Lower urinary tract electrical sensory assessment: A systematic review and meta-analysis

Objectives

To summarize the current literature on lower urinary tract electrical sensory assessment (LUTESA), with regard to current perception thresholds (CPTs) and sensory evoked potentials (SEPs), and to discuss the applied methods in terms of technical aspects, confounding factors, and potential for lower urinary tract (LUT) diagnostics.

Methods

The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement. Medline (PubMed), Embase and Scopus were searched on 13 October 2020. Meta‐analyses were performed and methodological qualities of the included studies were defined by assessing risk of bias (RoB) as well as confounding.

Results

After screening 9925 articles, 80 studies (five randomized controlled trials [RCTs] and 75 non‐RCTs) were included, comprising a total of 3732 patients and 692 healthy subjects (HS). Of these studies, 61 investigated CPTs exclusively and 19 reported on SEPs, with or without corresponding CPTs. The recording of LUTCPTs and SEPs was shown to represent a safe and reliable assessment of LUT afferent nerve function in HS and patients. LUTESA demonstrated significant differences in LUT sensitivity between HS and neurological patients, as well as after interventions such as pelvic surgery or drug treatments. Pooled analyses showed that several stimulation variables (e.g. stimulation frequency, location) as well as patient characteristics might affect the main outcome measures of LUTESA (CPTs, SEP latencies, peak‐to‐peak amplitudes, responder rate). RoB and confounding was high in most studies.

Conclusions

Preliminary data show that CPT and SEP recordings are valuable tools to more objectively assess LUT afferent nerve function. LUTESA complements already established diagnostics such as urodynamics, allowing a more comprehensive patient evaluation. The high RoB and confounding rate was related to inconsistency and inaccuracy in reporting rather than the technique itself. LUTESA standardization and well‐designed RCTs are crucial to implement LUTESA as a clinical assessment tool.

External Validation Confirms Validity of a Simple Model to Predict Bowel Outcome After Traumatic Spinal Cord Injury

Background. The prediction of functional outcomes after spinal cord injury (SCI) is essential to plan the rehabilitation phase and the social reintegration. Recently, 2 models to predict independent and reliable bowel management 1 year after traumatic SCI have been derived and validated in 2 cohorts of patients included in the European Multicenter Study about Spinal Cord Injury (EMSCI). Objective. We aimed to validate 2 prediction models for bowel outcome after traumatic SCI in a patient sample external to EMSCI. Methods. The simplified model (based on a single predictor, the International Standards for Neurological Classification of Spinal Cord Injury [ISNCSCI] total motor score) and the full model (based on 2 predictors, the ISNCSCI total motor score and item 3a of the Spinal Cord Independence Measure) were applied to the retrospectively collected data of 111 patients with traumatic SCI. Results. The simplified and the full models showed excellent discrimination with an area under the receiver operating characteristic curve of .939 (95% confidence interval (CI) .87-1.00) and .922 (95% CI 0.85-.99), respectively. Both models displayed similar results for sensitivity and negative predictive values; however, the simplified model showed higher values for specificity, positive predictive values, and accuracy. The calibration analysis showed a partial overlap between predicted probabilities and observed proportion, with better and acceptable calibration for the simplified model. Conclusions. Using an independent sample, our study demonstrates the validity of a simple model to predict independent and reliable bowel management 1 year after traumatic SCI.

Bladder management in patients undergoing spine surgery: An assessment of care delivery

BACKGROUND

Lower urinary tract dysfunction is common in the early postoperative phase after spine surgery. Although it is essential for an optimal patient management to balance benefits and harms, it is not known which patient benefit from a perioperative indwelling catheter. We therefore evaluated urological parameters prior and after spine surgery performing a quality assessment of our current clinical practice in bladder management.

METHODS

Preoperatively, all patients completed the International Prostate Symptom Score and were interviewed for urological history. Decision for preoperative urethral catheter placement was individually made by the responsible anesthesiologist according to an in-house protocol. Within and between group analyses using univariate and probability matching statistics were performed for patients with intraoperative urethral catheter-free management (n = 54) and those with a preoperatively placed catheter (n = 46). Post void residual (PVR) was measured prior and after surgery or after removal of the urethral catheter, respectively. The outcome measures consisted of postoperative urinary retention (POUR) and postoperative urological complications (PUC), defined as POUR and any catheter-related adverse events.

RESULTS

Hundred patients undergoing spine surgery were prospectively evaluated. Sixteen of the 54 (30%) patients with urethral catheter-free management developed POUR. Length of surgery and volume of intravenous infusion were associated with POUR (p < 0.05). In the 46 preoperatively catheterized patients, re-catheterization was required in 6 (13%). In a fairly homogenous subgroup of 72 patients with a probability of PUC between 15 and 40%, no significant association between intraoperative urethral catheter-free management and the occurrence of PUC was found (odds ratio 2.09, 95% confidence interval 0.69 to 6.33; p = 0.193).

CONCLUSIONS

In case of postoperative PVR monitoring allowing de novo catheterization as appropriate, urethral catheter-free management seems to be a valuable option in spine surgery since it does not to increase PUC but minimizes unnecessary catheterizations with their related complications.

Bacteriophages: what role may they play in life after spinal cord injury?

Bacterial infections are the leading cause of death in people with a spinal cord injury (SCI). Bacteriophages (phages) are viruses that solely infect and kill bacteria. The idea of using phages to treat bacterial infections, i.e., phage therapy, is very promising and potentially allows a more specific and personalized treatment of bacterial infections than antibiotics. While multi-drug resistant infections affect individuals from the general population, alternative therapeutic options are especially warranted in high-risk populations, such as individuals with SCI. However, more clinical data must be collected before phage therapy can be implemented in clinical practice, with numerous possible, subsequent applications.

Detrusor sphincter dyssynergia: can a more specific definition distinguish between patients with and without an underlying neurological disorder?

Study design

Cross-sectional study.

Objectives

To evaluate if specific definitions of detrusor sphincter dyssynergia (DSD) might distinguish between individuals with spinal cord injury (SCI) and those with no underlying neurological disorder (NO ND).

Setting

Single tertiary university SCI center.

Methods

A series of 153 individuals, 81 with traumatic SCI and 72 with NO ND, were prospectively evaluated and included in this study. All individuals underwent a clinical neuro-urological examination, a neurophysiological work-up and a video-urodynamic investigation and were diagnosed with DSD as defined by the International Continence Society (ICS). We determined the DSD grades/types according to the classifications by Yalla (grade 1–3), Blaivas (type 1–3) and Weld (type 1–2). Distribution of the DSD grades/types were compared between SCI and NO ND individuals. Associations between the various DSD grades/types and clinical parameters, such as risk factors for upper urinary tract damage (all individuals) or lower extremity motor scores, SCI injury levels and severity scores (only SCI group), were assessed.

Results

The distribution of all DSD types were similar between groups (p > 0.05). None of the DSD classifications allowed risk assessment for upper urinary tract damage. A significant association between DSD type and other clinical parameters could not be found (p > 0.05).

Conclusions

None of the investigated DSD definitions can distinguish between patients with SCI and with NO ND. The more complex DSD classifications by Yalla, Blaivas or Weld cannot compete with the ICS binary yes-no definition which is pragmatic and straightforward for managing patients in daily clinical practice.

Sponsorship

None.

Treatment of Stress Urinary Incontinence with Muscle Stem Cells and Stem Cell Components: Chances, Challenges and Future Prospects

Urinary incontinence (UI) is a major problem in health care and more than 400 million people worldwide suffer from involuntary loss of urine. With an increase in the aging population, UI is likely to become even more prominent over the next decades and the economic burden is substantial. Among the different subtypes of UI, stress urinary incontinence (SUI) is the most prevalent and focus of this review. The main underlying causes for SUI are pregnancy and childbirth, accidents with direct trauma to the pelvis or medical treatments that affect the pelvic floor, such as surgery or irradiation. Conservative approaches for the treatment of SUI are pelvic physiotherapy, behavioral and lifestyle changes, and the use of pessaries. Current surgical treatment options include slings, colposuspensions, bulking agents and artificial urinary sphincters. These treatments have limitations with effectiveness and bear the risk of long-term side effects. Furthermore, surgical options do not treat the underlying pathophysiological causes of SUI. Thus, there is an urgent need for alternative treatments, which are effective, minimally invasive and have only a limited risk for adverse effects. Regenerative medicine is an emerging field, focusing on the repair, replacement or regeneration of human tissues and organs using precursor cells and their components. This article critically reviews recent advances in the therapeutic strategies for the management of SUI and outlines future possibilities and challenges.

Considering non-bladder aetiologies of overactive bladder: a functional neuroimaging study

OBJECTIVES

To better understand the neuropathophysiology of overactive bladder (OAB) in women by characterising supraspinal activity in response to bladder distention and cold stimulation.

SUBJECTS/PATIENTS AND METHODS

We recruited 24 female participants, 12 with OAB (median [interquartile range, IQR] age 40 [32-42] years) and 12 healthy controls (HCs) without lower urinary tract (LUT) symptoms (median [IQR] age 34 [28-44] years), and assessed LUT and cognitive function through neuro-urological examination, 3-day bladder diary, urodynamic investigation, and questionnaires. Functional magnetic resonance (MR) imaging using a 3-T scanner was performed in all participants during automated, repetitive bladder filling and draining (block design) with 100 mL body temperature (37 °C) saline using a MR-compatible and MR-synchronised infusion-drainage device until strong desire to void (HIGH-FILLING/DRAINING) and bladder filling with cold saline (4 °C, i.e. COLD). Whole-brain and region-of-interest analyses were conducted using Statistical Parametric Mapping, version 12.

RESULTS

Significant between-group differences were found for 3-day bladder diary variables (i.e. voiding frequency/24 h, P < 0.001; voided volume/void, P = 0.04; and urinary incontinence [UI] episodes/24 h, P = 0.007), questionnaire scores (International Consultation on Incontinence Questionnaire-Female LUT symptoms [overall, filling, and UI scores, all P < 0.001]; the Overactive Bladder Questionnaire short form [symptoms and quality-of-life scores, both P < 0.001]; the Hospital Anxiety and Depression Scale [anxiety P = 0.004 and depression P = 0.003 scores]), as well as urodynamic variables (strong desire to void, P = 0.02; maximum cystometric capacity, P = 0.007; and presence of detrusor overactivity, P = 0.002). Age, weight and cognitive function (i.e. Mini-Mental State Examination, P = 1.0) were similar between groups (P > 0.05). In patients with OAB, the HIGH task elicited activity in the superior temporal gyrus, ventrolateral prefrontal cortex (VLPFC), and mid-cingulate cortex; and the COLD task elicited activity in the VLPFC, cerebellum, and basal ganglia. Compared to HCs, patients with OAB showed significantly stronger cerebellar activity during HIGH-FILLING and significantly less activity in the insula and VLPFC during HIGH-DRAINING.

CONCLUSIONS

The present findings suggest a sensory processing and modulation deficiency in our OAB group, probably as part of their underlying pathophysiology, as they lacked activity in essential sensory processing areas, such as the insula. Instead, accessory areas, such as the cerebellum, showed significantly stronger activation compared to HCs, presumably supporting pelvic-floor motor activity to prevent UI. The novel findings of the present study provide physiological evidence of the necessity to consider non-bladder aetiologies of bladder symptoms.

Optimizing clinical trial design using prospective cohort study data: a case study in neuro-urology

Study Design

Simulations using data from a prospective cohort study.

Objectives

To illustrate how prospective cohort data can be employed in randomized controlled trial (RCT) planning to assess feasibility and operational challenges, using TASCI (Transcutaneous tibial nerve stimulation in patients with Acute Spinal Cord Injury to prevent neurogenic detrusor overactivity: a nationwide randomized, sham-controlled, double-blind clinical trial) as a case study.

Setting

Spinal cord injury rehabilitation centers in Switzerland.

Methods

TASCI is nested in the multicenter Swiss Spinal Cord Injury Cohort Study (SwiSCI), which prospectively includes patients with acute spinal cord injury. In simulations, data from 640 patients, collected by SwiSCI, were used to investigate different scenarios of patient eligibility and study consent, as well as the performance of the randomization list. Descriptive analysis was used to describe the population of interest and the simulation results; multivariable logistic regression analysis was performed to identify predictors of discharge within the TASCI intervention time period.

Results

The recruitment target of 114 patients is obtainable within the originally envisioned three-year time period under the most favorable recruitment scenario examined. The distribution of the primary prognostic factor produced imbalance in the randomization lists and informed further discussion of the cut-off values used in stratification. Influxes of patients resulted in overlapping intervention periods for multiple participants, which guided resource allocation. Early discharge was related to the primary prognostic factor and study center, but is only anticipated in about 8% of participants.

Conclusions

Prospective cohort data are a very valuable resource for planning RCTs.

Scalp Topography of Lower Urinary Tract Sensory Evoked Potentials

Impaired lower urinary tract (LUT) afferents often cause LUT symptoms. Assessment of LUT afferent pathways is possible using bipolar cortical sensory evoked potential (SEP) recordings with the active electrode at the vertex during electrical stimulation in the LUT. This study aimed to investigate the topographical distribution and microstates of lower urinary tract sensory evoked potentials (LUTSEPs) using different stimulation frequencies. Ninety healthy subjects (18-36 years old, 40 women) were randomly assigned to one of five stimulation locations [bladder dome; trigone; proximal, membranous (men only) or distal urethra]. Cycles of 0.5 Hz/1.1 Hz/1.6 Hz electrical stimulation were applied using a custom-made catheter. Cortical activity was recorded from 64 surface electrodes. Marker setting was performed manually on an individual subject-level for the P1, N1, and P2 components of vertex recordings. N1 and P2 topographies presented with central negativities and positivities around the vertex. Regarding topographical distribution, Randomization Graphical User interface (RAGU) analyses revealed consistent frequency effects and microstates for N1/P2. Higher stimulation frequencies resulted in decreasing map strength for P1, N1, and P2. LUTSEP topographies suggest central generators in the somatosensory cortex, which are not detectable in a bipolar set-up. The observed frequency effect indicates fiber refractoriness at higher frequencies. The multichannel approach allows more comprehensive assessment of LUTSEPs and might therefore be sensitive to pathological changes. Examinations in patients with LUT symptoms are needed to further investigate this biomarker.

Intravesical bacteriophages for treating urinary tract infections in patients undergoing transurethral resection of the prostate: a randomised, placebo-controlled, double-blind clinical trial

BACKGROUND

Urinary tract infections (UTIs) are among the most prevalent microbial diseases and their financial burden on society is substantial. In the context of increasing antibiotic resistance, finding alternative treatments for UTIs is a top priority. We aimed to determine whether intravesical bacteriophage therapy with a commercial bacteriophage cocktail is effective in treating UTI.

METHODS

We did a randomised, placebo-controlled, clinical trial, at the Alexander Tsulukidze National Centre of Urology, Tbilisi, Georgia. Men older than 18 years of age, who were scheduled for transurethral resection of the prostate (TURP), with complicated UTI or recurrent uncomplicated UTI but no signs of systemic infection, were allocated by block randomisation in a 1:1:1 ratio to receive intravesical Pyo bacteriophage (Pyophage; 20 mL) or intravesical placebo solution (20 mL) in a double-blind manner twice daily for 7 days, or systemically applied antibiotics (according to sensitivities) as an open-label standard-of-care comparator. Urine culture was taken via urinary catheter at the end of treatment (ie, day 7) or at withdrawal from the trial. The primary outcome was microbiological treatment response after 7 days of treatment, measured by urine culture; secondary outcomes included clinical and safety parameters during the treatment period. Analyses were done in a modified intention-to-treat population of patients having received at least one dose of the allocated treatment regimen. This trial is registered with ClinicalTrials.gov, NCT03140085.

FINDINGS

Between June 2, 2017, and Dec 14, 2018, 474 patients were screened for eligibility and 113 (24%) patients were randomly assigned to treatment (37 to Pyophage, 38 to placebo, and 38 to antibiotic treatment). 97 patients (28 Pyophage, 32 placebo, 37 antibiotics) received at least one dose of their allocated treatment and were included in the primary analysis. Treatment success rates did not differ between groups. Normalisation of urine culture was achieved in five (18%) of 28 patients in the Pyophage group compared with nine (28%) of 32 patients in the placebo group (odds ratio [OR] 1·60 [95% CI 0·45-5·71]; p=0·47) and 13 (35%) of 37 patients in the antibiotic group (2·66 [0·79-8·82]; p=0·11). Adverse events occurred in six (21%) of 28 patients in the Pyophage group compared with 13 (41%) of 32 patients in the placebo group (OR 0·36 [95% CI 0·11-1·17]; p=0·089) and 11 (30%) of 37 patients in the antibiotic group (0·66 [0·21-2·07]; p=0·47).

INTERPRETATION

Intravesical bacteriophage therapy was non-inferior to standard-of-care antibiotic treatment, but was not superior to placebo bladder irrigation, in terms of efficacy or safety in treating UTIs in patients undergoing TURP. Moreover, the bacteriophage safety profile seems to be favourable. Although bacteriophages are not yet a recognised or approved treatment option for UTIs, this trial provides new insight to optimise the design of further large-scale clinical studies to define the role of bacteriophages in UTI treatment.

FUNDING

Swiss Continence Foundation, the Swiss National Science Foundation, and the Swiss Agency for Development and Cooperation.

TRANSLATIONS

For the Georgian and German translations of the abstract see Supplementary Materials section.

Metaepidemiological Inventory of Diagnostic Studies on Urodynamics

BACKGROUND

Urodynamic investigations have a pivotal role in the diagnosis of lower urinary tract symptoms. Despite expert statements and guidelines supporting their usefulness for clinical decision making in various clinical domains, the academic debate remains controversial.

OBJECTIVE

To provide a metaepidemiological inventory of studies assessing the diagnostic properties of urodynamic investigations.

DESIGN, SETTING, AND PARTICIPANTS

Systematic searches without language restrictions were performed in (Pre-)Medline, EMBASE, and the Cochrane Library from inception until August 31, 2018. Checking of reference lists of included studies and reviews complemented searches. Records were compiled and screened for possible inclusion by reading title and abstracts by two teams of two research fellows. Inclusion criteria were as follows: prospective data collection and urodynamic investigations performed either as a diagnostic test or using a therapy monitoring instrument. No a priori selection on clinical domain was done. Double reading was performed on records marked "included." Extraction into a developed and piloted matrix was performed in duplicate and checked by a third research fellow.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Of each included article, study specifics, objective, study design, type of data collection, clinical domain, type and description of test used, and type of outcome were extracted and attributed to a framework.

RESULTS AND LIMITATIONS

Electronic searches retrieved 20 841 records. After screening, 299 abstracts were considered relevant. The main reasons for exclusion were as follows: animal studies, no primary data, editorial/opinion based on published data or reviews, primary objective of the study being not the assessment of urodynamic investigations, and post hoc (opportunistic) correlation studies.

CONCLUSIONS

To our knowledge, this is the first comprehensive collection of studies assessing the clinical usefulness of urodynamic investigations. The collection is the starting point for a series of systematic reviews assessing the diagnostic properties of urodynamic investigations.

PATIENT SUMMARY

The usefulness of urodynamic investigations for clinical decision making is under debate. We established an inventory of diagnostic studies on urodynamics to assess the value of urodynamics in various clinical applications.

Update from TASCI, a Nationwide, Randomized, Sham-controlled, Double-blind Clinical Trial on Transcutaneous Tibial Nerve Stimulation in Patients with Acute Spinal Cord Injury to Prevent Neurogenic Detrusor Overactivity

Transcutaneous tibial nerve stimulation has the potential to revolutionize the management of lower urinary tract dysfunction in patients with acute spinal cord injury. TASCI is a nationwide randomized, sham-controlled, double-blind clinical trial for which the preparatory phase has been successfully completed.

TASCI-transcutaneous tibial nerve stimulation in patients with acute spinal cord injury to prevent neurogenic detrusor overactivity: protocol for a nationwide, randomised, sham-controlled, double-blind clinical trial

INTRODUCTION

Neurogenic lower urinary tract dysfunction (NLUTD), including neurogenic detrusor overactivity (NDO) and detrusor sphincter dyssynergia, is one of the most frequent and devastating sequelae of spinal cord injury (SCI), as it can lead to urinary incontinence and secondary damage such as renal failure. Transcutaneous tibial nerve stimulation (TTNS) is a promising, non-invasive neuromodulatory intervention that may prevent the emergence of the C-fibre evoked bladder reflexes that are thought to cause NDO. This paper presents the protocol for TTNS in acute SCI (TASCI), which will evaluate the efficacy of TTNS in preventing NDO. Furthermore, TASCI will provide insight into the mechanisms underlying TTNS, and the course of NLUTD development after SCI.

METHODS AND ANALYSIS

TASCI is a nationwide, randomised, sham-controlled, double-blind clinical trial, conducted at all four SCI centres in Switzerland. The longitudinal design includes a baseline assessment period 5-39 days after acute SCI and follow-up assessments occurring 3, 6 and 12 months after SCI. A planned 114 participants will be randomised into verum or sham TTNS groups (1:1 ratio), stratified on study centre and lower extremity motor score. TTNS is performed for 30 min/day, 5 days/week, for 6-9 weeks starting within 40 days after SCI. The primary outcome is the occurrence of NDO jeopardising the upper urinary tract at 1 year after SCI, assessed by urodynamic investigation. Secondary outcome measures assess bladder and bowel function and symptoms, sexual function, neurological structure and function, functional independence, quality of life, as well as changes in biomarkers in the urine, blood, stool and bladder tissue. Safety of TTNS is the tertiary outcome.

ETHICS AND DISSEMINATION

TASCI is approved by the Swiss Ethics Committee for Northwest/Central Switzerland, the Swiss Ethics Committee Vaud and the Swiss Ethics Committee Zürich (#2019-00074). Findings will be disseminated through peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT03965299.

Sacral Neuromodulation: Mechanism of Action

Although the mechanism of action of sacral neuromodulation (SNM) is still not fully elucidated, it seems to involve modulation of spinal cord reflexes and brain networks by peripheral afferents according to findings from neurophysiology, electroencephalography, positron emission tomography, and magnetic resonance imaging studies. Moreover, motor effects mediated via efferents on direct stimulation cannot be fully excluded. In this mini-review, we summarize current knowledge on the mechanism of action of SNM. PATIENT SUMMARY: We reviewed the literature on the mechanism of action of sacral neuromodulation, in which electrical stimulation is applied to the nerves that regulate bladder activity. The mechanism seems to involve modulation of spinal cord reflexes and brain networks by peripheral sensory and possibly motor neurons.

Methods for Assessing Lower Urinary Tract Function in Animal Models

Lower urinary tract dysfunction affects a multitude of patients. Current therapeutic approaches are limited and very little is known about the mechanisms in failure of bladder control. Thus, more basic research is clearly needed to elucidate the underlying pathological mechanisms and to develop novel treatment strategies in urology. Noninvasive tests such as the void-spot assay and the metabolic cage and more invasive urodynamics investigations are currently used to assess lower urinary tract function in animals, in particular rodents. The noninvasive tests give some insights into the functionality of the system, whereas urodynamics testing yields an objective evaluation that allows distinction of different pathologies and investigations of the underlying neuronal malfunctions. PATIENT SUMMARY: We briefly summarize methods currently used to assess impairments of bladder function in animal models. Both noninvasive and invasive methods are available and can be used to understand and improve human health. An accurate and detailed diagnosis is, however, possible only with urodynamics assessments.

Optimized Measurement Parameters of Sensory Evoked Cortical Potentials to Assess Human Bladder Afferents - A Randomized Study

Overactive bladder and voiding dysfunction are highly prevalent and often associated with malfunction of the bladder afferent pathways. Appropriate diagnostic tools for an objective assessment of afferent nerve function of the human bladder are currently missing. One promising possibility is the assessment of sensory evoked potentials (SEP) during repetitive electrical bladder stimulation, which proved feasible in healthy subjects. For an implementation into clinical practice, however, further refinements for efficient and reliable data acquisition are crucial. The aim of this randomized study was to find the optimal measurement settings regarding stimulation frequency, repetition number, and data acquisition. Forty healthy subjects underwent two visits of SEP (Cz-Fz) assessments using repetitive (500 stimuli) electrical stimulation of 0.5 Hz, 1.1 Hz, and 1.6 Hz and pulse width of 1 ms at the bladder dome or trigone. SEP analyses revealed higher amplitudes and better signal-to-noise ratio (SNR) with lower stimulation frequencies, while latencies remained unchanged. Decreasing amplitudes and SNR were observed with continuing stimulation accompanied by decreasing responder rate (RR). When applying stimuli at a frequency of 0.5 Hz, averaging across 200 stimuli revealed optimal reliability with best SNR, RR and sufficiently high amplitudes. This constitutes an optimal compromise between the duration of the assessment and SEP peak-to-peak amplitudes.

Quantitative electrical pain threshold assessment in the lower urinary tract

AIMS

Assessing the reliability of electrical pain threshold (PT) and evaluating the impact of stimulation frequency at different locations in the healthy lower urinary tract (LUT).

METHODS

Ninety subjects (age: 18.3-35.8 years, 40 females, 50 males) were randomly allocated to one stimulation site (bladder dome [BD], trigone, proximal, membranous (only males), or distal urethra). Using 0.5 Hz/1.1 Hz/1.6 Hz electrical stimulation (square wave, pulse width:1 ms), current perception thresholds (CPTs), PTs and tolerance thresholds were assessed at two visits. Analyses were performed using linear mixed models, intraclass correlation coefficients (ICC) and Bland-Altman method.

RESULTS

PTs vary in relation to stimulation frequency, location and between genders. PT decreased with higher stimulation frequency. The highest PTs were measured at the BD and membranous urethra with males reporting higher PTs than females. Reliability of PT assessments according to ICC was good to excellent across all frequencies, locations, and genders (ICC = 0.61-0.97), except for BD and distal urethra in females showing poor to fair reliability (BD: all frequencies, distal urethra: 0.5 Hz).

CONCLUSIONS

PTs can be safely and reliably assessed from bladder and urethral locations. Semi-objective PT assessment may provide additional information on functionality and sensitivity of the LUT slow fiber afferents and complement findings from urodynamic investigations and CPT assessments. In conclusion, the developed methodology may open new opportunities for using electrical stimulation paradigms for LUT PT assessments and diagnostics. All this allows a more precise, location-specific characterization of pain origin and pain reaction towards therapy.

Ultrasound: A Valuable Translational Tool to Measure Postvoid Residual in Awake Rats?

BACKGROUND

Ultrasound is generally used to measure postvoid residual (PVR) in daily clinical practice for a basic assessment of voiding dysfunction. In animal research, however, PVR is measured mostly by expelling the urine with gentle squeezing of the bladder.

OBJECTIVE

To assess the translational value of measuring PVR by ultrasound in awake rats with the aim of obtaining directly comparable data sets in patients and rodent models.

DESIGN, SETTING, AND PARTICIPANTS

A prospective animal study was conducted in 10 rats with large, incomplete thoracic spinal cord injury resulting in severe bladder impairment. Lower urinary tract function was assessed by urodynamics with implanted bladder catheter and external urethral sphincter electrodes, allowing for repeated measurements over time. Immediately after the last micturition cycle in the urodynamic investigation, PVR was first assessed by ultrasound using a 7.5 MHz linear probe and then by manually expelling the urine via gentle pressure on the abdomen.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

PVR was measured by ultrasound and by manually expelling the urine. Paired t test was used to analyze the difference between the two measurements 1 and 2 wk after spinal cord injury.

RESULTS AND LIMITATIONS

PVR assessed by ultrasound was equal to and not statistically different from the volumes obtained by manual expulsion in intact rats, both before injury and during the first 2 wk after spinal cord injury (intact: 0.16 ± 0.07 vs 0.14 ± 0.09 ml, p =  0.08; week 1: 1.67 ± 0.53 vs 1.71 ± 0.55 ml, p =  0.67; week 2: 1.16 ± 0.35 vs 0.98 ± 0.43 ml, p =  0.11). The main limitation of ultrasound for measuring PVR is the restricted availability of ultrasound machines in animal research laboratories.

CONCLUSIONS

Ultrasound is a valuable translational tool to measure PVR in awake rats reflecting the situation in humans.

PATIENT SUMMARY

We measured postvoid residual by ultrasound in awake rats, analogous to clinical examination in humans. Ultrasonography provided similar values to the generally used manual bladder expulsion.