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

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.

Defining bladder outlet obstruction and detrusor underactivity in females with overactive bladder: Are we forgetting about the free uroflowmetry?

INTRODUCTION

Both detrusor underactivity (DU) and bladder outlet obstruction (BOO) can coexist in patients with overactive bladder. Definitions of both DU and BOO are based on pressure-flow study (PFS) data. However, invasive urodynamics study can differ from a natural micturition, in fact, discrepancies between free uroflowmetry (UFM) and PFS have been largely described. Our goal is to assess the correlation of free-flowmetry and PFS among patients with OAB and to evaluate how different definitions of DU/BOO are able to discriminate patients with different free UFMs.

METHODS

A retrospective review of urodynamics performed at a single institution was conducted. Females with OAB who voided more than 150 mL in both UFM and PFS were included. Parameters from both voiding episodes were compared with nonparametric test. Two definitions of DU were applied; PIP1: Pdet@Qmax+Qmax < 30 and Gammie: Pdet@Qmax < 20 cmH₂ O, Qmax < 15 mL/s, and BVE < 90% (Bladder voiding efficiency). Also, two definitions of obstruction were chosen; Defretias: Pdet@Qmax ≥25 cmH₂ O and Qmax ≤ 12 mL/s and Solomon-Greenwell female BOO index ≥ 18. Patients who matched with each definition were compared to those who did not, to assess if any definitions were able to discriminate different noninvasive uroflowmetries.

RESULTS

A total of 195 patients were included. Overall, mean age was 55 ± 12 years, 90.8% had mixed urinary incontinence, and 39% complained of at least one voiding symptom. Globally, Qmax and BVE correlated poorly between UFM and PFS, showing that most of the variation corresponded to a systematic error. Twenty-two individuals were found to have DU, they had a difference of 13 mL/s on both maximum flows. Fifty-four patients showed BOO, with a difference between their Qmax of 19 mL/s. Among the four definitions analyzed, only PIP1 and Defreitas were able to discriminate patients with actually a lower Qmax on the free UFM.

CONCLUSIONS

Patients with overactive bladder seem to have a systematic discordance between the urine flow of the free and invasive studies. Current definitions of DU and BOO, which are based on the PFS parameters, are not consistently able to discriminate patients who actually void deficiently on the free UFM.

Transurethral versus suprapubic catheterization to test urethral function in rats

Transurethral and suprapubic catheterization have both been used to test urethral function in rats; however, it is unknown whether these methods affect urethral function or if the order of catheterization affects the results. The aim of this cross-over designed experiment was to compare the effects of catheterization methods and order on leak point pressure (LPP) testing. LPP and simultaneous external urethral sphincter electromyography (EUS EMG) were recorded in anesthetized female virgin Sprague-Dawley rats in a cross-over design to test the effects of transurethral and suprapubic catheterization. There was no significant difference in peak bladder pressure during LPP testing whether measured with a transurethral or suprapubic catheter. There was no significant difference in peak bladder pressure between the first and second catheter insertions. However, peak EMG firing rate, as well as peak EMG amplitude and EMG amplitude difference between peak and baseline were significantly higher after the first catheter insertion compared to the second insertion, regardless of the catheter method. Our results suggest that route of catheterization does not alter urethral function, e.g. create a functional partial outlet obstruction. Either catheterization method could be used for LPP and/or EUS EMG testing in rats.

Comparison of bladder voiding efficiency in women when calculated from a free flow versus an intubated flow

OBJECTIVES

To assess the reproducibility of bladder voiding efficiency (BVE, Void%) between free flow (FF) and intubated flow (IF) and to correlate BVE measurements with urinary incontinence (UI) complaints and urodynamic (UDS) findings in women.

METHODS

UDS recordings of women referred for LUTD evaluation to our UDS center were reviewed. Each file included FF at arrival, filling cystometry, and IF. Post-void residual volumes (PVR) were measured by catheterization after FF and IF. Women unable to void during the study or who expelled the catheter during IF, as well as studies with voided volume < 100 ml were excluded. Data was sub-analyzed according to 3 age categories, and UI complaints and UDS findings.

RESULTS

Over the past 3 years, 237 UDS studies for FF and IF met all criteria. There was significant difference between voided volumes (232 vs. 335 ml) and PVR (24 vs. 71 ml) respectively (P < 0.0001). For the whole population, BVE IF (79.8 ± 28.6) was significantly lower than BVE FF (90.7 ± 15.9) (P < 0.0001). A significant decrease of BVE during IF was only noted for UI. BVE IF was significantly different in women in the peri-menopause and older groups. PVR IF increased with age and was significantly higher than PVR FF for women older than 45 years (P < 0.0001).

CONCLUSIONS

BVE measurement in women has a role, but is most reliable from a FF. BVE is influenced by age and urinary incontinence complaints as well as UDS findings.

Identification of experimental bladder sensitivity among dysmenorrhea sufferers

BACKGROUND

Dysmenorrhea is a common risk factor for chronic pain conditions including bladder pain syndrome. Few studies have formally evaluated asymptomatic bladder pain sensitivity in dysmenorrhea, and whether this largely reflects excess pelvic symptom reporting due to comorbid psychological dysfunction.

OBJECTIVE

We sought to determine whether bladder hypersensitivity is more common among women reporting moderate or greater dysmenorrhea, without chronic pain elsewhere, after accounting for anxiety and depression. Demonstrating this would suggest that dysmenorrhea might be an early clue for visceral or widespread pain hypersensitivity and improve understanding of potential precursors to bladder pain syndrome.

STUDY DESIGN

We compared cohorts of regularly menstruating women, without symptoms of chronic pain elsewhere, reporting (1) moderate-to-severe dysmenorrhea (n = 98) and (2) low levels or no menstrual pain (n = 35). Participants underwent rapid bladder filling following a standard water ingestion protocol, serially rating bladder pain and relative urgency during subsequent distension. Potential differences in bladder volumes were controlled for by sonographic measurement at standard cystometric thresholds. Bladder sensitivity was also measured with complementary measures at other times separately including a simplified rapid filling test, palpation of the bladder wall, and through ambulatory self-report. Anxiety and depression were evaluated with the National Institutes of Health Patient-Reported Outcomes Measurement Information System measures.

RESULTS

Women with moderate-to-severe dysmenorrhea reported more urinary symptoms than controls and had a lower maximum capacity (498 ± 18 mL vs 619 ± 34 mL, P < .001) and more evoked bladder filling pain (0-100 visual analog scale: 25 ± 3 vs 12 ± 3, P < .001). The dysmenorrhea-bladder capacity relationship remained significant irrespective of menstrual pain severity, anxiety, depression, or bladder pain (R² = 0.13, P = .006). Severity of menstrual pain predicted evoked bladder pain (R² = 0.10, P = .008) independent of anxiety (P = .21) and depression (P = .21). Women with moderate-to-severe dysmenorrhea exhibiting provoked bladder pain (24/98, 24%) also reported higher pain during the screening rapid bladder test (P < .001), in response to transvaginal bladder palpation (P < .015), and on prospective daily diaries (P < .001) than women with dysmenorrhea without provoked bladder pain.

CONCLUSION

Women experiencing moderate-to-severe dysmenorrhea also harbor a higher pain response to naturally evoked bladder distension. Noninvasive bladder provocation needs to be tested further longitudinally in those with dysmenorrhea to characterize the course of visceral sensitivity and determine if it may help predict individuals at risk for developing subsequent pain in the bladder or elsewhere.

Are nomograms based on free uroflows helpful to evaluate urethral obstruction in men?

AIMS

It was demonstrated earlier that reduced maximum flow-rate (Q_max ) during intubated flow (IF) in women may be the consequence of a urethral reflex. Over-estimation of outflow obstruction is the consequence. Our hypothesis, that a similar phenomenon could occur in men, is tested using results of a free uroflow (FF) preceding an IF to eventually correct the Abrams-Griffiths (AG) number.

METHODS

Retrospectively, analysis of 441 urodynamic studies of men suspected of bladder outflow obstruction (BOO) was performed. The Valentini-Besson-Nelson model links outflow obstruction (parameter pucp) and the detrusor contractility (parameter k) to Q_max and detrusor pressure at Q_max (p_det.Qmax ). AG and pucp are strongly correlated. Contractility is described by a graphical representation (a nomogram) which numerical fitting is an algebraic equation f(Q_max ,p_det.Qmax ). Nomograms based on IF allowed computing a calculated AG (corr-AG) on the basis of free flow.

RESULTS

Included files (N = 362) had filling volume during FF > 90 mL; corr-AG was compared to AG. When Q_max.FF  > 1.5*Q_max.IF (N = 114), 61 patients (53.5%) were found less obstructed with corr-AG, no one more obstructed. Increased BOO could be the result of a urethral reflex during IF and AG gave an overestimation. When Q_max.FF  < 1.5*Q_max.IF (N = 248), only 39 patients (12.1%) were found less obstructed with corr-AG and 28 (11.3%) more obstructed.

CONCLUSION

To obtain a reliable evaluation of BOO in men, it is suitable to perform a FF before IF. A corrected AG (corr-AG) obtained from IF analysis and nomograms based on FF may be helpful for evaluation of BOO in men.

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.

VBN-based nomograms provide critical voiding parameters which can be used for invasive or non-invasive flow interpretation of women at risk of obstruction over time

AIMS

To design a simple office-based method to evaluate characteristic parameters from free uroflowmetries (FF) or pressure flow studies (PFs). This method can be applied by any physician to any recording, for instance in the follow-up of women at risk of developing outflow obstruction over time after surgical interventions.

METHOD

Using pressure-flow studies (PFs), a reliable evaluation of urethral obstruction (U) and detrusor contractility (k) parameters could be obtained from the maximum flow rate and detrusor pressure at maximum flow rate. Nomograms for these parameters were derived from theoretical computations using the VBN model. Then, to allow an evaluation of the real urethral obstruction, a protocol was designed incorporating FF data in the follow-up of women suspected of urethral obstruction.

RESULTS

Two nomograms were obtained: (1) A urethral obstruction nomogram allowing to define a Woman Obstruction Index (WOI = p_det.Qmax - 0.5*Q_max ) which has the same structure than the A-G number in men. (2) A detrusor contractility nomogram which was generalized to all initial bladder volumes. The curves were fitted by algebraic equations easily programmable on any handheld device.

CONCLUSION

Using a mathematical model of micturition and data extracted from PFs, two nomograms on urethral obstruction and detrusor contractility were designed. This tool offers a rapid and practical method for the clinician to follow women at risk of obstruction over time. Its applications will be the purpose of further studies. Neurourol. Urodynam. 36:37-42, 2017. © 2015 Wiley Periodicals, Inc.

Detrusor after-contraction: a new insight

Aims:

Detrusor after-contractions (DAC) are non-common in adults. Both definition (nothing in ICS reports) and significance (artefact, link with detrusor overactivity (DO) or bladder outlet obstruction (BOO)) remain discussed. Our purpose was to carry out an analysis of the urodynamic parameters during voidings with DAC and, using the VBN model, to simulate pathophysiological conditions able to explain both voiding phase and DAC.

Materials and Methods:

From large urodynamic database of patients referred for evaluation of lower urinary tract dysfunction, DAC were observed in 60 patients (5.7%). Criteria for DAC were post-void residual <30mL and increase of detrusor pressure >10cmH₂O. VBN model was used for analysis of both pressure and flow curves, and simulations of pathophysiological conditions.

Results:

Onset of DAC (ODAC) occurred when Q=7.3±5.7mL/s and bladder volume=17.9±15.4mL. Urgency-frequency syndrome and urodynamic diagnosis of DO were the more frequent scenarios associated with DAC. ODAC was associated to an inversion of the slope of detrusor pressure curve without any perturbation in flow curve. Among tested pathophysiological hypothesis (great, abnormal, detrusor force, sphincter contraction), none allowed restoring all recorded curves (flow rate, voiding pressure and DAC).

Conclusion:

No urodynamic characteristic of the first part of voiding is an index of occurrence of DAC. ODAC is a significant phenomenon linked with the bladder collapse. DAC is not associated with BOO but more probably with DO and appears as the result of local conditions in an almost empty bladder (concentration of stresses around a transducer); thus DAC seems of weak clinical significance.

A quantitative comparison between free uroflow variables and urodynamic data, and the effect of the size of urodynamic catheters on its interpretation

Objective

To assess the effect of the urodynamic catheter on the urinary flow rate and residual volume in various urodynamic diagnoses, and compare the outcome when using a smaller catheter, as the effect of this catheter on free uroflow variables is mostly studied in patients with bladder outlet obstruction (BOO) and little is known about its effect in other urodynamic diagnoses.

Patients and methods

In all, 319 men undergoing a pressure-flow study (PFS) with a 5 F filling and 5 F measuring bladder catheter were subdivided into three groups based on a urodynamic diagnosis, i.e. normal PFS (group 1), BOO (group 2) and detrusor underactivity (DU, group 3). Another group (4) comprised 61 patients who had a PFS with the filling catheter removed before the voiding phase. The effect of the catheters on the maximum urinary flow rate (Q_max) and the postvoid residual volume (PVR) was analysed statistically and compared among the groups. We also compared the free-flow variables with the clinical and urodynamic variables.

Results

Groups 1–3 (with two catheters) had a significantly lower Q_max and higher PVR than those voiding with one catheter (group 4). The reduction in Q_max was highest in group 3 (41.9%) and least in group 2 (21%). Group 4 showed no significant change in Q_max in cases with BOO and a normal PFS but a significant decline in those with DU (19.6%). The PVR was positively associated with the bladder capacity and negatively with detrusor contractility, but no association with a urodynamic diagnosis of BOO or any specific symptom.

Conclusion

Detrusor contractility was the strongest predictor of the obstructive effect caused by the catheter. This study justifies the use of a single 5 F catheter at the time of voiding, although that can also cause a reduction in flow in patients with DU.

Clinically relevant modeling of urodynamics function: the VBN model

BACKGROUND

For the past two decades, a mathematical model of micturition was built step by step. Fundamental studies, presentations of the model and several applications to various male and female lower urinary tract dysfunctions have been published. We expect now that other teams will be interested in using it. In order to do so, a VBN pack (software in Linux and tutorial) is freely available.

AIMS

The purpose of this review is to describe the model and to show its practical usefulness.

MATERIALS AND METHODS

After a short description of the basis of the model and of how to use it, some published applications were summed up. The main application of the VBN model is to obtain a coherent modelling for a given patient from a set of several recordings (free uroflows and pressure-flow study) obtained either during the same session or in follow up.

RESULTS

This experience gradually led us to study what information could be extracted from a free uroflow. In addition, the model is valuable to quickly compute the effect of some additional condition; thus, it can predict the effect of an experimental artefact (urethral catheter, penile cuff).

CONCLUSION

Because the process of fitting model computations and real recordings is a powerful way to detect unexpected phenomena, the use of the VBN model provides a method to improve the knowledge of misunderstood dysfunctions of the lower urinary tract.