In the last 50 years, our understanding of several pathological conditions of lower urinary tract dysfunction (LUTD) affecting both genders in adult and paediatric population evolved tremendously. The development of urodynamic studies and their application in the research of various types of LUTD played a major role in this advancement. This chapter aims to summarise the mile stones of urodynamic research in the last 50 years related to different diseases of LUTD.
Urodynamics, as we see it nowadays, as an objective evaluation of the mechanics of micturition, was started some centuries ago. But it has evolved into a separate science in these last decades, mostly because of the share of understanding among specialists of different backgrounds. The International Continence Society (ICS) took the lead not only on the development of new ideas, new measurements, but also promoting standards of thought, conventions and training accepted all over the world. This enabled meta analyses not possible before a common and universal language and practices. The result was a huge amount of discussion, progress and clinical meaning.
Urodynamic evaluation of micturition is an old test with more than 100 years. For long it was meant to put in numbers the events of storing and eliminating urine and try to explain the abnormal conditions of the lower urinary tract found in clinical settings.
During the seventies and eighties of the last century, two main achievements changed the way we understand micturition physiology: the synchronous addition of radiological imaging1 and the attempt to set the standards of urodynamic procedures and the urodynamic equipment.2, 3, 4, 5
ICS stood as the forum of urodynamic discussion and research after publishing regularly the Neurourology & Urodynamics journal in the early 80’s. ICS proceedings were then followed by all professionals in the field. The Urodynamics Committee has been serving to popularize and to teach the best urodynamic practice for many years by designing and validating educational courses and materials, globally. The recently founded School of Urodynamics comes under the remit of the Urodynamics Committee and works to deliver gold standard educational resources in Urodynamics to members through eLearning and work placements at international centres of excellence.
ICS has been the right environment to connect clinicians with physicists and engineers developing the hydrodynamic concepts applied to voiding and storage physiology and the physics of micturition were promptly explained and clinically relevant modelling of urodynamics function were established.6, 7
Computerization of data had a crucial role when personal computing hit several medical fields. The computer is ideally suited for storing and retrieving a large volume of medical data. Described herein is a computer program written for the management of data from patients who have had urodynamic evaluation.8, 9, 10
The computer was found capable of recording urodynamic tracings, storing the data on computer files, and generating graphic summaries of test results. The computerized work station was found to be easy to operate, safe for patient use, accurate in reporting results, and durable in active clinical use. Computer technology showed to be well adapted to urodynamic testing with both clinical and research applications.11
Soon, pressure/flow studies became a valuable tool to measure the bladder outlet resistance and the detrusor performance, the hallmarks of voiding efficiency and dysfunctions. Repeated pressure/flow studies of micturition, with and without a thick catheter in the urethra, together with an on‐line plot of detrusor pressure against flow rate, enable real anatomic urethral obstruction to be distinguished from functional effects.12, 13
Standards and recommendations
Several reports were published with the details the recommendations of the Urodynamic Society on urodynamic procedures. It was the unanimous opinion of the members of the task force that the practicing urologist should have access to cystometry, voiding cystourethrography, and estimation of urinary flow rate and postvoid residual urine volume.3
These were also adapted to special groups of patients as the pediatric population such as the International Children's Continence Society standardization report on urodynamic studies of the lower urinary tract in children.14 Proposals on video and EMG be added to urodynamics in children with lower urinary tract dysfunction were then justified by the evidence.15
In 2002, the standardisation sub-committee of the ICS published the standardisation of terminology of lower urinary tract function also introducing new terminology for urodynamic findings.16 Periodically, the fundamentals of urodynamic practice, based on ICS good urodynamic practices recommendations were published and followed by the urodynamic communities.17
The International Consultation on Incontinence (ICI) has published an update of the recommendations for the diagnosis and management of urine incontinence (ICI 2016). This manuscript summarizes the recommendations of the ICI committee with regard to urodynamic assessment 18.
A recent study analysed the findings of the UPSTREAM study and reported the recommendations for conducting invasive urodynamics for men with lower urinary tract symptoms (LUTS). 19 A recent report on male LUTS set the terminology for adult male lower urinary tract and pelvic floor symptoms and dysfunction and urodynamic examination.20
Not only the clinical standards but also the Standards on equipment were produced.4 The first report of the ICS on the development of comprehensive guidelines for “Good Urodynamic Practice” for the measurement, quality control, and documentation of urodynamic investigations in both clinical and research environments was published in 2002. This report focused on the most common urodynamics examinations; uroflowmetry, pressure recording during filling cystometry, and combined pressure-flow studies. The basic aspects of good urodynamic practice are discussed and a strategy for urodynamic measurement, equipment set-up and configuration, signal testing, plausibility controls, pattern recognition, and artifact correction are proposed. The problems of data analysis are mentioned only when they are relevant in the judgment of data quality. In general, recommendations are made for one specific technique. This does not imply that this technique is the only one possible. Rather, it means that this technique is well-established, and gives good results when used with the suggested standards of good urodynamic practice.21
Updates by the ICS on good urodynamic practices and terms followed with urodynamics, uroflowmetry, cystometry, and pressure-flow study22. Other examples are the ICS standard for digital exchange of urodynamic study data. 23
Recently, some technical advances were proposed by manufacturers and several groups compared air-charged and water-filled urodynamic pressure measurement catheters 24, 25, enabling conversion of urodynamic pressures measured simultaneously by air-charged and water-filled catheter systems26 and set the implications for good urodynamic practice 2728. The ICS promoted guidelines on urodynamic equipment performance. 29
Some conditions of the lower urinary tract were specifically studied.
Post prostatectomy incontinence (PPI) was urodynamically explained. Urodynamic observations on incontinent postprostatectomy patients were the key: The factors causing incontinence were1 persistent detrusor hyperactivity,2 sphincter failure causing passive incontinence, and 3 a combination of the above two factors.30 The role of bladder dysfunction as a causative factor in post‐prostatectomy incontinence is then strongly emphasized.31
A 1998 paper described the urodynamic findings in postprostatectomy incontinence 21 and two latter studies proposed a urodynamic protocol to comprehensively assess all parameters of PPI 3334.
During a prospective study, the effects of radical retropubic prostatectomy on bladder and sphincter function were analysed by comparing preoperative and postoperative urodynamic data. 35
Bladder capacity on preoperative urodynamics was found to impact outcomes on transobturator male slings. 36 Functional and anatomical differences between continent and incontinent men post radical prostatectomy on urodynamics and 3T MRI. 37 Urodynamic parameters were challenged to predict the success of adjustable transobturator male system (ATOMS) to treat PPI.38
Female stress urinary incontinence
Female stress urinary incontinence and the results of surgical treatments are explained by manometric means. For example, post-operative urodynamic evaluation after sling surgery was reported in 1983. 39 Women undergoing a polypropylene suburethral sling procedure for treatment of genuine stress incontinence were assessed pre‐ and post‐operatively by standard urodynamic methods and by urethral pressure profile measurements at rest and on stress.
The urodynamic characteristics were reported for de novo, post sling urgency incontinence 40, and for incontinence after mid-urethral sling removal . 41 Long-term outcomes for transobturator tension-free vaginal tapes in women with urodynamic mixed urinary incontinence was studied.42 Likewise, the efficacy and safety of TVT for the treatment of urodynamic stress incontinence was assessed at 13-year follow-up.43
Urodynamic findings in 250 patients with objective stress incontinence were compared with those of 108 controls without abnormalities.44 Pelvic floor re-education and body posture correction for treatment of female urinary incontinence was assessed by pre- and post-treatment urodynamic testing.45
The clinical and urodynamic findings in patients with either mixed urinary incontinence or simple urge urinary incontinence were reported.46 The urodynamic diagnoses of women with mixed urinary incontinence symptoms were defined.47
Pre-operative evaluation of female stress incontinence
A large worldwide discussion on the value of urodynamic testing before surgical treatment of stress urinary incontinence in women is still ongoing. A study evaluated the usefulness of the urethral pressure profile (UPP) parameters in assessing the severity of genuine (urodynamic) stress incontinence.48 The assumption of stress incontinence as a non-manometric event led to the idea of omitting preoperative urodynamic investigation.49 Baseline demographic, clinical, and urodynamic variables were found to correlate with measures of urethral function in women planning mid-urethral sling surgery.50
Likewise, another study suggested that in women with pure stress urinary incontinence pre-operative invasive urodynamic studies were not any more needed when symptoms were assessed by the initial standard evaluation including measurement of post-void residual volume and a stress test.51 For some, pre-operative urodynamics in women with stress urinary incontinence increases physician confidence, but does not improve outcomes.52 A secondary analysis of the ValUE trial suggested that eliminating this preoperative test has a major economic benefit.53 A further analysis on the trends in urodynamic testing prior to mid urethral sling placement revealed that the rate of preoperative urodynamic testing decreased after publication of the VALUE trial 554 Likewise, this observation was reported by others, too.55
In contrary, some others strongly argued against the idea that calls pre-operative urodynamics useless in the treatment of female stress urinary incontinence. 56
In an uncomplicated population of women with SUI, it is not demonstrated that preoperative urodynamic evaluation can improve the outcome of continence surgery; however, UDS provides additional information regarding lower urinary tract function that could guide the physician to make the right therapeutic choice. UDS should be considered mandatory before surgery in complicated patients, but its use should also be evaluated in index patients when the results may help counselling and management of these women.57
A further analysis of the published randomised trials that found the pre-operative urodynamics unnecessary, revealed that even in the so-called index patients preoperative urodynamics diagnosed detrusor underactivity or detrusor overactivity in more than 1/3rd of the patients. Although, this would not necessarily change the decision for surgery, it would certainly affect the preoperative patient counselling since both detrusor underactivity or detrusor overactivity is shown to affect the outcome of surgery by many studies. 58 Another important point to consider is that the index patients constitute only a very minor group and the vast majority of the patients with stress urinary incontinence are classified as complicated.58
Vesico-ureteral reflux and voiding dysfunction relationship was analysed in 1983. Perioperative measurements of ureteral pressure, bladder pressure, and ureteral electromyographic activity were performed during bladder filling in vesicoureteral reflux patients.59
Significance of after-contractions
The detrusor after‐contraction is an involuntary detrusor contraction occurring after the completion of voiding. These contractions were seen in the micturition studies of 20 patients undergoing video-urodynamic studies to investigate a variety of nonneurogenic emptying or storage problems.60
Overactive bladder evaluation
Overactive bladder (OAB), as a clinical syndrome, and not always related to detrusor overactivity led to the uncertainty whether the urodynamic diagnosis is useful in the management of women with symptoms of OAB .61
The variability of urodynamic parameters in patients with overactive bladder was shown,63 particularly in special groups as OAB in older female patients.63
The research question whether patients with symptoms and signs of lower urinary tract dysfunction need a urodynamic diagnosis was also discussed by the ICI-Research Society in 2013.64 The weak association between urodynamic variables and severity of OAB in women with idiopathic detrusor overactivity was shown in another study.65
Underactive bladder (UAB)
Extensive discussion and research are continuing on the definition and diagnosis of UAB, whether UAB is a symptom complex or a urodynamic diagnosis.66 Spontaneous voiding is surprisingly recoverable via outlet procedure in men with underactive bladder and documented detrusor underactivity on urodynamics.67
Neurogenic uropathy is believed to have pressure related outcomes and diagnosis is not always clear. In a study, seventy‐five patients with equivocal neurologic findings were prospectively evaluated to determine the presence or absence of “neurogenic bladder.68 Some diseases as Parkinson and multiple system atrophy can be distinguished early by urodynamic means.69
Early predictors of bladder recovery and urodynamics after spinal cord injury were reported.70 Urinary and neurological features were shown to correlate with each other in multiple sclerosis.71 A consensus statement about the urodynamics in patients with multiple sclerosis was published by a urodynamic expert working group.72 Clinical usefulness of urodynamic assessment for maintenance of bladder function in patients with spinal cord injury was reported.73 The role of sacral neuromodulation for treating neurogenic bladder dysfunction was assessed by a clinical and urodynamic study.74 Utility of urodynamics, including ambulatory, and 24 h monitoring, in predicting upper urinary tract damage in neuro-urological patients and other lower urinary tract dysfunction was further assessed.75
A clinical review and best practice paper by a working group of the ICS Urodynamics Committee was published about urodynamics in patients with spinal cord injury.76
The role of detrusor leak poin pressure in the prediction of upper urinary tract damage was assessed in a large cohort of children with myelomeningocele.77 It was shown that more than half of the children with myelodysplasia had normal UUT function even with a DLPP of 40 cm H2 O and over. It was suggested that DLPP should not the sole decision-making parameter to rely for more invasive therapies in children with myelodysplasia. On the other hand, a DLPP cut-off value of 20 cm H2 O was found to have a higher sensitivity to predict UUT damage instead of 40 cm H2 O.
The urodynamic evaluation of male LUTS associated with benign prostatic hyperplasia was described in 1989, when male LUTS were still called as prostatism symptoms.78
A method to measure the urodynamic improvement when treating urethral obstruction is introduced and applied to patients with benign prostatic hypertrophy.79
Urodynamic features of enuresis were assessed in 1989.80
Female bladder outlet obstruction
To evaluate whether bladder outlet obstruction index (BOOI), a mathematical index of outlet resistance, in association with maximal flow rate (Qmax) obtained during multichannel urodynamics (UDS) or detrusor pressure at maximal flow rate (PdetQmax) could help the identification of obstruction in women.81
Pre-operative urodynamic evaluation of female pelvic organ prolapse
In a retrospective study, pre-operative urodynamics are found to be unnecessary for patients with asymptomatic pelvic organ prolapse since none of the investigated parameters of the urodynamic investigation tests was associated with the presence of urinary incontinence after surgery.82 However, in a larger study it was shown that an accurate pre-surgical evaluation of patients with prolapse is incomplete without urodynamics, due to the high proportion of urodynamic findings in presumably "asymptomatic" patients.83
Advantages and pitfalls of ambulatory detrusor pressure monitoring are discussed.84, 85 Comparison of ambulatory versus conventional urodynamics in females with urinary incontinence.86
ICS Teaching Modules on Urodynamics
The project of ICS on “Urodynamic Teaching Modules” was started in 2012 by the Urodynamics Committee at the ICS with the idea of improving and popularizing urodynamic practice all over the world by producing papers for specific utilization of urodynamic studies. This was really necessary because there was no document or guideline that clearly enlightened the best clinical urodynamic practice for specific clinical conditions of LUTD in a basic and advanced manner. Today, the project is evolved to “ICS Educational Modules” to target not only the urodynamic practice but also the “best practice” management of several conditions related to Female & Functional Urology. The completed modules were published in Neurourology and Urodynamics.
The first completed module was published in 2014 and elaborated the pad testing in the evaluation of urinary incontinence.87 This was followed in 2016 by the basic modules on the analysis of voiding, pressure flow analysis88 and measurement of post-void residual urine.89 In 2017, 4 teaching modules were published; focusing on artefacts in urodynamic pressure traces (basic module)90, ambulatory urodynamic monitoring91, detrusor leak point pressures in patients with relevant neurological abnormalities92 and cystometry (basic module).93 In 2018, other 3 modules, about electromyography94 and ICS standardization of cough stress test95 were published.
In parallel to its mission, the ICS has played a pioneering role in the standardisation, optimisation and popularisation of urodynamic studies and supported the related research in the last 50 years. This goal was achieved by many ways including numerous educational courses and materials, expert working group reports of best practice or consensus or standardisation, teaching modules and also by providing the researchers with the best platforms to share their knowledge such as ICS annual meetings or ICS official journal, Neurourology and Urodynamics.
Article by Luis Miguel Abranches-Monteiro, Tufan Tarcan and Enrico Finazzi Agrò on behalf of the ICS Urodynamics Committee