturition model.

METHODS

Urodynamic data of 217 consecutive (June 2002 to December 2004) women with urinary incontinence and without neurological disease or more than grade 2 prolapse were reviewed. Inclusion criteria were to perform one free flow (FF) and one intubated flow (IF) (voided volumes of at least 100 ml and continuous flow curves). Voiding parameters: volumes, maximum flow rate, detrusor pressure and flow time, were analyzed as some characteristic ratios. The VBN model was used to make simulations of various pathophysiological hypotheses.

RESULTS

Significant increased residual volume and flow time, decreased maximum flow rate were observed during IF. Twenty five patients had a residual volume only during IF; in that group, both decrease of Q(max) and increase of flow time were significant. Simulations showed that the geometrical effect of the catheter was not the only cause and allowed to propose the occurrence of a compression-like effect of the urethra and of a fading of the detrusor excitation after Q(max) to explain the results.

CONCLUSION

Significant differences were found between the data from a FF and an IF in women with urinary incontinence. These findings bring to the fore the impact of the transurethral catheter and underline the necessity to obtain at least one FF and one IF during a urodynamic session.

Valsalva Leak Point Pressure to Determine Internal Sphincter Deficiency in Stress Urinary Incontinence

INTRODUCTION

Valsalva leak point pressure (VLPP) represents the global competence of the conjunctive forces around the urethra to support increased pressure from the abdominal cavity with transmission to the bladder. Assessment of VLPP has prognostic meaning, but measurement techniques are still subject to controversy.

PATIENTS AND METHODS

One hundred and eight consecutive women with no genital prolapse or bladder hyperactivity exclusively presenting with urinary stress incontinence were submitted to VLPP determination during urodynamic evaluation using a rectal and urethral catheter. Rectal pressure measurement served as the landmark in the determination of Valsalva's maneuver. After determining the rectal pressure, the urethral probe was pulled out and the maneuver repeated.

RESULTS

Eighty-four cases (group I) presented leakage during Valsalva's maneuver with the urethral catheter being in place. Group Ia (66.6%) had a reduction of 44.5 cm H(2)O in the rectal pressure after catheter removal. In group Ib, rectal leakage pressure increased after catheter removal from 76.5 +/- 18.7 to 79.5 +/- 24.7 cm H(2)O. Eight patients did not demonstrate urine leakage after catheter removal. In group II, 24 cases showed a rise in rectal leakage pressure to 76.2 +/- 22 cm H(2)O, but urinary leakage was only observed after catheter removal. In group IIa (19 cases), the VLPP decreased by 12.6 +/- 15 cm H(2)O, while in group IIb (5 cases) leakage occurred only in patients showing an increase of 22.2 +/- 7 cm H(2)O in the rectal pressure after the second maneuver with the urethral catheter in position.

CONCLUSIONS

Precise determination of the abdominal leak point pressure through Valsalva's maneuver may be critical. The different techniques used for VLPP determination may render comparisons difficult. Rectal pressure measurement with no urethral catheter in place to monitor abdominal leak pressure seems to be more appropriate because it resembles clinical practice. Although lower abdominal leakage pressures may be found, this is not a uniform finding, and a higher incidence of type III incontinence may be expected, and critical analysis or painstaking repetition may be required in the case of lack of demonstration of urinary loss.

A comparison of external transducers and microtransducers in urodynamic studies of female patients

The urodynamic catheter and its transducer play a significant role in the performance of good urodynamic studies. The fluid-filled (perfusion) catheter with its external strain gauge transducer and the microtransducer catheter with a transducer built directly into the catheter are the two most prevalent catheters used in urodynamic studies today. Either functions differently with regard to how pressures are measured during testing. Both are unique with regard to their requirements for handling and management during testing. Proper transducer calibration, maintenance of standardized reference levels, and attention to catheter zeroing procedures as outlined by the International Continence Society are vital to good study technique and quality testing results. When used in a manner consistent with the catheter's performance characteristics, study error is minimized and meaningful clinical data can be obtained.

A Novel, Inexpensive, Double Lumen Suprapubic Catheter for Urodynamics

PURPOSE

We describe a novel, double lumen, intravesical, suprapubic catheter designed to meet the requirements of pediatric urodynamics that is easy to use and has minimal complications.

MATERIALS AND METHODS

A commercially available 10Fr pediatric suprapubic pigtail catheter forms the outer lumen for instilling filling media. A 16 gauge epidural catheter is inserted through the outer catheter providing an inner lumen for measuring intravesical pressures. The resultant double-lumen catheter is inserted suprapubically using a peel away needle supplied with the 10Fr catheter, with the patient under general anesthetic.

RESULTS

The catheter has been used for 15 years in more than 700 patients with good reliability and few complications. The concentric construction of the double lumens and the rigidity of the inner intravesical pressure channel ensure there is no transmission of pressure from the filling channel to the inner lumen. The catheter has a circular cross section and a pigtail distal end which help to retain it within the bladder. There is low resistance to filling that allows adequate filling rates to be achieved by gravity rather than necessitating a pump. The catheter is easily made from readily available components and is less expensive than other double-lumen catheters suitable for suprapubic use.

CONCLUSIONS

A reliable, double lumen catheter that fulfills criteria not found in commercially available alternatives can be inexpensively made for urodynamics.

Intrinsic urethral sphincteric deficiency: critical analysis of various diagnostic modalities

PURPOSE OF REVIEW

The proper diagnosis of intrinsic urethral sphincteric deficiency among women with urinary incontinence carries important implications for determining the most effective medical or surgical therapy. Numerous diagnostic tests have been described attempting to make an accurate and comprehensive assessment of urethral function, but all suffer from a lack of standardization or inconsistently quoted reference values. This paper will review the literature on the positive aspects and limitations of commonly employed procedures to diagnose intrinsic urethral sphincteric deficiency.

RECENT FINDINGS

Specific urodynamic studies, including the 'active' valsalva leak-point pressure and the 'static' urethral pressure profile are commonly used to determine urethral competence. However, these tests measure specific aspects of the continence mechanism under different clinical conditions, which limits the direct comparison between them. More complex techniques such as Doppler ultrasound, video-urodynamics and both static and dynamic magnetic resonance imaging are attempting to validate the urodynamic findings for urethral function. This approach may encourage the standardization of these procedures and parameters for diagnosing intrinsic urethral sphincteric deficiency.

SUMMARY

A single definitive test for the diagnosis of intrinsic urethral sphincteric deficiency does not exist. Instead, multiple tests should be employed to reach a consensus for the diagnosis. This should include a complete voiding history, simple office examinations, and advanced studies such as urethrocystoscopy, urodynamics and possibly radiological evaluations. Understanding the limitations and variabilities of their equipment and the specific studies utilized should enable practitioners to standardize the approach for determining the extent of urethral dysfunction.