The promise of urethral pressure reflectometry: an update

A Mechanics-Based Perspective on the Function of Human Sphincters During Functional Luminal Imaging Probe Manometry

Functional luminal imaging probe (FLIP) is used to measure cross-sectional area (CSA) and pressure at sphincters. It consists of a catheter surrounded by a fluid filled cylindrical bag, closed on both ends. Plotting the pressure-CSA hysteresis of a sphincter during a contraction cycle, which is available through FLIP testing, offers information on its functionality, and can provide diagnostic insights. However, limited work has been done to explain the mechanics of these pressure-CSA loops. This work presents a consolidated picture of pressure-CSA loops of different sphincters. Clinical data reveal that although sphincters have a similar purpose (controlling the flow of liquids and solids by opening and closing), two different pressure-CSA loop patterns emerge: negative slope loop (NSL) and positive slope loop (PSL). We show that the loop type is the result of an interplay between (or lack thereof) two mechanical modes: (i) neurogenic mediated relaxation of the sphincter muscle or pulling applied by external forces, and (ii) muscle contraction proximal to the sphincter which causes mechanical distention. We conclude that sphincters which only function through mechanism (i) exhibition NSL whereas sphincters which open as a result of both (i) and (ii) display a PSL. This work provides a fundamental mechanical understanding of human sphincters. This can be used to identify normal and abnormal phenotypes for the different sphincters and help in creating physiomarkers based on work calculation.

Current and future perspectives on the utility of provocative tests of anal sphincter function: A state-of-the-art summary

BACKGROUND

The maintenance of fecal continence depends upon coordinated interactions between the pelvic floor, anorectum, and anal sphincter complex orchestrated by central and peripheral neural activities. The current techniques to objectively measure anorectal function rely on fixed diameter catheters placed inside the anal canal with a rectal balloon to obtain measurements of anal resting and squeeze function, and rectal compliance. Until recently it had not been possible to measure the distensibility of the anal canal, or in other words its ability to resist opening against an increasing pressure, which has been proposed as the main determinant of a biological sphincter's function. Anal acoustic reflectometry (AAR) and the functional lumen imaging probe (FLIP) are two novel, provocative techniques that dynamically assess the anal sphincter complex under volume-controlled distension. In doing so, both provide information on the viscoelastic properties of the anal canal and offer new insights into its function.

PURPOSE

This review details the current and potential future applications of AAR and FLIP and highlights the unanswered questions relevant to these new technologies.

Effect of a 5-HT2c receptor agonist on urethral closure mechanism in healthy women

AIMS

To evaluate the effect of ASP2205, a selective serotonin 5-HT_2c receptor agonist, and Duloxetine on the urethral pressure in healthy female subjects.

METHODS

Healthy females aged 18 to 55 years were recruited for this phase 1, single site, placebo-controlled, randomized, four-period, cross-over study. The interventions were single oral doses of 10 and 60 mg ASP2205, 80 mg duloxetine, and placebo. As a pharmacodynamics endpoint, opening urethral pressure (OUP), corrected for placebo, was measured using urethral pressure reflectometry under both resting and squeezing condition of the pelvic floor at predose and 3, 6, 12, and 24 hours after dosing. Safety and tolerability of ASP2205 were also compared with duloxetine and placebo.

RESULTS

Eighteen healthy women signed informed consent, however, one dropped out before dosing and one dropped out after the first period, therefore, 16 subjects completed the study. Duloxetine significantly increased the OUP during both resting and squeezing condition (maximal increase 18.1 and 16.8 cmH₂ O, respectively). Both doses of ASP2205 did not increase OUP at any time point. During squeezing OUP decreased significantly in the ASP2205 60 mg group from 6 to 24 hours after dosing. All subjects experienced predominantly central nervous system-related side effects (eg, dizziness and nausea) during ASP2205 treatment, which was most pronounced at 60 mg.

CONCLUSIONS

ASP2205, a serotonin 5-HT_2c receptor agonist, does not increase the urethral pressure and it is therefore unlikely that 5-HT _2c receptor agonists can be used as a treatment for stress urinary incontinence. ASP2205 was less well tolerated than the high dose of duloxetine.

Does assessing urethral function allow the selection of the optimal therapy for recurrent SUI? Report from the ICI-RS 2017

AIMS

The management of recurrent stress urinary incontinence following failed previous continence surgery remains challenging. Whilst the role of urodynamic investigations has been questioned in the management of primary stress incontinence there is a widely held view that women with recurrent symptoms require further investigation although there is no agreement regarding which tests are required. We sought to understand what testing is recommended prior to managing this difficult cohort of patients.

METHOD

This research proposal was presented at the International Consultation on Incontinence Research Society (ICI-RS) in order to clarify our current knowledge regarding the assessment of urethral function and to set research priorities for the future.

RESULTS

Whilst the majority of clinicians would advocate urodynamic evaluation of women with recurrent stress incontinence following previous surgery there is no consensus of opinion as to which tests should be performed, on whom or where. The available evidence to date suggests that urethral function tests do have a role with regard to prognosis following surgery and also in planning the most appropriate surgical intervention.

CONCLUSION

The ICI-RS developed a list of research questions which may be able to assist in improving the investigation and management of women with recurrent SUI. Questions included whether patients felt the information gained via urethral function tests had an important role in their counseling regarding outcome of repeat SUI surgery.

The urethral closure mechanism is deteriorated after anterior colporrhaphy

INTRODUCTION AND HYPOTHESIS

Urethral pressure reflectometry (UPR) has proven highly reproducible in women with pelvic organ prolapse. We hypothesized that urethral parameters would decrease after anterior colporrhaphy.

METHODS

A prospective, observational study where women with anterior vaginal wall prolapse ≥stage II were assessed before and after anterior colporrhaphy. Assessments consisted of prolapse staging according to the Pelvic Organ Prolapse Quantification system, UPR measurements at rest, during squeezing and straining (at a standardized abdominal pressure of 50 cmH₂O, P_{O-Abd 50}), standardized stress tests with 300 ml saline, and answering the International Consultation on Incontinence - Urinary incontinence short form. Stress urinary incontinence (SUI) was defined as a positive stress test and a questionnaire with symptoms of SUI and a bother score > 1. Sample size was 30, power was 100% and the level of significance was 5%. We analyzed data with paired t-tests or non-parametric Wilcoxon signed rank tests; p-values <0.05 were considered statistically significant.

RESULTS

Twenty-eight women who underwent anterior colporrhaphy completed the study. P_{O-Abd 50} decreased 12 cmH₂O after surgery (p < 0.0001). Five women developed postoperative SUI and one had persistent SUI; the six women's preoperative P_{O-Abd 50} was lower than the rest (p < 0.01). If preoperative P_{O-Abd 50} was ≤65 cmH₂O, the positive predictive value for postoperative SUI was 50%, and if P_{O-Abd 50} was ≥85 cmH₂O, the negative predictive value was 100%.

CONCLUSIONS

The urethral closure mechanism deteriorates after anterior colporrhaphy. Using UPR, we can calculate a woman's risk of SUI after anterior colporrhaphy.

Posterior colporrhaphy does not affect the urethral closure mechanism

INTRODUCTION AND HYPOTHESIS

Studies have suggested that a posterior vaginal wall prolapse might compress the urethra and mask stress urinary incontinence (SUI), much like an anterior vaginal wall prolapse. A recent study with urethral pressure reflectometry (UPR) has shown that the urethral closure mechanism deteriorates after anterior colporrhaphy; this could explain the occurrence of postoperative de novo SUI. We hypothesized that urethral pressure would also decrease after posterior colporrhaphy.

METHODS

This was a prospective, observational study where women with posterior vaginal wall prolapse ≥stage II were examined before and after posterior colporrhaphy. We performed prolapse staging according to the Pelvic Organ Prolapse Quantification system, UPR measurements at rest, during squeezing and straining, and standardized stress tests with 300 ml saline. The women filled out International Consultation on Incontinence-Urinary incontinence (ICIQ-UI) short forms. The sample size was 18, with a power of 99.9% and a level of significance of 5%. Parameters were compared using paired t tests or Fisher's exact test, where appropriate; p values <0.05 were considered statistically significant.

RESULTS

Eighteen women with posterior vaginal wall prolapse ≥stage II were recruited. One woman did not undergo surgery. There were no changes in urethral pressure at rest (p = 0.4), during squeezing (p = 0.2) or straining (p = 0.2), before and after surgery. The results of the stress tests and ICIQ-UI short forms were the same after surgery.

CONCLUSIONS

The urethral closure mechanism is not affected by posterior colporrhaphy. Our study does not support the theory that the posterior vaginal wall prolapse compresses the urethra and masks SUI.