Is the time right for a new initiative in mathematical modeling of the lower urinary tract? ICI-RS 2023.

INTRODUCTION: A session at the 2023 International Consultation on Incontinence - Research Society (ICI-RS) held in Bristol, UK, focused on the question: Is the time right for a new initiative in mathematical modeling of the lower urinary tract (LUT)? The LUT is a complex system, comprising various synergetic components (i.e., bladder, urethra, neural control), each with its own dynamic functioning and high interindividual variability. This has led to a variety of different types of models for different purposes, each with advantages and disadvantages. METHODS: When addressing the LUT, the modeling approach should be selected and sized according to the specific purpose, the targeted level of detail, and the available computational resources. Four areas were selected as examples to discuss: utility of nomograms in clinical use, value of fluid mechanical modeling, applications of models to simplify urodynamics, and utility of statistical models. RESULTS: A brief literature review is provided along with discussion of the merits of different types of models for different applications. Remaining research questions are provided. CONCLUSIONS: Inadequacies in current (outdated) models of the LUT as well as recent advances in computing power (e.g., quantum computing) and methods (e.g., artificial intelligence/machine learning), would dictate that the answer is an emphatic "Yes, the time is right for a new initiative in mathematical modeling of the LUT."

Detrusor contractility in post-menopausal women: Impact of ageing, complaint and urodynamic diagnosis.

INTRODUCTION: Detrusor contractility (DC) can have a considerable impact on the management oflower urinary tract symptoms (LUTS). However, it is currently impossible to predict, based on clinical data alone, which woman has an impaired DC. Our aim was to determine if DC, assessed by projected isovolumetric pressure-1 (PIP1) and VBN contractility parameter k, was associated with age, main complaint, and urodynamic diagnosis in a population of older women. METHODS: Pressure-flow studies of non-neurologic post menopausal women over 65 referred for investigation of LUTS were retrospectively analyzed. Associations between DC indices PIP1 and k, and age, main complaint and urodynamic diagnosis were assessed in univariate analysis. RESULTS: One hundred and ninety women were included (mean age 74.5 years). There was no significant association between detrusor contractility indices and age considered as a continuous or a categorical variable. Urge urinary incontinence was significantly associated with greater detrusor contractility regardless of age. Regarding urodynamic diagnoses, DC was greater when bladder outlet obstruction and detrusor overactivity were diagnoses vs. detrusor underactivity alone or associated with detrusor overactivity, regardless of age. CONCLUSION: PIP1 and k indices allow an easy evaluation of detrusor contractility. In that population of older, post menopausal women, no significant change in the value of the indices is observed with aging whatever the complaint or the urodynamic diagnosis. None of these indices has predominance. LEVEL OF EVIDENCE: 4.

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

AIMS: It was demonstrated earlier that reduced maximum flow-rate (Qmax ) 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 Qmax and detrusor pressure at Qmax (pdet.Qmax ). AG and pucp are strongly correlated. Contractility is described by a graphical representation (a nomogram) which numerical fitting is an algebraic equation f(Qmax ,pdet.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 Qmax.FF > 1.5*Qmax.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 Qmax.FF < 1.5*Qmax.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.

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.

Can we define and characterize the aging lower urinary tract?-ICI-RS 2015.

The prevalence of lower urinary tract (LUT) symptoms increases with age but the etiology is unknown. This article aims to identify research directions that clarify the basis of this association. The initial question is whether biological age is the variable of interest or a time-dependent accumulation of factors that impact on LUT function at rates that differ between individuals. In particular, the accumulation of conditions or agents due to inflammatory states or tissue ischemia is important. Much of the above has been concerned with changes to bladder function and morphology. However, the outflow tract function is also affected, in particular changes to the function of external sphincter skeletal muscle and associated sacral motor nerve control. Nocturia is a cardinal symptom of LUT dysfunction and is more prevalent with aging. Urine production is determined by diurnal changes to the production of certain hormones as well as arterial blood pressure and such diurnal rhythms are blunted in subjects with nocturia, but the causal links remain to be elucidated. Changes to the central nervous control of LUT function with age are also increasingly recognized, whether in mid-brain/brainstem regions that directly affect LUT function or in higher centers that determine psycho-social and emotional factors impinging on the LUT. In particular, the linkage between increasing white matter hyperintensities and LUT dysfunction during aging is recognized but not understood. Overall, a more rational approach is being developed to link LUT dysfunction with factors that accumulate with age, however, the precise causal pathways remain to be characterized. Neurourol. Urodynam. 36:854-858, 2017. © 2017 Wiley Periodicals, Inc.

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 = pdet.Qmax - 0.5*Qmax ) 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 >10cmH(2)O. 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.

Detrusor after-contraction: a new insight

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.

Contribution of behavioral and cognitive therapy to managing overactive bladder syndrome in women in the absence of contributive urodynamic diagnosis.

Overactive bladder (OAB) is a syndrome characterized by symptoms of urgency with or without incontinence, frequency, and nocturia. Pathophysiology of OAB is incompletely characterized. Therefore, there is great variability surrounding OAB evaluation. In some cases, urodynamics is normal and the challenge is to propose the least invasive treatment. Behavioral therapies have been used for decades as they are conservative, inexpensive, and do not induce side effect. Our purpose was to describe which usual techniques of pelvic floor rehabilitation in association with behavioral and cognitive therapy could be proposed to manage OAB syndrome in the absence of urodynamic diagnosis and when no targeting drug treatment could be proposed.

Do patients with symptoms and signs of lower urinary tract dysfunction need a urodynamic diagnosis? ICI-RS 2013.

AIMS: The ICI-RS Think Tank discussed the diagnostic process for patients who present with symptoms and signs of lower urinary tract (LUT) dysfunction. This manuscript reflects the Think Tank's summary and opinion. METHODS: An overview of the existing evidence and consensus regarding urodynamic testing was presented and discussed in relation to contemporary treatment strategies. RESULTS: Evidence of the validity of the diagnostic process in relation to the contemporary management paradigm is incomplete, scattered, and sometimes conflicting and therefore a process redesign may be necessary. The Think Tanks' suggestion, contained in this manuscript, is that the symptoms and signs that the patients present can be more precisely delineated as syndromes. The overactive bladder syndrome (OAB-S); the stress urinary incontinence syndrome (SUI-S); the urinary incontinence syndrome (UI-S); the voiding dysfunction syndrome (VD-S); and or the neurogenic LUT dysfunction syndrome (NLUTD-S) may become evidence based starting point for initial management. Consistent addition of the word syndrome, if adequately defined, acknowledges the uncertainty, but will improve outcome and will improve selection of patients that need further (invasive) diagnosis before management. CONCLUSIONS: The ICS-RS Think Tank has summarized the level of evidence for UDS and discussed the evidence in association with the currently changing management paradigm. The ICI-RS Think Tank recommends that the diagnostic process for patients with LUTD can be redesigned. Carefully delineated and evidence based LUTD syndromes may better indicate, personalize and improve the outcome of initial management, and may also contribute to improved and rational selection of patients for invasive UDS. Neurourol. Urodynam. 33:581-586, 2014. © 2014 Wiley Periodicals, Inc.

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.

Idiopathic and neurogenic detrusor overactivity: do the different patterns have urodynamic characteristics related to gender or neurological condition?

OBJECTIVES: To evaluate the urodynamic characteristics of the two patterns (phasic, P and terminal, T) of detrusor overactivity (DO) according to gender and neurological condition. MATERIALS AND METHODS: Urodynamic characteristics of DO were analysed in a population with proven urodynamic DO (127 women and 76 men, respectively with 48 and 43 neurological diseases (encephalic, incomplete medullar lesion or peripheral)). Phasic DO is characterized by phasic waves with or without leakage while terminal DO is defined by a single non-inhibited contraction resulting in incontinence. Parameters analysed for both patterns of DO (among other parameters) included: volume and amplitude of the first non-inhibited detrusor contraction (NIDC#1), and for phasic DO: duration of pressure rise during NIDC#1 and number of NIDC. RESULTS: Phasic DO was observed in younger patients in the whole population whatever the gender (women: 55.9 years vs. 64.7 years, p = 0.0052; men: 57.4 years vs. 67.8 years, p = 0.0038). Volume at NIDC#1 was greater for neurological PDO (significant in women: 185 vs. 125 mL, p = 0.0223). Other parameters were not significantly different whatever the gender. Amplitude of NIDC#1 during PDO was significantly lower than that of NIDC during terminal DO (TDO) in both genders whatever the neurological condition (p < 0.0001). Volume at NIDC#1 in both patterns was dependent on the level of neurological lesion. CONCLUSION: The main difference between the patterns of DO is that PDO occurs in younger individuals. There is no significant difference between urodynamic characteristics of each pattern whatever gender or neurological status. Further studies will provide additional information on the impact of the level of neurological lesion on the pattern of DO.