Striated urethral sphincter activity does not alter urethral pressure during filling cystometry

The Maximal Urethral Pressure at Rest and during Normal Bladder Filling Is Only Determined by the Activity of the Urethral Smooth Musculature in the Female

The aim of this opinion paper is to determine the entities that define the maximal urethral pressure (MUP) during rest and during bladder filling that is needed to guarantee continence in females. For the development of this opinion, the literature was searched for via the Pubmed database and historic sources. Animal studies indicate that the maximal urethral pressure is determined by the smooth muscle activity in the mid-urethra. Additionally, during increased smooth muscle tone development, the largest sympathetic responses are found in the middle part of the urethra. This could be confirmed in human studies that are unable to find striated EMG activity in this area. Moreover, the external urethral striated sphincter is situated at the distal urethra, which is not the area with the highest pressure. The external urethral sphincter only provides additional urethral pressure in situations of exertion and physical activity. From a physics point of view, the phasic pressure of the external striated sphincter at the distal urethra cannot be added to the tonic pressure generated by the smooth muscle in the mid-urethra. The assertion that mid-urethral pressure is the result of different pressure forces around the urethra, including that of the external striated sphincter, is not supported by basic research evidence combined with physical calculation and should therefore be considered a misconception in the field of functional urology.

Aging and overactive bladder may be associated with loss of urethral sensation in women

AIMS

To compare current perception thresholds (CPT) in the urethra and bladder of women with idiopathic overactive bladder to asymptomatic controls.

METHODS

Women with > or =1 urge urinary incontinence (UUI) episode per week on 7-day diary, seeking treatment for UUI underwent CPT testing using a Neurometer(R) CPT device (Neurotron, Inc., Baltimore, MD). Testing was done in the urethra and bladder at three frequencies 2,000, 250, and 5 Hz corresponding to A-beta, A-delta, and C fibers, respectively. CPT values from the women with UUI were compared to CPT values from a group of control women without lower urinary tract symptoms.

RESULTS

Forty-eight controls without lower urinary tract symptoms and 13 women with UUI were included in the analysis. Women with UUI were significantly older (mean +/- SD age 62 +/- 14 and 44 +/- 15, P < 0.0005) and more likely to be vaginally parous (P = 0.007) than control women. Urethral CPT at 2,000, 250, and 5 Hz were significantly higher in women with UUI than controls, while bladder CPT were not different between groups. Using logistic regression, to control for age and parity, urethral CPT at 5 Hz remained significantly higher in women with UUI than controls (P = 0.013).

CONCLUSION

Urethral sensation is significantly higher in older women, suggesting sensory neuropathy in the lower urinary tract increases with age and may contribute to the increase in overactive bladder seen with aging. These data reinforce the role of the urethra in lower urinary tract function.

The Volume at Which Women Leak First on Urodynamic Testing is Not Associated With Quality of Life, Measures of Urethral Integrity or Surgical Failure

PURPOSE

We determined if the bladder volume at which urodynamic stress incontinence is first detected is related to preoperative quality of life, urethral sphincter assessment or surgical outcome in women undergoing continence surgery.

MATERIALS AND METHODS

Charts of consecutive women who underwent a sling or Burch procedure were reviewed. Preoperative and postoperative assessment included the Incontinence Impact Questionnaire and Urogenital Distress Inventory. Urodynamic stress incontinence volume is the bladder volume at which urodynamic stress incontinence was first detected. Women were divided into 4 groups according to urodynamic stress incontinence volume, and compared with respect to maximum urethral closure pressure, Valsalva leak point pressure, Incontinence Impact Questionnaire and Urogenital Distress Inventory. Urodynamic stress incontinence persistence was evaluated only in patients who had sling surgery.

RESULTS

A total of 168 women were recruited for the study. Urodynamic stress incontinence volume was 100 ml for 31% of women, 200 ml for 17%, 300 ml for 17% and 400 ml or greater for 35%. Baseline and postoperative Urogenital Distress Inventory, Incontinence Impact Questionnaire, maximal urethral closure pressure and Valsalva leak point pressure did not differ by urodynamic stress incontinence volume. Among the 116 patients who had the sling procedure, urodynamic stress incontinence persistence did not differ by urodynamic stress incontinence volume (p=0.72).

CONCLUSIONS

Women who demonstrate urodynamic stress incontinence at lower bladder volumes do not report greater bother from incontinence than women who leak at higher volumes, suggesting leakage severity on urodynamics is not an adequate reflection of incontinence related quality of life.

Magnetic resonance-based female pelvic anatomy as relevant for maternal childbirth injury simulations

The objectives of the study are to review the female pelvic floor anatomy relevant to childbirth simulations, to discuss available methods for clinical evaluation of female pelvic floor function, and to review the variation in pelvic floor changes after vaginal childbirth. A high-resolution magnetic resonance (MR) data set from an asymptomatic nullipara was used to illustrate the MR anatomy of the female pelvic floor. Manual segmentation was performed and three-dimensional reconstructions of the pelvic floor structures were generated, which were used to illustrate the 3D anatomy of the pelvic floor. Variation in the post partum appearance of the levator ani muscles is illustrated using other 2D MR data sets, which depict unilateral and bilateral disruptions in the puborectalis portion of levator ani, as well as shape variations, which may be seen in the post partum levator. The clinical evaluation of the pelvic floor is then reviewed. The female pelvis is composed of a bony scaffold, from which the pelvic floor muscles (obturator internus, levator ani) are suspended. The rectum fits in a midline groove in the levator ani. The vagina is suspended across the midline, attaching bilaterally to the obturator and levator ani. The vagina supports the bladder and urethra. MR studies have demonstrated disruptions in levator ani attachments after vaginal childbirth. Such disruptions are rare in women who have not given birth vaginally. Changes to the neuromuscular apparatus of the pelvic floor can also be demonstrated after vaginal delivery. The combination of childbirth-related anatomic and neurological injury to the pelvic floor may be associated with pelvic floor dysfunction (PFD). These changes are difficult to study in vivo but may be studied through simulations. Appropriate consideration of clinical anatomy is important in these simulations.

Urodynamic assessment of sphincteric function in the incontinent female: which test, and does it matter anyway?

The overall prevalence of urinary incontinence among women surveyed in the United States is approximately 37%. The lifetime risk of undergoing urinary incontinence surgery for women in the United States is estimated to be 11.1%. Conservative therapy can be instituted without performing extensive evaluation such as urodynamics, voiding cystourethrograms, ultrasonography, or video studies. Further evaluation is recommended when conservative measures have failed or if invasive, potentially morbid surgical therapies are being considered. This paper reviews the available methods for evaluating the urinary sphincter in the incontinent female.

Facilitatory Neuromodulative Effect of Duloxetine on Pudendal Motor Neurons Controlling the Urethral Pressure: A Functional Urodynamic Study in Healthy Women

OBJECTIVE

The aim of this functional urodynamic experiment in healthy women was to study the effect of duloxetine, which is a combined serotonin and norepinephrine (5-HT/NE) reuptake inhibitor, on urethral resting pressure, excitability of pudendal motor neurons, and urethral sphincter contractility.

METHODS

In 11 healthy female subjects three baseline urethral pressure profiles (UPPs) were obtained to study resting pressure. Afterward the individual motor threshold (MT) for external urethral sphincter (EUS) contraction in response to transcranial magnetic stimulation (TMS) was determined to study the excitability of pudendal motor neurons. Another three UPPs were recorded while sacral root magnetic stimulation (SMS) was performed to evoke reproducible urethral contractions to study urethral sphincter contractility. Then the women received 40 mg duloxetine and the protocol was repeated 4 h after drug administration. The resting pressure values, MT values following TMS, and the EUS pressure amplitudes in response to SMS obtained at baseline were statistically compared to the corresponding values at follow-up after duloxetine.

RESULTS

Oral administration of duloxetine significantly lowered MT for EUS contraction in response to TMS (p=0.013). In addition, duloxetine significantly increased EUS pressure amplitudes in response to SMS (p=0.0007, 5 of 11 subjects evaluated) but did not change urethral resting pressures.

CONCLUSIONS

This is the first functional, urodynamic controlled study to show that the combined 5-HT/NE reuptake inhibitor duloxetine has a significant effect on the excitability of pudendal motor neurons and on urethral sphincter contractility in healthy women in vivo but no significant effect on urethral resting tone. Our data confirm a facilitatory neuromodulative effect of duloxetine on sphincter motor neurons in humans.