Electrophysiological correlates of sensory innervation of the vesico-urethral junction and urethra in man

To investigate urethral sensory innervation in man, cerebral evoked potentials (CEPs) and bulbocavernous reflex (BCR) were recorded by stimulation of vesico-urethral junction (VUJ), prostatic and distal urethra, and penile skin. A specially produced catheter with a pair of electrodes was used for bipolar stimulation along the lower urinary tract. In comparison to the potentials evoked by distal urethral stimulation, the shape differences and protracted latency of CEPs to VUJ stimulation suggest that the distal and proximal urethra are innervated by different peripheral afferents. Similarities of CEPs and BCR latencies produced by prostatic urethral and VUJ stimulation indicate that the sensory innervation of the prostatic urethra is provided by pelvic nerve afferents. The remaining distal parts of the urethra are innervated by pudendal nerves. This is indicated by shape similarities and latency characteristics of both CEPs and BCR when the distal urethra and glans skin are stimulated.     

Urethral sensitivity and the impact on urinary continence in patients with an ileal bladder substitute after cystectomy

PURPOSE: After cystectomy and ileal bladder substitution, sensitivity in the membranous urethra correlates with postoperative urinary continence. We determine whether sensitivity is decreased only in the most proximal part of the urethra or also more distally in the bulbar urethra, which would give some indication as to which nerves may be injured during radical cystoprostatectomy. MATERIALS AND METHODS: The sensory threshold for electrical stimulation was measured with double ring electrodes in the membranous urethra, and 2.5 cm. distally to it in 41 men after cystectomy and ileal bladder substitution, and in a control group of 29 men. RESULTS: The mean sensory threshold plus or minus standard deviation of the membranous urethra was 9 +/- 2 mA. in the control group compared to 26 +/- 11 mA. in the postoperative group (p <0.001). Mean sensory threshold 2.5 cm. distal to the membranous urethra was 8 +/- 3 versus 9 +/- 3 mA. in the control and postoperative groups, respectively (not significant). Patients with daytime continence had a mean threshold of 22 +/- 8 mA. in the membranous urethra compared to 38 +/- 11 mA. in those who were incontinent (p <0.004) and a threshold of 8 +/- 3 mA. 2.5 cm. distal to the membranous urethra compared to 8 +/- 2 mA. in those who were incontinent (not significant). CONCLUSIONS: After cystectomy and ileal bladder substitution, urethral sensitivity 2.5 cm. distal to the membranous urethra is unaffected by surgery and does not correlate with postoperative continence. In contrast, a decreased sensitivity in the membranous urethra correlates with an increased risk of postoperative incontinence. Preservation of sensitivity in the membranous urethra seems to be an important factor for achieving continence after cystectomy and ileal bladder substitution, and does not seem to be dependent on the extrapelvic portion of the pudendal nerve.     

Urethral sensation following reconstructive pelvic surgery

Introduction and hypothesis

Most urethral neuromuscular function data focus on efferent rather than afferent innervation. We aimed to determine if changes exist in urethral afferent nerve function before and after reconstructive pelvic surgery (RPS). Secondarily, we compared afferent urethral innervation in women with and without stress urinary incontinence undergoing RPS.

Methods

Participants underwent current perception threshold (CPT) and urethral anal reflex (UAR) testing prior to surgery and again post-operatively. Wilcoxon signed ranked test and Spearman’s correlations were used and all tests were two-sided. p?=?0.05 was considered to indicate statistical significance.

Results

Urethral CPT thresholds increased significantly after RPS, consistent with decreased urethral afferent function. Pre-operative urethral CPT thresholds at 5 and 250 Hz were lower in SUI women (10 [IQR 5–29], 40 [32–750]) compared with continent women (63 [14–99], 73 [51–109]; p?=?0.45, p?=?0.020), signifying increased urethral sensation or easier activation of urethral afferents in SUI women.

Conclusions

Reconstructive pelvic surgery is associated with a short-term deleterious impact on urethral afferent function, as demonstrated by the higher levels of stimuli required to activate urethral afferent nerves (decreased urethral sensation) immediately after RPS. Women with SUI required lower levels of stimuli to activate urethral afferent nerves prior to RPS, although UAR latencies were similar regardless of concomitant SUI.     

INEFFICIENT URETHRAL MILKING SECONDARY TO URETHRAL DYSFUNCTION AS AN ADDITIONAL RISK FACTOR FOR INCONTINENCE AFTER RADICAL PROSTATECTOMY

PURPOSE: Continence after radical prostatectomy is thought to depend completely on the striated urethral sphincter. However, some patients complain only of occasional post-void dribbling. Therefore, we determined whether urethral dysfunction may be another cause of incontinence. MATERIALS AND METHODS: The sensory threshold of electric stimulation was measured by double ring electrodes in the membranous urethra and 2.5 cm. distal in 29 men before and in 29 after radical retropubic prostatectomy. In addition, voiding cystourethrography was performed in 66 patients before and in 49 after surgery to determine complete post-void urethral emptying or milking. RESULTS: The mean sensory threshold of the membranous urethra was 15 +/- 3 mA. preoperatively versus 38 +/- 17 postoperatively (p <0.0001). The sensory threshold 2.5 cm. further distal was 12 +/- 5 mA. before and 10 +/- 4 after radical prostatectomy, which was not statistically significant. Postoperatively in completely continent patients and in those with dribbling the mean threshold was 32 +/- 12 and 43 +/- 18 mA. in the membranous urethra (p = 0.09), and 11 +/- 4 and 9 +/- 4 mA. in the bulbar urethra, respectively, which was not statistically significant. Of the 66 patients 36 (55%) showed post-void urethral milking before surgery but only 8 of 49 (16%) showed it postoperatively (chi-square test p <0.0001), including 7 who were completely continent and 1 who complained of occasional post-void dribbling. CONCLUSIONS: After radical prostatectomy sensitivity of the membranous but not of the bulbar urethra is affected, correlating with postoperative continence. In addition, post-void dribbling seems to be associated with the loss of urethral milking. We conclude that preserving urethral function is another important continence factor after radical prostatectomy.     

Permanent retention following radical hysterectomy

Urodynamic findings associated with permanent retention after radical hysterectomy are presented and discussed in the light of previous observations made in women rendered severely incontinent by the operation. These findings suggest that if the operation ablates the micturition reflex, some reduction in urethral pressure is required to achieve balanced bladder function. They also demonstrate that opposite extremes of proximal urethral pressure can occur after a radical hysterectomy and that they are associated with diametrically opposite types of urinary dysfunction even if detrusor function is identical. It is difficult to reconcile these observations with histochemical data which suggest a purely cholinergic efferent nerve supply to the proximal urethra.     

Urethral and bladder current perception thresholds: normative data in women

PURPOSE: Given increased evidence of sensory dysfunction in lower urinary tract pathology, we determined normative current perception threshold values in the lower urinary tract of asymptomatic women. MATERIALS AND METHODS: After receiving institutional review board approval women without lower urinary tract symptoms underwent current perception threshold testing of the urethra and bladder using a Neurometer constant current stimulator. Current perception threshold values were determined at 3 frequencies, including 2,000 Hz (corresponding to A-beta fibers), 250 Hz (corresponding to A-delta fibers) and 5 Hz (corresponding to C fibers). RESULTS: A total of 48 women with a mean age of 38 years (range 23 to 67) underwent current perception threshold testing. Normative values were established for the urethra and bladder at 2,000, 250 and 5 Hz. Median urethral current perception thresholds at 2,000, 250 and 5 Hz were 1.2 (IQR 0.76-1.5), 0.45 (IQR 0.33-0.56) and 0.11 mA (IQR 0.07-0.24), respectively. Median bladder current perception thresholds at 2,000, 250 and 5 Hz were 4.1 (IQR 2.0-6.3), 2.3 (IQR 0.87-5.5) and 1.4 mA (IQR 0.22-2.9), respectively. Urethral and bladder current perception thresholds increased significantly with subject age at all 3 frequencies (p<0.0005). Prior pelvic surgery was associated with an increased bladder current perception threshold at all 3 frequencies (p<0.005) but not with the urethral current perception threshold. CONCLUSIONS: We report urethral and bladder current perception thresholds for a large sample of asymptomatic women. These reference values may help elucidate changes in afferent nerve function in women with lower urinary tract dysfunction.     

Studies of the neurogenic bladder.

A series of 36 patients with specific neurological lesions affecting those parts of the nervous system thought to be involved in the control of bladder function have been studied by urodynamic, electromyographic and neurohistochemical means and the results compared with those obtained in 20 control subjects. In patients with pelvic nerve injury urethral sphincter electromyography (EMG) revealed abnormal motor units and the density of bladder innervation was significantly reduced (P less than 0.01). By contrast, in patients with distal autonomic neuropathy the innervation of the striated muscle of the urethra was unaffected and although there was an almost total loss of nerves from the bladder muscularis, the subepithelial plexus of nerves was preserved. In patients with progressive autonomic failure and multiple system atrophy, the bladder neck was incompetent in every case and the striated muscle of the urethra was affected by a process of denervation and re-innervation. These findings serve to distinguish patients with autonomic failure from those with idiopathic Parkinson's disease and influence the selection of patients for transurethral surgery.     

Effects of selective autonomic and pudendal denervation on the urethral function and development of retention in female dogs

PURPOSE: This trial is an experimental approach to the possible causes of continence and voiding problems after urethra sparing radical cystectomy and orthotopic bladder substitution in women. MATERIALS AND METHODS: Between January 1996 and January 1999 we included 24 mongrel female dogs in this 4-phase study of 6 dogs each. The effects of autonomic denervation of the urethra (phase 1) and urethral transection just distal to the bladder neck (phase 2) on the urethral pressure profile were recorded. In phase 3 the effects of autonomic denervation, urethral transection and pharmacological manipulation of the denervated transected urethra on the urethral pressure profile were studied in succession. In phase 4 the effects of pudendal nerve transection and pharmacological blockade were recorded. In the 12 phases 2 and 3 dogs the transected urethra was re-anastomosed to the bladder neck. Acute experiments were repeated after 2 and 6 months, urethrocystoscopy was done and post-void residual urine was estimated. Two of the latter dogs were sacrificed 6 months after the acute experiment and the urethras were histopathologically examined. RESULTS: Autonomic denervation resulted in a 46% to 48% decrease in mean maximal pressure in the proximal urethra in phases 1 and 3 (p <0.001) with no significant effect on the distal urethra. Urethral transection in phase 2 did not affect the urethral pressure profile. Phentolamine injection after urethral denervation and transection in phase 3 produced a further reduction of 11.3% and 46.3% in mean resting pressure in the proximal and distal urethra, respectively, while succinyl choline produced a 38.1% further decrease in the distal urethra. Unilateral and bilateral pudendal denervation reduced pressure in the distal urethra significantly but not in the proximal urethra. When phentolamine was given thereafter, a further decrease of 38% and 2.4% resulted in resting pressure values in the proximal and distal urethra, respectively. The change in distal urethral pressure was marginally significant after succinyl choline injection (p = 0.05). Results were reproducible after 2 and 6 months. The proximal urethra remained patent with no post-void residual urine after autonomic denervation. There was no significant urethral fibrosis after realignment of the transected urethra in the 2 sacrificed phases 2 and 3 dogs. CONCLUSIONS: From this study we concluded that autonomic denervation reduced pressure in the proximal urethra by less than 50%. Continuity of the urethra with the bladder is not necessary for proper urethral function. After autonomic denervation the proximal urethra remained patent with no subsequent fibrosis. In addition, no post-void residual urine was noted. Bilateral pudendal denervation did not completely block activity of the distal urethra. The nonneuromuscular components had a small role in the creation of urethral closure function.     

Colour Doppler ultrasonography of female urethral vascularization in normal young volunteers: a preliminary report

OBJECTIVE: To assess urethral vascularization in healthy young women, using colour Doppler ultrasonography. SUBJECTS AND METHODS: Eleven healthy young women volunteers (mean age 33.6 years, range 24-46) with no pelvic floor disorders and no history of incontinence were assessed. The subjects underwent colour Doppler ultrasonography using a 4-7 MHz convex broadband transducer. Translabial sagittal scans of the urethra were taken when the subjects had a full bladder, both during the oestrogenic and progestogenic phases. The colour Doppler ultrasonography parameters were optimized to detect slow flows in the anterior and posterior distal, middle and proximal urethra. A rank-sum nonparametric test was used to assess differences between the resistive indices. RESULTS: The statistical evaluation showed a significant difference in the resistive index only in the anterior urethra, between the distal and middle plus proximal urethra, in both the progestogenic (P = 0.002) and oestrogenic (P = 0.0127) phases. CONCLUSIONS: This study confirmed that the vascularization of the urethra plays an important role in the 'seal' effect, which is considered one of the most important factors in urethral closure. There was a significantly greater resistive index in the anterior proximal urethra than in the middle and distal urethra. These findings suggest that the seal effect is related to the existence of a rich venous urethral vascularization, involved in the mechanism of urethral closure. Colour Doppler ultrasonography of the urethra seems to be feasible and useful for understanding the mechanism of the vascular component in female continence.     

Relationship between the integrity of the pelvic floor muscles and early recovery of continence after radical prostatectomy

PURPOSE: We investigated how the preoperatively estimated integrity of pelvic floor muscles related to the recovery of continence after radical prostatectomy. MATERIALS AND METHODS: A total of 94 patients underwent magnetic resonance image of the prostate and urodynamic studies before undergoing radical prostatectomy and evaluation of voiding symptoms before, and 3 and 6 months after surgery. Incontinence was defined as any unwanted urine leakage. On the magnetic resonance image the thickness of the levator ani and pelvic diaphragm, and prostate volume were measured to correlate with continence status. RESULTS: Incontinence was noted in 41.5% and 15.9% of the patients at 3 and 6 months, respectively. Recovery of continence 3 months after RP was related to the thickness of the pelvic diaphragm on sagittal imaging (p=0.017), the ratio of the levator ani on the axial image to prostate volume (p=0.047), functional urethral length (p=0.007) and incontinence before surgery (p=0.009). Recovery at 6 months was related to neurovascular bundle sparing (p=0.013) and marginally to the pelvic diaphragm on sagittal imaging (p=0.059). On multivariate analysis the pelvic diaphragm on sagittal imaging (HR 2.455, 95% CI 0.894-6.739, p=0.008) and the ratio of the levator ani on the axial image to prostate volume (HR 1.886, 95% CI 0.952-3.736, p=0.011) significantly predicted continence at 3 months, while at 6 months only the pelvic diaphragm on sagittal imaging showed a significant relationship (p=0.024). CONCLUSIONS: Pelvic diaphragm thickness and the ratio of levator ani thickness to prostate volume are independent factors predictive of post-prostatectomy incontinence. Patients with better developed pelvic floor muscles, especially in relation to the size of the prostate, can be expected to achieve earlier recovery of continence after radical prostatectomy.     

Bladder dysfunction after proximal urethrolysis in female dogs.

BACKGROUND: Functional changes in the bladder after proximal urethrolysis are not recognized, despite the development of neuroanatomical studies of the female urethra or functional studies of the urethra after cystectomy. The aim of the present pilot study is to investigate possible functional changes in the bladder after proximal urethrolysis in female dogs. METHODS: The bilateral nerve branches to the urethra were resected by separating the urethra from the anterior vaginal wall in 10 female dogs. Pre- and postoperative cystometrograms were recorded under anesthesia and the bladder capacity, threshold pressure for micturition and bladder stiffness (the inverse of compliance) were compared. RESULTS: Fourteen days postoperatively, the bladder capacity significantly decreased and the threshold pressure and bladder stiffness significantly increased. Eight weeks after surgery, the threshold pressure and bladder stiffness remained high, but the bladder capacity tended to return to baseline values. CONCLUSIONS: These results indicate that proximal urethrolysis with bilateral sections of the nerve branches to the urethra produces a low-compliant bladder in the early postoperative period and suggest that afferent stimuli from the urethra may participate in maintaining a compliant bladder during filling.     

Predictors of hysterectomy in women with common pelvic problems: a uterine survival analysis

BACKGROUND: Comprising over 600,000 patients per year, hysterectomy is the most common nonobstetrical operation performed in US women. Little is known about the natural history of the noncancerous uterine conditions leading to hysterectomy. We followed a prospective cohort of women with common pelvic problems to determine whether simple clinical characteristics could predict a subsequent hysterectomy. STUDY DESIGN: We recruited 762 women seeking care for abnormal uterine bleeding, chronic pelvic pain, or symptomatic uterine fibroids and ascertained their hysterectomy status during 4 years of surveillance. We collected baseline patient-reported sociodemographic and clinical data and fit Cox models to predict the effects of covariates on hysterectomy across patient age. RESULTS: There were 99 hysterectomies, resulting in 0.044 hysterectomies per person-year of observation and a 13.5% cumulative hysterectomy rate. Hysterectomy was independently predicted by multiple pelvic symptoms or symptomatic fibroids (hazard ratio [HR], 1.97; 95% CI, 1.18-3.28), previous use of a gonadotropin-releasing hormone agonist (HR, 2.54; 95% CI, 1.53-4.24), and an absence of symptom resolution (HR, 2.24; 95% CI, 1.46-3.44). Survival curves plotted for subgroups with combinations of these predictors showed an escalating risk of hysterectomy with each additional risk factor. Predicted hysterectomy rates ranged from 20%, if all 3 predictors were absent, to 95%, if all 3 were present. CONCLUSIONS: For women with common pelvic problems, three easily measured clinical characteristics (symptom combination, degree of resolution, and earlier use of a gonadotropin-releasing hormone agonist) predict the likelihood of subsequent hysterectomy and can be used to inform counseling about the likely success of alternative treatments.     

Urethral response to nerve stimulation measured by strain gauge force transducer

This paper presents a study of urethral responses to efferent nerve stimulation in dogs. The pelvic, hypogastric and pudendal nerves were stimulated using a programmed instrument under three different in vivo conditions. The preparations consisted of: (A) bladder, urethra, and rectum; (B) urethra and rectum, and (C) urethra only. Stimulation of the pelvic nerve in preparation A resulted in elongation and constriction of the mid and proximal urethra with a resultant rise in pressure. However, this response was reduced in preparations B and C. Similar observations were made with hypogastric nerve stimulation. The results of pudendal nerve stimulation were significantly different, in that the pressure rise occurred in the mild and distal urethra and varied in elongation response.     

Influence of sacral neuromodulation on electrosensation of the lower urinary tract

ABSTRACT PURPOSE: We prospectively investigated whether neuromodulation of the S3 root influences the sensory threshold to electrical stimulation in the lower urinary tract. MATERIALS AND METHODS: The study included 7 women and 3 men receiving S3 neuromodulation at 210 msec. and 25 Hz. with the Interstim PNE system for a mean of 5 days. Neuromodulation was done unilaterally in 6 cases and bilaterally in 4. The sensory threshold was determined by electrodes placed randomly against the mucosa of the empty bladder on the left and right sides, in the urethra in women, and in the prostatic and penile urethra in men. Thresholds were measured at each location with neuromodulation on and off. RESULTS: With bilateral neuromodulation on all 4 patients had a lower bladder threshold than with neuromodulation off. In unilateral neuromodulation the threshold was significantly lower during neurostimulation on the ipsilateral side. There was no effect on the threshold on the arm or in the urethra. The effect was noted in patients in whom neuromodulation was and was not clinically successful. CONCLUSIONS: Neuromodulation on S3 influences the nervous system involved in electrosensation of the bladder but not the skin afferent innervation or the nerves involved in urethral electrosensation. These data support the hypothesis that S3 neurostimulation is effective mainly through the afferent nervous system in the pelvic nerves.     

Role of the pelvic nerve in the dynamics of micturition in the decerebrate dog as determined by suprapubic endoscopical and urodynamic evaluation

The role of the pelvic nerves on the dynamics of micturition was evaluated in 13 decerebrate dogs, four male and nine female, by direct observation of bladder movement, by suprapubic cystoscopic observation of urethral behavior, and by pressure flow EMG studies. Experiments were performed before and after unilateral pelvic nerve transection. In control conditions and after unilateral pelvic nerve transection, the bladder neck was not tightly closed during the collecting phase, the membranous portion of the urethra opened and closed spasmodically during the emptying phase, and reflex micturition developed. Direct observation showed that after unilateral pelvic nerve transection, the ipsilateral bladder did not contract. A pressure flow EMG study showed that unilateral pelvic nerve transection produced a significant increase in threshold volume, threshold pressure, bladder compliance and residual volume, and a significant decrease in contraction pressure and flow rate. The present study shows that unilateral pelvic nerve transection has no demonstrable effect on urethral function, but has effects on bladder function during the collecting and emptying phases and that bladder innervation is unilateral in the dog.     

Role of striated and smooth muscle components in the urethral pressure profile in traumatic neurogenic bladders: a neuropharmacological and urodynamic study. Preliminary report

Urodynamic investigations with urethral pressure profile, and vesical, intrarectal and anal pressure recordings were performed in 37 patients with spinal cord lesions. The recordings were done before and after phentolamine injections and/or pudendal nerve blocks to evaluate the respective contribution of sympathetic and somatic innervation to the maximum urethral closure pressure in the mid and distal portions of the membranous urethra. A pressure gradient was demonstrated in the membranous urethra with higher values in the distal than in the mid portion. These results emphasize that the interrupted withdrawal technique is superior to the continuous technique in patients with upper motor neuron bladders. Mid urethral striated and smooth muscle components were shown to represent approximately 60 and 30 per cent of the maximum urethral closure pressure, respectively. In the distal urethra striated and smooth components are more abundant than in the mid portion and contribute in equal proportion to the maximum urethral closure pressure. No substantial role was found for the vascular bed in the maximum urethral closure pressure. The greatest pressure decrease in the mid and distal urethra of patients with lower motor neuron bladders was believed to be an effect of denervation supersensitivity. The results of pudendal blocks showed sphincter dyssynergia to be mediated through pudendal nerves via spinal reflex arcs. Phentolamine effects on bladder activity suggest that blockade of alpha-adrenergic receptors inhibits primarily the transmission in vesical and/or pelvic parasympathetic ganglia and acts secondarily through direct depression of the vesical smooth muscle. Our neuropharmacological results raise strong doubts as to the existence of a sympathetic innervation of the striated urethral muscle in humans.     

Impact of nerve sparing technique on patient self-assessed outcomes after radical perineal prostatectomy

PURPOSE: We investigated the impact of nerve sparing technique on erectile function, urinary continence and health related quality of life after radical perineal prostatectomy using a validated self-assessment questionnaire. MATERIALS AND METHODS: The Expanded Prostate Cancer Index Composite questionnaire was administered preoperatively and at defined intervals after surgery to 265 patients who underwent radical perineal prostatectomy at 2 institutions between January 2001 and December 2004. Of these patients 153 (57.7%) and 112 (42.3%) underwent nonnerve sparing and nerve sparing approaches, respectively. Kaplan-Meier analysis was used to determine time to recovery of erectile function (erections firm enough for intercourse) and urinary continence (0 pads per day). RESULTS: Median patient age was 60.6 years. Median followup was 15 months. In multivariate analysis preoperative erectile function (p = 0.005) and preservation of the neurovascular bundle (p = 0.018) were independent predictors of earlier recovery of erectile function, with hazard ratios of 2.3 (95% CI 1.2-4.6) and 4.0 (95% CI 1.5-10.3), respectively. Median time to recovery of urinary continence was 4.8 months in the nerve sparing group and 6.1 months in the nonnerve sparing group (p = 0.001). In multivariate analysis nerve sparing technique (p = 0.001, HR 1.4, 95% CI 1.1-1.9) and age (p = 0.012, HR 1.7, 95% CI 1.3-2.2) were independent predictors of recovery of continence. CONCLUSIONS: This analysis suggests that nerve sparing radical perineal prostatectomy is associated with improved recovery of urinary continence and favorable health related quality of life scores and, therefore, should be considered a viable alternative to other nerve sparing approaches.     

The effect of tamsulosin on the resting tone and the contractile behaviour of the female urethra: a functional urodynamic study in healthy women

AIMS: The aim of this functional urodynamic experiment was to study the effect of the selective alpha1(A)-blocker tamsulosin on the urethral pressure in healthy human females and assessed first the resting urethral pressure and second the urethral contractility in response to magnetic stimulation of the sacral roots. METHODS: 11 healthy female subjects gave their written informed consent and were included. A microtip pressure transducer catheter was inserted into the bladder and three baseline urethral pressure profiles were obtained. Another three urethral pressure profiles were recorded while magnetic single pulse stimulation of the sacral roots was performed above the motor threshold of the pelvic floor to evoke reproducible urethral contractions. Then the subjects received 0.4 mg of tamsulosin and the entire protocol was repeated 6 hours after drug administration. Cardiovascular monitoring was obtained during the baseline and follow-up measurements. Mean and maximal urethral pressure values calculated over the entire urethra, mean pressure values calculated over the proximal, middle and distal third of the urethra and the pressure amplitudes to magnetic stimulation at baseline were statistically compared to the follow-up measurements with tamsulosin. RESULTS: The oral administration of tamsulosin did not change the systemic blood pressure, but did significantly reduce the mean and maximal urethral pressure acquired over the entire urethra. When the proximal, middle and distal third of the urethra were analysed separately, there was a significant pressure reduction in all three segments. Amplitudes of the urethral contractions evoked by sacral magnetic stimulation remained unchanged after tamsulosin. CONCLUSIONS: These data show a significant relaxing effect of tamsulosin on the resting urethral tone in healthy females in vivo. These results may suggest tamsulosin as a new pharmacological approach to treat urinary retention due to overactive or non-relaxing urethra in women.     

Urethral function after cystectomy: a canine in vivo experiment

Summary To study the function of the pelvic floor and the isolated urethra after removal of the bladder, 5 male and 5 female mongrel dogs were used in an acute in vivo experiment. Urethral pressure changes secondary to unilateral stimulation of the pelvic and pudendal nerves were recorded. After baseline data of the intact system were documented, the following procedures were carried out: separation of the urethra from the bladder neck (prostate), nerve-sparing cystectomy (cystoprostatectomy), and cold-knife incision through the entire length of the proximal urethra. Pressure recordings were repeated after each step of surgery. Pudendal nerve stimulation resulted in rapid and large pressure rises in the distal urethra (reaction typical of striated muscle). This response remained unchanged after all three surgical steps. Pelvic nerve stimulation provoked pressure rises within the urethra of a pattern typical of smooth muscle. The findings persisted after separation of the urethra from the bladder neck (prostate) and after cystectomy, but were not observed after urethrotomy. Contractions secondary to pudendal nerve stimulation were inhibited by curare, which did not affect the reaction to pelvic nerve stimulation. Our experiments demonstrate that in the dog the continuity of bladder and urethra is not required for the function of urethral closure mechanisms. The contractile potency of the urethral smooth muscles remains intact after nerve-sparing cystectomy. We believe that problems with the baseline continence of surrogate bladders should mainly be ascribed to a lack of surgical caution in preserving the autonomic nerves of cystectomy. A poor response to stress conditions cannot be explained by damage to the neural pathway of the striated sphincter, as the pudendal nerve is not at risk during nerve-sparing cystectomy. In our opinion mechanical malfunction of the striated muscle components secondary to scarring at the site of the anastomosis is the main reason for stress incontinence after orthotopic bladder replacement.