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.

Urethral Sensitivity in Incontinent Women

OBJECTIVES

The aim of this study was to ascertain whether frequent voiding and urge incontinence are associated with supersensitivity to electrical stimulation in the posterior urethra.

METHODS

Current perception thresholds (CPT) were tested at four stimulus frequencies (1, 3, 20, and 100 Hz; duration 0.5 ms) using a square-wave constant current electrical stimulator connected to ring electrodes on a urethral catheter. The strength of the current at the first tingling sensation was regarded as the CPT. CPT analysis and cystometry were performed on 61 women (ages 28-89 years).

RESULTS

CPTs were significantly higher at lower than at elevated stimulus frequencies, and they were also generally higher in old than in younger patients. Seven women repeated the CPT test after two months, and the thresholds were unchanged. There were no significant differences in sensitivity between patient groups with stress incontinence, urge, or mixed symptoms. Moreover, CPT was not significantly related to bladder volume at first sensation of filling.

CONCLUSION

Measuring CPT is an easy and reproducible method of testing urethral sensibility, but our results do not support the suspicion that urethral hypersensitivity is involved in increased voiding frequency and urge incontinence.

The basics behind bladder pain: A review of data on lower urinary tract sensations

Interstitial cystitis is a syndrome consisting of frequency, urgency, and bladder pain that increases with bladder filling and improves temporarily after voiding. The exact cause or causes are not as yet fully understood. This leads to uncertainty in diagnosis and treatment. There is need for more knowledge, and to acquire this for more research. The fact that the condition causes pain, a pathologic stimulation of sensory fibres, makes understanding the basic sensory mechanisms in the lower urinary tract in normal and pathologic conditions mandatory. In this article we review the data on bladder sensation from the last 25 years and the possible relation with painful bladder syndrome.

Quest for standardisation of electrical sensory testing in the lower urinary tract: the influence of technique related factors on bladder electrical thresholds

AIMS

The aim of this study is to determine the influence of technique-related factors on bladder electrical thresholds in order to establish more standardisation in electrical sensory testing in the lower urinary tract (LUT).

METHODS

In 51 young healthy volunteers, electrical thresholds were determined in the bladder by using different techniques described in the literature. Within an individual, thresholds were repeatedly determined in the bladder while varying the position of the stimulating electrodes and the intravesical volume.

RESULTS

The height of bladder electrical thresholds is influenced by the position of the stimulating electrodes and the volume of the intravesical fluid at the time of the examination. By filling the bladder, the sensitivity of the bladder toward electrical stimulation can be increased.

CONCLUSIONS

Although the techniques to test electrical sensitivity have already proven to be a valuable tool in diagnosing the presence of neuropathy in the LUT, its full scope can only be evaluated after standardisation. Therefore, it is proposed that the position of the stimulating electrodes and the bladder volume at the time of the examination should be outlined in studies and standardised.

Transurethral microwave thermotherapy: how does it work?

Although some authors have proposed that the favorable impact of transurethral microwave thermotherapy (TUMT) for benign prostatic hyperplasia has only a placebo effect, this idea is inconsistent with the findings of a number of sham-controlled clinical trials. Histologic and immunohistochemical studies have shown that the nerve fibers in the periurethral tissue are damaged or ablated by TUMT, and it appears that the heat affects the innervation of the smooth muscle cells. Among the nerves damaged are the sensory neurons of the posterior urethra, and this change might reduce the excitatory signals from the urethrodetrusor facilitating reflexes. Necrosis and apoptosis within a limited area also have been described. Thus, there is likely more than one basis for the therapeutic effect of TUMT.

Elevation of sensory thresholds in the prostatic urethra after microwave thermotherapy

OBJECTIVES

To determine whether transurethral microwave thermotherapy (TUMT) affects the sensory threshold in the posterior urethra and whether such an effect influences urinary storage symptoms.

PATIENTS AND METHODS

The sensory threshold was measured before and at 3 and 12 weeks after TUMT in 13 men with minor obstructive symptoms caused by benign prostatic hyperplasia. Sensations were evoked by electrical stimulation at different frequencies, using a bipolar ring-electrode mounted on a urethral catheter. Changes in sensory thresholds were evaluated in the patients both as a group and individually. The patients were interviewed about their symptoms at each measurement.

RESULTS

After TUMT, 12 patients were satisfied and reported decreased irritative symptoms, primarily less frequent nocturnal micturition; two patients were cured of urgency incontinence. In 11 of the satisfied patients, and the unsuccessful patient, decreased urge accompanied increased sensory thresholds. Thresholds elevated by >/= 30% were correlated with decreased irritative symptoms.

CONCLUSIONS

TUMT decreases sensitivity in the posterior urethra, which may alleviate storage symptoms.

Study on the correlation between subjective perception of bladder filling and the sensory threshold towards electrical stimulation in the lower urinary tract

In 426 urodynamic patients with or without a neuropathic bladder sensation in the lower urinary tract was determined with 2 different investigation methods. During medium-fill cystometry the perception of filling was evaluated. At each sensation the bladder volume and detrusor pressure were noted. The electrical threshold was determined at different areas of the lower urinary tract with constant current stimulation. No correlation was found between the volume and pressure variables at which filling perception occurred and the electrical sensory thresholds. The levels of sensory threshold of the bladder and urethra in sensory urgency and hyposensitive bladder cases were not different from those seen in the normosensitive patients. Of the patients with disturbed or absent electrosensation 18% had a normal filling perception. Filling perception and electrosensation seem to correspond with 2 different areas of the sensory innervation of the lower urinary tract. To gain a maximum of information on bladder sensation, electrosensation as part of exteroceptive perception and filling perception as part of proprioception should be studied.