Preliminary Observations Of A Synergistic Bladder-Sphincter Relationship Following Spinal Cord Injury In A Quadruped Animal

Abstract

Background/Objectives: High urethral resistance or detrusor-sphincter dyssynergia (DSD) is characterized by obstructed voiding during bladder contractions. DSD is caused by an exaggerated pelvic floor reflex resulting from sensory input from elevated pressure in the bladder that produces reflex constriction of the urethral sphincter. The objective of this study was to determine whether sensory input from the bladder produced synergistic or dyssynergic pelvic floor reflexes following SCI in an animal model.

Methods: A pelvic floor reflex that shares the same motor pathway with DSD is the bulbocavernosus (BC) reflex. The BC reflex was elicited with electrical stimulation in 4 male cats with T1 spinal injury, and recorded as an anal sphincter contraction. Recordings were obtained during control and elevated bladder pressures. Increased bladder pressure was induced with either manual pressure (Crede procedure) or spontaneous contractions resulting from bladder filling.

Results: During the control period, the BC reflex indicated by the peak anal pressure response was 23 ± 6 cmH20. During elevated bladder pressure of 34 ± 18 cmH20, the BC response decreased to 10 ± 3 cmH20 (not significant), showing a synergistic relationship. Anal sphincter tone between BC reflex tests showed a dyssynergic response. All4 animals showed increased tone during elevated bladder pressures that averaged 9 ± 5 cmH2 0 . Because abdominal pressure was not recorded, the significance is not clear. However, there was further support of a dyssynergic relationship based on increases in the anal and urethral electromyography recordings and some pelvic floor spasms during the elevated bladder pressure.

Conclusions: Because 2 different pelvic floor activities were observed during increased bladder pressures, this animal model may be described best as a mixed model. This model shows both synergistic and dyssynergic relationships between the bladder and the BC contractions. Although observed changes were not significant, the unique observations of synergistic bladder-sphincter activity shown by the inhibited BC reflex is in marked contrast to the strictly dyssynergic bladder-sphincter relationship seen in SCI patients.     

Dynamic Bulbocavernosus Reflex: Dyssynergia Evaluation Following SCI

ABSTRACT

High urethral resistance caused by detrusor-sphincter dyssynergia (DSD) occurs following spinal cord injury (SCI) and results in poor voiding. A major pelvic floor reflex that may be involved in DSD is the bulbocavernosus reflex (BC) and evaluation of this reflex during the micturition cycle may provide additional information regarding this role. The periodic BC observed during micturition via cystometry is described as a dynamic bulbocavernosus reflex (DBC).

The DBC was induced in upper motor neuron SCI patients using periodic dorsal penile nerve stimulation; the evoked reflex response was recorded with an anal sphincter pressure sensing balloon. Stimulation of 15–50 mA was applied at the base and dorsal side of the penis with surface electrodes, pulsed at a rate of 0.25 Hz. By applying the stimulation during cystometry, the BC reflex could be evaluated throughout the entire micturition cycle. Results showed that the DBC increased during bladder filling and bladder contractions. These findings indicate that an enhanced BC reflex is a major factor causing increased urethral resistance during micturition. (J Am Paraplegia Soc: 17; 140–145)     

Overactive bladder inhibition in response to pelvic floor muscle exercises

A recent study by the senior author demonstrated that striated urethral sphincter contraction effected the inhibition of vesical contraction and suppression of the desire to micturate, an action suggested to be mediated through the "voluntary urinary inhibition reflex". We hypothesized that the effect of pelvic floor muscle (PFM) exercises on the overactive bladder was mediated through this reflex action. The current communication investigates this hypothesis. A total of 28 patients (mean age 44.8+/-10.2 years, 18 men, 10 women) with overactive bladder and 17 healthy volunteers (mean age 42.6+/-9.8 years, 12 men, 5 women) were enrolled in the study. The vesical and posterior urethral pressures were determined before and after vesical filling reached the volume at which urge in control subjects, and involuntary voiding in the patients, occurred. Intra-abdominal pressure was recorded to obtain detrusor pressure readings. The bladder was refilled to the above volume and the subject asked to hold PFM contractions for 10 s during which the vesical and posterior urethral pressures were recorded. In healthy volunteers, the mean detrusor and posterior urethral pressures at urge to void were 30.6+/-4.8 SD and 18.7+/-3.3 cm H(2)O, respectively. On PFM contraction, the detrusor pressure declined to 11.6+/-1.4 cm H(2)O (P<0.01) and urethral pressure increased to 139.8+/-17.4 cm H(2)O (P<0.001). In patients, the mean detrusor and posterior urethral pressure readings when the bladder was filled to the volume which induced involuntary incontinence, were 28.2+/-4.2 and 17.3+/-3.4 cm H(2)O, respectively; on PFM contractions, the detrusor pressure decreased to 10.6+/-2.1 cm H(2)O (P<0.01), while urethral pressure increased to 86.6+/-7.9 cm H(2)O (P<0.001) and voiding did not occur. In conclusion, PFM contractions led to a decline of detrusor and increase of urethral pressures and suppressed the micturition reflex. These contractions appear to induce their effect by preventing internal sphincter relaxation produced by the micturition reflex. Failure of the internal sphincter to relax seems to cause reflex detrusor relaxation, an action presumably mediated through the "voluntary urinary inhibition reflex". The results of the current study encourage the treatment of overactive bladder with PFM contractions.     

Videomanometry of the pelvic organs: A comparison of the normal lower urinary and gastrointestinal tracts

BACKGROUND: Both the lower urinary tract (LUT) and the caudal part of the lower gastrointestinal tract (LGIT) are innervated by the sacral spinal cord. We aimed to compare the normal physiology of the LUT and LGIT using the same videomanometry method. METHODS: We recruited fifteen healthy volunteers (eight men and seven women; mean age, 60 years). The videomanometric measures included fluoroscopic images, subtracted bladder/rectal pressures, urethral/anal sphincter pressures, sphincter electromyography, and urinary/fecal flow. RESULTS: During the resting phase, the urethral/anal sphincter pressures showed almost the same values (mean, 70 cmH2O and 68 cmH2O, respectively). During the storage phase, the volumes at first sensation and maximum capacity for the LGIT (129 mL and 320 mL) were slightly smaller than those for the LUT (170 mL and 405 mL). Compliance of the LGIT (65 mL/cmH2O) was almost as high as that of the LUT (99 mL/cmH2O). However, the LGIT showed spontaneous phasic rectal contractions (SPRC) that were never seen in the bladder. None of the subjects experienced leakage during bladder/rectal filling. During the evacuation phase, rectal contraction on defecation (14 cmH2O) was present, but was weaker than bladder contraction on micturition (42 cmH2O; P < 0.01). Abdominal strain on defecation (70 cmH2O) was greater than that on micturition (25 cmH2O; P < 0.01). Sphincter pressure increase on defecation (13 cmH2O) was greater than that on micturition (-52 cmH2O). An illustrative case of SPRC that were seen during urodynamic recording was shown. CONCLUSION: SPRC and abdominal strain are features of the LGIT, whereas micturition bladder contraction is a feature of the LUT. These features can aid in understanding the possible rectal 'artifacts' of videourodynamics and neurogenic pelvic organ dysfunction.     

Bladder inhibition or voiding induced by pudendal nerve stimulation in chronic spinal cord injured cats

AIMS: To investigate pudendal-to-bladder spinal reflexes in chronic spinal cord injured (SCI) cats induced by electrical stimulation of the pudendal nerve. METHODS: Bladder inhibition or voiding induced by pudendal nerve stimulation at different frequencies (3 or 20 Hz) was studied in three female, chronic SCI cats under alpha-chloralose anesthesia. RESULTS: Voiding induced by a slow infusion (2-4 ml/min) of saline into the bladder was very inefficient (voiding efficiency=7.3%+/-0.9%). Pudendal nerve stimulation at 3 Hz applied during the slow infusion inhibited reflex bladder activity, and significantly increased bladder capacity to 147.2+/-6.1% of its control capacity. When the 3-Hz stimulation was terminated, voiding rapidly occurred and the voiding efficiency was increased to 25.4+/-6.1%, but residual bladder volume was not reduced. Pudendal nerve stimulation at 20 Hz induced large bladder contractions, but failed to induce voiding during the stimulation due to the direct activation of the motor pathway to the external urethral sphincter. However, intermittent pudendal nerve stimulation at 20 Hz induced post-stimulus voiding with 78.3+/-12.1% voiding efficiency. The voiding pressures (39.3+/-6.2 cmH2O) induced by the intermittent pudendal nerve stimulation were higher than the voiding pressures (23.1+/-1.7 cmH2O) induced by bladder distension. The flow rate during post-stimulus voiding induced by the intermittent pudendal nerve stimulation was significantly higher (0.93+/-0.04 ml/sec) than during voiding induced by bladder distension (0.23+/-0.07 ml/sec). CONCLUSIONS: This study indicates that a neural prosthetic device based on pudendal nerve stimulation might be developed to restore micturition function for people with SCI.     

Urodynamics in spinal shock patients

We investigated 17 spinal shock patients with traumatic complete cord lesions with cystometry, urethral pressure profile, anal and rectal pressure recordings, and electromyography of the pelvic floor sphincters. Bladder filling was accompanied by an elevation of resistance in the bladder neck area, with a concomitant increase of pressure in the external sphincter zone but without a simultaneous increase of the electromyographic activity. These results indicate an increased sympathetic activity in the smooth muscle component of the entire urethra. In the majority of patients the continuous withdrawal pressure profile had higher values in the membranous urethra than the interrupted withdrawal pressure profile had higher values in the membranous urethra than the interrupted withdrawal pressure profile, revealing the importance of sensory afferents from the urethral mucosal receptors in producing artifactual reflex activity in the pelvic floor muscles. In the majority of interrupted withdrawal urethral pressure profiles higher pressures were recorded in the juxtabulbous region than in the mid part of the membranous urethra. A somewhat decreased electromyographic activity was found in the anal and urethral sphincters at rest. It did not often relate to the amount of resistance recorded in either sphincter. High urethral sphincter pressures and somatic activity of the conus medullaris reflexes show that external urethral and anal sphincters escape spinal shock, the primary characteristic of which is areflexia.     

Urodynamic findings in patients with a urethral Kock pouch after radical cystectomy]

Urodynamic evaluation was performed in 11 male patients, who underwent radical cystectomy with pelvic lymph node dissection for bladder cancer followed by bladder replacement with a urethral Kock pouch, 3 to 21 months after the operation. Frequency of micturition were 4.9 +/- 1.5 times (mean +/- S.D.) during the day-time and 1.5 +/- 1.2 times during the night-time. Tidal volume of micturition ranged from 300 to 550 ml and residual volume from 10 to 30 ml. Urinary continence was completely preserved in all patients (100%) during the day-time and 8 (72.7%) during the night-time. On pouchmetry, maximum capacity of the pouch was 429.2 +/- 82.4 ml, and intra-pouch pressure was 16.2 +/- 5.4 cmH2O at the capacity of 200 ml and 38.7 +/- 11.5 cmH2O at the maximum capacity. Maximum intra-pouch pressure on voiding was 80.0 +/- 19.4 cmH2O. Uroflowmetry demonstrated intermittent voiding curves in all the patients, with maximum flow rate of 15.2 +/- 6.5 ml/sec, voided volume of 405.9 +/- 80.7 ml and residual rate of 4.5 +/- 2.6%. Maximum intra-urethral pressure at the external urethral sphincter was 28.0 +/- 11.3 cmH2O when the pouch was empty and increased in response to pouch filling up to 64.7 +/- 27.0 cmH2O. Maximum urethral closing pressure and total profile length on the urethral pressure profile were 30.2 +/- 12.4 cmH2O and 20.9 +/- 9.0 mm, respectively, with the pouch empty, and 23.2 +/- 14.5 cmH2O and 20.0 +/- 7.6 mm, respectively, with the pouch full.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anal hypertonia in fissures: cause or effect?

High sphincter pressures recorded in patients with fissure-in-ano have been attributed to sphincter spasm induced by wide recording assemblies. To investigate this hypothesis, anal sphincter pressure was measured using a series of perfused probes of 0.4-2 cm diameter in six men with chronic anal fissure in whom digital examination was easily tolerated. The results were compared with those from 14 normal men. The resting pressure within the anal canal exceeded the normal range in all six patients irrespective of probe size. With the smallest (0.4 cm) probe, the resting pressure was 114 +/- 17.1 cmH2O (mean +/- s.d.) in patients with fissure and 73.1 +/- 27.0 cmH2O (mean +/- s.d.) in control subjects (P less than 0.001) even 10 min after introduction of the device. The minimum residual pressure attained during inflation of a rectal balloon with 100 ml of air was higher in patients with anal fissure than controls, reaching statistical significance with the 1.0 cm probe (80.8 +/- 17.7 cmH2O versus 36.9 +/- 19.0 cmH2O, P less than 0.001). Maximum pressures recorded during a voluntary contraction of the sphincter were no higher than in control subjects. The results suggest that high resting pressures are recorded in patients with chronic anal fissures even when small probes are employed and are unlikely to be due to spasm, but probably represent a true increase in basal sphincter tone. It is proposed that elevated sphincter pressures may cause ischaemia of the anal lining and this may be responsible for the pain of anal fissures and their failure to heal.     

Can simultaneous perineal sonography and urethrocystometry help explain urethral pressure variations?

Objective: To correlate urodynamic with perineal sonographic findings in pressure variations. Patients and methods: In 15 women presenting with urethral pressure variations a urodynamic evaluation with water filling cystometry, urethral pressure at rest and during coughing and uroflowmetry were performed. During water filling cystometry, there were simultaneous perineal video-sonography and urethrocystometry. Video ultrasound images and urodynamic curves were simultaneously monitored on a computer screen. Results: Simultaneous ultrasound and urodynamic evaluation in the 15 patients revealed movements in two areas leading to urethral pressure variations: activity of the pelvic floor muscles and of the urethral sphincter muscles. For the pelvic floor, we found either slow or fast contractions with, respectively, slow (15–30 cm H₂O for 3–10 sec) or fast (30–130 cm H₂O for 1–3 sec) urethral pressure changes. Urethral sphincter contractions were always fast, resulting in fast pressure changes of 30–170 cm H₂O for 1–3 sec. Conclusion: Evaluation of simultaneous perineal sonography and urethrocystometry shows the association of urethral pressure variations and muscle activity. Urethral pressure variations are caused by the activity of urethral sphincter or pelvic floor muscles. With ultrasound the activity of the urethral sphincter muscle can directly be seen whereas pelvic floor muscle activity is indirectly visible. Pelvic floor muscle contractions are either fast or slow, whereas the urethral sphincter muscle contractions are always fast contractions.     

Effects of a selective metabotropic glutamate receptor agonist on the micturition reflex pathway in urethane-anesthetized rats

AIMS: To determine a possible role of metabotropic glutamate receptors in the spinobulbospinal micturition reflex pathway in the rat. MATERIALS AND METHODS: A selective metabotropic glutamate receptor agonist, trans-(+/-)-1-amino1,3-cyclopentanedicarboxylic acid (trans-ACPD) was administered to the lumbosacral spinal cord via an intrathecal catheter in urethane anesthetized rats. Amplitude of reflex bladder contractions evoked by bladder distension under isovolumetric condition as well as amplitude of bladder contractions elicited by electrical stimulation of the pontine micturition center (PMC) were examined before and after administration of trans-ACPD. The effect of trans-ACPD on the urethral activity during isovolumetric bladder contractions was also examined by monitoring urethral perfusion pressure and electromyography of the external urethral sphincter (EUS-EMG). RESULTS: Trans-ACPD (3-10 microg) completely inhibited reflex bladder contractions evoked by bladder distension and the duration of inhibition was dose dependent (3 microg: 11.4 +/- 2.8 min, 5 microg: 13.2 +/- 1.3 min, 10 microg: 36.2 +/- 2.4 min). The mean amplitude of bladder contractions evoked by electrical stimulation of the PMC was reduced to 12.6 +/- 2.3% of control by 10 microg of trans-ACPD. In addition, bursting activity of EUS-EMG and corresponding high frequency oscillations of urethral pressure during isovolumetric bladder contractions were completely abolished by 10 microg of trans-ACPD. CONCLUSIONS: These results indicate that intrathecal administration of a selective metabotropic glutamate receptor agonist to the lumbosacral spinal cord has an inhibitory effect on the spinobulbospinal micturition reflex pathway in urethane-anesthetized rats. This pharmacological action is attributed at least to the inhibitory effect on the descending pathway from the PMC to the lumbosacral spinal cord.     

Detrusor myotomy: a 5-year review in unstable and non-compliant bladders

OBJECTIVE: To identify urodynamic factors that might determine the clinical outcome of detrusor myotomy in incontinent children. PATIENTS AND METHODS: Six girls and three boys (aged 5-14 years) underwent detrusor myotomy for severe urinary incontinence. Seven children had spina bifida, one had traumatic paraplegia and one had low bladder compliance. The patients were followed for a minimum of 5 years. RESULTS: Urodynamic studies before surgery showed that three patients had normal compliance with grossly unstable detrusor contractions, and six had low bladder compliance with few phasic detrusor contractions. Detrusor leak-point pressures were > 40 cmH2O in five patients and < 40 cmH2O in four. Only two patients, both with grossly unstable detrusor contractions and leak-point pressures of > 40 cmH2O, had a successful 5-year outcome. The other seven patients remained incontinent; six underwent further surgery and one died from unrelated causes. CONCLUSION: Detrusor myotomy appears to have the best outcome in those patients with marked phasic unstable detrusor contractions with a competent urethral sphincter. In this group it may have distinct advantages over more commonly used procedures.     

The relationship between external anal and external urethral sphincter activity in continent women

The relationship between the external anal sphincter and the periurethral sphincter muscles is an unresolved issue. Recordings of the external anal sphincter (EAS) are commonly used to indicate the responses of the urethral sphincter during urodynamic evaluations and in biofeedback procedures for the treatment of urinary incontinence. This study examined the validity of using anal sphincter training to teach control of the external urethral sphincter. Subjects were 5 continent women, aged 37–51 years, who reported being free of all urologic symptoms. Using visual biofeedback of anal sphincter pressure, subjects were trained to voluntarily contract the sphincter to four amplitudes: 5, 10, 15, and 20 mmHg (6.8, 13.6, 20.4, and 27.2 cmH₂O). Then they were guided through a series of controlled anal sphincter contractions, while the response of the urethral sphincter was measured using surface electrodes embedded in a Foley catheter. At each of four bladder volumes, subjects performed 16 contractions (four contractions at each of the four amplitudes). The order of contractions was counterbalanced, using a Latin square design. The results show a strong, statistically significant, monotonic relationship between the magnitude of anal sphincter contraction (pressure) and the level of urethral sphincter electromyographic (EMG) activity. The results support the use of the external anal sphincter as an indicator of urethral sphincter activity for the purpose of conducting biofeedback in the treatment of urinary incontinence.     

A Balloon-Tipped Catheter for Measuring Urethral Pressures

Background:

Better methods are needed for recording urethral function for complex urologic problems involving the bladder, urethra, and pelvic floor.

Objective:

To evaluate a balloon catheter for recording urethral pressure and function using bench-top testing and evaluation in an animal model.

Methods:

Balloon pressure–recording methods included slightly inflating the balloon with water and placing the pressure transducer on the distal end of the catheter. For bench-top testing, manual procedures and a silastic tube with a restriction were used. In 3 anesthetized dogs, pressure recorded from the skeletal urethral sphincter was induced with electrical stimulation of the sphincter. Anal sphincter pressure was also recorded.

Results:

Bench-top testing showed good pressure recordings, including a confined peak at the tube restriction. Animal tests showed urethral pressure records with rapid responses when electrical stimulation was applied. Peak pressure at the urethral skeletal sphincter was 55.7 ± 15 cmH₂O, which was significantly higher than the peak pressure recorded 2 cm distally in the proximal urethra (3.3 ± 2.3 cmH₂O). Peak anal pressures were smaller and unchanged for the 2 stimulations.

Conclusions:

Balloon-pressure recordings showed rapid responses that were adequate for the tests conducted. In the animal model, high-pressure contractions specific to the skeletal urethral sphincter were shown. Balloon-tipped catheters warrant further investigation and may have applications for the evaluation of detrusor-sphincter dyssynergia after spinal cord injury or for stress urinary incontinence.     

The effect of abdominal and pelvic floor muscle activation patterns on urethral pressure

Purpose

Urethral pressure increases during voluntary pelvic floor (PF) muscle contractions in healthy women. As PF and abdominal muscle activity is coordinated, this study aimed to determine whether specific abdominal muscle actions also change urethral pressure.

Methods

Urethral pressures were measured in seven healthy women during lower abdominal in-drawing, abdominal bulging and PF muscle contractions, with the bladder empty and filled to 250 ml. A repeated measures multiple analysis of variance compared vesical, rectal and urethral pressure changes between bladder volumes and the three tasks.

Results

Urethral pressures increased by a similar amount during PF muscle contractions and abdominal in-drawing (p = 0.94) and did not differ between bladder status. During abdominal bulging, urethral pressures decreased by 12.6 (18.2) cmH₂O (full bladder) and 18.1 (11.5) cmH₂O (empty bladder) and were different from the other two manoeuvres (p < 0.001).

Conclusions

This study shows that specific abdominal actions are associated with increased or decreased urethral pressures, consistent with strategies for continence and voiding.     

Lateral division of the puborectalis muscle in the management of severe constipation

Patients with severe constipation often do not 'relax' their pelvic floor during defaecation. Electromyography of the pelvic floor may reveal inappropriate contraction during defaecation straining, and balloon expulsion, a test of rectal evacuation, may be impaired. Fifteen patients with severe idiopathic constipation and three patients with a megarectum underwent lateral division of the puborectalis muscle and upper half of the external sphincter muscle. Twelve patients had a unilateral division and six patients had both sides divided. Surgery caused a marked reduction in the maximum voluntary squeeze pressure in the anal canal from a pre-operative mean of 90 +/- 49 (s.d.) cmH2O to a postoperative mean of 40 +/- 29 cmH2O (P less than 0.0001). Four patients, three with idiopathic constipation and one with megarectum, experienced symptomatic improvement. Three of these patients had a bilateral division. Improvement did not correlate with a change in the puborectalis electromyography or the ability to expel a balloon. Three patients experienced mild mucus or urge incontinence, but no patient was incontinent for solid stool.     

Incontinence after augmentation cystoplasty and internal diversion

The collective published experience with continent urinary diversions, together with our own, indicates that there are certain basic principles with regard to continence, which is dependent on: (1) the pressure generated by the reservoir; (2) the outflow resistance of the outlet; and (3) detubularization, which is crucial to diminish the uninhibited involuntary bowel contractions. Detubularized ileal pouches provide the lowest pressures (less than 20 cm H2O). Although the majority of patients (approximately 85%) who have a low-pressure ileal neobladder are completely continent, a few experience persistent nocturnal incontinence as a result of low resting urethral pressure. Numerous continence methods have been described, each with its own unique set of problems. The most physiologic continence mechanism is the external urethral sphincter in men. It is clear that total continence with this mechanism is not assured. Other factors such as reservoir contractions, overflow incontinence, decreased sphincter tone, and loss of the normal vesicourethral reflex play an important role in nocturnal incontinence. However, understanding these contributing elements will allow us to refine the construction of a continent physiologic bladder substitute.     

同步膀胱膜部尿道测压的临床意义

目的 探讨同步膀胱膜部尿道压力测定的临床意义。方法 采用ANTEC Duet尿动力学仪同步测定412例泌尿系病人和6例健康者充盈和排尿时的膀胱和膜部尿道压力,肌电图用直肠电极测定。结果 （1）健康人充盈期膜部尿道压,男性为40－50cmH2O,女性为20－30cmH2O,充盈期膜部尿道压高于膀胱压,且全充盈期没有明显变化,排尿时膜部尿道压力明显下降低于膀胱压。（2）逼尿肌尿道协同失调的病人,排尿时膜部尿道压升高,其中逼尿肌外括约肌协同失调（EDES）时合并有肌电活动明显增加,逼尿肌膀胱颈协同失调（DBDS）肌电活动正常,排尿期尿道测压膀胱颈处压力呈斜坡样下降。（3）尿道关闭机制下降或不全时充盈期膜部尿道压明显低,且充盈期膜部尿道膀胱压力差为负值。（4）尿道不稳定充盈期膜部尿道压突然下降且幅度≥15cmH2O。（5）正常尿道腹压传递率为20％－35％,而压力性尿失禁（GUI）病人尿道腹压传递率＜20％。结论 同步膀胱膜部尿道压力测定操作简单,在判断尿道关闭机制的正常与否、逼尿肌尿道的协同与否、尿道稳定性及腹压向尿道的传递效率方面有重要价值。     

Minimally-invasive electrical stimulation of the pudendal nerve: a pre-clinical study for neural control of the lower urinary tract

AIMS: Electrical stimulation of afferent pudendal nerve fibers can evoke sustained bladder contractions (SBC) in cats, yet evidence of therapeutic efficacy in human subjects is lacking. This pre-clinical study was undertaken to test the hypothesis that robust bladder contractions can be generated with a minimally-invasive needle electrode. MATERIALS AND METHODS: In seven adult cats, triggered electromyographic (EMG) signals from the external anal sphincter (EAS) were used to minimize the needle-to-nerve distance; while reflex bladder contractions were recorded as 20-sec trains of current pulses of varying amplitude (threshold to 10 mA) and frequency (1-100 Hz) were applied to the nerve. This stimulation paradigm was repeated at successively greater needle-to-nerve distances (0.5 cm intervals) and also at different electrode positions along the nerve. RESULTS: Electrophysiological access to the pudendal nerve was consistently achieved, as indicated by the average threshold for EAS activation (0.31+/-0.19 mA). Using different combinations of stimulus amplitude and frequency, robust SBCs were evoked in every experiment. More rostral electrode positions exhibited stimulation amplitudes and corresponding maximum bladder pressures (0.68+/-0.36 mA and 25.3+/-3.5 cmH2O, respectively) that were comparable to those of more invasive stimulation methods. CONCLUSIONS: The needle electrode provides a minimally-invasive approach that will enable the study of reflexes mediated by pudendal afferents in humans, and allow pre-operative testing before implanting a permanent device.     

Correlation between laboratory findings and clinical outcome after restorative proctocolectomy: serial studies in 20 patients with end-to-end pouch-anal anastomosis

Clinical function and anorectal physiological function were assessed and correlated in 20 patients with ulcerative colitis before restorative proctocolectomy and 3, 7, and 12 months after operation. The entire anal sphincter was preserved by means of a stapled pouch-anal anastomosis. Before operation, the median resting anal pressure was 79 cmH2O (interquartile range 70-89 cmH2O), the rectoanal inhibitory reflex was present in all patients and anorectal 'sampling' was noted in 16 of 20 patients. Three months after operation, resting anal pressure was 68 cmH2O (range 50-87 cmH2O) (P less than 0.001), the reflex was present in only three patients (P less than 0.001) and sampling was observed in one patient. After 7 months, resting anal pressure was 76 cmH2O (range 64-89 cmH2O), the reflex was present in 11 patients and sampling was observed in nine patients. At 12 months, resting anal pressure was 84 cmH2O (range 66-94 cmH2O), the reflex was present in 19 patients and sampling was observed in 17 patients. The compliance and capacity of the reservoir increased significantly. Ability to discriminate flatus from faeces was associated with return of the rectoanal reflex and sampling.     

The "opening time" and "pelvic floor electromyographic lag time": two novel tools in the assessment of the anorectal evacuation time.

Rectal evacuation necessitates rectal contraction and pelvic floor muscles relaxation; it is not known which action precedes the other. We investigated the hypothesis that pelvic floor muscles relaxation precedes rectal contraction so that rectal contents find the anal canal already opened. Electromyographic activity of the external anal sphincter as well as anal and rectal pressures were recorded during rectal balloon distension and evacuation. Pelvic floor muscles electromyographic lag time (time from start of pelvic floor muscles relaxation to start of evacuation) and opening time (time from start of rectal contraction to start of evacuation) were measured. Rectal balloon distension in increments of 20 mL up to 100 mL effected progressive increase of both external anal sphincter electromyography and anal pressure. At 120 mL balloon distension up to 180 mL, external anal sphincter electromyography and anal pressure exhibited gradual decrease whereas rectal pressure showed no changes. At 200 to 220 mL rectal balloon distension, rectal pressure increased and anal pressure decreased, while external anal sphincter showed no electromyographic activity; rectal balloon was expelled. The opening time recorded a mean of 1.8 +/- 0.7 s and pelvic floor muscles electromyographic lag time of 2.2 +/- 0.9; the two recordings showed no significant difference (p > .05). These, two diagnostic tools in anorectal investigations are presented: the opening time and pelvic floor muscles electromyographic lag time. Pelvic floor muscles relaxation preceded rectal contraction. As there is no significant difference between opening time and pelvic floor muscles electromyographic lag time, it appears easier to apply the latter as it is simple, objective, and noninvasive.